WO2016067811A1

WO2016067811A1 - Electrically powered device

Info

Publication number: WO2016067811A1
Application number: PCT/JP2015/077482
Authority: WO
Inventors: 和隆岩田
Original assignee: 日立工機株式会社
Priority date: 2014-10-31
Filing date: 2015-09-29
Publication date: 2016-05-06
Also published as: JPWO2016067811A1

Abstract

The purpose of the present invention is to provide an electrically powered device that can stably control a motor in a sensorless-driving scheme. An electrically powered device of the present invention comprises: a motor that has a rotor and a stator which has a winding; an induced voltage detection means that detects an induced voltage generated in the winding; and a motor control means that controls the motor on the basis of the induced voltage. The induced voltage detection means includes: a digital signal outputting means that outputs a digital signal that corresponds to the induced voltage to the motor control means; and an analog signal outputting means that outputs an analog signal that corresponds to the induced voltage to the motor control means.

Description

Electric equipment

The present invention relates to an electric device having a motor.

2. Description of the Related Art Conventionally, electric devices including a Hall element that detects a rotational position (rotational angle) of a rotor and a control unit that controls a motor based on the detected rotational position of the rotor have been widely used. In an electric device that controls a motor using such a Hall element, the Hall element must be installed in the vicinity of the rotor, and a cable connecting the Hall element and the control unit must be provided in the electric device. There was a problem that the score increased and the assemblability deteriorated. In order to solve the above problem, there has been proposed an electric device that employs a sensorless drive system that controls a motor without using a Hall element (Patent Document 1). In the electric device described in Patent Document 1, an induced voltage generated in the stator winding and a predetermined reference voltage are compared by using a comparator, so that a digital signal (2) corresponding to the direction (direction) of the induced voltage is compared. Value signal), and the motor is controlled by determining the rotational position of the rotor based on the digital signal.

JP-A-9-117186

In the electric device described above, when the rotor rotation speed is low (low rotation speed range, for example, when the motor starts driving), the induced voltage generated in the stator winding is low. The difference between the two becomes smaller, chattering, etc. occurs, the comparison by the comparator and the digital signal (binary signal) output as the comparison result may be inaccurate, and the motor control in the low rotation speed range is unstable There was a problem of becoming.

Therefore, an object of the present invention is to provide an electric device that can stably control a motor in a sensorless drive system.

In order to solve the above problems, the present invention provides a motor having a rotor, a stator having windings, induced voltage detection means for detecting an induced voltage generated in the windings, and the induced voltage based on the induced voltage. Motor control means for controlling a motor, and the induced voltage detection means outputs a digital signal corresponding to the induced voltage to the motor control means, and an analog signal corresponding to the induced voltage. There is provided an electric device having an analog signal output means for outputting to the motor control means.

According to such a configuration, a digital signal and an analog signal corresponding to the induced voltage can be output. For this reason, since the signal used for control of a motor can be selected suitably, a motor can be controlled more stably and favorably, and operativity can be improved. That is, in the sensorless driving method, the motor can be controlled stably. Moreover, since it is the structure which controls a motor based on the signal according to an induced voltage, it is not necessary to provide a Hall element in an electric equipment. Thereby, the number of parts can be reduced and assemblability can be improved.

In the above configuration, the motor control means selects either the digital signal or the analog signal according to the driving state of the motor, and controls the motor based on the selected signal. preferable.

According to such a configuration, the motor control means can select either a digital signal or an analog signal as a signal corresponding to the induced voltage used for controlling the motor according to the driving state. As a result, when the motor is controlled based on the digital signal, the control may be unstable (for example, when the motor starts driving). The motor can be controlled based on the analog signal. For this reason, the motor can be controlled more stably and satisfactorily and the operability can be improved as compared with the configuration in which the signal used for controlling the motor cannot be appropriately selected from both signals according to the driving state. Can be made.

In the above configuration, the driving state detecting means includes a rotational speed detecting means for detecting the rotational speed of the rotor, and the motor control means is either one of the digital signal and the analog signal according to the rotational speed. It is preferable to control the motor based on one of the selected signals.

According to such a configuration, a digital signal and an analog signal corresponding to the induced voltage according to the rotational speed state of the rotor (rotor rotational speed), which is a factor that has a great influence on the stability of the motor control, among driving states. Since one of the signals can be selected and the motor can be controlled based on the selected one of the signals, the motor control can be made more stable.

The motor control means controls the motor based on the analog signal when the rotational speed is equal to or lower than the rotational speed threshold, and based on the digital signal when the rotational speed is larger than the rotational speed threshold. It is preferable to control the motor.

According to such a configuration, when the motor is controlled based on a digital signal corresponding to the induced voltage, in a driving state where the control may become unstable, that is, in a state where the rotational speed of the rotor is low (low rotational speed state) When the motor is controlled based on the analog signal and the motor is controlled based on the analog signal corresponding to the induced voltage, the control may become unstable, that is, in a high rotational speed state (high rotational speed state) The motor can be controlled based on the digital signal. Therefore, the motor can be controlled more stably.

Further, it is preferable that the motor control means controls the motor based on the analog signal when the driving of the motor is started.

According to such a configuration, the motor can be reliably controlled based on the analog signal in a low rotational speed state at the start of driving of the motor. That is, in the low rotational speed state at the start of driving of the motor, it is possible to reliably avoid the motor control based on the digital signal that may cause the motor control to become unstable. Therefore, the motor can be controlled more stably.

Further, it is preferable that the motor control means controls the motor based on the analog signal until a predetermined time elapses from the start of driving of the motor.

According to such a configuration, the motor can be controlled based on the analog signal from when the motor starts to be driven until a predetermined time elapses. That is, in the low rotational speed state at the start of driving of the motor, it is possible to more reliably avoid the motor control based on the digital signal that may cause the motor control to become unstable in this state. Therefore, the motor can be controlled more stably and satisfactorily.

Moreover, it is preferable that the motor control means controls the motor based on the digital signal after controlling the motor based on the analog signal.

According to such a configuration, for example, in the low rotational speed state at the time of starting the motor (at the start of driving), the motor control based on the digital signal that may cause the motor control to become unstable in the state is more reliably performed. It can be avoided. Therefore, the motor can be controlled more stably and satisfactorily.

In order to solve the above-described problems, the present invention further includes a motor having a rotor and a stator having a winding, a trigger for instructing the start of the motor, and an induced voltage for detecting an induced voltage generated in the winding. Detection means and motor control means for controlling the motor based on the induced voltage, the induced voltage detection means comprising: a digital signal output means for outputting a digital signal corresponding to the induced voltage; and the induced voltage Analog signal output means for outputting an analog signal corresponding to the motor signal, and the motor control means controls the motor based on the analog signal when the trigger is operated, and then based on the digital signal. An electric device characterized by controlling the motor is provided.

According to the electric device of the present invention, the motor can be stably controlled in the sensorless drive system.

