JP2002264031A - Power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power tool having a power transmission system capable of buffering a starting shock and transferring torque in both normal and reverse rotation directions with a simple structure. SOLUTION: In a power screw driver, an elastically deformable C-type spring member 18 is intervened between a drive gear 13 engaging with a pinion 12 mounted on an output shaft of an electric motor 11 and a middle gear 17 coaxially arranged next to the drive gear 13. The spring member 18 is engaged with the drive gear 13 and the middle gear 17 in a rotation direction and elastically deformed (bent) to a direction to enlarge a diameter according to a load of driven side when rotation of the drive gear 13 is transferred to the middle gear 17, and thereby the starting shock is absorbed or relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric tool such as an electric screwdriver and an electric drill, and more particularly to a torque transmission technique for transmitting the torque of an electric motor to a tool bit.

[0002]

2. Description of the Related Art Conventionally, in an electric screwdriver and an electric drill used for screw tightening work, the torque of an electric motor is transmitted to a driver bit or a drill bit as a tool bit through a gear device.

[0003]

In the case of an electric tool provided with the above-described gear device, when the electric motor is started in order to grasp the tool body by hand and perform a screw tightening operation or a drilling operation, the electric motor is activated. An impact called a shock occurs instantaneously. Such a starting shock acts as a recoil on the operator's hand, resulting in poor usability. In addition, the repetition of the starting shock on the electric motor and the gear device adversely affects the durability. Therefore, in order to eliminate the starting shock as described above, a power tool using a coil spring (spring clutch) for transmitting torque between two rotating members in a torque transmission system has been proposed. Kaihei 7-2144
No. 17 publication. In the power transmission device for an electric tool described in the above publication, a coil spring is disposed on the outer periphery of the drive-side shaft and the outer periphery of the driven-side shaft. It is configured to rotate and wind around the outer periphery of the driven shaft to transmit torque. According to this, it is possible to obtain a buffering effect against the starting shock.

[0004]

However, in the case of the power transmission device using the coil spring as described above, the rotation transmission direction is limited to one direction, and it is necessary to perform the rotation in both the forward rotation and the reverse rotation. , 2 for forward rotation and reverse rotation
Different types of coil springs are required. As a result, there is a problem that the number of parts increases and the structure becomes complicated or large accordingly. Furthermore, since the torque is transmitted by the frictional force between the coil spring and the outer periphery of the shaft, the coil spring may slip and interrupt the torque transmission.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. It is an object of the present invention to be able to buffer a starting shock and to transmit torque in both forward and reverse directions with a simple structure. It is to provide a power tool with a possible power transmission device.

[0006]

Means for Solving the Problems To achieve the above object, a power tool according to the present invention has a configuration as described in each claim. In the power tool according to the first aspect, the power transmission device has an elastically deformable C-shaped torque transmission member interposed between the two rotating members in the torque transmission system. One end of the C-shaped torque transmitting member is in contact with a radial wall surface formed on one rotating member, and the other end is in contact with a radial wall surface formed on the other rotating member. This is a configuration in which torque is transmitted in a state of being performed. Here, the C-shape includes a part that forms a part of a circular arc or an arc shape, and is not limited by the length or curvature of the arc. Further, the radial wall surface refers to a surface arranged in a direction crossing the circumferential direction.
Therefore, according to the first aspect of the present invention, when the electric motor is started, the starting shock can be absorbed or reduced by the elastic deformation of the C-shaped torque transmitting member between the two rotating members. As a result, the drive motor or the torque transmission system can be protected from the starting shock, and the durability can be improved. In addition, the adoption of the C-shaped torque transmitting member allows the torque to be reliably transmitted in both the forward and reverse directions with a simple structure.

In this case, as described in claim 2, the two rotating members are arranged at a predetermined interval on the same axis, and at least one of the rotating members is
It is preferable to have a recess into which one end in the axial direction of the C-shaped torque transmitting member is fitted. In this case, the axial length of the two rotating members including the torque transmitting member can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power tool according to a first embodiment of the present invention will be described below with reference to FIGS. This embodiment is applied to an electric screwdriver as an example of a rotary electric tool in which a tip tool rotates,
FIG. 1 is a side view showing the entire electric screwdriver. The electric screwdriver 1 includes a main body 2, a handle 3, and a nose 4. The handle 3 is provided with a trigger-type main switch 5. When the main switch 5 is pulled, the main body case 2 of the main body 2 is pulled.
Electric motor 11 built in a (see FIGS. 2 and 3)
Starts.

