Impact tool

Abstract

To provide an impact tool which makes it difficult for striking force to be transmitted to a user's hand to achieve good usability.SOLUTION: An impact tool includes: a motor 1; a hammer 2 which is rotated by the motor 1; an anvil 3 which is struck by the hammer 2; and a case 4 which houses the motor 1, the hammer 2, and at least part of the anvil 3. A hammer receiving part 31 which receives striking from the hammer 2, a power transmission part 32 which transmits power received by the hammer receiving part 31 forward, and a bit support part 33 or a socket which receives power from the power transmission part 32 to rotate are arranged from the rear to the front in an axial direction in a written order to form the anvil 3. The power transmission part 32 and the bit support port 33 or the socket are connected with an allowance formed in a rotation direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an impact tool such as an impact driver, an impact wrench, or an impact ratchet. [Background technology]

[0002] Patent document 1 discloses an impact type screw fastener that includes a hammer and an anvil, rotates the hammer using the power of a motor, and the rotating hammer strikes the anvil, thereby applying a rotational striking force to a screw fastener bit attached to the anvil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4754395 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, every time the hammer strikes the anvil, the striking force is transmitted to the user's hand, causing discomfort to the user, and there is room for improvement.

[0005] An object of the present invention is to provide an impact tool which is easy to use and in which striking force is not easily transmitted. [Means for solving the problem]

[0006] The impact tool of the present invention comprises a motor, a hammer rotated by the motor, an anvil struck by the hammer, and a case that houses the motor, the hammer, and at least a part of the anvil, and the anvil is configured such that, from rear to front in the axial direction, the anvil is arranged in the following order: a hammer receiving portion that receives the strike from the hammer, a power transmission portion that transmits the power received by the hammer receiving portion to the front, and a bit support portion or socket that rotates upon receiving power from the power transmission portion, and the power transmission portion and the bit support portion or socket are connected with play in the rotational direction.

[0007] With this configuration, the power transmission unit and the bit support unit or socket are connected with some play in the rotational direction, so that vibrations generated by the impact force of the hammer receiving unit that receives the strike from the hammer are less likely to be transmitted from the power transmission unit to the bit support unit or socket, thereby reducing the vibrations transmitted to the user's hands.

[0008] In the impact tool of the present invention, the power transmission portion and the bit support portion or the socket may be made of different materials or have different hardnesses.

[0009] This configuration makes it easy to select the materials for the power transmission part and the bit support part or socket. For example, if the hardness of the power transmission part is made lower than the hardness of the bit support part or socket, the vibration transmitted to the user's hand can be further reduced.

[0010] In addition, the impact tool of the present invention may further include an intervening portion, and a space for providing the intervening portion may be formed between a side surface of the power transmission portion and an inner surface of a fixed portion arranged radially outward of the power transmission portion and fixed to the case, and the space may include a movement region in which the intervening portion can move circumferentially, and a bite region in which the intervening portion is bitten between the side surface of the power transmission portion and the inner surface of the fixed portion.

[0011] According to this configuration, the interposition portion bites into the biting region, thereby fixing the power transmission portion and the bit support portion to the case, whereby the case can be rotated by hand to rotate the bit attached to the bit support portion, thereby further tightening the screw.

[0012] In the impact tool of the present invention, the bit support portion may be a substantially cylindrical body configured to have a uniform outer diameter at the same axial position.

[0013] According to this configuration, if the bit support portion is a substantially cylindrical body configured to have the same outer diameter at the same axial position, it is possible to achieve uniform strength in the circumferential direction.

[0014] In addition, in the impact tool of the present invention, the front end of the power transmission part is inserted into and connected to the axial rear end of the bit support part, and the axial rear end of the bit support part may have a larger radial dimension than other parts.

