JP5958817B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool including a power transmission unit that can change a reduction ratio.

  2. Description of the Related Art Conventionally, some electric tools control a power transmission unit that decelerates and transmits the rotational power of a motor by a control unit to automatically change a reduction ratio (see, for example, Patent Document 1). In such an electric tool, for example, a load torque applied to an output shaft to which a tip tool (bit) is attached is detected from a drive current supplied to the motor, and the control unit decelerates the power transmission unit based on the detected load torque. Control to change the ratio is performed.

JP 2012-30347 A

  By the way, the power transmission unit becomes larger as the number of gears that can be shifted, that is, the number of reduction gears increases. On the other hand, miniaturization of the entire tool is desired for electric tools, particularly portable electric tools. Therefore, the power transmission unit provided in the electric tool tends to increase the difference in reduction ratio of each stage by limiting the number of shift stages.

  In the above power tool, when the load torque applied to the output shaft increases as the bolt is tightened in the actual work, for example, the work of tightening the bolt using a drill driver, the control unit reduces the speed with a large reduction ratio with respect to the power transmission unit. Control to switch to stage. However, the cause of the increase in the load torque is, for example, that the tip tool (output shaft) is locked, that is, the motor is locked because the bolt is not screwed in correctly in the tightening portion. When the stage is switched, a large reaction is applied from the power tool to the user's hand. In particular, as described above, in an electric tool having a power transmission unit with a large reduction gear ratio difference at each reduction gear stage, the reaction applied to the user from the electric tool immediately after performing a gear shift that increases the reduction gear ratio is larger. Become.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric tool that can suppress a reaction applied to a user after shifting.

In order to solve the above-mentioned problems, the electric tool is configured such that a motor for tightening a bolt by the rotational power of the output shaft, the rotational power of the motor is decelerated and transmitted to the output shaft, and the reduction ratio thereof can be changed. a power transmission portions, a power tool that includes a gear shift actuator to change the speed reduction ratio of the power transmission unit, a torque detection unit for detecting a load torque applied to the output shaft, the detected load torque is e Bei and a control unit that controls the shift actuator so as to increase the speed reduction ratio of the power transmission unit exceeds a threshold value, the control unit performs a control to increase the speed ratio with respect to the power transmission unit The output of the motor is limited until a predetermined time elapses.

  Moreover, the said structure WHEREIN: It is preferable that the said control part eases the output limitation of the said motor according to time passage.

  According to the present invention, the electric power tool can suppress the reaction applied to the user after shifting.

It is a schematic block diagram of the electric tool in embodiment. It is a flowchart for demonstrating the operation example of the electric tool in the same as the above. It is explanatory drawing for demonstrating the operation example of the electric tool in the same as the above. It is a flowchart for demonstrating the operation example of the electric tool in another example. It is explanatory drawing for demonstrating the operation example of the electric tool in the same as the above.

Hereinafter, an embodiment of a power tool will be described with reference to the drawings.
As shown in FIG. 1, the power tool 10 of the present embodiment is a tool used as a drill driver, for example, and has a power tool body 11 and a battery pack 12 that can be attached to and detached from the power tool body 11. . The electric tool main body 11 includes a motor 21 that is driven based on the supply of driving power from the battery pack 12, a power transmission unit 22 that decelerates and outputs the rotational power of the motor 21, and the motor 21. And a control unit 23 for performing general control. The battery pack 12 has a secondary battery composed of a plurality of battery cells (for example, lithium ion batteries).

  A power transmission unit 22 including a speed reduction mechanism, a clutch mechanism, and the like is connected to the rotation shaft 24 of the motor 21. The power transmission unit 22 decelerates the rotational power of the motor 21 and transmits it to the output shaft 25. The power transmission unit 22 includes, for example, two reduction gears (H gear and L gear), and the reduction ratio can be changed in two stages. A tip tool (bit) 26 is attached to the tip of the output shaft 25. Accordingly, the electric power tool 10 is configured such that the tip tool 26 rotates together with the output shaft 25 when the rotational power of the motor 21 is decelerated by the power transmission unit 22 and transmitted to the output shaft 25. Note that the L gear included in the power transmission unit 22 is set so as to have a larger reduction ratio (lower speed rotation and higher torque) than the H gear.

