JP2015027710A - Electric power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a workability of an electric power tool.SOLUTION: This electric power tool has an electric power tool body on which a motor, which is equipped with a rotor connected to a work tool and a stator around which a coil is wound, is mounted. An operation mode of the motor is inputted by an input operation part. The operation mode involves a constant speed operation mode in which the motor is constantly held at any one of rotation numbers of a low speed, a high speed and a middle speed therebetween. The rotation number of the motor is controlled by controlling an electrically advanced ignition θ. When a heavy load is applied onto the motor, the operation mode is changed into a heavy load operation mode, and the motor is driven at a high torque and a low rotation.

Description

  The present invention relates to an electric power tool configured to drive a work tool such as a driver bit by a motor.

  Examples of the electric tools configured to drive a work tool using a motor as a drive source include a driver drill, an impact driver, a cutter, and a disc grinder. The driver drill is a power tool that is used to perform a screw tightening operation or a drilling operation of a driven member by using a working tool, also referred to as a tip tool, as a driver bit and rotating it. The impact driver and the impact wrench are electric tools designed to give impact force, that is, impact to the tip tool, and the impact wrench is attached with a socket corresponding to the type of driven member such as a screw. The cutter is used to streak or cut wood or concrete using a disc-shaped cutting wheel or saw blade as a work tool. The disc grinder is a power tool for performing a grinding operation by rotationally driving a grinding wheel as a tip tool.

  In such an electric tool, the number of rotations of the work tool by the motor is set by the operator in accordance with the type of work object. As a method for setting the rotation speed of the motor, conventionally, there is PWM control for changing the duty ratio, and the voltage supplied to the motor coil is controlled by changing the duty ratio. In an electric tool whose rotational speed is controlled by duty ratio control, a low-torque motor must be used in order to obtain high rotation. In a power tool equipped with a low-torque motor, the motor is stopped by an overload protection circuit when the load is heavy.

  Patent Document 1 describes an electric tool that automatically switches between a low-speed / high-torque mode and a high-speed / low-torque mode according to a load applied to the motor by switching the connection of a plurality of coils. Yes.

JP 2013-111734 A

  As described above, in an electric tool in which the voltage is controlled by duty ratio control to set the rotation speed of the motor, it is necessary to use a low torque motor. For this reason, the motor may stop during heavy load work, and there is a problem that workability is poor. On the other hand, according to the load applied to the motor, in the electric tool that automatically switches the rotation speed between the low torque high rotation and the high torque low rotation, the operator depends on the type of work object. The rotation speed cannot be selected. For example, it is not possible to select an operation with medium rotation and medium torque at a light load. For this reason, it is not possible to perform work at an optimum rotational speed according to the work object, and workability deteriorates.

  An object of the present invention is to improve the workability of an electric power tool.

  An electric tool of the present invention is an electric tool for driving a work tool, and an electric tool main body on which a motor including a rotor coupled to the work tool and a stator around which a coil is wound is mounted; An input operation unit that inputs an operation mode, and an energization timing setting that sets an energization timing of at least one of an electrical advance angle and an energization angle with respect to the coil in accordance with the rotation speed input by the operation of the input operation unit Part.

  In this electric power tool, the motor speed is set by the operator operating the input operation unit. The energization timing of at least one of the electrical advance angle and energization angle with respect to the coil is controlled, and the rotation speed of the motor can be set to a low rotation, a high rotation, and an intermediate speed between these. This makes it possible to perform work at low torque and high speed, work at high torque and low speed, and work at medium torque and medium speed according to the type of work object, improving workability with electric tools. To do.

  When the load on the work tool changes and the load applied to the motor changes, the motor rotation speed is driven at the input fixed rotation speed by changing the energization timing. The motor rotation speed is controlled not by voltage control but by energization timing control, so the maximum voltage can be supplied to the motor and the output can be increased without increasing the size of the electric tool. The workability by the electric tool is improved.

