JPH068151A - Automatic speed changer for rotary power tool - Google Patents

Abstract

PURPOSE:To conduct speed change smoothly and surely according to load change by equipping a speed change portion to change a deceleration ratio; elastic bodies to allow the rotation of an internal gear; a cam member; and a turning-over spring to energize a speed change internal gear and to reverse an energizing direction. CONSTITUTION:The automatic speed changer of a rotary power tool is equipped with a speed change portion that conducts the changeover of a deceleration ratio by means of the axial movement of at least one internal gear 22 at a plural step planetary mechanism; and springs 71 that are rotatable in reard to a gear case and are provided between the other internal gear 12 and the gear case and allow the rotation of the internal gear 12 by means of torque that exceeds predetermined torque. The rotation of the internal gear 12 is converted into the axial movement of the speed change internal gear 22 by means of a cam projection 15, and the speed change internal gear 22 is energized axially by means of a turning-over spring 65, and at the same time this energizing direction is reversed on the way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission system for automatically performing a shifting operation in a rotary electric tool such as an electric screwdriver in response to load fluctuations.

[0002]

2. Description of the Related Art There are various rotary electric tools in which the speed reduction ratio can be switched according to the load. Conventional transmissions, however, change gears only by a user's switching operation. Further, which reduction ratio (output characteristic) is selected by this switching operation depends on the user's judgment.

[0003]

Considering screw tightening and drilling work, work is first started at a reduced speed ratio, that is, low torque and high speed rotation, and thereafter, the reduction ratio is increased to increase high torque and low speed rotation. However, in the conventional system, it is necessary to set a reduced speed ratio at the start of work and switch to a high reduction ratio in the middle of work. This burden becomes large.

As disclosed in Japanese Unexamined Patent Publication No. 63-221980, there is provided a device which can be automatically switched according to a load change, but the conventional device of this type is
Switching was not smooth or reliable, and load fluctuations near the switching point caused frequent switching between high and low, resulting in gear damage and loud noise. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an automatic transmission device for a rotary electric power tool, which is capable of smoothly and reliably performing gear shifting according to load variations. In addition, it is an object of the present invention to provide an automatic transmission that does not cause frequent switching operations due to load variations near the switching points.

[0006]

SUMMARY OF THE INVENTION The present invention, however, 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 is rotatable with respect to a gear case. The elastic body, which is provided between the other internal gear and the gear case and allows the internal gear to rotate with a torque equal to or higher than a predetermined torque, and the rotation of the latter internal gear in the axial direction of the former internal gear for shifting. It is characterized in that it is provided with a cam member that converts into movement and a reversing spring that urges the speed-changing internal gear in the axial direction and reverses this urging direction midway.

[0007]

According to the present invention, the cam member moves the internal gear for speed change due to the load change to perform the speed change, and at this time, the reversing spring reverses the urging direction of the internal gear for changing the speed of the internal gear for speed change. The operation of switching the reduction ratio due to 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 the illustrated embodiments. This rotary electric tool is, as shown in FIG. 8, a motor 8 which is rotated by a power source supplied from a removable battery pack.
Is driven by the reduction mechanism in the gear case 7 to drive the drive shaft 9 provided with the chuck 90. The reduction mechanism is provided in the gear case 7 as shown in FIG.
It has a three-stage planetary mechanism.

The first stage planetary mechanism uses a sun gear as a gear attached to the output shaft of the motor 8, and is composed of an internal gear 12, a planetary gear 13, and a carrier 14 holding the planetary gear 13. The second stage planetary mechanism is composed of a sun gear 21, an internal gear 22, a planetary gear 23, and a carrier 24 that are integrally provided on the carrier 14, and the third stage planetary mechanism is a sun that is integrally provided on 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 the interlocking pin 35 projecting from the carrier 34, a lock plate 92 arranged on the outer periphery of the drive shaft 9, and a lock member located between the lock plate 92 and the interlocking pin 32. It is transmitted to the drive shaft 9 through (not shown). 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 thereof is omitted here. Further, the internal gear 32 in the third stage planetary mechanism is normally in the state of being unable to rotate, and when the tightening torque exceeds the set torque, it starts rotating and cuts the power transmission to the drive shaft 9 to limit the tightening torque. It also serves as a member of the torque limiter, but the description of this point will also be omitted.

