JP2003071736A - Impact tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impact too preventing vibration and damage even in quickly performing heavy load work. SOLUTION: The impact tool 1 is provided with a hammer 4 engaging with a drive shaft 3 and rotating together with the drive shaft 3 and an anvil 6 meshing with the hammer 4 and rotating together with the hammer 4, is provided with a drive shaft cam groove 3a on the drive shaft 3, a hammer cam groove 4a on the hammer and a steel ball 5 engaging with the drive shaft cam groove 3a and the hammer cam groove 4a respectively as mechanisms for converting the rotating motion of the drive shaft 3 to the retreating motion of the hammer 4 when a load of fixed value of more acts on the anvil 6, is provided with a spring 7 making the hammer 4 mesh with the anvil 6 again with an impact after engagement of the hammer 4 and the anvil 6 is released due to retreat of the hammer 4, and having a housing 2 covering the components mentioned above. In this tool 1, an elastic body 9 regulating retreat of the hammer 4 is provided on an inner surface of the housing 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact tool, and more particularly to a technique for preventing vibration and damage that occur when a hammer receives a large reaction force.

[0002]

2. Description of the Related Art An impact tool 1 is a tool used when tightening or loosening screws, and when a load of a certain amount or more is applied, it produces a stronger torque by striking it. Is. As a configuration for giving the above function, as shown in FIG. 16 and FIG. 17, a substantially annular hammer 4 is attached to a drive shaft 3 which is rotated by a motor 8 inside a housing 2 forming an outer shell of the impact tool 1. The drive shaft 3 is slidably fitted and provided.
Is provided with a drive shaft cam groove 3a in a substantially V shape, and the hammer 4 is provided with a hammer cam groove 4a in the axial direction. A substantially V-shaped central portion which is a front end portion of the drive shaft cam groove 3a, and
The rotational motion of the drive shaft 3 is transmitted to the hammer 4 via the steel ball 5 fitted so as to be sandwiched between the rear ends of the hammer cam grooves 4a, and the rotational motion is further transmitted to the anvil 6 meshed with the hammer 4. Transmitted. Here, in the front-back direction, the side where the anvil 6 is located in the axial direction of the drive shaft 3 is the front side, and the opposite side is the rear side. When a certain amount of load or more is generated on the anvil 6 during the work and the rotation is slowed, the steel ball 5 and the drive shaft cam groove 3a are located at substantially the center of the drive shaft cam groove 3a at the fitting portion. A component force that pushes down the steel ball 5 along either groove direction of the V-shaped drive shaft cam groove 3a is generated. Here, which of the drive shaft cam grooves 3a is along depends on the rotation direction of the rotation shaft.

As shown in FIG. 18, the hammer 4 retreats on the drive shaft 3 in conjunction with the depression of the steel ball 5, whereby the hammer 4 and the anvil 6 are disengaged from each other. At this time, the hammer 4 is in the state of performing the rotational movement, while the anvil 6 is in the state of stopping the rotational movement. A coiled spring 7 is arranged behind the hammer 4, and the hammer 4 is pushed back by the urging force of the spring 7 and meshes with the anvil 6 again, but at that time, with respect to the stopped anvil 6, The hammer 4 gives a blow by its own rotation. The hammer 4, which receives a reaction force due to the impact at the time of impact, retreats again while rotating in the direction opposite to the rotation direction of the drive shaft 3, but the urging force of the spring 7 and the drive shaft 3
This rotation and retreat are damped by the rotational force of the, and the operation moves to the next striking operation.

In this way, when a certain load or more is generated during the work such as screw tightening, the striking by the anvil 6 can be repeated to generate a stronger torque.

[0005]

However, when the above-described conventional impact tool 1 is used, the reaction force received by the hammer 4 becomes large when it is necessary to perform high-load work more quickly. There is a case where the hammer 4 is retracted until the spring 7 is brought into a substantially close contact state as shown in FIG. 18 without sufficient damping. In this case, the steel balls 5 are sandwiched between the drive shaft cam groove 3a and the hammer cam groove 4a and collide with each other, resulting in increased vibration and damage to parts.

The present invention has been made in view of the above points, and can be used comfortably without worrying about occurrence of vibration or damage even when high-load work needs to be performed quickly. It is an object to provide an impact tool.

