JPH10329056A - Power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform gear shift with the remarkable decrease of a deceleration ratio and compacting maintained by a method wherein a reduction gear having a planetary gear mechanism and an internal contact type planetary mechanism arranged in series and a gear shift mechanism is arranged at the planetary gear mechanism. SOLUTION: A planetary gear mechanism 2 comprises a sun gear 21 arranged at the rotary shaft of a motor 20 fixed at a motor mounting base 10; a ring gear 23; a planetary gear 22 engaged with both a sun gear 21 and a ring gear 23: and a planetary carrier 24 to support the planetary gear 22. The ring gear 23 is axially movably arranged in an idling state at a gear case 8. When the ring gear is positioned on the motor 20 side, rotation thereof is blocked and when it is positioned on the planetary carrier 24 side, it is also engaged with an engaging tooth 25. In a state that rotation of the ring gear 23 is blocked and in a state that the ring gear 23 and the planetary carrier 24 are integrally rotated, rotation transmitted to the planetary carrier 24 has the reduction ratio of a former increased to a value higher thin that of a latter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power tool such as an electric screwdriver and an electric drill, and more particularly to an electric power tool for which portability is important.

[0002]

2. Description of the Related Art In a hand-held power tool,
As a speed reducer for reducing the rotation output of a motor, a speed reducer using a plurality of stages of planetary gear mechanisms is generally used in view of the relationship between the speed reduction ratio and the required space. With this planetary gear mechanism, the motor and the final output part can be coaxial, the rotation is prevented by the rotation prevention and rotation change of the ring gear of the planetary gear mechanism, and the rotation is caused by the spring load. It is widely used in many electric tools, because it is easy to add a function such as tightening torque adjustment utilizing the fact that the blocked ring gear runs idle when the load torque increases.

[0003]

However, regarding the case where it is desired to sufficiently increase the reduction ratio, in the case of using the planetary gear mechanism, it is necessary to stack many steps or use a large-diameter gear. However, there are many problems in terms of the number of parts, weight and bulk. On the other hand, an inscribed planetary mechanism such as a cycloid mechanism or a trochoid mechanism is known as one that can obtain a large reduction ratio in spite of its small size. Although a gear with a reduction ratio can be obtained, the inscribed planetary mechanism has a characteristic that it is not possible to have a shift function using its constituent members, or it is extremely difficult to do so. For the same reason, it is also difficult to provide a tightening torque adjusting function, and this point is an obstacle to use in recent power tools which are required to have multiple functions.
In addition, when high torque is transmitted, a reaction force is applied to the eccentric cam, which is a constituent member, and the axial center shift occurs, which also hinders use of the power tool.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power tool having a small size and a large reduction ratio and having preferable functions.

[0005]

According to the present invention, there is provided a speed reducer in which a planetary gear mechanism and an inscribed planetary mechanism are arranged in series, and a transmission mechanism is provided in the planetary gear mechanism. Have. The speed change is enabled by using not only the inscribed planetary mechanism but also a planetary gear mechanism.

At this time, if the planetary gear mechanism is arranged in front of the inscribed planetary mechanism, the planetary gear mechanism also serves to align the motor with the inscribed planetary mechanism. The contacting type planetary mechanism can be provided with a tightening torque adjusting clutch mechanism, so that multi-functionality can be further achieved. And if a bearing is interposed between the output part of the planetary gear mechanism and the carrier of the inscribed planetary mechanism, the shaft center deviation due to the clutch operation will be eliminated, and despite the existence of the tightening torque adjusting clutch mechanism. If the output of the inscribed planetary mechanism and the output shaft are connected via a connecting part having a play in the radial direction, high efficiency can be maintained. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an embodiment of the present invention will be described. The power tool shown in the figure has various tool bits mounted on an output shaft 9 thereof through a chuck (not shown), and an electric screwdriver or the like. The gear case 8 accommodates a cycloid mechanism 3 as an inscribed planetary mechanism and a planetary gear mechanism 2 located in front of the cycloid mechanism 3.

The planetary gear mechanism 2 includes a motor mount 10
, A sun gear 21 provided on a rotation shaft of a motor 20 fixed to the motor, a ring gear 23, a planetary gear 22 meshing with both the sun gear 21 and the ring gear 23, and a planetary gear 22.
The ring gear 23 is provided so as to freely rotate and move in the axial direction with respect to the gear case 8 as shown in the lower side of FIG. When it is located on the motor 20 side, its rotation is prevented by engagement with the motor mount 10, and when it is located on the planetary carrier 24 side, engagement teeth provided on the outer peripheral surface of the planetary carrier 24 in addition to the planetary gear 22. 25 also meshes.

In the former state in which the rotation of the ring gear 23 is blocked and the latter state in which the ring gear 23 and the planet carrier 24 rotate integrally, the rotation transmitted to the planet carrier 24 is reduced in the former. The ratio increases. Therefore,
The gear can be shifted by allowing the ring gear 23 to be axially moved from the outside.

The cycloid mechanism 3 includes the planet carrier 2
An input shaft 30 formed integrally with the outer ring 4 and having an eccentric cam formed on the outer peripheral surface; a cycloid ring gear 31 disposed freely in the gear case 8;
Cycloid carrier 3 held on the outer surface and the inner surface of cycloid ring gear 31 via bearings 5 and 5, respectively.
2 and a pin 33 provided on the cycloid carrier 32
The bearing 5 is also provided between the input shaft 30 and the cycloid ring gear 31.

