impact tools

Abstract

In the impact tool of the present invention, a tapered portion is provided on the outer circumference of the front surface of the hammer to reduce the stress applied to the striking claw during impact. The impact tool of the present invention comprises a hammer rotated by a motor and pushed forward from a rotating shaft by a cam mechanism and a spring; and an anvil struck by the hammer. The hammer comprises a body and a claw extending forward from the body, with the tapered surface formed such that the inner diameter end of the claw of the body is located further forward than the outer diameter end of the claw. The tapered surface is formed on the outer circumference of the front facing surface of the hammer and is shaped to recede radially as it moves away from the rotation axis.

Description

Technical Field

[0001] The present invention relates to an impact tool for fastening fasteners such as screws or bolts. Background Art

[0002] As a striking tool for tightening screws, etc., the following impact tool is known, which utilizes a motor to drive a rotating striking mechanism portion, applies rotation and striking to an anvil, and intermittently transmits the rotating striking force to the front end tool to perform operations such as screw tightening. The impact tool includes a motor, a power transmission mechanism connected to the motor, and a front end tool connected to the power transmission mechanism. The operator connects the front end tool to a fastener such as a screw, rotates the motor, and the impact tool tightens the fastener while striking. As such an impact tool, the technology of Patent Document 1 is known. In Patent Document 1, as a power transmission mechanism, there is a striking mechanism that converts a rotating force into a striking force in a rotational direction, and the striking mechanism is provided with three anvils that output a rotating force to the front end tool, and a collision part (claw) of a hammer that imparts a striking force to the anvil.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2016 / 002539 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] With the recent increase in the output of impact tools, the industry has sought to strengthen power sources such as battery packs or improve the performance of motors. As a result, mechanical components such as the striking mechanism cannot fully withstand the output of the motor, and the concern of damage has increased. Therefore, sufficient countermeasures are needed to address this situation. As a countermeasure for damage to mechanical components, it is considered to change the material and shape of the hammer or anvil. For example, the hammer claw and the anvil wing were previously two sets, but the technology of Patent Document 1 has increased this to three sets. By increasing the number of hammer claws and anvil wings to three sets, the contact points during striking are dispersed at three locations along the circumferential direction, thereby reducing the force applied to each contact point. However, on the other hand, if collision does not occur at all of these contact points at the same time, for example, if contact occurs at two locations instead of at three locations simultaneously, and the remaining location contacts with a slight delay, a significant stress is generated near the outer diameter end of the hammer claw base. As a countermeasure for this, measures such as forming a groove with a large curvature radius R at the base of the hammer claw or chamfering the end of the hammer claw are implemented. However, these measures increase the total length of the product or increase the amount of assembly processing work.

[0008] The present invention has been made in view of the above background, and its object is to provide an impact tool that reduces stress generated at the connection between the hammer body and the striking claw. Another object of the present invention is to provide an impact tool that shortens the overall length and improves workability.

[0009] Technical means to solve the problem

[0010] Representative features of the invention disclosed in this application are described below. According to one feature of the present invention, an impact tool includes: a motor; a rotating shaft driven by the motor in a rotational direction; a hammer capable of relative movement in an axial and rotational direction within a predetermined range relative to the rotating shaft and urged forward by a cam mechanism and a spring; and an anvil rotatably disposed in front of the hammer and struck by the hammer as the hammer moves forward and rotates. The hammer includes a main body and a claw extending forward from the main body, wherein the front inner diameter end of the main body is positioned forward of the front outer diameter end. The main body of the hammer includes a front wall, and the claw is configured to protrude from the front wall toward the anvil when viewed along the rotation axis. The hammer is configured such that the length L1 of the inner diameter end of the claw from the main body and the length L2 of the outer diameter end of the claw from the main body satisfy L1 < L2.

[0011] According to another feature of the present invention, a tapered surface is formed on the hammer body that gradually recedes as it moves away from the rotation axis. As described above, by configuring the claw portion so that part or all of it protrudes from the tapered surface toward the anvil, the relationship L1 < L2 can be achieved. Furthermore, grooves with a predetermined radius of curvature are formed at the circumferential corners connecting the hammer body and the claw portion.

[0012] According to yet another feature of the present invention, a plane orthogonal to the rotation axis is formed on the main body of the hammer, and the length D1 from the plane orthogonal to the rear end of the hammer in the axial direction is greater than the length D2 from the tapered surface to the rear end in the axial direction. This structure D1 > D2 is achieved by providing a tapered surface on the outer circumference of the front side of the hammer, excluding the claw portion.

[0013] According to another feature of the present invention, a spring support portion for supporting a spring is formed on the anti-anvil side of the hammer body, with the tapered surface starting radially outward from the radial center of the spring support portion. The cam mechanism comprises a shaft cam groove provided on the shaft; a hammer cam groove formed on the inner circumference of the hammer; a cam roller disposed between the shaft cam groove and the hammer cam groove; and a coiled spring disposed around the shaft to push the hammer toward the anvil in the direction of the rotation axis. Furthermore, the impact tool's motor is driven by a battery that can be used with a detachable power tool.

[0014] Effects of the Invention

[0015] According to the impact tool of the present invention, stress concentration near the outer diameter side end portion of the base of the hammer claw can be reduced, and the striking mechanism can be miniaturized. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a longitudinal sectional view showing the entire structure of the impact tool 1 according to the present embodiment.

[0017] Figure 2 yes Figure 1 A perspective view of the hammer 30 and the anvil 50.

[0018] Figure 3 yes Figure 2 The picture of Hammer 30, Figure 3 (A) is the front view, Figure 3 (B) is a longitudinal section view.

[0019] Figure 4 yes Figure 2 Figure 50 of the anvil, Figure 4 (A) is the front view, Figure 4 (B) is a longitudinal section view.

[0020] Figure 5 Yes Figure 1 A front view of the hammer 30 and the anvil 50 in a normal striking state.

[0021] Figure 6 This is a longitudinal section for comparing the shapes of the hammer 30 and anvil 50 of this embodiment with those of the conventional hammer 330 and anvil 350 . The upper half of the section, divided by the rotation axis A1 , represents the shape of this embodiment, while the lower half represents the conventional shape.

[0022] Figure 7 (A) is a front view showing the striking state of the hammer 30 and the anvil 50 when the hammer 30 and the anvil 50 are off-center. Figure 7 (B) is a cross-sectional view of the CC portion and a view viewed from the CC portion in the direction of the rotation axis A1.

