Impact tools

Abstract

To provide an impact toll that is suppressed from enlarging in size.SOLUTION: An impact tool is provided with: a motor; a spindle that has a spindle shaft part and a flange part provided at a rear portion of the spindle shaft part, which is rotated by rotation force of the motor; an anvil, arranged closer to a front side than the spindle, which has an anvil shaft part to which a tip tool is attached and an anvil protrusion part that protrudes from the anvil shaft part to outside in a radial direction; and a hammer that has a base part arranged around the spindle shaft part, a front-side ring part that protrudes forward from an outer periphery portion of the base part and a hammer protrusion part that protrudes from an inner peripheral surface of the front-side ring part to inside in the radial direction to hammer the anvil protrusion part in a rotation direction. A front surface of the hammer protrusion part is arranged closer to the front side than the front surface of the base part. The base part has a groove formed at a boundary between the hammer protrusion part and the base part.SELECTED DRAWING: Figure 9

Description

Technical Field

[0006] , ,

[0001] The technology disclosed in this specification relates to impact tools.

Background Art

[0002] In the technical field related to impact tools, an impact assembly as disclosed in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to improve the workability of using an impact tool, a technology for suppressing the enlargement of the impact tool is required.

[0005] The technology disclosed in this specification aims to suppress the enlargement of impact tools.

Means for Solving the Problems

[0006] This specification discloses an impact tool. The impact tool may include a spindle that rotates by the rotational force of the motor, having a motor, a spindle shaft portion, and a flange portion provided at the rear of the spindle shaft portion; an anvil having an anvil shaft portion positioned in front of the spindle and on which a tip tool is mounted, and an anvil projection portion projecting radially outward from the anvil shaft portion; a hammer having a base portion positioned around the spindle shaft portion, a front ring portion projecting forward from the outer circumference of the base portion, and a hammer projection portion projecting radially inward from the inner circumferential surface of the front ring portion and striking the anvil projection portion in the rotational direction. The front surface of the hammer projection portion may be positioned in front of the front surface of the base portion. The base portion may have a groove provided at the boundary with the hammer projection portion. [Effects of the Invention]

[0007] The technology disclosed herein helps to suppress the increase in size of impact tools. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a front perspective view showing an impact tool according to the first embodiment. [Figure 2] Figure 2 is a rear perspective view showing an impact tool according to the first embodiment. [Figure 3] Figure 3 is a side view showing an impact tool according to the first embodiment. [Figure 4] Figure 4 is a longitudinal cross-sectional view showing an impact tool according to the first embodiment. [Figure 5] Figure 5 is a longitudinal cross-sectional view showing the upper part of the impact tool according to the first embodiment. [Figure 6] Figure 6 is a cross-sectional view showing the upper part of the impact tool according to the first embodiment. [Figure 7] Figure 7 is an exploded perspective view from the front showing a part of the impact tool according to the first embodiment. [Figure 8]Figure 8 is an exploded rear perspective view showing a part of the impact tool according to the first embodiment. [Figure 9] Figure 9 is a front perspective view showing a hammer according to the first embodiment. [Figure 10] Figure 10 is a view of the hammer according to the first embodiment, seen from the front. [Figure 11] Figure 11 is a rear perspective view showing a hammer according to the first embodiment. [Figure 12] Figure 12 is a longitudinal cross-sectional view showing a hammer according to the first embodiment. [Figure 13] Figure 13 is a cross-sectional view showing a hammer according to the first embodiment. [Figure 14] Figure 14 is a front perspective view showing a cup washer according to the first embodiment. [Figure 15] Figure 15 is a schematic diagram showing the relationship between the anvil and hammer in the comparative example. [Figure 16] Figure 16 is a schematic diagram showing the relationship between the anvil and the hammer according to the first embodiment. [Figure 17] Figure 17 is a longitudinal cross-sectional view showing the upper part of the impact tool according to the second embodiment. [Modes for carrying out the invention]

[0009] In one or more embodiments, the impact tool may include a motor, a spindle shaft portion, and a flange portion provided at the rear portion of the spindle shaft portion, a spindle that rotates by the rotational force of the motor, an anvil shaft portion disposed forward of the spindle and to which a tip tool is attached, and an anvil having an anvil protrusion protruding radially outward from the anvil shaft portion, a base portion disposed around the spindle shaft portion, a front ring portion protruding forward from the outer peripheral portion of the base portion, and a hammer having a hammer protrusion protruding radially inward from the inner peripheral surface of the front ring portion and striking the anvil protrusion in the rotational direction. The front surface of the hammer protrusion may be disposed forward of the front surface of the base portion. The base portion may have a groove provided at the boundary with the hammer protrusion.

[0010] In the above configuration, since the groove is provided in the base portion, while suppressing a decrease in the contact area between the hammer protrusion and the anvil protrusion, an increase in the size of the impact tool in the axial direction parallel to the rotation axis of the motor is suppressed. Further, since a decrease in the contact area between the hammer protrusion and the anvil protrusion is suppressed, an excessive force is prevented from being applied to the hammer protrusion. Therefore, wear of the hammer protrusion is suppressed, and shortening of the life of the hammer is suppressed.

[0011] In one or more embodiments, the base portion may have a first front surface and a second front surface that is disposed at a position different from the first front surface in the circumferential direction and is disposed forward of the first front surface. One end portion in the circumferential direction of the first front surface may be connected to the other end portion in the circumferential direction of the front surface of the hammer protrusion via a first connection surface. One end portion in the circumferential direction of the second front surface may be connected to the other end portion in the circumferential direction of the first front surface via a second connection surface. The first connection surface may be parallel to the rotation axis of the hammer and include a first plane at least partially facing the struck surface of the anvil protrusion and a first curved surface connecting the rear end portion of the first plane and the one end portion in the circumferential direction of the first front surface. The groove may be defined by the first front surface, the first connection surface, and the second connection surface.

[0012] In the above configuration, since the first flat surface and the first front surface are connected via the first curved surface, stress concentration at the boundary between the first flat surface and the first front surface is suppressed. Therefore, for example, the occurrence of cracks in the hammer is suppressed.

[0013] In one or more embodiments, the outer peripheral surface of the front ring portion may be inclined radially inward toward the front.

[0014] In the above configuration, an increase in the size of the hammer in the radial direction is suppressed. Since an increase in the size of the hammer in the radial direction is suppressed, an increase in the size of the front portion of the hammer case in the radial direction is also suppressed.

[0015] In one or more embodiments, the front ring portion may be disposed radially outside the anvil protrusion. In the axial direction, the position of the front ring portion and at least a part of the position of the anvil protrusion may be the same.

[0016] In the above configuration, since the moment of inertia of the hammer when the hammer protrusion strikes the anvil protrusion increases, the striking force can be increased.

[0017] In one or more embodiments, the second connection surface may include a second flat surface parallel to the rotation axis of the hammer and facing the first flat surface, and a second curved surface connecting the rear end portion of the second flat surface and the circumferential other end portion of the first front surface. The distance between the first flat surface and the second flat surface may be smaller than the circumferential dimension of the anvil protrusion.

[0018] In the above configuration, since the second flat surface and the first front surface are connected via the second curved surface, stress concentration at the boundary between the second flat surface and the first front surface is suppressed. Therefore, for example, the occurrence of cracks in the hammer is suppressed. Further, since the distance between the first flat surface and the second flat surface indicating the width of the groove is smaller than the circumferential dimension of the anvil protrusion, the anvil protrusion can rotate smoothly without fitting into the groove.

[0019] In one or more embodiments, the distance between the first plane and the second plane may be greater than the sum of the radii of the first surface and the radii of the second surface.

[0020] In the above configuration, a first curved surface and a second curved surface are formed inside the groove. For example, if the radii of the first and second curved surfaces are 0.5 mm, the width of the groove may be about 4 mm.

[0021] In one or more embodiments, the spindle shaft portion may include a coil spring arranged around the spindle shaft portion, a washer arranged behind the base portion and supporting the front end of the coil spring, and a support ball arranged in a support groove provided on the rear surface of the base portion and supporting the front surface of the washer. In the radial and circumferential directions, the position of the support groove and the position of at least a portion of the second front surface may be the same.