It is a partial section side view of an impact driver by an embodiment of the invention. 1 is a circuit diagram including a block diagram showing a drive control system of an impact driver according to an embodiment of the present invention. It is a figure which shows the structure of the U-phase signal output circuit with which the induced voltage detection circuit part and the circuit part of the impact driver by embodiment of this invention are provided. It is a figure showing each voltage signal and the voltage waveform in a state where the rotor of the impact driver according to the embodiment of the present invention is rotating at the maximum number of revolutions, (a) is a figure showing the waveform of the U-phase corresponding voltage, (B) is a figure which shows the waveform of a U-phase analog signal, (c) is a figure which shows the waveform of a U-phase digital signal. It is a flowchart which shows control of the motor by the control part of the impact driver by embodiment of this invention. It is a figure which shows the timing chart of the voltage of each part at the time of controlling a motor using the control flow by the control part of the control part of the impact driver by embodiment of this invention, a voltage signal, rotation speed, and a duty ratio. The figure which shows the waveform of a phase corresponding | compatible voltage, (b) is a figure which shows the waveform of a U-phase analog signal, (c) is a figure which shows the waveform of a U-phase digital signal, (d) is a figure which shows the rotation speed of a rotor, e) is a diagram showing the duty ratio. It is a figure which shows the voltage signal of each part in case the rotor in the conventional electrically-driven apparatus is a low speed state, (a) is a figure which shows the waveform of the signal according to the induced voltage input into a comparator, (b) is It is a figure which shows the waveform of the digital signal which a comparator outputs.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, the case where the present invention is applied to a cordless type impact driver will be described as an example.

In the following description, when a specific numerical value is mentioned, for example, when referring to an electrical angle such as “90 °”, not only the case where the numerical value completely coincides with the numerical value, but also substantially the same as the numerical value. Including cases. In addition, when referring to the positional relationship, for example, when referring to parallel, orthogonal, opposite, etc., not only when it is completely parallel, orthogonal, opposite, etc., but also substantially parallel, substantially orthogonal, substantially opposite, etc. Including some cases.

As shown in FIG. 1, an impact driver 1, which is an example of an electric device according to an embodiment of the present invention, includes a housing 2, a motor 3, a drive circuit unit 4, a cooling fan 5, a power transmission unit 6, and a control board. Part 7 is provided. FIG. 1 is a partial cross-sectional side view of the impact driver 1 and shows the impact driver 1 with the battery pack P attached. In FIG. 1, the direction in which the power transmission unit 6 is provided with respect to the motor 3 is defined as the front direction, and the direction opposite to the front direction is defined as the rear direction. Further, the direction in which the control board portion 7 is provided with respect to the motor 3 is defined as a downward direction, and the direction opposite to the downward direction is defined as an upward direction. Further, when the impact driver 1 is viewed from behind, the left is defined as the left direction and the right is defined as the right direction.

The housing 2 forms an outline of the impact driver 1, and includes a motor housing 21, a handle housing 22, and a board housing portion 23.

The motor housing 21 has a substantially cylindrical shape extending in the front-rear direction, and accommodates the motor 3, the drive circuit unit 4, the cooling fan 5, and the power transmission unit 6 therein. A hammer case 21 A is disposed inside the front side of the motor housing 21. The hammer case 21A has a substantially funnel shape whose diameter gradually decreases toward the front, and an opening 21a is formed at a front end portion thereof.

The motor 3 is housed inside the rear side of the motor housing 21 and has a rotating shaft 31, a rotor 32, and a stator 33. The rotating shaft 31 is a shaft extending in the front-rear direction, and is rotatably supported by the motor housing 21 via a bearing. The rotor 32 is a rotor having a plurality of permanent magnets 32 A, and is configured to be fixed to the rotating shaft 31 and rotate integrally with the rotating shaft 31. The stator 33 is a stator having a stator winding 33A. The stator winding 33 A is disposed so as to surround the rotor 32.

The drive circuit unit 4 is an inverter circuit for supplying a drive current to the stator winding 33 A of the motor 3, and is located on the rear surface of the stator 33. Details of the drive circuit unit 4 will be described later.

The cooling fan 5 is a centrifugal fan, and is fixed coaxially with the rotating shaft 31 at the front side portion of the rotating shaft 31. The cooling fan 5 generates cooling air in the motor housing 21 by its rotation, and cools the motor 3, the drive circuit unit 4, and the like.

The power transmission unit 6 is housed in the hammer case 21 A and includes a speed reduction mechanism 61, an impact mechanism 62, and an anvil part 63. The speed reduction mechanism 61, the impact mechanism 62, and the anvil part 63 are arranged in that order from the motor 3 side in the axial direction (front-rear direction) of the rotating shaft 31.

The reduction mechanism 61 includes a sun gear 61A that rotates integrally with the rotary shaft 31, a planetary gear 61B that meshes with the sun gear 61A, and a ring gear 61C that meshes with the planetary gear 61B. As the sun gear 61A rotates, the planetary gear 61B goes around the sun gear 61A.

The impact mechanism 62 has a spindle 62A and a hammer 62B. The spindle 62A rotates at a position coaxial with the rotation shaft 31 by the revolving motion of the planetary gear 61B. The hammer 62B is disposed on the spindle 62A so as to be slidable back and forth, and includes a pair of collision portions 62C at the front end thereof. Further, the hammer 62B is configured to be given a rotational striking force while being urged forward by a spring 62D, and can move backward against the urging force of the spring 62D.

The anvil portion 63 is disposed in front of the hammer 62B, is rotatably supported on the hammer case 21A at a position coaxial with the spindle 62A, and includes a tip tool holding portion 63A and an anvil 63B. The tip tool holding portion 63A is formed in a substantially cylindrical shape and protrudes forward from the opening 21a of the hammer case 21A. The tip tool holding portion 63A has a holding hole 63a into which a tip tool (not shown) is inserted in the front-rear direction, and a chuck 63C that holds a bit (not shown) at the front end portion of the tip tool holding portion 63A. Is provided. Here, the tip tool is, for example, a driver bit or a bolt tightening bit.

The anvil 63B is configured behind the tip tool holding portion 63A and integrally with the tip tool holding portion 63A in the hammer case 21A. Further, the anvil 63B has a pair of impacted parts 63D arranged at symmetrical positions with respect to the rotation centers of the anvil 63B and the tip tool holding part 63A.

The handle housing 22 has a substantially cylindrical shape extending in the vertical direction, and an upper end thereof is connected to the motor housing 21. The handle housing 22 includes a switch trigger 22A and a switch mechanism 22B. The switch trigger 22 A is provided on the front side of the upper end of the handle housing 22 and is connected to the switch mechanism 22 B inside the handle housing 22. When the switch trigger 22A is pushed, the motor 3 is activated. That is, the switch trigger 22 A functions as a trigger that instructs activation of the motor 3. The switch mechanism 22B is connected to the control board unit 7. When the switch trigger 22A is pushed, the switch mechanism 22B outputs a trigger signal corresponding to the pushing amount (operation amount) of the switch trigger 22A to the control board unit 7.

The board housing part 23 is connected to the lower end of the handle housing 22, and the control board part 7 connected to the switch mechanism 22 B and the drive circuit part 4 is housed therein. The control board unit 7 controls the motor 3 by outputting a drive signal for controlling the motor 3 to the drive circuit unit 4 based on various signals input from the switch mechanism 22B and the like. Moreover, the lower end part of the board | substrate accommodating part 23 is comprised so that the battery pack P can be attached or detached. Details of the control board 7 will be described later.

The battery pack P is detachably attached to the lower end portion of the substrate housing portion 23, and is a lithium ion secondary battery, a nickel-cadmium secondary battery, or the like serving as a power source for the motor 3, the drive circuit portion 4, and the control substrate portion 7. The battery set which consists of is accommodated. The battery set is configured to be electrically connected to the drive circuit unit 4 and the like in a state where the battery pack P is mounted on the substrate housing unit 23.

Next, the operation of the impact driver 1 will be described when tightening screws. When the operator pulls the switch trigger 22 A, a signal is output from the switch mechanism 22 B to the control board unit 7, and the control board unit 7 starts driving control of the motor 3. When the motor 3 is driven and controlled by the control board 7, the rotating shaft 31 and the rotor 32 of the motor 3 rotate integrally with the number of rotations corresponding to the pushing amount of the switch trigger 22 A. At the same time, the cooling fan 5 also rotates, and outside air is taken into the motor housing 21 from an intake hole (not shown) formed in the motor housing 21. The outside air cools the motor 3 and the drive circuit unit 4 and is discharged to the outside through an exhaust hole (not shown) formed in the motor housing 21.

