U.S. patent application number 15/107658 was filed with the patent office on 2016-11-03 for brushless motor, wiper apparatus, motor apparatus, and control method for motor apparatus.
The applicant listed for this patent is MITSUBA CORPORATION. Invention is credited to Tomohiko Annaka, Toru Furusawa, Tomofumi Kobayashi, Naoki Kojima, Hiroto Tanaka.
Application Number | 20160322921 15/107658 |
Document ID | / |
Family ID | 53478644 |
Filed Date | 2016-11-03 |
United States Patent
Application |
20160322921 |
Kind Code |
A1 |
Annaka; Tomohiko ; et
al. |
November 3, 2016 |
BRUSHLESS MOTOR, WIPER APPARATUS, MOTOR APPARATUS, AND CONTROL
METHOD FOR MOTOR APPARATUS
Abstract
A brushless motor (18) which supplies currents to coils (U1, U2,
V1, V2, W1, and W2) and rotates a rotor (27), the brushless motor
comprising a control apparatus (37) which switches and selectively
executes: first energization control to start energization to the
coils (U1, U2, V1, V2, W1, and W2) at first timing, and to continue
the energization for a first period to control the rotation number
of the rotor (27); and second energization control to start
energization to the coils (U1, U2, V1, V2, W1, and W2) at second
timing advanced by an electric angle with respect to the first
timing, and to continue the energization for a second period longer
than the first period to control the rotation number of the rotor
(27).
Inventors: |
Annaka; Tomohiko; (Gunma,
JP) ; Tanaka; Hiroto; (Gunma, JP) ; Kojima;
Naoki; (Gunma, JP) ; Furusawa; Toru; (Gunma,
JP) ; Kobayashi; Tomofumi; (Gunma, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBA CORPORATION |
Kiryu-shi |
|
JP |
|
|
Family ID: |
53478644 |
Appl. No.: |
15/107658 |
Filed: |
December 22, 2014 |
PCT Filed: |
December 22, 2014 |
PCT NO: |
PCT/JP2014/083821 |
371 Date: |
June 23, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60S 1/166 20130101;
H02P 27/08 20130101; B60S 1/08 20130101; H02P 6/10 20130101 |
International
Class: |
H02P 6/10 20060101
H02P006/10; B60S 1/08 20060101 B60S001/08; B60S 1/16 20060101
B60S001/16; H02P 27/08 20060101 H02P027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2013 |
JP |
2013-267084 |
Dec 25, 2013 |
JP |
2013-267085 |
Claims
1-13. (canceled)
14. A brushless motor which supplies a current to a coil and
rotates a rotor, the brushless motor comprising a control unit
which switches and selectively executes: first energization control
to start energization to the coil at first timing, and to continue
the energization for a first period to control the rotation number
of the rotor; and second energization control to start energization
to the coil at second timing advanced by an electric angle with
respect to the first timing, and to continue the energization for a
second period longer than the first period to control the rotation
number of the rotor.
15. The brushless motor according to claim 14, wherein the second
timing is advanced by an electric angle 30.degree. with respect to
the first timing.
16. The brushless motor according to claim 15, wherein the first
period is an electric angle 120.degree., and the second period is
equal to or more than an electric angle 135.degree. and equal to or
less than an electric angle 165.degree..
17. The brushless motor according to claim 14, further comprising a
stator disposed around the rotor, wherein the rotor has: a rotor
shaft having a rotor core attached to an outer peripheral surface
thereof; and four permanent magnets disposed on the outer
peripheral surface of the rotor core along a circumferential
direction of the rotor shaft, wherein the stator has six teeth
disposed at intervals in the circumferential direction of the rotor
shaft, the coil being wound around the teeth.
18. A wiper apparatus, comprising: the brushless motor according to
claim 14; and a wiper arm which receives power from the rotor of
the brushless motor, and which is moved so as to wipe off a window
glass of a vehicle.
19. The wiper apparatus according to claim 18, comprising: a mode
switching unit which switches and selects one of a low-speed mode
to move the wiper arm at a speed determined in advance; and a
high-speed mode to move the wiper arm at a speed faster than the
low-speed mode, wherein the control unit executes the second
energization control when the high-speed mode is selected.
20. A motor apparatus which supplies currents to a plurality of
coils and rotates a rotor, the motor apparatus comprising: a
plurality of switching elements which separately turn on or off
current supply paths connected to the coils; a plurality of sensors
which are different in phase from each other, provided in a
rotation direction of the rotor, and detects a phase of the rotor
in the rotation direction to generate output signals; a signal
correcting unit which uses an output signal of any one sensor among
the sensors as a reference signal, and corrects the output signal
of the other sensor; and an element control unit which separately
turns on or off the switching elements on the basis of the
reference signal and the corrected output signal.
21. The motor apparatus according to claim 20, wherein the element
control unit switches and selectively executes: first energization
control to start energization to the coils at first timing to
control an output of the rotor; and second energization control to
start energization to the coils at second timing advanced by a
predetermined electric angle with respect to the first timing to
control the output of the rotor.
22. The motor apparatus according to claim 20, wherein the element
control unit executes third energization control to continue
energization to the coil for the time longer than the time in which
the energization to the coil is continued in the second
energization control.
23. The motor apparatus according to claim 20, further comprises a
control board to which the switching elements, the sensors, the
signal correcting unit, and the element control unit are
attached.
24. The motor apparatus according to claim 20, further comprising a
stator disposed around the rotor, wherein the rotor has: a rotor
shaft having a rotor core attached to an outer peripheral surface
thereof; and four permanent magnets disposed on the outer
peripheral surface of the rotor core along a circumferential
direction of the rotor shaft, wherein the stator has six teeth
disposed at intervals in the circumferential direction of the rotor
shaft, the coil being wound around the teeth.
25. The motor apparatus according to claim 20, further comprising a
power transmitting mechanism that transmits torque of the rotor to
a wiper arm which wipes off a window glass of a vehicle.
26. A control method for the motor apparatus according to claim 20,
the motor apparatus controlling an output of a rotor, the control
method comprising: a first step of controlling the output of the
rotor by using an output signal of any one sensor among the sensors
as a reference signal, and correcting the output signal of the
other sensor; and a second step of separately turning on or off the
switching elements on the basis of the reference signal and the
corrected output signal.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] Applicant hereby claims foreign priority benefits under
U.S.C. .sctn.119 from International Patent Application Serial No.
PCT/JP2014/083821 filed on Dec. 22, 2014; Japanese Patent
Application No. 2013-267084 filed on Dec. 25, 2013; and Japanese
Patent Application No. 2013-267085 filed Dec. 25, 2013, the
contents of all of which are incorporated by reference herein.
TECHNICAL FIELD
[0002] The present invention relates to a brushless motor and a
wiper apparatus, each of which has a stator and a rotor, and can
control the rotation number of the rotor.
[0003] The present invention relates to a motor apparatus having a
sensor for sensing a phase in rotation direction of a rotor, and a
control method for the motor apparatus.
BACKGROUND ART
[0004] Examples of conventional electric motors are described in
Japanese Patent Application Laid-Open Publication No. 2007-202391;
Japanese Patent Application Laid-Open Publication No. 2007-143278;
and Japanese Patent Application Laid-Open Publication No.
2010-93977. The electric motor described in each of Japanese Patent
Application Laid-Open Publication No. 2007-202391 and Japanese
Patent Application Laid-Open Publication No. 2007-143278 is an
electric motor with brush, provided with: a magnet (stator) serving
as a field fixed to a case; and a rotor serving as an armature
rotatably provided in the case. Furthermore, the electric rotor is
provided with: a core around which coils is wound; and a commutator
connected to the coil. In addition, the electric rotor is further
provided with: a common brush which contacts the commutator; a
low-speed-driving brush; and a high-speed-driving brush.
[0005] The brushes are disposed in the phases mutually different in
the rotation direction of the electric rotor, and switching
elements are provided at the respective paths which supply electric
power to the brushes. When the switching elements are turned on or
off, the brush to supply a current is switched, and the rotation
number of the electric rotor is controlled to a low speed or a high
speed.
[0006] The motor described in Japanese Patent Application Laid-Open
Publication No. 2010-93977 is not provided with a brush, but is
provided with a stator (stationary part), which is serving as an
armature in a case, and a rotor serving as a field rotatably
provided in the case. The stator has a stator core and a coil wound
around the stator core. The coil has three coils to which
excitation currents of three phases, in other words, a U-phase, a
V-phase, and a W-phase are supplied, and the coils are disposed so
that the phases are mutually shifted in the rotation direction of
the rotor.
[0007] Furthermore, it is provided with switching elements
electrically connected to the respective coils. By alternately
switching on/off of the switching elements and controlling duty
ratios, which are the rate of "on", currents are supplied to all
the coils with shifted timing, and the rotation number of the rotor
is controlled.
[0008] On the other hand, one example of a conventional motor
apparatus is described in Japanese Patent Application Laid-Open
Publication No. 2003-47277. The motor apparatus described in
Japanese Patent Application Laid-Open Publication No. 2003-47277 is
provided with a brushless motor, an inverter circuit, a control
circuit, a speed control arithmetic unit, etc. The brushless motor
has: a rotor to which permanent magnets and a sensor magnet are
attached; and a stator provided in the outer peripheral side of the
rotor. The stator ha: a core which is a stack of steel plates or
the like; and three coils corresponding to three phases, in other
words, a U-phase, a V-phase, and a W-phase wound around the
core.
[0009] Furthermore, the inverter circuit is used for
connecting/shutting-off the three coils and an electric power
source, and it is provided with positive-electrode switching
elements and negative-electrode switching elements corresponding to
the U-phase, the V-phase and the W-phase. Furthermore, the control
circuit separately turns on/off the switching elements.
[0010] Furthermore, based on the intensity of the magnetic field
formed by the sensor magnet, three sensors which output signals are
provided to correspond to the U-phase, the V-phase, and the
W-phase. The three sensors are disposed at an interval of a
mechanical angle 120.degree. outside the sensor magnet.
Furthermore, the signals output from the sensors are input to the
speed control arithmetic unit, and the speed control arithmetic
unit controls on/off of the switching elements of the inverter
circuit.
[0011] In the motor apparatus described in Japanese Patent
Application Laid-Open Publication No. 2003-47277, on/off of the
switching elements is controlled, currents are supplied to the
three coils at predetermined timing, and a rotating magnetic field
is formed by the three coils to rotate the rotor. Furthermore, the
speed control arithmetic unit detects the rotation phases of the
rotor on the basis of the signal output from the singe sensor
determined in advance among the three sensors and, on the basis of
the detected rotation phase, controls the on/off timing of the
switching elements.
[0012] Therefore, even if there are errors in the attachment
positions of the other two sensors with respect to the single
sensor determined in advance, it is assumed that electric power can
be distributed to the three coils at ideal energization timing, and
the rotation number of the rotor can be appropriately
controlled.
SUMMARY
[0013] The electric motors as described in Japanese Patent
Application Laid-Open Publication No. 2007-202391; Japanese Patent
Application Laid-Open Publication No. 2007-143278; and Japanese
Patent Application Laid-Open Publication No. 2010-93977 have
problems that, regardless of whether the electric motor is provided
with brushes or not, torque ripples at the rotor are increased
depending on control conditions.
[0014] An object of the present invention is to provide a brushless
motor and a wiper apparatus capable of suppressing the torque
ripples at the rotor.
[0015] In the brushless motor described in the Japanese Patent
Application Laid-Open Publication No. 2003-47277, since it is
difficult to say that the signals of the three sensors are
effectively utilized, it is possible to further improve the
brushless motor and the wiper apparatus.
[0016] It is therefore an object of the present invention to
provide a motor apparatus and a motor control method capable of
effectively utilizing signals of sensors for detecting rotation
phases of a rotor.
[0017] According to one aspect of the present invention, there is
provided a brushless motor which supplies a current to a coil and
rotates a rotor, the brushless motor comprising a control unit
which switches and selectively executes: first energization control
to start energization to the coil at first timing, and to continue
the energization for a first period to control the rotation number
of the rotor; and second energization control to start energization
to the coil at second timing advanced by an electric angle with
respect to the first timing, and to continue the energization for a
second period longer than the first period to control the rotation
number of the rotor.
[0018] In the brushless motor of the present invention, the second
timing is advanced by an electric angle 30.degree. with respect to
the first timing.
[0019] In the brushless motor of the present invention, the first
period is an electric angle 120.degree., and the second period is
equal to or more than an electric angle 135.degree. and equal to or
less than an electric angle 165.degree..
[0020] In the brushless motor of the present invention, the rotor
has: a rotor shaft having a rotor core attached to an outer
peripheral surface thereof; and four permanent magnets disposed on
the outer peripheral surface of the rotor core along a
circumferential direction of the rotor shaft, wherein a stator
having the coil is provided outside the rotor; and the coil is
provided with 6 slots at intervals in the circumferential direction
of the rotor shaft.
