JP2011047465A - Automatic gear shifting device for rotary power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic gear shifting device for a rotary power tool, which safely and smoothly changes over reduction gear ratio by preventing a shaft deflection in change over. <P>SOLUTION: This automatic gear shifting device for the rotary power tool includes a change over part changing over to different reduction gear states by moving a change over gear 14 in an axial direction in response to load fluctuation. The change over part includes a bias part 15 biasing the change over gear 14 to only axial direction A by magnetically attracting the same by electromagnetic drive, a detection part 16 detecting load fluctuation, and a control unit controlling power supply to the bias part 15. The control unit electromagnetically drives the bias part 15 when a detection result of the detection part 16 reaches a threshold. The change over gear 14 is magnetically attracted in the axial direction A, and the shaft deflection of the change over gear 14 in change over is prevented, thereby. Thus, the detection accuracy of load fluctuation is improved by the detection part 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an automatic transmission for a rotary electric tool, and more particularly to an automatic transmission that automatically performs a switching operation for changing a reduction ratio in a rotary electric tool in accordance with a load change.

  Conventionally, in a rotary electric tool such as a drill driver, an impact driver, an oil pulse driver, and a rotary wrench, rotational drive from a drive source is decelerated and output by a reduction mechanism. For example, the speed reduction mechanism has a plurality of planetary speed reduction stages, and the first stage planetary speed reduction stage uses a sun gear as the gear attached to the output shaft of the drive source, and connects the internal gear, the planetary gear, and the planetary gear with a connecting pin. And a next-stage sun gear is attached to the carrier.

  In addition, there is one that improves work efficiency by providing a speed change mechanism that changes the speed reduction ratio to a speed reduction mechanism having a plurality of planetary speed reduction stages and switching the speed reduction ratio according to load fluctuations during work. For example, work using a rotating electric tool is a hole opening work, a tightening work, etc., and the work is started by switching to high torque low speed rotation by the above transmission during the work after starting the work with low torque high speed rotation. The working efficiency is improved in response to the increased load due to the progress of.

  In particular, as in Patent Document 1, an automatic transmission is provided in the planetary reduction mechanism, and the reduction ratio is changed automatically according to the load fluctuation during the operation while the automatic transmission is rotationally driven. However, there are those that reduce the burden on the user, such as stopping the use of the rotary electric tool and switching it by manual operation. Specifically, a cam device is provided which switches one reduction gear ratio by moving one internal gear of a multi-stage planetary mechanism as a shift internal gear (switching gear) in the axial direction. The cam device includes an elastic body that restricts the rotation of the other internal gear located below the predetermined torque of the internal gear for speed change, and a rotation when the predetermined torque of the other internal gear is reached. And a reversing spring for biasing the internal gear for shifting in the axial direction. The reversing spring reverses the direction of energization before and after switching of the reduction ratio, and the reversal of the energizing direction holds the shift internal gear at each position before and after switching. Since the direction in which the reversing spring is urged during the axial movement of the speed change internal gear is reversed, the assisting force assists the axial movement of the speed change internal gear.

Japanese Patent No. 3084138

  However, in Patent Document 1, in order to reverse the urging direction of the reversing spring during the switching operation, the reversing spring is provided on the outer peripheral surface of the internal gear for shifting, and the urging force of the reversing spring is inclined with respect to the shaft. It depends on. For this reason, the internal gear for shifting may not move in the axial direction in parallel at the time of switching, causing shaft runout, which may cause problems in the planetary mechanism such as gear breakage.

  Therefore, the present invention has been invented in view of the above circumstances, and by applying an urging force to the switching gear only in the axial direction, shaft switching of the switching gear can be prevented and smooth and stable switching can be achieved. An object of the present invention is to provide an automatic transmission for a rotary electric tool to be performed. In particular, an object is to improve the stability of the shift timing at which the switching of the reduction ratio is started according to the load fluctuation.