It is a perspective view which shows the driver drill which is an example of an electric tool. (A) is a top view which shows the operation panel shown by FIG. 1, (B) is a front view which shows the modification of an operation panel. (A) is sectional drawing which shows the rotor and stator of the motor shown by FIG. 1, (B) is a circuit diagram which shows the inverter circuit which has a switching element. (A) is a time chart showing the on / off timing of the switching element when the electrical advance angle to the stator coil is 0 degree and the conduction angle is 120 degrees, and (B) is an electrical diagram from the state of (A). It is a time chart which shows the on-off timing of a switching element when an advance angle is increased to 30 degree | times. (A) is a time chart showing the on / off timing of the switching element when the electrical advance angle is 0 degree and the conduction angle is 120 degrees, as in FIG. B) is a time chart showing the on / off timing of the switching element when the energization angle is increased to 150 degrees without changing the electrical advance angle from the state of (A). It is a block diagram which shows the control circuit of a motor. It is an operation mode characteristic diagram of the motor when the electrical advance angle is changed according to the load applied to the motor. It is a flowchart which shows the algorithm of the control of an operation mode when changing an electrical advance angle according to the load added to a motor. It is a flowchart which shows the algorithm of the control of an operation mode when changing an electrical advance angle according to the load added to a motor. It is an operation mode characteristic diagram of the motor when the energization angle is changed according to the load applied to the motor. It is a flowchart which shows the algorithm of control of the operation mode in the case of changing an energization angle according to the load added to a motor. It is a flowchart which shows the algorithm of control of the operation mode in the case of changing an energization angle according to the load added to a motor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a driver drill 10 as an example of an electric tool. The driver drill 10 has a casing 11 formed of a resin material, and the casing 11 constitutes a power tool body. The casing 11 includes a grip 12 held by an operator, a motor casing 13 provided at one end of the grip 12, and a battery mounting portion 14 provided at the other end. A motor 15 is mounted in the motor casing 13, and a tip tool, that is, a work tool 17 is detachably mounted on a chuck 16 that is connected to the rotor of the motor 15 and is driven to rotate by the rotor.

  The electric tool shown in FIG. 1 is a driver drill 10, and a state where a driver bit as a work tool 17 is attached to the chuck 16 is shown in FIG. 1. A battery pack 18 is detachably mounted on the battery mounting portion 14, and power is supplied to the motor 15 from the battery in the battery pack 18. The casing 11 is provided with a trigger switch 19 adjacent to the grip 12. When the operator operates the trigger switch 19, the work tool 17 is rotationally driven by the motor 15.

  As shown in FIG. 1, an operation panel 21 is provided in the casing 11 as the electric tool main body. As shown in FIG. 2A, the operation panel 21 includes an input operation unit 22 for inputting the operation mode, and a display unit 23 for displaying the operation mode input by the input operation unit 22 being operated by the operator. have. The input operation unit 22 is a push button type, and when the input operation unit 22 is pressed, the rotation speed of the work tool 17, that is, the rotation speed, can be any of the low speed mode, the medium speed mode, and the high speed mode. Is set. As the medium speed mode, one type of rotation is set. When the driver drill 10 is in the low speed mode, the display unit 23 lights the LED (1), and when the driver drill 10 is in the medium speed mode, the two LEDs (1) and (2) are lit, When it is, the three LEDs (1) to (3) are lit. Thereby, when the operator performs an operation on the work object using the driver drill 10, the input operation mode can be confirmed by the display unit 23. However, any one LED may be turned on according to each mode.

  FIG. 2B is a modification of the operation panel 21, and the operation panel 21 is provided with a dial type input operation unit 22. By rotating the input operation unit 22 in FIG. 2B, the rotation speed of the work tool 17 is set to the low speed mode, the high speed mode, and the intermediate speed mode of any intermediate rotation speed between them. When the input operation unit 22 is rotated clockwise in FIG. 2B, the rotation speed of the work tool 17 as the operation mode is increased, and when the input operation section 22 is rotated in the reverse direction, the rotation speed is decreased. The operation panel 21 includes a remaining amount display unit 24 for displaying the remaining amount of the battery in the battery pack 18 and a lighting switch 25 for turning on and off an illumination lamp (not shown) provided in the casing 11. Is provided. The remaining amount display unit 24 includes a plurality of LEDs (a) and LEDs (b). When the remaining amount of the battery decreases, the number of LEDs to be lit decreases.

