JP5914841B2 - Electric tool - Google Patents

Description

  The present invention relates to a power tool.

  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 load current (drive current) supplied to the motor, and the control unit is driven by the detected load torque. Control to change the reduction ratio of the transmission unit is performed.

JP 2012-30347 A

  The power transmission unit as described above increases in size 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.

  By the way, in the power tool described above, when the load torque applied to the output shaft increases as the screw is tightened in the actual work, for example, the work of tightening the screw using the drill driver, the control unit reduces the reduction ratio with respect to the power transmission unit. Control to switch to a larger deceleration stage. However, the cause of the increase in the load torque is, for example, that the tip tool (output shaft) is locked because the screw is not screwed into the tightening portion in the correct state, that is, the motor is locked. When switching to the deceleration stage, a large reaction is applied from the power tool to the user's hand or the like. In particular, in an electric tool having a power transmission unit with a large reduction gear ratio difference at each reduction gear stage as described above, 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.

  Therefore, when the load torque is increased to exceed the threshold value of the shift condition set to perform control to increase the reduction ratio and reach the threshold value of the lock condition set to detect the lock of the motor, the power transmission It may be determined that the motor is locked without performing control in the direction of increasing the reduction ratio of the motor. Thereby, it is suppressed that a big reaction is added to a user.

  However, for example, in the screw tightening operation, at the moment when the screw is seated, the load torque is improved, and there is a possibility that the condition is similar to the lock condition. For this reason, there exists a possibility that the operation | work of tightening a screw may be interrupted on the way.

  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 capable of more appropriately performing motor lock detection.

  In order to solve the above-described problem, an electric tool includes a motor, a power transmission unit configured to decelerate and transmit the rotational power of the motor to the output shaft, and to change a reduction ratio thereof, and A speed change actuator that changes the speed reduction ratio, a torque detection portion that detects load torque applied to the output shaft, and the speed change actuator that controls the speed change actuator to change the speed reduction ratio of the power transmission portion in accordance with the detected load torque An electric power tool including a control unit, wherein the control unit is configured to detect a lock of the motor within a predetermined time after performing a control to increase a reduction ratio with respect to the power transmission unit. When the detected load torque reaches the threshold value of the condition, the driving of the motor is stopped, and when the detected load torque does not reach the threshold value within the predetermined time, the driving of the motor is stopped. Characterized in that it continue.

  Further, in the above configuration, a plurality of threshold values set to detect the lock are set to increase with time after performing the control to increase the reduction ratio by the control unit, The controller stops driving the motor when the detected load torque reaches the threshold that changes with time, and the detected load torque does not reach the threshold that changes with time It is preferable to continue driving the motor.

  According to the present invention, the power tool can appropriately perform the speed change operation and the lock detection of the motor.

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

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 includes a power tool body 11 and a battery pack 12 that can be attached to and detached from the power tool body 11. ing. 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. Incidentally, the control unit 23 operates based on the supply of electric power that has undergone voltage adjustment from the battery pack 12. Moreover, the speed change drive part 28 is comprised by the H bridge circuit which used the switching element (for example, FET), for example. The control unit 23 controls the rotation direction of the gear shift actuator 27 with respect to the motor and the drive power supplied by PWM control based on the control signal for the gear shift drive unit 28.

  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. And the control part 23 controls the electric 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 at the time of operation | movement. .

  Between the switching drive circuit 29 and the motor 21, a current detection unit 41 for detecting a load current (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 load current based on the detection signal from the current detection unit 41 at every predetermined sampling time, and based on the detected load current and the deceleration stage of the power transmission unit 22 when the load 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. Further, a drive state detection unit for detecting whether the ring gear is changed to the correct position by the speed change actuator 27 may be provided. In this case, the control unit 23 controls the shift actuator 27 based on the detection signal of the drive state detection unit.

  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. In a state where the L gear is selected, the control unit detects whether or not the lock is achieved with a time factor in addition to the detection of the load torque (current) by the current detection unit 41.