  The power transmission unit 22 is provided with a speed change actuator 27 for changing the reduction ratio. The shift actuator 27 is, for example, a motor actuator, and operates by supplying drive power from the shift drive unit 28 based on the control of the control unit 23. The speed change actuator 27 performs a switching operation of the speed reduction stage (deceleration gear) of the power transmission unit 22 based on the control of the control unit 23 via the speed change drive unit 28. In addition, the electric power tool body 11 includes a drive state detection unit 27 a that detects the position of the speed change actuator 27. Then, the control unit 23 detects the position of the speed change actuator 27 by the drive state detection unit 27a, so which of the H gear and L gear constituting the power transmission unit 22 is currently selected. It is possible to detect whether or not. Incidentally, the control unit 23 operates based on the supply of electric power that has undergone voltage adjustment from the battery pack 12. Further, the speed change drive unit 28 is configured by, for example, an H-bridge circuit using a switching element (for example, FET), and the control unit 23 determines the rotation direction of the speed change actuator 27 relative to the motor by a control signal for the speed change drive unit 28. Drive power supplied by PWM control is controlled.

  The motor 21 is driven to rotate based on the supply of drive power generated by a switching drive circuit 29 including, for example, an H bridge circuit using a switching element (for example, FET). The switching drive circuit 29 controls the drive power supplied to the motor 21 from the power supplied from the battery pack 12 by PWM control by the control unit 23. That is, the control unit 23 controls the electric power supplied to the motor 21 via the switching drive circuit 29 and controls the rotation speed of the motor 21.

  The power tool body 11 is provided with a trigger switch 31 that can be operated by the user. The trigger switch 31 includes ON / OFF for starting and stopping the motor 21, and outputs an output signal corresponding to the operation amount (trigger pull-in amount) of the trigger switch 31 to the control unit 23. Then, the control unit 23 controls the power supplied to the motor 21 in the switching drive circuit 29 based on the output signal from the trigger switch 31, and starts and stops the motor 21 and adjusts the rotational speed during operation. Do.

  Between the switching drive circuit 29 and the motor 21, a current detection unit 41 for detecting a drive current supplied to the motor 21 is provided. The current detection unit 41 includes a detection resistor 42 connected between the switching drive circuit 29 and the motor 21, and an amplification circuit (op-amp) that amplifies the terminal voltage of the detection resistor 42 and outputs it as a detection signal to the control unit 23. 43. The control unit 23 detects the drive current based on the detection signal from the current detection unit 41 at every predetermined sampling time, and based on the detected drive current and the deceleration stage of the power transmission unit 22 when the drive current is detected. A load torque applied to the output shaft 25 (tip tool 26) is detected. Further, the control unit 23 detects the lock of the motor 21 based on the detected load torque and controls the motor 21.

  The electric tool 10 is configured such that automatic shift is performed by the control unit 23 switching and controlling the deceleration stage of the power transmission unit 22 through the shift actuator 27 based on the detected load torque. Note that the speed reduction mechanism of the power transmission unit 22 is, for example, a planetary gear speed reduction mechanism, and a sun gear that is driven to rotate about the axis of the rotation shaft 24 of the motor 21 and a planetary gear that is arranged around and meshed with the sun gear. And a ring gear meshed with the planetary gear. The speed change actuator 27 can control the speed reduction stage by changing the position of the ring gear and changing the planetary gear meshing with the ring gear. The controller 23 can detect whether the ring gear has been changed to the correct position by the shift actuator 27 by the drive state detector 27a. And the control part 23 controls the actuator 27 for speed change based on the detection signal of the drive state detection part 27a.

  In the electric power tool 10 configured as described above, when the trigger switch 31 is pulled by the user, an output signal corresponding to the pull-in amount is input to the control unit 23. The control unit 23 controls the switching drive circuit 29 based on the output signal from the trigger switch 31 to control the start / stop of the motor 21 and the rotation speed. The tip tool 26 rotates as the rotational power of the motor 21 is decelerated by the power transmission unit 22 and transmitted to the output shaft 25. Further, the control unit 23 changes the deceleration stage of the power transmission unit 22 to either the H / L gear according to the load torque. In this case, when the load torque is small, the H transmission is selected by the power transmission unit 22, and the tip tool 26 is driven at high speed rotation and low torque. At the time of activation, the H transmission is selected in the power transmission unit 22. When the load torque increases and exceeds the predetermined torque, the power transmission unit 22 selects the L gear, and the tip tool 26 is driven at a low speed and a high torque. Further, the control unit 23 detects the lock of the motor 21 based on the detection signal from the current detection unit 41 and performs control to stop the motor 21. The control unit 23 limits the output of the motor 21 after shifting to the L gear.

Next, an operation example (action) of the electric power tool 10 will be described.
As shown in FIG. 3, when the electric tool 10 is driven by the H gear and the load torque (load current) reaches the threshold current I0 at time t0, the control unit 23 determines that the load torque T is changed to the speed change condition (threshold I0). ), The power transmission unit 22 is controlled to shift the gear from the H gear to the L gear. At this time, the control unit 23 interrupts energization of the motor 21.

