WO2018061387A1

WO2018061387A1 - Rotary impact tool

Info

Publication number: WO2018061387A1
Application number: PCT/JP2017/024810
Authority: WO
Inventors: 雅理村松; 隆司草川
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2016-09-27
Filing date: 2017-07-06
Publication date: 2018-04-05
Also published as: JP2018051659A; JP6719084B2

Abstract

This rotary impact tool (1) is provided with: a main hammer (20) which is capable of rotating around a rotational axis of a spindle (11), and which is capable of moving in the direction of the rotational axis; a first cam structure in which steel spheres (19) are provided between a first guidance groove (11b) at the spindle side and a first engagement groove (20b) at the main hammer side; an anvil (22) on which rotary impact force is exerted by the main hammer (20); a secondary hammer (21) capable of rotating integrally with the main hammer (20); a large diameter part which is provided to the rear side of the first guidance groove (11b), and which has a larger external diameter than a portion of the spindle (11) in which the first guidance groove (11b) is formed; and a second cam structure in which steel spheres (17) are provided between a second guidance groove (16a) at the large diameter part side, and a second engagement groove (21f) at the secondary hammer side. The rotary impact tool (1) is formed such that the secondary hammer (21) moves in the opposite direction to the movement direction of the main hammer (20), when the main hammer (20) moves in the direction of the rotational axis.

Description

Rotating hammer tool

The present invention relates to a rotary impact tool.

In the rotary impact tool, the hammer is urged toward the anvil side by a spring so that the hammer claw and the anvil claw are engaged in the circumferential direction, and the rotation of the hammer is transmitted to the anvil. When a load torque exceeding a predetermined value is applied to the anvil, the hammer moves backward against the spring biasing force. When the hammer claw and the anvil claw are disengaged due to the retraction of the hammer, the hammer advances while rotating, and the hammer claw strikes the anvil claw in the rotation direction. At this time, impact is generated in the direction of the rotation axis due to the rotation impact, but the impact generated in the direction of the rotation axis does not contribute to tightening the bolts and nuts and is transmitted as vibration to the tool body, so it can be reduced as much as possible. preferable.

Patent Document 1 discloses an impact including a spindle rotated by a driving unit, an anvil disposed in front of the spindle in the rotation axis direction, and a rotary striking mechanism that converts the rotation of the spindle into a rotational striking and transmits it to the anvil. Disclose wrench. The rotary striking mechanism includes a main hammer that can rotate about the rotation axis of the spindle and move in the axial direction, and a sub hammer that rotates integrally with the main hammer but does not move in the axial direction. In the impact wrench disclosed in Patent Document 1, a cam structure in which a steel ball is arranged between a guide groove on the spindle side and an engagement groove on the main hammer side is provided, and the main hammer can move backward and forward at high speed. Repeat with to give the anvil a rotational impact.

JP 2014-240108 A

The magnitude of the impact in the direction of the rotation axis is proportional to the mass of the hammer hitting the anvil, and the magnitude of the impact in the direction of rotation is the moment of inertia of the rotating hammer (the mass of each part in the object and the rotation from that part) Proportional to the sum of the product of the distance to the axis and the square. The impact wrench of Patent Document 1 adopts a double hammer configuration, and the mass of the auxiliary hammer that contributes only to the impact in the rotational direction is made larger than the mass of the main hammer, thereby maintaining the magnitude of the impact in the rotational direction. The impact of the hammer in the direction of the rotation axis is reduced.
The inventors of the present invention have come up with a technique for reducing the vibration in the rotation axis direction transmitted to the tool body by changing the double hammer configuration disclosed in Patent Document 1.

The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for reducing vibration in the rotation axis direction transmitted to the tool body in a rotary impact tool having a main hammer and a sub hammer. is there.

In order to solve the above-described problems, a rotary impact tool according to an aspect of the present invention includes a drive unit, a spindle that is rotated by the drive unit, a main unit that is rotatable about the rotation axis of the spindle and is movable in the direction of the rotation axis. A first cam structure in which a first steel ball is disposed between a hammer, a first guide groove on the spindle side, and a first engagement groove on the main hammer side; an anvil to which a rotational striking force is applied by the main hammer; A sub-hammer that can rotate integrally with the hammer, a large-diameter portion that is provided on the rear side of the first guide groove and has a larger outer diameter than the portion of the spindle on which the first guide groove is formed; And a second cam structure in which a second steel ball is disposed between the second guide groove and the second engagement groove on the sub hammer side. The rotary impact tool of this aspect is configured such that when the main hammer moves in the rotation axis direction, the sub hammer moves in the direction opposite to the movement direction of the main hammer.