[0007]

In order to solve the above problems, the present invention provides a hammer that slidably fits on a drive shaft to rotate together, and an anvil that meshes with the hammer to rotate together. As a mechanism for converting the rotational movement of the drive shaft into the backward movement of the hammer when a load of a certain amount or more occurs on the anvil, the drive shaft cam groove is the drive shaft, the hammer cam groove is the hammer, A steel ball is fitted into the drive shaft cam groove and the hammer cam groove, respectively, and the hammer is given a biasing force that causes the hammer and the anvil to disengage from each other after the hammer retreats and then strikes again to engage with the anvil. In the impact tool including a spring that covers each member with a housing, an elastic body that restricts the backward movement of the hammer is provided on the inner surface of the housing. The assumed that the features. By doing so, the elastic body has a cushioning property to stop the retreat of the hammer before the steel ball is hit by being sandwiched between the drive shaft cam groove and the hammer cam groove, so that the increase in vibration and component The damage of is prevented.

Also, ribs are provided so as to project from the inner surface of the housing,
It is also preferable that the rib is provided with an elastic body, and by doing so, the elastic body sandwiched between the rib and the hammer has cushioning properties and stops the retreat of the hammer, so that increase in vibration and damage to parts etc. To be prevented.

Further, it is also preferable to fix the rib and the elastic body by adhesion, and by doing so, the elastic body can be easily positioned only by adhering to the rib.

It is also preferable that the rib is provided with an elastic body by fitting the recess formed in the elastic body with the rib. By doing so, the elastic body can be easily positioned by simply fitting the rib into the rib. Done.

It is also preferable that the rib is provided with the elastic body by press-fitting the rib into the recess formed in the elastic body. By doing so, the positioning of the elastic body is facilitated and
Definitely done.

It is also preferable to provide a thrust plate on the hammer-side surface of the elastic body. By doing so, direct contact between the elastic body and the hammer can be avoided, so that abrasion and damage of the elastic body are prevented. It

It is also preferable that the thrust plate is provided so as to protrude from the elastic body in the center direction of the housing, and by doing so, the elastic body sandwiched between the rib and the thrust plate and deformed by pressing is the thrust plate. Contact with corners and damage is prevented.

Further, a hook portion is extended from the thrust plate,
It is also preferable to hook and hook the hook portion to a rib provided with an elastic body and protruding from the inner surface of the housing. By doing so, positioning of the thrust plate becomes easy,
Deformation and rattling of the thrust plate is prevented.

Further, it is also preferable to provide a clearance between the hook portion for hooking the rib on the hook portion, the rib and the elastic body.
It becomes easy to assemble the thrust plate and the elastic body into the housing.

Further, it is also preferable that the hook portion of the thrust plate is provided at a position for restricting the movement of the elastic body toward the center of the housing. Since the fall and deformation of the elastic body are prevented, the load received from the hammer can be substantially evenly received by the entire elastic body. Therefore, the effect obtained by disposing the elastic body is further exhibited, and the elastic body is not damaged. To be prevented.

It is also preferable that a through hole is formed in the elastic body, and a locking portion that is locked to the through hole by fitting is provided so as to project from the thrust plate. The elastic body can be easily fixed.

It is also preferable that the elastic body is rotatably provided around the drive shaft. By doing so, the elastic body itself rotates when receiving a force in the rotational direction from the hammer. Twisting is prevented.

It is also preferable to interpose a sliding agent between the rib and the elastic body. By doing so, the friction between the rib and the elastic body is reduced, and the hammer receives a force in the rotational direction. In this case, the elastic body rotates more smoothly, so that the elastic body is more reliably prevented from being twisted.

It is also preferable to interpose a thrust bearing between the rib and the elastic body. By doing so,
The friction between the ribs and the elastic body is reduced, and the elastic body rotates more smoothly when receiving a force in the rotational direction from the hammer, so that the elastic body is more reliably prevented from being twisted.

It is also preferable to provide the elastic body integrally with the housing. By doing so, it is not necessary to separately provide the elastic body, so that the cost can be reduced and the assemblability can be improved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the embodiments shown in the accompanying drawings. The impact tool 1 of the present invention has a function of generating a stronger torque by hitting when a certain load or more is generated when tightening or loosening the screws. Since the structure for providing is already described in the description of the prior art, the description thereof is omitted, and the structure for restricting the retreat of the hammer 4 which is a characteristic structure of the present invention will be described below. However, similarly to the description of the conventional technique, the side on which the anvil 6 is located in the axial direction of the drive shaft 3 is the front side, and the opposite side, the side on which the motor 8 is located, is the rear side.

