JP4043567B2 - Impact tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a striking tool such as an electric hammer or a hammer drill, and more particularly to a structure for reducing the impact.
[0002]
[Prior art]
In this type of striking tool, measures are taken to mitigate a large impact generated at the time of hitting the bit and to improve the durability of the crank mechanism portion including the piston pin, the crankpin, and the like. For example, the impact mitigation structure disclosed in Japanese Utility Model Publication No. 54-44304 is configured to absorb the impact at the time of impact by deforming a synthetic rubber attached to the piston.
[0003]
[Problems to be solved by the invention]
However, since the conventional configuration is configured to absorb the impact by deforming the synthetic rubber, the impact absorbing capability is not sufficient. Then, an object of this invention is to provide the impact tool which can fully relieve | moderate the reaction force at the time of the air compression accompanying the action | operation of a piston.
[0004]
[Means for Solving the Problems]
For this reason, this invention was set as the impact tool of the structure described in the said claim.
According to the striking tool of claim 1, when a reaction force (external force acting on the opposite side to the striking direction) is applied to the crankpin during air compression, the intermediate rotating body is elastically applied. It rotates with respect to the crank gear against the force, and this reaction force is alleviated. Thus, the reaction force generated during the air compression is alleviated by the relative rotation of the intermediate rotating body with respect to the crank gear, so that it is not directly applied to the crank mechanism such as the crank gear, the crank pin, or the piston pin. Thus, the durability can be improved, and the reaction force transmitted to the operator can be reduced.
In addition, it is not a configuration that relaxes the reaction force by deforming the synthetic rubber as in the past, but a configuration that relaxes by rotating the intermediate rotating body with respect to the crank gear, ensuring a larger relaxation allowance than conventional As a result, the reaction force can be relaxed more reliably than in the prior art.
[0005]
Although not included in the first aspect of the invention, the piston is supported so as to be displaceable with respect to the piston pin along the moving direction of the piston, and the piston is elastically biased in the striking direction using a compression spring. A similar effect can be obtained by a striking tool (related technique) characterized by the above.
According to this striking tool, when a reaction force that exceeds the biasing force of the compression spring is applied to the piston during air compression, the piston is displaced against the piston pin against the biasing force of the compression spring. This reaction force is alleviated. Since the reaction force generated during air compression is mitigated by the movement of the piston relative to the piston pin, it is not added to the crank mechanism such as the crank gear, the crank pin, or the piston pin as it is. The reaction force transmitted to the operator can be alleviated.
And since it is the structure which relieves reaction force by displacing a piston with respect to a piston pin, a reaction force absorption margin larger than before can be set, and reaction force can be relieved reliably.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the invention described in claim 1 (hereinafter simply referred to as an embodiment) will be described with reference to FIGS . FIG. 1 shows an internal structure of an electric hammer 1 as an example of an impact tool. In the figure, reference numeral 2 denotes an electric motor as a drive source of the electric hammer 1. A gear 2 a is formed on the output shaft of the electric motor 2, and the gear 2 a meshes with the crank gear 3. The crank gear 3 is rotatably supported by the crankcase 10 via bearings 4 and 5. In the center of the upper surface of the crank gear 3, a circular hole 3a is formed with a certain depth. In this circular hole 3a, the shaft portion 7a of the intermediate rotator 7 is rotatably supported via a bearing 6, so that the intermediate rotator 7 is rotatably supported coaxially with respect to the crank gear 3. ing.
[0007]
A flange portion 7b is provided on the upper portion of the shaft portion 7a. The flange portion 7b faces the upper surface of the crank gear 3, and projections 7c and 3b are formed on the lower surface of the flange portion 7b and the upper surface of the crank gear 3, respectively. Each part is hooked. By this torsion spring 8, the intermediate rotating body 7 is urged in one rotation direction with respect to the crank gear 3.