It is a section schematic diagram of the principal part of the rotary impact tool concerning an embodiment. It is a disassembled perspective view of the component of the rotation impact mechanism which concerns on embodiment. It is an assembly perspective view of the rotation impact mechanism concerning an embodiment. (A) is a front side perspective view of a main hammer, (b) is a perspective view of a spindle and a carrier, and (c) is a rear side perspective view of a sub hammer. (A) And (b) is a figure which shows the operation state of a 1st cam structure. (A)-(c) is a figure which shows the positional relationship which expanded the engagement surface of the main hammer and the anvil typically in the circumferential direction. (A) And (b) is a figure which shows the operation state of a 2nd cam structure. (A)-(c) is a figure which shows the rotation impact mechanism which concerns on embodiment. It is a schematic sectional drawing of a rotation impact mechanism.

The rotary impact tool of the embodiment includes a spindle rotated by a drive unit, an anvil disposed in front of the spindle in the rotation axis direction, and a rotary impact mechanism that converts rotation of the spindle into rotational impact and transmits the rotational impact to the anvil. Prepare. The rotary hammering mechanism employs a double hammer configuration, and includes a main hammer that is rotatable about the rotation axis of the spindle and is movable in the axial direction, and a sub hammer that is rotatable integrally with the main hammer. The rotary striking mechanism has a function of causing the main hammer to impactably engage the anvil and rotating the anvil about the axis.

FIG. 1 is a schematic cross-sectional view of a main part of a rotary impact tool according to an embodiment. In FIG. 1, an alternate long and short dash line indicates a rotation axis of the rotary impact tool 1. FIG. 2 is an exploded perspective view of components of the rotary impact mechanism according to the embodiment, and FIG. 3 is an assembled perspective view of the rotary impact mechanism according to the embodiment. In FIG. 3, the illustration of a later-described stopper member 27 is omitted for ease of viewing. 4A is a front perspective view of the main hammer, FIG. 4B is a perspective view of the spindle and the carrier, and FIG. 4C is a rear perspective view of the auxiliary hammer. Hereinafter, the structure of the rotary impact tool 1 will be described with reference to FIGS.

The rotary impact tool 1 includes a housing 2 that constitutes a tool body. The upper part of the housing 2 forms an accommodation space for accommodating various components, and the lower part of the housing 2 constitutes a grip portion 3 that is gripped by the user. An operation switch 4 that is operated by a user's finger is provided on the front side of the grip 3, and a battery (not shown) that supplies power to the drive unit 10 is provided at the lower end of the grip 3.

The drive unit 10 is an electric motor, and the drive shaft 10 a of the drive unit 10 is connected to the carrier 16 and the spindle 11 via the power transmission mechanism 12. The carrier 16 is located on the rear end side of the spindle 11 and accommodates a power transmission gear. With reference to FIG. 4B, the carrier 16 is configured as a large-diameter portion having an outer diameter larger than that of the spindle 11. The carrier 16 has a front member 16b having a diameter larger than that of the spindle 11, and a rear member 16c positioned rearward of the front member 16b, and accommodates a gear between the front member 16b and the rear member 16c. The space 16d is formed.

The power transmission mechanism 12 includes a sun gear 13 that is press-fitted and fixed to the tip of the drive shaft 10 a, two planetary gears 14 that mesh with the sun gear 13, and an internal gear 15 that meshes with the planetary gear 14. The planetary gear 14 is rotatably supported in a space 16d of the carrier 16 by a support shaft 14a fixed to the front member 16b and the rear member 16c. The internal gear 15 is fixed to the inner peripheral surface of the housing 2.

With the power transmission mechanism 12 configured as described above, the rotation of the drive shaft 10a is decelerated based on the ratio between the number of teeth of the sun gear 13 and the number of teeth of the internal gear 15, and the rotational torque is increased. . As a result, the carrier 16 and the spindle 11 can be driven at low speed and high torque.

Rotating impact mechanism of the rotating impact tool 1 includes a spindle 11, a carrier 16, a main hammer 20, a secondary hammer 21 and a spring member 23. The spindle 11 is formed in a columnar shape, and a small-diameter protrusion 11 a is formed at the tip thereof coaxially with the axis of the spindle 11. The protrusion 11a is inserted in a rotatable state into a hole having a cylindrical inner space formed in the rear part of the anvil 22.

A steel main hammer 20 having a substantially disc shape and having a through hole in the center is mounted on the outer periphery of the spindle 11. A pair of hammer claws 20 a projecting toward the anvil 22 are formed on the front surface of the main hammer 20. The main hammer 20 is attached to the spindle 11 so as to be rotatable about the rotation axis of the spindle 11 and to be movable in the direction of the rotation axis of the spindle 11, that is, in the front-rear direction. As a result, the main hammer 20 can apply a rotational striking force to the anvil 22. The auxiliary hammer 21 is formed as a steel cylindrical member, and is divided into a front part 21a and a rear part 21b by an annular partition part 21e. The sub hammer 21 accommodates the main hammer 20 in the internal space of the front portion 21a.