  As shown in FIG. 3A, the motor 15 includes a rotor 31 provided on the motor main shaft 30 and a stator 32 disposed on the outer side of the rotor 31, and the chuck 16 rotates through the motor main shaft 30. 31. The motor 15 is a three-phase brushless motor, the rotor 31 has four permanent magnets 33, and the stator 32 is provided with a three-phase coil. The stator 32 has six stator cores 34, and coils of U1, U2, V1, V2, W1, and W2 phases are formed by windings wound around the stator cores 34, respectively. The U1 phase and U2 phase coils are connected to each other, and the same applies to the V phase and W phase coils. In order to detect the circumferential position of the rotor 31 with respect to the stator 32, the motor 15 is provided with position sensors H1 to H3 made up of Hall elements.

  FIG. 3B shows an inverter circuit 35 connected to each coil. The inverter circuit 35 has two switching elements Tr1, Tr2 connected in series, two switching elements Tr3, Tr4, and two switching elements Tr5, Tr6, respectively. The battery 36 is connected to the positive and negative electrodes of the battery 36. One connection terminal of the U-phase coil is connected between the two switching elements Tr1 and Tr2. One connection terminal of a V-phase coil is connected between the two switching elements Tr3 and Tr4. One connection terminal of a W-phase coil is connected between the two switching elements Tr5 and Tr6. The other connection terminals of the U-phase, V-phase, and W-phase coils are connected to each other. For example, when a control signal is supplied to the bases of the switching element Tr1 and the switching element Tr4, current is supplied to the U-phase and V-phase coils. By adjusting the timing of the control signal supplied to each switching element, the electrical advance angle and energization angle of each coil, that is, the energization timing, is adjusted according to the rotation angle of the rotor 31 with respect to the stator 32. Although the switching elements Tr1 to Tr6 shown in FIG. 3B are bipolar types, various semiconductor elements such as MOS type can be used as the switching elements.

  4 and 5 are time charts showing the on / off timings of the position sensors H1 to H3 and the on / off timings of the switching elements Tr1 to Tr6 according to the rotation angle of the rotor 31 with respect to the stator 32. FIG. When each of the switching elements Tr1 to Tr6 is on, a current is supplied to the coil through the switching elements that are on. 4 and 5, the rotor rotation angle is set to 0 degree when the relative rotation position of the rotor 31 with respect to the stator 32 is in the positional relationship shown in FIG.

  The position sensors H1 to H3 are switched on and off when the circumferential boundary of the permanent magnet 33 of the rotor 31 crosses the position sensors H1 to H3. Since the rotor 31 is provided with four permanent magnets 33, the position sensors H1 to H3 are switched on and off each time the rotor 31 rotates 90 degrees. Since the three position sensors H1 to H3 are arranged in the motor 15 so as to be shifted by 60 degrees in the circumferential direction, the ON / OFF switching timing is shifted by 60 degrees from each other.

  FIG. 4A shows the ON / OFF timing of the switching element when the electrical advance angle θ is 0 degree and the electrical conduction angle α is 120 degrees. FIG. 4B shows the on / off timing of the switching element when the electrical advance angle θ is increased to 30 degrees from the state of FIG. For example, when the rotor 31 rotates 180 degrees from the 0 degree position shown in FIG. 3A, the switching element Tr1 is switched from off to on, and current is supplied to the U-phase coil. A current is supplied to each coil in a range in which the rotor 31 rotates 60 degrees, and a current is supplied in a total range of 120 degrees while the rotor 31 rotates in 360 degrees. It is a degree. As shown in FIG. 4B, when the electrical advance angle θ is changed from 0 degrees to 30 degrees, the electrical advance angle is advanced to a rotation angle that the rotor 31 is advanced by 30 degrees relative to the stator 32. When the electrical advance angle θ is thus increased, the number of revolutions of the motor 15 can be increased without changing the voltage. When the electrical advance angle θ is increased from 30 degrees to 60 degrees, the motor rotational speed becomes higher, and when the electrical advance angle is increased from 60 degrees to 90 degrees, the motor rotational speed becomes higher.