First, the impact tool 1 of the first example in the embodiment of the present invention will be described with reference to FIG. In the initial state where the hammer 4 and the anvil 6 are engaged with each other, an annular elastic member 9 made of, for example, rubber is provided at a position rearwardly separated from the rear end of the hammer 4 by an appropriate distance.
Are integrally provided on the inner surface of the housing 2. As a result, when the hammer 4 retreats significantly along the drive shaft cam groove 3a, the rear end surface of the hammer 4 contacts the front surface of the elastic body 9 and the restoring force of the elastic body 9 causes the hammer 4 to have a cushioning property. In preparation, the retreat is restricted. Therefore,
Even when the hammer 4 receives a large reaction force when colliding with the anvil 6 during high-load work such as bolt tightening, the steel ball 5 collides with the driving shaft cam groove 3a and the hammer cam groove 4a. The hammer 4 is locked by the elastic body 9 to stop the retreat before the occurrence of the, and shifts to the next striking operation.

In the present embodiment, the elastic body 9 is provided on the inner surface of the housing 2 as described above, but a gear box (not shown) for accommodating each member such as the drive shaft 3 and the hammer 4 is provided in the housing 2. If it is, the same elastic body 9 may be provided on the inner surface of the gear box.

Next, a second example impact tool 1 according to the embodiment of the present invention will be described with reference to FIG. In the initial state where the hammer 4 and the anvil 6 are meshed with each other, at a position rearwardly separated from the rear end portion of the hammer 4 by an appropriate distance, an annular rib 1 is projected from the inner surface of the housing 2.
0, and the annular elastic body 9 is provided on the front surface of the rib 10.
It is equipped with adhesively fixed. As a result, when the hammer 4 retreats significantly along the drive shaft cam groove 3a, the rear end surface of the hammer 4 abuts the front surface of the elastic body 9 and the elastic body sandwiched between the rib 10 and the hammer 4 is formed. By the restoring force of 9, the hammer 4 has a cushioning property and its retreat is restricted. Therefore, even when the hammer 4 receives a large reaction force when colliding with the anvil 6 during high-load work such as bolt tightening, the steel ball 5 is sandwiched between the drive shaft cam groove 3a and the hammer cam groove 4a. Before the collision occurs, the hammer 4 is locked by the elastic body 9 adhered and fixed to the rib 10 to stop the retreat, and shifts to the next striking operation.

In this example, the rib 10 is provided so as to project from the inner surface of the housing 2 as described above.
If a gearbox (not shown) for accommodating each member such as the drive shaft 3 and the hammer 4 is provided therein, the same rib 10 may be provided on the inner surface of the gearbox.

Next, the impact tool 1 of the third example in the embodiment of the present invention will be described with reference to FIG. 3, but this example has a configuration similar to that of the second example described above. Therefore, the description of the common configuration will be omitted. As a characteristic configuration of this example different from the above-mentioned second example, a concave portion 9a is formed on the entire outer peripheral surface of the annular elastic body 9 and a rib 10 protruding from the inner surface of the housing 2 is formed.
Is press-fitted into the recess 9a. With the above configuration, the elastic body 9 can be easily attached to the rib 10.

Next, the impact tool 1 of the fourth example in the embodiment of the present invention will be described with reference to FIG. The impact tool 1 of this example has substantially the same configuration as that of the second example described above, and a description of the common configuration will be omitted. However, in this example, the annular thrust plate 11 is provided on the front surface of the elastic body 9. The characteristic configuration is that it has. As a result, the elastic body 9 does not come into direct contact with the hammer 4, and the life of the elastic body 9 is extended. Further, the thrust plate 11 may be provided in the impact tool 1 of the first and third examples described above.

