JP2000254870A - Automatic transmission of rotary power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly shift by determining a spring position so that a reversal spring is reversed and the axial energization force is generated. SOLUTION: A reversal spring 61 reverses to change the energization direction before a moving second internal gear 23 reaches a neutral point in an initial engagement state during the initial engagement of a moving stroke. The relationship between the second internal gear 23 and the stoke of the reversal spring 61 satisfies initial engagement > backward energization. When the second internal gear 23 reaches the neutral point, it is disengaged from a gear of a first carrier outer periphery, also not engaged with teeth on an inner periphery of a gear case 4, but engaged with a second planatary gear. As the second internal gear 23 is not restricted, no load free rotating state exists, and the rotation is stopped from an output shaft to a second carrier by the load torque at a point side. The second planatary gear is provided with only autorotation, and a no load state exists from a secondary sun gear to a first sun gear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission for automatically shifting the output shaft of a rotary power tool such as an electric screwdriver or an electric drill by the load of a tool bit.

[0002]

2. Description of the Related Art Various rotary power tools which automatically change the speed according to the load have been proposed. Representative examples of shifting gears by moving an internal gear by load torque include, for example, JP-A-63-221980 and JP-A-06-008151.

In the former, the internal gear of the last stage of the planetary gear reduction unit is moved with a predetermined load torque, and the movement of the planetary gear is automatically changed by switching the fixed state of the internal gear of the first stage.

In the latter, the internal gear of the first stage is rotated by a predetermined torque to move the cam member, and the internal gear of the next stage is moved by the movement of the cam member, thereby automatically shifting the speed. Further, the moving internal gear is urged in the axial direction by a reversing spring whose urging direction is reversed so that the cam member and the moving internal gear do not move back and forth due to load torque fluctuation near the switching point.

Hereinafter, the latter rotary power tool will be described with reference to FIGS.
This will be described with reference to FIGS.

FIG. 3 shows a gear arrangement. Basically, it has a three-stage planetary speed reduction configuration. In the first stage, the first sun gear 11, the first planetary gear 12, and the first internal gear 13 mesh with each other, and the first planetary gear 12 is supported on the first carrier 14. In the second stage, the second sun gear 21, the second planetary gear 22, and the second internal gear 23 integrated with the first carrier 14 mesh with each other, and the second planetary gear 22 is supported on the second carrier 24. ing. In the third stage, the third sun gear 31, the third planetary gear 32, and the third internal gear 33 integrated with the second carrier 24 mesh with each other, and the third planetary gear 32 is pivotally supported on the third carrier 34. ing. The third carrier 34 is locked to the output shaft 8 and transmits the rotation to the chuck 9 at the tip. The second internal gear 23 can move back and forth, and can mesh with the gear 15 provided on the outermost periphery of the first carrier 14 when moving backward. Further, the teeth 25 that can mesh with the teeth 42 on the inner periphery of the gear case 4 during forward movement are provided at the outer front end of the second internal gear 23. As shown in FIG. 5, the second internal gear 23 has a switching spring 64 connected to an external switching knob (not shown) through an outer peripheral groove 26.
Is gripped by The third internal gear 33 is locked so as not to rotate with respect to the gear case 4. Further, as shown in FIG. 6, a plurality of (two in FIG. 6) locking projections 18 are provided on the outer circumference of the first internal gear 13 in the first stage, and the spring 66 is provided in the concave groove 43 on the inner circumference of the gear case 4. Are arranged on both sides of the locking projection 18, and the first internal gear 13 is rotatable at a predetermined load torque or more set by the load of the spring 66. As shown in FIG. 7, a cam 17 having an inclined surface is formed at the outer peripheral front end of the first internal gear 13. The second internal gear 23 faces through an interlocking ring 51 forming a cam groove 52 engaged with the cam 17. As shown in FIG. 5, the interlocking ring 51 is supported at one end by a reversing spring 61 rotatably fixed to the gear case 4. The support of the reversing spring 61 to the interlocking ring 51 is also rotatable. A projection 52 is provided on the outer circumference of the interlocking ring 51 and is inserted into the groove 44 on the inner circumference of the gear case 4 so that it can move only in the axial direction without rotating.