When the rotary shaft 31 rotates, the rotational speed of the rotary shaft 31 is reduced by the speed reduction mechanism 61 and transmitted to the spindle 62A. When the rotational force is transmitted to the spindle 62A, the spindle 62A and the hammer 62B rotate together. When the hammer 62B rotates, the one colliding part 62C and one colliding part 63D of the anvil part 63 collide, and at the same time, the other colliding part 62C and the other colliding part 63D collide. Thereby, the rotational force of the hammer 62B is transmitted to the anvil 63B, and a hit is given to the anvil 63B.

In addition, after the collision between the collision part 62C and the collided part 63D, the spindle 62A and the hammer 62B rotate integrally with the collision part 62C and the collided part 63D being in contact with each other, and the rotational torque of the hammer 62B is a predetermined value. Is exceeded, the spindle 62A starts to rotate relative to the hammer 62B. When the spindle 62A and the hammer 62B start relative rotation, the hammer 62B moves backward while rotating against the urging force of the spring 62D. When the collision part 62C gets over the collided part 63D, the hammer 62B moves forward at high speed while rotating due to the release of the elastic energy stored in the spring 62D. Due to the movement of the hammer 62B, the collision part 62C and the colliding part 63D collide again. In this way, by repeating the collision between the collision part 62C and the collided part 63D and the retraction of the hammer 62B, a rotational striking force is applied to the tip tool mounted on the tip tool holding part 63A of the anvil part 63, and the screw is tightened. tighten. The motor 3 stops when the operator releases the switch trigger 22A.

Next, the configuration of the motor 3 and the drive control system of the motor 3 will be described with reference to FIG. FIG. 2 is a circuit diagram including a block diagram showing a drive control system of the impact driver 1.

As shown in FIG. 2, the motor 3 is a DC brushless motor, and the rotor 32 of the motor 3 includes two sets of permanent magnets 32 A each having a north pole and a south pole. The stator winding 33 A of the stator 33 includes star-connected three-phase coils U, V, and W, and the coils U, V, and W are connected to the drive circuit unit 4. The stator winding 33A is an example of the winding of the present invention.

The drive circuit unit 4 includes six FETs Q1 to Q6 connected in a three-phase bridge format. The connection point 4a between the source of the FET Q1 and the drain of the FET Q4 is connected to one end of the coil U, the connection point 4b between the source of the FET Q2 and the drain of the FET Q5 is connected to one end of the coil V, and the source of the FET Q3 and the drain of the FET Q6 The connection point 4c is connected to one end of the coil W, and the gates of the six FETs Q1 to Q6 are connected to the control substrate section 7. The six FETs Q1 to Q6 perform a switching operation that is repeatedly turned on / off by a drive signal input from the control board 7 to each gate. Moreover, the connection point 4a, the connection point 4b, and the connection point 4c are connected to the control board part 7 by the connection line 4A, the connection line 4B, and the connection line 4C, respectively.

The control board unit 7 is connected to the switch mechanism 22 B and the drive circuit unit 4, and includes an induced voltage detection circuit unit 71, a control signal output circuit 75, and a control unit 76.

The induced voltage detection circuit unit 71 is connected to one end of each of the coils U, V, and W of the stator winding 33A by the connection line 4A, the connection line 4B, and the connection line 4C, and the stator winding 33A is rotated by the rotation of the rotor 32. And a digital signal corresponding to the induced voltage (induced voltage digital signal) and a digital signal corresponding to the induced voltage to the control unit 76. The induced voltage detection circuit unit 71 functions as an induced voltage detection unit of the present invention.

The induced voltage detection circuit unit 71 includes a U-phase signal output circuit 72, a V-phase signal output circuit 73, and a W-phase signal output circuit 74. The U-phase signal output circuit 72 detects an induced voltage (U-phase induced voltage) generated in the coil U, an analog signal (U-phase analog signal) corresponding to the U-phase induced voltage, and a digital signal corresponding to the U-phase induced voltage. This is a circuit that outputs (U-phase digital signal) to the controller 76. The V-phase signal output circuit 73 detects an induced voltage (V-phase induced voltage) generated in the coil V, an analog signal (V-phase analog signal) corresponding to the V-phase induced voltage, and a digital signal corresponding to the V-phase induced voltage. This is a circuit that outputs (V digital signal) to the controller 76. The W-phase signal output circuit 74 detects an induced voltage (W-phase induced voltage) generated in the coil W, an analog signal (W-phase analog signal) corresponding to the W-phase induced voltage, and a digital signal corresponding to the W-phase induced voltage. This is a circuit that outputs (W-phase digital signal) to the controller 76.

Here, the configuration of the induced voltage detection circuit unit 71 and the configuration of the U-phase signal output circuit 72, the V-phase signal output circuit 73, and the W-phase signal output circuit 74 provided in the circuit unit will be described with reference to FIG. The configurations of the U-phase signal output circuit 72, the V-phase signal output circuit 73, and the W-phase signal output circuit 74 are substantially the same. Therefore, in the following description, the configuration of the U-phase signal output circuit 72 will be described as an example. The description of the configuration of the V-phase signal output circuit 73 and the W-phase signal output circuit 74 will be simplified. FIG. 3 is a diagram illustrating a configuration of the induced voltage detection circuit unit 71 and the U-phase signal output circuit 72 provided in the circuit unit. In FIG. 3, the V-phase signal output circuit 73 and the W-phase signal output circuit 74 are omitted in order to avoid complication of the drawing.

As shown in FIG. 3, the induced voltage detection circuit unit 71 includes a resistor 71A, a resistor 71B, a resistor 71C, a resistor 71D, and a resistor 71E. One end of each of the

resistors

71A, 71B, and 71C is commonly connected at the neutral point 71a. In other words, the

resistors

71A, 71B, and 71C are star-connected. The other end of the resistor 71A is connected to one end of the coil U of the stator winding 33A via the connection line 4A and the connection point 4a, and the other end of the resistor 71B is connected to the coil V via the connection line 4B and the connection point 4b. The other end of the resistor 71C is connected to one end of the coil W of the stator winding 33A via the connection line 4C and the connection point 4c.

In this way, the

resistors

71A, 71B, and 71C are star-connected, and the other ends of the

resistors

71A, 71B, and 71C are connected to one ends of the coils U, V, and W, respectively. The voltage drop of 71A corresponds to the U-phase induced voltage, the voltage drop of resistor 71B corresponds to the V-phase induced voltage, and the voltage drop of resistor 71C corresponds to the W-phase induced voltage. In other words, the potential difference between the connection point connecting one end of each of the

resistors

71A, 71B and 71C, that is, the neutral point 71a and the U-phase voltage point 71b provided at the other end of the resistor 71A is The potential difference between the neutral point 71a and the V-phase voltage point 71c provided at the other end of the resistor 71B corresponds to the V-phase induced voltage and is provided at the neutral point 71a and the other end of the resistor 71C. The potential difference from the W-phase voltage point 71d corresponds to the W-phase induced voltage.

The resistor 71D and the resistor 71E are connected in series between the neutral point 71a and the ground, and divide the voltage at the neutral point 71a. The connection point between the resistor 71D and the resistor 71E, that is, the voltage at the neutral point voltage dividing point 71e is a value obtained by dividing the voltage at the neutral point 71a by the resistor 71D and the resistor 71E.

The U-phase signal output circuit 72 includes a U-phase analog signal output circuit 8 that outputs a U-phase analog signal and a U-phase digital signal output circuit 9 that outputs a U-phase digital signal.