FIG. 2 and FIG. 3 are cross-sectional views showing the internal structure of the main body 2 and the nose 4, and show a power transmission device of an electric screwdriver. 2 and 3 show almost half of the front end side of the main body 2. As shown in the figure, a power transmission device for transmitting the torque of the electric motor 11 to a driver bit B as a tip tool is constituted by a gear device 10. Hereinafter, the gear device 10
Will be described.

A pinion 12 formed on the output shaft of the electric motor 11 meshes with a drive gear 13. Drive gear 1
3 is rotatably fitted to the intermediate shaft 14. Intermediate shaft 1
4 penetrates the drive gear 13 and has a bearing 15 at one end of the main body case 2a and a nose portion case 4a at the other end.
Are rotatably supported by bearings 16. An intermediate gear 17 is fixedly or integrally formed on the intermediate shaft 14, and the intermediate gear 17 and the drive gear 13 are arranged concentrically and in parallel at a predetermined interval. An elastically deformable C-shaped metal spring member 18 for buffering is interposed between the intermediate gear 17 and the drive gear 13, and the rotation of the drive gear 13 is rotated via the spring member 18. 17 is transmitted. The drive gear 13, the intermediate gear 17, and the spring member 18 constitute a shock-absorbing mechanism for starting shock. The drive gear 13 and the intermediate gear 17 correspond to two rotating members in the torque transmission system according to the present invention. The spring member 18 corresponds to the C-shaped elastically deformable torque transmitting member referred to in the present invention.

As shown in an exploded perspective view of FIG. 4, a C-shaped recess 13a is formed on one side of the drive gear 13, and a C-shaped recess is formed on the side of the intermediate gear 17 in opposition to the C-shaped recess 13a. A portion 17a is formed. The spring member 18 is formed in a C-shape in which a part in the circumferential direction of the cylinder is cut out, one end in the axial direction is inserted into the C-shaped recess 13a, and the other end is the outer periphery of the C-shaped protrusion 17a. It is mounted in a state fitted to the surface. In this mounting state, the spring member 18 has the notch opening end face 18a formed on the radial wall 13 of the C-shaped recess 13a.
b and the radial wall surface 17b of the C-shaped projection 17a.

As described above, the spring member 18 is connected to the drive gear 1.
3 and the intermediate gear 17 are engaged in the rotational direction. Therefore, as shown in FIG. 5, when the drive gear 13 is rotated clockwise or counterclockwise, one of the open end surfaces 18a is pushed by one of the radial wall surfaces 13b of the C-shaped recess 13a, The other of the open end faces 18a is the C-shaped convex portion 17.
The rotation is transmitted while being pressed against one of the radial wall surfaces 17b. At this time, the spring member 18 is elastically deformed (hereinafter, referred to as the direction in which the diameter thereof is increased in response to the load (resistance) on the driven side.
(Referred to as bending), and the bending damps the starting shock. The width of the C-shaped recess 13a is set so as to have a space sufficient to allow the spring member 18 to bend.

As shown in FIG. 2 and FIG.
Meshes with a driven gear 19, which transmits rotation to a spindle 22 via a clutch 21. The spindle 22 is supported by the nose case 4a by a bearing 23 so as to be rotatable and axially movable, and a driver bit B can be mounted on the tip (front end) side thereof. The clutch 21 includes a clutch tooth 21a formed at a predetermined pitch in a circumferential direction on a distal end surface (left side surface in the drawing) of the driven gear 19, and a clutch tooth 21b formed on a shaft end surface of a spindle 22 opposed to the clutch tooth 21a. The spindle 22 is engaged with the driven gear 19 by moving to the driven gear 19 side. The spindle 22 is always pushed to the front end side by a compression spring 24 interposed between the driven gear 19 and the clutch 21 so that the clutch 21 is disengaged.

The driven gear 19 is fixed on a driven shaft 20. The driven shaft 20 passes through the driven gear 19,
The rear end is rotatably supported by the main body case 2 a by a bearing 25, and the front end is rotatably and rotatably supported by a bearing 26 with the front end inserted into the cylindrical hole of the spindle 22. The axial load when the spindle 22 is pushed to the rear side is received by a thrust bearing 27 disposed on the rear side of the driven gear 19. Gear device 1 for transmitting rotation of electric motor 11 to driver bit B
0 is configured as described above, and includes the pinion 12, the drive gear 13, the intermediate gear 17, the driven gear 19, the clutch 2
1, the spindle 22 and the like constitute a torque transmission system according to the present invention.