  In order to solve the above-mentioned problems, an automatic transmission for a rotary electric tool according to the present invention is provided in a speed reduction mechanism including a planetary speed reduction stage that decelerates rotational drive from a drive source. At least one gear of the planetary reduction stage is a switching gear 14 that changes the reduction ratio of the reduction mechanism, and the switching gear 14 is moved in the axial direction in response to load fluctuations to have different reduction ratios. A switching unit for switching to a state is provided. The switching unit includes a biasing unit 15 that attracts magnetic force by electromagnetic driving to bias the switching gear 14 only in the axial direction A, a detection unit 16 that detects a load variation, and an energization control of the biasing unit 15. And a control unit for performing. The control unit electromagnetically drives the urging unit 15 when the detection result of the detection unit 16 reaches a threshold value. The urging unit 15 electromagnetically driven moves the switching gear 14 in the axial direction in parallel. At the same time, the switching gear 14 is held at the position after the axial movement.

  By adopting such a configuration, the reduction ratio can be switched according to the load fluctuation, the switching operation of the reduction ratio by the user is unnecessary, and the reduction ratio can be changed without interrupting the rotation drive. . In particular, since the urging portion 15 urges the switching gear 14 only in the axial direction A, it is possible to prevent the switching gear 14 from being shaken during the axial movement. And by providing the detection part 16 which detects a load fluctuation | variation, a load fluctuation | variation can be detected and a speed change operation | movement can be performed according to a detection result. Further, since the control unit determines the shift timing at which the switching of the reduction ratio is started, and controls the electromagnetic drive of the urging unit 15 based on the determination result, the urging unit 15 is the switching gear only at the time of switching and after the switching. 14 can be energized.

  In addition, it is preferable to use a displacement sensor 23, a rotation sensor 30, a magnetostrictive torque sensor, and a current detection circuit for the detection unit 16 so that load fluctuations can be numerically detected.

  In addition, it is preferable that the urging unit 15 be a ring-shaped electromagnet because the urging unit 15 can have a simple configuration.

  In addition, since the control unit can change the threshold value to be compared with the detection result, it can be changed to a threshold value corresponding to the load fluctuation in the work content by the rotary electric tool, and the shift timing can be adapted to the work content. This is preferable.

  As described above, the automatic transmission of the rotary electric tool according to the present invention switches the reduction ratio according to the load fluctuation, and the burden on the user can be reduced by eliminating the switching operation by the user. This improves the usability of the rotating power tool. And by moving the switching gear in the axial direction in parallel by the magnetic force attraction of the urging unit, it is possible to prevent the switching gear from running out of the shaft when the reduction ratio changes, and to prevent problems such as gear breakage. Is suppressed, and the tool life can be improved. In particular, since the urging unit is electromagnetically driven to attract the magnetic force, it is possible to eliminate the application of the urging force by the urging unit at the time of non-switching such as before switching or during non-rotation driving. It is possible to suppress the accumulation of magnetic force on the constituent members. And by providing a detection unit that detects load fluctuations, it is possible to detect the load fluctuations numerically, as compared with those that move the switching gear in the axial direction as the load increases, etc. The shift in shift timing due to can be reduced. For this reason, the switching of the reduction ratio is started when substantially the same load is reached, and the automatic reduction ratio can be smoothly switched at a stable shift timing.

  Further, by using a displacement sensor, a rotation sensor, a magnetostrictive torque sensor, or a current detection circuit for the detection unit, it is possible to detect the load fluctuation numerically and improve the detection accuracy of the load fluctuation. In particular, in the case of using a current detection circuit, the sensor member can be dispensed with, the detection unit can have a simple configuration, and the cost can be reduced.

It is sectional drawing of the speed-reduction mechanism of the basic structural example of embodiment of this invention, (a) is a low torque high speed rotation mode, (b) is a high torque low speed rotation mode. It is a disassembled perspective view of the automatic transmission in an example of a detection part. It is explanatory drawing of the rotation operation | movement of the 1st-stage internal gear with respect to a load fluctuation same as the above, (a) is before rotation, (b) is at the time of rotation. It is operation | movement explanatory drawing of a detection part same as the above, (a) is the low torque high speed rotation mode before switching, (b) is immediately after the mode switching start, (c) is the high torque low speed rotation mode after switching. It is. It is operation | movement explanatory drawing of the other example of a detection part, (a) is the low torque high speed rotation mode before switching, (b) is the high torque low speed rotation mode after switching. It is sectional drawing of the principal part of the further another example of a detection part.