The U-phase analog signal output circuit 8 includes a voltage dividing circuit 81 and a differential amplifier circuit 82. The voltage dividing circuit 81 is a circuit that divides the voltage of the U-phase voltage point 71b, and includes a resistor 81A and a resistor 81B connected in series between the U-phase voltage point 71b and the ground. The connection point between the resistor 81A and the resistor 81B, that is, the voltage at the U-phase voltage dividing point 81a is a value obtained by dividing the voltage at the U-phase voltage point 71b by the resistor 81A and the resistor 81B. The resistance value of the resistor 81A is set to the same value as the resistance value of the resistor 71D, and the resistance value of the resistor 81B is set to the same value as the resistance value of the resistor 71E. Therefore, the potential difference between the neutral point voltage dividing point 71e and the U phase voltage dividing point 81a, that is, the voltage at the U phase voltage dividing point 81a based on the neutral point voltage dividing point 71e is proportional to the U phase induced voltage. Voltage (voltage corresponding to U phase).

The differential amplifier circuit 82 includes an operational amplifier 82A, a resistor 82B, a resistor 82C, a resistor 82D, and a capacitor 82E. The non-inverting input terminal of the operational amplifier 82A is connected to the U-phase voltage dividing point 81a via the resistor 82B, and the inverting input terminal is connected to the neutral point voltage dividing point 71e via the resistor 82C. The output terminal of the operational amplifier 82A is connected to the A / D port of the control unit 76 and the U-phase digital signal output circuit 9, and the resistor 82D and noise are reduced between the output terminal and the inverting input terminal. A capacitor 82E serving as a low-pass filter is connected in parallel.

The differential amplifier circuit 82 amplifies and offsets the voltage of the U-phase voltage dividing point 81a with respect to the neutral point voltage dividing point 71e, that is, the U-phase-corresponding voltage to the input level of the control unit 76, and reduces noise. The analog signal (U-phase analog signal) is output to the A / D input port of the control unit 76 and the U-phase digital signal output circuit 9. That is, the differential amplifier circuit 82 outputs an analog signal (U-phase analog signal) corresponding to the U-phase induced voltage to the control unit 76 and the U-phase digital signal output circuit 9.

The U-phase digital signal output circuit 9 includes a voltage dividing circuit 91 and a comparator 92. The voltage dividing circuit 91 is a circuit that divides the reference voltage Vcc, and includes a resistor 91A and a resistor 91B connected in series between the reference voltage Vcc and the ground. The resistance value of the resistor 91A and the resistance value of the resistor 91B are set to the same value, and the connection point between the resistor 91A and the resistor 91B, that is, the voltage at the reference voltage dividing point 91a is a half of the reference voltage Vcc. Is the voltage. In the present embodiment, the reference voltage Vcc is 5V, and the voltage at the reference voltage dividing point 91a is 2.5V.

The comparator 92 is a circuit that compares voltages (voltage signals) input to the inverting input terminal and the non-inverting input terminal. The inverting input terminal of the comparator 92 is connected to the reference voltage dividing point 91a of the voltage dividing circuit 91, and the voltage (reference voltage signal) of the reference voltage dividing point 91a is input to the inverting input terminal. The non-inverting input terminal of the comparator 92 is connected to the output terminal of the operational amplifier 82A, and a U-phase analog signal is input to the non-inverting input terminal. The output terminal of the comparator 92 is connected to the input port of the control unit 76.

The comparator 92 compares the reference voltage signal and the U-phase analog signal, and outputs a digital signal (binary signal) corresponding to the direction of the U-phase induced voltage to the control unit 76. Specifically, when the U-phase analog signal is larger than the reference voltage signal, a high signal is output to the input port of the control unit 76, and when the U-phase analog signal is equal to or lower than the reference voltage signal, the control unit 76 is low. Outputs a signal (does not output a voltage signal). In other words, the comparator 92 outputs a digital signal (U-phase digital signal) corresponding to the U-phase induced voltage to the control unit 76.

Note that the V-phase signal output circuit 73 is connected to the V-phase voltage point 71c and the neutral point voltage dividing point 71e, and has the same configuration as the U-phase analog signal output circuit 8 except for the connection configuration. A V-phase digital signal output circuit having the same configuration as the signal output circuit and the U-phase digital signal output circuit 9 is provided. The W-phase signal output circuit 74 is connected to the W-phase voltage point 71d and the neutral point voltage dividing point 71e, and has the same configuration as the U-phase analog signal output circuit 8 except for the connection configuration. A signal output circuit and a W-phase digital signal output circuit having the same configuration as the U-phase digital signal output circuit 9 are provided. That is, the control unit 76 receives a total of six signals including a U-phase analog signal, a U-phase digital signal, a V-phase analog signal, a V-phase digital signal, a W-phase analog signal, and a W-phase digital signal. The U-phase analog signal output circuit 8, the V-phase analog signal output circuit, and the W-phase analog signal output circuit function as analog signal output means of the present invention. The U-phase digital signal output circuit 9, the V-phase digital signal output circuit, and the W-phase digital signal output circuit function as the digital signal output means of the present invention.

Here, the U-phase compatible voltage, the U-phase analog signal, and the U-phase digital signal will be described with reference to FIG. The U-phase induced voltage draws a substantially sine wave as the rotor 32 rotates. This is because when the rotor 32 rotates, the N pole and S pole of the permanent magnet 32A of the rotor 32 alternately pass through the vicinity of the coil U and the magnetic force penetrating the coil U changes periodically. FIG. 4 is a diagram showing the waveform of each voltage signal and voltage in a state where the rotor 32 is rotating at the maximum rotational speed, (a) is a diagram showing the waveform of the U-phase corresponding voltage, and (b) is U The figure which shows the waveform of a phase analog signal, (c) is a figure which shows the waveform of a U-phase digital signal.

As shown in FIG. 4A, the U-phase-corresponding voltage is a substantially sine wave that oscillates up and down around 0V. In the present embodiment, since two sets of four-pole permanent magnets 32A are provided, one cycle of the U-phase-corresponding voltage, that is, 360 ° in electrical angle, corresponds to half rotation of the rotor 32, that is, two cycles, The electrical angle of 720 ° corresponds to one rotation of the rotor 32.

The zero cross point, which is the point at which the U-phase corresponding voltage passes 0V, exists every half cycle of the U-phase corresponding voltage, that is, every 180 ° in electrical angle, and during one rotation of the rotor 32 (for 720 ° in electrical angle). There are four zero cross points. In addition, among the zero cross points, there is a “rise” zero cross point at which the U-phase-corresponding voltage changes from a value smaller than 0 V to a value larger than 0 V, every 1 cycle, that is, every 360 ° in electrical angle. There are two points during one rotation of the rotor 32.

Moreover, since the U-phase compatible voltage is proportional to the U-phase induced voltage, the U-phase induced voltage is a substantially sine wave synchronized with the U-phase compatible voltage, and the timing of the zero-cross point of the U-phase induced voltage is also the U-phase compatible voltage. Synchronize with the zero cross point timing. The V phase induced voltage is a substantially sine wave delayed by 120 ° in electrical angle from the U phase induced voltage, and the W phase induced voltage is a substantially sine wave delayed by 240 ° in electrical angle from the U phase induced voltage.

The number of zero cross points of all three phases of the U-phase induced voltage, the V-phase induced voltage, and the W-phase induced voltage is 12 points during one rotation of the rotor 32, and every time the rotor 32 rotates 30 ° (electrical angle At every 60 °), the induced voltage of any of the U-phase induced voltage, V-phase induced voltage, and W-phase induced voltage passes through the zero cross point. There are six “rise” zero cross points for all three phases, and each time the rotor 32 rotates 60 ° (every 120 ° in electrical angle), the U-phase induced voltage, the V-phase induced voltage, and the W-phase It passes through the “rise” zero cross point in the order of the induced voltage.

