JP4581895B2 - Impact tool - Google Patents

Description

  The present invention relates to an improvement in performance of an impact tool that performs work such as impact crushing and drilling on a work material such as concrete.

  Many products have already been put into practical use for impact tools, but many proposals have been made regarding improvements. One viewpoint of improvement is improvement of a torque switching mechanism from a motor to a tip tool as described in Patent Document 1.

  Another improvement viewpoint is the dust collection method. That is, since a lot of dust is generated during drilling, a structure for collecting the dust is indispensable.

  Still another viewpoint is a holding method of the tip tool as described in Patent Document 2. As described above, the impact tool can perform different types of work by exchanging the tip tool. However, since the tool holding device for the tip tool requires operability and safety, many proposals have been made.

  Still another improvement viewpoint is an idle driving prevention mechanism as described in Patent Document 3. For example, it is a kind of slip mechanism for preventing a phenomenon that an impact tool is swung by a reaction force when a tip tool is locked when drilling concrete or the like.

  Many inventions have been proposed in this way, but the invention that has been aimed at extending the life or improving the impact performance by optimizing the part shape by focusing on the part shape of the impact mechanism of the impact tool has been proposed so far. Not proposed.

  An example of a conventional impact tool will be described with reference to FIGS.

  The drive shaft 8 fixed to the electric motor 9 is rotated by the rotation of the electric motor 9, and the crankshaft 5 to which the gear 6 is attached is rotated via the pinion 7 disposed at one end of the drive shaft 8. As the crankshaft 5 rotates, the piston 4 reciprocates in the cylinder 15 via a connecting rod 11 and a piston pin 12 attached to the crankshaft 5. By the reciprocation of the piston 4, the air chamber 19 constituted by the piston 4, the striker 3 and the cylinder 15 changes in air pressure, and the striker 3 reciprocates due to the change in air pressure. The striker 3 collides with an intermediate element 2 disposed in the tool holder 17 so as to be slidable in the cylinder axis direction, and the intermediate element 2 is further engaged with the tool holder 17 so as to be slidable in the cylinder axis direction. Collide with 16. Since the meson 2 is engaged with the tool holder 17 so as to be slidable in the axial direction, an O-ring groove 2a for engaging an O-ring is disposed on the outer surface of the meson 2, and the O-ring groove 2a The O-ring 31 is engaged.

  The O-ring 31 engaged with the intermediate element 2 plays a role for preventing leakage of a lubricant such as grease applied to each part in the impact tool main body.

  Further, the impact tool needs to be used by replacing the tip tool 16 with a large diameter or a small diameter according to the work contents. During the replacement work, the lower stopper 41 disposed on the tool holder 17 is in contact with the lower inclined portion 21a of the intermediate element 2 so that the intermediate element 2 does not fall out of the impact tool body. Further, the upper inclined portion 21b of the intermediate element 2 abuts against the damper washer 51 so that the intermediate element 2 cannot move in the direction of the striker 3 more than necessary during operation, and a stopper provided in the damper 52, the damper holder 53, and the cylinder 15 Movement is restricted via the ring 54.

  When performing such operations as impact crushing and drilling with such an impact tool, an impact load is generated inside the intermediate element 2 that has been hit by the impactor 3. Then, the impact load inside the meson 2 reaches the contact surface with the tip tool 16 and the striking of the meson 2 and the tip tool 16 starts. An impact load is generated inside the tip tool hit by the meson 2, the impact load reaches the tip of the tip tool, the tip is displaced in the direction of the work material (not shown), and the work material is hit. Then, the work material is crushed.

Utility Model Registration No. 2549578 JP-A-10-225879 JP 2001-179657 A

  The problems of the conventional impact tool will be described with reference to FIGS.