Now, the internal gear 22 in the above-mentioned second stage planetary mechanism is provided so as to be rotatable about the axis and movable in the axial direction, and at the rear end in the axial direction. Has an engaging portion with the carrier 14 in the first stage planetary mechanism, and has a gear case 7 at the front end in the axial direction.
As shown in FIG. 2, when the internal gear 22 is engaged with the carrier 14, the carrier 14 and the second stage planetary mechanism in the first stage planetary mechanism are provided. Since the carrier 24 in the mechanism is directly connected, the drive shaft 9 is driven at low torque and high speed, and when the internal gear 22 moves forward and engages with the gear case 7 as shown in FIG. Since the deceleration in the planetary mechanism of the stage is also performed, the drive shaft 9 is driven by high torque and low speed rotation. The switching of the reduction ratio is not limited to this example. Further, as shown in FIG. 1, an annular groove 25 is formed on the outer peripheral surface of the internal gear 22, and the end portion of the switching spring 51 held by the outer surface of the gear case 7 is engaged therewith. . This switching spring 5
Reference numeral 1 transmits the sliding motion of the height switching handle 5 to the internal gear 22.

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

An interlocking ring 6 is arranged between the internal gear 12 and the internal gear 22. The interlocking ring 6 is provided with a plurality of cam recesses 60 corresponding to the cam protrusions 15 of the internal gear 12, and the protrusions 61 protruding from the outer peripheral surface are arranged 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. Further, the reversing spring 65 and the reset lever 67 are provided on the outer peripheral surface of the interlocking ring 6.
And are connected.

The reversing spring 65 is formed of 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, and when the interlocking ring 6 moves in the axial direction. The energizing direction of the interlocking ring 6 is reversed in the middle of the process. Note that this point will be described later in detail. The reset lever 67 has a shaft 68 shown in FIG. 8 as a rotation shaft, and the other end thereof is freely engageable with a groove 96 provided at the front end of a trigger lever 95 for operating the motor 8 and open to the front. Has become.

Next, the operation will be described. First, when the high / low switching handle 5 is moved forward and set to the high speed side, the switching spring 51 transmitting this movement causes the internal gear 22 to retract, so that the internal gear 22 engages with the carrier 14 as shown in FIG. Low torque and high speed rotation state. Further, at this time, the internal gear 12 is in a state in which the protrusion 16 thereof is located at the center of the groove 70 as shown in FIG. 5A by the bias of the pair of springs 71, 71. The cam protrusion 15 of the internal gear 12 is fitted in the cam recess 60 of the interlocking ring 6. Further, since the engagement point of the reversing spring 65 with the interlocking ring 6 is behind the engagement point with the gear case 7, the interlocking ring 6 is biased rearward, that is, toward the internal gear 12 side. ing.

If the trigger lever 95 is pulled in this state and the motor 8 is operated, the drive shaft 9 is driven in the low torque high speed rotation mode as described above. If the load torque increases while the internal gear 12 is in motion, as shown in Fig. 5 (b),
The rotation starts 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). When the reversing position of the reversing spring 65 shown in FIG. 6 (b) is passed, the interlocking ring 6 advances further rapidly as shown in FIG. 6 (c) with the bias of the reversing spring 65 applied, and the internal gear is moved. Move 22 forward.
That is, the internal gear 22 is switched from the engagement state with the carrier 14 to the engagement state with the gear case 7, and therefore the driving of the drive shaft 7 is changed to the high torque and low speed rotation state. Since the urging force is applied by the reversing spring 65, the switching can be performed smoothly and surely even if the load fluctuation is gentle.

In the reversing spring 65, as shown in FIG. 7 (b), the position where the width L between both ends is the shortest is the reversing position, and the position shown in FIGS. 7 (a) (c). Then, the biasing direction of the interlocking ring 6 with respect to the gear case 7 is opposite. Further, even when the internal gear 22 moves forward, the high / low switching handle 5 maintains the state set to the high speed state due to the deflection of the switching spring 51 connected to the internal gear 22. Further, the reset lever 67 for interlocking the interlocking ring 6 and the trigger lever 95 is in a state of being pulled out from the groove 96 of the trigger lever 95 at this point, as shown in FIG. And
Even when the internal gear 12 tries to return to the state shown in FIG. 5 (a) after the switching to the high torque / low speed rotation state and the internal gear 12 returns to the state shown in FIG. 5 (a), the interlocking ring 6 and the internal gear 22 are resisted against the reversing spring 65. Since there is no restoring 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, and at the same time, the internal gear 12 moves to the state shown in FIG. Then, the internal gear 22 is further retracted by the spring force accumulated in the switching spring 51 to return to the state of engaging with the carrier 14.

In order not to return the trigger lever 95,
It does not return to the low-torque high-speed rotation state, and therefore, even if it is used in the vicinity of the load torque to be switched, the switching is not repeated. FIG. 11 shows the number of revolutions-torque characteristic A at the time of low-torque high-speed rotation and the number of revolutions-torque characteristic B at the time of high-torque low-speed rotation. After the switching at the point p, the movements shown by the arrows a, b, c, and d in the drawing are performed until the initial state is restored by returning the trigger lever 95.