[0023] Figure 8 yes Figure 7 Partially enlarged view of portion D in (B).

[0024] Figure 9 It is a perspective view of a hammer 130 and anvil 150 according to a second embodiment of the present invention.

[0025] Figure 10 FIG. 2 is a perspective view of a hammer 230 and an anvil 250 according to a third embodiment of the present invention.

[0026] Explanation of symbols

[0027] 1: Impact tool

[0028] 2: Shell

[0029] 2a: Main body

[0030] 2b: Handle

[0031] 2c: Battery installation part

[0032] 3: Motor

[0033] 3a: Rotor

[0034] 3b: stator

[0035] 4: Rotation axis

[0036] 5: Hammer Shell

[0037] 5a: Through hole

[0038] 7: Trigger switch

[0039] 7a: Trigger lever

[0040] 8: Forward and reverse switching lever

[0041] 9: Lighting device

[0042] 12: Inverter circuit board

[0043] 13: Position detection element

[0044] 14: Semiconductor switching elements

[0045] 15: Cooling fan

[0046] 16a, 16b: bearings

[0047] 18a, 18b: bearings

[0048] 19: Inner cover

[0049] 20: Speed ​​reduction mechanism

[0050] 21: Sun gear

[0051] 22: Planetary gear

[0052] 23: Ring gear

[0053] 25: Impact mechanism

[0054] 26: Shaft

[0055] 26a: Rotating shaft cam groove

[0056] 27: Steel Ball

[0057] 28: Hammer spring

[0058] 30: Hammer

[0059] 31: Body part

[0060] 31a: Outer cylinder part

[0061] 31b: Front surface connecting portion

[0062] 31c: Inner tube

[0063] 31d: Spring support

[0064] 32: Front facing surface

[0065] 32a: radially inner position (of the front facing surface)

[0066] 32b: Flat surface (orthogonal surface)

[0067] 33: Boundary position

[0068] 34a~34c:conical surface

[0069] 36, 37, 38: Hammer Claw

[0070] 36a, 37a, 38a: striking surface (when rotating forward)

[0071] 36b, 37b, 38b: Striking side (when spinning in reverse)

[0072] 36c, 38c: Outermost position (of hammer claw)

[0073] 39a, 39b: Hammer cam groove

[0074] 41a, 41b, 42a, 42b, 43a, 43b: Chamfered grooves

[0075] 45: Hitting point

[0076] 46: Root position (of the striking point)

[0077] 50: Anvil

[0078] 51: Spindle

[0079] 52: Thin diameter part

[0080] 52a: Through hole

[0081] 52b: Circumferential groove

[0082] 53: Assembly hole

[0083] 54: Flange

[0084] 55: shaft

[0085] 56, 57, 58: Wings

[0086] 56a, 57a, 58a: struck surface (when rotating in the forward direction)

[0087] 56b, 57b, 58b: struck side (when rotating in the opposite direction)

[0088] 60: Assembly mechanism

[0089] 61: Casing

[0090] 62: Spring

[0091] 63: retaining ring

[0092] 64: Steel Ball

[0093] 70: Control circuit board

[0094] 75: Switch panel

[0095] 90: Battery

[0096] 91: Latch button

[0097] 130: Hammer

[0098] 131: Ontology Department

[0099] 132: Front facing side

[0100] 133: Boundary position

[0101] 134a~134c:conical surface

[0102] 136~138: Hammer Claw

[0103] 141a, 141b, 142a, 142b, 143a, 143b: groove

[0104] 150: Anvil

[0105] 230: Hammer

[0106] 231: Ontology Department

[0107] 232: Front facing surface

[0108] 233: Boundary position

[0109] 234a, 234b: Conical surface

[0110] 236, 237: Hammer Claw

[0111] 236a, 236b, 237a, 237b: striking surface

[0112] 241a, 241b, 242b: Connecting parts

[0113] 241c, 242c: Chamfer

[0114] 250: Anvil

[0115] 256, 257: Wings

[0116] 256a, 256b, 257a, 257b: struck side

[0117] 330: Hammer

[0118] 331: Ontology Department

[0119] 332: Front facing surface

[0120] 332a: radially inner position

[0121] 332b: radially outer position

[0122] 336: Hammer Claw

[0123] 345: Hitting Point

[0124] 346: Root position (of the striking point)

[0125] 350: Anvil

[0126] A1: Rotation axis

[0127] A2: Center of rotation (of the hammer)

[0128] A3: Center of rotation (of the anvil) DETAILED DESCRIPTION

[0129] Example 1

[0130] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In the following description, the directions of front, back, left, right, and top and bottom are described in the form of directions shown in the drawings.

[0131] Figure 1This is a side view showing the appearance of an impact tool 1 according to an embodiment of the present invention. The impact tool 1 uses a rechargeable battery pack 90 as its power source and a motor as its drive source. It applies rotational force and striking force to the output shaft (anvil 50), intermittently transmitting the rotational striking force to a tool tip (not shown), such as a bit, held in an assembly hole 53 by an assembly mechanism 60, to perform operations such as screw tightening and bolt tightening. The housing 2 of the impact tool 1 is generally T-shaped and includes a generally cylindrical main body 2a that houses the motor or power transmission mechanism, and a handle 2b that extends from approximately the center of the main body 2a in a direction generally perpendicular to the rotation axis A1 and is intended to be gripped by the operator with one hand. A battery mounting portion 2c is formed at the lower end (anti-main body end) of the handle 2b, located opposite the main body 2a. A trigger lever 7a is provided at an upper portion of the handle portion 2b so as to protrude forward. A forward / reverse switching lever 8 for switching the rotation direction of the motor 3 between forward and reverse directions is provided behind the trigger lever 7a.

[0132] The motor 3 is housed on the rear side of the cylindrical main body 2a. The motor 3 is a brushless (brush for rectifier) ​​direct current (DC) motor, which is a four-pole six-slot brushless DC motor. The motor 3 includes a rotor 3a having a permanent magnet, and a stator 3b having a multi-phase armature winding (stator winding) such as a three-phase winding. The rotor 3a forms a magnetic circuit formed by permanent magnets. The stator 3b is made of a laminated structure of thin annular iron plates, and six teeth (not shown) are formed on the inner circumference. An enameled wire is wound around each tooth to form a coil. In this embodiment, the coil is set to be star-connected or delta-connected with three phases, namely, U, V, and W phases. The motor 3 is operated as follows: the output of the position detection element 13 including multiple Hall integrated circuits (ICs) that detect the magnetic force of the permanent magnet of the rotor 3a and detect the rotor position is used, and the DC voltage supplied by a battery or the like is switched by multiple semiconductor switching elements 14. In this embodiment, the motor is a brushless motor, but it may also be a motor with a brush.

