U.S. patent application number 10/189039 was filed with the patent office on 2003-01-09 for drive unit for variable displacement electric compressor.
Invention is credited to Odachi, Yasuharu, Sonobe, Masanori.
Application Number | 20030005714 10/189039 |
Document ID | / |
Family ID | 19040309 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030005714 |
Kind Code |
A1 |
Odachi, Yasuharu ; et
al. |
January 9, 2003 |
Drive unit for variable displacement electric compressor
Abstract
A compressor is actuated by a motor and varies the displacement
by the operation of an electromagnetic actuator. A drive unit of
the compressor includes a power source, a motor drive circuit
located on a power supply path between the motor and the power
source, and an actuator drive circuit located on a power supply
path between an electromagnetic actuator and the power source. The
motor drive circuit drives the motor and the actuator drive circuit
drives the electromagnetic actuator. The motor drive circuit and
the actuator drive circuit share a smoothing circuit and a filter
circuit. Therefore, the actuator drive circuit does not require its
own smoothing circuit and a filter circuit. This reduces the number
of parts of the drive unit, thereby reducing the size and the cost
of the drive unit.
Inventors: |
Odachi, Yasuharu;
(Kariya-shi, JP) ; Sonobe, Masanori; (Kariya-shi,
JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
19040309 |
Appl. No.: |
10/189039 |
Filed: |
July 3, 2002 |
Current U.S.
Class: |
62/236 ;
62/228.4 |
Current CPC
Class: |
F04B 2027/1854 20130101;
F04B 27/0895 20130101; F04B 27/1804 20130101 |
Class at
Publication: |
62/236 ;
62/228.4 |
International
Class: |
F25B 001/00; F25B
049/00; F25B 027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 4, 2001 |
JP |
2001-203726 |
Claims
1. A drive unit of a compressor that is actuated by a motor to
compress gas and varies the displacement by the operation of an
electromagnetic actuator, the drive unit comprising: a power
source; a motor drive circuit located on a power supply path
between the motor and the power source, wherein the motor drive
circuit drives the motor in accordance with an external command
signal; and an actuator drive circuit located on a power supply
path between the electromagnetic actuator and the power source,
wherein the actuator drive circuit drives the electromagnetic
actuator in accordance with an external command signal, and wherein
one of the drive circuits includes an electric element, which
electrically affects the other drive circuit.
2. The drive unit according to claim 1, wherein one of the drive
circuits has an output terminal, wherein the other drive circuit
has an input terminal, and wherein the output terminal is connected
to the input terminal.
3. The drive unit according to claim 1, wherein the electric
element forms a smoothing circuit for stabilizing the applied
voltage from the power source.
4. The drive unit according to claim 3, wherein the drive circuits
share the smoothing circuit.
5. The drive unit according to claim 1, wherein the electric
element forms a filter circuit for filtering noise from the power
source.
6. The drive unit according to claim 5, wherein the drive circuits
share the filter circuit.
7. The drive unit according to claim 1, wherein the power source is
a direct-current power source, which has a high potential terminal
and a low potential terminal, and the actuator drive circuit
includes a switching element, which has a first terminal and a
second terminal, wherein the electromagnetic actuator includes a
coil, which has a first terminal and a second terminal, wherein the
first terminal of the switching element is connected to the high
potential terminal of the direct-current power source, and the
first terminal of the coil is connected to the low potential
terminal of the direct-current power source, and wherein the second
terminal of the switching element is connected to the second
terminal of the coil.
8. The drive unit according to claim 7, wherein a shunt resistor is
arranged between the low potential terminal of the direct-current
power source and the first terminal of the coil, and wherein the
shunt resistor is used for detecting the value of the current
flowing through the coil.
9. The drive unit according to claim 1, wherein the power source is
a direct-current power source, which has a high potential terminal
and a low potential terminal, and the actuator drive circuit
includes a switching element, which has a first terminal and a
second terminal, wherein the electromagnetic actuator includes a
coil, which has a first terminal and a second terminal, wherein the
first terminal of the switching element is connected to the low
potential terminal of the direct-current power source, and the
first terminal of the coil is connected to the high potential
terminal of the direct-current power source, and wherein the second
terminal of the switching element is connected to the second
terminal of the coil.
10. The drive unit according to claim 9, wherein the motor is an AC
motor, and the motor drive circuit includes a plurality of phase
inverter circuits, wherein each phase inverter circuit includes a
high-side switching element, which has a first terminal and a
second terminal, and a low-side switching element, which has a
first terminal and a second terminal, wherein the first terminal of
the high-side switching element is connected to the high potential
terminal of the direct-current power source, and the first terminal
of the low-side switching element is connected to the low potential
terminal of the direct-current power source, wherein the second
terminal of the high-side switching element and the second terminal
of the low-side switching element are connected to the AC motor via
a common AC output terminal, and wherein the low-side switching
element and the switching element of the actuator drive circuit are
driven by a common drive source.
11. The drive unit according to claim 1, wherein the motor is a DC
motor.
12. The drive unit according to claim 11, wherein a power line
extending from the motor drive circuit to the motor and a power
line extending from the actuator drive circuit to the
electromagnetic actuator are partially shared.