[0022] In the above configuration, the hammer can be made smaller.

[0023] In one or more embodiments, the hammer may have a rear ring portion that protrudes rearward from the outer circumference of the base portion.

[0024] In the above configuration, the moment of inertia of the hammer increases when the hammer projection strikes the anvil projection, thus increasing the striking force.

[0025] In one or more embodiments, the hammer may have a support ring portion that protrudes rearward from the inner circumference of the base portion and is supported on the spindle shaft portion via a hammer ball. In the radial direction, a washer may be positioned between the rear ring portion and the support ring portion.

[0026] In the above configuration, the front end of the coil spring fits between the rear ring and the support ring, thus suppressing the increase in size of the impact tool in the axial direction parallel to the motor's rotation axis.

[0027] In one or more embodiments, the washer may be positioned forward of the rear end of the hammer ball.

[0028] In the above configuration, the size of the impact tool in the axial direction parallel to the motor's rotation axis is suppressed.

[0029] The embodiments will be described below with reference to the drawings. In the embodiments, the positional relationships of each part will be described using the terms left, right, front, rear, top, and bottom. These terms indicate the relative position or direction with respect to the center of the impact tool 1. The impact tool 1 has a motor 6 as a power source.

[0030] In this embodiment, the direction parallel to the rotation axis AX of the motor 6 is appropriately referred to as the axial direction, the direction that circles around the rotation axis AX is appropriately referred to as the circumferential direction or rotational direction, and the radial direction of the rotation axis AX is appropriately referred to as the radial direction.

[0031] The rotation axis AX extends in the front-rear direction. One side in the axial direction is forward, and the other side in the axial direction is backward. Furthermore, in the radial direction, the position close to or approaching the rotation axis AX is appropriately referred to as the radially inward direction, and the position far from or away from the rotation axis AX is appropriately referred to as the radially outward direction.

[0032] [First Embodiment] The first embodiment will be described. <Impact Tools> Figure 1 is a front perspective view showing the impact tool 1 according to this embodiment. Figure 2 is a rear perspective view showing the impact tool 1 according to this embodiment. Figure 3 is a side view showing the impact tool 1 according to this embodiment. Figure 4 is a longitudinal cross-sectional view showing the impact tool 1 according to this embodiment.

[0033] In this embodiment, the impact tool 1 is an impact driver, which is a type of screw tightening tool. The impact tool 1 comprises a housing 2, a hammer case 4, a hammer case cover 5A, a bumper 5B, a housing cover 5C, a motor 6, a reduction mechanism 7, a spindle 8, a striking mechanism 9, an anvil 10, a tool holding mechanism 11, a fan 12, a battery mounting section 13, a trigger lever 14, a forward / reverse switching lever 15, an operation display section 16, a light 17, and a controller 18.

[0034] Housing 2 is made of synthetic resin. In this embodiment, housing 2 is made of nylon. Housing 2 includes a left housing 2L and a right housing 2R located to the right of the left housing 2L. The left housing 2L and the right housing 2R are fastened together by a plurality of screws 2S. Housing 2 is composed of a pair of split housings.

[0035] The housing 2 includes a motor housing section 21, a grip section 22, and a battery holding section 23.

[0036] The motor housing 21 houses the motor 6. The motor housing 21 has a cylindrical portion 21A and a rear plate portion 21B that is integrally connected to the rear end of the cylindrical portion 21A. The motor housing 21 houses at least a portion of the hammer case 4.

[0037] The grip portion 22 is held by the operator. The grip portion 22 extends downward from the motor housing portion 21. The trigger lever 14 is located on the upper part of the grip portion 22.

[0038] The battery holder 23 holds the battery pack 25 via the battery mounting section 13. The battery holder 23 is connected to the lower end of the grip section 22. In both the front-to-back and left-to-right directions, the external dimensions of the battery holder 23 are larger than the external dimensions of the grip section 22.

[0039] The motor housing 21 has an air intake port 19 and an exhaust port 20. The exhaust port 20 is located behind the air intake port 19. Air from the external space of the housing 2 flows into the internal space of the housing 2 through the air intake port 19. Air from the internal space of the housing 2 flows out into the external space of the housing 2 through the exhaust port 20.

[0040] The hammer case 4 houses the reduction mechanism 7, the spindle 8, the striking mechanism 9, and at least a portion of the anvil 10. At least a portion of the reduction mechanism 7 is located inside the bearing box 24. The reduction mechanism 7 includes a plurality of gears.

[0041] The hammer case 4 is made of metal. In this embodiment, the hammer case 4 is made of aluminum. The hammer case 4 is cylindrical. The hammer case 4 is connected to the front of the motor housing 21. A bearing box 24 is fixed to the rear of the hammer case 4. A cylindrical outer surface is formed on the outer circumference of the bearing box 24. A cylindrical inner surface is formed on the inner circumference of the hammer case 4. The bearing box 24 is fitted into the rear of the hammer case 4 via an O-ring 24A. The bearing box 24 and the hammer case 4 are fixed together by the coupling of the cylindrical outer surface of the bearing box 24 and the cylindrical inner surface of the hammer case 4 via the O-ring 24A. The hammer case 4 is sandwiched between the left housing 2L and the right housing 2R. At least a portion of the hammer case 4 is housed in the motor housing 21. The bearing box 24 is fixed to the motor housing 21 and the hammer case 4, respectively.

[0042] The hammer case cover 5A covers at least a portion of the surface of the hammer case 4. The bumper 5B is fitted to the front end of the hammer case 4. The hammer case cover 5A and bumper 5B protect the hammer case 4. The hammer case cover 5A and bumper 5B prevent contact between the hammer case 4 and objects around it. The housing cover 5C covers at least a portion of the surface of the housing 2.

[0043] Motor 6 is the power source for impact tool 1. Motor 6 is an inner rotor type brushless motor. Motor 6 has a stator 26 and a rotor 27. The stator 26 is supported by a motor housing 21. At least a portion of the rotor 27 is positioned inside the stator 26. The rotor 27 rotates relative to the stator 26. The rotor 27 rotates around a rotation axis AX that extends in the front-rear direction.

[0044] The reduction gear 7 connects the rotor 27 and the spindle 8. The reduction gear 7 transmits the rotation of the rotor 27 to the spindle 8. The reduction gear 7 rotates the spindle 8 at a rotational speed lower than the rotational speed of the rotor 27. The reduction gear 7 is positioned in front of the motor 6. The reduction gear 7 includes a planetary gear mechanism. The reduction gear 7 has multiple gears. The gears of the reduction gear 7 are driven by the rotor 27.

[0045] The spindle 8 rotates due to the rotational force of the rotor 27 transmitted by the reduction mechanism 7. The spindle 8 is positioned in front of at least a portion of the motor 6. The spindle 8 is positioned in front of the stator 26. At least a portion of the spindle 8 is positioned in front of the rotor 27. At least a portion of the spindle 8 is positioned in front of the reduction mechanism 7. The spindle 8 is positioned behind the anvil 10.

[0046] The striking mechanism 9 strikes the anvil 10 in the rotational direction based on the rotational force of the spindle 8, which is rotated by the motor 6. The rotational force of the motor 6 is transmitted to the striking mechanism 9 via the reduction mechanism 7 and the spindle 8.

[0047] The anvil 10 is the output shaft of the impact tool 1, which rotates based on the rotational force of the rotor 27. The anvil 10 is positioned in front of the motor 6. The anvil 10 has a tool hole 10A into which the tip tool is inserted. The tool hole 10A is located at the front end of the anvil 10. The tip tool is mounted on the anvil 10.

[0048] The tool holding mechanism 11 holds the tip tool inserted into the tool hole 10A of the anvil 10. The tool holding mechanism 11 is positioned around the front of the anvil 10. The tool holding mechanism 11 is detachable from the tip tool.