[0021] A wiper apparatus of the present invention comprises: the
above described brushless motor; and a wiper arm which receives
power from the rotor of the brushless motor, and which is moved so
as to wipe off a window glass of a vehicle.
[0022] The wiper apparatus of the present invention comprises: a
mode switching unit which switches and selects one of a low-speed
mode to move the wiper arm at a speed determined in advance; and a
high-speed mode to move the wiper arm at a speed faster than the
low-speed mode, wherein the control unit executes the second
energization control when the high-speed mode is selected.
[0023] A motor apparatus of the present invention is a motor
apparatus which supplies currents to a plurality of coils and
rotates a rotor, the motor apparatus comprising: a plurality of
switching elements which separately turn on or off current supply
paths connected to the coils; a plurality of sensors which are
different in phase from each other, provided in a rotation
direction of the rotor, and detects a phase of the rotor in the
rotation direction to generate output signals; a signal correcting
unit which uses an output signal of any one sensor among the
sensors as a reference signal, and corrects the output signal of
the other sensor; and an element control unit which separately
turns on or off the switching elements on the basis of the
reference signal and the corrected output signal.
[0024] In the motor apparatus according to the present invention,
the element control unit switches and selectively executes: first
energization control to start energization to the coils at first
timing to control an output of the rotor; and second energization
control to start energization to the coils at second timing
advanced by a predetermined electric angle with respect to the
first timing to control the output of the rotor.
[0025] In the motor apparatus according to the present invention,
the element control unit executes third energization control to
continue energization to the coil for the time longer than the time
in which the energization to the coil is continued in the second
energization control.
[0026] The motor apparatus according to the present invention is
provided with a control board to which the switching elements, the
sensors, the signal correcting unit, and the element control unit
are attached.
[0027] In the motor apparatus according to the present invention,
the rotor has: a rotor shaft having a rotor core attached to an
outer peripheral surface thereof; and has four permanent magnets
disposed on the outer peripheral surface of the rotor core along a
circumferential direction of the rotor shaft, wherein a stator
having the coils is provided outside the rotor; and the coils are
provided with six slots at intervals in the circumferential
direction of the rotor shaft.
[0028] The motor apparatus according to the present invention is
provided with a power transmitting mechanism that transmits torque
of the rotor to a wiper arm which wipes off a window glass of a
vehicle.
[0029] A control method for the above-described motor apparatus for
controlling an output of a rotor comprises: a first step of
controlling the output of the rotor by using an output signal of
any one sensor among the sensors as a reference signal, and
correcting the output signal of the other sensor; and a second step
of separately turning on or off the switching elements on the basis
of the reference signal and the corrected output signal.
[0030] According to the brushless motor and the wiper apparatus of
the present invention, it is possible to suppress torque ripples of
the rotor.
[0031] According to the motor apparatus and the control method for
the motor apparatus of the present invention, on the basis of the
signal of one of the sensors, the signal of the other sensor is
corrected, and the rotation phases of the rotor are detected by the
sensors. Therefore, it is possible to effectively utilize the
signals of the sensors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a schematic view showing an example in which a
brushless motor of the present invention is applied to a wiper
apparatus of a vehicle;
[0033] FIG. 2 is a schematic plan view showing the brushless motor
of the present invention;
[0034] FIG. 3 is a schematic lateral view showing the brushless
motor of the present invention;
[0035] FIG. 4 is a cross sectional view of the brushless motor of
the present invention;
[0036] FIG. 5 is a conceptual diagram showing an armature of the
brushless motor of the present invention;
[0037] FIG. 6 is a conceptual diagram showing the armature of the
brushless motor of the present invention;
[0038] FIG. 7 is a block diagram showing a control system of the
brushless motor of the present invention;
[0039] FIGS. 8A to 8C are diagrams showing an example of first to
third energization controls, which can be executed by the brushless
motor of the present invention;
[0040] FIG. 9 is a diagram showing characteristics of the brushless
motor of the present invention;
[0041] FIGS. 10A and 10B are diagrams showing the relations between
torque and rotation numbers of the brushless motor of the present
invention;
[0042] FIG. 11 is a diagram showing a torque ripple rate of the
brushless motor of the present invention;
[0043] FIG. 12 is a diagram showing sound pressure characteristics
of the brushless motor of the present invention;
[0044] FIG. 13 is a diagram showing current waveforms of the
brushless motor of the present invention, which is in power-on
state;
[0045] FIG. 14 is a diagram showing sound pressure characteristics
of the brushless motor of the present invention;
[0046] FIG. 15 is a schematic diagram showing an example in which a
motor apparatus of the present invention is used for driving a
wiper apparatus of a vehicle;
[0047] FIG. 16 is a block diagram showing a control system of the
motor apparatus of the present invention;
[0048] FIG. 17 is a time chart showing a drive pattern of first
energization control executed by the motor apparatus of the present
invention;
[0049] FIG. 18 is a time chart showing a drive pattern of first
energization control executed by the motor apparatus of the present
invention;
[0050] FIG. 19 is a time chart showing a drive pattern of second
energization control executed by the motor apparatus of the present
invention;
[0051] FIG. 20 is a time chart showing a drive pattern of third
energization control executed by the motor apparatus of the present
invention;
[0052] FIG. 21 is a time chart showing the waveforms of signals of
sensors of the motor apparatus of the present invention;
[0053] FIG. 22 is a time chart showing the waveforms of the signals
of the sensors of the motor apparatus of the present invention;
[0054] FIG. 23 is a time chart showing the waveforms of the signals
of the sensors of the motor apparatus of the present invention;
[0055] FIG. 24 is a time chart showing the waveforms of the signals
of the sensors of the motor apparatus of the present invention;
and
[0056] FIG. 25 is a flow chart showing a control example, which can
be executed by the motor apparatus of the present invention.
DETAILED DESCRIPTION
[0057] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying
drawings.
First Embodiment
[0058] A vehicle 10 shown in FIG. 1 has a windshield 11.
Furthermore, the vehicle 10 has a first wiper apparatus 12 and a
second wiper apparatus 13, which wipe off the windshield 11. The
first wiper apparatus 12 and the second wiper apparatus 13 are
disposed at positions different from each other in the width
direction of the vehicle 10. Since the first wiper apparatus 12 and
the second wiper apparatus 13 have approximately left-right
symmetric structures, hereinafter, the first wiper apparatus 12
will be described for the sake of convenience. The first wiper
apparatus 12 has: a wiper arm 15 which swings about a pivot shaft
14; and a wiper blade 16 which is attached to the wiper arm 15.
Furthermore, the first wiper apparatus 12 has a motor apparatus 17
serving as a drive apparatus which drives the wiper arm 15. The
motor apparatus 17 is provided with: a brushless motor 18; and a
speed reduction mechanism 19 which transmits the power of the
brushless motor 18 to the pivot shaft 14.
[0059] The brushless motor 18 is formed as shown in FIGS. 2 to 4.
The brushless motor 18 in this embodiment has a motor case 20
formed into a bottomed cylindrical shape, and an armature 21
serving as a stator is provided on an inner periphery of the motor
case 20. The armature 21 has a stator core 22 and armature coils
V1, V2, U1, U2, W1, and W2 wound around the stator core 22. The
stator core 22 is stacked electrically-conductive metal plates,
and, on the inner periphery of the stator core 22, a plurality of,
specifically, six teeth 23 are provided at intervals in the
circumferential direction. The armature coils V1, V2, U1, U2, W1,
and W2 are separately wound around the six teeth 23,
respectively.
[0060] The armature coils V1 and V2 correspond to V-phases, the
armature coils U1 and U2 correspond to U-phases, and the armature
coils W1 and W2 correspond to W-phases. In FIG. 4, clockwise with
respect to the armature 21, the armature coil U1, the armature coil
V1, the armature coil W1, the armature coil U2, the armature coil
V2, and the armature coil W2 are provided in this order. The
armature coils V1 and V2, the armature coils U1 and U2, and the
armature coils W1 and W2 have mutually different phases of
energization period.
[0061] Furthermore, as shown in FIGS. 5 and 6, an end "Ua" of the
armature coil U1 and an end "Ub" of the armature coil W2 are
connected by a terminal 24. Also, an end "Vb" of the armature coil
U2 and an end "Va" of the armature coil V1 are connected by a
terminal 25. Furthermore, an end "Wa" of the armature coil W1 and
an end "Wb" of the armature coil V2 are connected by a terminal 26.
In this manner, the brushless motor 18 employs delta connections as
the connection structure of the six armature coils.
[0062] On the other hand, the brushless motor 18 has a rotor 27,
and the rotor 27 is provided in the inner side of the armature 21.
The brushless motor 18 has an inner-rotor-type structure in which
the rotor 27 is disposed in the inner side of the armature 21,
which is serving as a stator. The rotor 27 has a rotor shaft 28 and
permanent magnets 29N and 29S of four polarities fixed to an outer
periphery of the rotor shaft 28 via a rotor core 30. The polarity
of the two permanent magnets 29N is the N pole, the polarity of the
two permanent magnets 29S is the S pole, and the permanent magnets
29N and the permanent magnets 29S are alternately disposed along
the circumferential direction of the rotor shaft 28. The brushless
motor 18 has 4 as the number of the permanent magnets, has 6 as the
number of the armature coils, and has a four-pole six-slot
structure.
[0063] In this manner, the brushless motor 18 has a SPM (Surface
Permanent Magnet) structure. The SPM structure is a structure in
which the permanent magnets 29N and 29S are fixed to the outer
peripheral surface of the rotor core 30. The rotor core 30 is
formed of an iron-based magnetic material. Furthermore, the rotor
shaft 28 is rotatably supported by a plurality of bearings 49.
[0064] On the other hand, the motor apparatus 17 is provided with a
gear case 31 which houses the speed reduction mechanism 19, and the
gear case 31 and the motor case 20 are fixed by a fastener member
(not shown). Part of the rotor shaft 28 in the length direction is
disposed in the motor case 20, and the remaining part thereof is
disposed in the gear case 31. A worm 32 is formed on the outer
periphery of the part of the rotor shaft 28 that is disposed in the
gear case 31. A worm wheel 33 is provided in the gear case 31. A
gear 33a is formed on the outer periphery of the worm wheel 33, and
the gear 33a and the worm 32 are meshed with each other.
[0065] The pivot shaft 14 is disposed concentrically with the worm
wheel 33, and the pivot shaft 14 is integrally rotated with the
worm wheel 33. The worm 32 and the gear 33a are the speed reduction
mechanism 19 in this embodiment. The speed reduction mechanism 19
is a mechanism which reduces the rotation number (output rotation
number) of the pivot shaft 14 with respect to the rotation number
(input rotation number) of the rotor 27 when the power of the rotor
27 is transmitted to the pivot shaft 14. The rotation number in
this embodiment is the rotation number per unit time and synonymous
with a rotation speed.
[0066] Furthermore, in FIG. 3, in an upper part of the gear case
31, a shaft hole (not shown) is provided. The end of the pivot
shaft 14 that is in the opposite side of the end to which the worm
wheel 33 is fixed is exposed to outside via the shaft hole of the
gear case 31. The wiper arm 15 is coupled to the part of the pivot
shaft 14 that is exposed to outside the gear case 31.
[0067] On the other hand, a sensor magnet 34 is attached to the
part of the rotor shaft 28 that is disposed in the gear case 31.
The sensor magnet 34 is integrally rotated with the rotor shaft 28.
The sensor magnet 34 has a cylindrical shape, and the sensor magnet
34 is magnetized so that N poles and S poles are alternately
juxtaposed along the circumferential direction of the rotor shaft
28.
[0068] An opening is provided at a part of the gear case 31 that is
in the opposite side of the shaft hole thereof. This opening is
formed for inserting the worm wheel 33, the pivot shaft 14, etc.
into the gear case 31. An under cover 35, which closes the opening,
is provided. The under cover 35 has a tray shape, and a control
board 36 is provided in the space surrounded by the under cover 35
and the gear case 31.
[0069] As shown in FIG. 7, a drive apparatus 37, which controls the
brushless motor 18, is provided on the control board 36. The drive
apparatus 37 has an inverter circuit 38, which controls
energization to the six armature coils V1, V2, U1, U2, W1, and W2.
The inverter circuit 38 is connected to the terminals 24, 25, and
26. Furthermore, the under cover 35 is provided with a connector
39; and, when an electric-power-source cable connected to an
external electric power source 40 is connected to the connector 39,
the external electric power source 40 and the inverter circuit 38
are connected to each other. The external electric power source 40
includes a battery, a capacitor, or the like mounted on the vehicle
10.
[0070] Furthermore, the inverter circuit 38 is provided with a
plurality of switching elements 38a, which separately connect or
shut off the external electric power source 40 and the six armature
coils V1, V2, U1, U2, W1, and W2. The switching elements 38a are
composed of, for example, semiconductor elements such as FETs. More
specifically, the switching elements include three
positive-electrode-side switching elements corresponding to the
U-phase, the V-phase, and the W-phase and connected to a positive
electrode of the external electric power source 40 and include
three negative-electrode-side switching elements corresponding to
the U-phase, the V-phase, and the W-phase and connected to the
negative-electrode side of the external electric power source 40.
