JP2008296323A - Power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power tool with a trigger switch control circuit in which the operability of a trigger switch is improved for facilitating the control of the number of rotations of a motor at the start of the rotation. <P>SOLUTION: In a low-speed range pressed area d1 where the trigger pressed amount d of a trigger switch part 13 is equal to or less than a first pressed amount D1, a control circuit part 3 increases the number of rotations N of the motor 1 at a predetermined first speed increasing rate in a first speed area between the lower limit number of rotations N1 for transmitting a rotational force to the load of an end tool and the upper limit number of rotations N2 specified by the operability of the end tool which is lower than a full speed number of rotations Nm, or is controlled correspondingly to the trigger pressed amount d so as to be a specified number of rotations. In a high-speed range pressed area d2 where the trigger pressed amount d reaches the maximum pressed amount Dm beyond the first pressed amount D1, the control part increases the number of rotations N of the motor at a second speed increasing rate which is higher than the speed increasing rate in the low-speed range pressed area d1 in a second speed area between the upper limit number of rotations N2 and the full speed number of rotations Nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric tool for driving a tip tool such as a screw tightening bit, and more particularly to a control circuit unit for controlling the number of rotations of an electric motor for driving the tip tool in response to the pushing amount of a trigger switch. It has an electric power tool.

  In an electric tool having a rotary tip tool such as a drill or a driver driven by an electric motor, a technique for controlling the rotation speed of an electric motor serving as a power source of the electric tool by operating a trigger switch having a trigger operation unit is, for example, It is disclosed in the following Patent Document 1. In this technique, the number of rotations of the motor is controlled by varying the applied voltage supplied to the electric motor in response to the pushing amount (operation amount) of the trigger switch, that is, the displacement amount.

  Generally, as the trigger push amount of the trigger switch increases, the applied voltage is increased in proportion to the trigger push amount, and as a result, the motor rotation speed is controlled to increase in proportion to the trigger push amount. . Such control prevents the rapid rotation of the motor at the start of the work and rotates the motor at a low speed, so that the tip tool can be machined in operations such as screw tightening, drilling, and cutting. This is to facilitate positioning or processing with respect to the object.

JP-A-8-66084

  In the motor control system using the conventional trigger switch as described above, the motor rotation speed increases proportionally with the pressing amount (operation amount) of the trigger operation unit. A delicate trigger operation is required to hold the motor rotation number in a desired low speed region by holding the trigger switch so as to be small.

  However, in practice, it is difficult for the operator to keep the trigger push-in amount small, and there is a problem that the rotational operation of the electric motor becomes unstable due to a slight variation in the trigger push-in amount. For example, there is a case where the trigger is pushed too small to stop the motor, or the voltage applied to the electric motor is controlled so that the motor cannot be started. Conversely, if the trigger push amount is increased too much and the motor rotation speed is increased rapidly, the end tool such as the driver bit of the electric tool is disengaged from the predetermined position of the workpiece, and the end tool is processed. This caused the problem of damaging the member. Furthermore, the operability of the electric power tool is impaired, and there may be a problem that work efficiency is lowered.

  Accordingly, an object of the present invention is to provide an electric tool including a trigger switch control circuit in which the operability of the trigger switch is improved in order to facilitate the control of the rotation speed at the start of rotation of the electric motor. is there.

  Another object of the present invention is to provide an electric tool including a brushless DC motor in which the rotational speed control of the motor based on the pushing amount of the trigger switch is improved in order to solve the above-described conventional problems.

  In order to achieve the above object of the present invention, typical features of the invention disclosed in the present application will be described as follows.

  According to one aspect of the present invention, an electric motor mounted in the housing portion, a tip tool provided in the housing portion that is rotationally driven by the electric motor, a trigger switch portion provided in the housing portion, An electric tool having a control circuit unit for controlling the rotation speed of the electric motor from the rotation start to the full-speed rotation speed according to a trigger pressing amount of the trigger switch unit, wherein the control circuit unit is configured to control the trigger of the trigger switch unit. In the first indentation range in which the indentation amount is equal to or less than the first indentation amount, the rotation speed of the electric motor is set to the lower limit rotation speed for transmitting the rotational force to the load of the tip tool and the tip lower than the full speed rotation speed. Within a first rotational speed range between the upper limit rotational speed defined by the operability of the tool, it is increased at a predetermined first rotational speed increase rate, or a constant rotational speed In the second push range in which the trigger push amount of the trigger switch unit is controlled in response to the trigger push amount and reaches the maximum push amount exceeding the first push amount, Second rotation of the electric motor within a second rotation speed range between the upper limit rotation speed and the full speed rotation speed is higher than the first rotation speed increase rate in the first push-in range. Control is performed in response to the trigger push-in amount so as to increase at a numerical increase rate.