13. The drive unit according to claim 1, wherein the compressor
includes a control chamber and a control valve, wherein the control
valve has the electromagnetic actuator, and the opening degree of
the control valve is adjusted by the electromagnetic actuator to
change the pressure in the control chamber, and wherein the
displacement of the compressor is varied in accordance with the
pressure in the control chamber.
14. The drive unit according to claim 1, wherein the compressor is
incorporated in an air-conditioner of a vehicle, and wherein the
compressor is actuated by selectively using the engine of the
vehicle and the motor.
15. A drive unit of a compressor that is actuated by a motor to
compress gas, wherein the compressor includes a control chamber and
a control valve, wherein the control valve has an electromagnetic
actuator, and the opening degree of the control valve is adjusted
by the electromagnetic actuator to change the pressure in the
control chamber, and wherein the displacement of the compressor is
varied in accordance with the pressure in the control chamber, the
drive unit comprising: a power source; a motor drive circuit
located on a power supply path between the motor and the power
source to drive the motor; an actuator drive circuit located on a
power supply path between the electromagnetic actuator and the
power source to drive the electromagnetic actuator; a command
device, which sends a command signal to each of the drive circuits
to control the drive circuits; and a single smoothing circuit for
stabilizing the voltage applied to the motor drive circuit from the
power source and the voltage applied to the actuator drive circuit
from the power source.
16. The drive unit according to claim 15, further comprising a
single filter circuit, wherein the filter circuit filters noise
from the power source to the motor drive circuit and noise from the
power source to the actuator drive circuit.
17. The drive unit according to claim 15, wherein the power source
is a direct-current power source, which has a high potential
terminal and a low potential terminal, and the actuator drive
circuit includes a switching element, which has a first terminal
and a second terminal, wherein the electromagnetic actuator
includes a coil, which has a first terminal and a second terminal,
wherein the first terminal of the switching element is connected to
the high potential terminal of the direct-current power source, and
the first terminal of the coil is connected to the low potential
terminal of the direct-current power source, and wherein the second
terminal of the switching element is connected to the second
terminal of the coil.
18. The drive unit according to claim 17, wherein a shunt resistor
is arranged between the low potential terminal of the
direct-current power source and the first terminal of the coil, and
wherein the shunt resistor is used for detecting the value of the
current flowing through the coil.
19. The drive unit according to claim 15, wherein the power source
is a direct-current power source, which has a high potential
terminal and a low potential terminal, and the actuator drive
circuit includes a switching element, which has a first terminal
and a second terminal, wherein the electromagnetic actuator
includes a coil, which has a first terminal and a second terminal,
wherein the first terminal of the switching element is connected to
the low potential terminal of the direct-current power source, and
the first terminal of the coil is connected to the high potential
terminal of the direct-current power source, and wherein the second
terminal of the switching element is connected to the second
terminal of the coil.
20. The drive unit according to claim 19, wherein the motor is an
AC motor, and the motor drive circuit includes a plurality of phase
inverter circuits, wherein each phase inverter circuit includes a
high-side switching element, which has a first terminal and a
second terminal, and a low-side switching element, which has a
first terminal and a second terminal, wherein the first terminal of
the high-side switching element is connected to the high potential
terminal of the direct-current power source, and the first terminal
of the low-side switching element is connected to the low potential
terminal of the direct-current power source, wherein the second
terminal of the high-side switching element and the second terminal
of the low-side switching element are connected to the AC motor via
a common AC output terminal, and wherein the low-side switching
element and the switching element of the actuator drive circuit are
driven by a common drive source.
21. The drive unit according to claim 15, wherein the motor is a DC
motor, and wherein a power line extending from the motor drive
circuit to the motor and a power line extending from the actuator
drive circuit to the electromagnetic actuator are partially shared.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a drive unit for a variable
displacement electric compressor, which can vary the displacement
using an electromagnetic actuator. More specifically, the present
invention pertains to a drive unit for driving a motor and an
electromagnetic actuator based on a command signal sent from a
command device.
[0002] A typical drive unit includes a system for controlling a
variable displacement electric compressor (hereinafter, simply
referred to as a compressor) used for a vehicular air-conditioner.
The system includes, for example, an electronic control unit (ECU),
a motor drive circuit (such as an inverter), and a valve drive
circuit (such as PWM circuit) for driving an electromagnetic valve.
The ECU is a computer that controls the air-conditioner. The motor
drive circuit is arranged on a power supply path between a
vehicular battery and the motor. The valve drive circuit is
arranged on a power supply path between the vehicular battery and
the electromagnetic valve.
[0003] The ECU determines that the compressor needs to be activated
or stopped in accordance with whether there is a need for
air-conditioning and then commands the motor drive circuit. The
motor drive circuit supplies or stops supplying power to the motor
in accordance with the command sent from the ECU. Accordingly, the
compressor is activated or stopped. The ECU determines the duty
ratio in accordance with the information such as the in-car
temperature and a target temperature. The ECU then commands the
valve drive circuit to drive the electromagnetic valve with the
determined duty ratio. The valve drive circuit drives the
electromagnetic valve with the duty ratio commanded by the ECU to
control the opening degree of the electromagnetic valve, or the
displacement of the compressor.