The number of the switching elements 38a provided is six in
total.
[0071] If the switching element 38a is connected (on), a current is
supplied from the external electric power source 40 to the armature
coil. On the other hand, if the switching element 38a is shut off
(off), the current is not supplied from the external electric power
source 40 to the armature coil. Furthermore, a control circuit
(controller) 50, which switches on and off of the switching
elements 38a, is connected to the inverter circuit 38.
[0072] The control circuit 50 is a publicly-known microcomputer
provided with a CPU, a RAM, a ROM, etc. Furthermore, the drive
apparatus 37 has a PWM-signal generating circuit 51, and the
signals of the PWM-signal generating circuit 51 are input to the
control circuit 50. The control circuit 50 outputs drive signals
which control the three negative-electrode-side switching elements,
and the PWM signals are superimposed on the drive signals.
Therefore, the three negative-electrode-side switching elements are
driven by PWM control and are intermittently turned on in
respective energization periods. The values of the currents
supplied to the six armature coils V1, V2, U1, U2, W1, and W2 are
controlled by controlling the rates at which the three
negative-electrode-side switching elements are separately turned
on, in other words, duty ratios. In other words, the energization
periods in which electric power is supplied to the six armature
coils V1, V2, U1, U2, W1, and W2 can be increased/reduced between
0% and 100% with respect to the entire period in which electric
power can be distributed. Furthermore, the control circuit 50
stores data, programs, etc. for controlling the rotation number of
the rotor 27 of the brushless motor 18.
[0073] Furthermore, the brushless motor 18 in this embodiment can
rotate the rotor 27 forward/backward by carrying out switching
control of on and off of the switching elements 38a and inverting
the directions of energization to the six armature coils V1, V2,
U1, U2, W1, and W2. If the switching elements 38a are turned on,
the external electric power source 40 and the armature coils V1,
V2, U1, U2, W1, and W2 are separately connected; and, if the
switching elements 38a are turned off, the external electric power
source 40 and the armature coils V1, V2, U1, U2, W1, and W2 are
separately shut off.
[0074] The control board 36 is disposed along the planar direction
which is perpendicular to a first axis A1 of the pivot shaft 14.
The first axis A1 serves as a center when the pivot shaft 14
rotates. Three sensors 41, 42, and 43 are attached to the control
board 36. All of the three sensors 41, 42, and 43 are Hall ICs, and
the three sensors 41, 42, and 43 are fixed to the control board 36
without contacting the sensor magnet 34. The three sensors 41, 42,
and 43 are arranged in the direction intersecting with a second
axis B1 of the rotor shaft 28 as shown in FIG. 2 by a planar view
of the control board 36. The second axis B1 serves as a center when
the rotor shaft 28 rotates.
[0075] The disposition range of the three sensors 41, 42, and 43
and the disposition range of the sensor magnet 34 are overlapped
with each other at least partially in the direction along the
second axis B1. Furthermore, if it is assumed that the control
board 36 is horizontally disposed, as shown in FIG. 3, the single
sensor 42 is disposed immediately below the second axis B1. The
three sensors 41, 42, and 43 are disposed at equal intervals in the
direction intersecting with the second axis B1. Furthermore, the
sensor 42 is disposed between the sensor 41 and the sensor 43.
[0076] When the rotor 27 is rotated and moves the magnetic poles of
the sensor magnet 34, the three sensors 41, 42, and 43 carry out
switching operations, and the three sensors 41, 42, and 43
separately generate switching signals (on/off signals),
respectively. On the basis of the switching signals of the three
sensors 41, 42, and 43, the control circuit 50 can detect the
rotation angle and the rotation number of the rotor 27.
Furthermore, a wiper switch 44 is provided in the interior of the
vehicle 10. When a driver manipulates the wiper switch 44 and
selects a low-speed mode or a high-speed mode, manipulation signals
of the wiper switch 44 are input to the control circuit 50.
Furthermore, a vehicle-speed sensor 45, which detects the
travelling speed of the vehicle 10, is provided, and detection
signals of the vehicle-speed sensor 45 are input to the control
circuit 50.
[0077] The control circuit 50 stores, in advance, data, arithmetic
expressions, etc. that control the timing to turn on/off the
switching elements 38a of the inverter circuit 38, the duration
time to turn on the switching elements 38a, etc. on the basis of
various conditions such as the manipulation signals of the wiper
switch 44, the detection signals of the vehicle-speed sensor 45,
and the actuation load of the wiper arm 15. The actuation load of
the wiper arm 15 can be specifically estimated from the signals of
the sensors 41, 42, and 43.
[0078] For example, it is assumed that the high-speed mode is
selected, a target rotation number of the rotor 27 to achieve a
target wiping speed of the wiper arm 15 is obtained, and
energization control is carried out so that the actual rotation
number of the rotor 27 becomes the target rotation number. Herein,
if the actual rotation number of the rotor 27 does not become the
target rotation number, it can be estimated that the action
resistance of the wiper arm 15, in other words, the actuation load
of the wiper arm 15 is increased by snow or the like.
[0079] Also, if the vehicle speed is different, the wind pressure
received by the wiper arm 15 is changed, and, therefore, the
actuation load of the wiper arm 15 is different. Furthermore, if
the inclination angle of the windshield 11 is different, the wind
pressure received by the wiper arm 15 is changed, and, therefore,
the actuation load of the wiper arm 15 is different. The
inclination angle of the windshield 11 is expressed by the
acute-angle-side inclination angle of the windshield 11 with
respect to the horizontal plane. Furthermore, the actuation load of
the wiper arm 15 is varied depending on the length of the wiper
blade 16.
[0080] Note that the gear case 31 is provided with attachment parts
46, for example, three attachment parts, and the attachment parts
46 are provided with shaft holes, respectively. Furthermore, buffer
materials 47 are attached to the shaft holes of the attachment
parts 46, respectively. The buffer materials 47 are annularly
formed synthetic rubbers, and screw members are inserted to holes
47a of the buffer materials 47 to attach the motor apparatus 17 to
a vehicle body 48.
[0081] Next, a control example which can be executed by the
brushless motor 18 in each of the first wiper apparatus 12 and the
second wiper apparatus 13 will be described. The on/off of the
switching elements 38a are controlled by the manipulation signals
of the wiper switch 44 or a condition other than the manipulation
signals of the wiper switch 44. Furthermore, on the basis of the
detection signals of the three sensors 41, 42, and 43, the control
circuit 50 estimates the rotation position of the rotor 27, in
other words, the angle thereof in a rotation direction and carries
out energization control on the basis of the rotation position of
the rotor 27. More specifically, the positive-electrode-side
switching elements of the phases are sequentially turned on
respectively by predetermined angles in electric angles, in other
words, energization angles, and the negative-electrode-side
switching elements of the phases, which are different from the
positive-electrode-side switching elements, are sequentially turned
on by predetermined energization angles, thereby switching the
energization state with respect to the armature coils U1, U2, V1,
V2, W1, and W2 and commutating phase currents.
[0082] When the above described control is repeated, a rotating
magnetic field is formed by the armature 21, and the rotor 27 is
rotated. The brushless motor 18 can subject the rotor 27 to forward
rotations, stop, and backward rotations by subjecting the on and
off of the switching elements 38a to switching control and
inverting the directions of electric distribution to the armature
coils U1, U2, V1, V2, W1, and W2. If the power of the rotor 27 is
transmitted to the pivot shaft 14 via the speed reduction mechanism
19, the wiper arm 15 reciprocates within the range of a
predetermined angle, and the windshield 11 is wiped off by the
wiper blade 16.
[0083] Meanwhile, the brushless motor 18 has a characteristic that
the rotation number of the rotor 27 is increased as the current
value is increased. Furthermore, the brushless motor 18 has a
characteristic that the torque of the rotor 27 is reduced as the
rotation number of the rotor 27 is increased.
[0084] Furthermore, when the brushless motor 18 of this embodiment
is to control the output, in other words, the rotation number and
torque of the rotor 27, the brushless motor 18 can switch and
execute first energization control, weak field control, and second
energization control. The first energization control, the weak
field control, and the second energization control are switched by
various conditions such as the detection signals of the wiper
switch 44, the detection signals of the vehicle-speed sensor 45,
and the load of the wiper arm 15. Particularly, the weak field
control is executed when there is a request to increase the
rotation number of the rotor 27 compared with the first
energization control. On the other hand, the second energization
control is executed when there is a request to increase the torque
of the rotor 27 compared with the first energization control.
[0085] The first energization control, the weak field control, and
the second energization control will be described by FIG. 8. The
angles 0.degree. to 360.degree. shown in FIG. 8 are the
energization angles expressing the energization periods in one
cycle of electric signals. The positive expresses that electric
power is distributed from the positive electrode to the armature
coils V1, V2, U1, U2, W1, and W2, and the negative expresses that
electric power is distributed from the negative electrode to the
armature coils V1, V2, U1, U2, W1, and W2. The energization control
shown in FIG. 8 exemplifies the state of energization to a
predetermined single armature coil.
[0086] FIG. 8A shows the first energization control. The first
energization control uses an energization angle 0.degree. as a
reference, starts energization from the positive electrode to the
predetermined armature coil at the position of an energization
angle 30.degree., maintains the energization in the range of an
energization angle 120.degree., and then terminates the
energization from the positive electrode. Furthermore, the first
energization control has an interval in the range of an
energization angle 60.degree. after the energization from the
positive electrode is terminated, starts energization from the
negative electrode to the predetermined armature coil, maintains
the energization in the range of an energization angle 120.degree.,
and then terminates the energization.
[0087] FIG. 8B shows the weak field control. With respect to the
predetermined armature coil, an energization angle 0.degree. serves
as a reference, energization from the positive electrode is started
at the position of an energization angle 15.degree., the
energization from the positive electrode is maintained in the range
of an energization angle 120.degree., and, then, the energization
from the positive electrode is terminated. Furthermore, with an
interval in the range of an energization angle 60.degree. after the
energization from the positive electrode is terminated,
energization from the negative electrode is started, the
energization from the negative electrode is maintained in the range
of an energization angle 120.degree., and, then, the energization
from the negative electrode is terminated. In this manner, the
position of the energization angle 15.degree. at which the
energization from the positive electrode is started in FIG. 8B is
the timing earlier than the position of the energization angle
30.degree. shown in FIG. 8A. The position of the energization angle
15.degree. has undergone angle advancement by the amount
corresponding to the energization angle 15.degree..
[0088] The second energization control will be described on the
basis of FIG. 8C. With respect to the predetermined armature coil,
an energization angle 0.degree. serves as a reference, energization
from the positive electrode is started at the position of an
energization angle 15.degree., the energization from the positive
electrode is maintained in the range of an energization angle
120.degree.+a, and, then, the energization from the positive
electrode is terminated at the position of an energization angle
165.degree.. Furthermore, after the energization from the positive
electrode is terminated, energization from the negative electrode
is started at an energization angle 195.degree., the energization
from the negative electrode is maintained in the range of an
energization angle 120.degree.+a, and, then, the energization from
the negative electrode is terminated. In this manner, the
energization timing in the second energization control is earlier
than the energization starting timing of the first energization
control by the range of the energization angle 15.degree., and the
range of the energization angle 120.degree.+a, in which the
energization is continued in the second energization control, is
wider than the range of the energization angle 120.degree. in which
the energization is continued in the first energization control.
Herein, the range of the energization angle 120.degree. is a first
period of the present invention, and the range of the energization
angle 120.degree.+a is a second period of the present
invention.
[0089] The first energization control is executed, for example,
when the low-speed mode is selected. The first energization control
causes the actual rotation number of the rotor 27 to be closer to
the required target rotation number by controlling the duty ration
without carrying out the weak field control. Furthermore, with the
first energization control carried out, the timing to start
energization to the armature coils U1, U2, V1, V2, W1, and W2 is at
the position of a fixed value determined in advance, in other
words, the energization angle 30.degree..
[0090] The weak field control or the second energization control is
executed, for example, when the high-speed mode is selected. The
weak field control is executed without changing the current values
supplied to the armature coils U1, U2, V1, V2, W1, and W2. The weak
field control is the control in which the magnetic field formed by
the armature 21 is weakened as much as possible by supplying
currents to the armature coils U1, U2, V1, V2, W1, and W2. When
this weak field control is carried out, the back electromotive
force generated at the armature coils U1, U2, V1, V2, W1, and W2 is
reduced, and the rotation number of the rotor 27 is increased. Note
that the second energization control is to cause the energization
period to be longer than that of the first energization control and
the second energization control in addition to the weak field
control.
[0091] FIG. 9 is a diagram showing characteristics of the brushless
motor 18. In FIG. 9, the rotation number of the brushless motor 18
is shown by a vertical axis, and the torque of the brushless motor
18 is shown by a horizontal axis. Furthermore, FIG. 9 shows an
example of the characteristics for the low-speed mode and an
example of high-speed mode characteristics.