[0008]
A crankpin 7d is disposed on the upper surface of the flange portion 7b at a position deviated from the center of rotation (axial center of the shaft portion 7a) by a certain dimension. The rear end side (right end side in the figure) of the connecting rod 9 is connected to the crank pin 7d via a bearing 9a so as to be relatively rotatable. A piston 11 is attached to the front end of the connecting rod 9 via a connecting pin 9b. The rotational power of the electric motor 2 is converted into the reciprocating motion of the piston 11 in the cylinder 12 through a crank mechanism mainly composed of the crank pin 7d and the connecting rod 9. A striking piece 13 is movably accommodated in the cylinder 12 and in front of the piston 11, and an air chamber 14 is formed between the striking piece 13 and the piston 11.
The cylinder 12 is accommodated in a cylindrical barrel 15 attached to the front end of the crankcase 10. A flange portion 12 a is formed at the front end of the cylinder 12, and the flange portion 12 a is held at the front end of the barrel 15. A cover 16 is attached around the barrel 15.
A slide sleeve 17 is mounted on the outer peripheral surface of the cylinder 12 so as to be movable in the front-rear direction. A compression spring 19 is interposed between the rear end of the slide sleeve 17 and a retaining ring 18 attached to the outer peripheral surface of the cylinder 12. The slide sleeve 17 is biased forward (leftward in the figure) by the compression spring 19. At the front end of the slide sleeve 17, insertion pieces 17 a to 17 a are provided so as to protrude forward in the circumferentially divided position, and each of the insertion pieces 17 a to 17 a is a slit formed in the flange portion 12 a of the cylinder 12 ( It protrudes further forward through (not shown).
[0009]
A cylindrical tool holder 20 is attached from the front side of the flange portion 12a, and a receiving member 21, an O-ring 22 and a guide member 23 are accommodated on the rear inner peripheral surface of the tool holder 20. These are each movable in the axial direction (left-right direction in the figure). A stepped stopper portion 23 a is formed on the outer peripheral surface of the guide member 23, and the insertion pieces 17 a to 17 a of the slide sleeve 17 are abutted against the stopper portion 23 a by the urging force of the compression spring 19. Yes. Accordingly, the receiving member 21, the O-ring 22 and the guide member 23 are retracted to the right in the figure against the compression spring 19, and are returned to the left in the figure by the compression spring 19.
In the tool holder 20, the meson 24 is accommodated so as to be movable in the axial direction. A bit 25 is inserted in front of the intermediate element 24, and the rear end face is hit by the intermediate element 24. The rear end surface of the intermediate element 24 is struck by the striker 13.
[0010]
The electric hammer 1 of this embodiment configured as described above operates as follows. When a switch (not shown) is turned on, the electric motor 2 is started, and the crank gear 3 is thereby rotated. Since a torsion spring 8 is interposed between the crank gear 3 and the intermediate rotator 7, the crank gear 3 and the intermediate rotator 7 rotate integrally within a torque range equal to or less than the biasing force of the torsion spring 8. To do. For this reason, the torsion spring 8 is in an extended state as shown in FIG.
When the intermediate rotating body 7 rotates in this way, the crank pin 7d moves on a certain circumference, so that the connecting rod 9 advances and retreats, whereby the piston 11 reciprocates in the cylinder 12.
On the other hand, when the bit 25 is pressed against the object to be struck, the bit 25 and the intermediate member 24 are retracted, and thereby the receiving member 21, the O-ring 22 and the guide member 23 are retracted. When the guide member 23 is retracted, the slide sleeve 17 is retracted against the compression spring 19. When the slide sleeve 17 moves backward, the air holes 12b to 12b formed in the cylinder 12 are closed, and the first air chamber 14a is almost sealed. However, the first air chamber 14a is ventilated with outside air through the auxiliary hole 12d, and the suction of the striker 13 when the piston 11 is retracted is suppressed.