As shown in FIG. 4B, the U-phase analog signal is a signal obtained by amplifying and offsetting the U-phase corresponding voltage by the differential amplifier circuit 82. In this embodiment, the U-phase analog signal is centered on 2.5V. And a substantially sine wave having an amplitude of 1.3V, a maximum value of 3.8V, and a minimum value of 1.2V. The timing at which the U-phase analog signal passes 2.5 V corresponds to the zero-cross point of the U-phase induced voltage (or U-phase compatible voltage). A broken line B in FIG. 4B indicates a reference voltage signal, which is 2.5 V in this embodiment.

As shown in FIG. 4C, the U-phase digital signal is a rectangular wave that is a combination of a high signal (5 V) and a low signal (0 V) that are comparison results by the comparator 92. The U-phase digital signal continues to output a high signal while the U-phase analog signal is larger than the reference voltage signal (between 0 ° and 180 ° in electrical angle, between 360 ° and 540 °, etc.). Further, during a period in which the U-phase analog signal is equal to or lower than the reference voltage signal (such as between 180 ° and 360 ° in electrical angle, between 540 ° and 720 °, etc.), the low signal is continuously output. The timing at which the output of the U-phase digital signal switches from the high signal to the low signal or the timing at which the output from the low signal to the high signal corresponds to the timing of the zero-cross point of the U-phase induced voltage. The timing at which the output of the U-phase digital signal switches from the low signal to the high signal corresponds to the timing of the zero cross point of the “rise” of the U-phase induced voltage.

Returning to FIG. 2, the control signal output circuit 75 is connected to the gates of the six FETs Q1 to Q6. Based on the drive signal input from the control unit 76, the voltage signal ( H1 to H6). Of the six FETs Q1 to Q6, the FET whose voltage signal is input to the gate is turned on, energizing the stator winding 33A of the motor 3 is permitted, and the FET whose voltage signal is not input to the gate is OFF. Then, the energization of the stator winding 33A is cut off.

The control unit 76 stores a central processing unit (CPU) (not shown) that performs calculation, comparison, and the like for outputting a drive signal based on the processing program and various data, and stores the processing program, control data, various threshold values, and the like. (Not shown), a RAM (not shown) for temporarily storing various data, and a time measuring function capable of measuring time. The control unit 76 includes a plurality of A / D input ports that convert analog signals into digital information, input ports that receive digital signals, and output ports that output various signals. In the present embodiment, the control unit 76 is a microcomputer.

The controller 76 calculates the rotational position (rotation angle) of the rotor 32 based on a signal (induced voltage analog signal or induced voltage digital signal) corresponding to the induced voltage generated in the stator winding 33A input to various ports. The motor 3 is controlled based on the information on the rotational position. That is, the motor 3 is controlled by a sensorless system that controls the rotation of the rotor 32 based on the induced voltage generated in the stator winding 33A without using a Hall element. The control unit 76 calculates the rotational speed of the rotor 32 and controls the rotational speed of the rotor 32 based on the rotational speed and the pulling amount of the switch trigger 22A.

The calculation of the rotational position by the control unit 76 is performed by detecting the zero cross point of the induced voltages (U-phase induced voltage, V-phase induced voltage, W-phase induced voltage) generated in the coils U, V, W of the stator winding 33A. Do. The control unit 76 is configured to output each analog signal (U-phase analog signal, V-phase analog signal and W-phase analog signal) corresponding to the induced voltage of each phase, or each digital signal (U-phase digital signal, V-phase digital signal and W). The zero cross point of the U phase induced voltage, the V phase induced voltage, and the W phase induced voltage is detected by detecting the zero cross point of the phase digital signal), and the rotational position of the rotor 32 is calculated based on the zero cross point. . As described above, there are 12 zero cross points during one rotation of the rotor 32, and each time the rotor 32 rotates 30 °, the rotation position of the rotor 32 can be detected every 30 °.

The detection of the zero cross point of each analog signal by the control unit 76 is performed by using the voltage signal threshold corresponding to the zero cross point of each analog signal and detecting the timing at which each analog signal passes the voltage threshold. The voltage signal threshold value in the present embodiment is 2.5V. Further, the zero cross point of each digital signal is detected by the control unit 76 by detecting the timing at which the high signal and low signal of each digital signal are switched.

In this way, the control unit 76 detects the rotational position of the rotor 32 by detecting the zero cross point, and forms a drive signal for alternately switching the predetermined FETs Q1 to Q6 based on the rotational position, and the drive The signal is output to the control signal output circuit 75. As a result, a predetermined coil among the coils U, V, and W is alternately energized to rotate the rotor 32 in a predetermined rotation direction. In this case, the drive signal for switching the FETs Q4 to Q6 connected to the negative power supply side is output as a pulse width modulation signal (PWM signal). The PWM signal is a signal that can change the signal output time (pulse width) in the switching period (predetermined time) for turning on / off the FET.

The calculation of the number of rotations by the control unit 76 detects the time interval of the zero cross point, and calculates the rotation value (rpm) per minute of the rotor 32 based on this time interval. For example, if the time interval of the zero cross point is T (ms), the time required for one rotation of the rotor 32 is T × 12 (ms), and the rotation speed of the rotor 32 per second is 1000 / (T × 12). ) (Times), and the rotation speed N (rpm) is calculated as N = (1000 / (T × 12)) × 60.

The control of the number of rotations of the rotor 32 by the control unit 76 is performed based on a trigger signal corresponding to the pushing amount output from the switch trigger 22A. The control unit 76 sets a target rotation speed according to the trigger signal, compares the target rotation speed with the detected rotation speed of the rotor 32, and changes the duty ratio of the PWM signal based on the comparison result. The power supply amount to the motor 3 is adjusted, and the rotation speed of the rotor 32 is controlled. The control unit 76 functions as a motor control unit, a drive state detection unit, and a rotation number detection unit of the present invention.

Next, control of the motor 3 by the control unit 76 will be described. The controller 76 calculates the rotational position of the rotor 32 based on the induced voltage analog signal and controls the motor 3, and calculates the rotational position of the rotor 32 based on the induced voltage digital signal. And the two control modes according to the driving state (whether the driving is in a starting state or whether the rotational speed of the rotor 32 is in a low rotational speed state). And the motor 3 is controlled. That is, the control unit 76 selects one of the induced voltage analog signal and the induced voltage digital signal according to the driving state, and controls the motor 3 based on the selected one signal.

Here, the characteristics of the digital signal control mode and the characteristics of the analog signal control mode will be described.

First, characteristics of the digital signal control mode, that is, characteristics of control of the motor 3 based on the induced voltage digital signal will be described. In the digital signal control mode, the object to be calculated by the control unit 76 is an induced voltage digital signal that is a binary signal, so the control unit 76 can calculate the rotational position of the rotor 32 at high speed. For this reason, even if the rotor 32 is in a high rotational speed state, a deviation between the calculated rotational position of the rotor 32 and the actual rotational position occurs only slightly, and the motor 3 can be controlled stably. However, when the rotor 32 is in the low rotation speed state in the digital signal control mode, the induced voltage generated in the stator winding 33A is low, and reverse rotation due to torque ripple or the like generated during rotation is likely to occur. Therefore, the comparator that outputs the induced voltage digital signal (for example, the comparator 92 that outputs the U-phase digital signal) is likely to cause chattering, and the motor 3 can be controlled stably. There is a possibility that it cannot be done. In addition, when the rotor 32 is in a low rotational speed state, the induced voltage generated in the stator winding 33A becomes low and the difference between the induced voltage analog signal and the reference voltage signal becomes small. Depending on the degree of resolution of the comparator 92) that outputs a signal and the hysteresis characteristics, there is a risk of malfunction. The malfunction is, for example, a malfunction in which the comparator outputs a low signal because the induced voltage analog signal is larger than the reference voltage signal but the difference is slight.