  When the striker 3 and the meson 2 collide, an impact load is generated from the collision surface of the striker 3 and the meson 2 toward the tip tool 16 through the inside of the meson 2, and the impact load is initially within the small diameter portion of the meson 3. When transmitted to the large diameter portion (FIG. 10a), it spreads to the outer shape side and is transmitted (FIG. 10b). Thereafter, the impact load passes through the bottom 2b of the O-ring groove 2a, and at that time, excessive impact stress concentration occurs on the bottom 2b (FIG. 10c).

  Further, the impact load is transmitted to the tip tool 16 from the collision surface between the intermediate piece 2 and the tip tool 16, and the reaction force from the tip tool 16 is again transmitted as an impact load in the direction of the striker 3 in the intermediate piece 2. At this time, the impact load again passes through the bottom 2b of the O-ring groove 2a (FIG. 10d). Since the O-ring groove 2a is usually formed in accordance with the dimensions of the O-ring 31, the bottom 2b of the O-ring groove has a shape with a large curvature and stress concentration.

  If the impact stress generated by the impact of the striker 3, the meson 2, and the tip tool 16 and propagated inside the meson 2 exceeds the material strength of the meson 2, the meson 2 is damaged, and the reliability of the product Result. However, if the impact energy of the striker 3 is set low so that the impact stress does not exceed the material strength of the meson 2, an impact tool with low work performance is obtained.

  In particular, recently, a small and high-power impact tool has been desired in the market, and since the kinetic energy of the striker 3 is set to be large, the problem of damage to the meson 2 has become serious.

  An object of the present invention is to solve the above-mentioned problems, and to provide an impact tool having high work performance and a long life.

The object is to have a depth substantially equal to the O-ring groove on one or both sides in the meson axis direction of the O-ring groove of the meson, a width larger than the O-ring groove, and the curvature of the groove bottom surface. Is achieved by disposing a groove smaller than the curvature of the largest curvature portion of the O-ring groove.

  According to the present invention, in the impact tool that performs the destruction work of the work material such as concrete with the tip tool, since the groove is disposed on one or both sides of the O-ring groove of the meson, the impact on the bottom surface of the O-ring groove. The stress can be reduced. This makes it possible to improve the reliability of the meson without reducing the hitting performance. Furthermore, the disposed grooves can hold the lubricant, prevent galling and wear between the meson and the cylinder, and provide a more reliable impact tool.

<First Embodiment>
An impact tool according to a first embodiment of the present invention will be described with reference to FIGS. The structures other than those described below are the same as those of the conventional impact tool shown in FIGS.

The impact tool meson 2 includes a small-diameter portion on the piston 4 side and a large-diameter portion on the tip tool 16 side, and an O-ring groove 2a is disposed in the large-diameter portion. The large diameter portion of the intermediate element 2 on the striker 3 side has a depth substantially equal to that of the O-ring groove 2a, a width larger than that of the O-ring groove 2a, and the curvature of the groove bottom surface is an O-ring groove. An upper groove 2c having a bottom surface portion 2d smaller than the curvature of the largest curvature portion 2a is provided.

  According to the present embodiment, as shown in FIG. 3, the impact load propagating from the collision surface of the striker 3 and the intermediate element 2 toward the tip tool 16 in the intermediate element 2 is caused to flow by the upper groove 2c. The impact load that is changed in the axial direction of the meson 2 and propagates to the O-ring groove 2a is reduced. As a result, the impact stress of the O-ring groove 2a is very low compared to the state without the upper groove 2c. By providing the upper groove 2c, impact stress is also generated on the bottom surface portion 2d of the upper groove 2c. However, since the curvature of the bottom surface portion 2d of the upper groove 2c is reduced, the impact stress is reduced to the O-ring groove. The size can be equivalent to 2a.

FIG. 4 shows the relationship between the depth of the upper groove 2c and the stress of each groove. In FIG. 4, the stress of the O-ring groove 2a when the upper groove 2c is not present is set to 1. Thus, the stress of the O-ring groove 2a is reduced by disposing the upper groove 2c, and the ratio of the depth of the upper groove 2c to the depth of the O-ring groove 2a is A, and when A is substantially equal (optimally 1.1), the stresses in both grooves are almost equal, and the stress balance is improved.
<Second Embodiment>
An impact tool according to a second embodiment of the present invention will be described with reference to FIGS.

