JP3084138B2 - Automatic transmission for rotary power tools - Google Patents

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 performing a shift operation in a rotary electric tool such as an electric screwdriver according to a load change.

[0002]

2. Description of the Related Art Various types of rotary electric tools capable of switching a reduction ratio in accordance with a load have been provided, but conventional transmissions perform a shift only by a switching operation of a user. Further, which reduction ratio (output characteristic) is selected by this switching operation is determined by the user.

[0003]

By the way, considering screw tightening and drilling work, work is first started at a reduced speed ratio, that is, a low torque high speed rotation, and then a high torque low speed rotation is performed by increasing the reduction ratio. This means that the work efficiency can be improved.However, in the conventional system, the reduction speed ratio must be set at the start of work, and an operation of switching to the high reduction ratio must be added during the work. This burden increases.

As disclosed in Japanese Patent Application Laid-Open No. 63-221980, there is provided a device which is automatically switched in response to a load change.
Switching was not smooth or performed reliably, and in addition, load switching near the switching point frequently resulted in frequent switching between high and low, resulting in gear damage and loud noise. .

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and it is an object of the present invention to provide an automatic transmission for a rotary electric tool which can smoothly and surely shift according to a load change. Another object of the present invention is to provide an automatic transmission that does not frequently perform a switching operation due to a load change near a switching point.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a transmission unit in which a reduction ratio is switched by axial movement of at least one internal gear in a multi-stage planetary mechanism, and a rotation unit that is rotatable with respect to a gear case. An elastic body provided between the other internal gear and the gear case and allowing rotation of the internal gear with a torque equal to or more than a predetermined torque; and an axial direction of the latter internal gear for shifting the rotation of the latter internal gear. It is characterized by including a cam member for converting the movement to a movement, and a reversing spring for biasing the speed change internal gear in the axial direction and for reversing the biasing direction halfway.

[0007]

According to the present invention, the cam member moves the internal gear for shifting by load fluctuation to perform gear shifting, and at this time, the reversing spring reverses the biasing direction halfway, so that the internal gear for shifting is changed. The switching operation of the reduction ratio accompanying the axial movement is made smooth and reliable.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to an embodiment shown in the drawings. As shown in FIG. 8, this rotary electric tool comprises a motor 8 which rotates with a power supplied from a detachable battery pack.
2 is driven by the speed reduction mechanism in the gear case 7 to drive the drive shaft 9 provided with the chuck 90. As shown in FIG.
It contains a three-stage planetary mechanism.

The first stage planetary mechanism uses a gear attached to the output shaft of the motor 8 as a sun gear, and comprises an internal gear 12, a planetary gear 13, and a carrier 14 holding the planetary gear 13. The second-stage planetary mechanism includes a sun gear 21 and an internal gear 22, a planetary gear 23, and a carrier 24 provided integrally with the carrier 14. The third-stage planetary mechanism further includes a sun gear provided integrally with the carrier 24. It comprises a gear 31, an internal gear 32, a planetary gear 33, and a carrier 34. The output of the carrier 34 is output from an interlocking pin 35 protruding from the carrier 34, a lock plate 92 disposed on the outer periphery of the drive shaft 9, and a lock member located between the lock plate 92 and the interlocking pin 32. (Not shown) to the drive shaft 9. These members, together with the lock ring 93,
It has a function of automatically fixing the drive shaft 9 to the gear case 7 when the motor 9 is stopped, but the description is omitted here. Further, the internal gear 32 in the third stage planetary mechanism is always in a non-rotatable state. When the tightening torque exceeds a set torque, the internal gear 32 starts rotating and cuts off the transmission of power to the drive shaft 9 to limit the tightening torque. Although it is also a member of the torque limiter, description of this point is also omitted.

The internal gear 22 in the second-stage planetary mechanism is provided so as to be rotatable around the axis and movable in the axial direction, and is provided at the rear end in the axial direction. In the first-stage planetary mechanism, an engagement portion with the carrier 14 is provided.
When the internal gear 22 is engaged with the carrier 14 as shown in FIG. 2, the carrier 14 and the second stage planetary gear in the first stage planetary mechanism are provided. The drive shaft 9 is driven at low torque and high speed to directly connect with the carrier 24 in the mechanism. When the internal gear 22 advances and engages with the gear case 7 as shown in FIG. Since the stage planetary mechanism is also decelerated, the drive shaft 9 is driven at high torque and low speed. The switching of the reduction ratio is not limited to this example. As shown in FIG. 1, an annular groove 25 is formed on the outer peripheral surface of the internal gear 22, and an end of the switching spring 51 held on the outer surface of the gear case 7 is engaged with the annular groove 25. . This switching spring 5
1 transmits the sliding operation of the height changing handle 5 to the internal gear 22.

On the other hand, the internal gear 12 of the first stage planetary gear has a plurality of cam projections 15 on the surface on the side of the internal gear 22, and a plurality of projections 16 on the outer peripheral surface. . As shown in FIG. 5, these projections 16 are located in grooves 70 formed on the inner surface of the gear case 7 to limit the rotatable range of the internal gear 12 around the axis. In the groove 70, switching torque setting springs 71, 71 are arranged so as to be located on both sides of the projection 16. One spring 71 is for forward rotation, and the other spring 71 is for reverse rotation.

