U.S. patent application number 10/166877 was filed with the patent office on 2003-05-15 for electric tool.
Invention is credited to Saito, Fumiaki, Tsuneda, Yukio.
Application Number | 20030089511 10/166877 |
Document ID | / |
Family ID | 26624489 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030089511 |
Kind Code |
A1 |
Tsuneda, Yukio ; et
al. |
May 15, 2003 |
Electric tool
Abstract
To provide a cordless electric tool promoting a fastening
function or a cutting function by facilitating to control a
rotational number of a motor from a low speed region to a high
speed region, reducing generation of vibration or noise and
achieving small-sized formation and light-weighted formation, there
is provided a cordless electric tool constituted by a brushless
direct current motor 3, an output shaft 5 connected to the
brushless direct current motor 3 via a speed changing device 4, a
motor driving circuit 7 and a control portion 8 of the driving
circuit and using a charge type battery 11 as a drive power
source.
Inventors: |
Tsuneda, Yukio; (Obama-shi,
JP) ; Saito, Fumiaki; (Obama-shi, JP) |
Correspondence
Address: |
JORDAN AND HAMBURG LLP
122 EAST 42ND STREET
SUITE 4000
NEW YORK
NY
10168
US
|
Family ID: |
26624489 |
Appl. No.: |
10/166877 |
Filed: |
June 11, 2002 |
Current U.S.
Class: |
173/217 |
Current CPC
Class: |
B25B 21/00 20130101;
B25F 5/001 20130101 |
Class at
Publication: |
173/217 |
International
Class: |
E21B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 12, 2001 |
JP |
2001-346652 |
Jan 17, 2002 |
JP |
2002-009132 |
Claims
What is claimed is:
1. An electric tool which is a cordless electric tool comprising a
motor, an output shaft connected to the motor via a speed changing
device, a motor driving circuit and a control portion of the
driving circuit and using a charge type battery as a drive power
source: wherein the motor is a brushless direct current motor.
2. An electric tool comprising: a brushless direct current motor
constituting a power source of the electric tool; a first operating
member for changing a maximal rotational speed of the brushless
direct current motor; a second operating member for changing a
rotational speed of the brushless direct current motor within a
range of the maximal rotational speed of the brushless direct
current motor set by the first operating member; and controlling
means for controlling a rotational state of the brushless direct
current motor; wherein the controlling means comprises: maximal
rotational speed signal outputting means for outputting a maximal
rotational speed signal in correspondence with a displacement of
the first operating member; and rotational speed signal outputting
means for constituting a maximal level by the maximal rotational
speed signal outputted from the maximal rotational speed signal
outputting means and outputting a rotational speed signal in
correspondence with a displacement of the second operating means to
thereby drive to rotate the brushless direct current motor.
3. The electric tool according to claim 1 or 2: wherein the
electric tool is an electric driver, an electric driver drill, an
electric impact driver or an electric wrench.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electric tool.
[0003] 2. Description of the Related Art
[0004] Conventionally, there has generally been used an electric
tool such as an electric drill or an electric driver of a portable
type as an electric tool used for operation of cutting such as
drilling or fastening a screw or a bolt. The electric tool is
provided with functions of controlling rotational speed or
rotational torque of a drive motor and switching a rotational
direction and is capable of interchanging a front end tool
thereof.
[0005] Particularly, in recent years, a cordless electric tool
having a direct current motor with brush constituting a power
source by a charge type battery, is simple in operation, excellent
in operability and spreads also for household use.
[0006] An explanation will be given of an outline of an inner
constitution (indicated by broken lines) of an example of a
conventional cordless electric tool in reference to an outlook view
of an electric driver drill 200 capable of using both of a driver
and a drill shown in FIG. 7.
[0007] The cordless electric driver drill 200 shown in the drawing,
is constituted by a driving portion 215 comprising a motor 203
constituting a drive source, a speed changing device 204 containing
a gear mechanism for reducing a rotational number of the motor 203
and an output shaft 205 connected to the speed changing device 204,
an operating portion 216 having a motor driving circuit 207, a
control portion 208 thereof and a switch 209 for controlling power
supply, and a power source portion 217 comprising a charge type
battery 211 and the electric driver drill 200 is formed by a
housing 202.