[0092] In the brushless motor 18 of this embodiment, for example, a
single characteristic is present at the position shown by a solid
line so that the rotation number and torque corresponding to the
low-speed mode characteristic of FIG. 9 can be obtained when the
rating thereof is set. Therefore, if the low-speed mode is
selected, the required rotation number and torque can be obtained
in the range equal to and blow the single characteristic by
executing the first energization control.
[0093] The single characteristic is the target output of the case
in which the actual vehicle speed of the vehicle 10 is equal to or
less than a reference vehicle speed, in other words, is the
characteristic that satisfies the low-speed mode. An apparent
characteristic is the target output of the case in which the actual
vehicle speed of the vehicle 10 exceeds the reference vehicle
speed, in other words, is the characteristic that satisfies the
high-speed mode. The target output can be expressed by the rotation
number and torque of the rotor 27. The conditions that determine
the target output include various conditions such as the detection
signals of the wiper switch 44, the detection signals of the
vehicle-speed sensor 45, and the load of the wiper arm 15.
[0094] On the other hand, for example, when the high-speed mode is
selected and the torque and rotation number required to the rotor
27 exceed the single characteristic, the rotation number and torque
exceeding the single characteristic can be obtained by executing
the weak field control or the second energization control by the
control circuit 50. As a result, the characteristic of the
brushless motor 18 is equivalent to the presence at the positions
shown by a dashed-dotted line in FIG. 9 in terms of appearance.
[0095] Therefore, the brushless motor 18 can be subjected to
determination of the rating thereof while using the low-speed mode
as a reference in terms of design, and the size of the brushless
motor 18 can be reduced as much as possible. The fact that the
rotation number of the brushless motor 18 can be increased and the
torque can be increased without changing the current value means
that a torque constant is relatively increased. In other words, the
brushless motor 18 of this embodiment can generate high torque as
much as possible with smaller electric power consumption, and motor
efficiency is improved.
[0096] The characteristics of the brushless motor 18 of the case in
which the weak field control or the second energization control is
carried out will be described on the basis of the characteristic
diagrams of FIGS. 10A and 10B. In the characteristic diagrams of
FIG. 10, torque is shown by horizontal axes, and rotation numbers
are shown by vertical axes. The characteristic diagram of FIG. 10A
shows the characteristics of the brushless motor 18 in the case in
which the second energization control is executed. A solid line
represents the characteristic of an advance angle 30.degree., a
broken line represents the characteristic of an advance angle
45.degree., and a dashed-dotted line represents the characteristic
of an advance angle 60.degree.. The above described advance angle
30.degree., advance angle 45.degree., and advance angle 60.degree.
mean that the energization to the armature coil is started at the
timing earlier by the advance angle 30.degree., the advance angle
45.degree., and the advance angle 60.degree. than the position of
the energization angle 30.degree., which is the timing at which the
energization to the armature coil is started in the first
energization control.
[0097] The period of the energization to the armature coil is
continued across the range of the energization angle 120.degree.
regardless of the advance angle. According to FIG. 10A, it can be
understood that the rotation number of the rotor is relatively
increased as the advance angle is increased even if the torque of
the rotor is the same. Furthermore, in the three characteristics,
the rotation number is reduced as the torque of the rotor is
increased. Furthermore, as the torque of the rotor is increased,
the differences in the rotation numbers of the rotor in the three
characteristics are reduced.
[0098] The characteristics of the brushless motor 18 in the case in
which the second energization control is carried out will be
described on the basis of FIG. 10B. A solid line represents the
characteristic of an energization angle 120.degree. with an advance
angle 30.degree., a broken line represents the characteristic of an
energization angle 135.degree. with an advance angle 37.5.degree.,
a dashed-dotted line represents the characteristic of an
energization angle 150.degree. with an advance angle 45.degree.,
and a dashed two-dotted line represents the characteristic of an
energization angle 165.degree. with an advance angle 52.5.degree..
The basic characteristics of the brushless motor 18 shown in FIG.
10B are the same as the basic characteristics of the brushless
motor 18 shown in FIG. 10A. The differences in the rotation numbers
in the high-torque region are larger in the characteristics of the
brushless motor 18 shown in FIG. 10B than the characteristics of
the brushless motor 18 shown in FIG. 10A.
[0099] FIG. 11 is a graph chart showing the relation between the
advance angles, the energization angles, and torque ripple rates.
The horizontal axis shows the energization angles. Torque ripples
mean changes, in other words, pulsations of the torque of the
rotor. The torque ripple rate is the ratio of the pulsation width
of the torque with respect to the average of the torque. Herein,
the torque ripple rates of the rotor with respect to an advance
angle 0.degree., an advance angle 15.degree., and an advance angle
30.degree., respectively, are shown. The advance angle 0.degree.
corresponds to first timing of the present invention, and the
advance angle 15.degree. and the advance angle 30.degree.
correspond to second timing of the present invention. Therefore,
the advance angle 15.degree. means advancing the timing to start
energization by the amount corresponding to the energization angle
15.degree. with respect to the advance angle 0.degree., and the
advance angle 30.degree. means to advance the timing to start
energization by the amount corresponding to the energization angle
30.degree. with respect to the advance angle 0.degree..
[0100] According to the graph chart of FIG. 11, it can be
understood that, if the energization angle is constant, the larger
the advance angle becomes, the smaller the torque ripple rate
becomes. On the other hand, it can be understood that, if the
advance angle is constant, there is an inclination that the larger
the energization angle becomes, the smaller the torque ripple rate
becomes. Specifically, it can be understood that, if the brushless
motor 18 is controlled by the energization angle 150.degree. and
the advance angle 30.degree., the torque ripple rate becomes the
lowest. Note that, when the first energization control and the
second energization control are compared with each other, in a case
of the energization angle 135.degree. or more and the energization
angle 165.degree., the torque ripple rate in the case in which the
second energization control is executed can be reduced more than
the torque ripple rate in the case in which the first energization
control is executed.
[0101] FIG. 12 shows an example of comparing the radiated sound
(sound pressures) generated around the brushless motor in the case
in which control is carried out by using rectangular waves as
current waveforms and the case in which control is carried out by
the waveforms smoother than the rectangular waves when control of
the energization to the armature coil of the brushless motor 18 is
executed. When the first energization control is executed, the
current waveform becomes a rectangular wave. When the second
energization control is executed, the current waveform becomes a
smooth waveform. According to FIG. 12, it can be understood that
the sound pressure in the case in which the second energization
control is executed is lower than the sound pressure of the case in
which the first energization control is executed.
[0102] FIG. 13 shows the waveforms showing the relations between
currents and electric signals in the case in which the energization
to the armature coil of the brushless motor 18 is executed. The
waveform of the advance angle 60.degree. and the energization angle
165.degree. is shown by a solid line, the waveform of the advance
angle 0.degree. and the energization angle 120.degree. is shown by
a dashed two-dotted line, the waveform of the advance angle
30.degree. and the energization angle 150.degree. is shown by a
broken line, and the waveform of the advance angle 15.degree. and
the energization angle 120.degree. is shown by a dashed-dotted
line. Among the waveforms shown in FIG. 13, the waveform of the
advance angle 60.degree. and the energization angle 165.degree. has
a most smoothly changed current and approximates a sine wave. More
specifically, the waveform of the advance angle 60.degree. and the
energization angle 165.degree. has the lowest radiated sound (sound
pressure) generated around the brushless motor compared with the
other waveforms and can reduce the actuation sound of the brushless
motor 18.
[0103] FIG. 14 is a graph chart showing the relations between the
advance angles, the energization angles, and sound pressures. FIG.
14 shows the sound pressures at the energization angle 120.degree.
with the advance angle 0.degree., the advance angle 15.degree., and
the advance angle 30.degree., shows the sound pressures at the
energization angle 150.degree. with the advance angle 15.degree.
and the advance angle 30.degree., and shows the sound pressures at
the energization angle 165.degree. with the advance angle
60.degree.. According to FIG. 14, it can be understood that the
sound pressure at the advance angle 15.degree. and the energization
angle 150.degree. and the sound pressure at the advance angle
60.degree. and the energization angle 165.degree. are lower than
the sound pressures at the other advance angles and energization
angles.
[0104] Herein, the advance angle 0.degree. is the first timing, and
the advance angle 15.degree. and the advance angle 30.degree. are
the second timing. Furthermore, the advance angle 60.degree. may be
the second timing at which the timing to start energization is
advanced by the amount corresponding to the energization angle
60.degree. with respect to the advance angle 0.degree., which is
the first timing.
[0105] On the basis of the inclinations shown in FIGS. 12 to 14, it
can be understood that there is an inclination that, if the
energization angle is constant, the larger the advance angle
becomes, the lower the sound pressure becomes. Furthermore, it can
be understood that there is an inclination that, if the advance
angle is constant, the larger the energization angle becomes, the
lower the sound pressure becomes.
[0106] In this embodiment, when the energization to the armature
coil of the brushless motor 18 is controlled, the advance angle and
the energization angle can be controlled in accordance with various
conditions such as the selected mode, the vehicle speed, and the
load of the wiper arm 15 so that the torque ripple rate becomes
small. Furthermore, when the energization to the armature coil of
the brushless motor 18 is controlled, the advance angle and the
energization angle can be controlled in accordance with the various
conditions so that the sound pressure becomes low.
[0107] Furthermore, the rigidity, the attachment position, etc. of
the vehicle body 48 to which the motor apparatus 17 is attached is
different in every vehicle model, and the resonant frequency in the
case in which the brushless motor 18 is actuated is different in
every vehicle model. Therefore, the advance angle and the
energization angle can be tuned for every vehicle model so that the
sound pressure generated around the brushless motor 18 becomes
low.
[0108] The drive apparatus of the present invention is not limited
to that of the above described first embodiment, and it goes
without saying that various modifications can be made within the
range not deviating from the gist thereof. For example, the
brushless motor of the present invention includes the structure of
a star connection in which armature coils are connected in Y
shapes. The brushless motor of the present invention includes one
in which the rotor has an IPM (Interior Permanent Magnet)
structure. In the IPM structure, permanent magnets are buried in
the rotor core. Meanwhile, the first period is not limited to the
energization angle 120.degree., but may be less than the
energization angle 120.degree., or may exceed the energization
angle 120.degree..
[0109] The brushless motor of the present invention includes the
inner-rotor-type structure in which the rotor is disposed in the
inner side of the stator and an outer-rotor-type structure in which
the rotor is disposed in the outer side of the stator.
[0110] The wiper apparatus of the present invention includes a
wiper apparatus in which the wiper blade wipes off a rear glass.
Thus, the wind glass of the wiper apparatus of the present
invention includes a windshield and a rear glass. Furthermore, the
wiper apparatus of the present invention includes a configuration
in which two wiper arms are singularly driven by a single brushless
motor.
[0111] The brushless motor of the first embodiment includes, other
than the wiper motor that operates the wiper apparatus, brushless
motors provided for operating action members such as a door, a
roof, a glass, etc. in, for example, a power slide door apparatus,
a sunroof apparatus, or a power window apparatus provided in a
vehicle. Note that the drive apparatus 37 corresponds to a control
unit and a mode switching unit of the present invention.
Second Embodiment
[0112] The second embodiment is one example of a motor apparatus
applied to the vehicle. FIGS. 2-5 and 9 used in the first
embodiment will be used also in the second embodiment.
[0113] A vehicle 10 shown in FIG. 15 has a windshield 11.
Furthermore, the vehicle 10 has a first wiper apparatus 12 and a
second wiper apparatus 13, which wipe off the windshield 11. The
first wiper apparatus 12 and the second wiper apparatus 13 are
disposed at the positions which are different from each other in
the width direction of the vehicle 10. Since the first wiper
apparatus 12 and the second wiper apparatus 13 have approximately
left-right symmetric structures, the first wiper apparatus 12 will
be described hereinafter for the sake of convenience. The first
wiper apparatus 12 has: a wiper arm 15 which swings about a pivot
shaft 14; and a wiper blade 16 which is attached to the wiper arm
15. Furthermore, the first wiper apparatus 12 has a motor apparatus
17 which drives the wiper arm 15. The motor apparatus 17 is
provided with: a brushless motor 18; and a speed reduction
mechanism 19 which transmits the power of the brushless motor 18 to
the pivot shaft 14.
[0114] The brushless motor 18 is formed as shown in FIGS. 2 to 4.
The brushless motor 18 in this embodiment has a motor case 20
formed into a bottomed cylindrical shape, and an armature 21
serving as a stator is provided on an inner periphery of the motor
case 20. The armature 21 has a stator core 22 and armature coils
V1, V2, U1, U2, W1, and W2 wound around the stator core 22. The
stator core 22 is stacked electrically-conductive metal plates,
and, on the inner periphery of the stator core 22, a plurality of,
specifically, six teeth 23 are provided at intervals in the
circumferential direction and disposed at a mechanical angle of
60.degree.. The armature coils V1, V2, U1, U2, W1, and W2 are
separately wound around the six teeth 23, respectively.
