WO2021100844A1

WO2021100844A1 - Electric tool, control method, and program

Info

Publication number: WO2021100844A1
Application number: PCT/JP2020/043352
Authority: WO
Inventors: 中原　雅之; 隆司草川; 尊大植田
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2019-11-22
Filing date: 2020-11-20
Publication date: 2021-05-27
Also published as: JP2021079522A

Abstract

The purpose of the present disclosure is to prevent a reduction in the efficiency of an electric motor. An electric tool (1) is provided with an electric motor (15), a drive power transmission mechanism (18), and a control unit (4). The electric motor (15) has a permanent magnet (131) and a coil (141). The drive power transmission mechanism (18) is driven by the electric motor (15). The control unit (4) performs vector control to control an excitation current and a torque current that are supplied to the electric motor (15). The control unit (4) performs control so as to increase the excitation current in accordance with at least an increase in external load to which an output shaft (16) of the electric motor (15) is subjected.

Description

Power tools, control methods, and programs

This disclosure generally relates to power tools, control methods, and programs. More specifically, the present disclosure relates to a power tool including a power tool, a control method for the power tool, and a program.

Patent Document 1 describes an electric tool capable of controlling the rotation speed of an electric motor. This electric tool includes a brushless DC motor (motor), a battery voltage detection unit, a rotation position detection unit, and a control unit. The battery voltage detection unit detects the voltage of the battery used to drive the brushless DC motor. The rotation position detection unit detects the rotation position of the brushless DC motor. The control unit controls the drive output to the brushless DC motor by the signal from the rotation position detection unit. When controlling the drive output to the brushless DC motor, the control unit sends the brushless DC motor to the brushless DC motor so that the rotation speed or energizing current of the brushless DC motor becomes the target value corresponding to the battery voltage detected by the battery voltage detection unit. Control the energization angle or advance angle.

JP-A-2014-144496

By the way, in the case of electric tools, the rotation speed of the electric motor may decrease due to the increase in load, and the target rotation speed of the electric motor may not be obtained. Therefore, it is desired to suppress the reduction in efficiency of the motor.

The present disclosure has been made in view of the above reasons, and an object of the present disclosure is to provide an electric tool, a control method, and a program capable of suppressing the reduction in efficiency of the electric motor.

The electric tool of one aspect of the present disclosure includes an electric motor, a driving force transmission mechanism, and a control unit. The motor has a permanent magnet and a coil. The driving force transmission mechanism is driven by the electric motor. The control unit performs vector control for controlling the exciting current and the torque current supplied to the motor. The control unit controls to increase the exciting current at least in response to an increase in a load received from the outside by the output shaft of the motor.

One aspect of the control method of the present disclosure is a control method of an electric tool including an electric motor having a permanent magnet and a coil. The control method includes a main step of performing vector control for controlling an exciting current and a torque current supplied to the electric motor that drives the driving force transmission mechanism. The main step includes at least a sub-step for controlling the exciting current to increase in response to an increase in a load received from the outside by the output shaft of the motor.

The program of one aspect of the present disclosure is a program for causing one or more processors to execute the above control method.

FIG. 1 is a block configuration diagram of a power tool according to an embodiment. FIG. 2 is a schematic view of the same power tool. FIG. 3 is a diagram for explaining the characteristics of the same power tool. FIG. 4 is a diagram for explaining the characteristics of the same power tool. FIG. 5 is a flowchart for explaining the operation of the power tool of the same.

(1) Outline Each figure described in the following embodiments is a schematic view, and the ratio of the size and the thickness of each component in each figure does not necessarily reflect the actual dimensional ratio. Not necessarily.

The power tool 1 (see FIGS. 1 and 2) according to the present embodiment is, for example, a tool used in a factory, a construction site, or the like. Here, as an example, the power tool 1 will be described on the assumption that it is an impact driver used for tightening a work object (fastening member such as a bolt or a screw). However, the type of the power tool 1 is not particularly limited, and a drill driver, an impact wrench, or the like may be used.

The electric tool 1 includes an electric motor 15 (for example, an AC electric motor), a driving force transmission mechanism 18, and a control unit 4. The electric motor 15 has a permanent magnet 131 and a coil 141. The electric motor 15 is, for example, a brushless motor. The electric motor 15 of the present embodiment is a synchronous electric motor, and more specifically, a permanent magnet synchronous electric motor (PMSM (Permanent Magnet Synchronous Motor)).

The driving force transmission mechanism 18 is driven by the electric motor 15. The control unit 4 performs vector control for controlling the exciting current (d-axis current) and the torque current (q-axis current) supplied to the motor 15. The control unit 4 executes weakening magnetic flux control by vector control. In the weakened magnetic flux control, the control unit 4 uses a weakened magnetic flux current (d-axis current) for generating a second magnetic flux (weakened magnetic flux) that weakens the magnetic flux (first magnetic flux) of the permanent magnet 131 in the coil 141 as an exciting current. Let it flow to 141. The weakening magnetic flux current is a negative exciting current. Due to the weak magnetic flux control, the rotation speed of the electric motor 15, that is, the rotation speed of the output shaft 16 (rotation shaft) is increased.

Here, the control unit 4 of the present embodiment controls so as to increase the exciting current at least in response to an increase in the load received from the outside by the output shaft 16 of the electric motor 15. "Increasing the exciting current" as used in the present disclosure means increasing the magnitude (absolute value) of the exciting current.

According to this configuration, the control unit 4 increases the exciting current at least in response to an increase in the load. Therefore, for example, it is possible to reduce the possibility that the rotation speed of the motor 15 decreases due to an increase in the load and the target rotation speed of the motor cannot be obtained. As a result, it is possible to suppress the reduction in efficiency of the electric motor 15.