The auxiliary hammer 21 and the main hammer 20 are provided with an integral rotation mechanism that rotates together. Referring to FIG. 2, the main hammer 20 includes four first pin grooves 20 d on its outer peripheral surface and having a semicircular cross section and parallel to the rotation axis of the spindle 11. The auxiliary hammer 21 includes four second pin grooves 21 c on the inner peripheral surface of the front portion 21 a and having a semicircular cross section and parallel to the rotation axis of the spindle 11. Here, the four second pin grooves 21 c of the sub hammer 21 are formed at positions corresponding to the four first pin grooves 20 d of the main hammer 20. The first pin grooves 20 d may be formed at an interval of 90 degrees on the outer peripheral surface of the main hammer 20. At this time, the second pin grooves 21 c are formed at an interval of 90 degrees on the inner peripheral surface of the sub hammer 21.

In the second pin groove 21c, an engagement pin 26 that is a cylindrical member is disposed. The engagement pin 26 may be a needle roller. The engaging pin 26 is inserted into the second pin groove 21c from the front end side of the sub hammer 21 and inserted to the groove bottom. With the engagement pin 26 inserted to the bottom of the groove, a stop member 27 having a function of preventing the engagement pin 26 from being detached is fitted into the annular groove 21d formed on the inner peripheral surface of the sub hammer 21. By disposing the stop member 27 in the annular groove 21d, the movement of the engagement pin 26 in the second pin groove 21c is limited.

At the time of assembly, the four first pin grooves 20d of the main hammer 20 and the four engagement pins 26 are aligned with the four engagement pins 26 attached to the four second pin grooves 21c of the sub hammer 21. Then, the main hammer 20 is inserted into the sub hammer 21. As a result, the main hammer 20 and the sub hammer 21 can be rotated together around the rotation axis of the spindle 11.

The main hammer 20 has an annular recess 20c on the rear side. The spring member 23 is interposed between the concave portion 20 c of the main hammer 20 and the annular partition portion 21 e of the sub hammer 21. The main hammer 20 can move in the front-rear direction using the engaging pin 26 as a guide, and can apply a rotational striking force to the anvil 22 by the biasing force of the spring member 23.

The spindle 11 includes two first guide grooves 11b on the outer peripheral surface thereof, and the main hammer 20 includes two first engagement grooves 20b on the inner peripheral surface of the through hole. The two first guide grooves 11b have the same shape and are arranged in the circumferential direction, and the two first engagement grooves 20b have the same shape and are arranged in the circumferential direction. With the main hammer 20 mounted on the outer periphery of the spindle 11, a steel ball 19 is disposed between the first guide groove 11b and the first engagement groove 20b. The first guide groove 11b on the spindle 11 side, the first engagement groove 20b on the main hammer 20 side, and the steel ball 19 disposed therebetween constitute a “first cam structure”. The two steel balls 19 support the main hammer 20 in the radial direction so that the main hammer 20 can rotate around the rotation axis of the spindle 11 and move in the direction of the rotation axis.

The carrier 16 having a diameter larger than that of the spindle 11 includes three second guide grooves 16a on the outer periphery of the front surface of the front member 16b, and the auxiliary hammer 21 includes three second engagement grooves 21f on the rear surface of the annular partition portion 21e. . The three second guide grooves 16a have the same shape and are arranged in the circumferential direction, and the three second engagement grooves 21f have the same shape and are arranged in the circumferential direction. In a state where the spindle 11 is inserted into the auxiliary hammer 21, a steel ball 17 is disposed between the second guide groove 16a and the second engagement groove 21f. The steel ball 17 is preferably the same steel ball as the steel ball 19 from the viewpoint of manufacturing cost. That is, the steel ball 17 is preferably formed of the same material as the steel ball 19 and has the same size. The second guide groove 16a on the carrier 16 side, the second engagement groove 21f on the sub hammer 21 side, and the steel ball 17 disposed between them constitute a “second cam structure”. The three steel balls 17 support the auxiliary hammer 21 in the direction of the rotation axis so that the auxiliary hammer 21 can rotate around the rotation axis of the spindle 11 and move in the direction of the rotation axis.

In the first cam structure, the first guide groove 11b is formed in a V-shape or a U-shape when viewed from the tip side of the tool. That is, the 1st guide groove 11b has two inclination grooves which incline in the back diagonal direction symmetrically from the foremost part. The first engagement groove 20b is formed in a V-shape or U-shape that is opposite to the tool tip side. When the steel ball 19 moves along the inclined groove from the foremost part of the first guide groove 11 b, the main hammer 20 moves backward relative to the spindle 11.