[0115] The armature coils V1 and V2 correspond to V-phases, the
armature coils U1 and U2 correspond to U-phases, and the armature
coils W1 and W2 correspond to W-phases. In FIG. 4, clockwise with
respect to the armature 21, the armature coil U1, the armature coil
V1, the armature coil W1, the armature coil U2, the armature coil
V2, and the armature coil W2 are provided in this order. The
armature coils U1 and U2 are in positional relationship of
mechanical angle 180.degree. with each other, the armature coils V1
and V2 are in positional relationship of mechanical angle
180.degree. with each other, and the armature coils U1 and U2 are
in positional relationship of mechanical angle 180.degree. with
each other.
[0116] Next, the configuration of the armature 21 will be described
with reference to FIGS. 5 and 16. The armature coils U1 and U2 are
connected in series, the armature coils V1 and V2 are connected in
series, and the armature coils W1 and W2 are connected in series,
Furthermore, an end "Ua" of the armature coil U1 and an end "Ub" of
the armature coil W2 are connected by a terminal 24. Also, an end
"Vb" of the armature coil U2 and an end "Va" of the armature coil
V1 are connected by a terminal 25. Furthermore, an end "Wa" of the
armature coil W1 and an end "Wb" of the armature coil V2 are
connected by a terminal 26. In this manner, the brushless motor 18
employs delta connections as the connection structure of the six
armature coils V1, V2, U1, U2, W1, and W2.
[0117] On the other hand, the brushless motor 18 has a rotor 27,
and the rotor 27 is provided in the inner side of the armature 21.
The brushless motor 18 has an inner-rotor-type structure in which
the rotor 27 is disposed in the inner side of the armature 21,
which is serving as a stator. The rotor 27 has a rotor shaft 28 and
permanent magnets 29N and 29S of four polarities fixed to an outer
periphery of the rotor shaft 28 via a rotor core 30. The polarity
of the two permanent magnets 29N is the N pole, the polarity of the
two permanent magnets 29S is the S pole, and the permanent magnets
29N and the permanent magnets 29S are alternately disposed along
the circumferential direction of the rotor shaft 28. The brushless
motor 18 has four permanent magnets, six armature coils, and a
four-pole six-slot structure.
[0118] In this manner, the brushless motor 18 has a SPM (Surface
Permanent Magnet) structure. The SPM structure is a structure in
which the permanent magnets 29N and 29S are fixed to the outer
peripheral surface of the rotor core 30. The rotor core 30 is
formed of an iron-based magnetic material. Furthermore, the rotor
shaft 28 is rotatably supported by a plurality of, specifically,
two bearings 49.
[0119] On the other hand, the motor apparatus 17 is provided with a
gear case 31, which houses the speed reduction mechanism 19, and
the gear case 31 and the motor case 20 are fixed by a fastener
member (not shown). Part of the rotor shaft 28 in the length
direction is disposed in the motor case 20, and the remaining part
thereof is disposed in the gear case 31. A worm 32 is formed on the
outer periphery of the part of the rotor shaft 28 that is disposed
in the gear case 31. A worm wheel 33 is provided in the gear case
31. A gear 33a is formed on the outer periphery of the worm wheel
33, and the gear 33a and the worm 32 are meshed with each
other.
[0120] The pivot shaft 14 is disposed concentrically with the worm
wheel 33, and the pivot shaft 14 is integrally rotated with the
worm wheel 33. The worm 32 and the gear 33a are the speed reduction
mechanism 19 in this embodiment. The speed reduction mechanism 19
is a mechanism which reduces the rotation number (output rotation
number) of the pivot shaft 14 with respect to the rotation number
(input rotation number) of the rotor 27 when the power of the rotor
27 is transmitted to the pivot shaft 14. The rotation number in
this embodiment is the rotation number per unit time and is
synonymous with a rotation speed.
[0121] Furthermore, in FIG. 3, in an upper part of the gear case
31, a shaft hole (not shown) is provided. The end of the pivot
shaft 14 that is in the opposite side of the end to which the worm
wheel 33 is fixed is exposed to outside via the shaft hole of the
gear case 31. The wiper arm 15 is coupled to the part of the pivot
shaft 14 that is exposed to outside the gear case 31.
[0122] On the other hand, a sensor magnet 34 is attached to the
part of the rotor shaft 28 that is disposed in the gear case 31.
The sensor magnet 34 is integrally rotated with the rotor shaft 28.
The sensor magnet 34 has a cylindrical shape, and the sensor magnet
34 is magnetized so that N poles and S poles are alternately
juxtaposed along the circumferential direction of the rotor shaft
28.
[0123] An opening is provided at a part of the gear case 31 that is
in the opposite side of the shaft hole thereof. This opening is
formed for inserting the worm wheel 33, the pivot shaft 14, etc.
into the gear case 31. An under cover 35, which closes the opening,
is provided. The under cover 35 has a tray shape, and a control
board 36 is provided in the space surrounded by the under cover 35
and the gear case 31.
[0124] As shown in FIG. 16, a drive apparatus 37, which controls
the brushless motor 18, is provided on the control board 36. The
drive apparatus 37 has an inverter circuit 38, which controls
energization to the six armature coils V1, V2, U1, U2, W1, and W2.
The inverter circuit 38 is connected to the terminals 24, 25, and
26. Furthermore, the under cover 35 is provided with a connector
39; and, when an electric-power-source cable connected to an
external electric power source 40 is connected to the connector 39,
the external electric power source 40 and the inverter circuit 38
are connected to each other. The external electric power source 40
includes a battery, a capacitor, or the like mounted on the vehicle
10.
[0125] Furthermore, the inverter circuit 38 is provided with a
plurality of, specifically, six switching elements 38a to 38f which
separately connect or shut off supply paths between the external
electric power source 40 and the six armature coils V1, V2, U1, U2,
W1, and W2. The six switching elements 38a to 38f are composed of,
for example, semiconductor elements such as FETs. More
specifically, the positive-electrode-side switching element 38b
corresponding to the U-phase and connected to the positive
electrode of the external electric power source 40 and the
negative-electrode-side switching element 38e corresponding to the
U-phase and connected to the negative electrode side of the
external electric power source 40 are provided.
[0126] Furthermore, the positive-electrode-side switching element
38b corresponding to the V-phase and connected to the positive
electrode of the external electric power source 40 and the
negative-electrode-side switching element 38e corresponding to the
V-phase and connected to the negative electrode side of the
external electric power source 40 are provided. Furthermore, the
positive-electrode-side switching element 38c corresponding to the
W-phase and connected to the positive electrode of the external
electric power source 40 and the negative-electrode-side switching
element 38f corresponding to the W-phase and connected to the
negative electrode side of the external electric power source 40
are provided.
[0127] Herein, the switching elements 38a, 38b, and 38c are
connected in mutually parallel, and the switching elements 38d,
38e, and 38f are connected in mutually parallel. Furthermore, the
switching element 38a and the switching element 38d are connected
in series, the switching element 38b and the switching element 38e
are connected in series, and the switching element 38c and the
switching element 38f are connected in series. Furthermore, a
source of the switching element 38a and a drain of the switching
element 38d are connected to the terminal 24. Furthermore, a source
of the switching element 38b and a drain of the switching element
38e are connected to the terminal 25. Furthermore, a source of the
switching element 38c and a drain of a switching element 38f are
connected to the terminal 26.
[0128] Furthermore, the drive apparatus 37 is provided with a
control circuit 50 for controlling the six switching elements 38a
to 38f. The control circuit 50 is a publicly-known microcomputer
provided with a CPU, a RAM, a ROM, etc.
[0129] Furthermore, the drive apparatus 37 has a PWM-signal
generating circuit 51, and the signals of the PWM-signal generating
circuit 51 are input to the control circuit 50. The control circuit
50 outputs drive signals which separately control the six switching
elements 38a to 38f, and the PWM signals are superimposed on the
drive signals. Therefore, the switching elements 38a to 38f are
driven by PWM control and are intermittently turned on/off in
respective energization periods.
[0130] In addition, the values of the currents supplied to the six
armature coils V1, V2, U1, U2, W1, and W2 are controlled by
controlling ratios at which the switching elements 38a to 38f are
separately turned on, in other words, "duty ratios". In other
words, the energization periods in which electric power is supplied
to the six armature coils V1, V2, U1, U2, W1, and W2 can be
increased/reduced between 0% and 100% with respect to the entire
period in which electric power can be distributed. Here, when waves
of currents to be respectively supplied to the armature coils V1,
V2, U1, U2, W1, and W2 are represented by electric angles, the
"energization periods" have important implications.
[0131] Furthermore, the brushless motor 18 of this embodiment can
rotate the rotor 27 forward/backward by subjecting the on and off
of the switching element 38a to switching control and inverting the
directions of energization to the six armature coils V1, V2, U1,
U2, W1, and W2.
[0132] The control board 36 is disposed along the planar direction
which is perpendicular to a first axis A1 of the pivot shaft 14.
The first axis A1 serves as a center when the pivot shaft 14
rotates. Three sensors 41, 42, and 43 are attached to the control
board 36. All of the three sensors 41, 42, and 43 are Hall ICs, and
the three sensors 41, 42, and 43 are fixed to the control board 36
without contacting the sensor magnet 34. In this embodiment, the
sensor 41 outputs a switching signal corresponding to the W-phase,
the sensor 42 outputs a switching signal corresponding to the
V-phase, and the sensor 43 outputs a switching signal corresponding
to the U-phase. The three sensors 41, 42, and 43 are arranged in
the direction intersecting with a second axis B1 of the rotor shaft
28 as shown in FIG. 2 by a planar view of the control board 36. The
second axis B1 serves as a center when the rotor shaft 28
rotates.
[0133] The disposition range of the three sensors 41, 42, and 43
and the disposition range of the sensor magnet 34 are overlapped
with each other at least partially in the direction along the
second axis B1. Furthermore, if it is assumed that the control
board 36 is horizontally disposed, as shown in FIG. 3, the single
sensor 42 corresponding to V-phase is disposed immediately below
the second axis B1. The three sensors 41, 42, and 43 are disposed
at equal intervals in the direction intersecting with the second
axis B1. Furthermore, the sensor 42 is disposed between the sensor
41 and the sensor 43.
[0134] When the rotor 27 is rotated and moves the magnetic poles of
the sensor magnet 34, the three sensors 41, 42, and 43 carry out
switching operations, and the three sensors 41, 42, and 43
separately generate switching signals (output signals),
respectively. On the basis of the switching signals of the three
sensors 41, 42, and 43, the control circuit 50 can detect the
rotation phase and the rotation number of the rotor 27. The
rotation phase of the rotor 27 is an angle or a position in a
rotation direction defined with respect to a reference position.
The control circuit 50 further has a function to estimate an
actuation load on the basis of the switching signals of the three
sensors 41, 42, and 43.
[0135] Furthermore, a wiper switch 44 is provided in the interior
of the vehicle 10. When a driver manipulates the wiper switch 44
and selects a low-speed mode or a high-speed mode, manipulation
signals of the wiper switch 44 are input to the control circuit 50.
Furthermore, a vehicle-speed sensor 45, which detects the
travelling speed of the vehicle 10, is provided, and detection
signals of the vehicle-speed sensor 45 are input to the control
circuit 50.
[0136] Furthermore, the control circuit 50 stores, in advance, data
of outputs from the rotor 27 of the brushless motor 18, that is,
data of energization pattern and the like of the six armature coils
V1, V2, U1, U2, W1, and W2, in order to control the rotation number
and the torque. More specifically, the control circuit 50 stores,
in advance, data, arithmetic expressions, etc. that control the
timing to turn on/off the switching elements 38a of the inverter
circuit 38, the duration time to turn on the switching elements 38a
to 38f on the basis of various conditions such as the manipulation
signals of the wiper switch 44, the detection signals of the
vehicle-speed sensor 45, and the actuation load of the wiper arm
15.
[0137] The actuation load of the wiper arm 15 can be specifically
estimated from the switching signals of the sensors 41, 42, and 43.
In the control circuit 50, for example, it is assumed that the
high-speed mode is selected, a target rotation number of the rotor
27 to achieve a target wiping speed of the wiper arm 15 is
obtained, and energization control is carried out so that the
actual rotation number of the rotor 27 becomes the target rotation
number. Herein, In the control circuit 50, if the actual rotation
number of the rotor 27 does not become the target rotation number,
it can be estimated that the action resistance of the wiper arm 15,
in other words, the actuation load of the wiper arm 15 is increased
by snow or the like.
[0138] Also, since the wind pressure received by the wiper arm 15
is changed depending on the vehicle speed, the actuation load of
the wiper arm 15 is changed depending on the vehicle speed.
Furthermore, the wind pressure received by the wiper arm 15 is
changed depending on the inclination angle of the windshield 11,
and, therefore, the actuation load of the wiper arm 15 is changed
depending on the inclination angle of the windshield 11. The
inclination angle of the windshield 11 is expressed by the
acute-angle-side inclination angle of the windshield 11 with
respect to the horizontal plane. Furthermore, the actuation load of
the wiper arm 15 is changed depending on the length of the wiper
blade 16.