[0008] The operating portion 216 is contained at inside of a grip
portion 210, the charge type battery 211 is attachably and
detachably provided at a lower portion of the grip portion 210,
power thereof is transmitted to the driving portion 215 via the
control portion 208 and the motor driving circuit 207 by operation
of the switch 209, ON/OFF and the rotational number of the motor
203 are controlled, rotational force is transmitted to a drill (not
illustrated) mounted to a chuck 206 provided at a front end of the
output shaft 205, further, at a vicinity of the switch 209, there
is provided a switch 212 for switching a rotational direction of
the motor 203 and locking the rotational direction.
[0009] According to the above-described conventional electric
driver drill 200, there is used a direct current motor with brush
as the motor 203 of the drive source.
[0010] The direct current motor with brush is rotated at high speed
and therefore, it is difficult to control speed of the motor, it is
difficult to continuously control the rotational number of the
electric driver drill 200 in a low through high speed region and a
range of the rotational number which can be used, is divided into a
low speed region and high speed region and a restriction is imposed
on use of continuous variable speed over the two speed regions.
[0011] Further, control of the rotational number is controlled by
switching operation and therefore, the control needs an expensive
switch and is inferior in operability since controllability thereof
is poor.
[0012] Further, since the motor is rotated at high speed, it is
necessary to use the motor by increasing a speed reduction ratio by
gears and therefore, there poses a problem that vibration or noise
is generated significantly, further, the tool is heavy and large
since a comparatively large-sized speed changing device is used and
the operability is poor.
[0013] Further, there poses a problem of noise by generating spark
in rotating the brush, noise of a radio, a disturbance of a
television screen, generation of noise by sliding movement of the
brush and a commutator. Further, the brush is accompanied by
service life and there is needed maintenance such as check or
interchange of the brush or the motor.
[0014] Hence, it is a first object of the invention to provide a
cordless electric tool facilitating to control a rotational number
of a drive motor from a low speed region to a high speed region,
promoting functions of cutting and fastening by selecting a
rotational number over a wide range, reducing generation of
vibration and noise and achieving small-sized formation,
light-weighted formation and long life formation.
[0015] Next, FIG. 8 is a view showing an outline of a constitution
of an operating portion 301 of the above-described electric tool
and FIG. 9 is a circuit diagram showing an electric constitution of
a lever switch circuit 304 of the operating portion 301 of the
electric tool.
[0016] An explanation will be given of the operating portion 301 of
the electric tool also in reference to FIG. 8 and FIG. 9.
[0017] The operating portion 301 of the electric tool is
constituted by including an operating portion main body 302
including a battery, a motor and a motor control circuit, and an
operating lever 303 belonging to the operating portion main body
302 and operated by the hand and the finger of an operator.
[0018] The operating portion 301 of the electric tool is provided
with the lever switch circuit 304 for outputting a pulse width
modulated signal (hereinafter, referred to as PWM signal) for
driving the motor in correspondence with an operational state of
the operating lever 303. The lever switch circuit 304 is provided
with a slide resistor circuit 305. The slide resistor circuit 305
is provided with a resistor R1 and a slide terminal 306 and the
resistor R1 is provided between power source voltage Vdd and ground
potential. Reference voltage Vth constituting an output of the
slide terminal 306, is inputted to a noninverting input terminal of
a comparing circuit 307 and an inverting input terminal of the
comparing circuit 307 is inputted with a predetermined triangular
wave signal.
[0019] An explanation will be given of operation of the lever
switch circuit 304.
[0020] Displacement of the operating lever 303 in an arrow mark A1
direction or an arrow mark A2 direction, is detected by the slide
resistor circuit 305. At this occasion, when the operating lever
303 is operated in the arrow mark A1 direction, the rotational
speed of the motor is increased and when the operating lever 303 is
operated in the arrow mark A2 direction, the rotational speed of
the motor is reduced.