(2) Details (2.1) Overall configuration Hereinafter, the overall configuration of the power tool 1 according to the present embodiment will be described in detail with reference to FIGS. 1 to 5. In the following, a person who performs the work of tightening the work target by using the power tool 1 may be simply referred to as a “user”.

As shown in FIG. 2, the electric tool 1 includes an electric motor 15, a power supply unit 32, a driving force transmission mechanism 18, an impact mechanism 17, a chuck 23, a trigger switch 29, a control unit 4, and a bit rotation measurement. A unit 25, a torque measuring unit 26, and a motor rotation measuring unit 27 are provided. Further, the power tool 1 further includes a tip tool (bit). The control unit 4 will be described in detail in the next column.

The impact mechanism 17 has an output shaft 21. The output shaft 21 is a portion that rotates by a driving force transmitted from the electric motor 15. The chuck 23 is fixed to the output shaft 21 and is a portion to which the tip tool can be detachably attached. The electric tool 1 is a tool that drives the tip tool with the driving force of the electric motor 15. The tip tool is, for example, a screwdriver or a drill. Of the plurality of types of tip tools, the tip tool according to the application is selectively attached to the chuck 23 and used. The tip tool may be mounted directly on the output shaft 21.

The motor 15 (AC motor) is a drive source for driving the tip tool. As shown in FIG. 1, the electric motor 15 includes a rotor 13 having a permanent magnet 131 and a stator 14 having a coil 141. The rotor 13 includes an output shaft 16 (see FIG. 2) that outputs rotational power. The rotor 13 rotates with respect to the stator 14 due to the electromagnetic interaction between the coil 141 and the permanent magnet 131.

The power supply unit 32 is a so-called battery pack including one or a plurality of batteries 320 (for example, a secondary battery) that supply electric power to the electric motor 15. The power supply unit 32 is detachably attached to the lower end of the grip portion in the body of the power tool 1, for example. The driving force transmission mechanism 18 is driven by the electric motor 15. The driving force transmission mechanism 18 adjusts the rotational power of the electric motor 15 to output a desired torque. The driving force transmission mechanism 18 has a driving shaft 22 (see FIG. 2) which is an output unit.

The drive shaft 22 of the drive force transmission mechanism 18 is connected to the impact mechanism 17. The impact mechanism 17 converts the rotational power of the electric motor 15 received via the driving force transmission mechanism 18 into pulsed torque to generate an impact force. The impact mechanism 17 includes a hammer 19, an anvil 20, an output shaft 21, and a spring 24. The hammer 19 is attached to the drive shaft 22 of the drive force transmission mechanism 18 via a cam mechanism. The anvil 20 is coupled to the hammer 19 and rotates integrally with the hammer 19. The spring 24 pushes the hammer 19 toward the anvil 20. The anvil 20 is integrally formed with the output shaft 21. The anvil 20 may be formed separately from the output shaft 21 and fixed to the output shaft 21.

When a load (torque) larger than the specified size is not applied to the output shaft 21, the drive shaft 22 and the hammer 19 connected by the cam mechanism rotate integrally, and the hammer 19 and the anvil 20 rotate integrally. Therefore, the output shaft 21 integrally formed with the anvil 20 rotates. On the other hand, when a load of a predetermined size or more is applied to the output shaft 21, the hammer 19 retracts against the spring 24 (that is, separates from the anvil 20) while being regulated by the cam mechanism. Then, when the connection between the hammer 19 and the anvil 20 is disengaged, the hammer 19 advances while rotating and gives a striking impact in the rotational direction to the anvil 20 to rotate the output shaft 21.

The trigger switch 29 is an operation unit that accepts an operation for controlling the rotation of the electric motor 15. By pulling the trigger switch 29, the motor 15 can be switched on and off. Further, the rotation speed (rotation speed) of the output shaft 21, that is, the rotation speed (rotation speed) of the motor 15 can be adjusted by the pull-in amount of the operation of pulling the trigger switch 29. The larger the pull-in amount, the faster the rotation speed of the electric motor 15. The control unit 4 rotates or stops the electric motor 15 according to the pull-in amount of the operation of pulling the trigger switch 29, and also controls the rotation speed of the electric motor 15. In the power tool 1, the tip tool is attached to the chuck 23. Then, the rotation speed of the tip tool is controlled by controlling the rotation speed of the electric motor 15 by operating the trigger switch 29.

Since the power tool 1 is provided with a chuck 23, the tip tool can be replaced according to the application, but it is not essential that the tip tool can be replaced. For example, the power tool 1 may be a power tool that can be used only with a specific tip tool.

The torque measuring unit 26 measures the operating torque of the motor 15. The torque measuring unit 26 is, for example, a magnetostrictive strain sensor capable of detecting torsional strain. The magnetostrictive strain sensor detects a change in the magnetostriction according to the strain generated by applying torque to the output shaft 16 of the motor 15 with a coil installed in the non-rotating portion of the motor 15, and a voltage signal proportional to the strain. Is output.

The bit rotation measuring unit 25 measures the rotation angle of the output shaft 21. Here, the rotation angle of the output shaft 21 is equal to the rotation angle of the tip tool (bit). As the bit rotation measuring unit 25, for example, a photoelectric encoder or a magnetic encoder can be adopted.

The motor rotation measuring unit 27 measures the rotation angle of the electric motor 15. As the motor rotation measuring unit 27, for example, a photoelectric encoder or a magnetic encoder can be adopted.