  Embodiments of the present invention will be described below with reference to the drawings. For convenience of explanation, each shape is a shape viewed along the axial direction A of the speed reduction mechanism, and the drive source side is the rear side and the output side is the front side along the axial direction A.

  The automatic transmission according to the present invention is provided in a speed reduction mechanism, and the speed reduction mechanism decelerates the rotational drive from a motor (not shown) as a drive source of the rotary electric tool and outputs it to the output shaft 13. . For example, the speed reduction mechanism includes a plurality of planetary stages arranged in a substantially cylindrical gear case 1 as an exterior, and in this example, as shown in FIG. 1, the planetary stages are arranged along the central axis of the cylinder. It is arranged in three stages.

  Specifically, the first planetary stage, which is the first stage, includes a sun gear (not shown in the drawing) attached to one end of a motor drive shaft, an internal gear 3 fixedly held in a gear case 1, and the sun gear. And a planetary gear 2 that meshes freely with the internal gear 3. The planetary gear 2 is held by the carrier 4 via a connecting pin, and the sun gear, the rotation axis of the carrier 4 and the center axis of the ring-shaped internal gear 3 are substantially concentric with the center axis of the gear case 1. It has become. Furthermore, the second stage sun gear 5 which is the next stage is attached to the first stage carrier 4 concentrically.

  The second planetary stage is a gear stage that takes two states, a state in which the internal gear 7 can rotate and a state in which the internal gear 7 cannot rotate. As in the first planetary stage, the planetary gear 6 is always meshed with the sun gear 5 and the internal gear 7, and the planetary gear 6 is held by the carrier 8 via a connecting pin. A third-stage sun gear 9 is attached to the eye carrier 8 in a concentric manner. Further, when the second-stage internal gear 7 is rotatable, it engages with the outer periphery of the first-stage carrier 4 and rotates integrally with the carrier 4. When the second-stage internal gear 7 is not rotatable, it engages with the first-stage carrier 4. It is unwound and engaged with the inner peripheral surface of the gear case 1 so as to be fixedly held on the gear case 1. Therefore, the internal gear 7 is a switching gear 14 that changes the speed reduction ratio of the speed reduction mechanism, and the speed reduction ratio in the state in which the internal gear 7 is not rotatable is larger than the state in which the internal gear 7 is rotatable.

  The third planetary stage, which is the third stage, is a decelerating stage in which the internal gear 11 is provided with a torque clutch (not shown), and the internal gear 11 cannot rotate unless torque regulation is performed by the torque clutch. Is held by. As in the first planetary stage, the planetary gear 10 meshes with the sun gear 9 and the internal gear 11, and the planetary gear 10 is held by the carrier 12 via the connecting pin. An output shaft 13 is attached to the carrier 12. Of course, the last planetary stage may not have a torque clutch.

  In other words, the speed reduction mechanism includes a low torque high speed rotation mode in which the switching gear 14 rotates integrally with the first stage carrier 4 and a high torque low speed mode in which the switching gear 14 is fixed to the gear case 1. . The switching between the two modes is performed by the axial movement of the switching gear 14. Further, of the axial movement of the switching gear 14, a shifting operation from the low torque high speed rotation mode to the high torque low speed rotation mode is performed by the switching unit of the automatic transmission.

  Specifically, the switching unit is based on the detection result of the urging unit 15 that magnetically attracts the switching gear 14 by electromagnetic driving, the detection unit 16 that detects a value that serves as an index of load fluctuation, and the detection unit 16. And a control unit that controls electromagnetic driving of the urging unit 15. And the said detection part 16 detects the value used as the parameter | index of the fluctuation | variation of the load concerning a rotary electric tool, For example, the displacement sensor 23, the rotation sensor 30, a torque sensor, a current detection circuit etc. are used. Detailed description of the above example will be described later.

  The urging unit 15 is disposed between the second stage and the third planetary stage, and exerts an urging force by electromagnetic drive, and the urging force is axially A with respect to the switching gear 14. The switching gear 14 is urged toward the front side along the axial direction A. Specifically, the urging portion 15 is made of a ring-shaped electromagnet that faces the switching gear 14 along the axial direction A and is substantially concentric with the central axis of the gear case 1 and is switched by the magnetic force generated in the electromagnet. The working gear 14 is sucked forward along the axial direction A. The energizing unit 15 is energized and controlled by the control unit, and when the electric power is supplied to the electromagnet, the energizing unit 15 starts electromagnetic driving and attracts the switching gear 14 by magnetic force.

