Impact tool

Abstract

To provide an impact tool capable of reducing vibration to a fastening part generated when a hammer strikes.SOLUTION: In an impact tool, a hammer is movable in an axial direction of a driving shaft and is rotatable in a rotation direction D1 by moving a steel member 45 along a cam groove X1. The cam groove X1 includes a first part X11, a second part X12, and a third part X13. The first part X11 is formed in a rotation direction D1. The second part X12 extends from a first end E1 of the first part X11, and is inclined to the first part X11. The third part X13 extends from a second end E2 of the first part X11, and is inclined to the first part X11. The steel member 45 moves in the first part X11 of the cam groove X1 when the hammer strikes an anvil, and moves in the second part X12 or the third part X13 of the cam groove X1 before or after the hammer strikes the anvil.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates generally to impact tools, and more particularly to impact tools including a hammer. [Background technology]

[0002] Patent Document 1 discloses an impact tool in which the cam shape of the impact generating mechanism is made to have at least two stages and a curve is provided at the portion where the angle of the cam groove changes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-181774 Summary of the Invention [Problem to be solved by the invention]

[0004] In the impact tool described in Patent Document 1, a hammer, which is an impact generating mechanism, moves along a cam groove and strikes an anvil, thereby applying torque to a screw (fastening component). This causes a problem in that vibration is generated in the screw when the hammer strikes.

[0005] An object of the present disclosure is to provide an impact tool that can reduce vibrations that occur in fastening components when a hammer strikes them. [Means for solving the problem]

[0006] An impact tool according to one aspect of the present disclosure includes a drive shaft, a hammer, an anvil, and a steel member. The drive shaft has a first groove formed on its outer circumferential surface and is rotated in a rotational direction by a motor. The hammer has a second groove formed on its inner circumferential surface and is fitted to the outer circumferential surface of the drive shaft. The anvil is struck in the rotational direction by the hammer. The steel member is movably housed in a cam groove formed by the first groove and the second groove. The hammer is movable in the axial direction of the drive shaft and rotatable in the rotational direction as the steel member moves along the cam groove. The cam groove includes a first portion, a second portion, and a third portion. The first portion is formed along the rotational direction and has a first end and a second end in the rotational direction. The second portion extends from the first end and is inclined relative to the first portion. The third portion extends from the second end and is inclined relative to the first portion. The steel member moves through the first portion of the cam groove when the hammer strikes the anvil, and moves through the second or third portion of the cam groove before or after the hammer strikes the anvil. [Effects of the Invention]

[0007] According to the present disclosure, there is an advantage in that vibrations to the fastening component that occur when the hammer strikes can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing the appearance of an impact tool according to this embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the impact tool. [Figure 3] FIG. 3 is an external perspective view showing a drive shaft of the impact tool. [Figure 4] FIG. 4 is an external perspective view showing the hammer of the impact tool. [Figure 5] FIG. 5 is a development view of a cam groove in the impact tool. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments and modifications described below are merely examples of the present disclosure. The present disclosure is not limited to the embodiments and modifications, and various modifications other than these embodiments and modifications are possible depending on the design, etc., as long as they do not deviate from the technical concept of the present disclosure. The drawings described in the following embodiments and modifications are schematic drawings, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0010] (Embodiment) (1) Overview An outline of an impact tool 1 according to this embodiment will be described below with reference to FIGS.

[0011] The impact tool 1 (see FIG. 1) according to this embodiment is a portable power tool. The impact tool 1 is, for example, an electric impact wrench, and is used for tightening fastening parts (screws, bolts, nuts, etc.) to fastening objects (electrical appliances, furniture, etc.) or for loosening fastening parts from the fastening objects.

[0012] As shown in FIG. 2, the impact tool 1 includes a drive shaft 41, a hammer 42, an anvil 44, and a steel member 45. As shown in FIG. 3, the drive shaft 41 has a groove (first groove) 412 formed in its outer circumferential surface 411, and is rotated in a rotation direction D1 by the motor 3. As shown in FIGS. 2 and 4, the hammer 42 has a groove (second groove) 422 formed in its inner circumferential surface 421, and is fitted into the outer circumferential surface 411 of the drive shaft 41. The anvil 44 is struck in the rotation direction D1 by the hammer 42. The steel member 45 is movably housed in a cam groove X1 formed by the first groove 412 and the second groove 422.