  According to another feature of the invention, the rotational speed of the electric motor is controlled to a constant rotational speed in the first pushing range, and is increased from the constant rotational speed to the full speed rotational speed in the second pushing range. To control.

  According to still another aspect of the present invention, the trigger pushing amount of the trigger switch unit is converted into a voltage level by a potentiometer, and the applied voltage of the electric motor is varied using the converted voltage as a control signal. The rotational speed of the electric motor is controlled.

  According to still another aspect of the present invention, the brushless DC motor includes a rotor having a permanent magnet and a stator having a multi-phase armature winding, and a plurality of bridge-connected switching elements. An inverter that switches a DC voltage to supply power to the armature windings of each phase; an inverter driving unit that drives the plurality of switching elements with a pulse width modulation signal; A trigger switch unit for controlling the rotational speed of the DC motor, and a control circuit unit for controlling the rotational speed of the brushless DC motor from the start of rotation to the full-speed rotational speed based on the trigger pushing amount of the trigger switch unit; A power tool comprising: a tip tool that is rotationally driven by the brushless DC motor via a rotation transmission mechanism. The control circuit unit transmits the rotational force of the electric motor to the load of the tip tool in a first pressing range in which the trigger pressing amount of the trigger switch unit is equal to or less than the first pressing amount. In the first rotation speed range between the lower limit rotation speed of the first rotation speed and the upper limit rotation speed defined by the operability of the tip tool lower than the full speed rotation speed. Or a duty ratio of the pulse width modulation signal for driving the plurality of switching elements in response to the trigger push-in amount so as to be a constant rotation number, and the trigger push-in amount of the trigger switch unit is Within the second pressing range that exceeds the first pressing amount and reaches the maximum pressing amount, the rotational speed of the brushless DC motor is set to a second rotational speed between the upper limit rotational speed and the full speed rotational speed. Within range The pulse width for driving the plurality of switching elements in response to the trigger pressing amount so as to increase at a second rotation speed increase rate higher than the first rotation speed increase rate in the first pressing range. Controls the duty ratio of the modulation signal.

  According to still another aspect of the present invention, the control circuit unit includes an applied voltage setting unit that presets a change in the duty ratio of the pulse width modulation signal with respect to the trigger pushing amount of the trigger switch unit, The duty ratio of the pulse width modulation signal is varied by controlling the drive signal forming unit according to the output of the application setting unit.

  According to the above-mentioned one feature of the present invention, in the first pushing range where the trigger pushing amount of the trigger switch is not more than the predetermined first pushing amount from the pushing start, the rotation speed of the electric motor is set to the load of the tip tool. By controlling the power tool within a first rotational speed range between a lower limit rotational speed for transmitting the rotational force and an upper limit rotational speed defined by the operability of the tip tool lower than the full speed rotational speed, The person can hold the trigger operation in the desired low speed region of the motor rotation speed.

  That is, since the allowable pressing range at the start of motor rotation is substantially widened, a delicate operation for keeping the pressing amount of the trigger switch small becomes unnecessary. In this case, by setting a lower limit value for the motor rotation speed, the problem that the motor stops due to the load of the tip tool can be solved. Further, since the upper limit value of the motor rotational speed is provided in the first pressing range of the trigger pressing amount, it is possible to prevent a rapid increase in the motor rotational speed.

  This facilitates control of the motor in the low speed region by operating the trigger switch, and improves the operability or work efficiency of the electric tool at the start of work.

  In addition, in the first push range of the trigger push amount, the motor rotation speed is controlled to a constant value within a range from a predetermined upper limit value to a predetermined lower limit value, so that constant control in the low speed region of the motor by the trigger switch is possible. It becomes easy, and the operability or work efficiency of the power tool can be further improved.

  According to the other feature of the present invention, the motor is constituted by a brushless DC motor, and the control circuit unit sets the duty ratio of the pulse width modulation signal for driving the switching element of the inverter by the trigger push-in amount. The change rate of the motor rotation speed with respect to the amount can be easily changed.