(2.2) Control unit The control unit 4 includes a computer system having one or more processors and memories. When the processor of the computer system executes the program recorded in the memory of the computer system, at least a part of the functions of the control unit 4 are realized. The program may be recorded in a memory, provided through a telecommunication line such as the Internet, or may be recorded and provided on a non-temporary recording medium such as a memory card.

The control unit 4 is configured to control the drive of the motor 15. The control unit 4 controls (for example, independently) the exciting current and the torque current supplied to the motor 15 (vector control). Here, the drive control of the control unit 4 includes a weakening magnetic flux control and a normal control. In other words, the control unit 4 has a first mode as a mode of weakening magnetic flux control and a second mode as a mode of normal control as operation modes.

In the first mode, the control unit 4 causes a weakened magnetic flux current to flow from the inverter circuit unit 51 (see FIG. 1), which will be described later, to the coil 141 of the motor 15. That is, the control unit 4 causes the coil 141 to flow a weakening magnetic flux current for generating a second magnetic flux that weakens the magnetic flux (first magnetic flux) of the permanent magnet 131 in the coil 141 by the weakening magnetic flux control.

In the second mode, the control unit 4 weakens the coil 141 from the inverter circuit unit 51 so that the magnetic flux current does not flow. That is, in normal control, the current flowing through the coil 141 is only the torque current (q-axis current).

It can be said that the normal control is performed so that the command value (target value) of the weakening magnetic flux (current) (target value) cid1 (see FIG. 1) is set to zero (0) and the weakening magnetic flux (current) converges to this command value cid1. On the other hand, the weakening magnetic flux control can be said to be a control performed so that the command value cid1 of the weakening magnetic flux (current) is made larger than zero (0) and the weakening magnetic flux (current) converges to this command value cid1. When the command value side1 of the weakening magnetic flux (current) becomes larger than zero (0), the weakening magnetic flux current (minus exciting current) flows through the motor 15, and the weakening magnetic flux is generated.

As shown in FIG. 1, the control unit 4 includes a command value generation unit 41, a speed control unit 42, a current control unit 43, a first coordinate converter 44, a second coordinate converter 45, and a magnetic flux. It has a control unit 46, an estimation unit 47, and a step-out detection unit 48. Further, the power tool 1 further includes an inverter circuit unit 51 and a plurality of (two in FIG. 1)

current sensors

61 and 62. The control unit 4 is used together with the inverter circuit unit 51, and controls the operation of the electric motor 15 by feedback control.

Each of the plurality of

current sensors

61 and 62 includes, for example, a Hall element current sensor or a shunt resistance element. The plurality of

current sensors

61 and 62 measure the current supplied from the battery 320 to the motor 15 via the inverter circuit unit 51. Here, a three-phase current (U-phase current, V-phase current, and W-phase current) is supplied to the motor 15, and the plurality of

current sensors

61 and 62 measure at least two-phase currents. In FIG. 1, the current sensor 61 measures the U-phase current and _{outputs the measured current value i u} 1, and the current sensor 62 measures the V-phase current and outputs the _{measured current value i v 1.}

The estimation unit 47 calculates the angular velocity ω1 (angular velocity of the output shaft 16) of the motor 15 by time-differentiating the rotation angle θ1 of the motor 15 measured by the motor rotation measurement unit 27.

The second coordinate converter 45 uses the current measured values i _u 1 and i _v 1 measured by the plurality of

current sensors

61 and 62 based on the rotation angle θ1 of the motor 15 measured by the motor rotation measuring unit 27. The coordinates are converted and the current measurement values id1 and iq1 are calculated. That is, the second coordinate converter 45, a current measurement value i _{u _1,} i v ₁ corresponding to the two-phase currents of the three phases, the current measurement value id1 corresponding to the magnetic field component (d-axis current), It is converted to the current measured value iq1 corresponding to the torque component (q-axis current).

The command value generation unit 41 generates the command value cω1 of the angular velocity of the motor 15. The command value generation unit 41 generates, for example, the command value cω1 according to the pull-in amount of the operation of pulling the trigger switch 29 (see FIG. 2). The command value generation unit 41 increases the command value cω1 of the angular velocity as the pull-in amount increases.

The speed control unit 42 generates the command value ciq1 based on the difference between the command value cω1 generated by the command value generation unit 41 and the angular velocity ω1 calculated by the estimation unit 47. The command value ciq1 is a command value that specifies the magnitude of the torque current (q-axis current) of the motor 15. The speed control unit 42 determines the command value ciq1 so as to reduce the difference between the command value cω1 and the angular velocity ω1. That is, the control unit 4 controls so that the rotation speed of the electric motor 15 matches the target value corresponding to the operation of the trigger switch 29.

In the case of weak magnetic flux control (in the case of the first mode), the magnetic flux control unit 46 includes an angular velocity ω1 calculated by the estimation unit 47, a command value cvq1 (described later) generated by the current control unit 43, and a current measurement value. The command value cid1 is determined based on iq1 (q-axis current). The command value cid1 is a command value that specifies the magnitude of the weakening magnetic flux (magnetic flux in the d-axis direction) of the motor 15. In the case of normal control (in the case of the second mode), the command value cid1 generated by the magnetic flux control unit 46 is a command value for setting the weakening magnetic flux to zero (0).

The current control unit 43 generates the command value cvd1 based on the difference between the command value cyd1 generated by the magnetic flux control unit 46 and the current measurement value id1 calculated by the second coordinate converter 45. The command value cvd1 is a command value that specifies the magnitude of the d-axis voltage of the motor 15. The current control unit 43 determines the command value cvd1 so as to reduce the difference between the command value cid1 and the current measurement value id1.

