JPH04336978A - Impact wrench - Google Patents

Abstract

PURPOSE:To reduce the friction loss, to improve the transmitting efficiency of torque from an air motor to an output shaft, and to reduce the abrasion of a hammer, by making a rotary cylindrical body contact to the hammer through a steel ball at the time other than a locking projection strikes the hammer. CONSTITUTION:A rotary cylindrical body 5 is rotated by driving an air motor. And when a steel ball 16 moves from the condition in a guide groove 10 to the position the rotary cylindrical body 5 is rotated further and its inner circumferential surface 5b is abutted to the steel ball 16, a hammer 12 receives the force from the rotary cylindrical body 5 through the steel ball 16, a return gear 18 is moved to the right, and the hammer 12 is inclined. In this condition, the rotary cylindrical body 5 is rotated in the condition of very little friction loss only by point contacting with the steel ball 16. And when the rotary cylindrical body 5 is rotated further and its locking projection 8 strikes the hammer 12, the force is transmitted to an output shaft 6b through the hammer 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact wrench used for tightening and loosening bolts, nuts, etc.

0002

2. Description of the Related Art FIG. 6 shows an example of a conventional impact wrench. This impact wrench has a hammer case 4 in which a hammer 41 is swingably supported by a hammer stud 42.
3 is loosely fitted into a driver 44 spline-fitted to the rotor shaft (not shown) of the air motor, and the protrusion 41a of the hammer 41 is fitted into the recess 44a of the driver 44. 44 rotates, and as the hammer 41 rotates, the hammer 41 swings and rotates together with the hammer case 43. Then, the collar portion 4 of the output shaft 45 is pressed by this hammer 41.
5a, 45b to rotate the output shaft 45, and a socket (not shown) inserted into the square end 45c of the output shaft 45 is used to tighten bolts, nuts, etc. FIG. 7 is an explanatory diagram of the operation of this impact wrench. When the rotor shaft 50 is rotated in the direction of the arrow from the state shown in FIG. At this time, since resistance is applied to the output shaft 45 by the object to be fastened, the hammer 41 contacts the shaft 45 on its inner peripheral surface and rotates while sliding. With this rotation, one end L on the inner peripheral side of the hammer 41 gradually moves outward, and the other end R moves inward, resulting in the state shown in (b). As the rotation progresses further from this state, the end R of the hammer 41 collides with the collar 45b of the shaft 45, causing the shaft 45 to rotate, as shown in (c). Next, the end R of the hammer 41 is directed outward by the action of the driver 44, and as shown in (d), the hammer 41 rotates while sliding on the collar 45b of the output shaft 45, and enters a second striking motion. In this way, the output shaft 45 is struck twice by one revolution of the rotor shaft 50, and bolts, nuts, etc. are tightened while repeating this one after another.

0003

[Problems to be Solved by the Invention] In the conventional impact wrench described above, the driver 44 fits into the rotor shaft 50 of the air motor and rotates with the rotation of the rotor shaft 50.
The hammer 41 is rotated by
Since the hammer 1 rotates while contacting the output shaft 45, a large frictional force is generated, resulting in problems such as poor transmission efficiency of torque from the air motor to the output shaft 45 and increased wear on the hammer 41. SUMMARY OF THE INVENTION An object of the present invention is to provide an impact wrench that can improve the efficiency of torque transmission from the air motor to the output shaft and reduce wear on the hammer.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention controls the rotation of a rotating cylindrical body connected to a rotor shaft of a motor via a hammer swingably provided on the outer periphery of the base of an output shaft. The impact wrench is configured to transmit power to the output shaft, wherein a locking protrusion projecting inward from the inner circumferential surface of the rotary cylindrical body is provided at an appropriate position on the circular inner circumferential surface of the rotating cylinder, and the locking protrusion A portion of the inner circumferential surface of the locking protrusion is cut out to form a guide groove having a larger diameter than the inner circumferential surface, and a guide groove is formed on the outer periphery of the base of the output shaft at right angles to the output shaft. A support groove having a substantially semicircular cross section is carved in the axial direction, and the hammer is formed into a columnar shape having a substantially semicircular cross section and having an outer peripheral surface that makes sliding contact with the support groove, and the hammer and the rotating cylindrical body are connected to each other. A rotating body that can pass through the guide groove is disposed between the hammer, a holding groove for holding the rotating body so as to be movable in a direction perpendicular to the output shaft, and a spring is provided at the base of the output shaft. A return gear is provided that is biased to reciprocate in a direction perpendicular to the output shaft thereof, and
The hammer is provided with a gear groove that meshes with the return gear, and when the rotating cylinder rotates, the inner circumferential surface of the rotating cylinder pushes the rotating body to tilt the hammer, and the inclined hammer engages the hammer. The output shaft is characterized in that the stop protrusion portions collide with each other to rotate the output shaft.