By the way, in the normal operation, as described above, the state in which the low torque high speed rotation state is automatically switched to the high torque low speed rotation state, that is, the high / low switching handle 5 is set to the high speed side is set. Most of them can be covered, but when the use of a hole saw or tapping of screws is the work content, 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 height switching handle 5 may be moved backward and the internal gear 22 may be moved forward. Regardless of the movement of the internal gear 12, the high torque low speed rotation state is set.

Trigger lever 95 and reset lever 67
12 and FIG. 13, the trigger lever 95 is returned by mounting the electromagnetic coil 19 on the internal gear 12 and forming the interlocking ring 6 and the internal gear 22 by a magnetic material as shown in FIGS. In the state, the interlocking switch 97 may be closed and a current may flow in the electromagnetic coil 19 to return the interlocking ring 6 and the internal gear 22 to the initial state of low torque and high speed rotation by the magnetic attraction force. The interlocking switch 97 pulls the trigger lever 95 to turn on the main switch SW, and turns off when the motor 8 is energized.

Still another embodiment is shown in FIG. In this structure, the internal gear 12 also functions as the interlocking ring 6, and the cam recess 60 that forms a pair with the cam projection 15 of the internal gear 12 is provided in the thrust plate 77 here. Reference numeral 69 in the figure denotes a rotation stop protrusion of the thrust plate 77. Further, although the reversing spring 65 and the reset lever 67 are also engaged with the internal gear 12, not only the internal gear 12 is movable in the axial direction, but also the internal gear 12 rotates about the axis by a predetermined range. Therefore, the annular groove 18 is formed on the outer peripheral surface of the internal gear 12.
Is provided, and the reversing spring 65 and the reset lever 67 are provided here.
Are engaged. FIGS. 15 (a) and 16 show a low torque high speed rotation state, and FIGS. 15 (b) and 17 show a high torque low speed rotation state. Operationally, it is the same as the first embodiment.

[0022]

As described above, according to the present invention, the cam member moves the internal gear for speed change according to the load change to perform the speed change, and the speed is automatically changed without the user performing the switching operation. Therefore, the work efficiency is significantly improved. Moreover, at the time of this switching, the reversing spring reverses the urging direction midway, so the switching operation of the reduction ratio accompanying the axial movement of the internal gear for shifting is performed. Is smooth and reliable.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an important member according to an embodiment.

FIG. 2 is a vertical cross-sectional view of the same low-torque, high-speed rotation state.

FIG. 3 is a vertical cross-sectional view of the same high torque, low speed rotation state.

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

FIG. 5 (a) is a cross-sectional view in a state of low torque and high speed rotation, (b).
FIG. 4 is a cross-sectional view of a high torque low speed rotation state.

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

7 (a), (b) and (c) are side views showing the movement of the reversing spring.

FIG. 8 is a cutaway side view of the above-described low torque, high speed rotation state.

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

FIG. 10 is a cutaway side view when the above-described high torque low speed rotation state is set.

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 above.

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, (b).
FIG. 6 is a side view of a high torque low speed rotation state.

FIG. 16 is a vertical cross-sectional view of the same low-torque, high-speed rotation state.

FIG. 17 is a vertical cross-sectional view of the same high torque, low speed rotation state.

[Explanation of symbols]

 6 Interlocking ring 12 Internal gear 22 Internal gear for speed change 65 Inversion spring 71 Spring

Claims (5)

[Claims] 1. 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 another internal gear and a gear case that are rotatable with respect to the gear case. An elastic body that is provided between the internal gears to allow the internal gear to rotate with a torque equal to or greater than a predetermined torque, a cam member that converts the rotation of the latter internal gear into the axial movement of the former internal gear for shifting, and An automatic transmission for a rotary electric tool, comprising: a reversing spring that urges the internal gear in the axial direction and reverses the urging direction midway. 2. The cam device only switches from a small reduction ratio to a large reduction ratio.
An automatic transmission for a rotating electric tool as described. 3. The cam device is composed of an interlocking ring interposed between both internal gears and the latter internal gear, and a reversing spring connects between the gear case and the interlocking ring. An automatic transmission for a rotary electric tool according to claim 1. 4. The automatic transmission device for a rotary electric tool according to claim 1, further comprising a switching handle that can be operated externally and forcibly sets the transmission unit to a large reduction ratio. 5. The automatic transmission device for a rotary electric tool according to claim 1, further comprising reset means for returning the shifting internal gear of the transmission unit to the initial position in association with the stop of the prime mover.