Further, the current control unit 43 generates the command value cvq1 based on the difference between the command value iq1 generated by the speed control unit 42 and the current measurement value iq1 calculated by the second coordinate converter 45. The command value cvq1 is a command value that specifies the magnitude of the q-axis voltage of the motor 15. The current control unit 43 generates the command value cvq1 so as to reduce the difference between the command value xiq1 and the current measurement value iq1.

The first coordinate converter 44 converts the command values cvd1 and cvq1 into coordinates based on the rotation angle θ1 of the electric motor 15 measured by the motor rotation measuring unit 27, and converts the command values cv _u 1, cv _v 1, and cv _w. 1 is calculated. That is, the first coordinate converter 44 sets the command value cvd1 corresponding to the magnetic field component (d-axis voltage) and the command value cvq1 corresponding to the torque component (q-axis voltage) to the command value corresponding to the three-phase voltage. Convert to cv _u 1, cv _v 1, cv _{w 1.} The command value cv _u 1 corresponds to the U-phase voltage, the command value cv _v 1 corresponds to the V-phase voltage, and the command value cv _w 1 corresponds to the W-phase voltage.

The inverter circuit unit 51 supplies the three-phase voltage according to _{the command values cv u} 1, cv _v 1, and cv _{w 1 to the motor 15.} The control unit 4 controls the electric power supplied to the electric motor 15 by PWM-controlling the inverter circuit unit 51.

The motor 15 is driven by the electric power (three-phase voltage) supplied from the inverter circuit section 51 to generate rotational power.

As a result, the control unit 4 controls the weakening magnetic flux current so that the weakening magnetic flux current flowing through the coil 141 of the electric motor 15 has a magnitude corresponding to the command value cid1 generated by the magnetic flux control unit 46. Further, the control unit 4 controls the angular velocity of the motor 15 so that the angular velocity of the motor 15 corresponds to the command value cω1 generated by the command value generation unit 41.

The step-out detection unit 48 detects the step-out of the motor 15 based on the current measurement values id1 and iq1 acquired from the second coordinate converter 45 and the command values cvd1 and cvq1 acquired from the current control unit 43. To do. When step-out is detected, the step-out detection unit 48 transmits a stop signal cs1 to the inverter circuit unit 51 to stop the power supply from the inverter circuit unit 51 to the motor 15.

The operation mode will be described below.

The control unit 4 operates in the first mode in which a weakening magnetic flux current is passed through the coil 141 of the motor 15 when the switching condition is satisfied. That is, when the switching condition is satisfied, the control of the control unit 4 becomes the weak magnetic flux control.

The switching condition includes, for example, a high-speed range condition that the motor 15 is operating in the high-speed range. The fact that the electric motor 15 operates in the high speed range generally means that the rotational speed of the electric motor 15 is relatively high. The definition that "the motor 15 is operating in the high speed range" is defined as the duty of PWM (Pulse Width Modulation) control of the control unit 4 with respect to the inverter circuit unit 51 when the rotation speed of the motor 15 is equal to or higher than a predetermined rotation speed. The degree of modulation) is equal to or higher than the specified value. The duty of the PWM control is a value obtained by dividing the ON period in one cycle of the PWM signal by the length of one cycle. The rotation speed of the electric motor 15 is substantially proportional to the duty. The above-mentioned specified value is, for example, about 0.9 or 0.95.

Further, the switching condition includes, for example, a torque current condition that the torque current value (q-axis current value) flowing through the coil 141 of the motor 15 is equal to or less than a predetermined current value. The control unit 4 uses the current measurement value iq1 as the torque current value in order to determine whether or not the switching condition is satisfied. However, the control unit 4 may use the command value iq1 of the torque current value as the torque current value.

Here, the switching condition includes both the high-speed range condition and the torque current condition, but only one of them may be included. The switching condition may include only the torque current condition, for example.

The control unit 4 satisfies the switching condition in a low load region where the load (torque) received from the outside by the output shaft 16 of the motor 15 via the output shaft 21 and the drive shaft 22 is relatively low (including no load). , Weak magnetic flux control is performed. Thereby, the maximum rotation speed (maximum rotation speed) of the electric motor 15 can be increased. That is, the control unit 4 performs the weakening magnetic flux control when the load received from the outside by the output shaft 16 of the electric motor 15 is smaller than a predetermined magnitude.

The control unit 4 operates in the second mode in which the weakening magnetic flux current is not passed when the switching condition is not satisfied. That is, when the switching condition is not satisfied, the control of the control unit 4 becomes normal control. The control unit 4 can obtain a relatively large torque by performing normal control in a high load region where the electric motor 15 requires a relatively large torque current.

Note that the weakening magnetic flux control and the normal control may be manually switched by operating an operation unit different from the trigger switch 29. The weakening magnetic flux control and the normal control may be switched by a tap operation or the like on the display unit A3 (see FIG. 1) described later.

(2.3) Suppression of decrease in rotation speed By the way, FIG. 3 is a graph for explaining the operating characteristics of the power tool of the comparative example. The characteristic C1 in FIG. 3 shows the TN curve (relationship between load and rotation speed (rpm)) with respect to the motor 15. As the load (torque) increases, the maximum rotation speed of the motor decreases. For example, assuming that the pull-in amount of the trigger switch 29 by the user is maintained constant, if the load is a predetermined value L1 or less, the motor 15 becomes the rotation speed N1 of the target value corresponding to the current pull-in amount. (See characteristic B1 in FIG. 3). However, when the load exceeds the predetermined value L1, the rotation speed N1 cannot be maintained, and thereafter, even if the pull-in amount is kept constant, the rotation speed of the motor 15 decreases along the TN curve. Go (see characteristic B2 in FIG. 3). Therefore, there is a possibility that the user feels uncomfortable that the rotation becomes slower as the load increases (decrease in operation feeling). In addition, the work efficiency of the user may be reduced.