[0049] The fan 12 generates an airflow to cool the motor 6. The fan 12 is positioned behind the stator 26 of the motor 6. The fan 12 is fixed to at least a portion of the rotor 27. As the fan 12 rotates, air from the external space of the housing 2 flows into the internal space of the housing 2 through the intake port 19. The air that flows into the internal space of the housing 2 cools the motor 6 by circulating through the internal space of the housing 2. As the fan 12 rotates, the air that has circulated through the internal space of the housing 2 flows out into the external space of the housing 2 through the exhaust port 20.

[0050] The battery mounting section 13 is connected to the battery pack 25. The battery pack 25 is mounted in the battery mounting section 13. The battery pack 25 is detachable from the battery mounting section 13. The battery mounting section 13 is located below the battery holder 23. The battery pack 25 is mounted in the battery mounting section 13 by being inserted into the battery mounting section 13 from the front of the battery holder 23. The battery pack 25 is removed from the battery mounting section 13 by being pulled forward from the battery mounting section 13. The battery pack 25 includes a secondary battery. In an embodiment, the battery pack 25 includes a rechargeable lithium-ion battery. By being mounted in the battery mounting section 13, the battery pack 25 can supply power to the impact tool 1. The motor 6 is driven based on the power supplied from the battery pack 25.

[0051] The trigger lever 14 is operated by the operator to start the motor 6. Operating the trigger lever 14 switches between driving and stopping the motor 6. The trigger lever 14 is located on the grip portion 22.

[0052] The forward / reverse rotation switch lever 15 is operated by the operator. When the forward / reverse rotation switch lever 15 is operated, the rotation direction of the motor 6 is switched from one direction to the other. When the rotation direction of the motor 6 is switched, the rotation direction of the spindle 8 is switched. The forward / reverse rotation switch lever 15 is located on the upper part of the grip portion 22.

[0053] The operation display unit 16 has multiple operation buttons 16A. The operating mode of the motor 6 is switched by the operator operating the operation buttons 16A. The operation display unit 16 is provided on the battery holder 23. The operation display unit 16 is provided on the upper surface of the battery holder 23, forward of the grip 22.

[0054] Light 17 emits illumination light. Light 17 illuminates the anvil 10 and its surroundings with illumination light. Light 17 illuminates the area in front of the anvil 10 with illumination light. Light 17 also illuminates the tip tool attached to the anvil 10 and its surroundings with illumination light. Light 17 is positioned above the trigger lever 14.

[0055] The controller 18 outputs control signals for controlling the motor 6. The controller 18 includes a circuit board on which multiple electronic components are mounted. Examples of electronic components mounted on the circuit board include a processor such as a CPU (Central Processing Unit), non-volatile memory such as ROM (Read Only Memory) or storage, volatile memory such as RAM (Random Access Memory), transistors, and resistors. The controller 18 is housed in the battery holder 23.

[0056] Figure 5 is a longitudinal cross-sectional view showing the upper part of the impact tool 1 according to this embodiment. Figure 6 is a transverse cross-sectional view showing the upper part of the impact tool 1 according to this embodiment. Figure 7 is an exploded perspective view from the front showing a part of the impact tool 1 according to this embodiment. Figure 8 is an exploded perspective view from the rear showing a part of the impact tool 1 according to this embodiment.

[0057] The hammer case 4 has a first cylindrical portion 401, a second cylindrical portion 402, and a case connecting portion 403. The first cylindrical portion 401 is arranged around the striking mechanism 9. The second cylindrical portion 402 is positioned in front of the first cylindrical portion 401. The outer diameter of the second cylindrical portion 402 is smaller than the outer diameter of the first cylindrical portion 401. The case connecting portion 403 is positioned to connect the front end of the first cylindrical portion 401 and the outer circumferential surface of the second cylindrical portion 402. The rear end of the second cylindrical portion 402 protrudes rearward from the case connecting portion 403.

[0058] The motor 6 has a stator 26 and a rotor 27. The stator 26 has a stator core 28, a front insulator 29, a rear insulator 30, and a coil 31. The rotor 27 rotates around a rotation axis AX. The rotor 27 has a rotor core portion 32, a rotor shaft portion 33, a rotor magnet 34, and a sensor magnet 35.

[0059] The stator core 28 is positioned radially outward from the rotor 27. The stator core 28 includes multiple laminated steel plates. The steel plates are metal plates mainly composed of iron. The stator core 28 is cylindrical. The stator core 28 has multiple teeth that support the coil 31.

[0060] The front insulator 29 is provided at the front of the stator core 28. The rear insulator 30 is provided at the rear of the stator core 28. Both the front insulator 29 and the rear insulator 30 are electrically insulating members made of synthetic resin. The front insulator 29 is positioned to cover a portion of the surface of the teeth. The rear insulator 30 is positioned to cover a portion of the surface of the teeth.

[0061] The coil 31 is mounted on the stator core 28 via a front insulator 29 and a rear insulator 30. Multiple coils 31 are arranged. The coils 31 are arranged around the teeth of the stator core 28 via the front insulator 29 and the rear insulator 30. The coils 31 and the stator core 28 are electrically isolated by the front insulator 29 and the rear insulator 30. Multiple coils 31 are connected via a fusing terminal 38.

[0062] The rotor core portion 32 and the rotor shaft portion 33 are each made of steel. The rotor shaft portion 33 protrudes in the front-rear direction from the end face of the rotor core portion 32. The rotor shaft portion 33 includes a front shaft portion 33F that protrudes forward from the front end face of the rotor core portion 32 and a rear shaft portion 33R that protrudes rearward from the rear end face of the rotor core portion 32.

[0063] The rotor magnet 34 is fixed to the rotor core 32. The rotor magnet 34 is cylindrical. The rotor magnet 34 is arranged around the rotor core 32.

[0064] The sensor magnet 35 is fixed to the rotor core 32. The sensor magnet 35 is annular in shape. The sensor magnet 35 is positioned on the front end surface of the rotor core 32 and the front end surface of the rotor magnet 34.

[0065] A sensor board 37 is attached to the front insulator 29. The sensor board 37 is fixed to the front insulator 29 by screws 29S. The sensor board 37 has a disc-shaped circuit board with a hole in the center and a rotation detection element supported by the circuit board. At least a portion of the sensor board 37 faces the sensor magnet 35. The rotation detection element detects the position of the rotor 27 in the direction of rotation by detecting the position of the sensor magnet 35 on the rotor 27.

[0066] The rotor shaft portion 33 is rotatably supported by the rotor bearing 39. The rotor bearing 39 includes a front rotor bearing 39F that rotatably supports the front shaft portion 33F, and a rear rotor bearing 39R that rotatably supports the rear shaft portion 33R.

[0067] The front rotor bearing 39F is held in the bearing box 24. The bearing box 24 has a recess 241 that extends forward from the rear surface of the bearing box 24. The front rotor bearing 39F is positioned in the recess 241. The rear rotor bearing 39R is held in the rear plate portion 21B. The front end of the rotor shaft portion 33 is positioned in the internal space of the hammer case 4 through the opening of the bearing box 24.

[0068] The fan 12 is fixed to the rear of the rear shaft portion 33R via a bush 12A. The fan 12 is positioned between the rear rotor bearing 39R and the stator 26. The fan 12 rotates with the rotation of the rotor 27. As the rotor shaft portion 33 rotates, the fan 12 rotates together with the rotor shaft portion 33.

[0069] A pinion gear 41 is formed at the front end of the rotor shaft portion 33. The pinion gear 41 is connected to at least a part of the reduction mechanism 7. The rotor shaft portion 33 is connected to the reduction mechanism 7 via the pinion gear 41.

[0070] The reduction gear 7 has a plurality of planetary gears 42 arranged around a pinion gear 41, and an internal gear 43 arranged around the plurality of planetary gears 42. Each of the pinion gear 41, planetary gears 42, and internal gear 43 is housed in a hammer case 4. Each of the plurality of planetary gears 42 meshes with the pinion gear 41. The planetary gears 42 are rotatably supported on the spindle 8 via pins 42P. The spindle 8 is rotated by the planetary gears 42. The internal gear 43 has internal teeth that mesh with the planetary gears 42. The internal gear 43 is rotatably fixed to the bearing box 24. The internal gear 43 is always non-rotatable relative to the bearing box 24. The bearing box 24 is rotatably fixed relative to the left housing 2L and the right housing 2R.