[0004] However, the motor drive circuit and the valve drive circuit
are separate circuits. Therefore, electric elements forming each
circuit are exclusively used. That is, an electric element forming
a filter circuit to filter noise from the power source and an
electric element forming a smoothing circuit for stabilizing
direct-current voltage applied to each circuit are exclusively
provided for each drive circuit. This increases the size and the
cost of the control system for compressor.
SUMMARY OF THE INVENTION
[0005] Accordingly, it is an objective of the present invention to
provide a drive unit for a variable displacement electric
compressor in which electric elements are shared between a motor
drive circuit and an actuator drive circuit for driving an
electromagnetic actuator.
[0006] To achieve the above objective, the present invention
provides a drive unit of a compressor that is actuated by a motor
to compress gas and varies the displacement by the operation of an
electromagnetic actuator. The drive unit includes a power source, a
motor drive circuit, and an actuator drive circuit. The motor drive
circuit is located on a power supply path between the motor and the
power source. The motor drive circuit drives the motor in
accordance with an external command signal. The actuator drive
circuit is located on a power supply path between the
electromagnetic actuator and the power source. The actuator drive
circuit drives the electromagnetic actuator in accordance with an
external command signal. One of the drive circuits includes an
electric element, which electrically affects the other drive
circuit.
[0007] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0009] FIG. 1 is a cross-sectional view illustrating a swash plate
type variable displacement electric compressor according to a first
embodiment of the present invention;
[0010] FIG. 2 is a cross-sectional view illustrating the control
valve located in the compressor shown in FIG. 1;
[0011] FIG. 3 is a block circuit diagram illustrating a system for
controlling the compressor shown in FIG. 1:
[0012] FIG. 4 is a block circuit diagram illustrating a control
system according to a second embodiment of the present invention:
and
[0013] FIG. 5 is a block circuit diagram illustrating a control
system according to a third embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] A first embodiment of the present invention will now be
described with reference to FIGS. 1 to 3.
[0015] As shown in FIG. 1, a swash plate type variable displacement
electric compressor (hereinafter, simply referred to as a
compressor) has a housing assembly 11. The housing assembly 11
defines a control chamber, which is a crank chamber 12 in the first
embodiment. A drive shaft 13 is rotatably supported by the housing
assembly 11 and extends through the crank chamber 12. The drive
shaft 13 is coupled to a drive source, which is an engine E in the
first embodiment, by a power transmission mechanism PT. The engine
E may be, and not limited to, an internal combustion engine
including a gasoline engine.
[0016] The power transmission mechanism PT includes a pulley 80,
which is rotatably supported by the housing assembly 11, and a belt
81, which couples the pulley 80 to the engine E. A hub 82 is
secured to the end portion of the drive shaft 13 that projects
outside the housing assembly 11. A conventional one-way clutch 83
is arranged between the pulley 80 and the hub 82.
[0017] An AC motor 84 is arranged inside the hub 82. The motor 84
includes a stator 84a, which is secured to the housing assembly 11,
and a rotor 84b, which is secured to the hub 82 to surround the
outer circumference of the stator 84a. For example, when the engine
E is stopped, the motor 84 generates a rotational force on the
rotor 84b by the electromagnetic induction generated by the power
supply to the stator 84a. This rotates the drive shaft 13 via the
hub 82.
[0018] At this time, the one-way clutch 83 prevents power from
being transmitted from the hub 82 to the pulley 80. Therefore, the
rotational force generated by the motor 84 is prevented from being
transmitted to the engine E. The one-way clutch 83 permits power
transmission from the pulley 80 to the hub 82. Therefore, the power
of the engine E is transmitted to the drive shaft 13 via the pulley
80 and the hub 82.
[0019] A lug plate 14 is fixed to the drive shaft 13 in the crank
chamber 12 to rotate integrally with the drive shaft 13. A swash
plate 15 is accommodated in the crank chamber 12. The swash plate
15 slides along and inclines with respect to the drive shaft
13.
[0020] A hinge mechanism 16 is arranged between the lug plate 14
and the swash plate 15. Therefore, the swash plate 15 rotates
integrally with the lug plate 14 and the drive shaft 13 and
inclines with respect to the drive shaft 13.
[0021] The housing assembly 11 has cylinder bores 11a (only one is
shown). Each cylinder bore 11a accommodates a single-headed piston
17. Each piston 17 reciprocates inside the corresponding cylinder
bore 11a. Each piston 17 is coupled to the peripheral portion of
the swash plate 15 by a pair of shoes 18. Accordingly, the shoes 18
convert the rotation of the swash plate 15, which rotates with the
drive shaft 13, to reciprocation of the pistons 17.
[0022] The housing assembly 11 includes a valve plate assembly 19,
which closes the openings of the cylinder bores 11a on one end. The
valve plate assembly 19 has suction ports 23, suction valve flaps
24, discharge ports 25 and discharge valve flaps 26. Each set of
the suction port 23, the suction valve flap 24, the discharge port
25 and the discharge valve flap 26 corresponds to one of the
cylinder bores 11a. A compression chamber 20 is defined in each
cylinder bore 11a by the associated piston 17 and the valve plate
assembly 19. The housing assembly 11 defines a suction chamber 21
and a discharge chamber 22 opposite to the cylinder bores 11a with
the valve plate assembly 19 arranged in between.
