JP2011042012A - Automatic transmission device for rotary power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic transmission device for a rotary power tool for changing over a speed reduction ratio while preventing the axial runout of a change-over gear and inhibiting the occurrence of noises during change-over. <P>SOLUTION: The automatic transmission device for the rotary power tool includes a change-over member for axially moving the change-over gear 12 of a reduction mechanism to change over a speed reduction ratio. The change-over member includes a link part axially moved in parallel with the change-over gear 12, and having a protruded portion 17 on the outer periphery, an urging part 16 urging the link part only in an axial direction A, and a holding part 18 holding the link part against the urging of the urging part 16, and having a groove through which the protruded portion 17 is inserted. With the holding of the holding part 18 canceled depending on a load variation, the change-over gear 12 is axially moved in parallel only with the urging of the urging part 16 to perform change-over. Thus, power can be imparted only in the axial direction A during change-over to prevent the axial runout of the change-over gear 12, and the need for a cam device is eliminated to reduce noises during change-over. <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. 03084138

  However, since the reversing spring is provided on the outer peripheral surface of the internal gear for shifting in Patent Document 1, the urging force of the reversing spring is applied obliquely with respect to the shaft, causing the shaft displacement of the internal gear for shifting, and the gear. It may cause problems in the planetary mechanism such as breakage.

  Since the cam gear is used to convert the rotational force into the axial movement force and the switching gear is moved in the axial direction, the noise caused by the friction generated by the operation of the cam device is large, and the product life is shortened due to wear. There's a problem.

  Accordingly, the present invention has been invented in view of the above circumstances, and eliminates the cam device and moves the switching gear in the axial direction in parallel at the time of switching, thereby suppressing noise generation and switching the reduction ratio. An object of the present invention is to provide an automatic transmission that prevents a shaft misalignment at the time and performs smooth and stable switching.

  In order to solve the above problems, the automatic transmission according to the present invention is provided in a speed reduction mechanism including a planetary speed reduction stage that decelerates rotational driving from a drive source. At least one gear of the planetary reduction stage is a switching gear 12 for changing the reduction ratio of the reduction mechanism, and the switching for changing the reduction ratio by moving the switching gear 12 in the axial direction in response to a load change. Department. The switching unit includes an interlocking unit that moves axially in parallel with the switching gear 12, an urging unit 16 that urges the linking unit only in the axial direction A, and an urging force against the urging unit 16. And a holding portion 18 for holding the interlocking portion. The interlocking portion has a protrusion 17 protruding toward the outer periphery, and the holding portion 18 has a groove through which the protrusion 17 can be inserted. Then, the protrusion 17 is inserted into the groove in response to the load fluctuation to release the holding by the holding portion 18, and the interlocking portion is axially parallel with the switching gear 12 by the biasing by the biasing portion 16. It is characterized by moving.

  By adopting such a configuration, by switching the reduction ratio in response to a load change, the switching operation by the user becomes unnecessary, and the reduction ratio can be changed without interrupting the rotation drive. The holding unit 18 is engaged / disengaged according to the load variation and moves in the axial direction only by the urging force of the urging unit 16, and the cam member that converts the rotational force into the axial direction moving force according to the load variation is provided. Can be abolished.

  The invention according to claim 2 is characterized in that, in addition to the feature of the invention according to claim 1, the holding portion 18 is a separate member from the gear case 1.

  In addition to the features of the invention according to claim 1 or 2, the invention according to claim 3 is a ring shape in which the interlocking portion has a protrusion 17 on the outer peripheral surface, and the inner periphery of the ring It is characterized in that a switching gear 12 is arranged.

  Further, the invention according to claim 4 is characterized in that, in addition to the features of the invention according to any one of claims 1 to 3, the urging portion 16 is equidistantly arranged on a circumference concentric with the switching gear 12. It is characterized by comprising a plurality of arranged elastic bodies.

  The invention according to claim 5 is characterized in that, in addition to the features of the invention according to any one of claims 1 to 3, the urging portion 16 is composed of a permanent magnet 25.

  In addition to the feature of the invention described in claim 5, the invention according to claim 6 includes a plurality of permanent magnets 25 arranged at equal intervals on a circumference concentric with the switching gear 12. It is characterized by.