[0015] According to this configuration, if the axial rear end of the bit support portion has a larger radial dimension than other portions, a sufficient thickness can be ensured and the rotational force from the power transmission portion can be reliably transmitted to the bit support portion. Effect of the Invention

[0016] As described above, by connecting the power transmission unit and the bit support unit or the socket with play in the rotational direction, it is possible to provide an impact tool that is easy to use as it makes it difficult for impact force to be transmitted. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a side view, partially in cross section, of the impact driver. [Diagram 2] 4 is an exploded perspective view of components constituting an impact mechanism provided in a case. FIG. [Diagram 3] FIG. [Figure 4]11 is a cross-sectional view seen from behind, showing a state in which the motor is rotated forward in an unlocked state. FIG. [Diagram 5] FIG. 11 is a cross-sectional view seen from behind, showing the locked state when tightened by hand. [Figure 6] This is a cross-sectional view from the rear showing the locked state when returning (loosening). [Figure 7] 11 is a cross-sectional view seen from behind, showing a state immediately before the locked state is released by rotating the motor in the reverse direction. FIG. [Figure 8] 11 is a cross-sectional view of the main part of the power transmission section as viewed from behind, showing another embodiment of the power transmission section. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of an impact driver, which is an impact tool of the present invention, will be described with reference to the drawings.

[0019] As shown in Fig. 1, the impact driver includes a motor 1 having a rotating output shaft 1A, a hammer 2 rotated by the motor 1, an anvil 3 struck by the hammer 2, and a case 4 that houses at least a part of the motor 1, the hammer 2, and the anvil 3. The case 4 may be configured as two separate cases divided left and right (or top and bottom). In this embodiment, the impact driver is a battery-powered type that rotates the motor 1 using a battery (not shown) such as a secondary battery that supplies power, but it may also be configured to rotate the motor 1 using power from a commercial AC power source. In Fig. 1, the left side (tip) of the impact driver is the front side, and the base end side (right side) of the impact driver is the rear side.

[0020] The impact driver in FIG. 1 is configured in a generally cylindrical shape extending in a straight line from the front end with the bit support part 33 to the rear end where the battery and the like are stored. Such a generally cylindrical impact driver can be securely stored in a driver sack carried by the worker on the waist, and is excellent in portability, as it can be easily inserted and removed. In contrast, in a generally L-shaped impact driver having a main body part that contains a motor and a rotary impact mechanism part, and a grip part that contains a battery and the like attached to the rear end of the main body part so as to extend in a direction intersecting with the main body part, when the main body part is inserted into the driver sack carried by the worker, the grip part protrudes from the driver sack. This causes the inconvenience of the protruding grip part hitting something when the worker passes by, or the protruding grip part hitting something and dropping it from the driver sack.

[0021] The impact driver (impact tool) has an impact mechanism that increases the fastening force of the screw by striking the anvil 3 with the hammer 2. The vibrations generated by this impact mechanism are due to the impact between metals, and vibrations are generated for each strike. The hammer 2 is axially biased by a coil spring 7, which will be described later, and when a load of a predetermined level or more is applied to the anvil 3, the hammer 2 moves axially against the biasing force of the coil spring 7. When the hammer 2 moves beyond a predetermined level, the hammer 2 becomes rotatable relative to the anvil 3, and strikes the anvil 3 by the biasing force of the coil spring 7. In the impact driver (impact tool) configured in this way, when the hammer 2 strikes the anvil 3 in a rotational direction that increases the fastening force of the screw, vibrations in the rotational direction are generated, while axial vibrations acting in the axial direction of the anvil 3 are also generated, resulting in large vibrations.

[0022] The anvil 3 is configured so that, from rear to front in the axial direction, a hammer receiving portion 31 that receives the impact from the hammer 2, a power transmission portion 32 that transmits the power received by the hammer receiving portion 31 forward, and a bit support portion 33 that supports a bit (not shown) that rotates by receiving power from the power transmission portion 32 are arranged in that order.

[0023] An output shaft 1A of the motor 1 is connected to a planetary gear reduction mechanism (not shown), and an output from the planetary gear reduction mechanism (not shown) is transmitted to a drive shaft 5 to rotate the drive shaft 5. As shown in Fig. 2, the rear end of a cylindrical coupling part 32A extending rearward from the rear end of the power transmission part 32 is fitted into a fitting hole 5A formed in the front end part of the drive shaft 5, whereby the drive shaft 5 and the power transmission part 32 are connected to be able to rotate together.

[0024] As shown in Fig. 2, the hammer 2 has a through hole 2A for passing the drive shaft 5, and steel balls 6, 6 are sandwiched between engagement grooves 2M, 2M formed in this through hole 2A and engagement grooves 5M, 5M formed on the outer circumferential surface of the drive shaft 5. With this configuration, the hammer 2 is configured to be movable in the axial direction (front-rear direction) of the drive shaft 5, and is also configured to be rotatable relative to the drive shaft 5. Striking portions 2D that protrude forward are provided at two locations on the outer periphery of the front surface of the hammer 2. The striking portions 2D, 2D are formed at positions that divide the outer periphery of the hammer 2 into two equal parts.