  Therefore, for example, the voltage supplied to the coil is constant, the electrical advance angle θ for rotating the motor 15 in the lowest speed, that is, the low speed mode, is 30 degrees, and the electrical advance angle θ for rotating in the highest speed, that is, the high speed mode Is set to 90 degrees and the electrical advance angle θ is set to an intermediate value between 30 degrees and 90 degrees, the motor rotational speed becomes an intermediate rotational speed between the minimum rotational speed and the maximum rotational speed. If a plurality of intermediate values are set as the intermediate values, a plurality of intermediate rotation speeds can be set. If this intermediate value is set in a stepless manner, a stepless intermediate rotational speed can be set.

  FIG. 5A shows the ON / OFF timing of the switching element when the electrical advance angle θ is 0 degrees and the electrical conduction angle α is 120 degrees, as in FIG. 4A. FIG. 5B is a time chart showing the ON / OFF timing of the switching element when the energization angle α is increased to 150 degrees without changing the electrical advance angle θ from the state of FIG.

  As shown in FIG. 5B, when the energization angle α is changed from 120 degrees to 150 degrees, the rotation angle of the rotor 31 to which current is supplied to each coil increases. When the energization angle α is thus increased, the rotation speed of the motor 15 can be increased without changing the voltage. Increasing the energization angle α to 140 degrees rather than 120 degrees increases the motor rotation speed, and increasing the energization angle α to 160 degrees rather than 140 degrees increases the motor rotation speed further.

  Therefore, for example, the voltage supplied to the coil is constant, the conduction angle α for rotating the motor 15 in the low speed mode is 120 degrees, the conduction angle α for rotating in the high speed mode is 160 degrees, and the conduction angle When α is set to an intermediate value between 120 degrees and 160 degrees, the motor rotation speed becomes an intermediate rotation speed between the low-speed rotation and the high-speed rotation. If a plurality of intermediate values are set as the intermediate values, a plurality of intermediate rotation speeds can be set. If this intermediate value is set in a stepless manner, a stepless intermediate rotational speed can be set.

  As described above, when one of the electrical advance angle θ and the energization angle α as the energization timing is changed, the motor rotation speed can be changed without changing the voltage supplied to the coil. Also, the motor rotational speed can be changed by changing both the electrical advance angle θ and the energization angle α. In other words, the motor rotational speed can be set to an arbitrary rotational speed by changing the energization timing of at least one of the electrical advance angle θ and the energization angle α.

  The motor rotation speed is set by the operator operating the input operation unit 22 and inputting the operation mode. When no load is applied to the work tool 17, that is, when there is no load, the motor rotation speed is set to the input rotation speed. Further, when the driver drill 10 is used in a normal operation mode in which an excessive load is not applied to the work tool 17, the constant speed operation mode is set and the motor rotation speed is adjusted to the same value as when there is no load. The motor rotation speed in the constant speed operation mode is automatically controlled by changing the energization timing described above according to the load applied to the motor 15. On the other hand, when an excessive load is applied to the work tool 17, the motor 15 is automatically switched to the heavy load operation mode, and the motor 15 is driven at a high torque and a low speed. However, the motor 15 may be stopped when an excessive load is applied.

  FIG. 6 is a block diagram showing a motor control circuit. The motor control unit 41 has a controller 42 to which a signal from the input operation unit 22 is sent, and a motor rotation number signal set by the operator operating the input operation unit 22 is input to the controller 42. The A control signal is sent from the controller 42 to the inverter circuit 35 via the control signal output circuit 43. In the inverter circuit 35 shown in FIG. 6, MOS type semiconductors are used as the respective switching elements Tr1 to Tr6, and an energization timing signal is output from the control signal output circuit 43 to the gates of the respective switching elements Tr1 to Tr6. Is done. The electric advance angle θ and the energization angle α described above are adjusted by the energization timing signal sent to the gate.

