JP5379606B2 - Automatic transmission for rotary electric tools - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic transmission for a rotary power tool capable of safely and smoothly performing the switching of a speed reduction ratio by preventing axial deflection at the switching. <P>SOLUTION: The automatic transmission for the rotary power tool which is disposed in a speed reduction mechanism having a planetary reduction stage includes a switching section for switching the speed reduction ratio by moving a switching gear 18 provided in the planetary reduction stage in the axial direction according to a load variation, and an attraction section 24 biasing the switching gear 18 in the axial direction (A) by the attraction of a magnetic force. The attraction section 24 assists the movement of the switching gear 18 in the axial direction by the attraction of the magnetic force without changing the inclination of the rotary surface thereof and holds a position of the switching gear 18 after the movement. This allows the switching gear 18 to be magnetically attracted along the axial direction (A) so that the axial deflection of the switching gear 18 is prevented at the switching. <P>COPYRIGHT: (C)2011,JPO&amp;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 order to solve the above-described problems, an automatic transmission for a rotary electric tool according to the present invention is provided in a reduction mechanism including a planetary reduction stage that decelerates rotational drive from a drive source, and at least one of the planetary reduction stages. Two gears serve as a switching gear 18 that changes the reduction ratio of the speed reduction mechanism. As a feature of the present invention, the switching gear 18 is moved only in the axial direction A by switching the reduction gear ratio by moving the switching gear 18 in the axial direction in response to load fluctuations, and by magnetic attraction. And a suction part 24 for energizing. Further, the suction unit 24 moves the switching gear 18 in the axial direction in parallel by magnetic attraction and holds the switching gear 18 at the position after the movement . Further, the switching unit includes a cam member that moves the switching gear 18 in the axial direction toward the suction unit 24 in response to an increase in load, and between the suction unit 24 and the cam member in the axial direction. The switching gear 18 is disposed between them.

  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. And since the magnetic force attraction by the attraction portion 24 is applied only in the axial direction A, the switching gear 18 is prevented from being shaken when the switching gear 18 is moved in the axial direction, and the switching gear 18 is caused by the load fluctuation accompanying the change in the reduction ratio. Reciprocating back and forth along the axial direction A can be prevented.

  Further, it is preferable to use a permanent magnet or an electromagnet for the attraction portion 24, and in particular, the permanent magnet or the electromagnet is formed concentrically with the shaft of the switching gear 18 or a plurality of permanent magnets are formed on the shaft of the switching gear 18. It is preferable that the switching gear 18 can be reliably urged only in the axial direction A by being arranged at equal intervals on a concentric circumference. And what uses the electromagnet can change the magnetic force of the attraction | suction part 24 by changing the electric energy supplied to an electromagnet according to the electric current value of a drive source, and is preferable.

  Further, it is preferable that a buffer member 25 is disposed between the switching gear 18 and the suction portion 24 so that the buffer member 25 absorbs an impact when the switching gear 18 is switched.

  As described above, the automatic transmission of the rotary electric tool according to the present invention switches the reduction ratio in response to load fluctuations, thereby eliminating the need for a switching operation by the user and reducing the burden on the user. It has become a rotating power tool with improved usability. And by preventing the occurrence of front and rear shaking and shaft shaking of the switching gear when the reduction ratio changes due to magnetic attraction of the suction part, the switching gear teeth due to the shaking and the engaging part for changing the reduction ratio It is possible to prevent the occurrence of problems such as damage to the machine. Further, by preventing the occurrence of problems, the tool life can be improved, the switching gear can be moved smoothly, and stable reduction ratio switching can be performed without interrupting the rotation drive.

  In addition, the use of a permanent magnet or electromagnet for the suction unit eliminates the need for the switching gear that is magnetically attracted by the suction unit to generate a magnetic force, eliminating the need for adjustment of the weight balance, strength, etc. of the switching gear. The gear configuration can be made simple and simple. In particular, the shape of the permanent magnet or electromagnet or the arrangement of the plurality of permanent magnets is a concentric ring shape with the shaft of the switching gear, so that the rotation surface of the switching gear can be reliably aligned along the axial direction without changing the inclination of the rotation surface. Can be energized.