[0021] In this case, in correspondence with displacement of the
slide terminal 306 in an arrow mark displacement direction A3, or
the displacement of the slide terminal 306 in an arrow mark A4
direction in correspondence with the arrow mark A1 direction or the
arrow mark A2 direction constituting the direction of operating the
operating lever 303, there is outputted the reference voltage Vth
an output level of which is increased or reduced from the slide
terminal 306 and is inputted to the noninverting input terminal of
the comparing circuit 307.
[0022] Thereby, in correspondence with operation of the operating
lever 303 in the arrow mark A1 direction or the arrow mark A2
direction, there is outputted a rotational speed signal S1
constituting the PWM signal in which on duty of the triangular wave
signal is pertinently controlled from the comparing circuit 307 and
the rotational speed signal constitutes the output of the lever
switch circuit 304. The rotational speed signal S1 drives to rotate
the motor via, for example, an inverter circuit including a
switching transistor for driving the motor.
[0023] In the case of the operating portion 301 of the conventional
electric tool, when actual operation is carried out, depending on
content of the operation, there is a case in which the operation is
carried out at intermediate rotational speed lower than maximal
rotational speed of the operating portion 301 of the electric tool.
In such a case, the operator carries out the operation not in a
state of completely gripping to tighten the operating lever 303 but
in a state of gripping the lever intermediately and when the
operational time period is prolonged, there causes a drawback that
the rotational speed becomes unstable owing to fatigue of the hand
and the finger, or fatigue of the operator is increased.
[0024] Hence, it is a second object of the invention to provide an
electric tool capable of carrying out stable operation by
preventing enormous fatigue from being effected to the
operator.
SUMMARY OF THE INVENTION
[0025] According to a first aspect of the invention, there is
provided an electric tool which is a cordless electric tool
comprising a motor, an output shaft connected to the motor via a
speed changing device, a motor driving circuit and a control
portion of the driving circuit and using a charge type battery as a
drive power source wherein the motor is a brushless direct current
motor.
[0026] According to a second aspect of the invention, there is
provided an electric tool comprising a brushless direct current
motor constituting a power source of the electric tool, a first
operating member for changing a maximal rotational speed of the
brushless direct current motor, a second operating member for
changing a rotational speed of the brushless direct current motor
within a range of the maximal rotational speed of the brushless
direct current motor set by the first operating member, and
controlling means for controlling a rotational state of the
brushless direct current motor, wherein the controlling means
comprises maximal rotational speed signal outputting means for
outputting a maximal rotational speed signal in correspondence with
a displacement of the first operating member, and rotational speed
signal outputting means for constituting a maximal level by the
maximal rotational speed signal outputted from the maximal
rotational speed signal outputting means and outputting a
rotational speed signal in correspondence with a displacement of
the second operating means to thereby drive to rotate the brushless
direct current motor.
[0027] According to a third aspect of the invention, there is
provided the electric tool according to the first or the second
aspect wherein the electric tool is an electric driver, an electric
driver drill, an electric impact driver or an electric wrench.
[0028] According to the electric tool of the first aspect of the
invention, the drive source is constituted by the brushless direct
current motor and therefore, power consumption can be restrained to
be small since the motor efficiency is high, further, a control
range of the rotational number becomes wide, control of the
rotational number of the electric tool from the low speed region to
the high speed region is facilitated and therefore, a width of
selecting a rotational function of the electric tool becomes wide,
the rotational function in accordance with the use can easily be
achieved and an expensive switch for controlling the rotational
number is dispensed with.
[0029] Further, by using the brushless direct current motor, the
service life of the tool is prolonged, maintenance is promoted and
the problem of generation of spark in rotation is resolved.
[0030] Further, the speed ratio by the gears of the rotational
number of the motor can be reduced, further, sliding sound of the
brush can be eliminated, generation of vibration or noise can be
restrained, further, the speed changing device can be made
small-sized and therefore, small-sized formation and light-weighted
formation of the electric tool can be achieved.