[0023] As each piston 17 moves from the top dead center to the
bottom dead center, refrigerant gas in the suction chamber 21 is
drawn into the corresponding compression chamber 20 through the
corresponding suction port 23 while flexing the suction valve flap
24 to an open position. Refrigerant gas that is drawn into the
compression chamber 20 is compressed to a predetermined pressure as
the piston 17 is moved from the bottom dead center to the top dead
center. Then, the gas is discharged to the discharge chamber 22
through the corresponding discharge port 25 while flexing the
discharge valve flap 26 to an open position.
[0024] As shown in FIG. 1, a bleed passage 27 and a supply passage
28 are formed in the housing assembly 11. The bleed passage 27
connects the crank chamber 12 with the suction chamber 21. The
supply passage 28 connects the crank chamber 12 with the discharge
chamber 22. The supply passage 28 is regulated by the control valve
CV.
[0025] The opening of the control valve CV is adjusted to control
the balance of the flow rate of highly pressurized gas supplied to
the crank chamber 12 through the supply passage 28 and the flow
rate of gas conducted out from the crank chamber 12 through the
bleed passage 27. The pressure in the crank chamber 12 is thus
adjusted. As the pressure in the crank chamber 12 varies, the
inclination angle of the swash plate 15 is changed. Accordingly,
the stroke of each piston 17, or the compressor displacement, is
varied.
[0026] For example, a decrease in the pressure in the crank chamber
12 increases the inclination angle of the swash plate 15, which
increases the displacement of the compressor. On the contrary, an
increase in the pressure in the crank chamber 12 decreases the
inclination angle of the swash plate 15, which decreases the
displacement of the compressor.
[0027] As shown in FIG. 1, the refrigerant circuit of the vehicular
air-conditioner includes the compressor and an external refrigerant
circuit 30, which is connected to the compressor. The external
refrigerant circuit 30 includes a condenser 31, an expansion valve
32, and an evaporator 33.
[0028] A first pressure monitoring point PI is located inside the
discharge chamber 22. A second pressure monitoring point P2 is
located in the refrigerant passage at a part that is spaced away
from the first pressure monitoring point P1 toward the condenser 31
by a predetermined distance. The first pressure monitoring point PI
is connected to the control valve CV through a first pressure
introduction passage 35. As shown in FIG. 2, the second pressure
monitoring point P2 is connected to the control valve CV through a
second pressure introduction passage 36.
[0029] As shown in FIG. 2, the control valve CV has a valve housing
41. A valve chamber 42, a communication passage 43, and a pressure
sensing chamber 44 are defined in the valve housing 41. A
transmission rod 45 extends through the valve chamber 42 and the
communication passage 43. The transmission rod 45 moves in the
axial direction, or in the vertical direction as viewed in FIG.
2.
[0030] The communication passage 43 is disconnected from the
pressure sensing chamber 44 by the upper portion of the
transmission rod 45, which is fitted in the communication passage
43. The valve chamber 42 is connected to the discharge chamber 22
through an upstream section of the supply passage 28. The
communication passage 43 is connected to the crank chamber 12
through a downstream section of the supply passage 28. The valve
chamber 42 and the communication passage 43 form a part of the
supply passage 28.
[0031] A valve body 46 is formed in the middle portion of the
transmission rod 45 and is located in the valve chamber 42. A step
defined between the valve chamber 42 and the communication passage
43 functions as a valve seat 47. The communication passage 43
serves as a valve hole. The transmission rod 45 shown in FIG. 2 is
located at the lowermost position where the opening degree of the
valve hole 43 is the greatest. When the transmission rod 45 is
moved from the lowermost position to the uppermost position, at
which the valve body 46 contacts the valve seat 47, the
communication passage 43 is disconnected from the valve chamber 42.
The opening degree of the valve hole 43, or the opening degree of
the supply passage 28, is controlled in accordance with the axial
position of the transmission rod 45.
[0032] A pressure sensing member, which is a bellows 48 in the
first embodiment, is located in the pressure sensing chamber 44.
The upper end of the bellows 48 is fixed to the valve housing 41.
The lower end of the bellows 48 receives the upper end of the
transmission rod 45. The bellows 48 divides the pressure sensing
chamber 44 into a first pressure chamber 49, which is the interior
of the bellows 48, and a second pressure chamber 50, which is the
exterior of the bellows 48. The first pressure chamber 49 is
connected to the first pressure monitoring point P1 through a first
pressure introduction passage 35. The second pressure chamber 50 is
connected to the second pressure monitoring point P2 through a
second pressure introduction passage 36. Therefore, the first
pressure chamber 49 is exposed to the pressure PdH monitored at the
first pressure monitoring point P1, and the second pressure chamber
50 is exposed to the pressure PdL monitored at the second pressure
monitoring point P2.