  As described above, the automatic transmission of the present invention switches the reduction ratio in response to load fluctuations, thereby eliminating the need for a switching operation by the user, reducing the burden on the user, and improving usability. It is a rotating power tool. By providing the holding portion and the urging portion, the cam member becomes unnecessary, noise due to friction during operation of the cam member can be eliminated, and generation of noise during switching can be suppressed. And since there is no cam member, generation | occurrence | production of the abrasion by a cam operation | movement and component deformation | transformation can be prevented, and a product life can be improved. Furthermore, since the urging portion that is the power source during the axial movement is urged only along the axial direction, the switching gear can be moved in the axial direction in parallel, and the switching gear shaft can be shaken during switching. This makes it possible to prevent the switching of the reduction ratio in a stable and smooth manner.

  Also, by making the holding part a separate member from the gear case, the shape accuracy of the groove at the time of manufacture can be improved, the protrusion can be inserted more smoothly, and the reduction ratio switching can be made smoother and more stable. can do.

  In addition, since the urging section is made of a plurality of elastic bodies, the degree of freedom in design can be increased, noise can be further reduced, and the urging can be easily performed only along the axial direction. The switching of the reduction ratio can be made smoother and more stable.

  In addition, by using magnetic force as the urging force of the urging unit, it is possible to eliminate the restriction in the rotation direction of the urging unit, increase the degree of design freedom, further reduce noise, and change the reduction ratio. Can be made smooth and stable. In particular, by arranging the magnetic forces at equal intervals, the degree of freedom in design can be increased, and the reduction ratio can be switched more easily and stably.

It is sectional drawing of the deceleration mechanism of the Example 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 provided in the deceleration mechanism same as the above. It is explanatory drawing of operation | movement of the 1st-stage internal gear with respect to a load fluctuation same as the above, (a) is before switching, (b) is in the middle of switching. It is a perspective view of the principal part of the example which biased the interlocking ring with the some elastic body. It is a perspective view of the principal part of the example which energized the interlocking ring with magnetic force. It is a perspective view of the example which united the internal gear and interlocking ring of the 1st step.

  Embodiments of the present invention will be described below with reference to the drawings. For convenience of description, unless otherwise specified, each shape is a shape viewed along the axial direction A, 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 of the present invention is provided in a speed reduction mechanism that decelerates and outputs rotational drive from a drive source of a rotary electric tool, and the speed reduction mechanism is provided in a plurality of stages in a substantially cylindrical gear case 1 that is an exterior. Planetary stages are arranged along the central axis of the cylinder. The speed reduction mechanism includes, for example, three planetary stages as shown in FIGS. 1 to 3, and the second planetary stage is a shift stage in which the reduction ratio can be changed by the automatic transmission.

  Specifically, the first planetary stage uses the gear attached to the drive shaft of the drive source as a sun gear, the internal gear 3, the planetary gear 27, and the carrier 2 holding the planetary gear 27 via a connecting pin, It is made up of. The planetary gear 27 is engaged with the sun gear and the internal gear 3, and the sun gear, the internal gear 3, and the planetary gear 27 are located on the same plane as viewed in the axial direction A. Further, a second-stage sun gear 4 that is concentric and the next stage is attached to the first-stage carrier 2.

  The second planetary stage is a shift stage that takes two states, a state in which the internal gear 5 can rotate and a state in which the internal gear 5 cannot rotate. The ratio is large. As in the first planetary stage, the planetary gear 28 is always meshed with the sun gear 4 and the internal gear 5, and the planetary gear 28 is held by the carrier 6 via a connecting pin. Furthermore, a third-stage sun gear 7 is attached to the second-stage carrier 6 so as to be concentric with the carrier 6.

  The final planetary stage, which is the third stage, is a reduction stage in which the internal gear 29 cannot be rotated and is held in the gear case 1. The planetary gear 30 is meshed with the sun gear 7 and the internal gear 29, and the planetary gear 30 is held by the carrier 8 via the connecting pin, almost like the first and second planetary stages. An output shaft 9 is attached to the third-stage carrier 8. Further, a thrust plate 10 is disposed between the second planetary gear stage and the third planetary gear stage to prevent gears and carriers from coming off and shaft runout due to an impact when the reduction ratio is switched. The case 1 is fixed to the inner peripheral surface.

  That is, the internal gear 5 of the second planetary stage is a switching gear for changing the reduction ratio of the reduction mechanism, and is rotated from a rotatable state by being axially moved in parallel by the automatic transmission of the present invention. It switches to an impossible state.

