JP4341602B2 - Impact tool - Google Patents

Description

  The present invention relates to a reduction in vibration of an impact tool that is driven by an electric motor and performs operations such as impact crushing.

  Impact tools that perform work such as impact crushing have large vibrations and noise during work, causing various diseases due to vibration transmission to the human body, noise pollution to workers and surroundings, fatigue breakdown of various parts due to vibration, etc. . As a countermeasure for such a problem, for example, a vibration isolating member such as rubber is disposed between the grasping portion and the main body to reduce vibration transmission to the operator. As another countermeasure example, there is an example in which a damper is disposed in the reciprocating direction of the intermediate element or the tip tool so as to buffer the impact in the reciprocating direction.

  The basic operation of the impact tool and the outline of the prior art will be described below with reference to FIG. 4 showing a sectional view of the conventional impact tool.

  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 a pinion 7 disposed at one end of the drive shaft 8. To do. The rotation of the crankshaft 5 causes the piston 4 to reciprocate in the cylinder 15 via the connecting rod 11 and the piston pin 12 attached to the crankshaft 5. As the piston 4 reciprocates, the air chamber 19 constituted by the piston 4, the striker 3, and the cylinder 15 fluctuates in air pressure, and the striking member 3 reciprocates due to the air pressure fluctuation.

  On the other hand, the rotation of the electric motor 9 is transmitted to the shaft 22 via the second gear 20 and the third gear 21. Further, the second pinion 23 disposed at the tip of the shaft 22 rotates the cylinder rotating gear 24 meshed with the second pinion 23. The cylinder 15 is fixed to a cylinder rotating gear 24 via a key 25, and the cylinder 15 is connected to a tool holder (not shown) that holds the tip tool 16 at the lower portion thereof, so that the tip tool 16 rotates. To do.

  The striking element 3 collides with the intermediate element 2 disposed in the cylinder 15, and further, the intermediate element 2 collides with the tip tool 16, and the tip tool 16 rotates and the work material such as concrete is crushed. Etc.

  In the impact tool described above, the piston 4 receives a load due to air pressure fluctuation in the air chamber 19 and is transmitted to the housing 10 and the handle 17 via the piston pin 12, the connecting rod 11, and the crankshaft 5. When an operator performs a concrete crushing operation, the operator grips the handle 17 attached to the housing 10 to perform the operation, and thus is directly affected by fluctuations in air pressure. This air pressure fluctuation causes vibration.

  As a conventional measure for reducing the above-described vibration, for example, a vibration isolating member is disposed between the handle 17 and the housing 10 to which the grasping portion 17 is attached to reduce the transmission of vibration to the handle 17. Yes.

  In addition, there are one provided with a dynamic vibration absorber instead of the vibration isolating member (Patent Document 1) and one provided with a balancer (Patent Document 2).

Japanese Patent Publication No.58-24235 Japanese Utility Model Publication No. 58-31653

  In the case of the above-described prior art, it is possible to reduce vibration of the handle 17 by, for example, isolating the handle 17 with the vibration isolating member. However, in normal work, the operator holds the handle 17 with one hand. In many cases, the other hand holds a side handle (not shown) attached in the vicinity of the main body cylinder case 13 or directly grips the main body to perform the work, and the vibration of the main body is directly transmitted to the operator.

  An object of the present invention is to reduce the vibration of the entire product.

To achieve the above object, the present invention provides an electric motor, a drive shaft that is rotationally driven by the electric motor, a crankshaft that transmits the rotational power of the drive shaft through a gear mechanism, and an inner side of a cylindrical member. A piston capable of reciprocating, a first mechanism for converting rotation of the crankshaft into reciprocating motion of the piston via a connecting rod connected to the crankshaft, and the cylindrical member by reciprocating motion of the piston An impact tool that strikes a tip tool mounted on a tool holder in front of the striker and connected to the crankshaft. A second mechanism for converting the rotation of the crankshaft into a reciprocating motion and reciprocating the cylindrical member, and the piston is reciprocated by the first mechanism. Causes the movement, it has one feature in by the second mechanism that so as to reciprocate by shifting the movement of the piston of the cylindrical member.
When the piston is positioned between the top dead center located closest to the tip tool and the bottom dead center located closest to the tip tool, the cylindrical member is moved toward the tip tool. It has other features in doing so.

  According to the present invention, the vibration is reduced by moving the cylinder in the direction opposite to the load that the piston receives from the air in the middle of the transition from the top dead center to the bottom dead center of the piston in which the pressure of the air chamber becomes maximum. Thus, an impact tool having low vibration can be provided.