  In addition, since the buffer member is arranged between the switching gear and the suction portion, even if the axial movement of the switching gear is accelerated by magnetic force attraction and contacts the suction portion, the shock absorbing member absorbs the impact at the time of contact. can do. As a result, damage to the switching gear and the suction portion and occurrence of problems due to contact between the switching gear and the suction portion, such as shaft shift of the switching gear, can be prevented, and the reduction ratio can be switched more smoothly and stably. Can do.

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 the switching operation | movement of an automatic transmission same as the above, (a) is the high speed mode before switching, (b) is in the middle of mode switching, (c) is the low speed mode after switching.

  Embodiments of the present invention will be described below with reference to the drawings.

  The automatic transmission of the present invention is provided in a speed reduction mechanism that decelerates and outputs the rotational drive from the drive source of the rotary electric tool. The planetary reduction stage is arranged along the central axis of the cylinder.

  For example, as shown in FIGS. 1 to 3, in a reduction mechanism composed of three planetary reduction stages, the first planetary reduction stage uses a sun gear (not shown in the drawing) as the gear attached to the drive shaft of the drive source. It comprises an internal gear 5, a planetary gear 3, and a carrier 4 that holds the planetary gear 3 via a connecting pin. The planetary gear 3 is engaged with the sun gear and the internal gear 5, and the sun gear, the internal gear 5, and the planetary gear 3 are located on the same plane when viewed in the axial direction A. Further, a second-stage sun gear 6 that is concentric with the carrier 4 and is the next stage is attached to the first-stage carrier 4.

  Further, the second planetary speed reduction stage takes two states, a state where the internal gear 8 can rotate and a state where the internal gear 8 cannot rotate. The ratio is large. As in the first planetary speed reduction stage, the planetary gear 29 is always meshed with the sun gear 6 and the internal gear 8, and the planetary gear 29 is held by the carrier 7 via the connecting pin. Further, a third-stage sun gear 9 is attached to the second-stage carrier 7 so as to be concentric with the carrier 7.

  The planetary gear 30 of the final stage, which is the third stage, has the planetary gear 30 meshed with the sun gear 9 and the internal gear 31 in substantially the same manner as the first and second planetary speed reduction stages. Is held by the carrier 10 via a connecting pin, and the output shaft 11 is attached to the third-stage carrier 10.

  In other words, the second planetary gear reduction stage is a gear stage in which the reduction gear ratio can be switched by the automatic transmission of the present invention, and the switching internal gear that changes the reduction gear ratio when the second gear internal gear 8 moves in the axial direction. (Hereinafter referred to as the switching gear 18).

  Specifically, when the switching gear 18 moves in the axial direction, the switching gear 18 switches between a rear position on the drive source side and a front position on the output shaft 11 side. At the rear position, the switching gear 18 engages with the engaging portion 21 provided on the outer periphery of the first stage carrier 4 and rotates integrally with the carrier 4 so that the low torque high speed rotation mode is set. At the forward position, the switching gear 18 is disengaged from the first-stage carrier 4 and engaged with the case engaging portion 22 provided on the inner surface of the gear case 1 so that it cannot rotate and is fixedly held on the gear case 1. Thus, the high torque low speed rotation mode is set.

  An axial transmission of the switching gear 18 from the rear position to the front position is performed by an automatic transmission. The automatic transmission includes a cam member that advances the switching gear 18 in the axial direction A in response to an increase in load generated during use of the rotary electric tool, and a suction disposed on the front side of the switching gear 18. Part 24. The suction part 24 is fixed to the gear case 1 between the second stage and the third planetary reduction stage, and is located along the axial direction A at a position facing the front end face 20 of the switching gear 18. have. The permanent magnet is, for example, a substantially ring-shaped plate having an inner diameter that is substantially the same as the inner tooth diameter of the switching gear 18 and an outer diameter that is substantially the same as the outer diameter of the front end face 20 of the switching gear 18.

  The cam member includes a plurality of cam protrusions 16 provided on the front surface of the first-stage internal gear 5, a cam groove 17 having an inclination corresponding to the cam protrusion 16, and a cam ring 15 including the cam groove 17. And a slide guide for restricting the rotation of the cam ring 15. The cam ring 15 is disposed between the first-stage and second-stage internal gears 5, 8 and moves back and forth along the axial direction A by the guide of the slide guide 32.

