Impact tool

1. An impact tool comprising:

a casing that supports a tip tool;

a moving member that is reciprocatably provided in the casing and generates impact force to be transmitted to the tip tool;

an electric motor that is provided in the casing and has an output shaft;

a motion converting mechanism that is provided in the casing, converts rotary motion of the output shaft to reciprocating motion, and transmits the reciprocating motion to the moving member; and

a vibration reducing mechanism that is movably provided in the casing and reduces a vibration of the casing,

wherein the vibration reducing mechanism includes:

a supporting member that is provided to be swingable in a direction of a center line of reciprocation of the moving member with using a fixing position provided on the casing as a supporting point; and

a weight that is attached to a location of the supporting member close to a free end relative to the fixing position, in a plane including the center line, a gravity center of the weight and the fixing position are disposed at mutually different locations in a radial direction of the center line, in the plane including the center line, the fixing position is disposed on a side of a gravity center of the impact tool relative to the center line, the supporting member has a hole penetrating therethrough in a direction along an axis of the output shaft, and the output shaft is inserted in the hole.

2. The impact tool according to claim 1 ,

wherein, in the plane including the center line, the gravity center of the impact tool is disposed between the fixing position and the gravity center of the weight, and in the plane including the center line, the center line is disposed between the gravity center of the weight and the gravity center of the impact tool.

3. The impact tool according to claim 1 ,

wherein the axis of the output shaft is disposed to be parallel to and non-coaxial with the center line.

4. The impact tool according to claim 1 ,

wherein the electric motor has a coil that forms a rotating magnetic field by distribution of electric power, the motion converting mechanism has a rotatable power transmitting shaft,

a first gear provided at the output shaft and a second gear provided at the power transmitting shaft mesh with each other, and the vibration reducing mechanism is disposed between the first gear and the coil in a direction along the axis of the output shaft.

5. The impact tool according to claim 1 , wherein the vibration reducing mechanism is disposed between the electric motor and the motion converting mechanism.

6. The impact tool according to claim 1 , further comprising:

a bearing that is provided in the casing and supports the output shaft,

wherein the bearing and the vibration reducing mechanism are disposed so as to be at least partially overlapped with each other in a direction along the center line of the moving member.

7. The impact tool according to claim 6 , wherein the vibration reducing mechanism includes:

a supporting member that is fixed to the casing in a cantilever state so as to be swingable in the direction along the center line; and

a weight attached to the free end of the supporting member.

8. The impact tool according to claim 7 ,

wherein the weight has a shape whose width from the supporting member serving as a center is larger on an opposite side of the electric motor.

9. The impact tool according to claim 8 , further comprising:

an intermediate shaft that transmits power of the output shaft to the tip tool,

wherein the weight is disposed on an opposite side of the intermediate shaft with interposing the output shaft therebetween.

10. The impact tool according to claim 6 ,

wherein the electric motor has a coil that forms a rotating magnetic field by distribution of electric power, the motion converting mechanism has a power transmitting shaft that is disposed to be parallel to the center line and is rotatable,

a first gear provided at the output shaft and a second gear provided at the power transmitting shaft mesh with each other,

the vibration reducing mechanism is disposed between the first gear and the coil in the direction along the center line,

the vibration reducing mechanism has a hole or a recessed part that is penetrating therethrough in the direction along the center line, and the output shaft is inserted in the hole or the recessed part.

11. The impact tool according to claim 6 ,

wherein the casing has a cylindrical part that is formed so as to surround an axis of the output shaft,

the output shaft is inserted in the cylindrical part, the bearing is attached to an inner peripheral surface of the cylindrical part and supports the output shaft, a hole that is penetrating through the vibration reducing mechanism in the direction along the center line is provided, and

the cylindrical part is inserted in the hole.

12. The impact tool according to claim 1 , wherein

the weight has a trapezoidal shape whose size in a swinging direction along the center line is reduced as increasing a distance from the fixing position.

13. The impact tool according to claim 12 ,

wherein the weight has a first end part that is provided at a location close to the fixing position relative to the free end of the supporting member and has a second end part that is provided at a location close to the free end of the supporting member compared with the first end part, the casing has a weight-opposing flat surface that is opposed to the end part of the weight in the swinging direction, and

when the swinging motion of the weight reaches a maximum amplitude, a distance from the first end part to the weight-opposing flat surface and a distance from the second end part to the weight-opposing flat surface are equal to each other in the direction along the center line.

14. The impact tool according to claim 13 ,

wherein an end part of the weight in the direction along the center line is provided with an opposing surface opposed to the casing, and

when the swinging motion of the weight reaches the maximum amplitude, the weight-opposing flat surface and the opposing surface become parallel to each other in a plane including the center line.

15. The impact tool according to claim 12 ,

wherein the casing includes:

an outer casing that constitutes an outer shell; and

an inner casing that is disposed in the outer casing, and

the weight is supported by a plate spring having one end part fixed to the inner casing.

16. The impact tool according to claim 12 ,

wherein an end part of the weight in the direction along the center line is provided with an opposing surface opposed to the casing, and

a distance from a center position of the weight to the opposing surface in the direction along the center line is reduced as being closer to the free end from the fixing position.