  That is, since the urging force by the urging unit 15 is applied only to the switching gear 14 in the axial direction A, the switching gear 14 is parallel without changing the parallelism of the rotating surface with respect to the shaft when the reduction ratio is switched. It moves in the axial direction. Since the switching gear 14 is energized only on the front side, the switching gear 14 does not move backward even if a load fluctuation occurs due to the switching of the reduction ratio, and the switching gear 14 is moved while the shaft is moving in the axial direction. And reciprocating along the back and forth. Further, since the electromagnetic driving is continued until the rotational driving of the driving source is stopped, the urging unit 15 holds the switching gear 14 at the position of the high torque low speed rotation mode after the mode switching.

  Note that a plurality of electromagnets may be arranged on the concentric circle concentric with the central axis at equal intervals in the circumferential direction. It suffices if it is performed only in the axial direction A. Reference numeral 18 positioned between the switching gear 14 and the biasing portion 15 is a buffer member that absorbs an impact when the switching gear 14 that has been attracted by the magnetic force and moved in the axial direction comes into contact with the biasing portion 15. The urging portion 15 is disposed in a shape that covers substantially the entire contact surface with the switching gear 14 that is the rear surface of the urging portion 15.

  In addition to the energization control of the urging unit 15, the control unit determines whether or not the detection result of the detection unit 16 has reached a threshold value. The load increases and the detection result becomes the threshold value. When it reaches, electromagnetic driving of the urging unit 15 is started. That is, when the detection result of the detection unit 16 reaches the threshold value, the control unit determines that it is a shift timing for switching the reduction ratio, and starts the electromagnetic drive of the urging unit 15 to move the switching gear 14 in the axial direction. It is what The control unit is, for example, an arithmetic unit such as an integrated circuit or a microcomputer.

  As described above, the automatic transmission device switches the reduction ratio according to the load fluctuation, and reduces the burden on the user by eliminating the switching operation by the user, thereby improving the usability of the rotary electric tool. is doing. Then, the switching gear 14 is moved in the axial direction in parallel by the magnetic force attraction of the urging portion 15, so that the switching gear 14 is prevented from shaking during the axial movement, and the components of the speed reduction mechanism are damaged or deformed. The tool life is improved by suppressing the occurrence of such problems. In particular, since the detection unit 16 detects a value that serves as an index of load fluctuation, the timing for switching the reduction ratio can be determined more accurately according to the load fluctuation, and the speed reduction ratio according to the load fluctuation can be accurately determined. It is an automatic transmission that can be switched.

  The urging unit 15 uses an electromagnet that is electromagnetically driven to make the urging force a magnetic force, and the control unit controls the electromagnetic driving of the urging unit 15, so that the urging unit 15 is only at the time of switching and after the switching. A magnetic force that is an urging force is generated. Therefore, it is possible to eliminate the application of the urging force from the urging unit 15 before switching or during non-switching such as during non-rotation driving, and it is possible to suppress the accumulation of magnetic force on the constituent members other than the urging unit 15. It is possible to suppress a decrease in the urging force to the switching gear 14 due to adhesion of debris or the like and an increase in wear of the engaging portion and the gear teeth.

  The switching gear 14 is provided with a substantially ring-shaped groove 17 along the outer periphery, and a switching spring interlocked with a switching handle 19 for forcibly switching the position of the switching gear 14 by an external operation. 20 and a reset lever 22 for returning the switching gear 14 to the low torque high speed rotation mode in conjunction with a trigger switch 21 for driving the drive source. When the switching handle 19 is operated from the outside, the switching spring 20 forcibly moves the switching gear 14 to the front position in accordance with the operation, and switches to the high torque low speed rotation mode regardless of the load fluctuation. . The reset lever 22 releases the external operation of the trigger switch 21 in the high torque low speed rotation mode, thereby moving the switching gear 14 in the axial direction by the spring force to return to the low torque high speed rotation mode. .