[0133] The rotating shaft 4 of the motor 3 is arranged concentrically with the rotating axis A1 of the cylindrical main body 2a, and is axially supported by the housing 2 on the front and rear sides by two bearings 16a and 16b. A roughly annular inverter circuit substrate 12 for carrying three position detection elements 13 or six semiconductor switching elements 14 is arranged on the rear side of the stator 3b. The inverter circuit substrate 12 is a roughly annular double-sided substrate with a diameter roughly the same as the outer diameter of the motor 3. Six semiconductor switching elements 14 are provided to form an inverter circuit to switch the power supply to the stator winding of each phase. As the semiconductor switching element 14, a field effect transistor (FET) or an insulated gate bipolar transistor (IGBT) can be used. The inverter circuit is controlled by a microcomputer, and the power supply timing of the armature winding of each phase is set based on the position detection signal of the rotor 3a of the position detection element 13, so that high-level rotation control is easy to perform.

[0134] A cooling fan 15 is mounted coaxially with the rotating shaft 4 between the rotor 3a and the bearing 16b. The cooling fan 15 is integrally molded, for example, from a plastic mold. It draws air from air intakes (not shown) formed near the left and right sides of the inverter circuit board 12 in the main body 2a. The air is then discharged rearward in the direction of the rotation axis A1, flowing through and around the motor 3. The cooling air from the inverter circuit board 12 cools the motor 3 located behind the inverter circuit board 12 and is then discharged to the outside through air discharge slits (not shown) formed on the sides of the cooling fan 15.

[0135] A cup-shaped hammer case 5 is provided on the front side of the housing 2. The hammer case 5 houses the speed reduction mechanism 20 and the impact mechanism (striking mechanism) 25 and is located on the front side of the main body 2a of the housing 2. The hammer case 5 is made of a single piece of metal. A through-hole 5a for the anvil 50 is formed in the front portion of the hammer case 5, which abuts the cup-shaped bottom. An attachment mechanism 60 for attaching and detaching a tip tool (not shown) is provided on the outside of the hammer case 5, at the front end of the anvil 50.

[0136] The assembly mechanism 60 is composed of the following: an assembly hole 53 extending axially and rearwardly from the front end of the anvil 50 and having a hexagonal cross-sectional shape; two holes formed at two locations in the circumference for accommodating a steel ball 64 and passing through in the radial direction; and a sleeve 61 provided on the outer circumference. A spring 62 is mounted on the inner side of the sleeve 61 to push the sleeve 61 toward the rear. An illumination device 9 is provided on the lower side of the assembly mechanism 60 for illuminating the vicinity of the front end of the front end tool (not shown). As the illumination device 9, one or more light emitting diodes (LEDs) can be used, and an illumination window for transmitting light is provided on the front side of the illumination device 9.

[0137] A trigger lever 7a is provided in the upper portion of the handle portion 2b, which extends substantially perpendicularly from the main body 2a of the housing 2, projecting forward. A trigger switch 7 is provided behind the trigger lever 7a. The user grips the handle portion 2b with one hand and moves the trigger lever 7a rearward with their index finger or other finger to adjust the amount of trigger depression (operation distance), thereby adjusting the rotational speed of the motor 3. The direction of rotation of the motor 3 can be switched by operating a forward / reverse switching lever 8.

[0138] A battery mounting portion 2c that expands in diameter in a direction substantially perpendicular to the axial direction of the handle portion 2b is provided at the lower portion of the handle portion 2b. A battery 90 serving as a driving power source for the motor 3 is detachably mounted on the battery mounting portion 2c. When removing the battery 90, the battery 90 is moved relative to the front side of the main body of the impact tool 1 while pressing the latch portion 91. A control circuit board 70 for controlling the inverter circuit board 12 of the motor 3 is provided above the battery 90. The control circuit board 70 is arranged horizontally in a manner extending in the front, back, left, and right directions, and is equipped with a microcomputer (not shown) that controls the rotation of the motor 3. The control circuit board 70 is connected to the inverter circuit board 12 via a signal line. A switch panel 75 for configuring a remaining amount check switch for the battery 90, an LED display device for indicating the remaining amount, and a lighting switch for the lighting device 9 is provided near the control circuit board 70 and on the upper surface of the battery mounting portion 2c.

[0139] The main body 2a of the housing 2 is made of a synthetic resin material together with the handle 2b and the battery mounting portion 2c. It is formed so that it can be divided into two parts, left and right, by a vertical plane passing through the rotating shaft 4 of the motor 3. When assembling, the following method is used: prepare the left and right members of the housing 2, assemble the speed reduction mechanism 20 and the impact mechanism 25 in advance, and then assemble them into the housing 2. Figure 1 As shown in the cross-sectional view of FIG, the hammer case 5 and the motor 3 of one of the housings 2 (for example, the housing on the left) are assembled, and then the other housing 2 (for example, the housing on the right) is overlapped and fastened with a plurality of screws.

[0140] The impact mechanism 25 is located on the output side of the planetary gear reduction mechanism 20. It includes a rotating shaft 26 and a hammer 30, rotatably held by a bearing 18b at the rear end and a bearing 18a at the front end. The reduction mechanism 20 is composed of a sun gear 21 fixed to the front end of the rotating shaft 4 of the motor 3; a ring gear 23 spaced and surrounding the outer periphery of the sun gear 21; and a plurality of planetary gears 22 positioned in the space between the sun gear 21 and the ring gear 23, meshing with these two gears. The ring gear 23, also known as an external gear, is a gear formed on the inner circumference of an annular member. The outer circumference of the ring gear 23 is held by the housing 2, and the ring gear 23 itself does not rotate.

[0141] The sun gear 21 is a spur gear that serves as the input portion of the reduction gear mechanism 20. Multiple (here, three) planetary gears 22 are arranged between the outer gear surface of the sun gear 21 and the inner gear surface of the ring gear 23. The three planetary gears 22 are axially supported by a planetary gear carrier formed at the rear end of the rotating shaft 26. The planetary gears 22 rotate around the shaft (not shown) supported by the planetary gear carrier while revolving around the sun gear 21. When the rotating shaft 4 of the motor 3 rotates, the sun gear 21 also rotates synchronously with it. The rotational force of the sun gear 21 is reduced at a predetermined ratio, causing the rotating shaft 26 to rotate.