[0139] Note that the gear case 31 is provided with attachment parts
46 at plural, for example, three locations, and the attachment
parts 46 are provided with shaft holes, respectively. Furthermore,
buffer materials 47 are attached to the shaft holes of the
attachment parts 46, respectively. The buffer materials 47 are
annularly formed synthetic rubbers, and screw members are inserted
to holes 47a of the buffer materials 47 to attach the motor
apparatus 17 to a vehicle body 48.
[0140] Next, a control example which can be executed by the motor
apparatus 17 in order to control each of the first wiper apparatus
12 and the second wiper apparatus 13 will be described. In the
control circuit 50 of the motor apparatus 17, the on/off of the
switching elements 38a are controlled by the manipulation signals
of the wiper switch 44 or a condition other than the manipulation
signals of the wiper switch 44. Furthermore, on the basis of the
detection signals of the three sensors 41, 42, and 43, the control
circuit 50 estimates the rotation phase of the rotor 27, in other
words, the angle thereof in a rotation direction and carries out
energization control on the basis of the rotation phase of the
rotor 27. More specifically, the positive-electrode-side switching
elements 38a 38b, and 38c are sequentially turned on/off
respectively by predetermined electric angles, in other words,
energization angles, and the negative-electrode-side switching
elements 38d, 38e, and 38f are sequentially turned on/off by
predetermined electric angles, thereby switching the energization
state with respect to the armature coils U1, U2, V1, V2, W1, and W2
and commutating phase currents.
[0141] When the above described control is repeated, a rotating
magnetic field is formed by the armature 21, and the rotor 27 is
rotated. The brushless motor 18 can subject the rotor 27 to forward
rotations, stop, and backward rotations by subjecting the on and
off of the switching elements 38a to 38f to switching control and
inverting the directions of electric distribution to the armature
coils U1, U2, V1, V2, W1, and W2. If the power of the rotor 27 is
transmitted to the pivot shaft 14 via the speed reduction mechanism
19, the wiper arm 15 reciprocates within the range of a
predetermined angle, and the windshield 11 is wiped off by the
wiper blade 16.
[0142] In FIG. 15, the wiper arm 15 reciprocates, for example,
between a lower inverting position D1 shown by a solid line and an
upper inverting position D2 shown by a dashed two-dotted line. The
upper inverting position D2 is at a position which is more distant
than the lower inverting position D1 is from the vehicle body 48 to
which the motor apparatus 17 is attached. The location at which the
motor apparatus 17 is attached is, for example, a lower side of a
louver.
[0143] Furthermore, the range in which the wiper arm 15 is moved
from the lower inverting position toward the upper inverting
position D2 is a forward path, and the range in which the wiper arm
15 is moved from the upper inverting position D2 toward the lower
inverting position D1 is a return path. Note that it is assumed
that, if the wiper arm 15 is moved in the forward path, the rotor
27 shown in FIG. 3 is rotated, for example, counterclockwise; and,
if the wiper arm 15 is moved in the return path, the rotor 27 is
rotated clockwise.
[0144] As described above, the control circuit 50 can control
output of the rotor 27 by controlling the timing of the electric
angles to turn on or off the switching elements 38a to 38f, the
sections of the electric angles to turn on the switching elements
38a to 38f, etc. The timing of the electric angles can be also
referred to as the points of the electric angles. The brushless
motor 18 has a characteristic that the rotation number of the rotor
27 is increased as the current value is increased. Furthermore, the
brushless motor 18 has a characteristic that the torque of the
rotor 27 is reduced as the rotation number of the rotor 27 is
increased.
[0145] Furthermore, when the brushless motor 18 of this embodiment
controls the output, in other words, the rotation number and torque
of the rotor 27, the brushless motor 18 can switch and execute
first energization control, weak field control, and third
energization control. The first energization control, the weak
field control, and the third energization control are switched by
various conditions such as the detection signals of the wiper
switch 44, the detection signals of the vehicle-speed sensor 45,
the load of the wiper arm 15, and the moving direction of the wiper
arm 15. Particularly, the weak field control can be executed when
there is a request to increase the rotation number of the rotor 27
compared with the first energization control. On the other hand,
the third energization control can be executed when there is a
request to increase the torque of the rotor 27 compared with the
first energization control. That is, the third energization control
is executed when the actuation load of the wiper arm 15 is
increased by snow and the like deposited on the front windshield
11.
[0146] The drive patterns of the switching elements 38a to 38f in
the first energization control will be described by the time charts
of FIGS. 17 and 18. FIG. 17 shows the drive patterns of the
switching elements 38a to 38f in the case in which the wiper arm 15
is moved in the forward path, and FIG. 18 shows the drive patterns
of the switching elements 38a to 38f in the case in which the wiper
arm 15 is moved in the return path.
[0147] The drive patterns of FIGS. 17 and 18 are divided into six
energization stages ST1 to ST6, which are started from rising edges
or falling edges of the switching signals output from the sensors
41, 42, and 43, and, in this case, the energization stages are
divided by the electric angles (degrees) determined in advance. In
the examples of FIGS. 17 and 18, the energization stages are
divided by the ranges (sections) of the electric angle 60.degree..
The rising of the switching signal means switching of the switching
signal from "off" to "on", and the falling of the switching signal
means switching of the switching signal from "on" to "off".
[0148] In FIGS. 17 and 18, the on-section of each of the switching
signals of the sensors 41, 42, and 43 is set to an electric angle
180.degree., and the on-sections of the switching signals of the
sensors 41, 42, and 43 are set so as to be mutually shifted by the
electric angle 60.degree..
[0149] FIG. 17 shows the drive patterns corresponding to the
forward path of the wiper arm 15, wherein the switching signal of
the sensor 43 corresponding to the U-phase is turned on at the
timing of an electric angle 0.degree. and is turned off at the
timing of the electric angle 180.degree.. While the switching
signal of the sensor 43 corresponding to the U-phase is turned on,
the switching signal of the sensor 41 corresponding to the W-phase
is turned on at the timing of the electric angle 60.degree.. The
switching signal of the sensor 43 corresponding to the U-phase is
turned off at the timing of an electric angle 240.degree..
[0150] Furthermore, while the switching signal of the sensor 41
corresponding to the W-phase is turned on, the switching signal of
the sensor 42 corresponding to the V-phase is turned on at the
timing of the electric angle 120.degree.. The switching signal of
the sensor 42 corresponding to the V-phase is turned off at the
timing of an electric angle 300.degree.. The control circuit 50
controls the switching elements 38a to 38f in a below manner on the
basis of the switching signals of the sensors 41, 42, and 43.
[0151] The positive-electrode-side switching element 38a of the
U-phase is constantly turned on in the section of an electric angle
120.degree. from the timing of an electric angle 30.degree. to the
timing of an electric angle 150.degree. and is alternately switched
to "on" and "off" in the section of an electric angle 120.degree.
from the timing of an electric angle 210.degree. to the timing of
an electric angle 330.degree.. Meanwhile, the
negative-electrode-side switching element 38d of the U-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
210.degree. to the timing of the electric angle 330.degree..
[0152] Furthermore, the positive-electrode-side switching element
38b of the V-phase is alternately switched to "on" and "off" in the
section of an electric angle 120.degree. from the timing of the
electric angle 330.degree. to the timing of an electric angle
90.degree.. Furthermore, the positive-electrode-side switching
element 38b of the V-phase is turned on at the timing of the
electric angle 150.degree. and is constantly turned on until it is
turned off at the timing of an electric angle 270.degree.. On the
other hand, the negative-electrode-side switching element 38e of
the V-phase is alternately switched to "on" and "off" in the
section of an electric angle 120.degree. from the timing of the
electric angle 330.degree. to the timing of the electric angle
90.degree..
[0153] Furthermore, the positive-electrode-side switching element
38c of the W-phase is constantly turned on in the section of an
electric angle 120.degree. from the timing of the electric angle
270.degree. to the timing of the electric angle 30.degree., and
positive-electrode-side switching element 38c of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
90.degree. to the timing of the electric angle 210.degree..
Furthermore, the negative-electrode-side switching element 38c of
the W-phase is alternately switched to "on" and "off" in the
section of an electric angle 120.degree. from the timing of the
electric angle 90.degree. to the timing of the electric angle
210.degree..
[0154] On the other hand, FIG. 18 shows the drive patterns
corresponding to the return path, wherein the switching signal of
the sensor 43 corresponding to the U-phase is turned on at the
timing of the electric angle 0.degree. and is turned off at the
timing of the electric angle 180.degree.. While the switching
signal of the sensor 43 corresponding to the U-phase is turned on,
the switching signal of the sensor 42 corresponding to the V-phase
is turned on at the timing of the electric angle 60.degree.. The
switching signal of the sensor 42 corresponding to the V-phase is
turned off at the timing of the electric angle 240.degree..
[0155] Furthermore, while the switching signal of the sensor 42
corresponding to the V-phase is turned on, the switching signal of
the sensor 41 corresponding to the W-phase is turned on at the
timing of the electric angle 120.degree.. The switching signal of
the sensor 41 corresponding to the W-phase is turned off at the
timing of the electric angle 300.degree.. The control circuit 50
controls the switching elements 38a to 38f in a below manner on the
basis of the switching signals of the sensors 41, 42, and 43.
[0156] The positive-electrode-side switching element 38a of the
U-phase is alternately switched to "on" and "off" in the section of
an electric angle 120.degree. from the timing of the electric angle
30.degree. to the timing of the electric angle 150.degree..
Meanwhile, in the section of an electric angle 120.degree. from the
timing of the electric angle 210.degree. to the timing of the
electric angle 330.degree., the switching element 38a is constantly
turned on. On the other hand, the negative-electrode-side switching
element 38d of the U-phase is alternately switched to "on" and
"off" in the section of an electric angle 120.degree. from the
timing of the electric angle 30.degree. to the timing of the
electric angle 150.degree..
[0157] Furthermore, the positive-electrode-side switching element
38b of the V-phase is constantly turned on in the section of an
electric angle 120.degree. from the timing of the electric angle
90.degree. to the timing of the electric angle 210.degree..
Furthermore, the positive-electrode-side switching element 38b of
the V-phase is alternately switched to "on" and "off" in the
section of an electric angle 120.degree. from the timing of an
electric angle 270.degree. to the timing of the electric angle
30.degree.. On the other hand, the negative-electrode-side
switching element 38e of the V-phase is alternately switched to
"on" and "off" in the section of an electric angle 120.degree. from
the timing of the electric angle 270.degree. to the timing of the
electric angle 30.degree..
[0158] Furthermore, the positive-electrode-side switching element
38c of the W-phase is constantly turned on in the section of an
electric angle 120.degree. from the timing of the electric angle
330.degree. to the timing of the electric angle 90.degree., the
positive-electrode-side switching element 38c of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
150.degree. to the timing of the electric angle 270.degree., and,
the negative-electrode-side switching element 38f of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
150.degree. to the timing of the electric angle 270.degree..
[0159] Then, the drive patterns of the switching elements 38a to
38f in the weak field control, which is the second energization
control, will be described on the basis of FIG. 19. The weak field
control is executed when the wiper arm 15 is moved in the forward
path; and, when the wiper arm 15 is moved in the return path, the
first energization control is executed. Also in FIG. 19, as well as
FIG. 17, the energization stage ST1 to the energization stage ST6
and the electric angle 0.degree. to the electric angle 360.degree.
are shown. In FIG. 19, the on/off timing of the switching signals
of the sensors 41 to 43 are the same as the on/off timing of the
switching signals of the sensors 41 to 43 in FIG. 17.
[0160] FIG. 19 shows the drive patterns of the switching elements
38a to 38f corresponding to the forward path of the wiper arm 15,
and the control timing of the switching elements 38a to 38f shown
in FIG. 19 is forward, in other words, by the amount corresponding
to the section of an electric angle 30.degree. compared with the
control timing of the switching elements 38a to 38f shown in FIG.
7.
[0161] First, the positive-electrode-side switching element 38a of
the U-phase is constantly turned on in the section of an electric
angle 120.degree. from the timing of an electric angle 15.degree.
to the timing of an electric angle 135.degree. and is alternately
switched to "on" and "off" in the section of an electric angle
120.degree. from the timing of an electric angle 195.degree. to the
timing of an electric angle 315.degree.. Meanwhile, the
negative-electrode-side switching element 38d of the U-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
195.degree. to the timing of the electric angle 315.degree..
[0162] Furthermore, the positive-electrode-side switching element
38b of the V-phase is alternately switched to "on" and "off" in the
section of an electric angle 120.degree. from the timing of the
electric angle 315.degree. to the timing of the electric angle
75.degree., and the positive-electrode-side switching element 38b
of the V-phase is constantly turned on while it is turned on at the
timing of the electric angle 135.degree. and turned off at the
timing of an electric angle 255.degree.. On the other hand, the
negative-electrode-side switching element 38e of the V-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
315.degree. to the timing of the electric angle 75.degree..