  Specifically, a plurality of protrusions 13 are provided on the outer periphery of the first-stage internal gear 5, and the protrusions 13 slide in respective circumferential grooves 33 provided in the same number as the protrusions 13 on the inner peripheral surface of the gear case 1. The first-stage internal gear 5 is rotatable within a range in which the protrusion 13 is positioned in the circumferential groove 33. Between each of the protrusions 13 and the circumferential end portions of the circumferential groove 33 facing each other in the circumferential direction, torque setting springs 14 that expand and contract due to load fluctuations are arranged, respectively, and the first stage through the springs 14. The internal gear 5 is held by the gear case 1. That is, the rotation of the internal gear 5 at the first stage is restricted by the spring 14 when the rotational drive is transmitted, and the rotation starts when the torque applied to the internal gear 5 reaches a value that resists the bias of the spring 14. is there.

  At this time, since the rotation of the cam ring 15 is restricted by the slide guide 32, the cam groove 17 is pushed forward by the rotation of the cam protrusion 16, and the cam ring 15 moves forward. That is, the rotational force of the internal gear 5 in the first stage is converted into a force that pushes the cam ring 15 along the axial direction A via the cam protrusion 16 and the cam groove 17, and the cam ring 15 is moved forward by the rotation of the internal gear 5. It moves axially in parallel to.

  As the cam ring 15 moves in the axial direction, the internal gear 8 at the second stage is pushed along the axial direction A to move forward, and the reduction ratio is switched. At this time, the second-stage internal gear 8 pushed forward by the cam ring 15 is attracted by the permanent magnet of the suction portion 24 facing forward in the course of advancement, and disengages from the first-stage carrier 4 to move forward. Move to. After the movement to the forward position, the switching gear 18 is engaged with the case engaging portion 22 provided in the gear case 1 so as not to rotate, and is urged forward along the axial direction A by the magnetic attraction. The retreat and rotation are regulated and held at the front position.

  Further, immediately after the engagement of the carrier 4 with the engagement portion 21 is released or immediately before the release, the suction portion 24 sucks the switching gear 18 and moves it to the front position, before and after the change of the reduction ratio. This prevents the load from vibrating and becoming unstable. Of course, the switching gear 18 is formed of a magnetic material, or has a magnetic material or a permanent magnet in the front end face 20 or in the vicinity of the front end face 20, and is attracted to the magnetic force by the suction portion 24 to move to the front position. The direction is movable. In particular, since the attracting portion 24 generates a magnetic force, the switching gear 18 is formed of a magnetic material that does not spontaneously generate a magnetic force. It is preferable to suppress the occurrence of stress concentration at the time of movement and to achieve a low-cost and simple configuration.

  In this way, the automatic transmission device uses the second-stage internal gear 8 as the switching gear 18 and moves the switching gear 18 in the axial direction in response to the load variation applied to the first-stage internal gear 5. The reduction ratio is switched. During the movement, the magnetic force of the attracting part 24 is applied to the switching gear 18 to apply the magnetic force as an auxiliary force for assisting the axial movement, and the switching gear 18 is held at the forward position after the movement. ing.

  Therefore, as the load increases, the automatic transmission automatically switches from the low torque high speed mode to the high torque low speed mode without stopping the rotational drive of the rotary electric tool. Switching to is no longer necessary. And since switching operation is unnecessary and switching is possible without stopping the rotational drive, the burden on the user of the rotary electric tool is reduced and the usability is improved.

  In particular, during the switching, the auxiliary force due to the magnetic attraction by the suction part 24 is applied to the switching gear 18 only along the axial direction A, so that the reduction ratio such as engagement / disengagement of the switching gear 18 and the engaging part 21 changes. In this case, the movement along the axial direction A such as the switching gear 18 moving back and forth in the axial direction A due to the load fluctuation accompanying the change in the reduction ratio is prevented. Therefore, it is possible to prevent the occurrence of problems such as breakage of the switching gear 18 and the engaging portion 21 due to the above two types of shaking, improve the tool life, and smoothly move the switching gear 18 to the front position. Thus, stable reduction ratio switching can be performed.