With reference to FIG. 7, chattering in a low rotation speed state in motor control based on a digital signal corresponding to an induced voltage will be described using a conventional electric device as an example. FIG. 7 is a diagram showing voltage signals at various parts when a rotor in a conventional electric device that controls a motor based on a digital signal corresponding to an induced voltage is in a low rotation speed state, and (a) is input to a comparator. The figure which shows the waveform of the signal according to the induced voltage to be performed, (b) is a figure which shows the waveform of the digital signal which a comparator outputs.

As shown in FIG. 7A, in general, when the rotor is in a low rotation speed state, the induced voltage generated in the motor coil is low, so that reverse rotation caused by torque ripple generated during rotation occurs. In some cases, the signal corresponding to the induced voltage input to the comparator may rise and fall at a high speed across 0 V in the vicinity of the zero cross point (180 ° in electrical angle, near 360 °). In such a case, as shown in FIG. 7B, the comparator in the conventional electric device repeats the high signal and the low signal alternately at high speed as a digital signal corresponding to the induced voltage near the zero cross point. The possibility of causing chattering to be output increases. When the comparator causes chattering, the detection of the zero cross point based on the digital signal lacks accuracy, the rotational position detection (rotational position calculation) of the rotor becomes inaccurate, and the control of the motor becomes unstable. As described above, in the conventional electric device that controls the motor based on the digital signal corresponding to the induced voltage, there is a possibility that the control of the motor becomes unstable when the rotor is in a low rotation speed state.

Thus, in the digital signal control mode, there is a possibility that the control of the motor 3 may become unstable when the rotor 32 is in the low rotation speed state, but the motor 3 is in the case where the rotor 32 is in the high rotation speed state. It is suitable for the control.

Next, characteristics of the analog signal control mode, that is, characteristics of control of the motor 3 based on the induced voltage analog signal will be described. In the analog signal control mode, the induced voltage analog signal A / D converted at the A / D input port is processed by the controller 76 based on a program for removing chattering components stored in advance in the ROM. For this reason, the zero cross point can be accurately calculated even in the low rotational speed state. Thereby, even if the rotor 32 is in a low rotation speed state, the control unit 76 can accurately detect (calculate) the zero cross point, and can control the motor 3 stably. However, in general, the resolution of the A / D input port is higher than the resolution of the comparator (for example, the comparator 92 that outputs the U-phase digital signal), and the A / D conversion of the induced voltage analog signal takes longer than the comparison processing in the comparator. In addition, since the processing based on the program by the control unit 76 also takes time, the calculation speed of the rotational position of the rotor 32 in the analog signal control mode is slower than the calculation speed in the digital signal control mode. For this reason, in the high rotational speed state in the analog signal control mode, there is a possibility that the calculated rotational position of the rotor 32 and the actual rotational position are greatly deviated and the motor 3 cannot be stably controlled. It should be noted that the time required for calculating the rotational position is not such that the control of the motor 3 becomes unstable in the low rotational speed state.

Thus, in the analog signal control mode, there is a possibility that the control of the motor 3 may become unstable when the rotor 32 is in a high rotational speed state, but the motor 3 is in a case where the rotor 32 is in a low rotational speed state. It is suitable for the control.

In view of the characteristics of each control mode described above, the control unit 76 in the present embodiment controls the motor 3 based on the induced voltage digital signal (analog) when in the drive start state or in the low rotation speed state. When the signal control mode is selected) and neither the driving start state nor the low rotation speed state is selected, the motor 3 is controlled based on the induced voltage digital signal (digital signal control mode is selected). In other words, after the analog signal control mode is executed, the digital signal control mode is entered. Thereby, it is possible to achieve both stable control of the motor 3 in the low rotational speed state and stable control of the motor 3 in the high rotational speed state in the sensorless system.

An example of a control flow of the motor 3 by the control unit 76 will be described based on FIG. FIG. 5 is a flowchart showing a control flow of the control unit 76.

As shown in FIG. 5, when the battery pack P is attached to the impact driver 1, the control unit 76 starts controlling the motor 3 (S201). The control unit 76 stops the motor 3 after starting the control of the motor 3 (S202). Thereby, for example, it is possible to prevent the tip tool from being driven at an unintended timing of the operator such as the motor 3 being driven and the tip tool being driven at the moment when the battery pack P is mounted on the impact driver 1. it can. This is particularly effective when the battery pack P is mounted while the switch trigger 22A is in the on state.

Next, it is determined whether or not the switch trigger 22A is in an on state (whether or not it has been pressed). Whether or not the switch is on is determined by whether or not a trigger signal is input to the control unit 76 from the switch trigger 22A. When it is determined that the switch trigger 22A is not in the on state (S203: No), the motor 3 is stopped (S202), and it is determined again whether the switch trigger 22A is in the on state (S203). That is, until the switch trigger 22A is determined to be in the ON state in Step 202, the driving stop state of the motor 3 is maintained while repeating Step 202 and Step 203.

When it is determined that the switch trigger 22A is in the on state (S203: Yes), the analog signal control mode is selected as the control mode, and the driving of the motor 3 is started (S204). At the start of driving of the motor 3 (driving start state), since the rotor 32 is in the low rotation speed state, the motor 3 is controlled based on the induced voltage analog signal.

When driving of the motor 3 is started, it is determined whether or not the calculated rotation speed N of the rotor 32 is equal to or less than the rotation speed threshold A (step 205). If it is determined that the rotational speed N is equal to or lower than the rotational speed threshold A (S206: Yes), the rotational speed of the rotor 32 is in the low rotational speed state (low rotational speed range), and therefore the control unit 76 sets the analog signal control mode. Select and control the motor 3 based on the induced voltage analog signal. As a result, the motor 3 can be stably controlled even in the low rotational speed state. Note that the controller 76 determines whether or not the engine is in the low engine speed state by checking whether or not the calculated engine speed N of the rotor 32 is equal to or less than the engine speed threshold A stored in the ROM of the controller 76 in advance. Judge with. In the present embodiment, the rotation speed threshold A is a rotation speed that is determined to be less likely to cause chattering by a comparator (for example, the comparator 92 that outputs a U-phase digital signal) if the rotation speed is higher than the value. Is set to a value.

Thereafter, it is determined whether or not the switch trigger 22A is in an ON state (S208). When it is determined that the switch trigger 22A is in the on state (S208: Yes), it is determined again whether the rotational speed N is equal to or lower than the rotational speed threshold A (S205). That is, the control unit 76 repeats step 205, step 206, and step 208 in this order as long as the switch trigger 22A is in an on state and the rotation speed N is in a state (low rotation speed state) that is equal to or less than the rotation speed threshold value A. The motor 3 is controlled in the analog signal control mode.

If it is determined in step 205 that the rotational speed N is not equal to or lower than the rotational speed threshold A (step 205: No), the rotational speed of the rotor 32 is not in the low rotational speed state, so the control unit 76 selects the digital signal control mode, The motor 3 is controlled based on the induced voltage digital signal. Thereby, in the control of the sensorless motor 3, it is possible to achieve both stable control of the motor 3 in the low rotational speed state and stable control of the motor 3 in the high rotational speed state.