[0025] Furthermore, a disk-shaped flange 5F is provided at the rear end of the drive shaft 5, and a coil spring 7 for urging the hammer 2 forward is provided between the flange 5F and the hammer 2. A sliding member 8 for allowing the coil spring 7 to rotate relatively to the hammer 2 is provided between the front end of the coil spring 7 and the hammer 2. The sliding member 8 includes a ring-shaped plate member 8A that receives the front end of the coil spring 7, and a number of spheres 8B that are interposed between the plate member 8A and the hammer 2 along the circumferential direction.

[0026] 2, the hammer receiving portion 31 has a through hole 31A for passing the connecting portion 32A of the power transmission portion 32 therethrough, and is held so as to be rotatable within a certain range relative to the power transmission portion 32. The hammer receiving portion 31 has impact receiving portions 31B, 31B protruding radially outward to receive impacts from the striking portions 2D, 2D of the hammer 2 at positions that divide the outer periphery of the hammer receiving portion 31 into two equal parts.

[0027] Furthermore, transmission parts 31C, 31C, 31C (see FIG. 2) for transmitting power to the power transmission part 32 protrude forward from the front surface of the outer periphery of the hammer receiving part 31 at positions dividing the outer periphery into three equal parts.

[0028] As shown in Fig. 4, the power transmission part 32 has power receiving parts 32B that receive power (rotational force) from the transmission parts 31C, 31C, 31C, which are formed to protrude radially outward at positions that divide the outer circumference of the outer circumference of the rear end part into three equal parts. The power receiving parts 32B are disposed between the transmission parts 31C, 31C that are adjacent to each other in the circumferential direction. The power transmission part 32 also has an outer circumferential surface 320 between the power receiving parts 32B, 32B that are adjacent to each other in the circumferential direction, and thus has three outer circumferential surfaces 320, 320, 320 in total. The hardness of the power transmission part 32 is lower than the hardness of the striking parts 2D, 2D of the hammer 2, the hardness of the hammer receiving part 31, and the hardness of the bit support part 33. For example, the hardness (Rockwell hardness) of the power transmission part 32 is 40HRC, and the hardness (Rockwell hardness) of the striking parts 2D, 2D, the hammer receiving part 31, and the bit support part 33 of the hammer 2 is 48HRC. In this embodiment, the hardness of the striking parts 2D, 2D, the hammer receiving part 31, and the bit support part 33 of the hammer 2 is the same, but they may be different in hardness. If the hardness of the power transmission part 31 is lower than that of the hammer receiving part 31 as described above, vibration is less likely to be transmitted from the hammer receiving part 31 to the power transmission part 32. Also, if the hardness of the power transmission part 31 is lower than that of the bit support part 33, vibration is less likely to be transmitted from the power transmission part 32 to the bit support part 33. Therefore, it is possible to reduce the vibration transmitted to the user's hand. As a result, even if the case 4 near the motor 1, which is also subjected to the vibration of the motor 1, is gripped, vibration is less likely to be transmitted to the hand.

[0029] 1 and 4, a ring-shaped fixed portion 9 surrounding the power receiving portions 32B, 32B, 32B of the power transmission portion 32 is provided on the outside of the power receiving portions 32B, 32B, 32B of the power transmission portion 32. The fixed portion 9 is fixed to the case 4 so as not to rotate. A small gap is formed between the inner peripheral surface 9A of the fixed portion 9 and the outer surfaces 32b, 32b, 32b of the power receiving portions 32B, 32B, 32B so as not to hinder the rotation of the power transmission portion 32.