Although the cycloid ring gear 31 is freely rotatable with respect to the gear case 8 as described above,
This is to constitute a tightening torque adjusting portion, and a plurality of ridges 40 are provided on the axial end surface of the cycloid ring gear 31 so that the stepped portion of the gear case 8 penetrates in the axial direction. Ball 41 disposed in the provided through hole
Is engaged with the ridge 40 by the bias of the clutch spring 42. In a state where the engagement is maintained, the rotation of the cycloid ring gear 31 is prevented. In the figure, reference numeral 43 denotes an adjusting plate which is screwed with a male screw provided on the outer surface of the front end portion of the gear case 8. By rotating the adjusting plate 43 to advance and retreat in the axial direction to change the compression amount of the clutch spring 42, The engagement force between the ball 41 and the ridge 40 can be changed.

As shown in FIG. 2, a plurality of engaging pieces 37 are protruded concentrically from the cycloid carrier 32 which is the output part of the cycloid mechanism 3.
An engagement plate 3 having a plurality of receiving grooves for receiving the engagement pieces 37
9 is fixed to the output shaft 9 held at the tip of the gear case 8 via a bearing. As shown in FIG. 3, power may be transmitted to the output shaft 9 via a spline coupling portion 91 (preferably an involute spline). In the figure, reference numeral 90 denotes a retaining ring, and reference numeral 81 in FIG.

The output of the motor 20 is output from the planetary gear mechanism 2,
The cycloid ring gear 31 whose rotation is hindered by the locking of the ball 41 by the bias of the clutch spring 42
Is transmitted to the output shaft 9 through deceleration by the cycloid mechanism 3 having Also, the ring gear 2 of the planetary gear mechanism 2
The gear can be shifted as described above by moving the shaft 3 in the axial direction.
1 is higher than the engaging force between the ball 41 provided by the clutch spring 42 and the ridge 40 of the cycloid ring gear 31, the cycloid ring gear 31 Is pushed back to start idling, power transmission to the output shaft 9 is cut off. The tightening torque is limited, and the tightening torque can be changed by changing the compression amount of the clutch spring 42 by the adjusting plate 43.

Here, the planetary gear mechanism 2 interposed between the motor 20 and the cycloid mechanism 3 not only enables the speed change as described above, but also reduces the backlash of the meshing portion of the planetary gear mechanism 2 with the cycloid mechanism. The mechanism exerts a centering action with respect to the axial center deviation of the input shaft 30 of the mechanism. Further, the cycloid ring gear 31 and the input shaft 30 (the planet carrier 2) in the cycloid mechanism 3 are used.
4) and the bearing 5 supporting the cycloid carrier 32 make it possible to use the cycloid ring gear 31 as a component of the torque adjusting clutch. There is no shaft center displacement due to the clutch operation, and a tightening torque adjustment function can be provided while maintaining high efficiency.

In addition, since the power transmission from the cycloid mechanism 3 to the output shaft 9 is performed with the radial play using the engagement piece 37 or the spline coupling portion 91 as described above, Absorbs radial wobble, which is a problem in the case where a clearance must be maintained between the cycloid ring gear 31 and the inner surface of the gear case 8 so that the cycloid ring gear 31 of the cycloid mechanism 3 can idle. Therefore, torque transmission loss can be reduced.
In particular, the one using the engagement piece 37 can be provided at a lower cost than the one using the spline connection part 91.

Cycloid mechanism 3 as an inscribed planetary mechanism
Although the above-mentioned method was used, a tocolloid mechanism may be used.

[0017]

As described above, in the present invention, not only the inscribed planetary mechanism but also the planetary gear mechanism are used, so that the transmission can be shifted while maintaining a large reduction ratio and compactness. Can be obtained. At this time, by disposing the planetary gear mechanism in front of the inscribed planetary mechanism, the planetary gear mechanism performs a centering action between the motor and the inscribed planetary mechanism. A better operation can be obtained on the contrary than in the case of a direct connection with the above, and in connection with this, a tightening torque adjustment clutch mechanism is provided in the inscribed planetary mechanism so that the tightening torque can be adjusted. And multi-functionalization can be further achieved.

In addition, the bearing is interposed between the output portion of the planetary gear mechanism and the carrier of the inscribed planetary mechanism, so that the above-mentioned clutch operation does not cause the axial misalignment, and tightens. High efficiency can be maintained despite the existence of the torque adjusting clutch mechanism.
Further, when the output portion of the inscribed planetary mechanism and the output shaft are connected via a connecting portion having a play in the radial direction, high efficiency can be maintained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a connecting portion between the cycloid mechanism and an output shaft according to the first embodiment.

FIG. 3 is an exploded perspective view of another example of a connecting portion between the cycloid mechanism and the output shaft according to the first embodiment.

[Explanation of symbols]

 2 Planetary gear mechanism 3 Cycloid mechanism

Claims (5)

[Claims] 1. A power tool comprising a speed reducer in which a planetary gear mechanism and an inscribed planetary mechanism are arranged in series, and a transmission mechanism provided in the planetary gear mechanism. 2. The power tool according to claim 1, wherein the planetary gear mechanism is provided at a stage preceding the inscribed planetary mechanism. 3. The electric tool according to claim 2, wherein a tightening torque adjusting clutch mechanism is provided on the inscribed planetary mechanism. 4. The power tool according to claim 1, wherein a bearing is interposed between an output portion of the planetary gear mechanism and a carrier of the inscribed planetary mechanism. 5. The power tool according to claim 3, wherein the output part of the inscribed planetary mechanism and the output shaft are connected via a connection part having a play in the radial direction.