Next, the impact tool 1 of the fifth example in the embodiment of the present invention will be described with reference to FIG. The impact tool 1 of this example has substantially the same configuration as that of the above-described fourth example, and therefore a description of the common configuration is omitted, but in this example, the elastic body 9 and the thrust plate 11 are respectively The outer diameters are substantially the same, and the inner diameter of the thrust plate 11 is smaller than the inner diameter of the elastic body 9, which is a characteristic configuration different from the fourth example. As a result, the thrust plate 11 has a shape such that the inner peripheral side thereof protrudes toward the center of the housing 2 more than the elastic body 9 when assembled, so that the elastic body 9 is pressed between the rib 10 and the thrust plate 11 when the hammer 4 retracts. When deformed,
It is prevented that the elastic body 9 comes into contact with the corner of the thrust plate 11 and is damaged.

Next, the impact tool 1 of the sixth example in the embodiment of the present invention will be described with reference to FIGS. 6 to 10. Since the impact tool 1 of this example has substantially the same configuration as that of the above-described fourth example, the description of the common configuration will be omitted, but in this example, there is elasticity between the rib 10 and the thrust plate 11. Hook part 1 for holding the body 9
A plurality of 2 provided by extending from the inner peripheral surface of the thrust plate 11 has a characteristic configuration different from that of the fourth example described above. The hook portion 12 is a support portion 12b extending rearward from the inner peripheral surface of the thrust plate 11 by a predetermined length L.
And a cross section L formed by a hooking portion 12a extending from the rear end of the supporting portion 12b to the inner surface of the housing 2.
It is a character-shaped member.

The hooking portion 12a is a member for locking the rear surface of the rib 10 by hooking. The supporting portion 12b supports the hooking portion 12a, and the elastic body 9 moves toward the center of the housing 2. This is a member for restricting movement and deformation. For example, when the hook portion 12 is not provided, as shown in FIG. 10A, the elastic body 9 is deformed by the rearward load F, but the support portion 12b of the hook portion 12 is placed at an appropriate position. When provided, the support portion 12b prevents the elastic body 9 from being deformed or collapsed even if a load F is applied, as shown in FIG. 10 (b).

Further, the predetermined length L of the hook portion 12 is
By setting the length such that an appropriate clearance is generated between the hooking portion 12a of the hook portion 12, the rib 10 and the elastic body 9, the elastic body 9 and the thrust plate 11 can be easily assembled into the housing 2. can do.

Next, the impact tool 1 of the seventh example in the embodiment of the present invention will be described with reference to FIGS. 11 and 12. Since the impact tool 1 of this example has a configuration substantially similar to that of the above-described fourth example, a description of the common configuration will be omitted, but in this example, a through hole that penetrates the elastic body 9 in the front-rear direction is formed. 13 are formed at a plurality of positions, and a plurality of nail-shaped locking portions 14 with a bulging tip end are provided on the thrust plate 11 so as to project rearward, and the locking portions 14 are locked to the through holes 13 by fitting. This is a characteristic configuration different from the above-mentioned fourth example. As a result, the thrust plate 11 and the elastic body 9 can be easily fixed.

Next, the impact tool 1 of the eighth example in the embodiment of the present invention will be described with reference to FIG. Since the impact tool 1 of this example has substantially the same configuration as the second example described above, a description of the common configuration will be omitted, but in this example, sliding between the elastic body 9 and the rib 10 is performed. With the agent 15 interposed, the elastic body 9 is
A characteristic constitution different from the above-mentioned second example is that the outer peripheral surface of the elastic body 9 and the inner surface of the housing 2 are rotatably provided while sliding. As a result, when the elastic body 9 receives a force in the rotational direction due to the collision with the hammer 4 that retracts while rotating, the elastic body 9 smoothly rotates via the sliding agent 15. This prevents the elastic body 9 from being twisted.

Next, the impact tool 1 of the ninth example in the embodiment of the present invention will be described with reference to FIGS. 14 and 15. Since the impact tool 1 of this example has substantially the same configuration as the eighth example described above, the description of the common configuration will be omitted. In this example, the elastic body 9 is rotatably provided while sliding the outer peripheral surface of the elastic body 9 and the inner surface of the housing 2, and a bearing as a thrust bearing is provided between the elastic body 9 and the rib 10. The provision of 16 is a characteristic configuration different from the eighth example described above. Further, a convex portion 9a is formed on the outer peripheral surface of the elastic body 9, and the convex portion 9a is rotatably fitted to the concave portion 2a on the inner surface of the housing 2 to restrict the movement of the elastic body 9 in the axial direction. As a result, when the elastic body 9 receives a force in the rotational direction due to the collision with the hammer 4 that retracts while rotating, the elastic body 9 smoothly rotates via the bearing 16, and thus the elastic body 9 is twisted. Is prevented from occurring.