[0030] Moreover, on both circumferential sides of each transmission part 31C, spaces 10, 10 are formed between the power receiving parts 32B, 32B. A total of six spaces 10 are formed. An intermediate part 11A, 11B is disposed in each of the six spaces 10. The intermediate parts 11A, 11B are configured in a shape that is movable in the circumferential direction, specifically, in a cylindrical shape (or may be spherical) that rotates in the circumferential direction. Furthermore, the axial direction of the rotation center of the intermediate parts 11A, 11B when they move in the circumferential direction is parallel to the axis of the drive shaft 5. 4, when the motor 1 is driven in the forward direction, the transmission parts 31C, 31C, 31C rotate in the direction of the arrow (clockwise), so that the transmission parts 31C, 31C, 31C abut against the three intermediate parts 11B, 11B, 11B located downstream in the rotation direction, and the three intermediate parts 11B, 11B, 11B further abut against the power receiving parts 32B, 32B, 32B. As a result, the rotational force of the transmission parts 31C, 31C, 31C is transmitted to the power receiving parts 32B, 32B, 32B via the intermediate parts 11B, 11B, 11B, and the power transmission part 32 rotates, causing the bit support part 33 to rotate in the forward direction. 4 (counterclockwise), the transmission parts 31C, 31C, 31C come into contact with the three intermediate parts 11A, 11A, 11A on the opposite side to the intermediate part located downstream in the rotation direction of the transmission parts 31C, 31C, 31C, and the three intermediate parts 11A, 11A, 11A further come into contact with the power receiving parts 32B, 32B, 32B. As a result, the rotational force of the transmission parts 31C, 31C, 31C is transmitted to the power receiving parts 32B, 32B, 32B via the intermediate parts 11A, 11A, 11A, and the power transmission part 32 rotates, causing the bit support part 33 to rotate in the reverse direction.

[0031] As shown in FIG. 4, each space 10 has a movement region 12 in which the interposed portions 11A, 11B can move circumferentially, and a clamping region 13 in which the interposed portions 11A, 11B are clamped between the outer peripheral surface 320 of the power transmission portion 32 and the inner peripheral surface 9A of the fixed portion 9, thereby preventing them from moving circumferentially.

[0032] The bite region 13 is formed at both circumferential ends of a central outer peripheral surface 3201 that is located at the approximate center of the circumferential direction of each outer peripheral surface 320 and is configured as a curved surface that is convex outward. The movement region 12 is formed between the power receiving portion 32B side end of the bite region 13 and the abutment surface 14 with which the interposed portions 11A, 11B of the power receiving portion 32B abut. Specifically, the movement region 12 includes an end outer peripheral surface 3202 that is configured as a curved surface that is recessed inwardly to the outer peripheral surface 320 of the power transmission portion 32, and an extended outer peripheral surface 3203 that is configured as a curved surface that is recessed inwardly continuously from the power receiving portion 32B side end of the end outer peripheral surface 3202 to the abutment surface 14 of the power receiving portion 32B.

[0033] The moving area 12 has an end outer peripheral surface 3202 formed to be recessed inward on the outer peripheral surface 320 of the power transmission part 32, so that the space 10 can be increased in the radial direction, and accordingly, the intermediate parts 11A, 11B having a large diameter, which is advantageous in terms of power transmission, can be used. This improves the freedom of design. In addition, the moving area 12 has an extended outer peripheral surface 3203 formed continuously from the power receiving part 32B side end of the end outer peripheral surface 3202 to the abutment surface 14 of the power receiving part 32B, so that when the intermediate parts 11A, 11B abut against the power receiving part 32B, they can abut on each other by surface, and therefore the impact force applied from the intermediate parts 11A, 11B to the power receiving part 32B can be dispersed.

[0034] The bit support portion 33 is provided with a through hole 33A (see Figs. 2 and 3) that is hexagonal when viewed from the front and into which a bit (not shown) can be inserted, and is configured as a substantially cylindrical body configured to have the same outer diameter at the same axial position. If the bit support portion 33 is thus configured as a substantially cylindrical body configured to have the same outer diameter at the same axial position, it can have uniform strength in the circumferential direction.

[0035] 2 and 3, the axial rear end of the bit support part 33 is provided with a large diameter part 330 whose radial dimension is larger than other parts. If the axial rear end of the bit support part 33 has a radial dimension larger than other parts in this way, there is an advantage that a wall thickness is ensured compared to other parts, and the rotational force from the power transmission part 32 can be reliably transmitted to the bit support part 33. Furthermore, the inner surface 330A of the large diameter part 330 is formed in a regular hexagonal shape so that it can be inserted into and connected to the regular hexagonal front end part 32F of the power transmission part 32.