[0142] The inner cover 19 is a component manufactured by integral molding of synthetic resin, and is held by the main body 2a of the housing 2 in a manner that clamps it from the left and right directions. At this time, the inner cover 19 is held in a manner that does not rotate relative to the housing 2. One of the multiple screw columns is located at the upper part of the inner cover 19, so that the inner cover 19 is stably clamped by the housing 2. The main function of the inner cover 19 is to hold the two bearings 18b and the bearing 16a, and to center the rotation center of the rotating shaft 4 of the motor 3 and the rotating shaft 26 on the same axis. The bearing 16a held by the inner cover 19 is used to axially support the rotating shaft 4 of the motor 3, and a ball bearing can be used, for example. The bearing 18b held by the inner cover 19 is used to axially support the rear end of the rotating shaft 26, and a ball bearing can be used, for example.

[0143] The reduction mechanism 20 and the impact mechanism 25 form the power transmission mechanism for driving the tool tip via the motor 3. When the trigger lever 7a is pulled to activate the motor 3, the motor 3 begins rotating in the direction set by the forward / reverse switching lever 8. This rotational force is reduced by the reduction mechanism 20 and transmitted to the rotating shaft 26, which then rotates at a predetermined speed. The rotating shaft 26 and hammer 30 are connected by a cam mechanism comprising a V-shaped rotating shaft cam groove 26a formed on the outer circumference of the rotating shaft 26, a hammer cam groove 39 formed on the inner circumference of the hammer 30, and two steel balls 27 that engage with the rotating shaft cam groove 26a and hammer cam groove 39. The hammer 30 is constantly urged forward by the hammer spring 28. At three locations on the facing rotational planes of the hammer 30 and the anvil 50, hammer claws (striking claws) 36 to 38 (37 is not visible in the figure) that protrude convexly in the direction of the rotation axis A1 and wings (striking claws) 56 to 58 (only 56 is visible in the figure) that are struck by the striking claws are formed in a rotationally symmetrical manner.

[0144] When the rotating shaft 26 is driven to rotate, its rotation is transmitted to the hammer 30 via the cam mechanism. While the hammer 30 is not halfway rotated, the hammer 30's striking claw engages with the struck claw of the anvil 50, causing the anvil 50 to rotate. The rotating shaft 26 and hammer 30 rotate relative to each other due to the reaction force of the engagement between the hammer 30 and the anvil 50 during rotation. The hammer 30 then begins to retract toward the motor 3 while compressing the hammer spring 28 along the rotating shaft cam groove 26a of the cam mechanism. The retracting motion of the hammer 30 causes the hammer 30's striking claw to overtake the struck claw of the anvil 50, releasing the engagement between the two. The hammer 30 then rapidly accelerates in the rotational direction and forward due to the elastic energy stored in the hammer spring 28 and the action of the cam mechanism, in addition to the rotating force of the rotating shaft 26. The hammer 30 then moves forward due to the biasing force of the hammer spring 28, causing the hammer 30's striking claw (36, etc.) to reengage with the struck claw (56, etc.) of the anvil 50, and begins to rotate together. When the hammer 30 rotates one revolution relative to the anvil 50, a strong rotational striking force is applied to the anvil 50, with the number of strikes (simultaneous strikes) being three (low-speed strikes) or 1.5 (high-speed strikes). Therefore, the rotational striking force is transmitted to a tip tool (not shown) mounted in a mounting hole 53 integrally formed with the anvil 50. Thereafter, the same operation is repeated, and the rotational striking force is intermittently and repeatedly transmitted to the tip tool, for example, when a wood screw is driven into a fastened member (not shown) such as wood.

[0145] Figure 2 The hammer 30 is a perspective view of the hammer 30 and the anvil 50 of this embodiment. The hammer 30 is arranged between the speed reduction mechanism 20 and the anvil 50 along the direction of the rotation axis A1. The hammer 30 is arranged relative to the rotation shaft 26 (refer to Figure 1) can rotate relative to each other and can move relative to each other in the direction along the rotation axis A1. Hammer cam grooves 39a and 39b are formed on the radial inner side of the hammer 30. Steel balls 27 (see Figure 1 The hammer 30 is separated from the steel ball 27 (see Figure 1 ) and by the rotating shaft 26 (refer to Figure 1 ) is maintained, so it can move in the direction of the rotation axis A1 within the range that the steel ball 27 can rotate, and relative to the rotating shaft 26, it can rotate relatively within a specified range along the circumferential direction with the rotation axis A1 as the center axis within the range that the steel ball 27 can rotate.

[0146] As the load on the anvil 50 in the rotational direction increases, the hammer claws 36-38 of the hammer 30 repeatedly engage and disengage with the wings 56-58 of the anvil 50, thereby generating a rotational striking force on the anvil 50, which serves as the output shaft. Here, the weight of the hammer 30 is set to be greater than the weight of the anvil 50, and the hammer 30 converts the rotational force of the rotating shaft 26 into a rotational force or a rotational striking force on the anvil 50.

[0147] The hammer 30 includes a body 31 formed in a generally cylindrical shape, and hammer claws 36 through 38 extending forward from the body 31. In this specification, the portion of the hammer 30 other than the claws 36 through 38 is referred to as the "body 31." A front-facing surface 32 (orthogonal surface) perpendicular to the rotation axis A1 is formed on the anvil 50 side of the body 31. The front-facing surface 32 is adjacent to and faces the anvil 50. When the hammer 30 is in its normal position (the forward position within its range of forward and backward movement along the rotation axis A1), it faces or contacts the wings 56 through 58 of the anvil 50 with a slight gap. The front-facing surface 32 is a generally annular surface perpendicular to the rotation axis A1. Tapered surfaces 34a through 34c are formed on the outer circumference of the front-facing surface 32. The tapered surfaces 34a to 34c are inclined surfaces that are inclined toward the rear side (anti-anvil side) in the direction of the rotation axis A1 as they move from the radially inner peripheral side toward the radially outer peripheral side. Figure 2 In the figure, the connection between the outer periphery of the front facing surface 32 and the inner peripheries of the tapered surfaces 34a through 34c is illustrated with double lines. This is because the cross-sectional shape of the connection, including the rotation axis A1, is chamfered, resulting in a surface with a small radius of curvature in the region between the double lines. The connection between the outer periphery of the front facing surface 32 and the inner peripheries of the tapered surfaces 34a through 34c is angular, the connection between the double lines is flat, or the connection between the double lines is formed as a groove recessed inward in the plane direction.