  Here, since the torque is proportional to the current, the control unit 23 restricts the current (output) of the motor 21 in three stages according to the passage of time after the shift to the L gear until a predetermined time has passed. . Specifically, restrictions are implemented as follows.

  As shown in FIG. 2, the control unit 23 detects the selection state of the H gear or the L gear by using the drive state detection unit 27a to determine the state of the speed change actuator 27 (step S10). If the control unit 23 determines that the H gear is selected using the drive state detection unit 27a (step S10: NO), the control unit 23 continues the operation with the setting of the H gear.

  When the control unit 23 determines that the L gear is selected using the drive state detection unit 27a (step S10: YES), the control unit 23 determines whether the timer C has started counting time (step S20). .

  When the time measurement by the timer C is before the start (step S20: NO), the control unit 23 resets the time measurement of the timer C once (step S21). Subsequently, the control part 23 starts the time measurement by the timer C (step S22).

  In addition, when the time measurement by the timer C is started (step S20: YES) or the time measurement by the timer C is started (step S22), the control unit 23 performs output restriction according to the elapsed time. Specifically, if the elapsed time from the start of timing is within time t2 (step S30: YES), the control unit 23 sets the upper limit of the load current of the motor 21 as the threshold value I1 (step S31). The control unit 23 sets the upper limit of the load current of the motor 21 as the threshold value I2 if the elapsed time from the start of time measurement is not less than the time t2 (step S30: NO) and within the time t3 (step S32: YES) ( Step S33). If the elapsed time from the start of timing is t3 or more (step S32: NO) and within the time t4 (step S34: YES), the control unit 23 sets the upper limit of the load current of the motor 21 as the threshold value I3 (step S32). S35). When the threshold values I1 to I3 are set in any one of step S31, step S33, and step S35, the control unit 23 sets the switching drive circuit 29 so that the upper limit of the load current of the motor 21 becomes the threshold values I1 to I3. Control (step S11). In this way, by gradually relaxing the load current limit of the motor 21, it is possible to suppress a sudden torque change and reduce the reaction applied to the user.

  As shown in FIGS. 2 and 3, the controller 23 does not set the upper limit of the load current of the motor 21 if the elapsed time from the start of time measurement is the time t4 or more (step S34: NO), that is, the output is limited. No (step S36). And the control part 23 does not set the upper limit of the load current of the motor 21, but controls the switching drive circuit 29 according to the pulling-in amount of the trigger switch 31, etc. The controller 23 releases the limit control of the load current of the motor 21 so that the maximum torque of the motor can be obtained, and the screw can be seated to the end.

Next, the effect of this embodiment will be described.
(1) The control unit 23 limits the output of the motor 21 until a predetermined time elapses after the power transmission unit 22 is controlled to increase the gear ratio, so that the output after the shift is suppressed and used. Reaction to the person can be suppressed.

  (2) Since the control unit 23 relaxes the limit on the load current (output) of the motor 21 as time elapses, it is possible to suppress a sudden torque change and reduce the reaction applied to the user. .

In addition, you may change the said embodiment as follows.
In the above embodiment, the load current of the motor 21 is detected and the output of this load current is limited. However, the present invention is not limited to this. For example, as shown in FIGS. 4 and 5, since the load current of the motor 21 depends on the duty ratio of the switching element (FET) in the switching drive circuit 29, the same effect can be obtained by limiting the duty ratio. Is obtained. In this case, the detection resistor 42 and the amplifier circuit 43 that detect the load current of the motor 21 can be omitted.

  A control example (operation example) having such a configuration will be described with reference to FIGS. The driving method in the H gear and the process of shifting to the L gear are substantially the same as those in the above embodiment, and therefore a part or all of the description is omitted.

  As shown in FIG. 5, when shifting from the H gear to the L gear when shifting to the L gear from the state where the energization of the motor 21 is interrupted, the control unit 23 passes a predetermined time after shifting to the L gear. In the meantime, the duty ratio (output) of the motor 21 is limited in three stages according to the passage of time. Specifically, restrictions are implemented as follows.

  As shown in FIG. 4, the control unit 23 detects the selection state of the H gear or the L gear by using the drive state detection unit 27a to determine the state of the speed change actuator 27 (step S10). When the control unit 23 determines that the L gear is selected using the drive state detection unit 27a (step S10: YES), the control unit 23 determines whether the timer C has started counting time (step S20). .

  When the time measurement by the timer C is before the start (step S20: NO), the control unit 23 resets the time measurement of the timer C once (step S21). Subsequently, the control part 23 starts the time measurement by the timer C (step S22).