In the second cam structure, the second guide groove 16a is formed in a V shape or a U shape as viewed from the rear end side of the tool. That is, the second guide groove 16a has two inclined grooves that are symmetrically inclined in the front oblique direction from the rearmost part. The second engagement groove 21f is formed in a V-shape or U-shape in the reverse direction when viewed from the tool rear end side. When the steel ball 17 moves along the inclined groove from the rearmost part of the second guide groove 16 a, the auxiliary hammer 21 moves forward relative to the carrier 16.

Thus, the first guide groove 11b and the second guide groove 16a are formed with inclined grooves extending in different directions in the rotation axis direction. With the first cam structure and the second cam structure, when the main hammer 20 moves in the rotation axis direction, a configuration in which the auxiliary hammer 21 that rotates integrally with the main hammer 20 moves in the direction opposite to the movement direction of the main hammer 20 is realized. The That is, when the main hammer 20 moves backward in the rotation axis direction, the sub hammer 21 moves forward, and when the main hammer 20 moves forward, the sub hammer 21 moves backward.

The stopper member 30 is provided between the main hammer 20 and the carrier 16 so that the steel ball 19 in the first cam structure and the steel ball 17 in the second cam structure do not collide with the end portions of the respective inclined grooves. The movement range in the direction of the 20 rotation axis is regulated. The stopper member 30 may be formed of a resin material, for example.

The anvil 22 that engages with the main hammer 20 is made of steel, and is rotatably supported by the housing 2 via a steel or brass sliding bearing. The tip of the anvil 22 is provided with a tool mounting portion 22a having a square cross section for mounting a socket body to be mounted on the head of a hexagon bolt or a hexagon nut.

A pair of anvil claws that engage with the pair of hammer claws 20a of the main hammer 20 are provided at the rear of the anvil 22. Each of the pair of anvil claws is formed as a columnar member having a sectional fan shape. The anvil claw of the anvil 22 and the hammer claw 20a of the main hammer 20 do not necessarily have to be two, and if the number of the respective claws is equal, three or more at equal intervals in the circumferential direction of the anvil 22 and the main hammer 20 It may be provided.

Next, operation | movement of the 1st cam structure in the rotary impact tool 1 of embodiment is demonstrated.
When the drive unit 10 is rotationally driven by the pulling operation of the operation switch 4 by the user, the carrier 16 and the spindle 11 are rotated via the power transmission mechanism 12. The rotational force of the spindle 11 is transmitted to the main hammer 20 via a steel ball 19 fitted between the first guide groove 11b of the spindle 11 and the first engagement groove 20b of the main hammer 20, and the main hammer 20 and the auxiliary hammer 20 The hammer 21 rotates as a unit.

FIG. 5A shows the state of the first cam structure immediately after the start of tightening of the bolts and nuts, and FIG. 5B shows the state of the first cam structure after a lapse of time from the start of tightening. FIG. 5B is a comparative view for comparison with the initial state of the first cam structure shown in FIG. 5A, and the steel ball 19 moves from the foremost part of the first guide groove 11b toward the groove end. It shows how it moves. In this comparative view, the steel ball 19 is shown moving to the vicinity of the groove end portion. However, in the embodiment, as described later, the circumferential movable range of the second cam structure is narrower than the first cam structure. For this reason, the steel ball 19 moves with the limit in front of the groove end.

6 (a) to 6 (c) show a positional relationship in which the engagement surfaces of the main hammer 20 and the anvil 22 are schematically developed in the circumferential direction. Here, FIG. 6A shows an engaged state between the hammer claw 20a of the main hammer 20 and the anvil claw 22b of the anvil 22 immediately after the start of tightening the bolts and nuts.

As shown in FIGS. 6A to 6C, a rotational force A due to the rotation of the driving unit 10 is applied to the main hammer 20 in the direction indicated by the arrow. Further, a forward biasing force B by the spring member 23 is applied to the main hammer 20 in the direction indicated by the arrow.

When the main hammer 20 rotates, the rotational force of the main hammer 20 is transmitted to the anvil 22 by the circumferential engagement of the hammer claws 20a and the anvil claws 22b. As the anvil 22 rotates, a socket body (not shown) attached to the tool mounting portion 22a rotates, and initial tightening is performed by applying a rotational force to the bolts and nuts. Since the spring member 23 applies the urging force B to the main hammer 20, the steel ball 19 is positioned at the foremost part in the first guide groove 11b as shown in FIG. At this time, the hammer claw 20a and the anvil claw 22b are in an engaged state with the maximum engagement length.

When the load torque applied to the anvil 22 increases as the tightening of the bolts and nuts proceeds, a rotational force in the Y direction is generated in the main hammer 20. When the load torque exceeds a predetermined value, the steel ball 19 moves in the direction indicated by the arrow F along the slopes of the first guide groove 11b and the first engagement groove 20b against the biasing force B of the spring member 23. Then, the main hammer 20 moves in the backward direction (X direction).