[0148] The hammer claws 36-38 are formed to protrude forward from the main body 31 and are integrally formed with the main body 31. The circumferential centers of the hammer claws 36-38 are spaced 120 degrees apart (equally spaced) along the circumference, and their cross-sectional shape, taken along a direction intersecting the rotation axis A1, is generally fan-shaped. The width of the hammer claws 36-38 radially outward and along the circumference of the hammer 30 is set to approximately 10 mm. This ensures sufficient strength for the hammer claws 36-38, while allowing the wings 56-58 of the anvil 50 to fit comfortably between adjacent hammer claws 36-38 along the circumference of the hammer 30. The central angle of the fan-shaped portion is located closer to the rotation axis A1, while the arc portion is located approximately at the same position as, or slightly inward of, the outer edge of the main body 31 of the hammer 30. The arcuate portions of the cross-sectional shapes of the hammer claws 36-38 may have a constant diameter or a slightly decreasing diameter as they move forward from the rear in the direction of the rotation axis A1. In this embodiment, the outer peripheral surfaces of the hammer claws 36-38 are configured so that the diameters decrease slightly as they move forward, as if the outer diameters on the distal end of the claws slightly taper. Furthermore, the distal end surfaces of the hammer claws 36-38 are chamfered perpendicular to the rotation axis A1. In other words, the distal end surfaces of the hammer claws 36-38 are parallel to the front-facing surface 32.

[0149] When viewed along the circumferential direction, the tapered surfaces 34a to 34c are arranged so as to be discontinuous along the circumferential direction due to the three hammer claws 36 to 38. The innermost circumferential position of each tapered surface 34a to 34c is arranged between the radially innermost position and the radially outermost position of the substantially fan-shaped hammer claws 36 to 38. By setting the boundary position 33 between the tapered surfaces 34a to 34c and the front facing surface 32, the protrusion amount (described below) of the hammer claws 36 to 38 in the innermost circumferential position relative to the main body 31 can be adjusted to the front of the rotation axis A1. Figure 3 The size represented by L1 in the figure) and the protrusion amount in the outermost position (described below) Figure 3 The size represented by L2 in the figure is formed in different ways.

[0150] The anvil 50 is manufactured by integrally forming metal, and three wings 56 to 58 are formed on the rear side of the main shaft 51, which protrude radially outward from the annular flange 54. The main shaft 51 is supported by a bearing 18a (see FIG. Figure 1) is supported by the main shaft 51, which becomes the rotating surface of the needle roller of the bearing 18a. A thin-diameter portion 52 is formed on the front side of the main shaft portion 51 to be slightly thinned for installing the assembly mechanism 60 of the front end tool not shown in the figure. From the front end of the thin-diameter portion 52 toward the rear side in the direction of the rotation axis A1, an assembly hole 53 with a hexagonal cross-sectional shape for assembling the front end tool is formed. Two through holes 52a are formed in the radial direction near the rear end of the thin-diameter portion 52, and a steel ball 64 (see Figure 1 When viewed in the axial direction, the main shaft portion 51 having a cylindrical outer peripheral surface is formed between the through hole 52a and the wing portions 56 to 58.

[0151] The three wings 56 to 58 that become the struck parts are evenly arranged in a manner that their circumferential center positions are spaced 120 degrees apart when viewed along the rotation direction, and are arranged in a manner extending radially outward. The side surfaces of the wings 56 to 58 in the rotation direction form the struck surfaces 56a, 57a, and 58a that are struck by the striking claws of the hammer 30 when rotating in the tightening direction, and the struck surfaces 56b, 57b, and 58b that are formed on the opposite side and are struck when rotating in the loosening direction. A cylindrical shaft portion 55 is formed on the rear side of the wings 56 to 58, and the outer peripheral surface of the shaft portion 55 is formed by a fitting hole (refer to Figure 1 ) is axially supported in a slidable manner. The width of the wings 56-58 along the circumferential direction and radially outward of the anvil 50 is set to approximately 5 mm. In other words, it is set to a width slightly shorter than the width of the hammer claws 36-38. This ensures sufficient strength for the wings 56-58 and allows for a relatively long distance between adjacent wings 56-58 along the circumference of the anvil 50, allowing the hammer claws 36-38 of the hammer 30 to fit comfortably.

[0152] Figure 3 (A) is a front view of hammer 30, Figure 3 The longitudinal section of (B) is Figure 3 (A) is a cross-sectional view of the AA section. Figure 3 In (B), if it is a vertical cross-sectional view, only one of the three hammer claws 36 to 38 is shown, so it is a cross-sectional view of the AA portion (in addition, Figure 1 、 Figure 6 In the figure, the cross-sectional position of the hammer 30 and the anvil 50 is set as the cross-sectional position of the AA portion. Figure 3In (A), the front wall of the main body 31 of the hammer 30 is formed by a front facing surface 32 located on the inner circumference and tapered surfaces 34a, 34b, and 34c located on the outer circumference thereof. Hatching is added here to clarify the scope of these areas. When viewed from the front, the hammer claws 36, 37, and 38 are formed in a fan-shaped shape. The base of the innermost portion of the fan-shaped portion (the portion connected to the main body 31) is within the range of the front facing surface 32, and the outer circumference is the area where the tapered surfaces 34a, 34b, and 34c are connected from near the middle of the straight edge of the fan-shaped portion. In other words, the boundary 33 between the tapered surfaces 34a, 34b, and 34c and the front facing surface 32 can be configured so that it is located between the innermost and outermost positions of the fan-shaped portion of the hammer claws 36, 37, and 38.

[0153] exist Figure 3 In (B), the hammer 30 is formed into a double-cylindrical shape consisting of an outer cylindrical portion 31a and an inner cylindrical portion 31c. The outer and inner cylindrical portions 31a and 31c are connected on the front side thereof by a front surface connecting portion 31b. A front facing surface 32 and tapered surfaces 34a through 34c are formed on the front side of the front surface connecting portion 31b. A spring support portion 31d is formed on the rear side of the front surface connecting portion 31b to support the front end of the coiled spring that holds the hammer spring 28. The annular center position (the front end position) of the spring support portion 31d is positioned such that the distance from the rotation axis A1 and the boundary position 33 between the tapered surfaces 34a through 34c and the orthogonal surface (the front facing surface 32) are approximately equal. By forming the hammer 30 in this manner, the lengths of the hammer claws 36, 37, and 38 in the direction of the rotation axis A1 are L1 on the inner circumference and L2 on the outer circumference, with L2 > L1. The receding angle α of the tapered surfaces 34 a and 34 b is set to 6° here, but may be appropriately set within a range of approximately 2° to 20°.