[0013] The hammer 42 is movable in the axial direction D2 (see FIG. 2) of the drive shaft 41 and rotatable in the rotational direction D1 as a result of the steel member 45 moving along the cam groove X1. As shown in FIG. 5, the cam groove X1 includes a first portion X11, a second portion X12, and a third portion X13. The first portion X11 is formed along the rotational direction D1 and has a first end E1 and a second end E2 in the rotational direction D1. The second portion X12 extends from the first end E1 of the first portion X11 and is inclined with respect to the first portion X11. Similarly, the third portion X13 extends from the second end E2 of the first portion X11 and is inclined with respect to the first portion X11.

[0014] The steel member 45 moves in the first portion X11 of the cam groove X1 when the hammer 42 strikes the anvil 44. On the other hand, the steel member 45 moves in the second portion X12 or the third portion X13 of the cam groove X1 before or after the hammer 42 strikes the anvil 44.

[0015] As described above, the steel member 45 moves along the rotation direction D1 when the hammer 42 strikes the anvil 44. Because the hammer 42 moves in the same direction as the steel member 45, in the impact tool 1 of this embodiment, the hammer 42 moves along the rotation direction D1 when striking the anvil 44. That is, the hammer 42 strikes the anvil 44 along the rotation direction D1. In short, the hammer 42 can suppress the component force in the axial direction D2 of the drive shaft 41 that is applied to the anvil 44. As a result, the impact tool 1 of this embodiment has the advantage of being able to reduce vibrations that are generated in the fastening component when the hammer 42 strikes.

[0016] (2) Detailed configuration (2-1) Overall The detailed configuration of the impact tool 1 of this embodiment will be described below with reference to FIGS.

[0017] In the following description, as shown in FIG. 2, the axial direction D2 of the drive shaft 41 is defined as the front-to-rear direction, the anvil 44 side as viewed from the hammer 42 is defined as the front, and the hammer 42 side as viewed from the anvil 44 is defined as the rear. Also, in the following description, as shown in FIG. 1, the direction in which a second portion 22 of the housing 2 described below and a grip portion 23 described below are aligned is defined as the up-down direction, the second portion 22 side as viewed from the grip portion 23 is defined as the top, and the grip portion 23 side as viewed from the second portion 22 is defined as the bottom. Also, a direction perpendicular to the front-to-rear direction and the up-to-down direction is defined as the left-to-right direction. However, these definitions are not intended to define the direction in which the impact tool 1 is used.

[0018] As shown in Figures 1 and 2, the impact tool 1 includes a housing 2, a motor 3, a transmission mechanism 4, a first holder 51, a second holder 52, a control unit 81, an operating unit 82, and an elastic member 9.

[0019] (2-2) Housing As shown in Figure 2, the housing 2 accommodates the motor 3, the transmission mechanism 4, the first holder 51, the second holder 52, the control unit 81, and the elastic member 9. The housing 2 has a first section 21, a second section 22, a grip section 23, and an attachment section 24. The first section 21 accommodates at least a portion of the anvil 44 and the hammer 42. The second section 22 accommodates the motor 3.

[0020] (Part 1) 1 and 2, the first portion 21 includes a front wall 211, a first side wall 212, a second side wall 213, and four mounting pieces 214. Note that three mounting pieces 214 are shown in FIG.

[0021] The front wall 211 has a disk shape. An insertion hole 215 having a circular cross section is formed in the center of the front wall 211. An anvil shaft 441 (described later) of the anvil 44 housed in the first section 21 is inserted into the insertion hole 215. The tip (front end) of the anvil shaft 441 is located forward of the front end of the first section 21.

[0022] The first side wall 212 has a cylindrical shape extending rearward from the outer peripheral edge of the front wall 211. The second side wall 213 has a cylindrical shape extending rearward from the rear end of the first side wall 212. The radial dimension of the first side wall 212 is smaller than the radial dimension of the second side wall 213.