[0005]

[Operation] In the above structure, while the rotating body is in the guide groove, the hammer receives no force from the rotating cylindrical body and is in a neutral state, and the return gear is in the center position. When the rotating cylindrical body rotates and its inner peripheral surface comes into contact with the rotating body,
The hammer receives a force from the rotating cylinder via its rotating body, the return gear moves in one direction, and the hammer tilts. In this state, the rotating cylindrical body rotates, and the rotating body rotates while slidingly contacting the inner peripheral surface of the rotating cylindrical body. When the rotating cylindrical body further rotates and its locking protrusion collides with the inclined hammer, the output shaft receives a force from the rotating cylindrical body via the hammer and rotates in the same direction as the rotating direction. At the same time, the spring biasing the return gear moves the return gear toward the center position and disengages the hammer from the locking projection, returning the hammer to its neutral state. Thereafter, in the same manner, the output shaft is rotated by hitting the hammer once every time the rotating cylindrical body rotates once. In this way, the rotating cylindrical body does not come into contact with the hammer until it is struck by the hammer, and only slightly contacts the rotating body, so only friction loss due to rolling friction occurs, and the friction loss is small. Therefore, the efficiency of transmitting torque from the motor to the output shaft is improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to illustrated embodiments. FIG. 1 is a longitudinal sectional side view of an embodiment of the impact wrench of the present invention, and FIGS. 2 to 5 are sectional views showing the operation of this embodiment. In these figures, 1 is a front casing, 2 is a rear casing, 3 is an air motor housed in the rear casing, 4 is a rotor shaft of the air motor, and 5 is a circular rear wall portion at the tip of the rotor shaft 4. 5a is a rotating cylindrical body whose center part is spline-fitted to rotate integrally with the rotor shaft 4; 6 is the front casing 1;
The output shaft is rotatably supported via a bush 7 by the front end portion 1a of the output shaft. The rotating cylindrical body 5 has an inner circumferential surface 5b formed into a perfect circular surface, and locking protrusions 8 protruding radially inward from the inner circumferential surface at appropriate locations on the inner circumferential surface.
is integrally formed in the length direction, and this locking protrusion 8
Both side surfaces 8a and 8b in the circumferential direction are formed into gently concave arc-shaped surfaces, and these surfaces are connected to arcuate grooves 9a and 9b cut from the inner peripheral surface of the rotating cylindrical body 5 in the outer radial direction. and,
The guide groove 1 is formed by cutting approximately the central part of the locking projection 8 and a part of the inner circumferential surface of the locking projection 8 in the circumferential direction.
0 is formed. Further, the output shaft 6 forms a mounting angle shaft 6a at the end protruding forward from the front casing 1 for attaching a fitting socket (not shown) such as a bolt or nut. A shaft portion 6c protruding from the center of the rear surface of the base portion 6b housed in the rotary cylindrical body 5 is rotatably fitted into a central hole of the circular rear wall portion 5a of the rotating cylindrical body 5. A support groove 6d having a semicircular cross section is formed in the axial direction on the outer periphery of the base 6b, and a columnar hammer 12 having a substantially semicircular cross section and having an outer peripheral surface that slides in contact with the support groove 6d is attached to the base 6b. It is swingably supported by a front end portion 6e and a retainer 15 fitted to the shaft portion 6c. A steel ball 16 as a rotating body that can pass through the guide groove 10 is disposed between the hammer 12 and the rotating cylindrical body 5, and
The hammer 12 is provided with a holding groove 12a for holding the steel ball 16 movably in a direction perpendicular to the base 6b of the output shaft. Also, a spring 17a is attached to the base 6b of the output shaft.
, 17b so as to be able to reciprocate in a direction perpendicular to the base 6b, and a gear groove 12b that meshes with the return gear 18 is provided on the outer peripheral surface of the hammer 12. 12, the return gear 18 moves in a direction perpendicular to the base.