  Specifically, the state in which the second-stage internal gear 5 is rotatable means that the second-stage internal gear 5 is engaged with the rear engagement portion 22 provided on the outer periphery of the first-stage carrier 2 and rotates integrally with the carrier 2. . Therefore, the second planetary stage transmits the rotational drive from the first planetary stage to the third stage without decelerating. The non-rotatable state, which is the other state, is disengaged from the rear engagement portion 22 and engaged with the front engagement portion 23 provided on the rear surface of the thrust plate 10 to be fixed to the gear case 1. Thus, the rotation is restricted. Therefore, the second planetary stage decelerates the rotational drive from the first planetary stage and then transmits it to the third planetary stage.

  That is, the switching gear 12 is engaged with the rear engaging portion 22 and rotated integrally with the first-stage carrier 2, and the switching gear 12 is detached from the rear engaging portion 22 and engaged with the front engaging portion 23 to engage with the gear case. The front position fixed to 1 is switched by the axial movement of the automatic transmission. Since the speed reduction ratio when the switching gear 12 is at the front position is larger than the speed reduction ratio when the switching gear 12 is at the rear position, the low torque high speed rotation mode is at the rear position and the high torque is at the front position. It is a low-speed rotation mode.

  Further, the internal gear 3 of the first stage has protrusions 13 on the outer periphery, and setting springs 14 that are elastic bodies for torque setting are disposed along the circumference at both ends of the protrusion 13 in the circumferential direction. The front surface of the internal gear 3 is provided with two interlocking engagement portions 15 arranged concentrically at equal intervals, and the interlocking engagement portion 15 is associated with a switching portion of an automatic transmission described later. Match. Therefore, when the torque applied to the internal gear 3 at the first stage reaches a value that resists the biasing of the setting spring 14, the internal gear 3 is allowed to rotate, and the rotation according to the load fluctuation is associated with the interlocking engagement. By being transmitted to the switching unit via the joint unit 15, the automatic reduction ratio switching is started. That is, the rotation of the internal gear 3 at the first stage is the starting point for starting the switching of the reduction ratio of the automatic transmission.

  The automatic transmission has a switching section for moving the switching gear 12 in the axial direction from the rear position to the front position. The switching unit includes an interlocking ring 11 that is detachable from the interlocking engagement unit 15 and rotates according to a load change, an urging unit 16 that urges the interlocking ring 11 that is power of the switching unit forward, And a holding part 18 that holds the interlocking ring 11 against the urging force of the urging part 16.

  The interlocking ring 11 has a substantially ring shape, and is provided with a releasable engaged portion on the interlocking engaging portion 15 of the first-stage internal gear 3 on the rear surface. It rotates with the internal gear 3. The interlocking ring 11 has a recess 21 on the inner peripheral side, and the switching gear 12 is rotatably disposed in the recess 21. That is, the interlocking ring 11 holds the switching gear 12 along the radial direction and the axial direction A by the recess 21, and moves in the axial direction with the switching gear 12. The interlocking engagement portion 15 has a length along the axial direction A, and is not separable, but the interlocking ring 11 is slidable along the axial direction A with respect to the interlocking engagement portion 15, and is switched. Sometimes it may also serve as a guide part for guiding the axial movement of the interlocking ring 11.

  A plurality of protrusions 17 are provided on the outer circumferential surface of the interlocking ring 11 at equal intervals on the circumference, and the front surface of the protrusion 17 is at a rear position where the interlocking ring 11 and the interlocking engagement part 15 are engaged. Is in contact with the rear surface of the holding portion 18. Therefore, the interlocking ring 11 is held in the rear position by the axial movement being restricted by the holding portion 18.

  The holding portion 18 has a substantially ring shape that is concentric with the interlocking ring 11 and has an inner diameter that is substantially the same as the outer diameter of the interlocking ring 11. And a plurality of insertion grooves 20 opened on the shaft core side. Each insertion groove 20 corresponds to and substantially corresponds to the protrusion 17 when viewed in the axial direction A, and each protrusion 17 is substantially simultaneously with any one of the insertion grooves 20 when the interlocking ring 11 is rotated. They are arranged so as to overlap along the axial direction A.