[0033] An electromagnetic actuator 51 is coupled to the lower
portion of the valve housing 41. The electromagnetic actuator 51
includes a cup-shaped cylinder 52, which is arranged coaxial to the
valve housing 41. A stationary iron core 53 is fitted in the upper
opening of the cylinder 52 and is secured to the cylinder 52. The
stationary core 53 defines a plunger chamber 54 at the lowermost
portion in the cylinder 52.
[0034] A movable iron core 56 is located in the plunger chamber 54.
The movable iron core 56 slides along the plunger chamber 54 in the
axial direction. An axial guide hole 57 is formed in the center of
the stationary iron core 53. The transmission rod 45 is inserted in
the guide hole 57. The lower end of the transmission rod 45
contacts the top surface of the movable iron core 56 inside the
plunger chamber 54.
[0035] The plunger chamber 54 accommodates a spring 60. The spring
60 urges the plunger 56 toward the transmission rod 45. The
transmission rod 45 is urged toward the movable iron core 56 by the
force of the bellows 48. Therefore, the plunger 56 always moves up
and down integrally with the transmission rod 45.
[0036] A coil 61 is located about the stationary iron core 53 and
the movable iron core 56. The coil 61 generates an electromagnetic
force (electromagnetic attracting force), the magnitude of which
depends on the value of the supplied current, between the movable
iron core 56 and the stationary iron core 53. The electromagnetic
force is transmitted to the transmission rod 45 via the movable
iron core 56.
[0037] The position of the transmission rod 45 (the valve body 46),
or the valve opening of the control valve CV, is controlled in the
following manner.
[0038] As shown in FIG. 2, when the coil 61 is supplied with no
electric current (duty ratio=0%), the position of the transmission
rod 45 is dominantly determined by the downward force of the
bellows 48. Thus, the transmission rod 45 is placed at its
lowermost position, and the communication passage 43 is fully
opened. The difference between the pressure in the crank chamber 12
and the pressure in the compression chambers 20 thus becomes great.
As a result, the inclination angle of the swash plate 15 is
minimized, and the discharge displacement of the compressor is also
minimized.
[0039] When a current of the minimum duty ratio, which is greater
than 0%, is supplied to the coil 61 of the control valve CV, the
upward electromagnetic force surpasses the downward forces of the
bellows 48, which moves the transmission rod 45 upward. In this
state, the resultant of the upward electromagnetic force and upward
force of the spring 60 act against the resultant of the force based
on the pressure difference .DELTA.Pd (Pd=PdH-PdL) and the downward
forces of the bellows 48. The position of the valve body 46 of the
transmission rod 45 relative to the valve seat 47 is determined
such that upward and downward forces are balanced.
[0040] For example, if the flow rate of the refrigerant in the
refrigerant circuit is decreased due to a decrease in speed of the
engine E, the downward force based on the pressure difference
.DELTA.Pd decreases, and the electromagnetic force cannot balance
the forces acting on the transmission rod 45. Therefore, the
transmission rod 45 (the valve body 46) moves upward. This
decreases the opening degree of the communication passage 43 and
thus lowers the pressure in the crank chamber 12. Accordingly, the
inclination angle of the swash plate 15 is increased, and the
displacement of the compressor is increased. The increase in the
displacement of the compressor increases the flow rate of the
refrigerant in the refrigerant circuit, which increases the
pressure difference .DELTA.Pd.
[0041] In contrast, when the flow rate of the refrigerant in the
refrigerant circuit is increased due to an increase in the speed of
the engine E, the downward force based on the pressure difference
.DELTA.Pd increases and the current electromagnetic force cannot
balance the forces acting on the transmission rod 45. Therefore,
the transmission rod 45 (the valve body 46) moves downward and
increases the opening degree of the communication passage 43. This
increases the pressure in the crank chamber 12. Accordingly, the
inclination angle of the swash plate 15 is decreased, and the
displacement of the compressor is also decreased. The decrease in
the displacement of the compressor decreases the flow rate of the
refrigerant in the refrigerant circuit, which decreases the
pressure difference .DELTA.Pd.
[0042] When the duty ratio of the electric current supplied to the
coil 61 is increased to increase the electromagnetic force, the
pressure difference .DELTA.Pd cannot balance the forces acting on
the transmission rod 45. Therefore, the transmission rod 45 (the
valve body 46) moves upward and decreases the opening degree of the
communication passage 43. As a result, the displacement of the
compressor is increased. Accordingly, the flow rate of the
refrigerant in the refrigerant circuit is increased and the
pressure difference .DELTA.Pd is increased.
[0043] When the duty ratio of the electric current supplied to the
coil 61 is decreased and the electromagnetic force is decreased
accordingly, the pressure difference .DELTA.Pd cannot balance the
forces acting on the transmission rod 45. Therefore, the
transmission rod 45 (the valve body 46) moves downward, which
increases the opening degree of the communication passage 43.
Accordingly, the compressor displacement is decreased. As a result,
the flow rate of the refrigerant in the refrigerant circuit is
decreased, and the pressure difference .DELTA.Pd is decreased.
[0044] As described above, the target value of the pressure
difference .DELTA.Pd (target pressure difference) is determined by
the duty ratio of current supplied to the coil 61. The control
valve CV automatically determines the position of the transmission
rod 45 (the valve body 46) according to changes of the pressure
difference .DELTA.Pd to maintain the target pressure difference
.DELTA.Pd. The target pressure difference .DELTA.Pd is externally
controlled by adjusting the duty ratio of current supplied to the
coil 61.