  The above and other objects of the present invention as well as the above and other novel features of the present invention will become more apparent from the following description of the present specification and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  FIG. 1 is a structural diagram showing an entire electric tool when the present invention is applied to a cordless type impact driver, FIG. 2 is a functional block diagram showing an entire motor drive circuit portion of the electric tool constituted by a brushless DC motor, and FIG. FIG. 4 is a schematic structural diagram of a trigger switch used in the electric tool of the present invention shown in FIG. 1, FIG. 4 is a characteristic diagram of the trigger push-in detection unit of the trigger switch used in the electric tool of the present invention shown in FIG. Each of 5 and FIG. 6 shows a characteristic diagram of the duty ratio of the pulse width modulation signal and a characteristic diagram of the motor rotation speed with respect to the trigger pressing amount of the trigger switch used in the electric power tool of the present invention.

  Initially, the whole electric tool which concerns on embodiment of this invention with reference to FIG. 1 is demonstrated. The electric tool (impact driver) 50 extends from one end portion (right end portion in the drawing) to the other end portion (left end portion in the drawing) along the same direction (horizontal axis direction) as the rotation axis of the brushless DC motor 1 described later. The tip tool holding portion 31 disposed at the other end portion of the body housing portion 21a includes a tool body composed of an existing body housing portion 21a and a handle housing portion 21b depending from the body housing portion 21a. Although not provided, a driver bit (tip tool) for receiving a rotational impact force from the tool body and tightening a screw (fastening tool) to the workpiece is detachably mounted. In place of the driver bit as a tip tool, a bolt tightening bit can also be mounted. That is, the brushless DC motor 1 serving as a drive source is attached to one end of the body housing portion 21a, and a tip tool (not shown) is attached to the tip tool holding portion 31 that outputs a rotational impact force to the other end of the body housing portion 21a. None) is detachably mounted.

  An inverter part (circuit board) 2 for driving the brushless DC motor 1 is mounted on one end side of the body housing part 21a. In the middle part of the body housing part 21a, there are a power transmission mechanism part (deceleration mechanism part) 22 for transmitting rotational force in the direction of the rotational axis of the motor 1, an impact mechanism part 26 for giving the rotational impact force, and the impact mechanism part 26. An anvil 30 that transmits the rotational impact force to the tip tool is mounted.

  A battery pack 4 serving as a driving power source for the brushless DC motor 1 is detachably attached to the lower end portion of the handle housing portion 21b. A control circuit unit ((circuit board) 3) for controlling the inverter unit 2 of the motor 1 is provided on the upper part of the battery pack 4 so as to extend in a direction crossing the paper surface. A trigger switch portion 13 is disposed at the upper end portion of the housing portion 21b, and the trigger operation portion 13a of the trigger switch portion 13 protrudes from the handle housing portion 21b in a state of being biased by a spring force. By gripping the trigger operation portion 13a in the handle housing portion 21b inward against the spring force, the trigger push-in amount (operation amount) can be adjusted and the rotation speed of the motor 1 can be controlled.

  The battery pack 4 is electrically connected so as to supply drive power to the trigger switch unit 13 and the control circuit unit (circuit board) 3 and to supply drive power to the inverter unit 2.

  The rotational force of the rotation output shaft of the brushless DC motor 1 is a spindle that constitutes a part of the impact mechanism portion 26 via the power transmission mechanism portion (deceleration mechanism portion) 22 engaged with the gear teeth of the rotation output shaft. 28. The power transmission mechanism (deceleration mechanism) 22 includes a pinion gear (sun gear) 25 and two planetary gears 23 meshing with the pinion gear 25, which are provided in an inner cover (not shown) in the body housing portion 21a. It has been incorporated. The spindle 28 is given a rotational force reduced by the reduction mechanism 22 with respect to the rotation of the brushless DC motor 1.

  The impact mechanism section 26 includes a spindle 28 to which a rotational force is applied via the speed reduction mechanism section 22, and a hammer 27 that is attached to the spindle 28, engages movably in the direction of the rotation axis of the spindle 28, and provides a rotational impact force. And an anvil 30 that rotates with a hammering force by the hammer 27 and has a tip tool holding portion 31. The hammer 27 and the anvil 30 have two hammer convex portions (striking portions) 27a and two anvil convex portions 30a arranged symmetrically with each other at two locations on the rotation plane, respectively. The hammer convex portion 27a and the anvil The convex portions 30a are in positions that mesh with each other in the rotational direction.