[0154] Figure 4 (A) is a front view of the anvil 50. The shape of the anvil 50 is the same as that of the anvil 50 used in the existing impact tool. When viewed along the rotation axis A1, the anvil 50 is installed at a position where the distance from the hammer 30 is slightly smaller than that of the existing impact tool. The anvil 50 has three wings 56 to 58. A struck surface 56a, a struck surface 57a, and a struck surface 58a are formed on one side of the rotation direction of the wings 56 to 58, and a struck surface 56b, a struck surface 57b, and a struck surface 58b are formed on the other side. In accordance with the relationship of the strong striking force applied to the anvil 50 by the hammer 30, a circular flange portion 54 is formed on the outer peripheral side of the main shaft portion 51, and the front view shape of the flange portion 54 and the wings 56 to 58 is set to be close to a triangular shape, thereby improving the strength.

[0155] Figure 4 (B) is Figure 4 The BB section of (A) is a cross-sectional view. The assembly hole 53 of the anvil 50 is constructed in a manner that extends not only to the small diameter portion 52 but also to the rear side of the rotation axis A1 in the inner side of the main shaft portion 51. With the above structure, a front end tool such as a screwdriver bit (not shown) can be assembled along the axial direction. The through hole 52a is a hole that passes through the assembly hole 53 on the inner side of the small diameter portion 52 to the outer side. The size of the through hole 52a is formed to be slightly larger than the steel ball 64 (refer to Figure 1 ), but only the innermost diameter is formed to be slightly smaller than the steel ball 64, so that the steel ball 64 inserted from the outer peripheral side of the through hole 52a cannot pass through the inside of the radially inner assembly hole 53, and is formed in a manner that a certain amount of protrusion is left on the side of the assembly hole 53. In order to fix the retaining spring 62 (refer to Figure 1 ) retaining ring 63 (refer to Figure 1 ), and a circumferential groove 52b is formed near the front end of the small diameter portion 52 in the direction of the rotation axis A1. Wings 56, 57, and 58 (57 is not visible in the figure) extending radially outward from the flange portion 54 are formed on the rear side of the main shaft portion 51, and a cylindrical shaft portion 55 is formed further rearward than the wings 56, 57, and 58. The shaft portion 55 is formed solid so as to be inserted into the fitting hole (see FIG. 2 ) of the rotating shaft 26. Figure 1 ) and is supported by the shaft in a sliding state.

[0156] Figure 5 This is a front view showing the hammer 30 and anvil 50 in a normal striking state. The respective rotation centers of the hammer 30 and anvil 50 are coaxial with the rotation axis A1, which serves as the rotation center of the motor 3, during normal operation. In this coaxial state, the striking surface 36a of the hammer claw 36 and the struck surface 56a of the anvil 50 are in good surface contact over substantially their entire surfaces, as indicated by the portion indicated by the thick black line. Similarly, the striking surface 37a of the hammer claw 37 is in good surface contact over substantially its entire surface with the struck surface 57a of the anvil 50, and the striking surface 38a of the hammer claw 38 is in good surface contact over substantially its entire surface with the struck surface 58a of the anvil 50. During normal rotation, these three areas of surface contact occur simultaneously as the hammer 30 rotates, thereby transmitting a striking force rotationally symmetrical with respect to the rotation axis A1 from the hammer 30 to the anvil 50.

[0157] Figure 6This longitudinal cross-section, taken along rotation axis A1, shows the shapes of the hammer 30 and anvil 50 according to the present invention. The upper half shows the shapes of the hammer 30 and anvil 50 according to the present invention, while the lower half shows the shapes of the conventional hammer 330 and anvil 350. In the figure below rotation axis A1, the conventional hammer 330 has a front outer wall surface (front facing surface 332) of the main body 331 that is perpendicular to rotation axis A1. Front facing surface 332 is flat from radially inward position 332a to radially outward position 332b, with the same position along rotation axis A1. In contrast, the hammer 30 of this embodiment has a flat surface 32b (orthogonal surface) perpendicular to rotation axis A1 from radially inward position 32a to boundary position 33. From boundary position 33 to the outer periphery, tapered surfaces 34a through 34c are formed (portion 34c is visible in the figure). Boundary position 33 is located further inward than the outermost diameter portion of anvil 50, so the outermost diameter portion of anvil 50 faces tapered surfaces 34a through 34c. As a result, the distance between striking point 45 of hammer claw 36 and body 31 (root position 46) of hammer 30 in this embodiment is L4, as shown in the figure. On the other hand, in conventional hammer 330, the distance between striking point 345 of hammer claw 336 and body 331 (root position 346) of hammer 330 is L3, as shown in the figure, achieving a relationship of L4 > L3. As described above, by setting L4 > L3, the hammer claws 36 to 38 are more likely to deform as they approach the outer diameter ends. Even when the hammer claws 36 to 38 partially contact the wings 56 to 58 of the anvil 50 at their outer diameter ends, the contact portion expands toward the inner diameter before a large stress is generated near the base of the contact portion between the hammer claws 36 to 38. This reduces the positional difference in the load borne near the base. Consequently, stress concentration at a specific location (near the outer diameter end of the base of the claw) that occurs when the hammer claws 36 to 38 partially contact each other can be reduced.

[0158] In this embodiment, the front side of the main body 31 of the hammer 30 includes a flat surface 32b (orthogonal surface) and tapered surfaces 34a to 34c. Therefore, the length D1 from the flat surface 32b (orthogonal surface) to the rear end of the hammer 30 in the axial direction can be greater than the length D2 from the tapered surfaces 34a to 34c to the rear end of the hammer 30 in the axial direction. In addition, the tapered surfaces 34a to 34c are formed on the outer peripheral side of the front side wall of the main body 31 of the hammer 30. However, the tapered surfaces 34a to 34c can also be formed in a curved surface, an arc shape, or a polygonal shape instead of the above. Figure 6 The cross-sectional shape is straight.