[0031] According to the electric tool of the second aspect of the
invention, the maximal rotational speed of the brushless direct
current motor is changed and set by operating the first operating
member. Based on operation of the first operating member, the
maximal rotational speed signal is outputted from the maximal
rotational speed signal outputting means included in the
controlling means. Further, the second operating member is operated
in order to change the rotational speed of the brushless direct
current motor.
[0032] Based on operation of the second operating means, the
rotational speed signal outputting means included in the
controlling means constitutes the maximal level by the maximal
rotational speed signal and the rotational speed signal in
correspondence with the displacement of the second operating means
is outputted to thereby drive to rotate the brushless direct
current motor.
[0033] Therefore, when the rotational speed necessary for actual
operation is set to the maximal rotational speed of the electric
tool by using the first operating means, in the case of operating
the second operating means, the rotational speed of the brushless
direct current motor is changed within the range of the maximal
rotational speed of the brushless direct current motor set by the
first operating means and in the case of constituting the maximal
rotational speed by maximally operating the second operating means,
the rotational speed necessary for the operation is
constituted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is an outlook view of an electric driver drill
according to a first embodiment;
[0035] FIG. 2 is a block diagram of a motor driving circuit;
[0036] FIG. 3 is a circuit diagram showing an electric constitution
of an essential portion of an electric impact driver;
[0037] FIG. 4 is a block diagram showing an electric constitution
of the electric impact driver;
[0038] FIG. 5 is a outlook view of an electric impact driver;
[0039] FIG. 6 is a circuit diagram showing an electric constitution
of an electric impact driver according to a second embodiment of
the invention;
[0040] FIG. 7 is an outlook view of an electric driver drill
according to a conventional technology;
[0041] FIG. 8 is a view showing an outline of a constitution of an
operating portion of an electric tool according to a conventional
technology; and
[0042] FIG. 9 is a circuit diagram showing an electric constitution
of a lever switch circuit of the operating portion.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] (First Embodiment)
[0044] An explanation will be given of an inner constitution shown
by broken lines of an embodiment of the invention in reference to
an outlook view of a cordless electric driver drill 1 shown in FIG.
1.
[0045] A cordless electric driver drill 1 shown in the drawing, is
constituted by a driving portion 15 comprising a brushless direct
current motor 3 constituting a drive source, a speed changing
device 4 for reducing a rotational number of the brushless direct
current motor 3 and an output shaft 5 connected to the speed
changing device 4, an operating portion 16 having a motor driving
circuit 7, a control portion 8 thereof and a switch 9 for
controlling power supply, and a power source portion 17 comprising
a charge type battery 11 and the electric driver drill 1 is formed
by a housing 2.
[0046] According to the driving portion 15, a drive shaft of the
brushless direct current motor 3 is connected with the speed
changing device 4 containing a gear mechanism for reducing the
rotational number, a front portion of the speed changing device 4
is connected with the output shaft 5 and a front end of the output
shaft 5 is provided with a chuck 6 for mounting a front end tool
such as a bit or a drill.
[0047] The operating portion 16 is constituted by the motor driving
circuit 7 and the control portion 8 thereof and the switch 9 for
controlling power supply from a power source and the operating
portion 16 is contained in a grip portion 10 of the housing 2.
[0048] According to the driving portion 15 and the operating
portion 16, respective parts thereof are fixed at inside of the
housing 2, the driving portion 15 and the operating portion 16 are
connected to each other by lead wires, not illustrated, to thereby
form the electric driver drill 1 and a vicinity of the drive switch
9, is provided with a switch 12 for switching a rotational
direction of the brushless direct current motor 3 and locking the
rotational direction.
[0049] The power source portion 17 of the electric driver drill 1
is constituted by the charge type battery 11 provided attachably
and detachably at a lower portion of the grip portion 10 and the
charge type battery 11 is provided with a cartridge type attaching
and detaching means attached to and detached from a bottom portion
of the grip portion 10 and electric contacts commonly for supplying
power to the electric driver drill 1 and charging the battery.