The operation of the impact wrench constructed as described above will be explained based on FIGS. 2 to 5. Figure 2 shows hammer 1
2 is in the neutral position, the rotating cylindrical body 5 is rotated in the direction of the arrow by the rotation of the air motor 3, and the steel ball 16 is floating from the hammer 12 due to centrifugal force. It is rolling on an inner orbit within the body. When the rotating cylindrical body 5 further rotates from this state and its inner peripheral surface 5b comes into contact with the steel ball 16, the steel ball 16 moves to the left in the holding groove 12a of the hammer 12, raising the hammer 12, and Move the return gear 18 to the right. and,
As shown in FIG. 3, the rotary cylindrical body 5 continues to rotate with the hammer 12 tilted and the return gear 18 moved to the right. At this time, the steel ball 16 is sandwiched between the rotating cylindrical body 5, the hammer 12, and the base 6b of the output shaft, and the hammer 12 is tilted against the force of the spring 17b. The rotating cylindrical body 5 is in only point contact with the steel ball 16 and only slightly in contact with the hammer 12, and rotates with very little friction loss. In this example, the hammer 12 is in slight contact with the rotating cylindrical body 5, but it is possible to prevent it from making contact. FIG. 4 shows a state on the verge of striking, and when the rotating cylindrical body 5 rotates a little from this state, as shown in FIG. 8 a collide, and the rotation of the rotating cylindrical body 5 is transmitted to the output shaft 6 via the hammer 12 . In this state, the hammer 12 is receiving a force trying to push the steel ball 16 outward due to the force of the spring 17b, that is, a force trying to remove the outer surface of the hammer 12 from the locking protrusion 8. The elastic force of 17b is set to be larger than the static frictional force between the locking protrusion 8 and the hammer 12, and smaller than the sum of this frictional force and the rotational force of the hammer 12 due to the rotation of the rotating cylindrical body 5. Therefore, the locking protrusion 8 and the hammer 12 maintain the locked state, and the rotating cylindrical body 5
The output shaft 6 rotates integrally with the output shaft 6, and a socket (not shown) attached to the tip of the output shaft 6 rotates bolts, nuts, etc. Then, when the resistance from the output shaft 6 due to tightening of bolts, nuts, etc. reaches the motor torque,
Unless the engagement between the locking protrusion 8 and the hammer 12 is released, the output shaft 6 approaches a stop while decreasing its rotational speed. Therefore, the rotational force of the hammer 12 becomes smaller, and when the rotational force disappears, the restoring force of the spring 17b overcomes the static friction force between the locking protrusion 8 and the hammer 12, and the hammer 12
2 clockwise to remove it from the locking protrusion 8, and while passing the steel ball 16 through the guide groove 10 of the rotating cylindrical body 5,
The rotating cylindrical body 5 performs free running. Then, the return gear 18 returns to the central position, and the hammer 12 becomes neutral, returning to the state shown in FIG. 2. Thereafter, by the same operation, the hammer 12 is struck only once every time the rotating cylindrical body 5 rotates once. At this time, the air motor 3 is connected to the output shaft 6 side.
When there is a resistance torque greater than the rotational torque of , even if the engagement protrusion 8 of the rotating cylindrical body 5 and the hammer 12 engage, the rotational force that sustains the engagement is generated only momentarily. Then, the engagement is immediately disengaged, and after the rotating cylindrical body 5 rotates once again, the two engage, and as the resistance torque increases, the engagement between the two becomes shocking. By repeating this impact, the screw is completely tightened. In addition, when loosening the screw, rotate the air motor 3 in the opposite direction (opposite to the arrow) to engage and disengage the other outer surface 12c of the hammer 12 from the other side surface 8b of the protrusion 8. good.