[0163] Furthermore, the positive-electrode-side switching element
38c of the W-phase is constantly turned on in the section of an
electric angle 120.degree. from the timing of the electric angle
255.degree. to the timing of the electric angle 15.degree., the
positive-electrode-side switching element 38c of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
75.degree. to the timing of the electric angle 195.degree., and the
negative-electrode-side switching element 38f of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 120.degree. from the timing of the electric angle
75.degree. to the timing of the electric angle 195.degree..
[0164] The above "weak field control" is a control for weakening
the magnetic field generated by the armature 21 in comparison with
that of the first energization control. When this weak field
control is carried out, the back electromotive force generated at
the armature coils U1, U2, V1, V2, W1, and W2 is reduced, and the
rotation number of the rotor 27 is increased. FIG. 9 is a diagram
showing characteristics of the brushless motor 18. In FIG. 9, the
rotation number of the brushless motor 18 is shown by a vertical
axis, and the torque of the brushless motor 18 is shown by a
horizontal axis. Furthermore, FIG. 9 shows an example of the
characteristics for the low-speed mode and an example of high-speed
mode characteristics. It is possible to switch between the
low-speed mode and an example of high-speed mode when the driver
manipulates the wiper switch 44 and selects the low-speed mode or
the high-speed mode.
[0165] In the brushless motor 18 of this embodiment, for example, a
single characteristic is present at the position shown by a solid
line so that the rotation number and torque corresponding to the
low-speed mode characteristic of FIG. 9 can be obtained when the
rating thereof is set. Therefore, if the low-speed mode is
selected, the required rotation number and torque can be obtained
in the range equal to and blow the single characteristic by
executing the first energization control.
[0166] The single characteristic is the target output of the case
in which the actual vehicle speed of the vehicle 10 is equal to or
less than a reference vehicle speed, in other words, is the
characteristic that satisfies the low-speed mode. An apparent
characteristic is the target output of the case in which the actual
vehicle speed of the vehicle 10 exceeds the reference vehicle
speed, in other words, is the characteristic that satisfies the
high-speed mode. The target output can be expressed by the rotation
number and torque of the rotor 27. The conditions that determine
the target output include various conditions such as the detection
signals of the wiper switch 44, the detection signals of the
vehicle-speed sensor 45, and the load of the wiper arm 15.
[0167] On the other hand, for example, when the high-speed mode is
selected and the torque and rotation number required to the rotor
27 exceed the single characteristic, the rotation number and torque
exceeding the single characteristic can be obtained by executing
the weak field control or the second energization control by the
control circuit 50. As a result, the characteristic of the
brushless motor 18 is equivalent to the presence at the positions
shown by a dashed-dotted line in FIG. 9 in terms of appearance.
[0168] Therefore, the brushless motor 18 can be subjected to
determination of the rating thereof while using the low-speed mode
as a reference in terms of design, and the size of the brushless
motor 18 can be reduced as much as possible. The fact that the
rotation number of the brushless motor 18 can be increased and the
torque can be increased without changing the current value means
that a torque constant is relatively increased. In other words, the
brushless motor 18 of this embodiment can generate high torque as
much as possible with smaller electric power consumption, and motor
efficiency is improved.
[0169] Next, the drive patterns of the switching elements 38a to
39f in the third energization control will be described on the
basis of FIG. 20. The third energization control is executed when
the wiper arm 15 is moved in the forward path; and, when the wiper
arm 15 is moved in the return path, the first energization control
is executed. On the basis of the rotation direction of the rotor
27, the control circuit 50 detects in which one of the forward path
and the return path the wiper arm 15 is moved.
[0170] FIG. 20 also shows the energization stage ST1 to the
energization stage ST6 and the electric angle 0.degree. to the
electric angle 360.degree. as well as FIG. 17. In FIG. 20, the
on/off timing of the switching signals of the sensors 41 to 43 is
the same as the on/off timing of the switching signals of the
sensors 41 to 43 in FIG. 17.
[0171] The control timing of the switching elements 38a to 38f
shown in FIG. 20 is advanced by the amount corresponding to the
section of an electric angle 15.degree. compared with the control
timing of the switching elements 38a to 38f shown in FIG. 17. This
point is the same as the weak field control.
[0172] First, the positive-electrode-side switching element 38a of
the U-phase is constantly turned on in the section of an electric
angle 150.degree. from the timing of the electric angle 15.degree.
to the timing of an electric angle 165.degree. and is alternately
switched to "on" and "off" in the section of an electric angle
150.degree. from the timing of the electric angle 195.degree. to
the timing of an electric angle 345.degree.. Meanwhile, the
negative-electrode-side switching element 38d of the U-phase is
alternately switched to "on" and "off" in the section of an
electric angle 150.degree. from the timing of the electric angle
195.degree. to the timing of the electric angle 345.degree..
[0173] Meanwhile, the positive-electrode-side switching element 38b
of the V-phase is alternately switched to "on" and "off" in the
section of an electric angle 150.degree. from the timing of the
electric angle 315.degree. to the timing of an electric angle
105.degree.. Furthermore, the positive-electrode-side switching
element 38b of the V-phase is turned on at the timing of the
electric angle 135.degree. and is constantly turned on in the
section of an electric angle 150.degree. until it is turned off at
the timing of an electric angle 285.degree.. On the other hand, the
negative-electrode-side switching element 38e of the V-phase is
alternately switched to "on" and "off" in the section of an
electric angle 150.degree. from the timing of the electric angle
315.degree. to the timing of the electric angle 105.degree..
[0174] Furthermore, the positive-electrode-side switching element
38c of the W-phase is constantly turned on in the section of an
electric angle 150.degree. from the timing of the electric angle
255.degree. to the timing of the electric angle 45.degree., the
positive-electrode-side switching element 38c of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 150.degree. from the timing of the electric angle
75.degree. to the timing of an electric angle 225.degree., and the
negative-electrode-side switching element 38c of the W-phase is
alternately switched to "on" and "off" in the section of an
electric angle 150.degree. from the timing of the electric angle
75.degree. to the timing of the electric angle 225.degree..
[0175] In this manner, in the third energization control, the
section of the electric angle 150.degree. in which each of the
switching elements 38a to 38f is turned on is longer by the amount
corresponding to an electric angle 30.degree. than the section of
the electric angle 120.degree. in which each of the switching
elements 38a to 38f is turned on in the first energization control
and the weak field control. In other words, it is longer by the
amount corresponding to an electric angle 15.degree. at each of the
beginning and the end of the section of the electric angle
120.degree..
[0176] Next, regarding attachment of the sensors 41 to 43 to the
control board 36, a case in which an error has occurred in the
attachment positions thereof and causes the mutual distances
between the sensors 41 to 43 to be different from targeted
distances is simulated. In such a case, if the rotation position of
the rotor 27 is estimated on the basis of the switching signals of
the sensors 41 to 43, there is a difference between the actual
rotation position of the rotor 27 and the estimated rotation
position. Therefore, if the first energization control, the weak
field control, or the third energization control is executed on the
basis of the switching signals of the sensors 41 to 43, the timing
to turn on/off the switching elements 38a to 38f and the
energization periods thereof may become inappropriate.
[0177] In order to avoid such inconvenience, the drive apparatus 37
can carry out control as described below. First, an example of
ideal waveforms of the switching signals of the sensors 41 to 43 is
shown by a time chart of FIG. 21. The time chart of FIG. 21 shows
electric angles by the sections each corresponding to 60.degree.
for the sake of convenience. The ideal waveforms of the switching
signals of the sensors 41 to 43 switch edges from "on" to "off",
and switch edges from "off" to "on" at every electric angle
60.degree..
[0178] In order to correct the phase shifting of the switching
signals of the sensors 41 to 43, on the basis of the edge switching
timing of a predetermined switching signal, the drive apparatus 37
estimates the edge switching timing which occurs thereafter.
[0179] For example, if the edge switching timing ahead by an
electric angle 120.degree. is calculated at every switching of edge
timing, on the basis of the edge switching timing of the switching
signal of the sensor 43 of the U-phase, the edge switching timing
of the switching signal of the sensor 42 of the V-phase is
estimated. Meanwhile, on the basis of the edge switching timing of
the switching signal of the sensor 42 of the V-phase, the edge
switching timing of the switching signal of the sensor 41 of the
W-phase is estimated. Furthermore, on the basis of the edge
switching timing of the switching signal of the sensor 41 of the
W-phase, the edge switching timing of the switching signal of the
sensor 43 of the U-phase is estimated.
[0180] Herein, in the time chart shown in FIG. 22, a method of
calculating the ideal edge switching timing of the sensor 42 of the
V-phase ahead by the electric angle 120.degree. on the basis of the
edge switching timing of the switching signal of the sensor 43 of
the U-phase can be expressed by the following Equations (1) and
(2).
The time corresponding to the electric angle 120.degree.
(.DELTA.t120)=.DELTA.t180.times.0.67 Equation (1)
The timing ahead by the electric angle 120.degree.
(p120)=.DELTA.t120+FRT Equation (2)
[0181] Here, "0.67" is a coefficient corresponding to the electric
angle 120.degree. with respect to the section of the electric angle
180.degree., in which on or off state of the switching signal is
continued, ".DELTA.t180" is the time corresponding to the section
of the electric angle 180.degree., and "FRT" is the time measured
by a timer of the drive apparatus 37. That is, at every edge
switching timing of the switching signal of the sensor 43, the
ideal switching timing of the switching signal of the V-phase
sensor 42 delayed by the electric angle 120.degree. after the
timing is estimated.
[0182] On the basis of the ideal switching timing, the drive
apparatus 37 of this embodiment obtains, by an electric angle, the
phase difference between the ideal switching timing and the
switching timing of the actually detected switching signal and
corrects the phase difference, thereby obtaining the ideal waveform
of the switching signal. When the first energization control, the
weak field control, or the third energization control is carried
out, the drive apparatus 37 controls on/off of the switching
elements 38a to 38f on the basis of the ideal waveforms of the
switching signals.
[0183] Next, a specific correction example of the switching signal
will be described. Herein, an example which uses the switching
signal of the sensor 42 corresponding to the V-phase as a reference
signal and corrects the switching signals of the other sensors 41
and 43 will be described. This is for a reason that, among the
sensors 41 to 43, the sensor 42 is the closest to the sensor magnet
34 and is capable of detecting stable signals.
Correction Example 1
[0184] First, with reference to the time chart of FIG. 23, an
example which uses the sensor 42 of the V-phase as a reference and
corrects the switching signal of the sensor 43 of the U-phase will
be described. The switching signals of the sensors 41 to 43 shown
in FIG. 23 are the same as the switching signals of the sensors 41
to 43 shown in FIG. 17. The time chart of FIG. 23 shows electric
angles by the sections each corresponding to 60.degree. for the
sake of convenience.
[0185] As shown by broken lines, the ideal waveform of the
switching signal of the sensor 43 is turned on at the electric
angle 0.degree., continues to be on for the section of an electric
angle 180.degree., and is then switched to off at the timing of the
electric angle 180.degree.. More specifically, the ideal waveform
of the switching signal of the sensor 43 is turned off at the
timing of the electric angle 180.degree. (p1) delayed by a section
of an electric angle 60.degree. from the timing of the electric
angle 120.degree. at which the switching signal of the sensor 42 is
turned on.
[0186] On the other hand, as shown by a solid line, a case in which
the actual waveform of the switching signal of the sensor 43 is
turned on at the timing of the electric angle 30.degree., then
turned on for the section of an electric angle 180.degree., and
then turned off at the timing of an electric angle 210.degree.
(p1') is simulated. More specifically, between the ideal electric
angle 180.degree. and the actual electric angle 210.degree., there
is a phase difference (shifting) corresponding to the section of an
electric angle 30.degree.. This can be expressed by Equation
(3).
The phase difference=p1'-p1 Equation (3)
[0187] The drive apparatus 37 is constantly detecting time
.DELTA.t180 corresponding to the section of the electric angle
180.degree. in the switching signal of the sensor 43. Then, ideal
time .DELTA.t60 corresponding to the section of the ideal electric
angle 60.degree. from the timing at which the sensor 42 is turned
on to the timing at which the sensor 43 is turned off is
calculated. Furthermore, the drive apparatus 37 calculates actual
measurement time .DELTA.treal60 corresponding to the section of the
actual electric angle 90.degree. from the timing at which the
sensor 42 is turned on to the timing at which the sensor 43 is
turned off. Furthermore, the drive apparatus 37 obtains an
adjustment value (correction value) "AdjPhase" of the switching
signal of the sensor 43 from the difference between the ideal time
.DELTA.t60 and the actual measurement time .DELTA.treal60. This
process can be expressed by Equation (4) and Equation (5).
.DELTA.t60=.DELTA.t180.times.0.334 Equation (4)
AdjPhase=.DELTA.t60-.DELTA.treal60 Equation (5)
[0188] Herein, "0.334" is a coefficient of the section of the
electric angle 60.degree. with respect to the section of the
electric angle 180.degree. in which on or off of the switching
signal is continued.