When the piston 11 reciprocates in this sealed state, the striker 13 reciprocates due to the air spring action of the first air chamber 14a, and the rear end of the intermediate member 24 and thus the bit 25 is repeatedly struck. In the course of the stroke of the striker 13 toward the strike side, the air in the second air chamber 14b on the side opposite to the first air chamber 14a flows between the exhaust holes 12c to 12c and the insertion pieces 17a and 17a of the slide sleeve 17. It is discharged out of the cylinder 12 through the gap.
[0011]
Here, when the striker 13 strikes the intermediate piece 24, the striker 13 moves to the piston 11 side by the reaction force and the air spring action at the time of strike. On the other hand, the piston 11 moves again toward the striker 13 as the intermediate rotating body 7 rotates. At this time, the pressure in the first air chamber 14a is rapidly increased, and the reaction force is applied to the crank mechanism such as the piston pin 9b, the crank pin 7d, and the crank gear 3. However, the intermediate rotating body 7 having the crank pin 7d can rotate relative to the crank gear 3, and a torsion spring 8 is interposed between the two. Therefore, when a reaction force (rotational torque) that exceeds the biasing force of the torsion spring 8 is applied to the intermediate rotating body 7 via the crank pin 7d, the intermediate rotating body 7 resists the biasing force of the torsion spring 8. It rotates with respect to the crank gear 3. The torsion spring 8 at this time is contracted as shown in FIG.
Since the intermediate rotator 7 rotates with respect to the crank gear 3 in this manner, the reaction force transmitted through the piston 11 is alleviated, so that the reaction force is applied to the crank mechanism such as the piston pin 9b, the crank pin 7d and the crank gear 3. Transmission is reduced. Thereby, the durability of the crank mechanism and thus the electric hammer 1 can be enhanced, and the reaction force transmitted to the operator can be reduced.
[0012]
Next, although not included in the invention described in the claims, a specific configuration of the related art will be described with reference to FIGS. 4 and 5 . About the point similar to embodiment about invention of a claim, the description is abbreviate | omitted using a same code | symbol. First, in the electric hammer 1 according to the exemplary embodiment, intermediate rotor 7 is supported rotatably with respect to the crank gear 3 has illustrated a configuration in which a crank pin 7d in the intermediate rotor 7, in this related art In the electric hammer 30, the crank pin 31 is directly fixed to the upper surface of the crank gear 32. This is the same as the conventional configuration.
A rear end portion of the connecting rod 33 is connected to the crank pin 31 via a bearing 34 so as to be relatively rotatable. There is no need to change this point. On the other hand, a piston pin 34 is fixed to the front end portion of the connecting rod 33, and the piston 36 is connected to the piston pin 34 so as to be displaceable within a certain range in the stroke direction. This is a major feature of the related technology . That is, the intermediate connecting member 35 is attached to be able to swing in the lateral direction (direction orthogonal to the paper surface in the drawing) via the piston pin 34 fixed to the front end portion of the connecting rod 33.
[0013]
On the other hand, a circular recess 36a having a constant diameter is formed at a predetermined depth on the rear surface (right end surface in the figure) of the piston 36, and the intermediate connecting member 35 moves in the stroke direction of the piston 36 in the circular recess 36a. Contained as possible. However, since the compression spring 37 is interposed between the bottom surface 36c of the circular recess 36a and the intermediate connecting member 35, the piston 36 is urged in the striking direction.
Further, both end portions of the piston pin 34 protrude from the side surface of the intermediate connecting member 35, and the protruding portions are inserted into support holes 36 b and 36 b formed facing the wall portion of the piston 36. Both the support holes 36b, 36b are formed in a long slot shape that is long in the stroke direction of the piston 36. For this reason, the piston 36 can be displaced with respect to the intermediate connecting member 35 and the connecting rod 33 within a range in which both end portions of the piston pin 34 can move within the support holes 36 b and 36 b.