As is clear from the above description, the rotating cylindrical body 5 is in a state with very little friction loss, with only point contact with the steel ball 16, except when striking the hammer 12 with its engaging protrusion 8. Since the hammer 41 is rotated by the driver 44 that rotates with the rotation of the rotor shaft 50, and the hammer 41 rotates while contacting the output shaft 45, the hammer 41 can be rotated by the air motor 3 to the output shaft 6. The efficiency of torque transmission to the hammer is greatly improved, and the wear of the hammer is also reduced. In addition, although the steel ball 16 was used as a rotating body in the said Example, a roller may be used instead of this steel ball.

[0009]

As is clear from the above, the impact wrench of the present invention has locking protrusions that protrude inwardly from the inner circumferential surface of the rotating cylindrical body at appropriate locations on the circular inner circumferential surface of the rotating cylinder connected to the rotor shaft of the motor. A part of the locking protrusion and a part of the inner circumferential surface of the locking protrusion before and after the locking protrusion are cut out to form a guide groove having a larger diameter than the inner circumferential surface, and a guide groove is formed on the output shaft. A support groove having a substantially semicircular cross section perpendicular to the output shaft is engraved in the axial direction on the outer periphery of the output shaft, and an outer peripheral surface in which a hammer swingably provided on the outer periphery of the base of the output shaft slides into contact with the support groove. A rotating body that can pass through the guide groove is disposed between the hammer and the rotating cylindrical body, and the rotating body is connected to the hammer with the output shaft. A retaining groove is provided at the base of the output shaft to allow reciprocating movement in the direction perpendicular to the output shaft. A gear groove is provided that meshes with the rotary cylinder, and as the rotary cylinder rotates, the inner circumferential surface of the rotary cylinder presses the rotary body to tilt the hammer, and the locking protrusion collides with the inclined hammer. Therefore, when rotating the rotating cylindrical body, the locking protrusion only slightly contacts the rotating body, except when the locking protrusion collides with the hammer. Since only a small frictional force is applied, the efficiency of transmitting torque from the motor to the output shaft can be improved, the device can be made smaller and the cost can be reduced, and wear on the hammer can be reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of an embodiment of the present invention.

FIG. 2 is a sectional view showing the operation of the above embodiment.

3 is a sectional view showing a state where rotation has progressed from the state shown in FIG. 2. FIG.

FIG. 4 is a sectional view showing a state just before impact in the above embodiment.

FIG. 5 is a sectional view showing a striking state in the above embodiment.

FIG. 6 is a sectional view of a conventional example.

FIG. 7 is an explanatory diagram of the operation of the above conventional example.

[Explanation of symbols]

3... Air motor, 4... Rotor shaft, 5... Rotating cylindrical body, 5b
...Inner peripheral surface, 6...Output shaft, 6b...Base, 6d...Support groove, 8
...Locking protrusion, 10...Guide groove, 12...Hammer, 12a
...Holding groove, 12b...Gear groove, 16...Steel ball, 17a, 17
b...Spring, 18...Return gear.

Claims (1)

[Claims] 1. An impact wrench in which the rotation of a rotating cylindrical body connected to a rotor shaft of a motor is transmitted to the output shaft via a hammer swingably provided on the outer periphery of the base of the output shaft, the impact wrench comprising: A locking protrusion projecting inward from the inner circumferential surface of the rotating cylindrical body is provided at an appropriate position on the circular inner circumferential surface, and a portion of the locking protrusion and the inner periphery in front and behind the locking protrusion in the circumferential direction are provided. A part of the surface is removed to form a guide groove with a larger diameter than the inner circumferential surface, and a support groove with a substantially semicircular cross section perpendicular to the output shaft is carved in the axial direction on the outer periphery of the base of the output shaft. At the same time,
The hammer is formed into a columnar shape with a substantially semicircular cross section having an outer peripheral surface that slides in contact with the support groove, and a rotating body that can pass through the guide groove is disposed between the hammer and the rotating cylindrical body, and The hammer is provided with a holding groove for holding the rotating body movably in a direction perpendicular to the output shaft, and a return is biased by a spring at the base of the output shaft so as to be able to reciprocate in the direction perpendicular to the output shaft. a gear is provided, and the hammer is provided with a gear groove that meshes with the return gear, and as the rotating cylindrical body rotates, the inner circumferential surface of the rotating cylindrical body pushes the rotating body to tilt the hammer;
The impact wrench is characterized in that the locking protrusion collides with the inclined hammer to rotate the output shaft.