[0071] When the rotor shaft 33 rotates due to the drive of the motor 6, the pinion gear 41 rotates, and the planetary gear 42 revolves around the pinion gear 41. The planetary gear 42 revolves while meshing with the internal teeth of the internal gear 43. Due to the revolving of the planetary gear 42, the spindle 8, which is connected to the planetary gear 42 via pin 42P, rotates at a lower rotational speed than the rotational speed of the rotor shaft 33.

[0072] The spindle 8 rotates with the rotational force of the motor 6. The spindle 8 transmits the rotational force of the motor 6 to the anvil 10 via the striking mechanism 9. The spindle 8 has a spindle shaft portion 801 and a flange portion 802 provided at the rear of the spindle shaft portion 801. The planetary gear 42 is rotatably supported on the flange portion 802 via a pin 42P. The rotation axis of the spindle 8 and the rotation axis AX of the motor 6 coincide. The spindle 8 rotates around the rotation axis AX. The spindle 8 is rotatably supported on the spindle bearing 44. A protrusion 803 is provided at the rear end of the spindle 8. The protrusion 803 projects rearward from the flange portion 802. The protrusion 803 is positioned to surround the spindle bearing 44.

[0073] The bearing box 24 is positioned around at least a portion of the spindle 8. The spindle bearing 44 is held in the bearing box 24. The bearing box 24 has a projection 242 that protrudes forward from the front surface of the bearing box 24. The spindle bearing 44 is positioned around the projection 242.

[0074] The striking mechanism 9 includes a hammer 47, a hammer ball 48, a coil spring 50, and a washer 53. The striking mechanism 9, including the hammer 47, hammer ball 48, coil spring 50, and washer 53, is housed in the first cylindrical portion 401 of the hammer case 4. The first cylindrical portion 401 is positioned around the hammer 47.

[0075] The hammer 47 is positioned in front of the reduction gear 7. The hammer 47 is positioned around the spindle shaft portion 801. The hammer 47 is supported by the spindle shaft portion 801.

[0076] The hammer 47 is rotated by the motor 6. The rotational force of the motor 6 is transmitted to the hammer 47 via the reduction gear 7 and the spindle 8. The hammer 47 is rotatable together with the spindle 8, which is rotated by the motor 6, based on the rotational force of the spindle 8. The axis of rotation of the hammer 47, the axis of rotation of the spindle 8, and the axis of rotation AX of the motor 6 coincide. The hammer 47 rotates around the axis of rotation AX.

[0077] Figure 9 is a front perspective view showing the hammer 47 according to this embodiment. Figure 10 is a front view of the hammer 47 according to this embodiment. Figure 11 is a rear perspective view showing the hammer 47 according to this embodiment. Figure 12 is a longitudinal cross-sectional view showing the hammer 47 according to this embodiment. Figure 13 is a transverse cross-sectional view showing the hammer 47 according to this embodiment.

[0078] The hammer 47 has a base portion 471, a front ring portion 472, a rear ring portion 473, a support ring portion 474, and a hammer projection portion 475.

[0079] The base portion 471 is positioned around the spindle shaft portion 801. The base portion 471 is annular in shape. The spindle shaft portion 801 is positioned inside the base portion 471.

[0080] The front ring portion 472 protrudes forward from the outer circumference of the base portion 471. The front ring portion 472 is cylindrical. The outer surface 472A of the front ring portion 472 is inclined radially inward toward the front.

[0081] The rear ring portion 473 protrudes rearward from the outer circumference of the base portion 471. The rear ring portion 473 is cylindrical.

[0082] The support ring portion 474 protrudes rearward from the inner circumference of the base portion 471. The support ring portion 474 is cylindrical. The support ring portion 474 is positioned around the spindle shaft portion 801. The support ring portion 474 is supported by the spindle shaft portion 801 via the hammer ball 48.

[0083] The hammer projection 475 protrudes radially inward from the inner circumferential surface of the front ring portion 472. The hammer projection 475 protrudes forward from the front surface of the base portion 471. The front surface 83 of the hammer projection 475 is positioned further forward than the front surface of the base portion 471. The front surface of the front ring portion 472 and the front surface 83 of the hammer projection 475 are located in the same plane. Two hammer projections 475 are arranged in the circumferential direction.

[0084] A recess 476 is formed by the rear surface of the base portion 471, the inner circumferential surface of the rear ring portion 473, and the outer circumferential surface of the support ring portion 474. The recess 476 is formed so as to recess forward from the rear surface of the hammer 47.

[0085] As shown in Figures 12 and 13, in the front-rear direction, the position of the rear end portion 473R of the outer ring portion 473 and the position of the rear end portion 474R of the support ring portion 474 are the same.

[0086] The base portion 471 has a groove 90 provided at the boundary with the hammer projection 475. The groove 90 is provided so as to extend in the radial direction. The groove 90 is provided on one circumferential side and the other circumferential side of the hammer projection 475.

[0087] The front surface of the base portion 471 includes a first front surface 81 and a second front surface 82 positioned differently from the first front surface 81 in the circumferential direction. The second front surface 82 is positioned in front of the first front surface 81.

[0088] One circumferential end of the first front surface 81 is connected to the other circumferential end of the front surface 83 of the hammer projection 475 via the first connecting surface 84. One circumferential end of the second front surface 82 is connected to the other circumferential end of the first front surface 81 via the second connecting surface 85. The groove 90 provided on the other circumferential side of the hammer projection 475 is defined by the first front surface 81, the first connecting surface 84 connected to one circumferential end of the first front surface 81, and the second connecting surface 85 connected to the other circumferential end of the first front surface 81.

[0089] The groove 90 provided on one circumferential side of the hammer projection 475 is defined by a first front surface 81, a first connecting surface 84 connected to the other circumferential end of the first front surface 81, and a second connecting surface 85 connected to one circumferential end of the first front surface 81.

[0090] The first connecting surface 84 includes a first plane 84A and a first curved surface 84B. The first plane 84A is parallel to the axis of rotation AX of the hammer 47. The first plane 84A is arranged to extend radially. In the groove 90 provided on the other circumferential side of the hammer projection 475, the first curved surface 84B is arranged to connect the rear end of the first plane 84A to one circumferential end of the first front surface 81. In the groove 90 provided on the one circumferential side of the hammer projection 475, the first curved surface 84B is arranged to connect the rear end of the first plane 84A to the other circumferential end of the first front surface 81.

[0091] The second connecting surface 85 includes a second plane 85A and a second curved surface 85B. The second plane 85A is parallel to the axis of rotation AX of the hammer 47. The second plane 85A is arranged to extend radially. In one groove 90, the second plane 85A is arranged to face the first plane 84A. In a groove 90 provided on the other circumferential side of the hammer projection 475, the second curved surface 85B is arranged to connect the rear end of the second plane 85A to the other circumferential end of the first front surface 81. In a groove 90 provided on one circumferential side of the hammer projection 475, the second curved surface 85B is arranged to connect the rear end of the second plane 85A to one circumferential end of the first front surface 81.

[0092] The hammer ball 48 is made of a metal such as steel. The hammer ball 48 is positioned between the spindle shaft portion 801 and the hammer 47. The spindle 8 has a spindle groove 804 in which at least a portion of the hammer ball 48 is positioned. The spindle groove 804 is provided on a portion of the outer circumferential surface of the spindle shaft portion 801. The hammer 47 has a hammer groove 477 in which at least a portion of the hammer ball 48 is positioned. The hammer groove 477 is provided on a portion of the inner circumferential surface of the support ring portion 474. The hammer ball 48 is positioned between the spindle groove 804 and the hammer groove 477. The hammer ball 48 can roll inside the spindle groove 804 and inside the hammer groove 477, respectively. The hammer 47 is movable along with the hammer ball 48. The spindle 8 and the hammer 47 can move relative to each other in the axial and rotational directions within the range of motion defined by the spindle groove 804 and the hammer groove 477.