  That is, in the state where the internal gear 3 of the first stage is not rotating in the low torque high speed rotation mode, the insertion groove 20 is at a position shifted by a predetermined angle along the rotation direction with respect to the protrusion 17, and the biasing portion 16. The interlocking ring 11 is held at the rear position against the forward urging caused by. When the load reaches a predetermined value and the internal gear 3 rotates, the protrusion 17 and the insertion groove 20 overlap along the axial direction A, and the holding part 18 releases the holding of the interlocking ring 11. Further, since the holding by the holding portion 18 is released, the interlocking ring 11 is moved in the axial direction in parallel to the front side by the biasing of the biasing portion 16.

  Further, the urging portion 16 urges the interlocking ring 11 forward along the axial direction A, and moves the interlocking ring 11 in the axial direction without changing the parallelism that is the inclination with respect to the axis of the rotating surface. Is. The urging portion 16 is made of an elastic body, and is, for example, a tension spring having a larger diameter than the switching gear 12 and wound substantially concentrically with the interlocking ring 11. One end of the tension spring is fixed to the front surface of the interlocking ring 11. The other end is fixed to the rear surface of the thrust plate 10. Since the urging portion 16 is urged to the front side even after switching to the front position, the holding portion 18 on the front position side that prevents the interlocking ring 11 from returning to the rear position due to vibration during rotation driving. Also serves.

  The automatic switching operation from the low torque high speed rotation mode to the high torque low speed rotation mode of the speed reduction mechanism by the automatic transmission of the present invention will be described below.

  Since the automatic transmission is in the low-torque high-speed rotation mode in the initial state, the switching gear 12 is in the rear position and rotates integrally with the first-stage carrier 2, and the interlocking ring 11 is biased by the holding portion 18 and the biasing portion 16. The position is held against the bias. Then, the load increases while the rotary electric tool is used, and the interlocking ring 11 rotates as the first-stage internal gear 3 rotates. When the protrusion 17 and the insertion groove 20 correspond to each other along the axial direction A due to the rotation of the interlocking ring 11, the interlocking ring 11 is released from the holding part 18, and the urging force of the urging part 16 is used as power to move forward from the rear position. Move axially to position. At this time, since the urging portion 16 urges the interlocking ring 11 forward only along the axial direction A, the interlocking ring 11 moves in the axial direction in parallel while maintaining parallelism.

  When switched to the front position, the front surface of the switching gear 12 engages with the front engaging portion 23 and is fixedly held in the gear case 1 so as not to rotate, and the reduction ratio of the second planetary stage increases. Then, the automatic switching of the deceleration mechanism is completed. At this time, the interlocking ring 11 is also engaged with the front engagement portion 23, is not rotatable, and is maintained in a state where the protrusion 17 and the insertion groove 20 are aligned along the axial direction A. The through-hole 19 can be inserted without rotating the interlocking ring 11 when the transmission is reset to the initial state.

  As described above, when the predetermined torque is reached in the low torque high speed rotation mode, the interlocking ring 11 rotates, the protrusion 17 overlaps the insertion groove 20 in the axial direction A, releases the holding portion 18, and the biasing portion 16 is attached. The switching gear 12 is moved in the axial direction in parallel by using only the motive power as the power to switch to the high torque low speed rotation mode. That is, the interlocking ring 11 rotates in response to the load fluctuation to release the holding of the holding unit 18 so that the reduction ratio can be switched, and only the urging force of the urging unit 16 is used as the power to drive the switching gear 12. It is intended to move the direction.

  This eliminates the need for a switching operation by the user, reduces the burden on the user, and improves the usability of the rotary electric tool. Further, it is not necessary to provide a cam mechanism for converting the rotation according to the load fluctuation into the axial movement force, and the force applied to the switching gear 12 at the time of switching is only along the axial direction A from the urging portion 16. It becomes an energizing force.

  Further, since only the urging portion 16 applies an axial movement force to the switching gear 12, the switching gear 12 can be moved in the axial direction in parallel, and the switching gear 12 can be shaken at the time of switching. It is possible to prevent the switching of the reduction ratio smoothly and stably. Since the cam mechanism and the like are not required, noise due to friction between the cam members during operation of the cam mechanism is eliminated, generation of noise during switching can be suppressed, wear due to cam operation, and part deformation The product life can be improved.

  In addition, the holding portion 18 is generated separately from the gear case 1 at the time of manufacture, so that the shape of the groove can be accurately formed, the dimensional accuracy of the groove is improved, and the plurality of protrusions 17 are substantially simultaneously formed with any one of the grooves. When they overlap in the axial direction A, they can be more accurately matched, and switching can be performed smoothly and stably.