When the steel ball 19 moves in the inclined groove and the main hammer 20 moves in the X direction by a distance corresponding to the maximum engagement length between the hammer claw 20a and the anvil claw 22b, as shown in FIG. The engagement between the hammer claw 20a and the anvil claw 22b is released.

When the hammer claw 20a is detached from the anvil claw 22b, the biasing force B of the compressed spring member 23 is released, so that the main hammer 20 rotates at a high speed in the direction in which the rotational force A is applied. Move forward by force B.

Then, as shown in FIG. 6C, the hammer claw 20 a moves along the locus indicated by the arrow G, collides with the anvil claw 22 b, and applies a striking force in the rotation direction to the anvil 22. Thereafter, the hammer claw 20a is moved in the direction opposite to the locus G by the reaction, but finally returns to the state shown in FIG. 6A by the rotational force A and the urging force B. The above operation is repeated at a high speed, and the rotational hammering force by the main hammer 20 is repeatedly applied to the anvil 22.

The above is the description of the operation when tightening the bolt or nut, but when the tightened bolt or nut is loosened, the same operation as when tightening is performed by the rotary impact mechanism. In this case, by rotating the drive unit 10 in the direction opposite to that at the time of tightening, the steel ball 19 moves to the upper right along the first guide groove 11b shown in FIG. 5A, and the hammer claw 20a is moved to the anvil claw. Strike 22b in the opposite direction to that during tightening.

Since the rotary impact tool 1 of the embodiment employs a double hammer configuration, the magnitude of the impact in the rotational direction is proportional to the total moment of inertia of the main hammer 20 and the secondary hammer 21, while the magnitude of the impact in the rotational axis direction. The length is proportional to the mass of the main hammer 20. According to the rotary impact tool 1, by making the mass of the sub hammer 21 larger than the mass of the main hammer 20, the impact force generated in the direction of the rotation axis when the main hammer 20 applies the rotary impact force to the anvil 22 is reduced. it can.

Compared with the rotary impact tool 1 using one hammer having the total mass of the main hammer 20 and the secondary hammer 21, the rotary impact tool 1 of the embodiment has the same impact magnitude in the rotational direction as it is in the rotational axis direction. Reduce the magnitude of impact. By making the mass of the main hammer 20 as small as possible compared with the mass of the sub hammer 21, the impact force generated in the direction of the rotation axis can be further reduced.

Further, in the embodiment, the moment of inertia is increased by utilizing the fact that the magnitude of the moment of inertia is proportional to the square of the turning radius. That is, by providing the auxiliary hammer 21 having a large mass on the outer peripheral side of the main hammer 20, the moment of inertia of the auxiliary hammer 21 is increased and the impact force in the rotational direction by the double hammer is increased.

Next, the operation of the second cam structure will be described. In the second cam structure, the sub hammer 21 is moved in the direction opposite to the movement of the main hammer 20 in the rotation axis direction, so that the impact generated in the rotation axis direction by the main hammer 20 is canceled and vibration transmitted to the housing 2 is transmitted. It has a role to further reduce.

Since the auxiliary hammer 21 rotates integrally with the main hammer 20, the relative position of the auxiliary hammer 21 and the main hammer 20 in the circumferential direction does not change. Therefore, when the steel ball 19 moves toward the groove end portion of the first guide groove 11b in the first cam structure, the steel ball 17 moves toward the groove end portion of the second guide groove 16a also in the second cam structure.

FIG. 7A shows the state of the second cam structure immediately after the start of tightening of the bolts and nuts, and FIG. 7B shows the state of the second cam structure after a lapse of time from the start of tightening. When the steel ball 19 is positioned at the foremost portion of the first guide groove 11b in the first cam structure (see FIG. 5A), the steel ball 17 is positioned at the rearmost portion of the second guide groove 16a in the second cam structure. (See FIG. 7A).

Then, when the steel ball 19 moves along the inclined surface from the foremost portion of the first guide groove 11b in the first cam structure, the steel ball 17 moves from the rearmost portion of the second guide groove 16a to the inclined surface also in the second cam structure. Move along. FIG.7 (b) shows a mode that the steel ball 17 is moving the 2nd guide groove 16a. At this time, the secondary hammer 21 moves in the direction opposite to the moving direction (X direction) of the main hammer 20. That is, when the main hammer 20 moves backward, the auxiliary hammer 21 moves forward.

As described above, the rotary hammer 1 is moved by the first cam structure and the second cam structure so that when the main hammer 20 moves in the rotation axis direction, the sub hammer 21 moves in the direction opposite to the movement direction of the main hammer 20. It is configured. The sub hammer 21 moves in the direction opposite to the movement direction of the main hammer 20 in synchronization with the movement of the main hammer 20, so that vibration generated by the movement of the main hammer 20 in the axial direction can be absorbed and vibration transmitted to the user's hand. Can be reduced.