  Detection signals from the position sensors H <b> 1 to H <b> 3 are sent to the rotor position detection circuit 44. From the rotor position detection circuit 44, a signal corresponding to the rotation angle of the rotor 31 with respect to the stator 32 is output to the controller 42. The rotor position detection circuit 44 sends a signal to the motor rotation speed detection circuit 45, and the motor rotation speed detection circuit 45 outputs a signal corresponding to the motor rotation speed to the controller 42. The controller 42 includes a microprocessor that calculates a control signal and a memory that stores a control program, an arithmetic expression, data, and the like. The microprocessor provided in the controller 42 includes an electrical advance angle θ and an energization angle. An energization timing setting unit for setting energization timing such as α is configured.

  When the trigger switch 19 shown in FIG. 1 is operated, respective signals are sent to the controller 42 via the switch operation detection circuit 46 and the applied voltage setting circuit 47. The electric power of the battery 36 is supplied from the control circuit voltage supply circuit 48 to the motor control unit 41 and the control circuit voltage detection circuit 49. The voltage of the battery 36 is detected by the current / voltage detection circuit 51, and a detection signal is sent to the controller 42.

  A motor current detection circuit 52 is provided in the motor control unit 41 in order to detect a load applied to the motor 15 when work is performed using the driver drill 10 by the work tool 17. By detecting the current flowing through the motor 15 by the motor current detection circuit 52, the load applied to the motor 15 is detected. Thereby, when the driver drill 10 is being used in the no-load state and in the constant speed operation mode, the motor 15 is driven at a constant motor rotation speed set by the operation of the input operation unit 22. On the other hand, when an excessive load is applied to the work tool 17, the motor 15 is automatically switched to the overload operation mode, and the motor 15 is driven at a high torque and a low speed. As an index for detecting the load applied to the motor 15, the motor rotation speed, the battery voltage, and the battery current may be used as an index instead of detecting the motor current.

  FIG. 7 is an operation mode characteristic diagram showing control of the operation mode when the electrical advance angle is changed according to the load applied to the motor from the work tool. The load applied to the tip tool is obtained by detecting the motor current I. 7A to 7D show changes in the operating voltage V, the electric advance angle θ, the motor rotation speed, that is, the motor rotation speed N, and the motor torque T according to the motor current I.

  By operating the input operation unit 22 shown in FIG. 2 (A), the motor speed in the no-load and constant speed operation modes is three stages: a low speed of 15000 rpm, a high speed of 25000 rpm, and a medium speed of 20000 rpm. Can be set to input. The motor torque T is larger at a low motor speed than at a high speed. In no-load and constant speed operation modes, the electrical advance angle θ corresponding to the low speed mode is set to 30 degrees, the electrical advance angle θ corresponding to the high speed mode is set to 90 degrees, and the medium speed mode is supported. The electrical advance angle θ is set to 60 degrees. Therefore, when the motor rotation speed is input by an input operation by the operator before the trigger switch 19 is operated, the electrical advance angle θ corresponding to the input rotation speed is set in advance.

  When the trigger switch 19 is operated, the motor 15 is driven. In this state, when the driver drill 10 performs an operation on the work object, a load is applied to the motor 15 by a load applied to the work tool 17. As shown in FIG. 7B, the electrical advance angle θ is controlled according to the load applied to the motor 15. When the electrical advance angle θ is increased as the load increases, the motor torque T can be increased as shown in FIG. Under this constant speed operation mode, when the load decreases and the motor rotation speed increases, the electric advance angle θ is adjusted according to the decreased load, and the motor rotation speed N is set to the input fixed rotation speed. Maintained.

  When the load applied to the motor 15 exceeds the heavy load determination threshold Ib, the operation mode is switched from the constant speed operation mode to the heavy load operation mode, and the electric advance angle θ is automatically set to 30 degrees of low speed and high torque. Can be switched automatically. In this heavy load operation mode, when the load increases, the motor rotation speed decreases and the motor torque T increases. Thereby, even if a heavy load is applied to the motor 15, the heavy load work can be smoothly performed by the work tool 17. When the work is being performed in the heavy load operation mode, when the load applied to the motor 15 decreases, the operation mode is automatically switched to the normal operation mode according to the load.