Therefore, the control unit 4 of the power tool 1 of the present embodiment controls so as to increase the exciting current according to the increase in the load. Here, as an example, the control unit 4 performs weakening magnetic flux control in which a weakening magnetic flux current flows through the coil 141 as an exciting current when the rotation speed of the motor 15 decreases due to an increase in load. That is, as an example, the control unit 4 determines that the rotation speed of the electric motor 15 has decreased, and thus considers that the load has increased.

The magnetic flux control unit 46 of the control unit 4 monitors the rotation speed (here, the angular velocity) of the motor 15. The magnetic flux control unit 46 determines whether or not the angular velocity ω1 of the motor 15 acquired from the estimation unit 47 is lower than the current command value cω1 (target angular velocity) according to the pull-in amount of the trigger switch 29 (that is, lower than the rotation speed). Whether or not) is determined. Here, the control unit 4 satisfies the "trigger condition" that the pull-in amount is, for example, constant (however, larger than zero (0)) at a predetermined interval, and the angular velocity ω1 of the motor 15 decreases due to an increase in the load. , Performs weakening magnetic flux control. The magnetic flux control unit 46 acquires the command value cω1 from the command value generation unit 41 at a predetermined sampling cycle, and the predetermined interval is assumed to be, for example, an integral multiple of 1 or more of the sampling cycle of the command value cω1. , Not particularly limited. The magnetic flux control unit 46 operates in the first mode (weak magnetic flux control) if both the trigger condition and the "angular velocity condition" that the angular velocity ω1 acquired from the estimation unit 47 is lower than the target angular velocity are satisfied. For example, the magnetic flux control unit 46 switches from the second mode to the first mode when both the trigger condition and the angular velocity condition are satisfied during operation in the second mode (normal control).

That is, the weakening magnetic flux control of the present embodiment satisfies both the first weakening magnetic flux control executed when the above-mentioned "switching condition is satisfied in the low load region" and the "trigger condition and angular velocity condition". Includes a second weakening flux control that is performed in the case. The "low load region" in which the first weakening magnetic flux control is executed is assumed to be at least a region lower than the predetermined value L1. Then, the maximum rotation speed of the motor 15 in the low load region of the TN curve can be increased by the first weakening magnetic flux control.

Hereinafter, the second weakening magnetic flux control will be described. In the second weakening magnetic flux control, the control unit 4 determines the magnitude of the exciting current so that the amount of change in the rotation speed of the motor 15 due to the change in the load is reduced. The magnetic flux control unit 46 makes the command value cid1 larger than zero (0) so that the amount of change is reduced, and causes a weakening magnetic flux current (minus exciting current) to flow. The command value cid1 is determined so that the angular velocity ω1 that has decreased with the increase in load returns to the current target angular velocity. The command value cid1 is adjusted so that the larger the amount of change (here, the amount of decrease) of the angular velocity ω1 with respect to the target angular velocity, the larger the amount. The control unit 4 stores in its own memory corresponding data in which a plurality of command values cid1 and a plurality of reduction amounts of the angular velocity ω1 (which may be the number of rotations) are associated with each other. The magnetic flux control unit 46 calculates the amount of decrease in the angular velocity ω1 with respect to the current target angular velocity, and selects the command value cid1 corresponding to the calculated amount of decrease from the corresponding data. The command value cid1 may be constant (fixed value) regardless of the amount of decrease in the angular velocity ω1 as long as it is larger than zero (0) in the second weakening magnetic flux control. In the second weakening magnetic flux control, even when the command value id1 is a fixed value, the amount of change in the rotation speed of the motor 15 due to the change in load can be reduced.

Here, the control unit 4 of the present embodiment maintains the rotation speed of the motor 15 at the target value (corresponding to the target angular velocity here) corresponding to the operation input to the trigger switch 29 (operation unit) even if the load changes. The magnitude of the exciting current is determined so as to be. For example, the magnetic flux control unit 46 increases the command value cid1 so that the rotation speed of the motor 15 is maintained substantially flat even when the load exceeds the predetermined value L1, and the magnetic flux current (minus exciting current) is weakened. To increase. In short, as shown in FIG. 4, the magnetic flux control unit 46 increases the command value cid1 so that the rotation speed of the motor 15 is maintained at the rotation speed N1 and is in line with the characteristic D1 which is an extension of the characteristic B1. FIG. 4 is a graph for explaining the operating characteristics of the power tool 1 of the present embodiment. The characteristic C1 and the characteristic B1 in FIG. 4 are common to the characteristic C1 and the characteristic B1 in FIG.

In particular, the control unit 4 continuously changes the magnitude of the exciting current. That is, the control unit 4 continuously increases the magnitude of the exciting current as the load increases. The "continuous change" of the exciting current makes it easier for the rotation speed of the motor 15 to be kept substantially flat (see curve E1 in FIG. 4). However, the control unit 4 may change (increase) the magnitude of the exciting current discontinuously (that is, stepwise) with respect to the increase in the load.

Since the control unit 4 of the present embodiment determines the increase in the load by the decrease in the rotation speed (angular velocity) of the electric motor 15, the rotation speed of the electric motor 15 is actually on the side from the characteristic D1 to the characteristic C1. It can be controlled to follow a curve E1 (see FIG. 4) that is slightly offset to. Since the consumption of the battery 320 of the power supply unit 32 may increase due to the increase in the exciting current, when the load increases to the extent that the load exceeds a certain threshold value (a value sufficiently higher than the predetermined value L1), the load becomes large. It is preferable to stop following the increase. The curve E1 can eventually reach the characteristic C1.