[0159] Figure 7 (A) is a front view showing the striking state of the hammer 30 and the anvil 50 when the hammer 30 and the anvil 50 are off-center. Figure 5During normal rotation (when the centers of rotation of the hammer 30 and the anvil 50 coincide), the striking surface 36a strikes the struck surface 56a, the striking surface 37a strikes the struck surface 57a (not shown), and the striking surface 38a strikes the struck surface 58a simultaneously. However, if the center of rotation of the hammer 30 deviates from the center of rotation of the anvil 50, as in A2, A3, the initial point of contact between the hammer 30 and the anvil 50 becomes point contact (or line contact) rather than surface contact, and the timing of the strikes is not simultaneous. Figure 7 (A) is a diagram showing the deviation between the rotation centers A2 and A3, which greatly illustrates the above-described state. Note that a portion of the wing portion of the anvil 50 is omitted.

[0160] exist Figure 7 In (A), the deviation of the rotation center A2 of the hammer 30 causes the initial striking point to be a specific portion (the striking point shown in the figure) of the hammer claw 36 and the wing 56. There are cases where the hammer 30 deviates from the position of the rotation center A2 relative to the rotation axis A1, and there are cases where the rotation center A3 of the anvil 50 deviates in the opposite direction relative to the rotation axis A1. As described above, if the rotation centers A2 and A3 deviate in opposite directions, it becomes Figure 7 (A) (For convenience of explanation, the deviation is exaggerated in the figure). At this time, the hammer claw 36 and the wing 56, and the hammer claw 38 and the wing 58 are struck, but the hammer claw 37 and the wing 57 (not shown) have not yet been struck. If the rotation center A2 of the hammer 30 deviates, the initial striking point is located further inboard than the outermost position 36c of the hammer claw 36. In contrast, the striking point of the wing 58 is located near the outermost position 38c of the hammer claw 38. Figure 7 (B) shows a cross section of the CC portion in the above state.

[0161] Figure 7 (B) is a cross-sectional view of the CC portion and a view viewed from the CC portion in the direction of the rotation axis A1. Here, the two-dot chain line indicates the position of the wing portion 56 of the anvil 50. In the figure, the hammer claw 36 and the wing portion 56 of the anvil 50 abut on the front side away from the chamfered groove 41a formed at the root of the hammer claw 36 in the direction of the rotation axis A1. During the striking action during use, the root of the hammer claw 36 and the wing portion 56 of the anvil 50 are closer than the front side due to the rotation speed of the rotating shaft 26 or the load acting on the front end tool. Figure 1 The state will become a state away from the rotation axis A1 direction. That is, when viewed in the direction of the rotation axis A1, Figure 7 The impact point (line) shown in (A) will be generated on the front side.

[0162] Figure 8 yes Figure 7After the hammer spring 28 is compressed, the hammer 30 advances along the rotation axis A1 while rotating in the direction of the black arrow. The claw of the hammer 30 (e.g., the hammer claw 36) strikes the wing of the anvil 50 (e.g., the wing 56). Figure 8 The state immediately after the strike is shown. The striking surface 36a of the hammer claw 36 is deformed from the position of the single-dot chain line (parallel to the rotation axis A1) by colliding with the wing portion 56 of the anvil 50 due to the impact (for ease of understanding, the striking surface 36a' shown in the solid line) starting from the position of the single-dot chain line. Figure 8 (The deformation is shown as being extremely large in the figure, but the actual deformation is very small). At this time, in the impact tool 1 of this embodiment, as in the hammer claw 36, the distance from the tapered surface 34c to the striking point as viewed along the rotation axis A1 is L4, and the striking point is displaced by d from the position of the striking surface 36a when not striking. The striking surface 36a' of the hammer claw 36 is deformed by an angle α when striking. After the striking point is displaced by d, the striking surface 36a of the hammer claw 36 and the struck surface 57a of the anvil 50 are aligned as shown in FIG. Figure 5 That way, the entire surface is in contact. Figure 6 In the conventional hammer 330 shown in the lower half of FIG, since no tapered surface is formed on the hammer, the position of the front facing surface 332 of the main body of the hammer becomes Figure 8 The position indicated by the dashed line is shown. Thus, the distance from the dashed line position to the striking point, as viewed along the rotation axis A1, is L3. In this case, upon striking, the striking surface of the hammer claw 336 deforms by an angle β, satisfying the relationship α < β. In other words, the stress generated in each of the hammer claws 36 to 38 is reduced when the configuration of the present invention is applied.

[0163] As described above, by using the hammer 30 of this embodiment, even when the hammer claw and the anvil blade partially contact at their outer diameter ends, the contact portion expands toward the inner diameter before a significant stress is generated at the base of the hammer claw. This reduces the positional differences in the load borne by the base of the hammer claw. As a result, stress concentration near the outer diameter end of the base of the claw, which occurs when the hammer claw partially contacts the anvil blade, can be reduced, thereby achieving a highly reliable and durable striking mechanism.

[0164] Example 2

[0165] Figure 9It is a three-dimensional view of the hammer 130 and the anvil 150 of the second embodiment of the present invention. The hammer 130 is composed of a main body 131 and three hammer claws 136 to 138. The radial inner position of the main body 131 to the boundary position 133 is a flat surface (front facing surface 132) perpendicular to the rotation axis A1, and the boundary position 133 to the outer peripheral side are tapered surfaces 134a to 134c. The hammer 130 is formed with six grooves 141a, 141b (not visible in the figure), 142a, 142b, 143a, and 143b. These grooves are formed with a curvature radius r, and by combining with the tapered surfaces 134a, 134b, and 134c of this embodiment, the curvature radius r can be made smaller than the grooves formed on the existing hammer 330. Figure 9 In the figure, the curvature radius r is exaggerated for the sake of understanding, but is actually a very small radius of about 1 mm. By making the curvature radius r of these grooves 141a, 141b (not visible in the figure), 142a, 142b, 143a, and 143b smaller than the curvature radius r1 (not shown) of the hammer in which the existing grooves are formed, the distance between the hammer 130 and the anvil 150 in the direction of the rotation axis A1 (with respect to the distance from the hammer 130 to the anvil 150) can be reduced. Figure 6 The gap (equivalent to the gap L3) is smaller than in the conventional case. When the curvature radius r1 is large, as in the conventional case, the contact portion between the hammer 130 and the anvil 150 and the groove partially overlap, thereby lengthening the length of the hammer claw of the hammer 330 in the direction of the rotation axis A1 and increasing the distance between the hammer 330 and the anvil 350. In the impact tool 1 of this embodiment, the distance between the hammer 130 and the anvil 150 is smaller than in the conventional case, thereby enabling the impact tool 1 to be smaller in size than in the conventional case.