[0045] As shown in FIG. 3, a system for controlling the compressor
includes a controller, which is an electronic control unit (ECU) 65
in the first embodiment, a detection apparatus 79, and a drive unit
66. The ECU 65 is a computer that has a CPU, a ROM, a RAM, and an
I/O.
[0046] The drive unit 66 includes a controller 67, a motor drive
circuit, which is an inverter circuit 68 in the first embodiment,
and an actuator drive circuit for driving an electromagnetic
actuator, which is a pulse width modulation (PWM) circuit 69 in the
first embodiment. The controller 67 is connected to the ECU 65 via,
for example, a LAN in a vehicle. The inverter circuit 68 is
arranged on a power supply path between a direct-current power
source, which is a battery Bt in the first embodiment, and a stator
84a of the motor 84. The PWM circuit 69 is arranged on a power
supply passage between the battery Bt and a coil 61 of the control
valve CV. The inverter circuit 68 and the PWM circuit 69 are
located on the same substrate. The inverter circuit 68, the PWM
circuit 69, and the controller 67 are accommodated in the case (not
shown) and form a single circuit unit.
[0047] The inverter circuit 68 includes phase inverter circuits 68a
(three phase inverter circuits 68a are arranged in the first
embodiment). Each phase inverter circuit 68a includes a high-side
switching element (an IGBT is used in the first embodiment) 70 and
a low-side switching element (an IGBT is used in the first
embodiment) 71. Each high-side switching element 70 includes a
control terminal (gate terminal), which is connected to the
controller 67, and first and second terminals. Similarly, each
low-side switching element 71 includes a control terminal (gate
terminal), which is connected to the controller 67, and first and
second terminals. The first terminal (collector terminal) of each
high-side switching element 70 is connected to the high potential
terminal of the battery Bt. The first terminal (emitter terminal)
of the low-side switching element 71 is connected to the low
potential terminal of the battery Bt. The second terminal (emitter
terminal) of the high-side switching element 70 and the second
terminal (collector terminal) of the low-side switching element 71
are connected to a common AC output terminal 68b. The AC output
terminal 68b of each phase inverter circuit 68a is connected to one
of winding wires of the stator 84a of the motor 84. A flywheel
diode 72 is connected between the first terminal and the second
terminal of each of the switching elements 70, 71.
[0048] The inverter circuit 68 includes a smoothing circuit
(smoothing capacitor) 73 and a filter circuit 74. The smoothing
circuit 73 stabilizes the voltage of the battery BT applied to the
inverter circuit 68. The filter circuit 74 includes an LC circuit,
which has a coil 74a and a capacitor 74b. The filter circuit 74
filters noise that enters the inverter circuit 68 from the battery
Bt.
[0049] The PWM circuit 69 includes a switching element (an IGBT is
used in the first embodiment) 75 and a flywheel diode 76. The
switching element 75 includes a control terminal (gate terminal),
which is connected to the controller 67, a first terminal (emitter
terminal), which is connected to the high potential terminal of the
battery Bt, and a second terminal (collector terminal), which is
connected to a cathode of the flywheel diode 76. An anode of the
flywheel diode 76 is connected to the low potential terminal of the
battery Bt. The coil 61 of the control valve CV includes a first
terminal, which is connected to the low potential terminal of the
battery Bt via a shunt resistor 77, and a second terminal, which is
connected to the second terminal of the switching element 75 and
the cathode of the flywheel diode 76. The controller 67 detects the
current value that flows through the coil 61 with the shunt
resistor 77.
[0050] In the drive unit 66, the electric elements that form the
inverter circuit 68 electrically affect the PWM circuit 69. That
is, a battery voltage input terminal of the PWM circuit 69, or the
first terminal of the switching element 75, is connected to a
battery voltage output terminal (a connecting point SP shown in
FIG. 3) of the inverter circuit 68. Therefore, the smoothing
circuit 73 of the inverter circuit 68 also stabilizes the battery
voltage applied to the PWM circuit 69. The filter circuit 74 of the
inverter circuit 68 also filters noise from the battery Bt to the
PWM circuit 69. Thus, the PWM circuit 69 does not have its own
smoothing circuit and a filter circuit but shares the smoothing
circuit 73 and the filter circuit 74 with the inverter circuit
68.
[0051] The ECU 65 determines the target pressure difference in
accordance with the information (on-off state of the air
conditioner, the in-car temperature, and a target temperature) from
the detection apparatus 79 and sends the target pressure difference
to the controller 67 of the drive unit 66. The controller 67
calculates the current value that corresponds to the target
pressure difference received from the ECU 65. The controller 67
then controls the duty ratio to the switching element 75 of the PWM
circuit 69 such that the current value from the shunt resistor 77
is equivalent to the calculated current value.
[0052] The ECU 65 drives an air-conditioning control actuator unit
86, which includes actuators other than the control valve CV. The
actuator unit 86 includes, for example, a servo motor, which
actuates the inside/outside air switching door, a blower motor, a
servo motor for actuating an air-mix door. The control valve CV, or
the displacement of the compressor is controlled regardless of
whether the compressor is actuated by the engine E or the motor 84.