  In addition, the code | symbol 24 of the interlocking | linkage ring 11 is the groove part for operation formed in the ring shape along the outer peripheral surface. The operation groove 24 is provided with a reset lever (not shown) made of a leaf spring or the like. For example, the reset lever returns the interlocking ring 11 and the switching gear 12 to the rear position when driving such as the release of the external operation of the trigger lever is stopped, and resets the automatic transmission to the initial state during non-rotational driving. Is.

  Further, the axial movement of the switching gear 12 is not limited to the movement from the rear to the front, but may be a movement from the front to the rear according to the configuration of the switching gear 12. It may be smaller than the reduction ratio before switching. Of course, the interlocking ring 11 may be provided with three or five or more protrusions 17 instead of four, or may have more insertion grooves 20 than the protrusions 17.

  The configuration for detecting the load fluctuation is not limited to the configuration using the setting spring 14, but may be a configuration using a change in the current value of the drive source. Further, the front engaging portion 23 is of a design change as long as it has a shape and arrangement that does not hinder the biasing portion 16 such as expansion and contraction of the elastic body. The engaged portion to be engaged may be provided only in the switching gear 12, and the interlocking ring 11 may be rotatable at the front position.

  Also, as shown in FIG. 4, a plurality of tension springs having a small diameter and substantially the same shape as the biasing portion 16 are arranged on the circumference concentric with the switching gear 12 at equal intervals. The resultant force may be applied only along the axial direction A. In particular, since the urging portion 16 is composed of a plurality of elastic bodies, the front engaging portion 23 can be provided in the circumferential clearance of each elastic body. Therefore, each elastic body which is the urging portion 16 can be attached not to the thrust plate 10 but to the inner wall on the output side of the gear case 1, so that the degree of freedom of design is increased and the automatic transmission of the present invention is installed in the planetary reduction stage. It can also be used for those not provided with the thrust plate 10 between them.

  The urging unit 16 urges the interlocking ring 11 and the switching gear 12 only along the axial direction A, so that the interlocking ring 11 and the switching gear 12 are axially moved without changing the parallelism when the reduction ratio is switched. Any shape and arrangement that does not hinder the engagement of the front and rear engaging portions 22 and 23 and the holding of the holding portion 18 may be used. That is, the number and shape of the elastic bodies are set appropriately.

  Of course, the urging portion 16 is not limited to a pulling portion, and may be a portion that presses forward such as a pressing spring. For example, when the recessed portion opened rearward and recessed along the axial direction A is formed in the interlocking ring 11 and the urging portion 16 made of a pressing spring is disposed in the recessed portion, the holding portion 18 is released. The interlocking ring 11 is pushed forward and switched by a pressing spring. In addition, the biasing portion 16 may be provided on the inner peripheral surface of the gear case 1 or the inner wall which is the end surface in the axial direction A, as long as it can bias the interlocking ring 11 only in the axial direction A at the time of switching. .

  Further, a part of the interlocking ring 11 is made of a magnetic material, a permanent magnet 25 is disposed on the inner wall of the thrust plate 10 or the gear case 1 on the output side, and the switching gear 12 and the interlocking ring 11 are moved forward by magnetic attraction. You may bias to the side. That is, the urging unit 16 is changed from urging by an elastic force to urging by a magnetic force.

  For example, as shown in FIG. 5, the protrusion 17 of the interlocking ring 11 is made of a magnetic material, and is located at a position overlapping the insertion groove 20 when viewed in the axial direction A and concentric with the central axis of the gear case 1. There is one in which a plurality of permanent magnets 25 arranged at equal intervals are embedded in the inner wall on the output side of the gear case 1. That is, the permanent magnets 25 are arranged at equal intervals on the circumference concentric with the holding portion 18, and the insertion grooves 20 are located on the rear side along the axial direction A of the permanent magnets 25. An urging force, which is the resultant magnetic force of the magnet 25, is applied to the interlocking ring 11 along the axial direction A only. At the time of switching, when the protrusion 17 overlaps the insertion groove 20, the magnetic force is most strongly received from the permanent magnet 25. At this time, since the holding by the holding portion 18 is released, the interlocking ring 11 is By moving in parallel in the axial direction through the through hole 19, the engagement partner of the switching gear 12 is switched from the rear engagement portion 22 to the front engagement portion 23, and the reduction ratio is switched.