[0036]

As described above, according to the first aspect of the invention, the elastic body has a cushioning property before the steel ball is collided by being sandwiched between the drive shaft cam groove and the hammer cam groove. Since the hammer is stopped from moving backward, there is an effect that an increase in vibration and damage to parts are prevented.

Further, in the invention described in claim 2,
In addition to the effect of the invention described in claim 1, since the elastic body sandwiched between the rib and the hammer has a cushioning property to stop the retreat of the hammer, an increase in vibration and damage to parts are prevented. There is.

Further, in the invention according to claim 3,
In addition to the effect of the invention described in claim 2, there is an effect that the elastic body can be easily positioned only by adhering it to the rib.

Further, in the invention described in claim 4,
In addition to the effect of the invention described in claim 2, there is an effect that the elastic body can be easily positioned only by fitting it to the rib.

Further, in the invention according to claim 5,
In addition to the effect of the invention described in claim 4, there is an effect that the elastic body can be positioned easily and surely.

Further, in the invention according to claim 6,
In addition to the effects of the invention according to any one of claims 1 to 5,
Since the elastic body and the hammer do not come into direct contact with each other, the elastic body is prevented from being worn or damaged.

Further, in the invention according to claim 7,
In addition to the effect of the sixth aspect of the invention, there is an effect that the elastic body sandwiched between the rib and the thrust plate and deformed by pressing is prevented from coming into contact with the corner of the thrust plate and being damaged.

Further, in the invention described in claim 8,
In addition to the effect of the invention described in claim 6, there is an effect that the thrust plate can be easily positioned and deformation and rattling of the thrust plate can be prevented.

In the invention described in claim 9,
In addition to the effect of the invention described in claim 8, there is an effect that the thrust plate and the elastic body can be easily assembled in the housing.

Further, in the invention described in claim 10, in addition to the effect of the invention described in claim 8 or 9, contact with the hook portion prevents the elastic body from falling or deforming inward. As a result, the load received from the hammer can be substantially evenly received by the entire elastic body, so that the effect obtained by disposing the elastic body is further exerted and the elastic body is prevented from being damaged. .

Further, in the invention described in claim 11, in addition to the effect of the invention described in claim 6, there is an effect that the thrust plate and the elastic body can be easily fixed.

According to the twelfth aspect of the invention, in addition to the effect of the second aspect of the invention, the elastic body itself is rotated when a force in the rotational direction is received from the hammer. Therefore, it is possible to prevent the elastic body from being twisted.

According to the thirteenth aspect of the invention, in addition to the effect of the twelfth aspect of the invention, the friction between the rib and the elastic body is reduced, and the hammer receives a force in the rotational direction. By rotating the elastic body even more smoothly, it is possible to more reliably prevent the elastic body from being twisted.

According to the fourteenth aspect of the invention, in addition to the effects of the twelfth aspect of the invention, the friction between the rib and the elastic body is reduced, and the hammer receives a force in the rotational direction. By rotating the elastic body even more smoothly, it is possible to more reliably prevent the elastic body from being twisted.

According to the fifteenth aspect of the invention, in addition to the effect of the first aspect of the invention, it is not necessary to separately provide an elastic body, so that cost reduction and improvement of the assemblability can be achieved. There is an effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of an impact tool according to a first example of an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of an impact tool of a second example in the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a main part of an impact tool of a third example in the embodiment of the present invention.

FIG. 4 is a sectional view showing a main part of an impact tool of a fourth example according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a main part of an impact tool of a fifth example according to the embodiment of the present invention.

FIG. 6 is a sectional view showing a main part of an impact tool of a sixth example according to the embodiment of the present invention.

FIG. 7 shows an initial state of the impact tool of the same, (a) is a sectional view of a main part, and (b) is a schematic explanatory view for explaining a positional relationship between a steel ball and a cam groove. .