On the other hand, a bit mounting hole 22a for inserting a driver bit B for screw fastening is formed at a fixed depth on the tip end side of the spindle 22. A steel ball 29 elastically biased radially inward by a leaf spring 28 is provided in the bit mounting hole 22a. The rear end side of the driver bit B is inserted into the bit mounting hole 22a, and the steel ball 29 is pushed in while being displaced radially outward against the elastic force of the leaf spring 28, whereby the driver bit B is mounted. It can be mounted in the hole 22a. When the driver bit B is pushed into a certain position, the steel ball 29
Of the driver bit B, thereby maintaining the mounted state of the driver bit B.

An adjusting sleeve 30 is mounted on the front end of the nose case 4a via a screw shaft portion 30a, and a stopper sleeve 31 is detachably mounted on the front end of the adjusting sleeve 30. The front end of the driver bit B slightly protrudes from the front end of the stopper sleeve 31. By rotating the adjusting sleeve 30 in the axial direction, the front end of the stopper sleeve 31 with respect to the driver bit B (stopper surface 31)
The position of a) can be arbitrarily adjusted, whereby the screwing depth of the screw can be adjusted.

The electric screwdriver 1 configured as described above operates as follows. FIG. 2 shows a state in which the driver bit B is not pressed against a screw (not shown) to be tightened.
Is pushed forward by the compression spring 24, and the engagement of the clutch 21 is released. Accordingly, if the electric motor 11 is started by pulling the trigger-type main switch 5 in this state, the driven gear 19 is idled from the pinion 12 via the drive gear 13, the spring member 18, and the intermediate gear 17. When the tip of the driver bit B is pressed against the screw in this state, the spindle 22 is moved rearward as shown in FIG. 3, whereby the clutch 21 is engaged, and the spindle 22 is rotated. Therefore, the driver bit B is rotated and the screw is tightened.

In the screw tightening (or retightening) operation as described above, a start shock occurs when the electric motor 11 is started. According to the present embodiment, the drive gear in the gear device 10 is driven. 13 and intermediate gear 1
The above-mentioned starting shock can be absorbed or reduced by a C-shaped spring member 18 interposed therebetween. FIG. 5 is an explanatory view of the buffering action by the spring member 18.
(A) shows the state before starting or at the time of no load, and FIG.
(C) shows the time of buffering. The upper side of the figure shows the relationship between the drive gear 13 and the spring member 18, and the lower side shows the relationship between the intermediate gear 17 and the spring member 18. FIG.
In the state shown in (A), when the electric motor 11 is started and the drive gear 13 is rotated clockwise or counterclockwise, as described above, the spring member 18 is moved to the open end face 18a.
Is pressed by one radial wall surface 13b of the C-shaped concave portion 13a, and the other of the open end surfaces 18a is pressed against one radial wall surface 17b of the C-shaped convex portion 17a.
To transmit torque. At this time, the spring member 18 bends in the direction of increasing the diameter as shown in FIG. 5B or 5C due to the load (rotational resistance of the bearings 15, 16, 25, 26, etc.) acting on the driven side. The drive gear 13 and the intermediate gear 17 are relatively displaced in the rotation direction. The amount of deflection of the spring member 18 at this time corresponds to the magnitude of the load on the driven side. Then, the starting shock generated in the rotation transmission system of the gear device 10 due to the bending of the spring member 18 is absorbed or reduced.

In addition, when the starting shock as described above occurs, the spindle 22 is pushed in to tighten the screw and the clutch 2 is pressed.
The same occurs when the gears 1 mesh with each other, but this is also absorbed or reduced by the buffering action due to the bending of the spring member 18 as in the case of starting the electric motor 11. The shock-absorbing effect of the starting shock due to the bending of the spring member 18 is particularly effectively exerted in the gear device 10 that does not involve a slip in the torque transmission system, such as a belt transmission device, and is frequently repeated. Gearing 10 from starting shock
Further, the durability can be improved by protecting the electric motor 11 which is a driving source thereof. In the case of a portable power tool such as the electric screwdriver 1, the starting shock is transmitted as a recoil to the user's hand and impairs usability, but as described above, the starting shock related to the torque transmission system is absorbed or reduced. As a result, the recoil at hand is reduced, and the usability is improved.