[0189] Then, the drive apparatus 37 carries out a process of
correcting the off-timing of the switching signal of the sensor 43
to the timing of the electric angle 180.degree. (p1), which has
been advanced by the section of the electric angle 30.degree. from
the electric angle 210.degree.. In other words, the section of the
electric angle from the timing at which the switching signal of the
sensor 42 is turned on to the timing at which the switching signal
of the sensor 43 is turned off can be changed to the ideal electric
angle 60.degree..
Correction Example 2
[0190] Next, by reference to the time chart of FIG. 24, an example
which uses the sensor 42 of the V-phase as a reference and corrects
the switching signal of the sensor 41 of the W-phase will be
described. The switching signals of the sensors 41 to 43 shown in
FIG. 24 are the same as the switching signals of the sensors 41 to
43 shown in FIG. 17. The timing chart of FIG. 24 shows electric
angles by the sections each corresponding to 60.degree. for the
sake of convenience. As shown by broken lines, the ideal waveform
of the switching signal of the sensor 41 is turned off at the
electric angle 60.degree., maintains to be off for the section of
an electric angle 180.degree., and is then switched to on at the
electric angle 240.degree.. In other words, the ideal waveform of
the switching signal of the sensor 41 is turned on at the timing of
the electric angle 240.degree. (p1) which is delayed by the section
of an electric angle 120.degree. from the timing of the electric
angle 120.degree. at which the switching signal of the sensor 42 is
turned on.
[0191] On the other hand, as shown by a solid line, a case in which
the actual waveform of the switching signal of the sensor 41 is
turned off at the timing of the electric angle 30.degree., is
turned off for the section of an electric angle 180.degree., and is
then turned on at the timing of the electric angle 210.degree.
(p1') is simulated. More specifically, between the ideal electric
angle 240.degree. and the actual electric angle 210.degree., there
is a phase difference (shifting) corresponding to the section of an
electric angle 30.degree.. This phase difference is expressed by
Equation (6).
The phase difference=p1-p1' Equation (6)
[0192] The drive apparatus 37 is constantly detecting the time
.DELTA.t180 corresponding to the section of the electric angle
180.degree. in the switching signal of the sensor 41. Then, ideal
time .DELTA.t120 corresponding to the section of an ideal electric
angle 120.degree. from the timing at which the sensor 42 is turned
on to the timing at which the sensor 41 is turned on is calculated.
Furthermore, the control circuit 50 calculates actual measurement
time .DELTA.treal120 corresponding to the section of an actual
electric angle 90.degree. from the timing at which the sensor 42 is
turned on to the timing at which the sensor 41 is turned off.
Furthermore, the control circuit 50 obtains an adjustment value
(correction value) "AdjPhase" of the switching signal of the sensor
41 from the difference between the ideal time .DELTA.t120 and the
actual measurement time .DELTA.treal120. This process is expressed
by Equation (7).
AdjPhase=.DELTA.t120-.DELTA.treal120 Equation (7)
[0193] Then, the control circuit 50 turns on the switching signal
of the sensor 43 at the timing of the electric angle 360.degree.
(p2) having an interval of a section of an electric angle
120.degree. from the electric angle 240.degree., which is the
on-timing of the corrected switching signal of the sensor 41. The
section of the electric angle from the timing at which the
switching signal of the sensor 41 is turned on to the timing at
which the switching signal of the sensor 43 is turned on can be
changed to the ideal electric angle 120.degree.. This process is
expressed by Equation (8).
p2=p120+AdjPhase Equation (8)
[0194] This Equation (8) means that it is possible to obtain, by
using the adjustment value (correction value) "AdjPhase", the
timing P2 of the electric angle of the switching signal which is
turned on at the timing having an interval of an electric angle
120.degree. (p120) from the timing of the electric angle
240.degree..
[0195] Note that, if the correction that turns on the switching
signal of the sensor 43 at the timing of the electric angle
330.degree. (p2') having an interval of the section of an electric
angle 120.degree. from the electric angle 210.degree., which is the
before-adjustment off-timing of the switching signal of the sensor
41 is carried out, a phase difference corresponding to the section
of an electric angle 30.degree. from the ideal electric angle
360.degree. is generated.
[0196] Next, the above control method will be comprehensively
described by the flow chart of FIG. 25. If the drive apparatus 37
detects the edge switching timing of any of the sensor among the
sensor 43 of the U-phase, the sensor 42 of the V-phase, and the
sensor of the W-phase (step S1), the drive apparatus 37 executes
the processes of step S2 to step S5.
[0197] The process of step S2 is expressed by Tn-3=Tn-2,
[0198] the process of step 3 is expressed by Tn-2=Tn-1, and
[0199] the process of step S4 is expressed by Tn-1=Tn.
[0200] "Tn" is the latest measurement time corresponding to the
section of the electric angle 60.degree., "Tn-1" is the measurement
time corresponding to the electric angle 60.degree. which is one
time before the latest measurement time, "Tn-2" is the measurement
time corresponding to the electric angle 60.degree. two times
before the latest measurement time, and "Tn-3" is the measurement
time corresponding to the electric angle 60.degree. three times
before the latest measurement time. In other words, step S2 to step
S4 mean to update the measurement time of the one-time-before to
three-time-before electric angles 60.degree.. The drive apparatus
37 acquires the latest measurement time corresponding to the
section of the electric angle 60.degree. in step S5.
[0201] In step S6 subsequent to step S5, the drive apparatus 37
judges whether it is the timing at which the edge of the switching
signal of the sensor 43 of the U-phase is switched or not. If the
drive apparatus 37 judges YES in step S6, the drive apparatus 37
proceeds to step S7. For example, the example in which YES is
judged in step S6 is at the timing of the electric angle
360.degree. of FIG. 22. Then, in step S7, the drive apparatus 37
obtains the time .DELTA.t120 corresponding to the section of the
electric angle 120.degree. from the time .DELTA.t180 corresponding
to the section of the electric angle 180.degree. of the switching
signal of the sensor 43.
[0202] Subsequent to step S7, the drive apparatus 37 executes the
processes of step S8 to step S11, executes the process of step S17,
and terminates a control routine. The processes of step S8 to step
S11 are the processes described by referencing the time chart of
FIG. 23. First, the process of step S8 is the process of obtaining
the ideal time .DELTA.t60 corresponding to the section of the ideal
electric angle 60.degree. from the time .DELTA.t180 corresponding
to the section of the electric angle 180.degree. of the switching
signal of the sensor 43 of the U-phase.
[0203] The process of step S9 is the process of obtaining the
actual measurement time .DELTA.treal60 corresponding to the actual
section of the electric angle 60.degree. from the timing at which
the sensor 42 is turned on to the timing at which the sensor 43 is
turned off.
[0204] The process of step S10 is the process of obtaining the
phase difference (shifting) between the ideal section of the
electric angle 60.degree. and the actual section of the electric
angle 60.degree.. This process is expressed by the phase
difference=.DELTA.t60-.DELTA.60'.
[0205] Herein, .DELTA.t60' has the same meaning as .DELTA.treal60
in Equation (5)
[0206] Meanwhile, in step S11, the process of correcting the
off-timing of the switching signal of the sensor 43 to the timing
of the electric angle 180.degree. (p1), which has been advanced by
the section of the electric angle 30.degree. from the electric
angle 210.degree..
[0207] The process of step S17 selects and executes any of the
first energization control, the weak field control, and the third
energization control by using the switching signal, which serves as
a reference, and the corrected switching signal.
[0208] On the other hand, if the drive apparatus 37 judges NO in
step S6, the drive apparatus 37 judges in step S12 whether it is
the timing at which the switching signal of the sensor 41 is
switched or not. If the drive apparatus 37 judges YES in step S12,
the drive apparatus 37 executes the processes of step S13 to step
S16 and, after step S17, terminates the control routine.
[0209] The processes from step S13 to step S16 are the processes
described by referencing the time chart of FIG. 24. First, the
process of step S13 is the process of obtaining the ideal time
.DELTA.t120 corresponding to the ideal section of the electric
angle 120.degree. from the time .DELTA.t180 corresponding to the
section of the electric angle 180.degree. of the switching signal
of the sensor 41 of the W-phase.
[0210] The process of step S14 is a process of obtaining the time
.DELTA.t120' corresponding to the ideal section of the electric
angle 120.degree. from the timing at which the sensor 42 has been
most recently turned on to the point at which the sensor 43 is
turned on as .DELTA.t120'=Tn-Tn-1.
[0211] The process of step S15 is the process of obtaining the
phase difference (shifting) between the ideal section of the
electric angle 120.degree. and the actual section of the electric
angle 90.degree.. This process is expressed by the following
equation.
The phase difference=.DELTA.t120-.DELTA.t120'.
[0212] Meanwhile, in step S16, the process of correcting the timing
of the switching signal of the sensor 41 to the timing of the
electric angle 240.degree. (p1), which is delayed by the section of
the electric angle 30.degree. from the electric angle 210.degree.,
is carried out.
[0213] As described above, the motor apparatus 17 can correct the
switching signal of the sensors 41 or 43 on the basis of the
switching signal of the sensor 42. Therefore, even if there is an
error in the mutual distances between the sensors 41, 42, and 43
with respect to ideal distances, the first energization control,
the weak field control, or the third energization control can be
appropriately carried out by using the corrected switching signal.
Therefore, in accordance with the conditions such as the movement
position, movement direction, load, mode, etc. of the wiper arm 15,
the rotation number, the torque, etc. of the rotor 27 of the
brushless motor 18 can be obtained. Therefore, efficiency of the
motor apparatus 17 can be improved, noise can be suppressed, and
vibrations can be avoided.
[0214] Furthermore, since the switching signals of the sensors 41,
42, and 43 can be corrected, the sensors 41, 42, and 43 can be
disposed on the same plane of the control board 36. Therefore,
dedicated sensor supporting members for attaching the three sensors
are not required to be provided around the rotor. Therefore, lead
wires, etc. for connecting the three sensors provided at the
dedicated sensor supporting members and the control circuit are not
required to be provided. Therefore, the size and cost of the motor
apparatus 17 can be reduced.
[0215] The drive apparatus 37 described in the above described
second embodiment corresponds to a signal correcting unit and an
element control unit of the present invention. In the first
energization control, the timing of the electric angle 30.degree.
at which the switching element 38a is turned on corresponds to
first timing of the present invention, and the timing of the
electric angle 15.degree. at which the switching element 38a is
turned on in the weak field control or the third energization
control corresponds to second timing of the present invention. The
speed reduction mechanism 19 and the pivot shaft 14 correspond to a
power transmitting mechanism of the present invention. Furthermore,
step S7 to step S11 and step S13 to step S16 correspond to a first
step of the present invention, and step S17 corresponds to a second
step of the present invention.
[0216] The drive apparatus of the present invention is not limited
to that of the second embodiment, and it goes without saying that
various modifications can be made within the range not deviating
from the gist thereof. For example, it is possible to correct the
switching signal from other sensor by using the switching signal of
the sensor of the U-phase, and it is possible to correct the
switching signal from other sensor by using the switching signal of
the sensor of the W-phase. Furthermore, the brushless motor of the
present invention includes the structure of a star connection in
which armature coils are connected in Y shapes. The brushless motor
of the present invention includes one in which the rotor has an IPM
(Interior Permanent Magnet) structure. In the IPM structure,
permanent magnets are buried in the rotor core. Meanwhile, the
first period is not limited to the electric angle 120.degree., but
may be less than the electric angle 120.degree., or may exceed the
electric angle 120.degree..
[0217] The brushless motor of the present invention includes the
inner-rotor-type structure in which the rotor is disposed in the
inner side of the stator and an outer-rotor-type structure in which
the rotor is disposed in the outer side of the stator.
[0218] The wiper apparatus of the present invention includes a
wiper apparatus in which the wiper blade wipes off a rear glass.
Thus, the wind glass of the wiper apparatus of the present
invention includes a windshield and a rear glass. Furthermore, the
wiper apparatus of the present invention includes a configuration
in which two wiper arms are singularly driven by a single brushless
motor.
[0219] The brushless motor of the second embodiment includes, other
than the wiper motor that operates the wiper apparatus, brushless
motors provided for operating action members such as a door, a
roof, a glass, etc. in, for example, a power slide door apparatus,
a sunroof apparatus, or a power window apparatus provided in a
vehicle. Note that the drive apparatus 37 corresponds to a control
unit and a mode switching unit of the present invention.
[0220] The brushless motor, motor apparatus, and control method
according to the present invention can be utilized in wiper
apparatuses, power-slide-door apparatuses, sunroof apparatuses, and
power window apparatuses provided in vehicles.
[0221] While the present disclosure has been illustrated and
described with respect to a particular embodiment thereof, it
should be appreciated by those of ordinary skill in the art that
various modifications to this disclosure may be made without
departing from the spirit and scope of the present disclosure.
* * * * *