FIG. 8A shows a front view of the rotary striking mechanism. FIG. 8A shows a state where the two steel balls 19 are positioned at the forefront of the first guide groove 11b. The first engagement groove 20b having a shape opposite to that of the first guide groove 11b has two inclined grooves inclined forward from the rearmost part where the steel ball 19 is disposed.
FIG. 8B shows a CC cross-sectional view of the rotary impact mechanism. In FIG. 8B, illustration of the spring member 23, the planetary gear 14 and the like is omitted. In this state, the three steel balls 17 are respectively located at the rearmost part of the second guide groove 16a.
FIG. 8C shows a DD sectional view of the rotary striking mechanism. The second guide groove 16a has two inclined grooves inclined forward from the rearmost part where the steel ball 17 is disposed.

As described above, the secondary hammer 21 and the main hammer 20 are restricted from relative rotation about the axis while allowing the relative movement in the axis direction by the engagement pin 26. The auxiliary hammer 21 is pressed against the carrier 16 by the spring member 23, and the rear surface of the annular partition 21 e is supported by three steel balls 17 disposed on the outer periphery of the front member 16 b of the carrier 16.

Since the auxiliary hammer 21 and the main hammer 20 rotate integrally at high speed, the rotation axes of the auxiliary hammer 21 and the main hammer 20 need to coincide with the rotation axis of the spindle 11, that is, be coaxial. Therefore, as far as the secondary hammer 21 is concerned, the steel ball 17 must stably support the rear surface of the annular partition 21e in the direction of the rotation axis so that the secondary hammer 21 and the spindle 11 remain coaxial.

Therefore, the rotary impact tool 1 of the embodiment includes three second cam structures in which the steel balls 17 are arranged between the second guide groove 16a and the second engagement groove 21f, and the three steel balls 17 are sub-hammers. The rear surface of the 21 annular partitioning portions 21e is supported at three points in the rotational axis direction. Compared to the case where the auxiliary hammer 21 is supported by one or two steel balls 17, the auxiliary hammer 21 is supported by the three steel balls 17, thereby effectively suppressing the inclination of the auxiliary hammer 21 with respect to the rotation axis direction. It becomes possible to maintain the coaxiality of the auxiliary hammer 21 and the spindle 11.

The steel ball 17 is disposed on the outer periphery of the front surface of the front member 16b having a diameter larger than that of the spindle 11. Since the peripheral speed of the outer periphery of the front member 16b is larger than the outer periphery of the spindle 11, if the auxiliary hammer 21 is supported by the same number (two) of steel balls 17 as the steel balls 19 in the first cam structure, It is conceivable that the wear of the steel ball 17 is more advanced than 19. Therefore, the tool reliability can be improved by increasing the number of steel balls 17 in the second cam structure than the number of steel balls 19 in the first cam structure.

It is preferable that the three second cam structures are provided at equal intervals in the circumferential direction. As a result, the three steel balls 17 are positioned at an interval of 120 degrees from each other, and can support the auxiliary hammer 21 stably.

In the rotary impact tool 1, the number of steel balls 17 may be three or more. By providing three or more second cam structures, the rotary impact tool 1 can suppress wear of the steel balls 17 while ensuring the coaxiality between the auxiliary hammer 21 and the spindle 11. Even when four or more second cam structures are provided, it is preferable that the sub hammer 21 is stably supported by the plurality of steel balls 17 being positioned at equal intervals in the circumferential direction.

<Comparison of the movable range in the circumferential direction of the first cam structure and the second cam structure of the embodiment. In the embodiment, two first cam structures are provided side by side in the circumferential direction on the outer peripheral surface of the spindle 11 having a smaller diameter than the carrier 16. Therefore, when the two first guide grooves 11b are formed over substantially the entire circumference of the outer peripheral surface of the spindle 11, the circumferential movable range of one inclined groove of the first guide groove 11b is approximately 90 degrees. On the other hand, three second cam structures are provided side by side in the circumferential direction on the outer periphery of the front surface of the carrier 16 having a diameter larger than that of the spindle 11. Therefore, if the three second guide grooves 16a are formed over substantially the entire circumference of the front surface of the carrier 16, the circumferential movable range of one inclined groove of the second guide groove 16a is approximately 60 degrees.

As described above, the circumferential range of motion is narrower in the second cam structure. This means that the second cam structure reaches the movable limit earlier than the first cam structure. Therefore, in the rotary impact tool 1, the first cam structure and the second cam are arranged so that the engagement between the hammer claw 20a and the anvil claw 22b is released before the steel ball 17 moves to the movable limit in the second guide groove 16a. A structure is formed.