  8 and 9 are flowcharts showing an algorithm for controlling the operation mode when the electrical advance angle is changed in accordance with the load applied to the work tool as shown in FIG.

  When the power of the driver drill 10 is turned on, steps S1 to S3 are executed, and the operation mode is set to the low speed mode. In other words, the electrical advance angle θ is initially set to 30 degrees and the motor rotation speed N is set to 15000 rpm, and the LED (1) on the display unit 23 of the operation panel 21 shown in FIG. Under this state, when the trigger switch 19 is operated without operating the input operation unit 22, the motor 15 is rotationally driven at the initially set rotation speed (steps S4 to S6). On the other hand, when it is determined in step S4 that the input operation unit 22 has been operated, steps S7 and S8 are executed, and each time the input operation unit 22 is operated, the medium speed mode and the high speed mode are switched. That is, every time the input operation unit 22 is operated, the electrical advance angle is increased by 30 degrees, and the motor rotation speed N is increased by 5000 rpm. Therefore, when the input operation unit 22 is pushed once under the initial setting, the electrical advance angle θ is increased to 60 degrees, and the motor rotational speed N is increased to 20000 rpm. When the electric advance angle θ is set to 90 degrees and the motor operation speed N is 25000 rpm and the input operation unit 22 is further operated, the maximum electric advance angle θ is 90 in step S9. Since a value exceeding the degree is input, step S10 is executed, and the low speed mode, that is, the electric advance angle θ is returned to 30 degrees, and the motor rotational speed N is returned to 15000 rpm.

  In step S11, the LED of the display unit 23 is turned on according to the input electrical advance angle θ. When the low speed mode is input and the electrical advance angle θ is set to 30 degrees, the LED (1) is lit. When the medium speed mode is input and the electrical advance angle θ is set to 60 degrees, the LED (1 ) (2) lights up. Further, when the high speed mode is input and the electrical advance angle θ is set to 90 degrees, the three LEDs (1) to (3) are lit. If it is determined in step S5 that the trigger switch 19 is turned on under the state where the operation of the input operation unit 22 has been completed, the motor 15 is driven at the set rotation speed N in step S6.

  When work is performed on the work object using the driver drill 10, a load is applied to the work tool 17. In steps S13 and S14, the motor speed N and the operating current I are detected. When it is determined in step S15 that the operating current I does not exceed the above-described threshold value Ib, it is determined in step S16 whether or not the detected motor rotation speed N exceeds the rotation difference determination threshold value Na. When it is determined in step S16 that the motor rotational speed N is higher than the threshold value Na, the electrical advance angle θ is increased by 1 degree in step S17. On the other hand, when it is determined in step S16 that the motor rotation speed N is lower than the threshold value Na, the electrical advance angle θ is decreased by 1 degree in step S18. As a result, the motor 15 enters the constant speed operation mode under a state in which a load is applied to the work tool 17, and the motor 15 is rotationally driven at the input constant rotation speed. When the electrical advance angle θ is increased or decreased by 1 degree, the motor rotation speed N changes by several hundred rotations.

  On the other hand, when it is determined in step S15 that the operating current I exceeds the threshold value Ib described above, a heavy load is applied to the tip tool 17, step S19 is executed, and the operation mode is Switch to load operation mode. When the operation using the driver drill 10 is completed and the trigger switch 19 is turned off, the motor 15 is stopped (steps S20 and S21).

  FIG. 10 is an operation mode characteristic diagram showing operation mode control when the energization angle is changed according to the load applied to the tip tool. In the case shown in FIG. 10, in order to control the rotation speed of the motor 15, as shown in FIG. 5, the motor 15 is operated in the constant speed operation mode by changing the conduction angle α. The load applied to the tip tool is obtained by detecting the motor current I as in the case described above. 10A to 10D show changes in the operating voltage V, the energization angle α, the motor rotation speed N, and the motor torque T according to the motor current I.