  Details of the invention will be described below with reference to FIG. 1 which is a cross-sectional view of an impact tool showing an embodiment of the present invention and FIG. 2 which is an enlarged view of the main part of FIG.

  The rotation of the electric motor 9 is converted into the reciprocating motion of the piston 4, and the air chamber 19 constituted by the piston 4, the striker 3 and the cylinder 15 fluctuates in air pressure, and the striking member 3 reciprocates due to the air pressure fluctuation. At this time, due to the pressure fluctuation of the air chamber 19, the piston 4 is loaded upward in the figure with a size of pressure × cross-sectional area. This load is transmitted to the housing 10 via the piston pin 12, the connecting rod 11, and the crankshaft 5, and acts to lift the impact tool toward the operator. This load causes vibration.

  The pressure in the air chamber 19 is maximized when the piston 4 reaches a substantially intermediate point where the piston 4 moves from the bottom dead center to the top dead center. The top dead center is when the piston 4 is located closest to the tip tool, and the bottom dead center is when the piston 4 is located closest to the tip end tool.

  On the other hand, the cylinder 15 is rotated by the electric motor 9 via the cylinder rotating gear 24. The cylinder rotating gear 24 is connected to the cylinder 15 with a key 25 and is connected so as not to slip in the rotational direction, but is held so as to be slidable in the axial direction.

  The cylinder 15 is provided with a flange 27. One of the flanges 27 is supported by an elastic body 28 supported by the housing 10, and the other is connected to a cylinder driving cam 26 disposed on the crankshaft 5. It is pressed. Accordingly, the cylinder 15 reciprocates according to the shape of the cylinder driving cam 26 as the crankshaft 5 rotates.

  The shape of the cam 26 for driving the cylinder, that is, the lift characteristic, is that the cylinder 15 moves in the direction of the tip tool 16 when the piston 4 reaches a substantially intermediate point where the bottom dead center moves to the top dead center, and the elastic body 28 is compressed most. It is set to be. The compressed elastic body 28 has a function of accelerating the cylinder 15 in the direction of the handle 17 and accelerating the housing 10 in the direction of the tip tool 16. At this time, a load is applied to the housing 10 from the elastic body 28 toward the tip tool 16. The load from the elastic body 28 to the housing 10 is opposite to the load due to the compressed air in the air chamber 19. At this time, there are two types of loads acting on the impact tool: a load in the worker direction due to the compressed air in the air chamber 19 and a load that the cylinder 15 presses in the direction of the tip tool 16 via the elastic body 28. Accordingly, both loads cancel each other, and the vibration of the housing 10 and the handle 17 is reduced.

Sectional drawing of the impact tool which showed one Example of the vibration isolator of the impact tool which becomes this invention 1 is an enlarged partial cross-sectional view of the main part of FIG. Perspective view of cylinder rotation gear Sectional drawing which shows an example of the conventional impact tool

Explanation of symbols

2 is an intermediate element, 3 is a striker, 4 is a piston, 5 is a crankshaft, 6 is a gear, 7 is a pinion, 8 is a drive shaft, 9 is an electric motor, 10 is a housing, 11 is a connecting rod, 12 is a piston pin,
13 is a cylinder case, 15 is a cylinder, 16 is a tip tool, 17 is a handle, 19 is an air chamber, 20 is a second gear, 21 is a third gear, 22 is a shaft, 23 is a second pinion, 2
4 is a cylinder rotation gear, 25 is a key, 26 is a cylinder drive cam, 27 is a flange, 2
8 is an elastic body, and 29 is a cylinder upper end surface.

Claims (2)

An electric motor,
A drive shaft that is rotationally driven by the electric motor;
A crankshaft that transmits the rotational power of the drive shaft via a gear mechanism;
A piston capable of reciprocating inside the cylindrical member;
A first mechanism that converts rotation of the crankshaft into reciprocating motion of the piston via a connecting rod connected to the crankshaft;
A striking element that reciprocates inside the cylindrical member due to air pressure fluctuation in the inner space of the cylindrical member due to reciprocating movement of the piston,
In the impact tool that strikes the tip tool mounted on the tool holder in front of the striker,
A second mechanism that is coupled to the crankshaft, converts rotation of the crankshaft into reciprocating motion, and reciprocates the cylindrical member;
An impact tool characterized in that the piston is reciprocated by the first mechanism, and the cylindrical member is reciprocated by the second mechanism, shifted from the movement of the piston. 2. The cylindrical member according to claim 1, wherein when the piston is located in the middle between a top dead center located closest to the tip tool side and a bottom dead center located closest to the tip end tool, the cylindrical member is An impact tool characterized by being moved in the direction.

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