  Specifically, when the operation of the trigger switch 21 is released after the operation in the high torque low speed rotation mode, the power supply to the urging unit 15 is stopped by the control unit, and the holding of the position of the switching gear 14 by magnetic attraction is released. . At this time, the spring force accumulated in the reset lever 22 is released with the release of the operation of the trigger switch 21, and the switching gear 14 is moved to the low torque high speed rotation mode position which is the initial position. That is, the reset lever 22 returns the automatic transmission to the initial state by releasing the operation of the trigger switch 21 in which the urging unit 15 is not energized in the high torque low speed rotation mode. In addition, no axial movement force is applied to the switching gear 14.

  As an example of the detection unit 16, as shown in FIGS. 2 to 4, a cam mechanism that converts rotational force into axial movement force is provided, and a displacement sensor 23 that detects the amount of displacement of the cam mechanism in the axial direction A is provided. What is used as the detection unit 16 will be described. In addition, the same code | symbol is provided to the structure same as the structure demonstrated in the above-mentioned example, and description is abbreviate | omitted.

  The detection unit 16 includes a holding unit 25 that can rotate the first-stage internal gear 3 and hold it in the gear case 1, a cam mechanism that converts the rotational force of the first-stage internal gear 3 into an axial movement force, and a shaft of the cam mechanism. And a displacement sensor 23 for measuring a displacement amount in the direction A.

  Specifically, the holding portion 25 includes a protrusion 26 provided on the outer periphery of the internal gear 3 in the first stage, and a setting spring 27 that is an elastic body attached to both ends of the protrusion 26 in the circumferential direction. The rotation of the internal gear 3 is restricted by the biasing of the setting spring 27 along the circumferential direction. That is, when the load applied to the first planetary stage reaches a predetermined value, the first-stage internal gear 3 rotates against the bias of the setting spring 27.

  The cam mechanism includes a cam protrusion 28 protruding along the axial direction A from the front surface of the internal gear 3 at the first stage, and a cam ring 24 having a cam recess 29 corresponding to the cam protrusion 28. The cam recess 29 has an inclination at both ends in the circumferential direction. Therefore, when the holding portion 25 allows the first-stage internal gear 3 to rotate, the cam ring 24 is pushed by the cam protrusion 28 and moves in the axial direction A.

  Further, a displacement sensor 23 for measuring the amount of displacement of the cam ring 24 when moving in the axial direction is provided at the rear periphery of the cam ring 24, and measures the distance L between the front surface of the internal gear 3 at the first stage and the rear surface of the cam ring 24. By doing so, load fluctuations are detected. That is, the detection unit 16 detects an increase in load applied to the speed reduction mechanism from the amount of displacement of the cam ring 24 in the axial direction A. When the displacement amount, which is a detection result of the displacement sensor 23, reaches a set amount that is a threshold value, the control unit starts supplying power to the urging unit 15 as a shift timing for switching the reduction ratio, and the switching gear. 14 is moved in the axial direction to switch to the high torque low speed rotation mode.

  As described above, the detection accuracy of the load fluctuation is improved by the displacement sensor 23, so that the energizing unit 15 can be energized and controlled so that the urging unit 15 does not generate magnetic force until immediately before the start of switching. It is possible to suppress adhesion of metal scraps and the like.

  In this example, the cam ring 24 is disposed between the internal gear 3 of the first stage and the switching gear 14. When the cam ring 24 moves in the axial direction A, the switching gear 14 is moved along the axial direction A. Pushing forward, the switching gear 14 is moved in the axial direction. However, when the cam ring 24 is pushed to move in the axial direction, the switching gear 14 and the first carrier 4 are not disengaged, and the switching gear 14 is fixed to the gear case 1 so as not to rotate. It has never been. That is, the axial movement of the switching gear 14 accompanying the movement of the cam ring 24 does not switch the reduction ratio, but is merely a preparatory operation for the switching, and the reduction ratio does not switch unless the threshold is reached. It has become. The displacement sensor 23 is preferably a non-contact measuring device such as an optical sensor using an infrared ray or an ultrasonic sensor.