  The rotational striking force is transmitted by the engagement of the convex portions 27a and 30a. Further, the hammer 27 is slidable in the axial direction with respect to the spindle 28 in a ring region surrounding the spindle 28 and is urged forward in the axial direction by a spring 29. An inverted V-shaped (substantially triangular) cam groove 27 b is provided on the inner peripheral surface of the hammer 27. On the other hand, a V-shaped cam groove 28 a is provided in the axial direction on the outer peripheral surface of the spindle 28, and a ball (steel ball) 32 inserted between the cam groove 28 a and the inner peripheral cam groove 27 b of the hammer 27. The hammer 27 rotates via the.

  In the impact mechanism 26, if the rotational torque of the hammer 27 is smaller than the load torque for rotating a fastener such as a screw to the workpiece, the rotational force of the spindle 28 applied from the motor 1 is the ball 32. Is transmitted to the hammer 27 via the cam groove 28a and the cam groove 27a, and the spindle 28 and the hammer 27 start to rotate together. The spindle 28 and the hammer 27 are relatively twisted, and the hammer 27 is moved backward along the spindle cam groove 28a while compressing the spring 29 in the right direction of the drawing while the spring 29 is twisted. When the hammer 27 gets over the height of the anvil protrusion 30a from the point of time away from the coupling with the protrusion 30a, the engagement with the anvil 30 is released. Further, the hammer 27 is urged by the spring 29 and the guide by the cam groove 28a, and advances while moving in the left direction of the drawing. The hammer convex portion (striking portion) 27a rotates the anvil convex portion 30a of the front anvil 30. Gives impact torque. As will be described later, this impact torque is transmitted to a tip tool (for example, a driver bit) (not shown) attached to the tip tool holding portion 31 of the anvil 30, and further, a rotational impact torque from the driver bit to the fastener screw. And screwing or tightening to the workpiece. Since the hammer convex portion 27a and the anvil convex portion 30a are again engaged with each other, the hammer 27 starts to move backward again and the hitting operation is repeated.

  Next, the inverter circuit unit 2 and the control circuit unit 3 of the brushless DC motor 1 will be described with reference to FIG.

  The brushless DC motor 1 is a three-phase brushless DC motor in this embodiment. The brushless DC motor 1 is an inner rotor type, and detects a rotational position of a rotor (magnet rotor) 1b configured by embedding a permanent magnet (magnet) including a pair of N poles and S poles. Therefore, based on the position detection signals of the three rotational position detection elements (Hall ICs) 5, 6, and 7 arranged every 60 ° and the Hall ICs 5, 6, and 7 constituting the rotational position detection element, an electrical angle of 120 ° And the armature winding 1d composed of the three-phase windings U, V, and W of the star-connected stator 1c that is controlled in the current supply period. The rotational position detecting means (5, 6, 7) of the rotor 1b of the brushless DC motor 1 detects the induced electromotive voltage (1) of the stator winding 1d in addition to the electromagnetic coupling detection by the Hall IC as described above. A sensorless system in which the rotor position is detected by extracting the back electromotive force as a logic signal through a filter may be employed.

  The inverter unit (power converter) 2 is built in parallel between six insulated gate bipolar transistors (IGBTs) Q1 to Q6 connected in a three-phase bridge form, and between the collectors and emitters of the transistors Q1 to Q6. And a connected flywheel diode (not shown). The gates of the six transistors Q1 to Q6 connected in a bridge are connected to an inverter drive unit (interface unit) 8a, and the collectors or emitters of the six transistors Q1 to Q6 are star-connected armature windings U. , V and W. As a result, the six transistors Q1 to Q6 perform a switching operation according to the switching element drive signals (drive signals such as H4, H5, and H6) input from the inverter drive unit 8a, and are applied to the inverter unit 2. 4 is supplied to the armature windings U, V, and W as three-phase (U-phase, V-phase, and W-phase) voltages Vu, Vv, and Vw.