[0166] Example 3

[0167] Figure 10 2 is a perspective view of a hammer 230 and anvil 250 according to a third embodiment of the present invention. In the first and second embodiments, the number of hammer claws and wings is three, but the present invention is as follows. Figure 10An impact tool having two hammer claws on the hammer 230 and two wings on the anvil 250 can also be similarly implemented. The hammer 230 comprises a main body 231 and two hammer claws 236 and 237. The main body 231 has a flat surface (front-facing surface 232) perpendicular to the rotation axis A1 from its radially inner side to its boundary 233. From the boundary 233 to the outer circumference, the hammer claws 236 and 237 form tapered surfaces 234a and 234b. The two hammer claws 236 and 237 are arranged on the hammer 230 circumferentially 180° apart. The cross-section of the hammer claw 236 perpendicular to the rotation axis A1 is generally fan-shaped, with the circumferential side surfaces forming a striking surface 236a for forward rotation and a striking surface 236b for reverse rotation. Near the connection between the body 231 and the striking surface 236a of the hammer 230, gently curved connecting portions 241a and 241b (241b is not visible in the figure) are formed. Near the connection between the body 231 and the striking surface 237b, gently curved connecting portion 242b is formed. Furthermore, the corners between the outer circumference and the front surface of the hammer claw 236 and the outer circumference and the front surface of the hammer claw 237 are chamfered 241c and 242c, respectively.

[0168] The two wings 256 and 257 are arranged on the anvil 250 circumferentially 180° apart. The shapes of the main shaft portion 51, the thin-diameter portion 52, the mounting hole 53, and the shaft portion 55 of the anvil 250 are identical to those of the anvil 50 of the first embodiment. The radially outer halves of the wings 256 and 257 are identical to the outer shapes of the wings 56 to 58 of the anvil 50 shown in the first embodiment. The side surface of the wing 256 forms a struck surface 256a for forward rotation and a struck surface 256b for reverse rotation, while the side surface of the wing 257 forms a struck surface 257a for forward rotation and a struck surface 257b for reverse rotation. As described above, the present invention can also be applied to impact tools having two hammer claws and two wings.

[0169] While the present invention has been described above based on embodiments, the present invention is not limited to the aforementioned embodiments and various modifications are possible without departing from the spirit of the present invention. For example, the shape of the hammer claw or the anvil wing is not limited to the aforementioned examples and may be realized with other shapes. In such cases, the outer peripheral portion of the front side of the hammer body may be tapered, with the length of the hammer claw in the direction of the rotation axis varying between the inner and outer peripheral sides. Furthermore, the tapered surface may not only be a flat surface but may also be a convex arc surface on the outer side or a polyhedron.

Claims

1. An impact tool, characterized in that: include: motor; a rotating shaft driven by the motor in a rotation direction about a rotation axis; The hammer is capable of relative movement along the rotation axis and the rotation direction within a predetermined range relative to the rotation shaft, and is pushed forward by a cam mechanism and a spring; and The anvil is rotatably provided in front of the hammer and is struck by the hammer when the hammer moves forward and rotates. The hammer comprises: a main body; a front surface wall portion provided on the front surface of the main body; and a claw portion, extending forward from the main body portion, forming a tapered surface on the front surface wall portion of the main body portion, the tapered surface gradually receding as it moves away from the rotation axis, the front inner diameter side end portion of the main body portion being located further forward than the front outer diameter side end portion, and being configured so as to protrude from the tapered surface toward the anvil side through a portion or all of the claw portion, the relationship between the length L1 of the inner diameter side front end portion of the claw portion from the main body portion and the length L2 of the outer diameter side front end portion of the claw portion from the main body portion being L1<L2.

2. The impact tool according to claim 1, wherein: Grooves having a predetermined curvature radius are formed at connecting corners between the main body and the claw on both sides in the circumferential direction.

3. The impact tool according to claim 1, wherein: An orthogonal surface orthogonal to the rotation axis is formed on the front wall of the body, and an axial length D1 from the orthogonal surface to the rear end of the hammer is greater than an axial length D2 from the tapered surface to the rear end of the hammer.

4. The impact tool according to claim 3, wherein: By providing the tapered surface on the outer peripheral side of the front wall portion, D1>D2 is achieved.

5. The impact tool according to claim 4, wherein: A spring support portion is formed on the anti-anvil side of the body portion of the hammer, and the spring support portion is used to support the spring. The tapered surface is provided radially outward of a radial center position of the spring support portion.

6. The impact tool according to claim 1, wherein: The cam mechanism includes: a rotating shaft cam groove provided on the rotating shaft; a hammer cam groove formed on the inner circumference of the hammer; a cam roller arranged between the rotating shaft cam groove and the hammer cam groove; and the coil-shaped spring arranged around the rotating shaft to push the hammer toward the anvil side in the direction of the rotation axis.

7. The impact tool according to claim 1, wherein: The impact tool includes a housing that accommodates the motor and a battery that is detachably attached to the housing. The motor is driven by the battery as a driving power source.

8. The impact tool according to claim 1, wherein: The outermost diameter portion of the anvil is located opposite to the tapered surface.

9. An impact tool, characterized in that: include: motor; a rotating shaft driven by the motor in a rotation direction about a rotation axis; The hammer is capable of relative movement in the axial and rotational directions within a predetermined range relative to the rotating shaft and is pushed forward by a cam mechanism and a spring; and The anvil is rotatably provided in front of the hammer and is struck by the hammer when the hammer moves forward and rotates. The hammer comprises: a main body; a front surface wall portion provided on the front surface of the main body portion; and a claw portion extending forward from the front surface wall portion, A tapered surface is formed on the front wall portion, and the tapered surface gradually recedes as it moves away from the rotation axis. A part or the entirety of the claw portion is configured to protrude from the cone surface toward the anvil.

10. The impact tool according to claim 9, wherein: A relationship between a length L1 of the inner diameter side tip end portion of the claw portion from the main body portion and a length L2 of the outer diameter side tip end portion of the claw portion from the main body portion is L1<L2.

11. The impact tool according to claim 9, wherein: Grooves having a predetermined curvature radius are formed at connecting corners between the main body and the claw on both sides in the circumferential direction.

12. The impact tool according to claim 9, wherein: An orthogonal surface orthogonal to the rotation axis is formed on the front wall of the body, and an axial length D1 from the orthogonal surface to the rear end of the hammer is greater than an axial length D2 from the tapered surface to the rear end of the hammer.

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