Further, in this embodiment, since the starting shock is prevented by the C-shaped spring member 18, the torque can be reliably transmitted in both the forward rotation and the reverse rotation, and it is a single component. Therefore, assembling is easier, the shape is small, the structure can be simplified, and the cost can be reduced as compared with the conventional type using a coil spring. Furthermore, in the case of the conventional coil spring type, there is a possibility that the coil spring slips and the torque transmission is interrupted, but according to the present embodiment, such a phenomenon does not occur.

Next, a second embodiment according to the present invention will be described with reference to FIG.
It will be described based on. This embodiment relates to a shock-absorbing mechanism for a starting shock, and FIG. 6 is a perspective view showing an exploded state. In this embodiment, the elastically deformable C-shaped torque transmitting member is formed in a half-arc shape, that is, in a C-shape having a shorter arc length than the C-shaped spring member 18 described in the first embodiment. Two spring members 38
Is adopted. A spring member 3 is provided on a side surface of the drive gear 13.
8 is formed symmetrically, one end of the spring member 38 in the axial direction is inserted into the C-shaped recess 13d, and the circumferential end face abuts against the radial wall surface 13e of the C-shaped recess 13d. Is done. On the side surface of the intermediate gear 17 is formed an engaging projection 17d radially projecting at an interval of 180 degrees with respect to the circumferential direction. The peripheral end face of the side is abutted. Thus, the spring member 38 is connected to the drive gear 1.
3 and the intermediate gear 17 are engaged in the rotational direction. The rest is configured in the same manner as in the first embodiment.

Therefore, according to the embodiment configured as described above, the start shock when the electric motor 11 is started or when the clutch 21 is engaged is the same as in the first embodiment described above. Buffering can be provided by the bending of the member 38.

Note that the present invention is not limited to the illustrated embodiment, and can be appropriately changed without departing from the gist of the present invention. In the first and second embodiments, the drive gear 13 is provided with the C-shaped recesses 13a and 13d, and the intermediate gear 17 is provided with the C-shaped protrusion 17a and the engagement protrusion 17d.
This may be reversed, both may be C-shaped concave portions, and in the case of the first embodiment, both may be C-shaped convex portions. Further, the spring members 18 and 38 are not limited to those made of metal, and rubber or resin springs can be used. The mounting portion of the cushioning spring members 18 and 38 is not limited to between the drive gear 13 and the intermediate gear 17, but a portion closer to the electric motor 11 which is a driving source as much as possible has a buffer effect. Can be raised. Further, in the present embodiment, the case where the present invention is applied to the electric screwdriver 1 has been described. However, the present invention can be applied to an electric tool such as an electric drill and an electric screwdriver drill in which a tip tool rotates.

[0024]

As described in detail above, according to the present invention,
It is possible to provide an electric tool having a power transmission device capable of buffering a start shock and having a simple structure and capable of transmitting torque in both forward and reverse directions.

[Brief description of the drawings]

FIG. 1 is a side view showing an entire electric screwdriver.

FIG. 2 is a cross-sectional view showing an internal structure of a main body portion and a nose portion, showing a state before a clutch is engaged.

FIG. 3 is a cross-sectional view showing an internal structure of a main body portion and a nose portion, showing a state where a clutch is engaged.

FIG. 4 is an exploded perspective view showing a shock-absorbing mechanism of the starting shock according to the first embodiment.

5A and 5B are diagrams illustrating a buffering action and a rotation transmitting action by a spring member, wherein FIG. 5A shows a state before starting or when there is no load, FIG. 5B shows a state when rotating clockwise, and FIG. Is shown.

FIG. 6 is an exploded perspective view showing a shock-absorbing mechanism of a starting shock according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric screwdriver 10 Gear device 11 Electric motor 12 Pinion 13 Drive gear 17 Intermediate gear 18 Spring member

Claims (2)

[Claims] 1. An electric tool comprising a power transmission device for transmitting torque of an electric motor to a driven object, wherein the power transmission device is elastically deformed between two rotating members in a torque transmission system. A possible C-shaped torque transmitting member has one end abutting on a radial wall surface formed on one rotating member and the other end rotating on the other side in the rotating direction. An electric tool, wherein torque is transmitted in a state of being in contact with a radial wall surface formed on a member. 2. The power tool according to claim 1, wherein the two rotating members are arranged at a predetermined interval on the same axis, and at least one of the rotating members is the torque transmitting member. A power tool having a concave portion into which one end in the axial direction is fitted.