[0023] 1, the four mounting pieces 214 are formed in a convex shape that protrudes outward from the peripheral edge of the rear end of the second side wall 213. Each of the four mounting pieces 214 is formed with an insertion hole through which a screw is inserted.

[0024] 2, the first section 21 has an internal space with a circular cross section that is surrounded by a front wall 211, a first side wall 212, and a second side wall 213 and is open at the rear, and accommodates at least a portion of the anvil 44 and the hammer 42 in the internal space. The internal space of the first section 21 also accommodates a portion of the drive shaft 41 (a front portion of the drive shaft 41) and a portion of the first holder 51 (a front portion of the holder 5).

[0025] (Second part) 1 and 2, the second portion 22 includes a rear wall 221, a side wall 222, four mounting pieces 223, and a partition wall 224. Note that three mounting pieces 223 are shown in FIG.

[0026] The rear wall 221 has a disk shape. The side wall 222 has a cylindrical shape and extends forward from the outer periphery of the rear wall 221.

[0027] The four mounting pieces 223 are formed in a convex shape that protrudes outward from the periphery of the front end of the side wall 222. Each of the four mounting pieces 223 is formed with a screw hole into which a screw is screwed.

[0028] 2, the second section 22 has an internal space with a circular cross section that is surrounded by a rear wall 221 and a side wall 222 and is open to the front, and accommodates the motor 3 in the internal space. The internal space of the second section 22 also accommodates a part of the drive shaft 41 (the rear part of the drive shaft 41), a part of the first holder 51 (the rear part of the first holder 51), and the second holder 52.

[0029] The first part 21 and the second part are connected by screwing. More specifically, the insertion holes provided in each of the four mounting pieces 214 in the first part 21 correspond one-to-one to the screw holes provided in each of the four mounting pieces 223 in the second part 22, and the corresponding insertion holes and screw holes are aligned. Then, a screw is inserted through the insertion hole of the mounting piece 214 and screwed into the corresponding screw hole of the mounting piece 223, thereby connecting the first part 21 and the second part 22.

[0030] The partition wall 224 is formed slightly rearward of the front end (front opening) of the internal space of the second section 22 so as to face the rear wall 221 in the front-rear direction. The partition wall 224 is disk-shaped. A through-hole 2241 with a circular cross section is formed in the center of the partition wall 224.

[0031] (Grip part) The grip portion 23 protrudes from the second portion 22. More specifically, the grip portion 23 protrudes from a side surface of the second portion 22. The grip portion 23 protrudes downward from the second portion 22. An operator can grasp the grip portion 23 to perform the work of fastening a fastening member such as a screw.

[0032] (Attachment part) As shown in FIG. 1, the mounting portion 24 has a rectangular parallelepiped shape. The mounting portion 24 is connected to the lower end of the grip portion 23. A rechargeable battery pack (not shown) is detachably attached to the mounting portion 24. The impact tool 1 operates using the battery pack as a power source. That is, the battery pack is a power source that supplies power to drive the motor 3. The battery pack may or may not be a component of the impact tool 1. The battery pack includes a battery pack configured by connecting multiple secondary batteries (e.g., lithium ion batteries) in series, and a case that houses the battery pack.

[0033] (2-3) Motor As shown in Figure 1, the motor 3 is housed in the rear part of the second section 22. The motor 3 includes a rotor having a rotating shaft 31 (see Figure 2) and permanent magnets, and a stator having coils. Electromagnetic interaction between the permanent magnets and the coils causes the rotor to rotate relative to the stator.

[0034] The motor 3 is a servo motor. The torque and rotation speed of the motor 3 change according to the control by the control unit 81 (servo driver). More specifically, the control unit 81 controls the operation of the motor 3 by feedback control, which controls the torque and rotation speed of the motor 3 so as to approach target values.

[0035] (2-4) Operation section As shown in Figures 1 and 2, the operating unit 82 protrudes from the grip portion 23. The operating unit 82 accepts operations for controlling the rotation of the rotary shaft 31 of the motor 3. By pulling the operating unit 82, the motor 3 can be switched on and off. Furthermore, the rotation speed of the rotary shaft 31 can be adjusted by the amount of pulling the operating unit 82. The greater the amount of pulling, the faster the rotation speed of the rotary shaft 31.