Hereinafter, the reason why the second guide groove 16a of the second cam structure is formed in the carrier 16 having a larger diameter than the spindle 11 in which the first guide groove 11b of the first cam structure is formed will be described. Since the rotary impact tool 1 is an electric tool that is used by a user by hand, there is a great demand for reduction in size and weight. If the structure in which three second guide grooves 16a are formed on the outer peripheral surface of the spindle 11 and the three steel balls 17 support the auxiliary hammer 21 in the radial direction is adopted, the strength of the spindle 11 is insufficient. It is necessary to thicken itself. However, increasing the diameter of the spindle 11 is not preferable because it does not meet the demand for reduction in size and weight. In this structure, it is also conceivable that the steel ball 17 is made smaller than the steel ball 19 to reduce the amount of lightening by forming the three second guide grooves 16a, thereby preventing the strength of the spindle 11 from being insufficient. However, by reducing the size of the steel ball 17, there is a problem that the strength of the steel ball 17 becomes a problem this time, and the manufacturing cost increases because two types of steel balls are required.

Therefore, in the rotary impact tool 1, the second guide groove 16 a is formed in the carrier 16 having a diameter larger than that of the spindle 11 to solve the above problem. A large-diameter portion having an outer diameter larger than that portion may be provided on the rear side of the portion where the first guide groove 11b of the spindle 11 is formed, and the second guide groove 16a may be formed in the large-diameter portion. In this case, the spindle 11 has a small diameter portion in which the first guide groove 11b is formed and a large diameter portion in which the second guide groove 16a is formed. At this time, since the spindle 11 has a large diameter portion, the weight of the spindle 11 is slightly increased, but at the same time, the strength of the carrier 16 is increased. Therefore, when sufficient durability can be expected, the carrier 16 is thinned (lightened). Thus, the tool weight may not be increased.

FIG. 9 is a schematic cross-sectional view of the rotary impact mechanism when the steel ball moves in the first cam structure and the second cam structure. In this example, the main hammer 20 moves backward by the movement amount M with respect to the spindle 11, and the auxiliary hammer 21 moves forward by the movement amount N with respect to the carrier 16. As described with reference to FIG. 6B, when the movement amount M of the main hammer 20 reaches a distance corresponding to the maximum engagement length between the hammer claws 20a and the anvil claws 22b, the engagement between the hammer claws 20a and the anvil claws 22b. The match is released. As described above, before the movement amount N of the secondary hammer 21 reaches the movable limit, the movement amount M of the main hammer 20 reaches a distance corresponding to the maximum engagement length between the hammer claw 20a and the anvil claw 22b. The first cam structure and the second cam structure are formed.

The movement amount M of the main hammer 20 in the rotation axis direction and the movement amount N of the sub hammer 21 in the rotation axis direction are respectively defined by the shapes of the first cam structure and the second cam structure. Since the ratio of the amount of movement for canceling the vibration in the axial direction preferably depends on the mass ratio of the main hammer 20 and the secondary hammer 21, the shapes of the first cam structure and the second cam structure are the main hammer. It is designed according to the mass ratio between 20 and the secondary hammer 21. Hereinafter, the mass of the main hammer 20 is P, and the mass of the auxiliary hammer 21 is Q. The mass P is smaller than the mass Q.

In the embodiment, the first cam structure and the second cam groove 16a so that the movable range in the rotation axis direction of the steel ball 17 is smaller than the movable range in the rotation axis direction of the steel ball 19 in the first guide groove 11b. A second cam structure is formed. This is because the mass Q of the secondary hammer 21 is larger than the mass P of the primary hammer 20, and vibrations caused by the movement of the primary hammer 20 in the rotational axis direction are opposite to the secondary hammer 21 having a large mass and have a small stroke. The purpose is to cancel the vibration caused by the movement. Specifically, the ratio of the movable range in the rotation axis direction of the steel ball 17 and the movable range in the rotation axis direction of the steel ball 19 is substantially equal to the ratio of the mass P of the main hammer 20 and the mass Q of the auxiliary hammer 21. May be set.

By forming the first cam structure and the second cam structure in this way, the length of the inclined groove of the second guide groove 16a in the rotational axis direction is made longer than the length of the inclined groove of the first guide groove 11b in the rotational axis direction. Can also be shortened. This realizes a shorter axis of the tool body and contributes to reducing the size and weight of the rotary impact tool 1.

Although the above description is about the movable range in the rotation axis direction, the shape of the inclined groove in the movable range in the first cam structure and the second cam structure is determined by the design concept. That is, the ratio of the movement amount N of the secondary hammer 21 relative to the carrier 16 to the movement amount M of the primary hammer 20 relative to the spindle 11 is substantially equal to the ratio of the mass P of the primary hammer 20 and the mass Q of the secondary hammer 21. First, the first cam structure and the second cam structure are formed. Thereby, it acts so that the vibration of the rotation axis direction by the main hammer 20 and the sub hammer 21 may mutually cancel, and it becomes possible to improve a user's workability | operativity.