The present embodiment is different from the first embodiment in that the bottom surface portion 2f of the O-ring groove 2a has a curvature of the groove bottom surface that is smaller than the curvature of the largest curvature portion of the O-ring groove 2a. The lower groove 2e having

According to the present embodiment, the effect of reducing the impact load propagating from the collision surface of the striker 3 and the meson 2 through the inside of the meson 2 toward the tip tool 16 is the same as that of the first embodiment (FIG. 6a). . However, the stress can be further reduced by the effect of the lower groove 2e. The impact load propagating in the direction of the striker 3 by the impact of the tip tool 16 and the intermediate piece 2 is changed in the axial direction of the intermediate piece 2 by the lower groove 2e, and the O-ring groove 2a The impact load that propagates to the bottom surface 2b is reduced. As a result, the concentration of impact stress on the bottom surface 2b is reduced (FIG. 6b). The impact stress of the bottom surface portion 2f of the lower groove 2e is equal to the impact stress of the bottom surface portion 2b because the curvature of the bottom surface portion 2f is smaller than the curvature of the largest curvature portion of the O-ring groove 2a. The value is smaller than that in the state without the lower groove 2e.

  FIG. 7 shows the relationship between the depth of the lower groove 2e and the stress of each groove. FIG. 7 shows a case where the stress A of the O-ring groove 2a without the upper groove 2c is 1, and the ratio A of the depth of the upper groove 2c to the depth of the O-ring groove 2a is 1.1. .

  Thus, by arranging the lower groove 2e in the meson 2, both the stress of the upper groove 2c and the stress of the O-ring groove 2a are reduced.

  Furthermore, the upper groove 2c and the lower groove 2e disposed in the meson 2 also have an effect of retaining a lubricant, and it becomes possible to prevent galling and wear between the meson 2 and the cylinder 15. Thereby, a more reliable impact tool can be provided.

1 is an overall structural cross-sectional view showing an impact tool according to a first embodiment of the present invention; External view showing only the meson of FIG. Schematic diagram showing how stress waves propagate inside the meson of FIG. Graph showing the relationship between upper groove depth and stress in the meson of FIG. FIG. 3 is an external view showing a meson according to a second embodiment of the present invention. Schematic diagram showing how stress waves propagate inside the meson of FIG. FIG. 5 is a graph showing the relationship between the lower groove depth and stress in the meson of FIG. Cross-sectional view of the entire structure showing a conventional impact tool External view showing only the meson of FIG. Schematic diagram showing how stress waves propagate inside the meson shown in FIG.

Explanation of symbols

2 Meson 2a O-ring groove 2b O-ring groove bottom surface 2c Upper groove 2d Upper groove bottom surface 2e Lower groove 2f Lower groove bottom surface 3 Strike 4 Piston 5 Crankshaft 6 Gear 7 Pinion 8 Drive shaft 9 Electric motor 11 Connection Rod 12 Piston pin 15 Cylinder 16 Tip tool 17 Tool holder 19 Air chamber 31 O-ring 41 Lower stopper 51 Damper washer 52 Damper 53 Damper holder 54 Stopper ring

Claims (1)

A piston disposed in a cylinder disposed in the main body housing, a striking element slidably reciprocating in the cylinder, and disposed between the striking element and a tip tool, An impact tool that is configured to impact the tip tool through the intermediate member by reciprocating movement of the striker,
One or both sides of the O-ring groove formed in the intermediate element in the cylinder axial direction has a depth substantially equal to that of the O-ring groove, a width larger than the O-ring groove, and a groove bottom surface. An impact tool characterized by having a groove whose curvature is smaller than the curvature of the largest curvature portion of the O-ring groove.