[0050] As shown by a block diagram of FIG. 2, the motor driving
circuit 7 is for driving the brushless direct current motor 3 by
being supplied with power from the charge type battery 11 and is
constituted by an inverter circuit 21 constituted by switching
transistors, a logical circuit 22 for controlling the inverter
circuit 21 and a rotational speed detecting circuit 24 for
detecting the rotational direction by a signal of a position
detecting element 23 comprising a Hall element included in the
brushless direct current motor 3. The logical circuit 22 carries
out a feedback control to rotate the brushless direct current motor
3 by instructed speed by a speed instructing signal from the
control portion 8 and a rotational speed signal from the rotational
speed detecting circuit 24 and an output thereof is transmitted to
the speed changing device 4.
[0051] The electric driver drill 1 is constituted such that by
operating the switch 9, power of the battery 11 is transmitted to
the driving portion 15 via the control portion 8 and the motor
driving circuit 7, ON/OFF and the rotational number of the
brushless direct current motor 3 are controlled, driving force is
transmitted from the speed changing device 4 to the output shaft 5,
a front end tool (not illustrated) of a bit or a drill mounted to
the front end is rotated to thereby carry out cutting such as
drilling or chipping or operation of fastening a screw or a
bolt.
[0052] According to the electric driver drill 1, the brushless
direct current motor 3 is used for the motor constituting the drive
source.
[0053] According to the brushless direct current motor 3, a control
range of the rotational number of the motor per se becomes wider
than that of the conventional direct current motor with brush,
control of the rotational number is facilitated and the rotational
number from the low speed region to the high speed region can
continuously be used variably, there can be facilitated selection
of the rotational speed for use at high speed rotation or use at
low speed and high torque rotation depending on the use of the
electric tool and operability and maneuverability of the electric
tool can significantly be promoted.
[0054] That is, by controlling a degree of pulling the switch 9,
low speed through high speed rotation can continuously be selected
variably by the feedback control of the motor driving circuit,
desired rotational torque can be achieved and therefore, a width of
selection of the rotational number region becomes wide depending on
the use and the content of operation such as drilling operation at
high speed rotation or fastening a screw or a bolt at low speed
high torque rotation, further, operation can be carried out
variably and therefore, the operability is promoted. Further, the
switch 9 having a constitution simpler than conventional one can be
used and an inexpensive switch can be utilized.
[0055] Further, the rotational number of the motor is lower than
that of the motor with brush and therefore, the speed reduction
ratio of the rotational number by the gear mechanism can be
reduced, vibration or noise generated at inside of the speed
changing device is reduced, sound emitted by sliding the brush and
the commutator is eliminated and vibration or noise of the electric
tool can be restrained from being generated than that of the
conventional tool.
[0056] Further, by reducing the speed reduction ratio, the gear
mechanism is simplified, small-sized and light-weighted formation
of the speed changing device can be achieved and the operability
can be promoted by the light-weighted compact formation of the
tool.
[0057] Further, maintenance performance is promoted by dispensing
with interchanging the brush and checking the motor, which has been
needed in the conventional motor with brush, the service life of
the electric tool is prolonged and there is also resolved the
problem of noise of a radio or a disturbance in a television screen
by generating spark in rotating the brush.
[0058] An electric tool using the above-described brushless direct
current motor is applicable to an electric driver, an electric
driver drill, an electric impact driver or an electric wrench and
there can be provided an electric tool excellent in operability in
cutting or fastening, small sized, light-weighted, having excellent
maneuverability and accompanied by low vibration and low noise.
[0059] Further, according to the respective electric tools, by
providing a vibration generating function or an impact generating
function for generating vibration or impact to a drill or a driver
of the front end tool, the above-described respective electric
tools can be used also for an electric impact driver, a vibration
drill or an electric chipping machine.
[0060] Further, depending on the use, the electric tool is
applicable also to a tool of a stepped variable type by using the
brushless direct current motor.