  In this case, among the switching element drive signals (three-phase signals) for driving the gates of the six transistors Q1 to Q6, the three negative power supply side transistors Q4, Q5, and Q6 are connected to the pulse width modulation signal (PWM signal) H4. , H5 and H6, and the pulse width (duty ratio) of the PWM signal is changed based on the detection signal of the trigger push-in amount d (see FIG. 4) of the trigger switch unit 13 by the control circuit unit 3 described later. Thus, the power to the motor 1 is adjusted to control the start-up and speed of the motor. The PWM signal is supplied to the switching element group on either one of the positive power supply side switching elements Q1 to Q3 or the negative power supply side switching elements Q4 to Q6 of the inverter unit 2, and the switching element is switched at high speed, thereby obtaining a result. Thus, the power supplied from the DC voltage of the battery pack 4 to the armature windings U, V, W is supplied. In the present embodiment, as described above, the PWM signal is supplied to the negative power supply side switching element groups Q4 to Q6. Therefore, the number of revolutions of the motor 1 can be controlled by adjusting the power supplied to each armature winding U, V, W by controlling the pulse width of the PWM signal.

  Although not shown, the control circuit unit 3 includes a CPU for outputting a drive signal based on the processing program and data, a ROM for storing the processing program and control data, a RAM for temporarily storing the data, and a timer. It is comprised by the microcomputer containing etc. Functionally, a drive signal forming unit (including a CPU and a memory) 8 for outputting a control signal and a PWM signal of the inverter unit 2 and an inverter unit 2 for driving the inverter unit 2 based on an output signal of the drive signal forming unit 8 Inverter driving unit 8a, trigger pressing amount detection unit 10 for detecting trigger pressing amount d based on an output signal (potential meter voltage signal) Vt that responds to the operation amount (trigger pressing amount) of the trigger switch unit 13, trigger pressing In response to the trigger pressing amount detected by the amount detection unit 10, the applied voltage of the brushless DC motor 1, that is, the applied voltage setting unit 9 for setting the duty ratio of the output PWM signal of the inverter drive unit 8a, To set the rotation direction of the motor 1 by detecting the forward rotation or reverse rotation operation by the reverse switching lever 14 (see FIG. 1). Based on the rotational direction setting unit 11 and the output signals of the three rotational position detecting elements (Hall ICs) 5, 6, and 7, the relative positions of the armature windings U, V, and W of the rotor 1b and the stator 1c And a rotational position detecting unit 12 for detecting.

  A drive signal forming unit (including a CPU and a memory) 8 forms a drive signal for alternately switching predetermined switching elements Q1 to Q6 based on output signals from the rotation direction setting unit 11 and the rotor position detection unit 12. And output to the inverter drive unit 8a. Thereby, predetermined windings (U, V, W) of the armature winding 1d are alternately energized to rotate the rotor 1b in the set rotation direction. In this case, based on the output control signal (data) of the applied voltage setting unit 9, the drive signal applied to the negative power supply side switching elements Q4 to Q6 of the inverter unit 2 is output as a PWM modulation signal. Of course, as described above, the PWM modulation signal may be applied to the positive power supply side switching elements Q1 to Q3 instead of being applied to the negative power supply side switching elements Q4 to Q6.

  The PWM signal is generated by the drive signal forming unit 8 in advance by storing necessary control data in the ROM memory, and reading out according to the clock signal and using it as PWM generation data. According to the present invention, as will be described later, the relationship between the trigger push-in amount (voltage output Vt) d of the trigger switch unit 13 and the PWM signal duty ratio DUTY as shown in FIG. The pulse width (duty ratio) of the PWM signal is varied in response to the output control signal of the applied voltage setting unit 9.

  The configuration example of the trigger switch unit 13 is a direction in which the trigger operation unit 13a of the trigger switch unit 13 faces the trigger pushing direction by a spring force, as shown in the structural diagram (a) and the circuit function diagram (b) of FIG. Is being energized. By gripping the trigger operation portion 13a in the trigger pushing direction (inward direction of the handle housing portion 21b) against the spring force, the movable terminal (sliding terminal) Tm of the potentiometer VR moves, and from the movable terminal Tm of the potentiometer VR. The detected voltage Vt is a high voltage. As a result, the pushing amount d of the trigger switch 13 is converted into the movable terminal voltage Vt. The solid line in FIG. 4 shows the relationship between the trigger push-in amount d and the movable terminal voltage Vt of the potentiometer VR1. As indicated by the broken line in FIG. 4, the movable terminal voltage Vt may be configured to decrease with respect to the trigger switch pressing amount d.