When the switching knob (not shown) is set to the high speed side, the gear arrangement is as shown in FIGS. 3 (a) and 7 (a). That is, the second internal gear 23 moves backward and meshes with the gear 15 on the outer periphery of the first carrier 14 and the second planetary gear 22. When the SW of the tool body (not shown) is turned on in this state, the first carrier 14, the second internal gear 23, the second planetary gear 22, and the second carrier 24 rotate integrally. The two-stage deceleration is performed only by the planetary deceleration, and the output shaft 8 is in a low torque, high speed rotation state. In this state, a load is applied to a tip tool (not shown) of the chuck portion 9, and when a predetermined load torque is reached, a spring 66 on the outer periphery of the first internal gear 13 is turned on.
The one-way rotating side is compressed and rotates in the opposite direction to the first sun gear 11. Then, the interlocking ring 51 meshing with the cam surface 17 on the outer periphery of the first internal gear 13 is pushed out and moved axially forward against the reversing spring 61 by the inclined surface of the cam, and moves as shown in FIG. 7) and FIG. 3 (b), and then moves to the state of FIG. 7 (c) and FIG. 3 (c). FIGS. 7B and 3B show a state where the second internal gear 23 has reached the neutral point of the movement stroke. FIGS. 7C and 3C show a state in which the second internal gear 23 is in the final meshing state after passing the neutral point of the movement stroke. At this time, the teeth 25 on the outer periphery of the second internal gear 23 mesh with the teeth 42 on the inner periphery of the gear case 4, and the rotation is stopped. Since the second and third planetary gears 22 are engaged with each other, the first, second, and third stages of the planetary mechanism function as deceleration, and accordingly, the output shaft 8 enters a high-torque low-speed rotation state by three-stage deceleration. . As the axial moving force of the second internal gear 23, not only the pushing force by the cam surface 17 but also
As shown in FIG. 7, the reversing spring 61 reverses at the position shown in FIG. 7B and urges forward in the axial direction, so that the second internal gear 23 moves back and forth due to load torque fluctuation near the switching point. Disappears.

Conversely, when the second internal gear 23 is returned from the low-speed rotation state to the high-speed rotation state, the set lever (not shown) is operated in conjunction with the OFF (return) of the SW of the tool body (not shown).
It works backward against the forward biasing force of the reversing spring 61, and moves the second internal gear 23 backward to return.

[0009]

Since the second reversing spring 61 urges the moving second internal gear 23 in the axial direction, the second internal gear 23 does not move back and forth due to load torque fluctuation near the switching point. However, actually, the second internal gear 23 moves in the “initial meshing state → neutral point → end meshing state”. At the neutral point, the gear 15 on the outer periphery of the first carrier 14 and the teeth 42 on the inner periphery of the gear case 4 do not mesh with each other, so that a free rotation state is achieved without restriction. If the initial and final meshing states occur simultaneously, the rotation lock state is established, so a neutral point is required. At this neutral point, since the second internal gear 23 is not restrained, when a load torque is applied to the output shaft 8, the second internal gear 2
The second planetary gear 22 meshing with the third and second internal gears 23 is in a no-load free rotation state (the second planetary gear 22 only rotates), and the rotation from the output shaft 8 to the second carrier 24 is stopped. Then, the second sun gear 21 meshing with the second planetary gear 22 also enters the no-load free rotation state. That is, the first sun gear 1 from the first carrier 14 which is integral with the second sun gear 21
Until 1 is in the no-load free rotation state. Accordingly, since the first internal gear 13 during this period is also unloaded, the rotation of the first internal gear 13 is eliminated, and the axial pushing force by the cam surface 17 is eliminated. Furthermore, since the reversing spring is also at the neutral position 61, it works so as to urge the interlocking ring 51 in the direction perpendicular to the axis, and the axial urging force is eliminated.