[0061] Further, although an explanation has been given of the
electric tool using the charge type battery of an attaching and
detaching type as the power source according to the above-described
embodiment, the electric tool is applicable to an electric tool of
a battery fixing type constituting a power source portion by
providing a charge type battery at inside of a main body of the
electric tool, for example, containing the charge type battery at a
lower side portion of a grip portion.
[0062] Although a nickel cadmium battery or nickel hydrogen battery
is exemplified as the charge type battery, the battery is not
limited so far as the battery is the charge type battery.
[0063] Further, the electric tool can be used in, for example, a
pencil type in a rod-like shape or a type capable of being folded
at a central portion other than the pistol type shown in the
drawing.
[0064] Further, although according to the above-described
embodiment, an explanation has been given of the invention in
accordance with the electric driver drill of a hand held type, the
electric tool of the invention can be used not only for the
above-described electric driver, electric impact driver, electric
wrench but also electric tools of an electric drill, an electric
plane, an electric saw, cutters such as screw cutter and a knife
cutter, a plant clipper and polishing machines such as a sander and
a polisher and can naturally be used for electric tools of a desk
top type such as a drilling machine.
[0065] (Second Embodiment)
[0066] An explanation will be given of a second embodiment of the
invention in reference to FIG. 3 through FIG. 5.
[0067] FIG. 3 is a circuit diagram showing an electric constitution
of an essential portion of an electric impact driver 111 of a
cordless type according to the embodiment, FIG. 4 is a block
diagram showing an electric constitution of the electric impact
driver 111 and FIG. 5 is a outlook view of the electric impact
driver 111.
[0068] Although in the following embodiment, an explanation will be
given by exemplifying the electric impact driver 111 of the
cordless type, the invention is not limited to the example but
generally and widely embodied to an electric impact driver which is
not of a cordless type but is used while being connected to a power
source, or other electric tool.
[0069] (1) Constitution of the Electric Impact Driver 111
[0070] An explanation will be given of a constitution of the
electric impact driver 111 in reference to FIG. 5 as follows.
[0071] The electric impact driver 111 is provided with a main body
112, a tool 113 mounted to one end portion of the main body 112 and
a grip portion 114 integrally formed with other end portion of the
main body 112.
[0072] The main body 112 is contained with a brushless direct
current motor 123.
[0073] The grip portion 114 is formed to be able to be gripped by
the hand of an operator and a portion thereof where the finger is
disposed in a gripping state, is arranged with a rotational speed
switching lever (hereinafter, referred to as speed lever) 115 in a
trigger-like shape. Further, a lower portion of the grip portion
114 is provided with a battery 120 of a charge type. The battery
120 is charged by being mounted on a charger 120a connected to
AC100V power source.
[0074] A lock switch 116 for fixing a state of pulling the speed
lever 115 is provided at a vicinity of the speed lever 115.
[0075] A vicinity of the grip portion 114 of the main body 112 is
arranged with a changeover switch 117 for switching rotation of the
brushless direct current motor 123 and accordingly, rotation of the
tool 113 between predetermined regular rotation and inverse
rotation. Further, a top portion of the main body 112 is provided
with a maximal speed setting switch (hereinafter, referred to as
setting switch) 119 for setting maximal rotational speed of the
tool 113.
[0076] (2) Electric Constitution of the Electric Impact Driver
111
[0077] An explanation will be given of an outline of an electric
constitution of the electric impact driver 111 also in reference to
FIG. 4 as follows.
[0078] The electric impact driver 111 is provided with a speed
controlling portion 121, a controller 122 and the brushless direct
current motor 123 supplied with power source by the battery
120.
[0079] The speed controlling portion 121 detects operation of the
speed lever 115 and the setting switch 119 as described below and
outputs a rotational speed signal S1 subjected to PWM (pulse width
modulation) for driving the blushless direct current motor in
correspondence with operational states of the lever 115 and the
setting switch 119 to the controller 122. The controller 122
includes a plurality of switching transistors (not illustrated)
driven to ON/OFF based on the rotational speed signal S1 from the
speed controlling portion 121 and a drive signal for driving the
brushless direction motor 123 is outputted from the switching
transistors.