FIG. 8 shows a state where the hammer of the impact tool is retracted to the maximum, and (a) is a cross-sectional view of the main part,
(B) is a schematic explanatory drawing for demonstrating the positional relationship between a steel ball and a cam groove.

FIG. 9 shows the thrust plate and the elastic body of the above,
(A) is a front view and (b) is a sectional view.

FIG. 10 is an explanatory view for explaining the action of the hook portion of the above, where (a) is a case where the hook portion is not provided, (b)
The case where a hook part is provided is shown.

FIG. 11 shows a thrust plate and an elastic body of a seventh example in the embodiment of the present invention, (a) is a front view, and (b).
Is a sectional view.

FIG. 12 is an enlarged view of part A of FIG. 11 (b).

FIG. 13 is a cross-sectional view showing the main parts of an impact tool of an eighth example according to the embodiment of the present invention.

FIG. 14 is a cross-sectional view showing the main parts of the impact tool of the ninth example in the embodiment of the present invention.

FIG. 15 is an enlarged view of part B in FIG.

FIG. 16 is a sectional view of a main part of a conventional impact tool.

FIG. 17 shows an initial state of the impact tool of the above, (a) is a cross-sectional view of a main part, and (b) is a schematic explanatory view for explaining a positional relationship between a steel ball and a cam groove. .

FIG. 18 shows a state where the hammer of the above impact tool is retracted to the maximum, (a) is a sectional view of a main part, and (b) is a view for explaining a positional relationship between a steel ball and a cam groove. It is a schematic explanatory drawing.

[Explanation of symbols]

1 impact tool 2 housing 3 drive axis 3a Drive shaft cam groove 4 hammer 4a hammer cam groove 5 steel balls 6 anvil 7 spring 9 elastic body 10 ribs 11 Thrust plate 12 Hook part 12a Hook part 12b support part 13 through-hole 14 Locking part 15 Lubricants 16 bearings

Claims (15)

[Claims] 1. A hammer comprising a hammer slidably fitted to a drive shaft to rotate together, and an anvil meshing with the hammer to rotate together, when a load of a certain level or more is generated on the anvil. As a mechanism for converting the rotational movement of the drive shaft into the backward movement of the hammer, the drive shaft cam groove is used as the drive shaft, the hammer cam groove is used as the hammer, and the steel ball is fitted with the drive shaft cam groove and the hammer cam groove. Each impact is provided by providing a spring for imparting a biasing force to the hammer that causes the hammer and the anvil to mesh with the hammer after the hammer disengages due to the retreat of the hammer, and each member is covered with a housing. An impact tool, characterized in that an elastic body for restricting the retreat of the hammer is provided on the inner surface of the housing. 2. The impact tool according to claim 1, wherein a rib is provided so as to project from the inner surface of the housing, and the rib is provided with an elastic body. 3. The impact tool according to claim 2, wherein the rib and the elastic body are fixed by adhesion. 4. The elastic body is provided in the rib by fitting the recess formed in the elastic body and the rib.
Impact tool described in. 5. The rib is provided with an elastic body by press-fitting the rib into a recess formed in the elastic body.
Impact tool described in. 6. The impact tool according to claim 1, wherein a thrust plate is provided on a surface of the elastic body on the hammer side. 7. The impact tool according to claim 6, wherein the thrust plate is provided so as to protrude from the elastic body in the center direction of the housing. 8. The hook portion is extended from the thrust plate, and the hook portion is hooked and locked to a rib provided with an elastic body and protruding from the inner surface of the housing. Impact tool. 9. The impact tool according to claim 8, wherein a clearance is provided between a hook portion for hooking the rib on the hook portion, the rib and the elastic body. 10. The impact tool according to claim 8, wherein the hook portion of the thrust plate is provided at a position that restricts movement of the elastic body toward the center of the housing. 11. The impact according to claim 6, wherein a through hole is formed in the elastic body, and a locking portion that is locked to the through hole by fitting is provided by projecting from a thrust plate. tool. 12. The impact tool according to claim 2, wherein an elastic body is provided so as to be rotatable around a drive shaft. 13. The impact tool according to claim 12, wherein a sliding agent is interposed between the rib and the elastic body. 14. The impact tool according to claim 12, wherein a thrust bearing is interposed between the rib and the elastic body. 15. The impact tool according to claim 1, wherein an elastic body is provided integrally with the housing.