[0093] The coil spring 50 is arranged around the spindle shaft portion 801. In this embodiment, the coil spring 50 includes a first coil spring 51 and a second coil spring 52 arranged in parallel with each other. The second coil spring 52 is arranged radially inward of the first coil spring 51.

[0094] The rear ends of the first coil spring 51 and the second coil spring 52 are supported by the flange portion 802. The front ends of the first coil spring 51 and the second coil spring 52 are positioned inside the recess 476. A washer 53 is positioned inside the recess 476. The front ends of the first coil spring 51 and the second coil spring 52 are supported by the washer 53. The washer 53 is ring-shaped. Each of the first coil spring 51 and the second coil spring 52 constantly generates an elastic force that moves the hammer 47 forward.

[0095] The washer 53 is positioned behind the base portion 471. The washer 53 supports the front end of the coil spring 50. In the radial direction, the washer 53 is positioned between the rear ring portion 473 and the support ring portion 474. The washer 53 is positioned inside the recess 476. The washer 53 is supported by the hammer 47 via a plurality of support balls 54. In the forward-rear range of motion of the hammer 47, when the hammer 47 is positioned furthest forward, the washer 53 is positioned forward of the rear end of the hammer ball 48.

[0096] The support ball 54 is positioned in a support groove 478 provided on the rear surface of the base portion 471. The support ball 54 supports the front surface of the washer 53. The support groove 478 is provided in a ring shape so as to surround the rotating shaft AX.

[0097] In both the radial and circumferential directions, the position of the support groove 478 is the same as the position of at least a portion of the second front surface 82. The base portion 471 has a thin-walled portion with a groove 90 and a thick-walled portion without a groove 90. The thin-walled portion includes the first front surface 81. The thick-walled portion includes the second front surface 82. The support groove 478 is provided in the thick-walled portion of the base portion 471.

[0098] The anvil 10 has an anvil shaft portion 101, an anvil projection portion 102, and an anvil convex portion 103.

[0099] The anvil shaft portion 101 is positioned in front of the spindle 8 and the hammer 47. The cutting tool is mounted on the anvil shaft portion 101. The tool hole 10A into which the cutting tool is inserted is provided so as to extend rearward from the front end of the anvil shaft portion 101.

[0100] As shown in Figure 5, in the front-rear direction, the rear end 10B of the tool hole 10A is positioned at the same location as at least a portion of the front ring portion 472. Alternatively, the rear end 10B of the tool hole 10A may be positioned at the same location as at least a portion of the base portion 471. This shortens the axial length, which is the distance between the rear end of the rear plate portion 21B and the front end of the anvil 10 in the front-rear direction.

[0101] The anvil projection 102 protrudes radially outward from the rear of the anvil shaft portion 101. The anvil projection 102 is struck in the rotational direction by the hammer projection 475. The anvil projection 102 has a striking surface 104 that is struck by the hammer projection 475. The striking surface 104 is parallel to the rotation axis AX of the anvil 10. At least a portion of the first plane 84A of the hammer projection 475 faces the striking surface 104 of the anvil projection 102.

[0102] The front ring portion 472 is positioned radially outward from the anvil projection 102. In the axial direction, the position of the front ring portion 472 is the same as the position of at least a portion of the anvil projection 102. The outer circumference of the anvil projection 102 and the inner circumference of the front ring portion 472 are separated.

[0103] The base portion 471 is positioned behind the anvil projection 102. The rear surface of the anvil projection 102 and the front surface of the base portion 471 are separated.

[0104] The anvil projection 103 protrudes rearward from the rear end of the anvil 10. The spindle 8 is positioned behind the anvil 10. A spindle recess 805 is provided at the front end of the spindle shaft portion 801. The anvil projection 103 is positioned in the spindle recess 805.

[0105] As shown in Figure 6, at least a portion of the outer circumferential surface of the spindle shaft portion 801 is the hammer sliding surface 8A on which the support ring portion 474 of the hammer 47 slides. At least a portion of the inner circumferential surface of the spindle recess 805 is the anvil sliding surface 8B on which the anvil projection 103 of the anvil 10 slides. The anvil sliding surface 8B is positioned radially inward from the hammer sliding surface 8A. In the front-rear direction, at least a portion of the hammer sliding surface 8A and the anvil sliding surface 8B overlap. In the front-rear direction, the positions of the hammer sliding surface 8A and at least a portion of the anvil sliding surface 8B are the same, so the axial length, which indicates the distance between the rear end of the rear plate portion 21B and the front end of the anvil 10 in the front-rear direction, becomes shorter.

[0106] As shown in Figures 6 and 13, at least a portion of the inner circumferential surface of the support ring portion 474 of the hammer 47 is the sliding surface 479 on which the hammer sliding surface 8A of the spindle shaft portion 801 slides. The front end of the sliding surface 479 is positioned in front of the washer 53. By positioning the sliding surface 479 in front of the washer 53, the dimensions of the hammer 47 in the front-rear direction are shortened.

[0107] The anvil 10 is rotatably supported by an anvil bearing 46. The axis of rotation of the anvil 10 coincides with the axis of rotation of the hammer 47, the axis of rotation of the spindle 8, and the axis of rotation AX of the motor 6. The anvil 10 rotates around axis AX. The anvil bearing 46 is positioned around the anvil shaft portion 101. The anvil bearing 46 is positioned inside the second cylindrical portion 402 of the hammer case 4. The anvil bearing 46 is held in the second cylindrical portion 402 of the hammer case 4. The anvil bearing 46 rotatably supports the front portion of the anvil shaft portion 101. An O-ring 45 is positioned between the anvil bearing 46 and the anvil shaft portion 101. The O-ring 45 contacts the outer circumference of the anvil shaft portion 101 and the inner circumference of the anvil bearing 46, respectively.

[0108] In this embodiment, two anvil bearings 46 are arranged in the axial direction. Two O-rings 45 are also arranged in the axial direction.

[0109] The hammer projection 475 can contact the anvil projection 102. When the motor 6 is driven while the hammer 47 and the anvil projection 102 are in contact, the anvil 10 rotates together with the hammer 47 and the spindle 8.

[0110] The anvil 10 is struck in the rotational direction by the hammer 47. For example, in screw tightening work, if the load acting on the anvil 10 becomes high, a situation may arise where the load of the coil spring 50 alone is insufficient to rotate the anvil 10. When the load of the coil spring 50 alone is insufficient to rotate the anvil 10, the rotation of the anvil 10 and the hammer 47 stops. The spindle 8 and the hammer 47 are relatively movable in the axial and circumferential directions, respectively, via the hammer ball 48. Even if the rotation of the hammer 47 stops, the rotation of the spindle 8 continues due to the power generated by the motor 6. When the spindle 8 rotates while the rotation of the hammer 47 is stopped, the hammer ball 48 moves backward, guided by the spindle groove 804 and the hammer groove 477, respectively. The hammer 47 receives force from the hammer ball 48 and moves backward along with the hammer ball 48. In other words, the hammer 47 moves backward as the spindle 8 rotates while the anvil 10 is stopped from rotating. As the hammer 47 moves backward, contact between the hammer 47 and the anvil projection 102 is released.

[0111] As described above, the coil spring 50 constantly generates an elastic force that moves the hammer 47 forward. The hammer 47, which has moved backward, moves forward due to the elastic force of the coil spring 50. When the hammer 47 moves forward, it receives a rotational force from the hammer ball 48. That is, the hammer 47 moves forward while rotating. As the hammer 47 moves forward while rotating, the hammer projection 475 comes into contact with the anvil projection 102 while rotating. As a result, the anvil projection 102 is struck in the rotational direction by the hammer projection 475. The anvil 10 is subjected to both the power of the motor 6 and the inertial force of the hammer 47. Therefore, the anvil 10 can rotate around the rotation axis AX with high torque.