  In the above configuration, according to the present invention, the applied voltage setting unit 9 stores the trigger push-in amount d vs. PWM duty ratio DUTY characteristic as shown in FIG. The PWM duty ratio DUTY indicates the duty ratio of the pulse width of the PWM signals H4, H5, and H6 output from the inverter driving unit 8a to the gates of the negative power supply side switching elements Q4 to Q6. In other words, to drive the armature windings (U, V, W) with an electrical angle of 120 °, the gate drive signals H4, H5, H6 supplied to the gates of the switching elements (Q4 to Q6) are subjected to pulse width modulation. The duty ratio of the pulse width of the PWM signal is shown.

  The trigger push-in amount d vs. PWM duty ratio DUTY characteristic shown in FIG. 5A is experimentally obtained in advance from the viewpoint of the operability and work efficiency of the tip tool and stored in the memory. In the characteristics shown in FIG. 5A, the upper limit duty ratio DUTYmax and the lower limit duty ratio DUTYmin are the upper limit speed N2 and the lower limit speed N1 in the trigger push-in amount d versus the motor speed N characteristics shown in FIG. It corresponds to the duty ratio for controlling to. The characteristic shown in FIG. 5B is experimentally obtained in advance from the viewpoint of the operability and work efficiency of the tip tool and stored in the memory unit, similarly to the characteristic shown in FIG.

  In the characteristic shown in FIG. 5B, in the first pushing range (low speed pushing range) d1 (for example, 3 mm) where the trigger pushing amount d of the trigger operating portion 13a is equal to or less than the first pushing amount D1, the motor 1 The lower limit rotational speed N1 (for example, 125 rpm) necessary for transmitting the rotational force to the load of the tip tool, and the upper limit rotational speed N2 (for example, the limit of operability such as positioning of the tip tool). , 250 rpm), the duty ratio of the PWM modulation signal is increased so as to increase at a predetermined first rotational speed increase rate, and the duty ratio DUTYmax (for example, 10%) in FIG. And DUTYmin (for example, 5%).

  Further, as shown in FIG. 5 (b), the trigger pushing amount d of the trigger operating portion 13a exceeds the first pushing amount D1 and reaches the maximum pushing amount Dm (for example, 12.5 mm). In the push range (high range push range) d2 (for example, 9.5 mm), the rotation speed N of the motor 1 is within the second rotation speed range of the upper limit rotation speed N2 and the full speed rotation speed Nm (for example, 2500 rpm). , The trigger shown in FIG. 5 (a) so as to increase at a second rotational speed increase rate (ΔN2 / ΔD2) higher than the first rotational speed increase rate (ΔN1 / ΔD1) in the first pushing range d1. In response to the pushing amount d, the duty ratio (DUTY) of the PWM signal is controlled. That is, when the trigger pressing amount d of the trigger operation unit 13a is in the first pressing range (low-speed range pressing range) d1, the motor rotation speed N is set to a low range between N1 and N2, and operability such as positioning is performed. When the trigger push-in amount d is in the second push-in range (high-speed push-in range) d2, the rate of increase in motor rotation speed N (ΔN2 / ΔD2) is set to the motor rotation speed N in the first push-in range d1. To increase the work efficiency such as screw tightening work.

  In the above embodiment, the motor rotation speed N with respect to the trigger pressing amount d in the first pressing range d1 of the trigger operation unit 13a is the upper limit rotation speed N2 and the lower limit as shown in FIGS. 6 (a) and (b). The duty ratio DUTY of the PWM signal may be controlled to be constant so that the rotation speed is constant within the range of the rotation speed N1.

  As shown in FIG. 4, the trigger push-in amount d is detected by being converted into an electric amount as a terminal voltage Vt by the potentiometer VR. For example, the detection voltage Vt at the maximum push-in amount Dm is set to 5V. The The applied voltage setting unit 9 corresponds to the output voltage Vt of the potentiometer VR based on the trigger pressing amount d of the trigger switch unit 13 according to the characteristics shown in FIG. 5A or FIG. 6A stored in advance. The duty ratio DUTY of the PWM signal is output.

  In the above configuration, when the trigger operation portion 13a of the trigger switch 13 of the electric power tool 50 is gripped, the motor 1 starts rotating within the first push range d1 shown in FIG. When d is held below D1, negative power supply side switching elements Q4 to Q6 (or positive power supply side switching elements Q1 to Q3) are controlled so that the duty ratio of the pulse width of PWM modulation signals H4 to H6 is in the range of DUTYmin to DUTYmax. Therefore, the rotation speed N of the motor 1 is controlled in the range of the upper limit rotation speed N2 to the lower limit rotation speed N1.