That is, even when the compressor is actuated by the motor 84, the
cooling performance of the air-conditioner is changed by
controlling the displacement of the compressor and not by adjusting
the rotational speed of the motor 84.
[0053] If it is determined that the compressor needs to be operated
based on the information from the detection apparatus 79 when the
engine E is stopped, the ECU 65 sends a command signal to the
controller 67 of the drive unit 66 to operate the motor 84. At the
receipt of the command signal, the controller 67 switches on the
low-side switching elements 71 each phased by 120 degrees by
intermittently controlling the switching elements 70, 71 of the
inverter circuit 68. The controller 67 then forms a pseudo
three-phase AC voltage by controlling the duty ratio to the high
side switching elements 70 to apply the voltage to the motor 84.
This rotates the motor 84 thereby activating the compressor. Thus,
the air in the passenger compartment can be conditioned even when
the engine E is stopped. The controller 67 commands the inverter
circuit 68 to rotate the motor 84 approximately at a constant
speed.
[0054] The present invention provides the following advantages.
[0055] The smoothing circuit 73 and the filter circuit 74, which
form a part of the inverter circuit 68, operate also for the PWM
circuit 69. Therefore, as mentioned above, instead of having its
own smoothing circuit and a filter circuit, the PWM circuit 69 can
share the electric elements, which form the smoothing circuit 73
and the filter circuit 74, with the inverter circuit 68. This
reduces the number of parts required for the drive unit 66, which
in turn reduces the size and the cost of the drive unit 66.
[0056] In the prior art, the smoothing circuit and the filter
circuit withstand several hundred watts and the smoothing circuit
and the filter circuit used in the valve drive circuit withstand
several ten watts. Therefore, when the smoothing circuit 73 and the
filter circuit 74 are shared between the inverter circuit 68 and
the PWM circuit 69 as in the first embodiment of the present
invention, it is not required to change the capacity of the
smoothing circuit and the filter circuit, which are used in the
prior art motor drive circuit. Therefore, the smoothing circuit and
the filter circuit that are used in the prior art motor drive
circuit can be used without change. Therefore, there is no increase
in the cost due to modification of the capacity of the smoothing
circuit and the filter circuit. That is, the present invention is
particularly effective for an apparatus that has a motor drive
circuit and a valve drive circuit for driving an electromagnetic
valve.
[0057] The switching element 75 of the PWM circuit 69 has the first
terminal, which is connected to the high potential terminal of the
battery Bt, and the second terminal, which is connected to the
second terminal of the coil 61 of the control valve CV. The first
terminal of the coil 61 is connected to the low potential terminal
of the battery Bt via the shunt resistor 77. Arranging the shunt
resistor 77 between the first terminal of the coil 61 and the low
potential terminal of the battery Bt allows detecting the value of
the current flowing through the coil 61. That is, the value of the
current flowing through the coil 61 can be detected using the shunt
resistor 77, which is inexpensive. Thus, the cost of the drive unit
66 is further reduced.
[0058] A second embodiment of the present invention will now be
described with reference to FIG. 4. The differences from the first
embodiment shown in FIGS. 1 to 3 will mainly be discussed
below.
[0059] As shown in FIG. 4, the PWM circuit 69 according to the
second embodiment includes a first terminal (emitter terminal),
which is connected to the low potential terminal of the battery Bt,
and a second terminal (collector terminal), which is connected to
the anode of the flywheel diode 76. The cathode of the flywheel
diode 76 is connected to the high potential terminal of the battery
Bt. The coil 61 of the control valve CV has a first terminal, which
is connected to the high potential terminal of the battery Bt, and
a second terminal, which is connected to the second terminal of the
switching element 75 and the anode of the flywheel diode 76.
[0060] Therefore, the emitter potential of the switching element 75
of the PWM circuit 69 becomes equivalent to the ground level. The
emitter potential of the low-side switching elements 71 of the
inverter circuit 68 also becomes equivalent to the ground level.
The controller 67 has a gate drive source 67a, which is connected
to the control terminal (gate terminal) of each of the switching
element 75 and the low-side switching elements 71. That is, the
switching element 75 of the PWM circuit 69 and the low-side
switching elements 71 of the inverter circuit 68 are driven by the
common gate drive source 67a.
[0061] The controller 67 has gate drive sources 67b each of which
corresponds to one of the high-side switching elements 70 of the
inverter circuit 68. The emitter potential of each high-side
switching element 70 fluctuates in accordance with the on-off state
of the corresponding low-side switching element 71 in the same
phase inverter circuit 68a. Therefore, it is difficult to share the
gate drive source 67a among all the high-side switching elements
70. Also, the shunt resistor 77 is eliminated in the second
embodiment and a hall element, which is not shown, is used instead
to detect the value of the current flowing through the coil 61.
[0062] In the second embodiment, the same advantages as the first
embodiment shown in FIGS. 1 to 3 are provided. Particularly, in the
second embodiment, the switching element 75 of the PWM circuit 69
and the low-side switching elements 71 of the inverter circuit 68
are connected to the common gate drive source 67a. This simplifies
the structure of the controller 67 and further reduces the cost of
the drive unit 66.