[0112] The tool holding mechanism 11 includes a ball 71, a sleeve 73, and a coil spring 74.

[0113] The anvil shaft portion 101 has a support recess 76 for supporting the ball 71. The support recess 76 is formed on the outer surface of the anvil shaft portion 101. In this embodiment, two support recesses 76 are formed in the anvil shaft portion 101.

[0114] The ball 71 is movably supported in the anvil 10. The ball 71 is placed in a support recess 76. One ball 71 is placed in each support recess 76.

[0115] A through hole is formed in the anvil shaft portion 101, connecting the inner surface of the support recess 76 and the inner surface of the tool hole 10A. The diameter of the ball 71 is smaller than the diameter of the through hole. With the ball 71 supported in the support recess 76, it is positioned inside the tool hole 10A through at least a portion of the ball 71. The ball 71 can secure the tip tool inserted into the tool hole 10A. The ball 71 is movable between an engaged position that secures the tip tool and a released position that releases the tip tool from being secured.

[0116] The sleeve 73 is a cylindrical member. The sleeve 73 is positioned around the anvil shaft portion 101. The sleeve 73 is movable around the anvil shaft portion 101 between a blocking position that prevents the ball 71 from moving radially outward and a permitting position that allows radial outward movement.

[0117] The positioning of the sleeve 73 in the blocking position prevents the ball 71 from moving radially outward. The positioning of the sleeve 73 in the blocking position maintains the state in which the tip tool is fixed by the ball 71.

[0118] When the sleeve 73 is moved to the permissible position, the ball 71 is allowed to move radially outward. When the sleeve 73 is positioned in the permissible position, the tip tool can be released from being fixed in place by the ball 71.

[0119] The coil spring 74 generates an elastic force that causes the sleeve 73 to move to the stop position. The coil spring 74 is positioned around the anvil shaft portion 101. The stop position is defined as being behind the allowable position. The coil spring 74 generates an elastic force that moves the sleeve 73 backward.

[0120] In this embodiment, the impact tool 1 is equipped with a cup washer 61 to suppress contact between the anvil projection 102 and the hammer case 4. In this embodiment, the cup washer 61 suppresses contact between the front surface of the anvil projection 102 and the rear end of the second cylindrical portion 402. The second cylindrical portion 402 receives the load from the anvil projection 102 via the cup washer 61.

[0121] The cup washer 61 is supported by the hammer case 4. In this embodiment, the outer circumference of the cup washer 61 is positioned in a groove 404 provided on the inner surface of the first cylindrical portion 401. The impact tool 1 also includes a restraining member 62 that prevents the cup washer 61 from coming out of the groove 404 to the rear.

[0122] Figure 14 is a front perspective view showing a cup washer 61 according to this embodiment. The cup washer 61 has an inner ring portion 611, an outer ring portion 612, and a connecting ring portion 613.

[0123] The inner ring portion 611 is positioned to face the front surface of the anvil projection 102. The inner ring portion 611 contacts the rear end surface of the anvil bearing 46.

[0124] The outer ring portion 612 is positioned around the anvil bearing 46. The outer ring portion 612 is positioned radially outward and forward of the inner ring portion 611. In the axial direction (front-rear direction), the position of the outer ring portion 612 and the position of at least a portion of the anvil bearing 46 are the same. The outer ring portion 612 is supported by the hammer case 4. The outer ring portion 612 is positioned in a groove 404 provided on the inner circumferential surface of the first cylindrical portion 401.

[0125] At least a portion of the rear surface of the case connection portion 403 faces the front surface of the outer ring portion 612. The rear surface of the case connection portion 403 and the front surface of the outer ring portion 612 face each other with a gap in between.

[0126] The connecting ring portion 613 is positioned to connect the outer edge of the inner ring portion 611 and the inner edge of the outer ring portion 612.

[0127] In this embodiment, the anvil bearing 46 is a ball bearing. The anvil bearing 46 has an inner ring, balls, and an outer ring. The inner ring of the anvil bearing 46 is in contact with the O-ring 45. The balls are arranged radially between the inner ring and the outer ring. The balls are in contact with both the inner ring and the outer ring, respectively. Multiple balls are arranged circumferentially. The outer ring is positioned radially outward from the inner ring and the balls. The outer ring of the anvil bearing 46 is in contact with the inner circumferential surface of the second cylindrical portion 402.

[0128] In this embodiment, the inner ring portion 611 contacts the rear end surface of the outer ring of the anvil bearing 46. The inner ring portion 611 does not contact the inner ring of the anvil bearing 46.

[0129] The restraining member 62 engages with the hammer case 4 and the cup washer 61, respectively. The restraining member 62 is supported by the hammer case 4. The restraining member 62 is positioned in the groove 404. The restraining member 62 prevents the cup washer from coming out rearward. A snap ring or a C-ring is exemplified as the restraining member 62. The restraining member 62 is positioned in the groove 404 so as to contact the rear surface of the outer ring portion 612. The outer ring portion 612 is supported by the hammer case 4 via the restraining member 62.

[0130] The cup washer 61 and the restraining member 62 prevent the anvil bearing 46 from falling out to the rear.

[0131] <The action of the hammer> Figure 15 is a schematic diagram showing the relationship between the anvil and the hammer in a comparative example. Figure 16 is a schematic diagram showing the relationship between the anvil 10 and the hammer 47 in this embodiment.

[0132] As shown in Figure 16, the anvil projection 102 strikes the hammer projection 475 as the hammer 47 rotates. In this embodiment, a groove 90 is provided in the base portion 471 at a position adjacent to the hammer projection 475, so that the contact area HS between the hammer projection 475 and the anvil projection 102 does not decrease, while the size of the impact tool 1 in the axial direction is suppressed. In addition, since the contact area HS between the hammer projection 475 and the anvil projection 102 does not decrease, excessive force is not applied to the hammer projection 475. As a result, wear of the hammer projection 475 is suppressed, and the shortening of the lifespan of the hammer 47 is suppressed.

[0133] As shown in Figure 15, if the base portion 471J does not have a groove (90), the contact area HJ between the hammer projection 475J and the anvil projection 102 becomes smaller. In the example shown in Figure 15, the front surface 82J of the base portion 471J and the front surface 83J of the hammer projection 475J are connected via a flat surface 84AJ and a curved surface 84BJ. The curved surface 84BJ is provided to suppress stress concentration in the hammer projection 475J. In order for the striking surface 104 of the anvil projection 102 to be properly struck by the hammer projection 475J, the flat surface 84AJ and the striking surface 104 must be in contact, and contact between the curved surface 84BJ and the striking surface 104 must be suppressed. Because contact between the curved surface 84BJ and the striking surface 104 must be suppressed, the contact area HJ between the flat surface 84AJ and the striking surface 104 becomes smaller. By increasing the axial dimensions of the hammer projection 475J and the anvil projection 102, the contact area HJ can be increased. However, increasing the axial dimensions of the hammer projection 475J and the anvil projection 102 results in a larger impact tool in the axial direction. A larger impact tool may reduce the work efficiency when using the impact tool.

[0134] As shown in Figure 16, in this embodiment, a groove 90 is provided in the base portion 471, so that the contact area HS between the hammer projection 475 and the anvil projection 102 does not become smaller without increasing the axial dimension of the hammer projection 475. In this embodiment, the second front surface 82 of the base portion 471 and the front surface 83 of the hammer projection 475 are connected via the groove 90. The groove 90 is defined by the first front surface 81, the first plane 84A, the first curved surface 84B, the second plane 85A, and the second curved surface 85B. The first curved surface 84B suppresses stress concentration in the hammer projection 475. In order for the striking surface 104 of the anvil projection 102 to be properly struck by the hammer projection 475, it is necessary for the first plane 84A to be in contact with the striking surface 104 and for contact between the first curved surface 84B and the striking surface 104 to be suppressed. The groove 90 expands the first plane 84A to the rear. This prevents the contact area HS between the first plane 84A and the impact surface 104 from decreasing. Therefore, it is possible to suppress the increase in the size of the impact tool 1 in the axial direction while suppressing the decrease in the contact area HS between the hammer projection 475 and the anvil projection 102.