  In addition, when the time measurement by the timer C is started (step S20: YES) or the time measurement by the timer C is started (step S22), the control unit 23 performs output restriction according to the elapsed time. Specifically, if the elapsed time from the start of time measurement is within time t2 (step S30: YES), the control unit 23 sets the upper limit of the duty ratio of the motor 21 as the threshold D1 (step S41). The control unit 23 sets the upper limit of the duty ratio of the motor 21 as the threshold value D2 if the elapsed time from the start of timing is the time t2 or more (step S30: NO) and within the time t3 (step S32: YES) ( Step S43). The controller 23 sets the upper limit of the duty ratio of the motor 21 to the threshold value D3 if the elapsed time from the start of timing is t3 or more (step S32: NO) and within the time t4 (step S34: YES) (step S34). S43). When the threshold values I1 to I3 are set in any one of step S41, step S42, and step S43, the control unit 23 sets the switching drive circuit 29 so that the upper limit of the duty ratio of the motor 21 becomes the threshold values D1 to D3. Control (step S11). Thus, by relaxing the restriction on the duty ratio (output) of the motor in stages, the same effect as the effect (2) of the above-described embodiment can be obtained.

  As shown in FIGS. 4 and 5, the controller 23 does not set the upper limit of the duty ratio of the motor 21 when the elapsed time from the start of time measurement is equal to or longer than the time t4 (step S34: NO), that is, the output is limited. No (step S44). Then, the control unit 23 does not set the upper limit of the duty ratio of the motor 21 and controls the switching drive circuit 29 according to the pull-in amount of the trigger switch 31 and the like. The control unit 23 releases the limit control of the duty ratio of the motor 21 so that the maximum torque of the motor can be obtained, and the screw can be seated to the end.

In the above embodiment, the output limit after shifting to the L gear is set to three stages, but may be one or two stages. Furthermore, it is possible to limit the output in four or more stages.
In the above embodiment, although not particularly mentioned, a rotation detection unit 51 may be provided as shown in FIG. 1 and lock detection may be performed using the rotation speed of the motor 21. The rotation detector 51 is provided on the rotating shaft 24 of the motor 21, for example. The rotation detection unit 51 includes a sensor magnet 52 that is fixed to the rotation shaft 24 so as to be integrally rotatable and has a plurality of magnetic poles, and a Hall element 53 that is disposed to face the sensor magnet 52. The hall element 53 outputs a change in magnetic flux based on the rotation of the sensor magnet 52 to the control unit 23 as a detection signal. The control unit 23 detects the rotation speed of the motor 21 based on the detection signal from the rotation detection unit 51. Further, the control unit 23 detects the lock of the motor 21 also by this change in the rotational speed. Specifically, the control unit 23 detects the lock based on the rotation speed of the motor 21 detected by the rotation detection unit 51. The rotation speed of the motor 21 is reduced at a stroke when the lock is generated. Therefore, the control unit 23 is configured to detect lock based on both the load torque T and the rotation speed. For example, the control unit 23 determines that the lock has not occurred when the rotation speed is not decreased or the degree of decrease is low. As a result, the lock detection accuracy is increased.

  In the above embodiment, the detection of the load torque T is indirectly detected from the load current supplied to the motor 21, but the present invention is not limited to this. For example, you may use the structure which can measure the torque with respect to the output shaft 25 directly.

In the above embodiment, the power transmission unit 22 is configured to switch between two reduction ratios, but may be configured to switch between three or more reduction ratios.
In the above embodiment, the speed change actuator 27 is a motor actuator. However, the motor is not limited to a motor, and a solenoid or the like may be used.

  In the above embodiment, the power tool 10 is embodied as a drill driver, but other power tools such as an impact driver, an impact wrench, a hammer drill, a vibration drill, a jigsaw, and a sealing gun may be used.

  DESCRIPTION OF SYMBOLS 10 ... Electric tool, 21 ... Motor, 22 ... Power transmission part, 23 ... Control part, 25 ... Output shaft, 27 ... Shifting actuator, 41 ... Current detection part (torque detection part), T ... Load torque.

Claims (2)

A motor for tightening a bolt by the rotational power of the output shaft; a power transmission portion configured to decelerate the rotational power of the motor and transmit it to the output shaft and change its reduction ratio; and the deceleration of the power transmission portion A power tool including a speed change actuator for changing a ratio ,
A torque detector for detecting a load torque applied to the output shaft, e Bei and a control unit load torque the detection to control the larger the shift actuator so as to the reduction ratio of the power transmission unit exceeds a threshold value,
The electric power tool is characterized in that the control unit limits the output of the motor until a predetermined time elapses after the power transmission unit is controlled to increase a gear ratio. The power tool according to claim 1,
The said control part eases the output restriction | limiting of the said motor according to progress of time, The electric tool characterized by the above-mentioned.