  And since the attraction | suction part 24 is a substantially ring shape facing substantially the whole surface of the circular front end surface 20 of the switching gear 18, the resultant force of the magnetic force applied from the attraction part 24 to the switching gear 18 is only along the axial direction A. Thus, the switching gear 18 is reliably prevented from being inclined with respect to the axial direction A and moving in the axial direction. That is, an auxiliary force by magnetic attraction is applied while maintaining the parallelism of the switching gear 18 with respect to the axis of the front end surface 20, and the switching gear 18 can be prevented from shaking when moving in the axial direction. Safety and tool life are further improved by preventing defects such as breakage. Further, after the movement to the front position, the switching gear 18 is held at the front position by the magnetic force attraction by the suction portion 24. Therefore, even if the cam ring 15 is retracted due to a decrease in load accompanying the change to the high speed mode, the switching gear 18 Thus, it is possible to switch the reduction ratio reliably.

  Further, a buffer member 25 made of an elastic body that absorbs and relaxes an impact is attached to substantially the entire surface of the suction portion 24 on the surface of the suction portion 24 that contacts the front end surface 20 of the switching gear 18. For this reason, the front end face 20 of the switching gear 18 moved to the front position is brought into contact with the permanent magnet via the elastic body, so that the shock at the time of movement accompanied by magnetic attraction is moderated by the buffer member 25. The buffer member 25 is preferably made of an elastic body such as rubber or soft resin that is non-magnetic and does not impede the magnetic attraction of the suction portion 24 and can absorb an impact. Of course, the buffer member 25 is not limited to the one provided on the permanent magnet in a substantially ring shape, but the one provided on the switching gear 18 side, the front end face 20 of the switching gear 18 such as bellows, and the contact surface of the permanent magnet. It may be one that absorbs impact by expanding and contracting.

  The switching gear 18 is provided with a substantially ring-shaped groove 19 along the outer periphery, and the switching spring 18 interlocked with a switching handle 26 forcibly switching the position of the switching gear 18 by an external operation. 27 and a reset lever 28 that returns the switching gear 18 to the rear position in conjunction with the trigger switch 12 that performs the driving operation of the driving source. When the switching handle 26 is operated from the outside, the switching spring 27 forcibly moves the switching gear 18 to the front position in accordance with the operation and switches to the low speed mode regardless of the load fluctuation.

  The reset lever 28 exhibits a spring force that resists the magnetic force of the suction portion 24 by releasing the external operation of the trigger switch 12 in the low speed mode. That is, when the external operation of the trigger switch 12 is released after the operation in the low speed mode, the switching gear 18 at the front position is moved to the rear position, which is the initial position, by the spring force accumulated in the reset lever 28, and the automatic shift is performed. The device is returned to the initial state. Therefore, the switching gear 18 is not returned to the rear position during rotational driving such as during switching from the low speed mode or the high speed mode to the low speed mode.

  As a modification of the cam member, a cam projection 16 is provided on the thrust plate 2 located on the drive source side of the first-stage internal gear 5, and a cam corresponding to the cam projection 16 is provided on the rear end surface of the first-stage internal gear 5. A groove 17 may be provided. At this time, the internal gear 5 at the first stage also serves as the cam ring 15, the dimension of the cam ring 15 in the axial direction A can be reduced, and the speed reduction mechanism can be downsized.

  The correspondence between the reduction ratio switching and the load fluctuation is not limited to the one using an elastic body that expands and contracts due to the load fluctuation, but the load fluctuation is detected by detecting the load fluctuation from the current value of the drive source. You may make it correspond. For example, when the internal gear 5 at the first stage is prevented from rotating by a locking portion such as a hook or an electromagnetic lock and the current value of the drive source exceeds a certain value, the locking is released and the internal gear 5 rotates to rotate the cam ring 15. There is something that works. Of course, the application of the axial direction moving force to the switching gear 18 is not limited to that using a cam member, and may be applied by a magnetic force or an elastic force.

  Further, as another embodiment of the attracting portion 24, a plurality of permanent magnets are arranged in a substantially ring shape at equal intervals along the circumference, and switched to the rear end face of the permanent magnet arranged in a substantially ring shape. There is one in which the front end face 20 of the working gear 18 is opposed along the axial direction A. By arranging a plurality of permanent magnets in a substantially ring shape concentric with the switching gear 18 at equal intervals, a magnetic force is applied to each part of the front end face 20 of the switching gear 18 substantially equally, and the switching gear 18 is applied to the switching gear 18. The resultant force of magnetic attraction is only along the axial direction A.