[0135] As shown in Figures 7, 10, and 16, in this embodiment, the distance Wa between the first plane 84A and the second plane 85A is smaller than the circumferential dimension of the anvil projection 102. The distance Wa represents the width of the groove 90. Also, the cross-sections of the first curved surface 84B and the second curved surface 85B are both arc-shaped. The distance Wa between the first plane 84A and the second plane 85A is greater than the sum of the radii of the first curved surface 84B and the radii of the second curved surface 85B.

[0136] <Impact tool operation> Next, the operation of the impact tool 1 will be described. For example, when performing a screw tightening operation on a workpiece, the tip tool (driver bit) used for the screw tightening operation is inserted into the tool hole 10A of the anvil 10. The tip tool inserted into the tool hole 10A is held by the tool holding mechanism 11. After the tip tool is mounted on the anvil 10, the operator grips the grip portion 22 with their right hand, for example, and pulls the trigger lever 14 with their right index finger. When the trigger lever 14 is pulled, power is supplied from the battery pack 25 to the motor 6, the motor 6 starts up, and the light 17 turns on at the same time. The start of the motor 6 causes the rotor shaft portion 33 of the rotor 27 to rotate. When the rotor shaft portion 33 rotates, the rotational force of the rotor shaft portion 33 is transmitted to the planetary gear 42 via the pinion gear 41. The planetary gear 42 rotates on its own axis while revolving around the pinion gear 41, meshing with the internal teeth of the internal gear 43. The planetary gear 42 is rotatably supported on the spindle 8 via a pin 42P. Due to the revolution of the planetary gear 42, the spindle 8 rotates at a lower rotational speed than the rotational speed of the rotor shaft 33.

[0137] When the spindle 8 rotates while the hammer projection 475 and the anvil projection 102 are in contact, the anvil 10 rotates together with the hammer 47 and the spindle 8. The rotation of the anvil 10 allows the screw tightening operation to proceed.

[0138] As the screw tightening process progresses, if a load exceeding a predetermined value is applied to the anvil 10, the rotation of the anvil 10 and the hammer 47 stops. When the spindle 8 rotates while the hammer 47 is stopped, the hammer 47 moves backward. As the hammer 47 moves backward, contact between the hammer projection 475 and the anvil projection 102 is released. The hammer 47, having moved backward, moves forward while rotating due to the elastic force of the first coil spring 51 and the second coil spring 52. As the hammer 47 moves forward while rotating, the anvil projection 102 is struck in the rotational direction by the hammer projection 475. As a result, the anvil 10 rotates around the rotation axis AX with high torque. Therefore, the screw is tightened to the workpiece with high torque.

[0139] <Effects> As described above, in this embodiment, the impact tool 1 may also include a motor 6, a spindle 8 having a spindle shaft portion 801 and a flange portion 802 provided at the rear of the spindle shaft portion 801 and rotating by the rotational force of the motor 6, an anvil 10 having an anvil shaft portion 101 positioned in front of the spindle 8 and on which the tip tool is mounted, and an anvil projection 102 projecting radially outward from the anvil shaft portion 101, and a hammer 47 having a base portion 471 positioned around the spindle shaft portion 801, a front ring portion 472 projecting forward from the outer circumference of the base portion 471, and a hammer projection 475 projecting radially inward from the inner circumferential surface of the front ring portion 472 and striking the anvil projection 102 in the rotational direction. The front surface 83 of the hammer projection 475 may be positioned in front of the front surface of the base portion 471. The base portion 471 may have a groove 90 provided at the boundary with the hammer projection portion 475.

[0140] In the above configuration, since a groove 90 is provided in the base portion 471, the contact area between the hammer projection 475 and the anvil projection 102 is suppressed, while the size of the impact tool 1 in the axial direction parallel to the rotation axis AX of the motor 6 is suppressed. In addition, since the contact area between the hammer projection 475 and the anvil projection 102 is suppressed, excessive force is suppressed from being applied to the hammer projection 475. As a result, wear of the hammer projection 475 is suppressed, and the shortening of the lifespan of the hammer 47 is suppressed.

[0141] In this embodiment, the base portion 471 may have a first front surface 81 and a second front surface 82 positioned differently from the first front surface 81 in the circumferential direction and positioned forward of the first front surface 81. One circumferential end of the first front surface 81 may be connected to the other circumferential end of the front surface 83 of the hammer projection 475 via a first connecting surface 84. One circumferential end of the second front surface 82 may be connected to the other circumferential end of the first front surface 81 via a second connecting surface 85. The first connecting surface 84 may include a first plane 84A parallel to the rotation axis AX of the hammer 47 and at least a portion of which faces the striking surface 104 of the anvil projection 102, and a first curved surface 84B connecting the rear end of the first plane 84A and one circumferential end of the first front surface 81. The groove 90 may be defined by the first front surface 81, the first connecting surface 84, and the second connecting surface 85.

[0142] In the above configuration, the first plane 84A and the first front surface 81 are connected via the first curved surface 84B, so that stress concentration at the boundary between the first plane 84A and the first front surface 81 is suppressed. Therefore, for example, the occurrence of cracks in the hammer 47 is suppressed.

[0143] In this embodiment, the outer circumferential surface 472A of the front ring portion 472 may be inclined radially inward toward the front.

[0144] In the above configuration, the enlargement of the hammer 47 in the radial direction is suppressed. Since the enlargement of the hammer 47 in the radial direction is suppressed, the enlargement of the front part of the hammer case 4 in the radial direction is also suppressed.

[0145] In this embodiment, the front ring portion 472 may be positioned radially outward from the anvil projection 102. In the axial direction, the position of the front ring portion 472 and the position of at least a portion of the anvil projection 102 may be the same.

[0146] In the above configuration, the moment of inertia of the hammer 47 increases when the hammer projection 475 strikes the anvil projection 102, thereby increasing the striking force.

[0147] In this embodiment, the second connecting surface 85 may include a second plane 85A that is parallel to the rotation axis of the hammer 47 and faces the first plane 84A, and a second curved surface 85B that connects the rear end of the second plane 85A to the other circumferential end of the first front surface 81. The distance Wa between the first plane 84A and the second plane 85A may be smaller than the circumferential dimension Wb of the anvil projection 102.

[0148] In the above configuration, the second plane 85A and the first front surface 81 are connected via the second curved surface 85B, so that stress concentration at the boundary between the second plane 85A and the first front surface 81 is suppressed. Therefore, for example, the occurrence of cracks in the hammer 47 is suppressed. In addition, since the distance Wa between the first plane 84A, which indicates the width of the groove 90, and the second plane 85A is smaller than the circumferential dimension Wb of the anvil projection 102, the anvil projection 102 can rotate smoothly without getting stuck in the groove 90.

[0149] In this embodiment, the distance Wa between the first plane 84A and the second plane 85A may be greater than the sum of the radius of the first curved surface 84B and the radius of the second curved surface 85B.

[0150] In the above configuration, a first curved surface 84B and a second curved surface 85B are formed inside the groove 90. For example, if the radii of the first curved surface 84B and the second curved surface 85B are 0.5 mm, the width of the groove may be about 4 mm.

[0151] In this embodiment, the spindle shaft portion 801 may be surrounded by a coil spring 50, a washer 53 positioned behind the base portion 471 and supporting the front end of the coil spring 50, and a support ball 54 positioned in a support groove 478 provided on the rear surface of the base portion 471 and supporting the front surface of the washer 53. In both the radial and circumferential directions, the position of the support groove 478 and the position of at least a portion of the second front surface 82 may be the same.

[0152] The above configuration allows for a miniaturization of the Hammer-47.

[0153] In this embodiment, the hammer 47 may have a rear ring portion 473 that protrudes rearward from the outer circumference of the base portion 471.