Next, an operation example (action) of the motor 21 will be described.
The controller 23 detects the lock of the motor 21 based on the load torque detected by the current detector 41.

  FIG. 2 shows a graph of the load torque T when the electric tool 10 is driven by the H gear, during shifting, and when driven by the L gear. For example, when a screw tightening operation using the electric tool 10 is performed, the load torque (load current) changes when the operation starts at time t0. More specifically, the load torque of the motor has an inrush current at start-up, and then fluctuates depending on the load during the work. The load current increases. In addition, this load current tends to become more prominent as the length of the screw (length to be screwed) is longer or as the object to be screwed is harder.

  When the electric tool 10 is driven by the H gear and the load torque T reaches the threshold value S1 at time t1, the control unit 23 determines that the load torque T has reached the speed change condition (threshold value S1), and transmits power. The unit 22 is controlled to shift from the H gear to the L gear. At this time, the control unit 23 interrupts energization of the motor 21.

  Here, when the controller 23 resumes energization to the motor 21 after shifting to the L gear, a starting current is generated (time t2). And the control part 23 starts the time measurement by the timer C, after the starting current (rush current) arises after a gear shift in L gear (time t3).

  The control unit 23 is set with a threshold value S3 (lock condition) for detecting lock with respect to the load torque T after shifting (L gear). Then, the control unit 23 determines that the lock has occurred if the load torque T reaches the threshold value S3 and the time elapsed by the timer C is within a predetermined time (between time t3 and t4), and the motor 21 Stop driving. Then, after the start-up current (rush current) is generated after shifting in the L gear (time t3), the control unit 23 drives the motor 21 if the threshold value S3 is not reached within a predetermined time (between time t3-t4). Continue. At this time, since the time measurement by the timer C is after the start-up current is generated as described above, the comparison between the start-up current and the threshold value S3 is prevented. For this reason, it is prevented that the lock determination is made by the starting current.

Next, the effect of this embodiment will be described.
(1) The control unit 23 performs a lock condition set to detect the lock of the motor 21 within a predetermined time (between times t3 and t4) after performing control to increase the reduction ratio with respect to the power transmission unit 22. When the detected load torque (load current) reaches the threshold value S3, the driving of the motor 21 is stopped. And the control part 23 continues the drive of the motor 21, when the load torque detected by threshold value S3 does not reach within predetermined time (between t3-t4). First, after a gear shift with high torque, the lock is determined and the lock is detected within a predetermined time, and the possibility of a large reaction from the electric tool 10 to the user due to the lock of the motor 21 can be reduced. Furthermore, since lock detection is not performed after a predetermined time has elapsed after the gear shift, operations such as screw tightening can be reliably performed until the end (until the screw is seated in the case of screw tightening). Thereby, the lock | rock detection of the motor 21 can be performed appropriately.

  (2) The control unit 23 performs the timing start timing by the timer C from the time t3 when the inrush current after the shift is settled. For this reason, since the comparison between the inrush current and the threshold value S3 is not performed, it is possible to prevent erroneous detection of the inrush current as a lock condition.

In addition, you may change the said embodiment as follows.
In the above embodiment, one threshold value S3 of the lock condition is set for a predetermined time from the time measurement start by the timer C (time t3) to the time t4, but according to the elapsed time from the time measurement start by the timer C. You may employ | adopt the structure which sets a some threshold value. As an example, as shown in FIG. 3, the threshold value of the lock condition is S4a, S4b, S4c, S4d in total for a predetermined time from the start of measurement by the timer C (time t5) to time t9. Set. Here, the threshold value S4a set between the measurement start by the timer C (time t5) and the time t6 is set lower than the other threshold values S4b, S4c, and S4d. Furthermore, the threshold value S4b set between the time t6 and the time t7 is set lower than the threshold values S4c and S4d. Further, the threshold value S4c set between the time t7 and the time t8 is set lower than the threshold value S4d set between the time t8 and the time t9.