  Thus, even if the urging method of the urging portion 16 is changed from an elastic force to a magnetic force, the urging force from the permanent magnet 25 to the interlocking ring 11 is applied only along the axial direction A. The switching gear 12 moves in the axial direction without changing the parallelism. Therefore, shaft shake at the time of switching is prevented and noise from the cam member or the like is prevented, thereby reducing noise at the time of switching. In particular, the urging portion 16 is restrained in the rotation direction when the interlocking portion is rotated, so that it is possible to prevent the members constituting the urging portion 16 from being loaded in the rotation direction and causing twisting. Can be improved.

  Further, it is preferable that the constituent members such as a gear group other than the urging portion 16 and the projecting portion 17 are made of a non-magnetic material that is not or hardly urged by magnetic force. When the holding portion 18 located between the urging portion 16 and the protrusion 17 is formed of a magnetic insulating material that does not transmit magnetic force, the magnetic force from the urging portion 16 is generated when the interlocking ring 11 is in the rear position. It is preferable to prevent the interlocking ring 11 from being applied.

  Specifically, in a state where the interlocking ring 11 is located at the rear position, the protrusion 17 is not pressed against the holding portion 18, and the axial movement is restricted to the rear surface of the holding portion 18. Only when the interlocking ring 11 rotates together with the first-stage internal gear 3 and the protrusion 17 overlaps the insertion groove 20 along the axial direction A, the biasing force toward the front side by the biasing portion 16 is interlocked. It is given to the ring 11. Therefore, it is possible to suppress the wear between the contact parts at the time of rearward position and switching, and the occurrence of stress concentration between the protrusion 17 and the outer periphery of the interlocking ring 11, and the life of the speed reduction mechanism can be extended.

  Further, as shown in FIG. 6, the first-stage internal gear 3 and the interlocking ring 11 may be integrally formed. At this time, the second-stage internal gear 5 that is the switching gear 12 is rotatably held by the interlocking ring 11 along the axial direction A and the radial direction. That is, the rotation at the rear position of the switching gear 12 is prevented from being transmitted to the internal gear 3 and the interlocking ring 11 in the first stage, and the shaft shake during the rotation of the switching gear 12 is prevented. Of course, the internal gear 3 of the first stage rotates not the interlocking ring 11 but the holding portion 18 according to the load fluctuation, and the front engaging portion 23 locks the switching gear 12 by magnetic force to prevent rotation. There may be.

DESCRIPTION OF SYMBOLS 1 Gear case 2 (First stage) Carrier 3 (First stage) Internal gear 5 (Second stage) Internal gear 9 Output shaft 10 Thrust plate 11 Interlocking ring 12 Switching gear 15 Interlocking engaging part 16 Energizing part 17 Protruding portion 18 Holding portion 20 Inserting groove 25 Permanent magnet

Claims (6)

  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 to a state of a different reduction ratio by moving the switching gear in the axial direction in response to a load change, and the switching unit is an interlocking unit that is restricted from rotating under a predetermined torque. A power source at the time of switching, and a biasing portion that biases the interlocking portion only in the axial direction, and a state of one reduction ratio with the interlocking portion held in position against the biasing of the biasing portion The interlocking part has a protrusion protruding toward the outer periphery, and the holding part has a groove through which the protrusion can be inserted, and has a predetermined torque. And the interlocking part rotates to keep the protrusion and groove overlapped along the axial direction. When the holding by the part is released, the urging part causes the interlocking part to move in the axial direction in parallel with the switching gear and switch to another reduction ratio state. Automatic transmission for rotary electric tools.   The automatic transmission for a rotary electric tool according to claim 1, wherein the holding portion is a separate member from the gear case.   The interlocking portion is formed in a ring shape that is concentric with the switching gear and has the protrusion on an outer peripheral surface, and the switching gear is disposed on the inner periphery of the ring. An automatic transmission for a rotary electric tool according to claim 1 or 2.   The said urging | biasing part consists of a some elastic body arrange | positioned at equal intervals on the circumference concentric with the said switching gear, The Claim 1 characterized by the above-mentioned. Automatic transmission for rotary electric tools.   The automatic transmission device for a rotary electric tool according to any one of claims 1 to 3, wherein the urging portion is made of a permanent magnet.   6. The automatic transmission for a rotary electric tool according to claim 5, wherein a plurality of the permanent magnets are arranged at equal intervals on a circumference concentric with the switching gear.

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