  In addition, as long as the member causes displacement according to the load fluctuation, the member for which the displacement sensor 23 measures the distance is not limited to the cam mechanism, and the detection unit 16 detects the load fluctuation by the friction operation by the friction operation member. It may be one that does not require. For example, there is one in which the displacement sensor 23 detects a retreat distance corresponding to a load fluctuation of the drive shaft as a displacement amount. In the case where the friction operation member is not required for the detection operation of the detection unit 16 as described above, there is no deviation in the detection result due to wear or shape deformation due to friction operation. Therefore, it is possible to further suppress the occurrence of shift in shift timing, to perform automatic switching of the reduction ratio that is smoother and more stable, and to simplify and reduce the speed reduction mechanism.

  Further, the distance measured by the displacement sensor 23 is not limited to the one along the axial direction A, and the displacement sensor 23 is provided on the outer periphery of the first-stage internal gear 3 or the like in the rotation direction that is the rotation amount of the first-stage internal gear 3. The distance may be measured as a displacement amount. For example, there is one that measures the amount of rotation when it resists the holding portion 25 of the internal gear 3 in the first stage. As in the case of detecting the amount of displacement of the drive shaft described above, since a frictional operation member is not required, a shift in shift timing can be suppressed, and the speed reduction mechanism can be simplified and downsized.

  A description will be given of the automatic switching of the reduction ratio according to the load variation from the change in the rotational speed using the rotation sensor 30 that counts the rotational speed of the switching gear 14 in the detection unit 16. In addition, the same code | symbol is provided to the structure same as each above-mentioned example, and description is abbreviate | omitted.

  The rotation sensor 30 is, for example, an optical sensor that is not in contact with the switching gear 14 and does not cause an error in the detection result due to the magnetic force of the electromagnet. Specifically, as shown in FIG. 5, every time a marker (not shown) such as a reflective tape provided on the outer periphery of the switching gear 14 is detected, the rotation speed is counted. That is, the rotation sensor 30 counts the number of rotations per unit time that is the rotation speed of the switching gear 14 in the low torque high speed rotation mode, and the counted number of rotations decreases as the load increases. . When the rotation speed reaches a set rotation speed that is a threshold value, the control unit starts electromagnetic driving of the electromagnet, assuming that it is a shift timing.

  Thus, by using the rotation sensor 30 for the detection unit 16, it is possible to detect the load fluctuation numerically and improve the detection accuracy of the load fluctuation. The power at the time of switching, which is the axial movement force of the switching gear 14, can be merely attracted by the urging unit 15, and it is not necessary to provide the detecting unit 16 with a wear operating member such as a cam mechanism. It is possible to prevent an error in the shift timing due to wear or breakage of the gear. In particular, since the switching gear 14 does not move in the axial direction before the urging unit 15 is electromagnetically driven, problems such as the rotation sensor 30 losing sight of the marker are prevented.

  Of course, the rotation sensor 30 may count the rotation speed of other parts such as the internal gear 3 and the output shaft 13 in the first stage without directly counting the rotation speed of the switching gear 14. In addition, the rotation sensor 30 is not limited to the optical sensor, and a magnetic sensor such as a Hall element or a frequency generator can be used as long as the position is not affected by the magnetic force generated from the urging unit 15 or the motor. For example, the position where the magnetic sensor is disposed includes the output shaft 13 and the end of the drive shaft extending rearward of the drive source.

  In addition, a description will be given of a case in which a magnetostrictive torque sensor is used as the detection unit 16 to automatically switch a reduction ratio according to a load change from a detected change in magnetic characteristics. In addition, the same code | symbol is provided to the structure same as each above-mentioned example, and description is abbreviate | omitted.

  As shown in FIG. 6, the magnetostrictive torque sensor includes a magnetic sensing part 31 attached to the output shaft 13 and a non-contact coil that applies a magnetic force to the magnetic sensing part 31 and detects a magnetic force transmitted through the magnetic sensing part 31. 32.