[0154] In the above configuration, the moment of inertia of the hammer 47 increases when the hammer projection 475 strikes the anvil projection 102, thereby increasing the striking force.

[0155] In this embodiment, the hammer 47 may have a support ring portion 474 that protrudes rearward from the inner circumference of the base portion 471 and is supported on the spindle shaft portion 801 via a hammer ball 48. In the radial direction, the washer 53 may be positioned between the rear ring portion 473 and the support ring portion 474.

[0156] In the above configuration, the front end of the coil spring 50 fits between the rear ring portion 473 and the support ring portion 474, thus suppressing the enlargement of the impact tool 1 in the axial direction parallel to the rotation axis AX of the motor 6.

[0157] In this embodiment, the washer 53 may be positioned forward of the rear end of the hammer ball 48.

[0158] In the above configuration, the enlargement of the impact tool 1 in the axial direction parallel to the rotation axis AX of the motor 6 is suppressed.

[0159] [Second Embodiment] A second embodiment will now be described. Components identical or equivalent to those in the above-described embodiment will be denoted by the same reference numerals, and their descriptions will be simplified or omitted.

[0160] Figure 17 is a longitudinal cross-sectional view showing the upper part of the impact tool 1 according to this embodiment. In this embodiment, the anvil bearing 460 that rotatably supports the anvil shaft portion 101 is a sliding bearing. The inner ring portion 611 of the cup washer 61 contacts the rear end surface of the anvil bearing 46.

[0161] The anvil bearing 460 is positioned around the anvil shaft portion 101. Two O-rings 45 are positioned between the anvil shaft portion 101 and the anvil bearing 460. The O-rings 45 are positioned radially inward from the anvil bearing 460. The O-rings 45 improve the sealing performance at the boundary between the anvil bearing 460 and the anvil shaft portion 101. In addition, the O-rings 45 suppress vibrations transmitted from the anvil shaft portion 101 to the anvil bearing 460.

[0162] [Other embodiments] In the above embodiment, the impact tool 1 is assumed to be an impact driver. The impact tool 1 may also be an impact wrench.

[0163] In the above-described embodiment, the power source for the impact tool 1 does not have to be the battery pack 25, but may also be a commercial power source (AC power source). [Explanation of Symbols]

[0164] 1…Impact tool, 2…Housing, 2L…Left housing, 2R…Right housing, 2S…Screw, 4…Hammer case, 5A…Hammer case cover, 5B…Bumper, 5C…Housing cover, 6…Motor, 7…Reduction mechanism, 8…Spindle, 8A…Hammer sliding surface, 8B…Spindle sliding surface, 9…Impact mechanism, 10…Anvil, 10A…Tool hole, 10B…Rear end, 11…Tool holding mechanism, 12…Fan, 12A…Bush, 13…Battery mounting section, 14…Trigger lever, 15…Forward / reverse rotation switch lever, 16…Operation display section, 16A…Operation button, 17…Light, 18…Control Roller, 19...Intake port, 20...Exhaust port, 21...Motor housing, 21A...Cylindrical part, 21B...Rear plate part, 22...Grip part, 23...Battery holder part, 24...Bearing box, 24A...O-ring, 25...Battery pack, 26...Stator, 27...Rotor, 28...Stator core, 29...Front insulator, 29S...Screw, 30...Rear insulator, 31...Coil, 32...Rotor core part, 33...Rotor shaft part, 33F...Front shaft part, 33R...Rear shaft part, 34...Rotor magnet, 35...Sensor magnet, 37...Sensor board, 38...Fusing terminal, 39...Ro Rotor bearing, 39F...front rotor bearing, 39R...rear rotor bearing, 41...pinion gear, 42...planetary gear, 42P...pin, 43...internal gear, 44...spindle bearing, 45...O-ring, 46...anvil bearing, 47...hammer, 48...hammer ball, 50...coil spring, 51...first coil spring, 52...second coil spring, 53...washer, 54...support ball, 61...cup washer, 62...restraining member, 71...ball, 73...sleeve, 74...coil spring, 76...support recess, 81...first front surface, 8 2...Second front surface, 83...Front surface, 84...First connecting surface, 84A...First flat surface, 84B...First curved surface, 85...Second connecting surface, 85A...Second flat surface, 85B...Second curved surface, 90...Groove, 101...Anvil shaft portion, 102...Anvil projection portion, 103...Anvil convex portion, 104...Surface to be struck, 241...Concave portion, 242...Convex portion, 401...First cylindrical portion, 402...Second cylindrical portion, 403...Case connecting portion, 404...Groove portion, 460...Anvil bearing, 471...Base portion, 472...Front ring portion, 472A...Outer circumference surface, 473...Rear ring portion, 473R...Rear end portion, 474...Support ring portion, 474R...Rear end portion,475...hammer projection, 476...recess, 477...hammer groove, 478...support groove, 479...sliding surface, 611...inner ring part, 612...outer ring part, 613...connecting ring part, 801...spindle shaft part, 802...flange part, 803...protrusion, 804...spindle groove, 805...spindle recess, AX... Axis of rotation.

Claims

1. Motor and, A spindle having a spindle shaft portion and a flange portion provided at the rear of the spindle shaft portion, and rotating by the rotational force of the motor, An anvil having an anvil shaft portion positioned in front of the spindle and a cylindrical anvil projection portion projecting radially outward from the anvil shaft portion, A hammer having a base portion disposed around the spindle shaft portion, a front ring portion projecting forward from the outer circumference of the base portion, and a hammer projection that projects radially inward from the inner surface of the front ring portion and strikes the anvil projection in the rotational direction, A coil spring arranged around the spindle shaft portion, A washer positioned behind the base portion and supporting the front end of the coil spring, The base portion comprises a support ball positioned in a support groove on the rear surface of the base portion and supporting the front surface of the washer, The front surface of the hammer projection is positioned in front of the front surface of the base portion. The base portion has a groove provided at the boundary with the hammer projection, The base portion has a first front surface and a second front surface which is positioned at a different location in the circumferential direction from the first front surface and is positioned in front of the first front surface. The base portion has a thin-walled portion with the groove and a thick-walled portion without the groove. The thin portion includes the first front surface, and the thick portion includes the second front surface. One circumferential end of the first front surface is connected to the other circumferential end of the front surface of the hammer projection via the first connecting surface. One circumferential end of the second front surface is connected to the other circumferential end of the first front surface via a second connecting surface. The first connecting surface includes a first plane parallel to the rotation axis of the hammer, with at least a portion facing the striking surface of the anvil projection, and a first curved surface connecting the rear end of the first plane and one circumferential end of the first front surface. The second connecting surface includes a second plane facing the first plane and a second curved surface connecting the rear end of the second plane to the other circumferential end of the first front surface. The groove is defined by the first front surface, the first connecting surface, and the second connecting surface. The radially outer end of the groove connects to the inner circumferential surface of the front ring portion. Impact tools.

2. The outer circumferential surface of the front ring portion is inclined radially inward toward the front. The impact tool according to claim 1.

3. The front ring portion is positioned radially outward from the anvil projection. In the axial direction, the position of the front ring portion and the position of at least a part of the anvil projection are the same. The impact tool according to claim 1.

4. The second connecting surface is parallel to the rotation axis of the hammer, The distance between the first plane and the second plane is smaller than the circumferential dimension of the anvil projection. The impact tool according to claim 1.

5. The distance between the first plane and the second plane is greater than the sum of the radius of the first surface and the radius of the second surface. The impact tool according to claim 4.

6. In both the radial and circumferential directions, the position of the support groove and the position of at least a portion of the second front surface are the same. The impact tool according to claim 1.

7. The hammer has a rear ring portion that protrudes rearward from the outer circumference of the base portion. The impact tool according to claim 6.

8. The hammer has a support ring portion that protrudes rearward from the inner circumference of the base portion and is supported on the spindle shaft portion via a hammer ball. In the radial direction, the washer is positioned between the rear ring portion and the support ring portion. The impact tool according to claim 7.

9. The washer is positioned forward of the rear end of the hammer ball. The impact tool according to claim 8.

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