  Then, the control unit 23 determines that the lock condition is satisfied when the threshold value S4a is reached during the time t5-t6, stops the driving of the motor 21, and when the threshold value S4a is not reached during the time t5-t6, the control unit 23 Continue driving. Further, when the threshold value S4b is reached during time t6-t7, the control unit 23 determines that the lock condition is satisfied and stops driving the motor 21, and when the threshold value S4b is not reached during time t6-t7, the control unit 23 Continue driving. Further, when the threshold value S4c is reached during time t7-t8, the control unit 23 determines that the lock condition is satisfied and stops driving the motor 21, and when the threshold value S4c is not reached during time t7-t8, the control unit 23 Continue driving. Then, the control unit 23 determines that the lock condition is satisfied when the threshold value S4d is reached during the time t8-t9, stops the driving of the motor 21, and if the threshold value S4d is not reached during the time t8-t9, the control unit 23 Continue driving. FIG. 3 illustrates a state in which the driving of the motor 21 is continued and the screw tightening operation is continued to the end.

  As described above, a plurality of threshold values S4a, S4b, S4c, and S4d set to detect the lock are set to increase with time after the control unit 23 performs control to increase the reduction ratio. Is. And the control part 23 will stop the drive of the motor 21, if the detected load torque reaches threshold value S4a, S4b, S4c, S4d which changes with progress of time. The control unit 23 continues to drive the motor when the detected load torque does not reach the threshold values S4a, S4b, S4c, and S4d that change with time. Here, if the user recognizes that the gear ratio has changed over time, the protection is not necessary. For this reason, it is possible to contribute to improvement in workability by gradually relaxing the threshold value of the lock condition.

  In the above embodiment, when re-driving the motor 21 after shifting to the L gear, the timer C does not start counting while the inrush current is generated. However, the present invention is not limited to this. For example, as shown in FIG. 4, the timing for starting timing may be started immediately after shifting by setting a threshold value in consideration of the inrush current. As an example, a method as shown in FIG. 4 can be considered. As shown in FIG. 4, the control unit 23 starts time measurement by the timer C when driving of the motor 21 is resumed (time t <b> 2). Then, the control unit 23 compares the threshold value S5a with the load current (load torque) until the time t10 when the inrush current is generated after the driving of the motor 21 is resumed. At this time, the control unit 23 determines that the lock condition is satisfied when the threshold value S5a is reached, stops driving the motor 21, and continues driving the motor 21 when the threshold value S5a is not reached. Next, the control unit 23 compares the threshold value S5b with the load current (load torque) at the time t5 when the inrush current settles from the time t10. At this time, the control unit 23 determines that the lock condition is satisfied when the threshold value S5b is reached, stops driving the motor 21, and continues driving the motor 21 when the threshold value S5b is not reached.

Even with this configuration, the same effect as the effect (2) of the above embodiment can be obtained.
-Although not mentioned in particular in the said embodiment, it is good also as a structure which performs a lock | rock detection, for example also at the time of H gear. For example, as shown by a two-dot chain line in FIG. 2, when the tip tool 26 (motor 21) is locked at time tx1, the load torque T increases rapidly. Here, the control unit 23 has a threshold value S1 (shift condition) for changing the reduction gear from the H gear to the L gear with respect to the detected load torque T, and a threshold value S2 (lock condition) for detecting the lock of the motor 21. And are set. The threshold value S2 is set to a torque value larger than the threshold value S1.

  Then, when the load torque T increases at a stretch from the threshold S1 to the threshold S2 in a predetermined short time, the control unit 23 determines that the motor 21 has been locked and stops the motor 21 (time tx2). That is, the control unit 23 determines that the motor 21 has been locked when the load torque T rapidly increases beyond the shift condition threshold S1 within a predetermined short time. When such a lock determination is made, the control unit 23 does not shift to the L gear side even if the load torque T exceeds the threshold value S1.

  In the above embodiment, the control example after the lock detection (after the drive of the motor 21 is stopped) is not mentioned, but for example, the following control method is conceivable. After detecting the lock and stopping the motor 21, the control unit 23 selects the H gear when the trigger switch 31 is continuously pulled or pulled again and the motor 21 is driven again next time. To resume driving.