Thereafter, it is determined whether or not the switch trigger 22A is in an ON state (S208). When it is determined that the switch trigger 22A is in the on state (S208: Yes), it is determined again whether the rotational speed N is equal to or lower than the rotational speed threshold A (S205). That is, as long as the switch trigger 22A is on and the rotation speed N is not equal to or less than the rotation speed threshold A, the control unit 76 repeats step 205, step 207, and step 208 in this order in the digital signal control mode. 3 is controlled. While the motor 3 is controlled in the digital signal control mode while repeating Step 205, Step 207, and Step 208, the rotational speed of the rotor 32 decreases, and the rotational speed N is equal to or smaller than the rotational speed threshold A in Step 205. If it is determined that there is (S205: Yes), the digital signal control mode is switched to the analog signal control mode, and the motor 3 is controlled based on the induced voltage analog signal.

If it is determined in step 208 that the switch trigger 22A is not in the ON state (S208: No), the process returns to step 202 described above, and the drive of the motor 3 is stopped. Thereafter, as described above, the stop state of the motor 3 is maintained while repeating Step 202 and Step 203 until the switch trigger 22A is turned on again.

Next, the voltage, voltage signal, rotation speed, and duty ratio of each unit when the motor 3 is controlled using the control flow by the control unit 76 described above based on FIG. 6 will be described. FIG. 6 is a diagram illustrating a timing chart of the voltage, voltage signal, rotation speed, and duty ratio of each unit when the motor 3 is controlled using the control flow by the control unit 76. FIG. The figure which shows a waveform, (b) is a figure which shows the waveform of a U-phase analog signal, (c) is a figure which shows the waveform of a U-phase digital signal, (d) is a figure which shows the rotation speed of the rotor 32, (e) is It is a figure which shows a duty ratio. 6A to 6E indicate time (time) and electrical angle, and a broken line B in FIG. 6B indicates a reference voltage signal as in FIG. The broken line in (d) indicates the rotation speed threshold A.

As shown in FIGS. 6A to 6E, at time t0, the control unit 76 starts driving the motor 3 in the analog signal control mode (corresponding to Yes and S204 in S203 in FIG. 5). . As shown in FIGS. 6D and 6E, between time t0 and time t1, the control unit 76 increases the duty ratio in a linear function with respect to time based on the rotational speed control. The number also increases in proportion to the duty ratio. Further, as shown in FIGS. 6A to 6C, between time t0 and time t1 (electrical angle 0 ° to 360 °), the rotor 32 is in a low rotational speed state and corresponds to the U phase. The amplitude of the voltage and the U-phase analog signal is also small, and the difference between the U-phase analog signal and the reference voltage signal is also small. For this reason, the comparator 92 malfunctions to output a low signal as a U-phase digital signal even though the U-phase analog signal is larger than the reference voltage signal in the electrical angle range of 0 ° to 180 °. ing. However, since the rotational speed does not exceed the rotational speed threshold A between time t0 and time t1, the control unit 76 controls the motor 3 in the analog signal control mode, and stable control of the motor 3 is maintained. ing.

Between time t1 and time t2 (electrical angle 360 ° to 720 °), the control unit 76 further increases the duty ratio based on the rotational speed control, and the rotational speed further increases. Further, the amplitudes of the U-phase compatible voltage and the U-phase analog signal are larger than the time t1, and the period is shortened. Furthermore, since the difference between the U-phase analog signal and the reference voltage signal is also larger than the time t1 during this period, the U-phase digital signal is output accurately (FIG. 6C). Note that the period from time t0 to time t2 corresponds to the repetition of Yes in S205, Yes in S206, and Yes in S208 in FIG.

As shown in FIG. 6D, when the time t2 is exceeded, the rotational speed exceeds the rotational speed threshold A, and the control unit 76 switches the control mode to the digital signal control mode (No in S205 and S207 in FIG. 5). Equivalent). If the time t2 is exceeded and the rotational speed exceeds the rotational speed threshold A, the motor 3 may not be stably controlled in the analog signal control mode, but the control unit 76 controls the motor 3 in the digital signal control mode. The motor 3 can be controlled stably.

After time t3, the control unit 76 increases the duty ratio to the maximum, and the rotation speed is also maximum. After time t3, the rotation speed is maximum, the U-phase compatible voltage and the amplitude of the U-phase analog signal are maximum, and the difference between the U-phase analog signal and the reference voltage signal is also maximum. A signal is output. In this state, the control unit 76 controls the motor 3 in the digital signal control mode in which the rotational position of the rotor 32 can be calculated at high speed, so that the motor 3 can be controlled more stably. Note that after the time t2 is exceeded, this corresponds to repetition of No in S205, Yes in S207, and Yes in S208 in FIG.

As described above, the impact driver 1, which is an example of the electric device according to the embodiment of the present invention, generates an induced voltage generated in the stator winding 33A, the motor having the stator 33 having the stator winding 33A and the rotor 32, and the stator winding 33A. An induced voltage detection circuit unit 71 for detecting, and a control unit 76 for controlling the motor 3 based on the induced voltage and detecting a driving state (such as a driving start state) of the motor 3. The voltage detection circuit unit 71 outputs a digital signal (induced voltage digital signal) corresponding to the induced voltage, a U-phase digital signal output circuit 9, a V-phase digital signal output circuit, a W-phase digital signal output circuit, and a voltage according to the induced voltage. A U-phase analog signal output circuit 8, a V-phase analog signal output circuit, and a W-phase analog signal output circuit that output analog signals (induced voltage analog signals); A control unit 76 selects either of the induced voltage digital signal and the induced voltage analog signal in response to the drive state, controls the motor 3 based on either one of the signal selected.

With the above configuration, the impact driver 1 is configured to control the motor 3 based on a signal corresponding to the induced voltage, and thus it is not necessary to provide a hall element in the impact driver 1. Thereby, the number of parts can be reduced and assemblability can be improved. Further, the induced voltage detection circuit unit 71 of the impact driver 1 outputs a digital signal (induced voltage digital signal) corresponding to the induced voltage to the control unit 76, a U-phase digital signal output circuit 9, a V-phase digital signal output circuit, and a W-phase digital signal output circuit. A phase digital signal output circuit, and a U phase analog signal output circuit 8, a V phase analog signal output circuit, and a W phase analog signal output circuit that output an analog signal (induced voltage analog signal) corresponding to the induced voltage to the control unit 76. Therefore, a signal used for controlling the motor 3 can be appropriately selected. Thereby, the motor 3 can be controlled more stably and favorably, and the operability can be improved. That is, the motor 3 can be stably controlled in the sensorless driving method.

The control unit 76 can select either an induced voltage analog signal or an induced voltage digital signal as a signal corresponding to the induced voltage used for controlling the motor 3 according to the driving state. As a result, when the motor 3 is controlled based on the induced voltage digital signal, the control is likely to become unstable (for example, when the motor 3 starts to be driven). The motor 3 can be controlled based on the induced voltage analog signal without using the. For this reason, the motor can be controlled more stably and satisfactorily and the operability can be improved as compared with the configuration in which the signal used for controlling the motor cannot be appropriately selected from both signals according to the driving state. Can be made.

Further, the control unit 76 in the impact driver 1 has a function of detecting the rotational speed of the rotor 32, and the rotational speed of the rotor 32, which is an element that greatly affects the stability of the control of the motor 3, particularly in the driving state. Since either the induced voltage digital signal or the induced voltage analog signal can be selected according to the state (the number of rotations of the rotor 32), the motor 3 can be controlled based on the selected signal. Control of the motor 3 can be made more stable.