[0080] The speed controlling portion 121 is provided with a maximum
speed changing lever switch circuit 24 for detecting operation of
the setting switch 119 and a rotational speed changing lever switch
circuit 125 for detecting operation of the speed lever 115. A
control apparatus is constituted by including the speed controlling
portion 121.
[0081] (3) Electric Constitution of the Speed Controlling Portion
121
[0082] An explanation will be given of an example of an electric
constitution of the speed controlling portion 121 also in reference
to FIG. 3 as follows.
[0083] The maximum speed changing lever switch circuit 124 is
provided with resistors R11 and R12 connected in series between
power source voltage vdd and ground potential and a slide terminal
126 for being slidingly moved relative to the resistor R11. An
output of the slide terminal 126 is outputted to the rotational
speed changing lever switch circuit 125.
[0084] The rotational speed changing lever switch circuit 125 is
provided with a resistor R13 inputted with the output from the
slide terminal 126 and other end of the resistor R13 is
grounded.
[0085] The resistor R13 is provided with a slide terminal 127,
reference voltage Vth outputted from the slide terminal 127 is
inputted to a noninverting input terminal of a comparing circuit
128 and an inverting input terminal of the comparing circuit 128 is
inputted with a predetermined triangular wave signal. The
rotational speed signal S1 is outputted from the comparing circuit
128.
[0086] (4) Operation of the Electric Impact Driver 111
[0087] An explanation will be given of operation of the electric
impact driver 111 as follows.
[0088] First, in correspondence with content of operation, by
operating the setting switch 119, the maximal rotational speed of
the electric impact driver 111 is set. According to the embodiment,
the maximal rotational speed is set variably. That is, in
correspondence with operation of the setting switch 119, the slide
terminal 126 is variably displaced and the maximum speed voltage Vs
in correspondence with an operational position of the setting
switch 119 stopped at a predetermined position.
[0089] Next, in carrying out actual fastening operation, the
operator operates the speed lever 115. Actually, the grip portion
114 shown in FIG. 5 is gripped and the speed lever 115 is gripped
by the hand and the finger. According to the embodiment, in
correspondence with large or small of a degree of gripping the
speed lever 115, the slide terminal 127 is displaced in an arrow
mark B1 direction or an arrow mark B2 direction. In correspondence
with the direction and the degree of the displacement, the
reference voltage Vth from the slide terminal 127 is increased or
reduced. The maximum value of the reference voltage vth is the
maximum speed voltage Vs.
[0090] That is, the maximum speed voltage Vs is divided by the
resistor R13 and the slide terminal 127 and the reference voltage
Vth provided by dividing the voltage is inputted to the
noninverting input terminal of the comparing circuit 128. From the
comparing circuit 128, there is outputted the rotational speed
signal S1 subjected to the PWM modulation in which the higher the
reference voltage Vth, the higher the on duty. As described above,
the rotational speed signal S1 is outputted to the controller 122
and the brushless direct current motor 123 is driven to rotate.
[0091] In this way, according to the embodiment, when the maximal
rotational speed of the electric impact driver 111 is set based on
operation of the setting switch 119, even in the case in which the
maximal rotational speed by the speed lever 115 is constituted by
operating the speed lever 115, the maximal rotational speed is
constituted by the maximal rotational speed set by the setting
switch 119. Thereby, when the rotational speed necessary for actual
operation is set by operating the setting switch 119, the operation
can be carried out in a state of operating to maximally gripping
the speed lever 115.
[0092] Thereby, there is resolved to eliminate a necessity to carry
out operation in the state of intermediately gripping the speed
lever 115 to constitute intermediate rotational speed lower than
the maximal rotational speed in order to provide the rotational
speed necessary for the actual operation and fatigue of the
operator can significantly be reduced. Further, there can be
resolved to eliminate unstable formation of the rotational speed
caused by carrying out the operation in the state of intermediately
gripping the speed lever 115 by the operator and stable operation
can be carried out.