[0036] 3, the inner diameter dimension of the large diameter portion 330 is set to be larger than the outer diameter dimension of the power transmission portion 32. As a result, there is a play in the rotational direction between the inner surface 330A of the large diameter portion 330 and the outer surface 32f of the front end portion 32F of the power transmission portion 32. Specifically, the length (maximum inner diameter) of the line connecting two opposing vertices of the large diameter portion 330 is 9.14 mm, and the length (minimum inner diameter) of the line connecting two opposing sides of the large diameter portion 330 is 8.00 mm, whereas the length (maximum outer diameter) of the line connecting two opposing vertices of the power transmission portion 32 is 8.97 mm, and the length (minimum outer diameter) of the line connecting two opposing sides of the power transmission portion 32 is 7.90 mm. In this manner, the bit support portion 33 and the power transmission portion 32 are connected with some play in the rotational direction, so that vibrations generated by the striking force of the hammer receiving portion 31, which receives the strike from the hammer 2, are less likely to be transmitted from the power transmission portion 32 to the bit support portion 33, thereby reducing the vibrations transmitted to the user's hands.

[0037] On the outside of the bit support portion 33, a chuck 15 (see FIG. 1) is provided for removably fixing a bit (not shown) inserted into the bit support portion 33.

[0038] In addition, the bit support part 33 and the power transmission part 32 are made of different materials. Specifically, the bit support part 33 is formed by forging iron or a forged material whose main component is iron, thereby improving productivity. In addition, the power transmission part 32 is made of iron-based alloy powder or copper-based alloy powder, and is molded by injection molding, thereby improving processing accuracy. In this way, by making the bit support part 33 and the power transmission part 32 out of different materials, it is easy to select the materials for the bit support part 33 and the power transmission part 32.

[0039] When driving motor 1 to tighten or loosen the screws, intervening portions 11A, 11B function as transmission members that transmit the rotational force from transmission portion 31C to power receiving portion 32B, and when it is desired to manually tighten or loosen the screws, intervening portions 11A, 11B function as locking members that get caught between power transmission portion 32 and fixed portion 9 to prevent rotation of power transmission portion 32.

[0040] When the motor 1 of the impact driver is driven to tighten the screw, the motor 1 is driven in the forward direction, and as shown in Fig. 4, the transmission parts 31C, 31C, 31C rotate clockwise (in the direction of the arrow), so that the transmission parts 31C, 31C, 31C abut against the three intermediate parts 11B, 11B, 11B located downstream in the rotation direction, and the three intermediate parts 11B, 11B, 11B further abut against the power receiving parts 32B, 32B, 32B. As a result, the rotational force of the transmission parts 31C, 31C, 31C is transmitted to the power receiving parts 32B, 32B, 32B via the intermediate parts 11B, 11B, 11B, and the power transmission part 32 rotates to rotate the bit support part 33 in the forward direction. At this time, the remaining three intermediate parts 11A, 11A, 11A that do not transmit power are located in the moving area 12 and do not hinder the rotation of the power transmission part 32. When using an impact driver to loosen the screws, the operation is the same as when the motor 1 is rotating in the normal direction, except that the rotation direction of the motor 1 is reversed (counterclockwise), so a description thereof will be omitted.

[0041] When manually tightening the screws, as shown in FIG. 5, when the motor 1 is stopped, the case 4 (not the case 4 in FIG. 5, but the fixed part 9 fixed to the case 4) is rotated clockwise as indicated by the arrow, the intermediate part 11A on the upstream side in the rotation direction of the intermediate parts 11A and 11B located on both sides in the circumferential direction of each transmission part 31C is rotated by the rotation of the case 4 (fixed part 9) and moves to the biting area 13 on the downstream side in the rotation direction, where the intermediate part 11A is bitten between the outer peripheral surface 320 of the power transmission part 32 and the inner peripheral surface 9A of the fixed part 9. This prevents the power transmission part 32 from rotating, and the case 4 can be manually rotated clockwise to tighten the screws. At this time, the intermediate part 11B on the downstream side in the rotation direction of the intermediate parts 11A and 11B maintains its position in the moving area 12.