Further, in the present embodiment, the magnetic flux control unit 46 increases the command value cid1 to increase the weakening magnetic flux current so that the rotation speed (angular velocity ω1) of the electric motor 15 does not exceed the target value (target angular velocity). However, if, for example, the load is reduced and the angular velocity ω1 becomes larger than the angular velocity during the second weakening magnetic flux control, the magnetic flux control unit 46 conversely causes the command value side1 to reduce the weakening magnetic flux current. To reduce.

By the way, as shown in FIG. 1, the control unit 4 of the present embodiment further includes a notification unit A1 and a setting unit A2. In other words, the control unit 4 further has a function as a notification unit A1 and a function as a setting unit A2.

The notification unit A1 is configured to notify the user, for example, that the magnetic flux control unit 46 is operating in the second weakening magnetic flux control. Specifically, the notification unit A1 displays a character message indicating that the power tool 1 is operating with the second weakening magnetic flux control on the touch panel type liquid crystal display (display unit A3: see FIG. 1). And notify the user. The notification unit A1 may output a voice message from a speaker provided in the power tool 1 instead of (or in addition to) the character message to notify the power tool 1. Further, the notification unit A1 may notify by changing the lighting state of the indicator lamp provided in the power tool 1. The change in the lighting state may include a change from turning off to lighting, a change from lighting to blinking, and the like. In addition to the second weakening magnetic flux control, the notification unit A1 may also notify the user that it is operating under normal control or first weakening magnetic flux control.

The setting unit A2 is configured to set valid or invalid for control to increase the exciting current. Specifically, the setting unit A2 sets "valid" or "invalid" of the second weakening magnetic flux control according to the operation input received from the user through a tap operation or the like to the display unit A3. The setting unit A2 stores the setting information regarding the validity or invalidity of the second weakening magnetic flux control in the memory of the control unit 4. If the setting information specifies "invalid" for the second weakening magnetic flux control, the magnetic flux control unit 46 maintains the second mode (normal control) even if both the trigger condition and the angular velocity condition are satisfied. .. The operation input may be received through a push button switch, a DIP switch, or the like provided in the power tool 1 in addition to the display unit A3.

Since the control unit 4 has the notification unit A1 and the setting unit A2 in this way, the convenience is improved.

(2.4) Operation of Second Weakened Magnetic Flux Control Hereinafter, an operation related to the second weakened magnetic flux control in the power tool 1 will be described with reference to FIG. In the following, as an example, a case where the user is using the power tool 1 and the power tool 1 is operating in the second mode (normal control) in which the command value cid1 is zero (0). Suppose. Further, it is assumed that the second weakening magnetic flux control is set to "effective".

The control unit 4 is operating in the second mode (normal control) (step S1). The control unit 4 determines whether or not the trigger condition is satisfied, that is, whether or not the pull-in amount of the trigger switch 29 is constant at a predetermined interval (step S2). When the control unit 4 determines that the pull-in amount is constant (step S2: Yes), whether or not the angular velocity condition is satisfied, that is, the angular velocity ω1 of the motor 15 is lower than the target angular velocity corresponding to the current command value cω1. Whether or not it is determined (step S3). When the control unit 4 determines that the pull-in amount is not constant (step S2: No), the control unit 4 continues the second mode (normal control).

When the control unit 4 determines that the angular velocity ω1 of the motor 15 is lower than the target angular velocity (step S3: Yes), the control unit 4 switches the operation mode from the second mode to the first mode (second weakening magnetic flux control) (step S4). When the control unit 4 determines that the angular velocity ω1 of the motor 15 substantially matches the target angular velocity (step S3: No), the control unit 4 continues the second mode (normal control).

In the second weakening magnetic flux control, the control unit 4 calculates the amount of decrease in the angular velocity ω1 with respect to the target angular velocity, and determines the command value cid1 corresponding to the calculated amount of decrease. After that, as long as the trigger condition is satisfied (step S5: Yes), the control unit 4 increases the command value cid1 so that the rotation speed of the motor 15 is kept substantially flat following the increase in the load. To weaken and increase the magnetic flux current. If the trigger condition is not satisfied during that time (step S5: No), the control unit 4 releases the first mode (second weakening magnetic flux control) (step S6). The condition for releasing the second weakening magnetic flux control is not limited to the trigger condition. The second weakening magnetic flux control may be canceled when the pull-in amount becomes zero (0).

As described above, the control unit 4 of the present embodiment controls so that the exciting current is increased according to the increase in the load received from the outside by the output shaft 16 of the electric motor 15. Therefore, unlike the characteristic B2 of FIG. 3, for example, it is possible to reduce the possibility that the rotation speed of the motor 15 decreases due to the increase in the load and the target rotation speed of the motor cannot be obtained (see curve E1 of FIG. 4). ). Therefore, it is possible to suppress the reduction in efficiency of the motor 15. Therefore, the work efficiency of the user is less likely to decrease.

In particular, since the weakening magnetic flux control is performed by triggering the decrease in the rotation speed of the motor 15 (here, the angular velocity ω1), the efficiency reduction of the motor 15 can be further suppressed.

Further, since the control unit 4 determines the magnitude of the exciting current so that the amount of change in the rotation speed of the motor 15 due to the change in the load is reduced, the control unit 4 uses a sense of incongruity that the rotation slows down as the load increases. It can be difficult to give to a person.