The interlocking ring 6 is provided between the internal gear 12 and the internal gear 22. This interlocking ring 6 has a plurality of cam recesses 60 corresponding to the cam projections 15 of the internal gear 12, and the projections 61 protruding from the outer peripheral surface are formed in the axial direction of the inner surface of the gear case 7 shown in FIG. By engaging with the groove 72, it is non-rotatable and movable in the axial direction. A reversing spring 65 and a reset lever 67 are provided on the outer peripheral surface of the interlocking ring 6.
And are connected.

The reversing spring 65 is formed by a torsion coil spring, one end of which is engaged with the gear case 7 and the other end of which is engaged with the interlocking ring 6. When the interlocking ring 6 moves in the axial direction. The biasing direction of the interlocking ring 6 is reversed halfway. This point will be described later in detail. The reset lever 67 uses the shaft 68 shown in FIG. 8 as a rotation axis, and the other end is freely engageable with a groove 96 provided at the front end of a trigger lever 95 for operating the motor 8 and which is opened forward. It has become.

Next, the operation will be described. First, when the height change handle 5 is advanced to a high speed side, the switching spring 51 for transmitting this movement causes the internal gear 22 to retreat, so that the internal gear 22 engages with the carrier 14 as shown in FIG. A low-torque high-speed rotation state is set. At this time, the internal gear 12 is in a state where the projection 16 is positioned at the center of the groove 70 as shown in FIG. 5 (a) by the bias of the pair of springs 71, 71. The cam projection 15 of the internal gear 12 fits into the cam recess 60 of the interlocking ring 6. Further, the reversing spring 65 urges the interlocking ring 6 rearward, that is, toward the internal gear 12 because the point of engagement with the interlocking ring 6 is behind the point of engagement with the gear case 7. ing.

If the motor 8 is operated by pulling the trigger lever 95 in this state, the drive shaft 9 is driven in the low-torque high-speed rotation mode as described above. When the load torque increases while the internal gear 12 is in operation, as shown in FIG.
The rotation is started against the spring 71, and the rotation causes the cam projection 15 to push the interlocking ring 6 forward as shown in FIGS. 6 (a) and 6 (b). After the reversing position of the reversing spring 65 shown in FIG. 6 (b), the interlocking ring 6 moves forward more rapidly as shown in FIG. 6 (c) with the bias of the reversing spring 65 applied. 22 is advanced.
In other words, the internal gear 22 is switched from the engaged state with the carrier 14 to the engaged state with the gear case 7, so that the driving of the drive shaft 7 is changed to a high torque low speed rotation state. Since the biasing by the reversing spring 65 is applied, the switching is performed smoothly and reliably even when the load fluctuation is gentle.

As shown in FIG. 7 (b), the position where the width L between both ends of the reversing spring 65 is the shortest is the reversing position, and the position shown in FIGS. 7 (a) and 7 (c). , The biasing direction of the interlocking ring 6 with respect to the gear case 7 is reversed. Further, even when the internal gear 22 moves forward, the high / low switching handle 5 remains set at the high speed state due to the bending of the switching spring 51 that connects the internal gear 22. Further, at this time, the reset lever 67 for interlocking the interlocking ring 6 and the trigger lever 95 is in a state of being out of the groove 96 of the trigger lever 95 as shown in FIG. And
Even if the load torque decreases after switching to the high-torque low-speed rotation state and the internal gear 12 attempts to return to the state shown in FIG. 5A, the interlocking ring 6 and the internal gear 22 are opposed to the reversing spring 65. Since there is no returning force, the high-torque low-speed rotation state is maintained as it is.

The return to the low torque high speed rotation state is performed by returning the trigger lever 95 to turn off the motor 8. At this time, the trigger lever 95 pushes the reset lever 67 and pushes back the interlocking ring 6 against the reversing spring 65. At the same time, the internal gear 12 is brought into the state shown in FIG. Returning, the internal gear 22 is further retracted by the spring force accumulated in the switching spring 51, and returns to a state of engaging with the carrier 14.

In order not to return the trigger lever 95,
This means that the motor does not return to the low-torque high-speed rotation state. Therefore, even if the motor is used near the load torque at which the switching is performed, the switching is not repeated. FIG. 11 shows the rotation speed-torque characteristic A at the time of low-torque high-speed rotation and the rotation speed-torque characteristic B at the time of high-torque low-speed rotation. After the switching at the point p, the movement indicated by the arrows a, b, c, and d in the drawing is performed until the trigger lever 95 is returned to return to the initial state.

The normal operation is performed by setting the state in which the low-torque high-speed rotation state is automatically switched to the high-torque low-speed rotation state as described above, that is, the state in which the high / low switching handle 5 is set to the high speed side. Most can be covered, but when using a hole saw or tapping a screw is a task, it is desirable to be in a high torque low speed rotation state from the beginning. In this case, as shown in FIG. 10, the internal gear 22 may be moved forward by retreating the height change handle 5. Regardless of the movement of the internal gear 12, the high torque low speed rotation state is set.