[0042] When the screw is loosened manually, as shown in FIG. 6, when the motor 1 is stopped, the case 4 (not the case 4 in FIG. 6, but the fixed part 9 fixed to the case 4) is rotated counterclockwise as indicated by the arrow, the intermediate part 11B on the upstream side in the rotation direction of the intermediate parts 11A and 11B located on both sides in the circumferential direction of each transmission part 31C is rotated by the rotation of the case 4 and moves to the biting area 13 on the downstream side in the rotation direction, and the intermediate part 11B is bitten between the outer peripheral surface 320 of the power transmission part 32 and the inner peripheral surface 9A of the fixed part 9. This prevents the power transmission part 32 from rotating, and the case 4 is rotated counterclockwise by hand to loosen the screw. At this time, the intermediate part 11A on the downstream side in the rotation direction of the intermediate parts 11A and 11B is maintained in the moving area 12.

[0043] When it is desired to release the state in which the interposed portion 11A shown in FIG. 5 is engaged between the outer peripheral surface 320 of the power transmission portion 32 and the inner peripheral surface 9A of the fixed portion 9, the motor 1 is rotated in the reverse direction (counterclockwise) to move the engaged interposed portion 11A to the moving region 12 as shown in FIG. 7, thereby releasing the engaged state.

[0044] Incidentally, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit and scope of the present invention.

[0045] In the above embodiment, an impact driver is shown as an impact tool, but an impact wrench or impact ratchet may also be used. In the case of an impact wrench or impact ratchet, a socket having a hexagonal or dodecagonal hole for fitting onto a bolt or nut to perform a tightening or loosening operation is connected to the power transmission part instead of the bit support part of the impact driver.

[0046] In the above embodiment, the engagement region 13 is set in a narrow range at the boundary between the inwardly recessed movement regions 12, 12 and the outer circumferential surface 320 configured as a curved surface that is outwardly protruding, but as shown in Fig. 8, a straight portion 16 having a predetermined distance in the circumferential direction may be formed between the movement region 12 and the outer circumferential surface 320, and the straight portion 16 may be used as the engagement region 13. In this way, the intermediate portion 11A or 11B can be reliably engaged with the straight portion 16. [Explanation of symbols]

[0047] 1...motor, 1A...output shaft, 2...hammer, 2A...through hole, 2D...striking portion, 2M...engagement groove, 3...anvil, 4...case, 5...drive shaft, 5A...fitting hole, 5F...flange, 5M...engagement groove, 6...steel ball, 7...coil spring, 8...sliding member, 8A...plate member, 8B...sphere, 9...fixed portion, 9A...inner surface, 10...space, 11A, 11B...intervening portion, 12...moving region, 13...engaging region, 14 ...contact surface, 15...chuck, 16...straight section, 31...hammer receiving section, 31A...through hole, 31B...impact receiving section, 31C...transmission section, 32...power transmission section, 32A...connection section, 32B...power receiving section, 32F...front end section, 32b...outer surface, 32f...outer surface, 33...bit support section, 33A...insertion hole, 320...outer peripheral surface, 330...large diameter section, 330A...inner surface, 3202...end outer peripheral surface, 3203...extended outer peripheral surface

Claims

1. The invention comprises a motor, a hammer rotated by the motor, an anvil struck by the hammer, and a case that houses the motor, the hammer, and at least a portion of the anvil, The anvil is configured such that, from the rear to the front in the axial direction, a hammer receiving portion that receives the impact from the hammer, a power transmission portion that transmits the power received by the hammer receiving portion to the front, and a bit support portion or a socket that rotates by receiving the power from the power transmission portion are arranged in this order, An impact tool, wherein the power transmission portion and the bit support portion or the socket are connected with play in a rotational direction.

2. The impact tool according to claim 1 , wherein the power transmission portion and the bit support portion or the socket are made of different materials or have different hardnesses.

3. The impact tool of claim 1 or 2, further comprising an intervening portion, wherein a space for providing the intervening portion is formed between a side surface of the power transmission portion and an inner surface of a fixed portion arranged radially outward of the power transmission portion and fixed to the case, the space comprising a movement region in which the intervening portion can move circumferentially, and a bite region in which the intervening portion is bitten between the side surface of the power transmission portion and the inner surface of the fixed portion.

4. 3. The impact tool according to claim 1, wherein the bit support portion is a substantially cylindrical body configured to have a uniform outer diameter at a uniform axial position.

5. 3. The impact tool according to claim 1 or 2, wherein the front end of the power transmission part is inserted into and connected to the axial rear end of the bit support part, and the axial rear end of the bit support part has a larger radial dimension than other parts.

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