  Also in the case shown in FIG. 10, the motor speed in the constant speed operation mode can be input and set in three stages: a low speed of 15000 rpm, a high speed of 25000 rpm, and a medium speed of 20000 rpm. In the no-load and constant speed operation modes, the conduction angle α corresponding to the low speed mode is 120 degrees, the conduction angle α corresponding to the high speed mode is 140 degrees, and the conduction angle α corresponding to the medium speed mode is 160 degrees. It is.

  A work is performed on the work object by the driver drill 10, and a load is applied to the motor 15 by a load applied to the work tool 17. The energization angle α is controlled according to the load applied to the motor 15 as shown in FIG. When the energization angle α is increased as the load increases, the motor torque T can be increased as shown in FIG. Under this constant speed operation mode, when the load decreases and the motor rotation speed increases, the conduction angle α is adjusted according to the decreased load, and the motor rotation speed N is maintained at a set constant rotation speed. The

  When the load applied to the motor 15 exceeds the current threshold value Ib as the heavy load determination value, the operation mode is switched from the constant speed operation mode to the heavy load operation mode, and the conduction angle α is set to 120 degrees of low speed and high torque. It is switched automatically. In this heavy load operation mode, when the load increases, the motor rotation speed decreases and the motor torque T increases. Thereby, even if a heavy load is applied to the motor 15, the heavy load work can be smoothly performed by the work tool 17. When the work is being performed in the heavy load operation mode, when the load applied to the motor 15 decreases, the operation mode is automatically switched to the normal operation mode according to the load.

  FIG. 11 and FIG. 12 are flowcharts showing an algorithm for controlling the operation mode when the energization angle is changed according to the load applied to the work tool.

  When the power of the driver drill 10 is turned on, steps S31 to S33 are executed, and the operation mode is set to the low speed mode. That is, the conduction angle α is initially set to 120 degrees and the motor rotation speed N is set to 15000 rpm, and the LED (1) on the display unit 23 of the operation panel 21 shown in FIG. Under this state, when the trigger switch 19 is operated without operating the input operation unit 22, the motor 15 is driven to rotate at the initially set rotation speed N (steps S34 to S36). On the other hand, when it is determined in step S34 that the input operation unit 22 has been operated, steps S37 and S38 are executed, and each time the input operation unit 22 is operated, the medium speed mode and the high speed mode are switched. That is, every time the input operation unit 22 is operated, the energization angle α is increased by 20 degrees, and the motor rotation speed N is increased by 5000 rpm. Therefore, when the input operation unit 22 is pushed once under the initial setting, the energization angle α is increased to 20 degrees and the motor rotation speed N is increased to 20000 rpm. When the conduction angle α is set to 120 degrees and the motor operation speed N is 25000 rpm, and the input operation unit 22 is further operated, in step S39, the maximum conduction angle α is set to 160 degrees. As a result, an excess value is input, and step S40 is executed to return the low speed mode, that is, the energization angle α to 120 degrees, and the motor rotational speed N to 15000 rpm.

  In step S41, the LED of the display unit 23 is turned on according to the input conduction angle α. When the low speed mode is input and the energization angle α is set to 120 degrees, the LED (1) is turned on. When the medium speed mode is input and the energization angle α is set to 140 degrees, the LED (1) ( 2) lights up. Further, when the high-speed mode is input and the conduction angle α is set to 160 degrees, the three LEDs (1) to (3) are lit. If it is determined in step S35 that the trigger switch 19 is turned on under the state where the operation of the input operation unit 22 has been completed, the motor 15 is driven at the set rotational speed N in step S36.

  When work is performed on the work object using the driver drill 10, a load is applied to the work tool 17. In steps S43 and S44, the motor rotation speed N and the operating current I are detected. When it is determined in step S45 that the operating current I does not exceed the above-described threshold value Ib, it is determined in step S46 whether or not the detected motor rotation speed N exceeds the rotation difference determination threshold value Na. When it is determined in step S46 that the motor rotational speed N is higher than the threshold value Na, the energization angle α is increased by 1 degree in step S47. On the other hand, when it is determined in step S46 that the motor rotational speed N is lower than the threshold value Na, the energization angle α is decreased by 1 degree in step S48. As a result, the motor 15 enters the constant speed operation mode and is driven to rotate at a constant rotational speed under a state where a load is applied to the work tool 17. When the conduction angle α is increased or decreased by 1 degree, the motor rotation speed N changes by several hundred rotations.