[0014]
According to the electric hammer 30 according to the related art configured as described above, when the striker 13 strikes the rear surface of the intermediate piece 24, the striker 13 moves to the piston 36 side by the reaction force and the air spring action at the time of strike. . On the other hand, the piston 36 moves again toward the striker 13 as the crank gear 32 rotates. At this time, the pressure in the first air chamber 14 a is rapidly increased, and the reaction force is applied to the piston 36. However, the piston 36 can be displaced in the stroke direction with respect to the connecting rod 33, and a compression spring 37 is interposed therebetween. For this reason, when the reaction force exceeds the urging force of the compression spring 37, the piston 36 is displaced in the stroke backward direction (rightward in the drawing) against the urging force of the compression spring 37. In this way, the reaction force is alleviated by the displacement of the piston 36 relative to the connecting rod 33. For this reason, a large reaction force is not applied to the connecting rod 33, which can increase the durability of the crank mechanism including the piston pin 34, the crank pin 31, the crank gear 32, and the like, and thus the electric hammer 30. The reaction force transmitted to the worker can be reduced.
[0015]
The embodiment and related technology described above can be implemented with various modifications. For example, although not shown, in the embodiment , a compression spring or a tension spring may be used instead of the torsion spring 8.
Moreover, although the electric hammers 1 and 30 are illustrated as the impact tools, the present invention can also be applied to other similar impact tools such as a hammer drill.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an internal structure of an electric hammer according to an embodiment of the present invention. This figure has shown the state at the time of the air compression which the piston advanced.
FIG. 2 is a longitudinal sectional view showing the internal structure of the electric hammer according to the embodiment , showing a state when the piston is retracted.
3 is a cross-sectional view taken along line (3)-(3) in FIG. 1, and (A) is a torsion spring at the time when the intermediate rotating body rotates against the torsion spring and the reaction force is relaxed. (B) shows the state of the torsion spring when no reaction force is received.
FIG. 4 is a longitudinal sectional view showing the internal structure of the electric hammer according to the related art . This figure shows a state at the time when the piston receives a reaction force by striking. Therefore, the piston is displaced to the right with respect to the piston pin, and the compression spring is contracted.
FIG. 5 is a longitudinal sectional view showing the internal structure of the electric hammer according to the related art , and shows a state when the piston is retracted. In this figure, no reaction force is applied to the piston. Therefore, the piston is displaced to the left with respect to the piston pin, and the compression spring extends.
[Explanation of symbols]
1 ... Electric hammer ( embodiment )
DESCRIPTION OF SYMBOLS 3 ... Crank gear, 3a ... Circular hole, 3b ... Projection 7 ... Intermediate | middle rotary body 7a ... Shaft part, 7b ... Flange part, 7c ... Projection, 7d ... Crank pin 8 ... Torsion spring 9 ... Connecting rod, 9b ... Piston pin 11 ... Piston 12 ... Cylinder 13 ... Batter 14a ... first air chamber, 14b ... second air chamber 15 ... barrel 17 ... slide sleeve 19 ... compression spring 20 ... tool holder 24 ... medium 25 ... bit 30 ... electric hammer ( related technology) )
31 ... Crank pin 32 ... Crank gear 33 ... Connecting rod 34 ... Piston pin 35 ... Intermediate connecting member 36 ... Piston, 36a ... Circular recess, 36b ... Support hole 37 ... Compression spring

Claims (1)

A striking tool that converts the rotational power of an electric motor into a reciprocating motion of a piston via a crank mechanism, and strikes the tip tool by a pneumatic spring action generated by the reciprocating motion of the piston,
The crank mechanism includes a crank gear that is rotated by the electric motor, an intermediate rotating body that is supported so as to be coaxially rotatable with respect to the crank gear, a crank pin that is eccentrically provided on the intermediate rotating body, the crank pin, It has a connecting rod that connects the pistons together,
The intermediate rotator is elastically urged with respect to the crank gear in the rotational direction, and the intermediate rotator is rotated relative to the crank gear against the elastic urge, and the air spring acts to A striking tool designed to relieve the reaction force applied through the piston .

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