  Therefore, the switching gear 18 can be moved in the axial direction in parallel to prevent the shaft shake during the movement, and the weight of the suction portion 24 can be reduced. In addition, the suction portion 24 is provided integrally with the case engaging portion 22, and a magnetic body or a permanent magnet is provided in the engaged portion 21 of the switching gear 18 with the case engaging portion 22 or in the vicinity of the engaged portion 21. The reduction mechanism may be downsized.

  In still another embodiment, the attraction unit 24 uses an electromagnet instead of a permanent magnet so that the on / off switching of the magnetic attraction to the switching gear 18 and the strength of the urging force can be changed. In particular, a magnetic force control unit (not shown) that controls the magnetic force intensity generated by the suction unit 24 by detecting the load variation and adjusting the power supplied to the electromagnet according to the load variation is provided in the internal circuit of the rotary electric tool. It is preferable.

  For example, the electromagnet is arranged in front of the front position in a substantially ring shape concentric with the switching gear 18 so that the rear end surface of the electromagnet and the front end surface 20 of the switching gear 18 are opposed to each other, and the magnetic force control unit has the electromagnet. There is one that controls the magnetic attraction of the attraction unit 24 by switching on and off the power supplied to the attraction.

  The magnetic force control unit detects a current value of a motor as a driving source and calculates a load amount generated in the tool from a change in the detected current value. When the load amount for starting the reduction gear ratio switching operation by the automatic transmission is reached, the magnetic force control unit supplies power to the electromagnet to generate the magnetic force in the suction unit 24, thereby attracting the magnetic force of the suction unit 24. Is applied to the switching gear 18 to move the switching gear 18 to the forward position. Furthermore, the power supply to the electromagnet by the magnetic force control unit continues until the trigger switch 12 is released, and the switching gear 18 is held at the forward position by the magnetic force.

  In other words, the suction unit 24 generates a magnetic force only during the switching operation and during the low-speed mode after the switching, and the control unit applies power to the electromagnet when the high-speed rotation mode and the trigger switch are not turned on. The power supply is stopped. Therefore, the adhesion of dust having a magnetic material such as iron powder and metal scraps to the suction part and the switching gear is suppressed, and the magnetic attraction force to the switching gear is reduced due to the adhesion of dust, the switching gear and the suction. This prevents the occurrence of problems such as wear and breakage of the contact surfaces of the parts and gear teeth, thereby improving the usability and tool life.

DESCRIPTION OF SYMBOLS 1 Gear case 5 (First stage) Internal gear 8 (Second stage) Internal gear 15 Cam ring 16 Cam protrusion 17 Cam groove 18 Switching gear 24 Suction part 25 Buffer member

Claims (7)

An automatic transmission provided in a speed reduction mechanism having 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 for changing a reduction ratio of the reduction mechanism;
A switching unit that switches the reduction ratio by moving the switching gear in the axial direction in response to load fluctuations, and a suction unit that biases the switching gear only in the axial direction by magnetic force attraction.
The suction unit holds the switching gear to the position after the movement causes parallel to axial movement of the switching gear by magnetic attraction,
The switching unit includes a cam member that moves the switching gear in the axial direction toward the suction unit according to an increase in load,
An automatic transmission for a rotary electric tool, wherein the switching gear is disposed between the suction portion and the cam member in the axial direction .   2. The automatic transmission for a rotary electric tool according to claim 1, wherein the suction part is made of a permanent magnet concentric with the shaft of the switching gear and formed in an annular shape.   2. The automatic speed change of the rotary electric tool according to claim 1, wherein the suction part is composed of a plurality of permanent magnets arranged at equal intervals on a circumference concentric with the shaft of the switching gear. apparatus.   The automatic transmission device for a rotary electric tool according to claim 1, wherein the suction portion is made of an electromagnet.   5. The automatic transmission for a rotary electric tool according to claim 4, wherein the electromagnet is concentric with the shaft of the switching gear and formed in an annular shape.   6. The automatic transmission device for a rotary electric tool according to claim 4, wherein a power supply amount for generating a magnetic force in the electromagnet is changed according to a current value of the drive source.   The rotary electric tool according to any one of claims 1 to 6, wherein a buffer member that absorbs an impact at the time of switching of the switching gear is disposed between the switching gear and the suction portion. Automatic transmission.

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