The outline of one embodiment of the present invention is as follows.
A rotary impact tool (1) according to an aspect of the present invention includes a drive unit (10), a spindle (11) rotated by the drive unit, and a rotation axis of the spindle that is rotatable about the rotation axis. A first hammer structure in which a first steel ball (19) is disposed between a main hammer (20), a first guide groove (11b) on the spindle side, and a first engagement groove (20b) on the main hammer side; An anvil (22) to which a rotational hammering force is applied by the main hammer, an auxiliary hammer (21) that can rotate integrally with the main hammer, and a spindle provided on the rear side of the first guide groove and formed with the first guide groove A second steel ball (16) between a large diameter portion (16) having an outer diameter larger than the second portion and a second guide groove (16a) on the large diameter portion side and a second engagement groove (21f) on the sub hammer side. 17) with a second cam structure. The rotary impact tool of this aspect is configured such that when the main hammer moves in the rotation axis direction, the sub hammer moves in the direction opposite to the movement direction of the main hammer.

The large diameter portion may be a carrier (16) that is located on the rear end side of the spindle and accommodates a power transmission gear. The spindle (11) may have a small diameter part in which the first guide groove is formed and a large diameter part in which the second guide groove is formed. In the rotary impact tool (1), it is preferable that the mass of the sub hammer (21) is larger than the mass of the main hammer (20).

In the rotary impact tool (1), the movable range of the second steel ball (17) in the second guide groove (16a) in the rotation axis direction is the rotation axis of the first steel ball (19) in the first guide groove (11b). A 1st cam structure and a 2nd cam structure may be formed so that it may become smaller than the movable range of a direction. The ratio of the movable range in the rotation axis direction of the second steel ball and the movable range in the rotation axis direction of the first steel ball may be set substantially equal to the ratio of the mass of the main hammer and the mass of the auxiliary hammer. The secondary hammer may house the primary hammer. The auxiliary hammer may be supported so as to be rotatable about the rotation axis by circumscribing the auxiliary hammer to the main hammer. The first steel ball and the second steel ball may be configured to have the same size.

The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to each component or combination of each processing process, and such modifications are within the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 ... Rotary impact tool, 2 ... Housing, 11 ... Spindle, 11b ... 1st guide groove, 12 ... Power transmission mechanism, 16 ... Carrier, 16a ... 2nd guide Groove, 16b ... front side member, 17, 19 ... steel ball, 20 ... main hammer, 20a ... hammer claw, 20b ... first engagement groove, 21 ... sub hammer, 21e ... Annular partition, 21f ... Second engagement groove, 22 ... Anvil, 22b ... Anvil claw, 23 ... Spring member.

The present invention can be used for a tool such as a rotary impact tool.

Claims

A drive unit; a spindle rotated by the drive unit; a main hammer rotatable about a rotation axis of the spindle and movable in the direction of the rotation axis; a first guide groove on the spindle side; and a main hammer side A first cam structure in which a first steel ball is disposed between the first engagement groove, an anvil to which a rotational striking force is applied by the main hammer, a secondary hammer rotatable integrally with the main hammer, A large-diameter portion that is provided on the rear side of one guide groove and has a larger outer diameter than the portion of the spindle on which the first guide groove is formed; a second guide groove on the large-diameter portion side; and a sub-hammer side A second cam structure in which a second steel ball is disposed between the second engagement groove,
The rotary hammering tool is configured such that when the main hammer moves in the rotation axis direction, the sub hammer moves in a direction opposite to the movement direction of the main hammer.
The large-diameter portion is a carrier that is positioned on the rear end side of the spindle and accommodates a power transmission gear.
The rotary impact tool according to claim 1.
The spindle has a small diameter portion in which the first guide groove is formed and the large diameter portion in which the second guide groove is formed.
The rotary impact tool according to claim 1.
The mass of the secondary hammer is greater than the mass of the primary hammer,
The rotary impact tool according to any one of claims 1 to 3.
The movable range in the rotation axis direction of the second steel ball in the second guide groove is smaller than the movable range in the rotation axis direction of the first steel ball in the first guide groove.
The rotary impact tool according to any one of claims 1 to 4.
The ratio of the movable range in the rotation axis direction of the second steel ball to the movable range in the rotation axis direction of the first steel ball is set substantially equal to the ratio of the mass of the main hammer and the mass of the secondary hammer. To be
The rotary impact tool according to claim 5.
The secondary hammer houses the primary hammer;
The rotary impact tool according to any one of claims 1 to 6.
The first steel ball and the second steel ball have the same size,
The rotary impact tool according to any one of claims 1 to 7.