  Therefore, it is advantageous to perform an operation at the start of work such as a positioning operation for a workpiece of a tip tool such as a driver bit. For example, if PWM control is performed at DUTYmin or higher, it is possible to prevent the applied voltage applied to the armature winding 1d from being reduced and to set the rotational speed N to the lower limit rotational speed N1 or higher. As a result, the rotor 1a of the motor 1 can be prevented from being unable to rotate due to the influence of the load torque applied to the tip tool. On the other hand, if the PWM signal is DUTYmax or less, the applied voltage to the armature winding 1d can be prevented from becoming an excessive voltage, and the motor rotation speed N can be controlled to the upper limit rotation speed N2 or less. As a result, the rapid increase in the motor rotation speed can be prevented, and the problem that the tip tool of the electric tool is detached from the positioning location and the tip tool damages the workpiece can be prevented. That is, at the start of the trigger operation of the trigger switch 13, the PWM signal duty ratio DUTY is set within the range of DUTYmax to DUTYmin, thereby easily obtaining a low speed region effective for the operation of the low speed region pushing range d1 at the start of work. be able to.

  Further, if the conventional trigger control method as described above is followed, the rate of increase in the motor speed in the low speed region push range d1 becomes as high as that in the high speed region push range d2, so that the trigger push amount of the trigger switch 13 is increased. A delicate operation is required to keep d at a low rotational speed by reducing d. For this reason, trigger switch operation is difficult, and the problem that operation | movement of a tip tool will become unstable by the fluctuation | variation of trigger pushing amount will be caused. However, according to the trigger control system of the present invention, the brushless DC motor is operated in the low speed region where the rotational speed is N2 or less within the low speed region push range d1 where the trigger push amount d of the trigger switch 13 is from the push start to the predetermined push amount D1. 1 is controlled, it is possible to easily control the rotation of the motor in the low speed region by operating the trigger switch 13.

  When the trigger push amount d of the trigger switch 13 falls within the high speed range push range d2 that is equal to or greater than the predetermined push amount D1, the rate of increase in rotation with respect to the push amount increases, and the motor speed N is increased to the maximum speed Nm in a short time. Can be controlled. Thereby, working efficiency can be improved.

  As shown in FIG. 6, when the trigger pressing amount d of the trigger switch 13 is within the low speed region pressing range d1, the duty ratio of the pulse width of the PWM signal is controlled to be constant and the motor rotation speed is controlled at a constant speed. Since the rotation speed does not vary, the operability can be further improved.

  As will be apparent from the above description of the embodiment, according to the present invention, it is possible to easily control the rotational speed at the start of rotation of the motor and to improve the operability of the electric tool.

  In addition, although the above embodiment demonstrated the electric tool using a three-phase brushless DC motor, it can be applied also to the electric tool using a brushless DC motor other than three phases. Further, the present invention can be applied not only to an impact driver but also to an electric rotary tool such as an electric drill.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the scope of the invention. .

1 is an overall structural diagram of a power tool according to an embodiment of the present invention. The functional block diagram which shows the drive control system of the brushless DC motor in the electric tool shown in FIG. The structure figure (a) and functional block diagram (b) which showed the trigger switch part of the electric tool shown in Drawing 1. FIG. 4 is a characteristic diagram illustrating a relationship between a trigger push-in amount of the trigger switch unit illustrated in FIG. 3 and a movable terminal voltage. The characteristic view which shows the relationship between the trigger pushing amount of the trigger switch part shown in FIG. 3, and PWM duty ratio. FIG. 4 is another characteristic diagram showing the relationship between the trigger push-in amount of the trigger switch section shown in FIG. 3 and the PWM duty ratio.