The trigger lever 95 and the reset lever 67
12 and 13, the electromagnetic coil 19 is mounted on the internal gear 12, the interlocking ring 6 and the internal gear 22 are formed of a magnetic material, and the trigger lever 95 is returned. In this state, the interlocking switch 97 may be closed to allow a current to flow through the electromagnetic coil 19, and the interlocking ring 6 and the internal gear 22 may be returned to the initial low-torque high-speed rotation state by magnetic attraction. The interlock switch 97 turns on the main switch SW by pulling the trigger lever 95, and turns off when the motor 8 is energized.

FIG. 14 and subsequent drawings show still another embodiment. This is such that the internal gear 12 also performs the function of the interlocking ring 6, and the cam recess 60, which forms a pair with the cam projection 15 of the internal gear 12, is provided on the thrust plate 77 here. In the drawing, reference numeral 69 denotes a rotation preventing projection of the thrust plate 77. Further, the reversing spring 65 and the reset lever 67 are also engaged with the internal gear 12, but the internal gear 12 is not only movable in the axial direction but also rotates around the axis by a predetermined range. Therefore, the annular groove 18 is formed on the outer peripheral surface of the internal gear 12.
Provided here, the reversing spring 65 and the reset lever 67
Are engaged. FIGS. 15A and 16 show a low torque high speed rotation state, and FIGS. 15B and 17 show a high torque low speed rotation state. The operation is the same as that of the first embodiment.

[0022]

As described above, in the present invention, the cam member shifts the internal gear for shifting by the load change to shift gears, and the gears are automatically shifted without the user performing the switching operation. Therefore, the work efficiency is greatly improved, and at the time of this switching, the reversing spring reverses the biasing direction halfway, so that the reduction gear switching operation accompanying the axial movement of the internal gear for shifting is performed. Will be smooth and reliable.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an important member in one embodiment.

FIG. 2 is a longitudinal sectional view of the same low torque high speed rotation state.

FIG. 3 is a longitudinal sectional view of the same high torque low speed rotation state.

4A is a side view in a low torque high speed rotation state, and FIG. 4B is a side view in a high torque low speed rotation state.

FIG. 5 (a) is a cross-sectional view of a low-torque high-speed rotation state, and (b)
FIG. 3 is a cross-sectional view in a high torque low speed rotation state.

FIGS. 6 (a), (b) and (c) are side views showing movements of an interlocking ring and a reversing spring.

FIGS. 7A, 7B and 7C are side views showing the movement of the reversing spring.

FIG. 8 is a cutaway side view of the same low torque high speed rotation state.

FIG. 9 is a cutaway side view of the above high torque low speed rotation state.

FIG. 10 is a cutaway side view when set in a high torque low speed rotation state according to the embodiment.

FIG. 11 is a rotational speed-torque characteristic diagram of the above.

FIG. 12 is an exploded perspective view of another embodiment.

FIG. 13 is a circuit diagram of the same.

FIG. 14 is an exploded perspective view of another embodiment.

FIG. 15 (a) is a side view of a low-torque high-speed rotation state, and (b).
FIG. 4 is a side view of a high torque low speed rotation state.

FIG. 16 is a longitudinal sectional view of the same low torque high speed rotation state.

FIG. 17 is a longitudinal sectional view of the same high torque low speed rotation state.

[Explanation of symbols]

 6 Interlocking ring 12 Internal gear 22 Internal gear for shifting 65 Reverse spring 71 Spring

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-34678 (JP, A) JP-A-60-25662 (JP, A) JP-A-60-34275 (JP, A) JP-A-63-63 221980 (JP, A) Japanese Utility Model 1-74064 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B25B 21/00

Claims (5)

(57) [Claims] 1. A transmission section in which a reduction ratio is switched by axial movement of at least one internal gear in a multi-stage planetary mechanism, and another internal gear and a gear case rotatable with respect to a gear case. An elastic member provided between the first and second gears to allow rotation of the internal gear with a torque equal to or greater than a predetermined torque; a cam member for converting rotation of the latter internal gear into axial movement of the former internal gear for shifting; An automatic transmission for a rotary electric tool, comprising: a reversing spring for urging the internal gear in the axial direction and reversing the urging direction halfway. 2. The cam device according to claim 1, wherein only the switching from the small reduction ratio to the large reduction ratio is performed.
An automatic transmission for a rotary electric tool according to claim 1. 3. The cam device comprises an interlocking ring interposed between both internal gears and the latter internal gear, and a reversing spring connects the gear case and the interlocking ring. The automatic transmission for a rotary electric tool according to claim 1. 4. The automatic transmission for a rotary electric tool according to claim 1, further comprising a switching handle operable externally and forcibly setting a transmission portion to a large reduction ratio. 5. The automatic transmission for a rotary electric tool according to claim 1, further comprising reset means for returning a shift internal gear of the transmission section to an initial position in conjunction with a stop of the prime mover.