[0093] (Third Embodiment)
[0094] FIG. 6 is a circuit diagram showing an electric constitution
of an electric impact driver 111a according to a third embodiment
of the invention.
[0095] The embodiment is similar to the second embodiment,
corresponding portions are attached with the same reference
notations and a further explanation thereof will be omitted.
[0096] A characteristic of the embodiment resides in setting the
maximal rotational speed of the electric impact driver 111a in
multiple stages. An explanation will be given of an electric
constitution of the electric impact driver 111a as follows. The
embodiment is also similarly provided with the constitution
explained in reference to FIG. 4 and FIG. 5 in the second
embodiment.
[0097] (1) Electric Constitution of Speed Controlling Portion
121a
[0098] An explanation will be given of an example of an electric
constitution of a speed controlling portion 121a provided in the
electric impact driver 111a according to the embodiment also in
reference to FIG. 6 as follows.
[0099] A maximal speed changing lever switch circuit 124a is
provided with a plurality of resistors R14, R15 . . . connected in
parallel between the power source voltage Vdd and the ground
potential and having resistance values different from each other as
an example and a changeover switch 129. Reference voltage Vth
constituting an output of the changeover switch 129, is outputted
to the resistor R13 of the rotational speed changing lever switch
circuit 125 having a constitution similar to the constitution of
the first embodiment.
[0100] (2) Operation of the Electric Impact Driver 111a
[0101] An explanation will be given of operation of the electric
impact driver 111a according to the embodiment. First, in
correspondence with content of operation, by operating the setting
switch 119, the maximal rotational speed of the electric impact
driver 111a is set.
[0102] That is, in correspondence with the operation of the setting
switch 119, the changeover switch 129 is connected to any one of
the power source voltage Vdd, the resistor R14, the resistor R15 .
. . . When the changeover switch 119 is connected to the power
source voltage Vdd, the maximal rotational speed of the electric
impact driver 111a is constituted.
[0103] Operation of the rotational speed changing lever switch
circuit 125 thereafter is similar to that of the above-described
embodiment and accordingly, also operation of the electric impact
driver 111a is similar thereto.
[0104] Therefore, also according to the embodiment, operation and
effect similar to operation and effect explained in the first
embodiment are realized.
Industrial Applicability
[0105] The electric tool according to the first aspect of the
invention is the cordless electric tool using the charge type
battery as the drive power source of the motor, the motor is
brushless direct current motor and therefore, the electric tool can
be used by variable speed changing by selecting the rotational
number and the rotational torque of the electric tool from wide
ranges, further, generation of vibration or noise can be reduced,
small-sized and light-weighted formation can be achieved and
therefore, there is provided the cordless electric tool having a
high function, excellent in maneuverability and capable of
achieving an improvement in an operational environment and durable
years of the electric tool can be prolonged.
[0106] According to the electric tool of the second aspect of the
invention, the maximal rotational speed of the brushless direct
current motor is set by operating the first operating member and
the second operating member is operated within the set maximal
rotational speed range to thereby change the rotational speed of
the brushless direct current motor. Thereby, when the rotational
speed necessary for operation is set to the maximal rotational
speed of the electric tool by using the first operating means, even
in the case of constituting the maximal rotational speed by
maximally operating the second operating means, the rotational
speed necessary for the operation is constituted.
[0107] Therefore, the operation can be carried out by maximally
operating the second operating means by changing the maximal
rotational speed in correspondence with content of the operation
using the electric tool. Thereby, there is resolved to eliminate a
necessity of continuing operation while maintaining the second
operating means at an intermediate operational state by the
operator, a situation of causing enormous fatigue for the operator
is prevented and stable operation can be carried out.
[0108] Further, fastening force is made constant, in the case of
fastening a screw, fastening torque is made uniform and quality of
a product is stabilized.
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