Explanation of symbols

1: Brushless DC motor 1a: Rotor (magnet rotor)
1b: Permanent magnet 1c: Stator 1d: Stator winding 2: Inverter unit 3: Control circuit unit 4: Battery pack 5, 6, 7: Rotation position detection element (Hall IC)
8: Drive signal formation unit 8a: Inverter drive unit 9: Applied voltage setting unit 10: Trigger push-in amount detection unit 11: Rotation direction setting unit 12: Rotation position detection unit 13: Trigger switch 13a: Trigger operation unit 14: Forward / reverse switching Lever 21a: fuselage housing part 21b: handle housing part 22: power transmission mechanism part (reduction mechanism part) 23: planetary gear 24: ring gear 25: pinion gear 26: impact mechanism part 27: hammer 27a: hammer convex part 27b: hammer inner circumference Surface cam groove 28: Spindle 28a: Spindle outer peripheral surface cam groove 29: Spring 30: Anvil 30a: Anvil convex part 31: Tip tool holding part 32: Ball (steel ball)
50: Electric tool d1: First push range (low speed range push range)
d2: Second push range (high-speed push range) DUTYmax: Upper limit duty ratio DUTYmin: Lower limit duty ratio N1: Lower limit rotation speed N2: Upper limit rotation speed U, V, W: Three-phase stator winding

Claims (5)

An electric motor mounted in the housing part, a tip tool provided in the housing part that is rotationally driven by the electric motor, a trigger switch part provided in the housing part, and a trigger pushing amount of the trigger switch part In the electric tool having a control circuit unit for controlling the rotation speed of the electric motor from the rotation start to the full speed rotation speed,
The control circuit unit transmits the rotational force of the electric motor to the load of the tip tool in a first pressing range in which the trigger pressing amount of the trigger switch unit is equal to or less than the first pressing amount. In the first rotation speed range between the lower limit rotation speed of the first rotation speed and the upper limit rotation speed defined by the operability of the tip tool lower than the full speed rotation speed. Or in response to the trigger pressing amount so as to be a constant rotation speed, and
In the second pushing range in which the trigger pushing amount of the trigger switch unit exceeds the first pushing amount and reaches the maximum pushing amount, the rotation speed of the electric motor is set to the upper limit rotation speed and the full speed rotation speed. In response to the trigger push-in amount so as to increase at a second rotational speed increase rate higher than the first rotational speed increase rate in the first push-in range. An electric tool characterized by controlling.   The rotational speed of the electric motor is controlled to be a constant rotational speed in the first pushing range, and is controlled to be increased from the constant rotational speed to the full speed rotational speed in the second pushing range. The power tool according to claim 1.   The trigger push amount of the trigger switch unit is converted into a voltage level by a potentiometer, and the applied voltage of the electric motor is subjected to pulse width modulation by using the converted voltage as a control signal to control the rotation speed of the electric motor. The power tool according to claim 1 or 2, wherein the power tool is provided. A brushless DC motor having a rotor with a permanent magnet and a stator with a multi-phase armature winding, and a plurality of bridge-connected switching elements, and switching each DC voltage by switching DC voltage An inverter for supplying power to the armature winding, an inverter drive unit for driving the plurality of switching elements with a pulse width modulation signal, and a trigger for controlling the rotation speed of the brushless DC motor by a trigger pushing amount of a trigger operation A switch, a control circuit unit for controlling the rotation speed of the brushless DC motor from the rotation start to the full speed rotation speed based on a trigger pushing amount of the trigger switch unit, and a rotation transmission mechanism unit by the brushless DC motor. In an electric tool comprising a tip tool that is rotationally driven,
The control circuit unit transmits the rotational force of the electric motor to the load of the tip tool in a first pressing range in which the trigger pressing amount of the trigger switch unit is equal to or less than the first pressing amount. In the first rotation speed range between the lower limit rotation speed of the first rotation speed and the upper limit rotation speed defined by the operability of the tip tool lower than the full speed rotation speed. Or to control the duty ratio of the pulse width modulation signal that drives the plurality of switching elements in response to the trigger pressing amount so as to be a constant rotational speed, and
In the second pressing range in which the trigger pressing amount of the trigger switch unit exceeds the first pressing amount and reaches the maximum pressing amount, the rotation speed of the brushless DC motor is set to the upper limit rotation speed and the full speed rotation. In response to the trigger push-in amount so as to increase at a second rotational speed increase rate higher than the first rotational speed increase rate in the first push-in range within a second rotational speed range between And controlling a duty ratio of the pulse width modulation signal for driving the plurality of switching elements.   The control circuit unit includes an applied voltage setting unit that presets a change in the duty ratio of the pulse width modulation signal with respect to the trigger pressing amount of the trigger switch unit, and a drive signal forming unit is configured by an output of the application setting unit. The power tool according to claim 4, wherein the duty ratio of the pulse width modulation signal is varied by controlling.

Images