(3) Modified Example The above embodiment is only one of various embodiments of the present disclosure. The above-described embodiment can be changed in various ways depending on the design and the like as long as the object of the present disclosure can be achieved. Further, the same function as the control unit 4 of the power tool 1 according to the above embodiment may be realized by this control method, a computer program, a non-temporary recording medium on which the computer program is recorded, or the like. Specifically, the control method of the electric tool 1 according to one aspect includes a main step of performing vector control for controlling the exciting current and the torque current supplied to the electric motor 15 that drives the driving force transmission mechanism 18. The main step includes at least a sub-step of controlling the output shaft 16 of the motor 15 to increase the exciting current in response to an increase in the load received from the outside.

The following is a list of modified examples of the above embodiment. The modifications described below can be applied in combination as appropriate. Hereinafter, the above embodiment may be referred to as a “basic example”.

The control unit 4 of the power tool 1 in the present disclosure includes a computer system. The main configuration of a computer system is a processor and memory as hardware. When the processor executes the program recorded in the memory of the computer system, the function as the control unit 4 in the present disclosure is realized. The program may be pre-recorded in the memory of the computer system, may be provided through a telecommunications line, and may be recorded on a non-temporary recording medium such as a memory card, optical disk, hard disk drive, etc. that can be read by the computer system. May be provided. A processor in a computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large scale integrated circuit (LSI). The integrated circuit such as IC or LSI referred to here has a different name depending on the degree of integration, and includes an integrated circuit called a system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). Further, an FPGA (Field-Programmable Gate Array) programmed after the LSI is manufactured, or a logical device capable of reconfiguring the junction relationship inside the LSI or reconfiguring the circuit partition inside the LSI should also be adopted as a processor. Can be done. A plurality of electronic circuits may be integrated on one chip, or may be distributed on a plurality of chips. The plurality of chips may be integrated in one device, or may be distributed in a plurality of devices. The computer system referred to here includes a microprocessor having one or more processors and one or more memories. Therefore, the microprocessor is also composed of one or a plurality of electronic circuits including a semiconductor integrated circuit or a large-scale integrated circuit.

Further, it is not an essential configuration that a plurality of functions in the control unit 4 are integrated in one housing. The components of the control unit 4 may be dispersedly provided in a plurality of housings. On the contrary, a plurality of functions in the control unit 4 may be integrated in one housing as in the basic example. Further, at least a part of the functions of the control unit 4, for example, a part of the functions of the control unit 4 may be realized by a cloud (cloud computing) or the like.

In the basic example, the control unit 4 executes the second weakening magnetic flux control so as to increase the weakening magnetic flux current when the load increases. However, the control unit 4 may further have a mode (strong magnetic flux control) for controlling so as to increase the strong magnetic flux current. The stronger magnetic flux current is a positive exciting current. Due to the strong magnetic flux control, the rotation speed of the electric motor 15, that is, the rotation speed of the output shaft 16 (rotation shaft) is reduced. For example, when the load is further increased and exceeds a threshold value sufficiently larger than the predetermined value L1, the magnetic flux control unit 46 causes a strong magnetic flux current to flow so that the rotation speed sharply decreases toward the characteristic C1. May be good.

In the basic example, the weakening magnetic flux control includes the first weakening magnetic flux control and the second weakening magnetic flux control. However, for the power tool 1 in the present disclosure, the first weakening magnetic flux control is not an essential control and may be omitted.

In the basic example, as a condition for executing the second weakening magnetic flux control, it was premised that the "trigger condition" that the pull-in amount was constant at a predetermined interval was satisfied. However, the trigger condition is not an indispensable condition for the power tool 1 in the present disclosure. For example, the control unit 4 determines whether or not the angular velocity condition is satisfied, that is, the angular velocity ω1 of the motor 15 corresponds to the command value cω1 (after the increase) even when the pull-in amount increases at a predetermined interval. It may be determined whether or not it is lower than.

In the basic example, the control unit 4 determines an increase in the load through a decrease in the rotation speed (angular velocity) of the electric motor 15. However, the power tool 1 may further include a detection unit that detects the load. The control unit 4 may perform weakening magnetic flux control (second weakening magnetic flux control) when the detected load increases. In this case, as an example, the detection unit corresponds to the

current sensors

61 and 62 in the basic example. The control unit 4 has a torque current (current measurement value corresponding to the torque component) corresponding to _{the detection result (for example, current measurement value i u} 1 and current measurement value i _v 1) detected by the detection unit (current sensors 61, 62). Based on iq1), it is determined whether or not the load has increased. According to this configuration, since the weakening magnetic flux control is performed by triggering the increase in the load, it is possible to further suppress the reduction in efficiency of the motor 15. Moreover, the load can be easily detected. The above-mentioned detection unit may be provided separately from the

current sensors

61 and 62 of the basic example.

(4) Summary As described above, the electric tool (1) according to the first aspect includes an electric motor (15), a driving force transmission mechanism (18), and a control unit (4). The motor (15) has a permanent magnet (131) and a coil (141). The driving force transmission mechanism (18) is driven by the electric motor (15). The control unit (4) performs vector control for controlling the exciting current and the torque current supplied to the electric motor (15). The control unit (4) controls to increase the exciting current at least in response to an increase in the load received from the outside by the output shaft (16) of the electric motor (15). According to the first aspect, it is possible to suppress the reduction in efficiency of the motor (15).

Regarding the electric tool (1) according to the second aspect, in the first aspect, the control unit (4) is a permanent magnet (131) when the rotation speed of the electric motor (15) decreases due to an increase in load. 1 Weak magnetic flux control is performed in which a weakening magnetic flux current for generating a second magnetic flux that weakens the magnetic flux in the coil (141) is passed through the coil (141) as an exciting current. According to the second aspect, since the weakening magnetic flux control is performed by triggering the decrease in the rotation speed, it is possible to further suppress the reduction in efficiency of the motor (15).