  Specifically, the magnetosensitive part 31 is an amorphous alloy thin film wound around the outer peripheral surface of the output shaft 13, and the strain permeability changes due to load fluctuations. The non-contact coil 32 is fixed to the clutch case 34 of the rotary electric tool via the magnetic yoke 33, and is disposed in a non-contact manner on the outer peripheral side of the magnetic sensing unit 31. For this reason, when the magnetic permeability of the magnetic sensing part 31 changes due to load fluctuations, the voltage of the non-contact coil 32 changes. That is, the detection unit 16 detects a load fluctuation from a change in the voltage of the non-contact coil 32, and the control unit determines a shift timing when the voltage output from the non-contact coil 32 reaches a set value that is a threshold value. The electromagnetic drive of the urging unit 15 is started.

  As described above, by using the magnetostrictive torque sensor for the detection unit 16, it is possible to eliminate the need for the friction operation member for detecting the load fluctuation, and it is possible to detect the load fluctuation as an electric signal and further improve the detection accuracy of the load fluctuation. Thus, a shift in shift timing can be suppressed. And since it is not necessary to provide the detection part 16 in a deceleration mechanism, the assembly property of a deceleration mechanism can be improved.

  In addition, a description will be given of a case where a current detection circuit that detects a current value of a motor that is a driving source is used as the detection unit 16 to automatically switch a reduction ratio according to a load change from a change in the motor current value. In addition, the same code | symbol is provided to the structure same as each above-mentioned example, and description is abbreviate | omitted.

  The current detection circuit detects a current value of a motor that is a drive source that increases with an increase in load, and the control unit attaches that it is a shift timing when the current value reaches or exceeds a set value that is a threshold value. The electromagnetic drive of the urging portion 15 is started.

  As described above, by using the current detection circuit for the detection unit 16, it is possible to improve the load fluctuation detection accuracy only by adding the current detection circuit to the control unit, and to easily suppress the shift timing shift. . And since it is not necessary to provide the detection part 16 in a deceleration mechanism, and a friction operation member and a sensor member become unnecessary, while being able to improve the assembly property of a reduction mechanism, the detection part 16 can be made into a simple structure and low cost. Can be

  In addition, the automatic transmission device may include a changing unit that changes a threshold value such as a set value and a set rotation speed, and a setting operation unit that externally operates the changing unit, so that the shift timing by the control unit can be changed. Specifically, by operating the setting operation unit externally, the threshold value that the control unit determines that the changing unit is at the change timing can be changed, and the shift timing by the control unit can be changed. It has become.

  For this reason, gear shifting timing can be set for each work using the rotary electric tool, and the reduction ratio can be automatically switched at the gear shifting timing set according to each work content, further improving the usability of the rotary electric tool. can do.

DESCRIPTION OF SYMBOLS 1 Gear case 13 Output shaft 14 Switching gear 15 Energizing part 16 Detection part 23 Displacement sensor 24 Cam ring 25 Holding part 30 Rotation sensor A Axial direction

Claims (7)

  An automatic transmission provided in a reduction mechanism having a planetary reduction stage for reducing rotational drive from a drive source, wherein at least one gear of the planetary reduction stage is a switching gear for changing a reduction ratio of the reduction mechanism. A switching unit that switches the switching gear to a different speed reduction ratio by moving the switching gear in the axial direction in response to a load change, and the switching unit attracts the magnetic force by electromagnetic drive to move the switching gear. An urging unit that urges only in the axial direction, a detection unit that detects load fluctuations, and a control unit that controls energization of the urging unit, and the control unit detects a detection result of the detection unit. When the threshold value is reached, the urging unit is electromagnetically driven, and the electromagnetically driven urging unit moves the switching gear in the axial direction in parallel and holds the switching gear in the position after the axial movement. Times characterized by being Automatic transmission of the electric power tool.   2. The automatic transmission for a rotary electric tool according to claim 1, wherein the detection unit is a displacement sensor.   The automatic transmission for a rotary electric tool according to claim 1, wherein the detection unit is a rotation sensor.   The automatic transmission for a rotary electric tool according to claim 1, wherein the detection unit is a magnetostrictive torque sensor.   The automatic transmission for a rotary electric tool according to claim 1, wherein the detection unit is a current detection circuit.   6. The automatic transmission for a rotary electric tool according to claim 1, wherein the urging portion is a ring-shaped electromagnet concentric with the switching gear.   The automatic transmission for a rotary electric tool according to any one of claims 1 to 6, further comprising a changing unit that changes the threshold value.

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