  On the other hand, when it is determined in step S45 that the operating current I exceeds the threshold value Ib described above, a heavy load is applied to the work tool 17, and step S49 is executed, so that the operating mode is Switch to load operation mode. When the operation using the driver drill 10 is completed and the trigger switch 19 is turned off, the motor 15 is stopped (steps S50 and S51).

  In the case shown in FIGS. 7 to 9, the motor rotation speed N is controlled by changing the electrical advance angle θ. On the other hand, in the case shown in FIGS. 10 to 12, the conduction angle α is changed. However, the motor rotational speed N may be controlled by changing both the electrical advance angle θ and the energization angle α.

  As described above, in the driver drill 10, the rotation speed of the work tool 17 can be set to a low speed rotation, a high speed rotation, and a medium speed rotation between these. Thereby, not only low-load high-speed rotation and high-load low-speed rotation, but also medium-light and medium-torque work with a light load can be performed, and workability of the electric tool can be improved.

  Even when a load is applied to the work tool 17 when the driver drill 10 is working, the motor 15 is driven at a constant rotational speed in the constant speed operation mode. In the constant speed operation mode, the motor rotation speed is controlled by changing the energization timing such as the electrical advance angle θ and the energization angle α of the current supplied to the coil without changing the voltage supplied to the motor 15. Since it did in this way, the maximum voltage of the battery 36 can be supplied to the motor 15, and the workability | operativity of an electric tool can be improved. Thereby, the output of the working tool 17 can be increased without increasing the size of the battery 36. However, the motor speed may be controlled by combining voltage control with varying duty ratio and control of energization timing.

  When an excessive load is applied to the work tool 17, the operation mode is switched to the heavy load operation mode and becomes a high torque and low speed rotation mode. Can be improved. However, in each case described above, when a heavy load is applied to the motor 15, the motor 15 may be stopped without setting the heavy load operation mode.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the motor 15 is not limited to a three-phase brushless motor, and may be a reluctance motor in which a permanent magnet is not provided in the rotor, and various types can be used. FIG. 1 shows a driver drill as an electric tool, but the electric tool can be applied to any tool as long as the working tool is driven using a motor as a driving source, such as a cutter or an impact wrench. Can be applied.

DESCRIPTION OF SYMBOLS 10 Driver drill 11 Casing 12 Grip 13 Motor casing 14 Battery mounting part 15 Motor 16 Chuck 17 Work tool 18 Battery pack 19 Trigger switch 21 Operation panel 22 Input operation part 23 Display part 24 Remaining quantity display part 25 Lighting switch 30 Motor spindle 31 Rotor 32 Stator 33 Permanent magnet 34 Stator core

Claims (6)

An electric tool for driving a work tool,
A power tool main body on which a motor including a rotor coupled to the working tool and a stator around which a coil is wound is mounted;
An input operation unit for inputting an operation mode of the motor;
An energization timing setting unit that sets an energization timing of at least one of an electrical advance angle and an energization angle with respect to the coil in correspondence with the rotation speed input by the operation of the input operation unit;
A power tool having   When the load applied to the motor changes, the motor rotation speed is set to the rotation speed of the input operation mode by changing at least one of the electrical advance angle and the energization angle according to the load. Item 1. The electric tool according to Item 1.   The electric tool according to claim 1 or 2, wherein when a load exceeding a heavy load determination threshold is applied to the motor, the operation mode of the motor is set to a low load and high torque heavy load operation mode.   The electric tool according to claim 1, wherein the operation mode of the motor includes high rotation, low rotation, and at least one kind of intermediate rotation by the input operation unit.   The electric tool according to any one of claims 1 to 3, wherein the operation mode of the motor includes a high rotation, a low rotation, and an arbitrary intermediate rotation number between the rotations by the input operation unit.   The power tool according to claim 1, wherein a display unit that displays the motor rotation speed is provided in the power tool main body.

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