Regarding the power tool (1) according to the third aspect, in the first aspect or the second aspect, the control unit (4) reduces the amount of change in the rotation speed of the electric motor (15) due to the change in load. In addition, the magnitude of the exciting current is determined. According to the third aspect, it is possible to further suppress the reduction in efficiency of the electric motor (15) and to make it difficult for the user of the electric tool (1) to feel uncomfortable that the rotation speed has changed due to a change in load. it can.

The power tool (1) according to the fourth aspect is an operation unit (trigger switch 29) that receives an operation for controlling the rotation of the electric motor (15) in any one of the first to third aspects. Further prepare. The control unit (4) adjusts the magnitude of the exciting current so that the rotation speed of the motor (15) is maintained at the target value corresponding to the operation of the operation unit (trigger switch 29) even if the load changes. decide. According to the fourth aspect, it is possible to further suppress the reduction in efficiency of the electric motor (15) and make it difficult for the user of the electric tool (1) to feel uncomfortable that the rotation speed has changed due to a change in load. it can.

Regarding the power tool (1) according to the fifth aspect, in any one of the first to fourth aspects, the control unit (4) continuously changes the magnitude of the exciting current. According to the fifth aspect, it is possible to further suppress the reduction in efficiency of the electric motor (15) as compared with the case where the magnitude of the exciting current is changed discontinuously (that is, stepwise).

The power tool (1) according to the sixth aspect further includes detection units (current sensors 61, 62) for detecting a load in any one of the first to fifth aspects. The control unit (4) uses the weakening magnetic flux current for generating the second magnetic flux that weakens the first magnetic flux of the permanent magnet (131) in the coil (141) as the exciting current when the detected load increases. The weakening magnetic flux is controlled to flow in 141). According to the sixth aspect, since the weakening magnetic flux control is performed by triggering the increase in the load, it is possible to further suppress the reduction in efficiency of the motor (15).

Regarding the power tool (1) according to the seventh aspect, in the sixth aspect, the control unit (4) is based on the torque current corresponding to the detection result detected by the detection units (current sensors 61 and 62). Determine if the load has increased. According to the seventh aspect, the load can be easily detected.

Regarding the power tool (1) according to the eighth aspect, in any one of the first to seventh aspects, the control unit (4) is set to set valid or invalid for the control for increasing the exciting current. It further has a part (A2). According to the eighth aspect, it is possible to further suppress the reduction in efficiency of the electric motor (15) while improving the convenience.

The control method according to the ninth aspect is a control method of an electric tool (1) including an electric motor (15) having a permanent magnet (131) and a coil (141). The control method includes a main step of performing vector control for controlling the exciting current and the torque current supplied to the electric motor (15) that drives the driving force transmission mechanism (18). The main step includes at least a sub-step of controlling the output shaft (16) of the motor (15) to increase the exciting current in response to an increase in the load received from the outside. According to the ninth aspect, it is possible to provide a control method capable of suppressing the reduction in efficiency of the motor (15).

The program according to the tenth aspect is a program for causing one or more processors to execute the control method in the ninth aspect. According to the tenth aspect, it is possible to provide a function capable of suppressing the reduction in efficiency of the electric motor (15).

The configurations according to the second to eighth aspects are not essential configurations for the power tool (1) and can be omitted as appropriate.

1 Power tool 131 Permanent magnet 141 Coil 15 Motor 16 Output shaft 18 Driving force transmission mechanism 4 Control unit 29 Trigger switch (operation unit)

A2 setting unit

61, 62 Current sensor (detection unit)

Claims

Motors with permanent magnets and coils,
The driving force transmission mechanism driven by the motor and
A control unit that performs vector control to control the exciting current and torque current supplied to the motor, and
With
The control unit controls to increase the exciting current at least in response to an increase in a load received from the outside by the output shaft of the motor.
Electric tool.
The control unit uses the weakening magnetic flux current for generating the second magnetic flux that weakens the first magnetic flux of the permanent magnet in the coil as the exciting current when the rotation speed of the motor decreases due to the increase in the load. Controls the weakening magnetic flux that flows through the coil,
The power tool according to claim 1.
The control unit determines the magnitude of the exciting current so that the amount of change in the rotation speed of the electric motor due to the change in the load is reduced.
The power tool according to claim 1 or 2.
Further provided with an operation unit that accepts an operation for controlling the rotation of the motor.
The control unit determines the magnitude of the exciting current so that the rotation speed of the motor is maintained at a target value corresponding to the operation on the operation unit even if the load changes.
The power tool according to any one of claims 1 to 3.
The control unit continuously changes the magnitude of the exciting current.
The power tool according to any one of claims 1 to 4.
Further provided with a detection unit for detecting the load,
When the detected load increases, the control unit causes the coil to flow a weakening magnetic flux current for generating a second magnetic flux that weakens the first magnetic flux of the permanent magnet as the exciting current. Perform magnetic flux control,
The power tool according to any one of claims 1 to 5.
The control unit determines whether or not the load has increased based on the torque current corresponding to the detection result detected by the detection unit.
The power tool according to claim 6.
The control unit further includes a setting unit for setting valid or invalid for the control for increasing the exciting current.
The power tool according to any one of claims 1 to 7.
A method of controlling an electric tool including an electric motor having a permanent magnet and a coil.
Includes a main step of performing vector control to control the exciting current and torque current supplied to the motor that drives the driving force transmission mechanism.
The main step includes at least a sub-step that controls the exciting current to increase in response to an increase in load received from the outside by the output shaft of the motor.
Control method.
A program for causing one or more processors to execute the control method according to claim 9.