  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, even when the load torque T exceeds the threshold value S2, 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, an acceleration sensor for detecting the displacement of the power tool 10 (power tool body 11) in the rotation direction of the output shaft 25 may be provided.
For example, as shown in FIG. 5, the control unit 23 is built in the battery pack mounting unit 61 to which the battery pack 12 of the electric power tool main body 11 is mounted, and an acceleration sensor is mounted on the substrate constituting the control unit 23. 62 is implemented. Then, when the rotation of the tip tool 26 (output shaft 25) is locked and the electric tool 10 is rotated, the acceleration sensor 62 detects the displacement of the electric tool 10 as acceleration, and the detection signal is output. Output to the control unit 23. In addition, the arrow 63 shown in FIG. 5 has shown the rotation direction of the electric tool 10 at the time of a lock | rock, and the arrow 64 has shown the direction of the acceleration component to detect. In such a configuration, the control unit 23 can detect the displacement of the electric tool 10 due to the lock, that is, the lock of the motor 21, based on the detection signal from the acceleration sensor 62.

  Incidentally, the acceleration generated in the electric tool 10 increases as the distance from the rotation center of the tip tool 26 (output shaft 25) becomes longer. Therefore, by providing the acceleration sensor 62 as far as possible from the center of rotation, the detection accuracy of the lock can be increased. The installation location of the acceleration sensor 62 may be interposed between the electric power tool body 11 and the battery pack 12 or may be built in the battery pack 12 and output a detection signal to the control unit 23.

  In addition, the acceleration sensor 62 appropriately changes the direction and components of the acceleration to be detected according to the configuration of the electric tool 10. For example, the electric tool 10 such as an electric saw shown in FIG. 6 differs from the drill driver shown in FIG. 5 in the rotation direction of the tip tool 26 (disk-shaped saw), the way the user holds the electric tool 10, and the like. Therefore, the acceleration sensor 62 sets an acceleration component to be detected based on the direction in which the electric tool 10 is displaced (moved) when locked.

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.

Next, a technical idea that can be grasped from the above embodiment and another example will be added below.
(A) In the electric tool according to claim 1 or 2, the control unit starts time measurement by a time measuring unit after control for increasing a reduction ratio with respect to the power transmission unit, and the torque detection unit is connected to the motor. The load torque applied to the output shaft is detected, and the control unit stops the driving of the motor when performing control to change the reduction ratio for the power transmission unit. The timing by the timing unit is started after the load current detected when restarting the driving of the motor after increasing the reduction ratio falls below the threshold set to detect the locking of the motor. An electric tool characterized by

  As a result, it is possible to reduce erroneous detection of an inrush current generated when the motor is restarted as a lock condition, and it is possible to detect lock more appropriately.

  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, S3, S4a , S4b, S4c, S4d, S5a, S5b ... threshold.

Claims (2)

A motor, a power transmission unit configured to decelerate and transmit the rotational power of the motor to the output shaft and change a reduction ratio thereof, a speed change actuator that changes the reduction ratio of the power transmission unit, and an output shaft An electric tool comprising: a torque detection unit that detects a load torque applied to the power transmission unit; and a control unit that controls the shift actuator to change a reduction ratio of the power transmission unit according to the detected load torque,
When the detected load torque reaches the threshold value of the lock condition set to detect the lock of the motor within a predetermined time after performing the control to increase the reduction ratio with respect to the power transmission unit, the control unit An electric tool characterized in that the driving of the motor is stopped and the driving of the motor is continued when the detected load torque does not reach the threshold within the predetermined time. The power tool according to claim 1,
A plurality of threshold values set to detect the lock are set so as to increase with the lapse of time after performing the control to increase the reduction ratio by the control unit,
The controller stops driving the motor when the detected load torque reaches the threshold that changes with time, and the detected load torque does not reach the threshold that changes with time The electric tool characterized by continuing to drive the motor.