[0063] A third embodiment of the present invention will now be
described with reference to FIG. 5. The differences from the first
embodiment shown in FIGS. 1 to 3 will mainly be discussed.
[0064] As shown in FIG. 5, in the third embodiment, a stepping
motor (DC motor) is used for the motor 84 instead of the AC motor.
A motor drive circuit 91 includes switching circuits 91a, the
number of which corresponds to the number of phases of the motor 84
(three switching circuits 91a are arranged in the third
embodiment). Each switching circuit 91a includes a switching
element (an IGBT is used in the third embodiment) 93 and a flywheel
diode 92. Each switching element 93 includes a first terminal
(collector terminal), which is connected to the low potential
terminal of the battery Bt, and a second terminal (emitter
terminal), which is connected to the anode of the corresponding
flywheel diode 92. The cathode of each flywheel diode 92 is
connected to the high potential terminal of the battery Bt. In each
switching circuit 91a, the second terminal of the switching element
93 and the anode of the flywheel diode 92 are connected to one of
winding wires of the stator 84a of the motor 84.
[0065] The structure of the PWM circuit 69 is the same as that of
the second embodiment shown in FIG. 4. The first terminal of the
coil 61 of the control valve CV is connected to the high potential
terminal of the battery Bt via a power line 95. A common terminal
(neutral point) of three winding wires of the stator 84a is
connected to the power line 95 via a power line 96. That is, the
neutral point of the winding wires of the stator 84a is connected
to the high potential terminal of the battery Bt via the power
lines 96, 95. Therefore, the motor 84 and the control valve CV are
connected to the drive unit 66 via the common power line 95.
[0066] In the third embodiment, the same advantages as the first
embodiment shown in FIGS. 1 to 3 are also provided. Particularly,
in the third embodiment, the DC motor is used for the motor 84.
Therefore, the structure of the motor drive circuit 91 and the
controller 67 is simplified. Also, using the DC motor for the motor
84 allows the motor 84 and the control valve CV to be connected to
the drive unit 66 via the common power line 95. This simplifies the
wiring.
[0067] It should be apparent to those skilled in the art that the
present invention may be embodied in many other specific forms
without departing from the spirit or scope of the invention.
Particularly, it should be understood that the invention may be
embodied in the following forms.
[0068] The ECU 65 may serve as the controller 67 instead of the
controller 67.
[0069] The switching elements 70, 71, 75, 93 may not be the IGBT.
The switching elements 70, 71, 75, 93 may be switching elements
such as power MOS-FET.
[0070] The first pressure monitoring point P1 may be located in the
suction pressure zone (low pressure zone), and the second pressure
monitoring point P2 may be located at a part downstream of the
first pressure monitoring point P1 in the suction pressure zone.
The low pressure zone includes the evaporator 33, the suction
chamber 21, and the refrigerant passage between the evaporator 33
and the suction chamber 21.
[0071] The first pressure monitoring point P1 may be located in the
discharge pressure zone (high pressure zone), and the second
pressure monitoring point P2 may be located in the low pressure
zone. The high pressure zone includes the discharge chamber 22, the
condenser 31, and the refrigerant passage between the discharge
chamber 22 and the condenser 31.
[0072] The first pressure monitoring point P1 may be located in the
high pressure zone, and the second pressure monitoring point P2 may
be located in the crank chamber 12. Alternately, the second
pressure monitoring point P2 may be located in the crank chamber
12, and the first pressure monitoring point P1 may be located in
the low pressure zone.
[0073] The pressure monitoring points P1, P2 may be located
anywhere as long as the pressure monitoring points P1, P2 are
located in the refrigerant circuit, that is, the high pressure
zone, the low pressure zone, and a medium pressure zone, which is
the crank chamber 12.
[0074] The control valve CV may be a variable target suction
pressure type control valve, which changes the target suction
pressure, or a variable target discharge pressure type control
valve, which changes the target discharge pressure, instead of the
variable target pressure difference type control valve, which
changes the target pressure difference. The variable target suction
(discharge) pressure type control valve CV includes a pressure
sensing mechanism and a target pressure changing mechanism. The
pressure sensing mechanism moves the valve body to change the
displacement of the compressor such that the mechanically detected
suction pressure (discharge pressure) converges to the target
value. The target pressure changing mechanism changes the target
suction pressure (target discharge pressure) by adjusting the force
applied to the valve body by the external command.
[0075] The control valve may be an electromagnetic valve that does
not have the pressure sensing mechanism.
[0076] The present invention may be applied to a drive unit of an
electromagnetic actuator, which directly changes the inclination of
the swash plate.
[0077] The present invention may be applied to a drive unit of a
motor used in a compressor that is actuated only by a motor, such
as a compressor used in an air-conditioner of an electric
automobile and a compressor used in an air-conditioner for home
use.
[0078] Therefore, the present examples and embodiments are to be
considered as illustrative and not restrictive and the invention is
not to be limited to the details given herein, but may be modified
within the scope and equivalence of the appended claims.
* * * * *