The control unit 76 controls the motor 3 based on the induced voltage analog signal when the rotational speed of the rotor 32 is equal to or lower than the rotational speed threshold A, and when the rotational speed is greater than the rotational speed threshold A, the induced voltage The motor 3 can be controlled based on the digital signal. Thereby, when the motor 3 is controlled based on the induced voltage digital signal, the induced voltage analog signal is generated in a driving state where the control may become unstable, that is, in a state where the rotational speed of the rotor 32 is low (low rotational speed state). When the motor 3 is controlled on the basis of the control signal and the motor 3 is controlled on the basis of the induced voltage analog signal, the control is likely to become unstable. That is, in the state where the rotational speed is high (high rotational speed state), the induced voltage digital The motor 3 can be controlled based on the signal. Therefore, the motor 3 can be controlled more stably.

Further, since the control unit 76 controls the motor 3 based on the induced voltage analog signal at the start of driving of the motor 3, the motor 3 is surely based on the induced voltage analog signal in the low rotation speed state at the start of driving of the motor 3. Can be controlled. That is, it is possible to reliably avoid the control of the motor 3 based on the induced voltage digital signal that may cause the control of the motor 3 to become unstable in the low rotational speed state when the motor 3 starts to be driven. Therefore, the motor 3 can be controlled more stably.

The control unit 76 controls the motor 3 based on the induced voltage digital signal after controlling the motor 3 based on the induced voltage analog signal (analog signal control mode). For this reason, for example, in the low rotation speed state when the motor 3 is started (at the start of driving), the control of the motor 3 based on the induced voltage digital signal that may cause the control of the motor 3 to become unstable in this state is more reliable. Can be avoided. Therefore, the motor 3 can be controlled more stably and satisfactorily.

Further, the impact driver 1 includes a switch trigger 22A for instructing activation of the motor 3, and when the switch trigger 22A is operated, the control unit 76 controls the motor 3 based on the induced voltage analog signal (analog signal). Control mode) and then the motor 3 is controlled based on the induced voltage digital signal (digital signal control mode). For this reason, for example, in the low rotation speed state when the motor 3 is started (at the start of driving), the control of the motor 3 based on the induced voltage digital signal that may cause the control of the motor 3 to become unstable in this state is more reliable. Can be avoided. Therefore, the motor 3 can be controlled more stably and satisfactorily.

In the above-described embodiment, the case where the present invention is applied to an impact driver has been described as an example, but the present invention is not limited to this. Various modifications and improvements are possible within the scope described in the claims. For example, the present invention can be applied to an electric device (an electric tool, an electric working machine, etc.) provided with a DC brushless motor in addition to an impact driver. Furthermore, the present invention is preferably applicable to an electric tool or an electric work machine having a configuration in which a rotor (rotating shaft) represented by a hammer drill, a driver drill, a compressor, or the like does not lock. Further, the motor is not limited to a DC brushless motor, and can be applied to an induction motor.

In addition, the control unit 76 in the present embodiment is configured to switch the control mode by determining whether the driving state is the driving start state or the low rotational speed state. As an alternative, the control mode may be switched by determining the elapsed time from the start of driving.

For example, when the elapsed time from the start of driving is less than a predetermined time, considering that the rotational speed state of the rotor 32 is a low rotational speed state, the predetermined time elapses from the start of driving the motor. The motor 3 may be controlled based on the induced voltage analog signal. In this case, in the low rotational speed state at the start of driving of the motor 3, the control of the motor 3 based on the induced voltage digital signal that may cause the control of the motor 3 to become unstable in this state can be avoided more reliably. The motor can be controlled more stably and satisfactorily.

Further, the control mode may be switched by judging the state of the trigger signal such as the state of the trigger signal (the state of the target rotational speed) according to the pulling amount of the switch trigger 22A, that is, the target rotational speed determined by the trigger signal is predetermined. If the configuration is such that the motor 3 is controlled in the analog signal control mode, the same effect as in the present embodiment can be obtained. be able to.

In the present embodiment, the control unit 76 calculates the rotation speed, but a circuit for detecting the rotation speed may be provided separately from the control unit 76.

In this embodiment, in order to detect the U-phase induced voltage, the U-phase component based on the voltage at the neutral point voltage dividing point 71e obtained by dividing the neutral point 71a by the resistor 71D and the resistor 71E. The voltage at the pressure point 81a is amplified and offset by the differential amplifier circuit 82. However, the neutral point 71a is connected to the ground via a capacitor for removing noise, and the neutral point 71a is used as a reference. A configuration in which the voltage at the phase voltage dividing point 81 a is amplified and offset to the input level of the control unit 76 by the differential amplifier circuit 82 may be adopted.

DESCRIPTION OF SYMBOLS 1 ... Impact driver 2 ... Housing 3 ... Motor 4 ... Drive circuit part 5 ... Cooling fan 6 ... Power transmission part 7 ... Control board part 8 ... U-phase analog signal output circuit 9 ... U-phase digital signal output circuit 21 ... Motor housing 22 ... handle housing 22A ... switch trigger 22B ... switch mechanism 23 ... substrate housing part 31 ... rotating shaft 32 ... rotor 32A ... permanent magnet 33 ... stator 33A ... stator winding 61 ... speed reduction mechanism 62 ... impact mechanism 63 ... anvil part 71 ... induction Voltage detection circuit unit 72: U-phase signal output circuit 73 ... V-phase signal output circuit 74 ... W-phase signal output circuit 75 ... Control signal output circuit 76 ... Control unit 81 ... Voltage division circuit 82 ... Differential amplification circuit 91 ... Voltage division Circuit 91a ... Reference voltage dividing point 92 ... Comparator A ... Rotation Threshold B ... dashed N ... rpm P ... battery pack U ... coil V ... coil W ... coil Vcc ... reference voltage

Claims

A motor having a rotor and a stator having windings;
Induced voltage detection means for detecting the induced voltage generated in the winding;
Motor control means for controlling the motor based on the induced voltage,
The induced voltage detection means includes a digital signal output means for outputting a digital signal corresponding to the induced voltage to the motor control means, and an analog signal output means for outputting an analog signal corresponding to the induced voltage to the motor control means. The electric device characterized by having.
The motor control means selects either the digital signal or the analog signal according to the driving state of the motor, and controls the motor based on the selected signal. The electric device according to claim 1.
A driving state detecting means for detecting the driving state of the motor;
The drive state detection means includes rotation speed detection means for detecting the rotation speed of the rotor,
The motor control means selects one of the digital signal and the analog signal according to the number of revolutions, and controls the motor based on the selected one of the signals. Item 3. The electric device according to item 1 or 2.
The motor control means controls the motor based on the analog signal when the rotational speed is equal to or lower than the rotational speed threshold value, and controls the motor based on the digital signal when the rotational speed is greater than the rotational speed threshold value. The motor according to claim 3, wherein the motor is controlled.
5. The electric device according to claim 1, wherein the motor control unit controls the motor based on the analog signal when the motor starts to be driven. 6.
6. The motor control unit according to claim 1, wherein the motor control unit controls the motor based on the analog signal until a predetermined time elapses from the start of driving of the motor. Electric equipment.
4. The electric device according to claim 1, wherein the motor control unit controls the motor based on the digital signal after controlling the motor based on the analog signal. 5.
A motor having a rotor and a stator having windings;
A trigger for instructing activation of the motor;
Induced voltage detection means for detecting the induced voltage generated in the winding;
Motor control means for controlling the motor based on the induced voltage,
The induced voltage detection means includes a digital signal output means for outputting a digital signal corresponding to the induced voltage, and an analog signal output means for outputting an analog signal corresponding to the induced voltage,
The motor control means controls the motor based on the analog signal when the trigger is operated, and then controls the motor based on the digital signal.