As described above, in the example disclosed in the latter publication,
Actually, at the neutral point, there is no axial biasing force by the interlocking ring 51 and the reversing spring 61 forming the cam member, so that there is a problem that the switching is not smooth.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, to smoothly change gears, and to improve operability.

[0012]

The above object is achieved by setting the spring position such that the reversing spring is reversed before the moving second internal gear reaches the neutral point to generate an axial biasing force. You.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIGS.
This will be described with reference to FIG. The basic configuration and operation are almost the same as described above, and the description is omitted.

As shown in FIG. 1, the moving second internal gear 23
Is the initial meshing state during the movement stroke OA (high-speed rotation)
, That is, before the neutral point is reached, the reversing spring 61 is reversed to change the biasing direction. Second internal gear 23
The relationship between the stroke of the reversing spring 61 (the supporting portion of the interlocking ring 51) is OA> ON. FIG. 2 is an external view showing a positional relationship between the reversing spring 61, the second internal gear 23, and the interlocking ring 51 when the neutral point is reached (movement stroke s ₁ ). Stroke s ₁ times, reversing spring 61 is urged forward. As shown in FIG. 3B, when the second internal gear 23 reaches the neutral point, the gear 15 on the outer periphery of the first carrier 14 and the second internal gear 2
3 and the teeth 42 on the inner periphery of the gear case 4
With the second planetary gear 22 only.

Therefore, since there is no constraint on the second internal gear 23, a no-load free rotation state is established, and the rotation from the output shaft 8 to the second carrier 24 is stopped by the load torque on the tip side. The second planetary gear 22 performs only rotation. Second sun gear 2
No load is applied from 1 to the first sun gear 11. First
The internal gear 13 is also in a no-load state, the rotation due to the load torque is eliminated, and the axial pushing force from the cam surface 17 is eliminated. However, since the reversing spring 61 has already been inverted, the interlocking ring 51, the second internal gear 23 Is moved by urging the actuator forward in the axial direction. Beyond the neutral point, as shown in FIG.
When the teeth 25 on the outer periphery of the second internal gear 23 mesh with the teeth 42 on the inner periphery of the gear case 4, an axial pushing force of the cam surface 17 due to the load torque of the first internal gear 13 is also applied, and the cam surface 17 moves to the stroke end point.

FIG. 4 shows a modification. Gear case 4
The interlocking ring 51 may be biased by a tension spring 71 having one end rotatably fixed thereto and a swing arm 72.

[0017]

As described above, according to the present invention, since the reversing position of the reversing spring is set before the second internal gear reaches the neutral point of the movement stroke, the reversing position of the second internal gear at the neutral point is set. The movement is smooth, the switching is smooth, and the operability can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a state of movement of a second internal gear and a reversing spring according to one embodiment of the present invention.

FIG. 2 is an external view showing a positional relationship between a second internal gear in FIG. 1 and a reversing spring when the second internal gear reaches a neutral point.

FIG. 3 is a longitudinal sectional view of a gear array portion showing an embodiment according to the present invention and the prior art.

FIG. 4 is a side view of a main part according to a modification of the present invention.

FIG. 5 is a side view of a main part according to the prior art.

FIG. 6 is a cross-sectional view of a first-stage speed reduction unit in FIG. 5;

FIG. 7 is a side view showing movements of a related art interlocking ring and a reversing spring.

[Explanation of symbols]

13 is a first internal gear, 17 is a cam surface, 23 is a second internal gear,
51 is an interlocking ring, 52 is a cam groove, 61 is a reversing spring, 6
6 is a spring.

Claims (1)

[Claims] 1. A multi-stage planetary gear device for changing a reduction ratio by moving at least one internal gear in the axial direction, a cam member for moving the internal gear in the axial direction, and a cam meshing with the cam member. Another internal gear that is provided on the outer peripheral surface and can rotate by a predetermined amount at a predetermined load torque or more in the gear case, an elastic body that allows the predetermined rotation of the internal gear, the cam member, and the moving internal gear, And a reversing spring for reversing the biasing direction, wherein the biasing direction of the reversing spring is reversed while the moving internal gear is in the initial meshing state. An automatic transmission for a rotary power tool.