[0036] (2-5) Control unit The control unit 81 includes, for example, a microcontroller. The control unit 81 rotates or stops the rotating shaft 31 according to the pulling amount of the operation of pulling the operating unit 82, and also controls the rotation speed of the rotating shaft 31. The control unit 81 controls the rotation speed of the rotating shaft 31 by feedback control that controls the torque and rotation speed of the motor 3 so that they approach target values. The control unit 81 changes the rotation speed of the rotating shaft 31 by, for example, changing the power supplied to the motor 3.

[0037] The control unit 81 can change the rotation speed of the rotary shaft 31 to change the rotation speed of the anvil shaft 441 of the anvil 44 and the tool bit.

[0038] (2-6) Transmission mechanism As shown in FIG. 2, the transmission mechanism 4 includes an impact mechanism 40, a planetary gear mechanism 48, a first bearing 491, a second bearing 492, and a third bearing 493.

[0039] The impact mechanism 40 is configured to perform an impact operation that applies an impact force in the rotational direction of the anvil 44 when the tightening torque (load torque) that tightens the fastening parts exceeds a predetermined value. The impact force acts on a tool tip (not shown) attached to the tip of the anvil shaft 441 of the anvil 44. This makes it possible to apply a larger tightening torque to the fastening parts. In other words, the impact tool 1 is an electric impact driver that performs fastening work such as screw tightening while performing an impact operation by the impact mechanism 40.

[0040] The impact mechanism 40 includes a drive shaft 41, a hammer 42, a coil spring 43, an anvil 44, and two steel members 45. The drive shaft 41, the hammer 42, the coil spring 43, and the two steel members 45 are housed in the internal space of the first section 21. Furthermore, an anvil body 440, anvil claws 442, and a rear portion of an anvil shaft 441 (described later) of the anvil 44 are housed in the internal space of the first section 21. The front portion of the anvil shaft 441 is exposed to the front side of the first section 21.

[0041] The planetary gear mechanism 48 is housed in a first holder 51 and a second holder 52, and is located in a portion of the housing 2 where the first portion 21 and the second portion are connected in the front-to-rear direction (see FIG. 2). The first holder 51 and the second holder 52 rotatably hold at least one gear included in the planetary gear mechanism 48. Details of the first holder 51 and the second holder 52 will be described later.

[0042] As shown in FIGS. 2 and 3 , the planetary gear mechanism 48 includes a sun gear 481, three planetary gears 482, and an annular internal gear 483. The sun gear 481 is located at the center of the internal gear 483, is connected to the front end of the rotary shaft 31 of the motor 3, and rotates together with the rotary shaft 31. Each of the three planetary gears 482 meshes with the sun gear 481 and the internal gear 483 between the sun gear 481 and the internal gear 483, and rotates on its own axis by the driving force transmitted from the sun gear 481 and revolves around the internal gear 483. A cylindrical drive shaft 41 extending in the front-to-rear direction is disposed in front of the planetary gear mechanism 48. The drive shaft 41 is connected to each of the three planetary gears 482, and the orbital motion of the three planetary gears 482 is transmitted to the drive shaft 41, causing the drive shaft 41 to rotate. 2 and 3, a flange 413 is integrally formed on the rear end of the drive shaft 41. The shaft portions (not shown) of the three planetary gears 482 are inserted into the flange 413, thereby connecting the drive shaft 41 to each of the three planetary gears 482. Note that in FIG. 3, the multiple teeth provided on the outer periphery of each of the three planetary gears 482 are omitted from the illustration, and specifically, each of the three planetary gears 482 is illustrated as a simplified cylindrical shape.

[0043] The planetary gear mechanism 48 is a reduction gear device that converts the rotational speed and torque of the rotating shaft 31 of the motor 3 into a rotational speed and torque for rotating the fastening member. The torque of the rotating shaft 31 of the motor 3 is transmitted to the drive shaft 41 via the planetary gear mechanism 48. This causes the drive shaft 41 to rotate in a rotational direction D1 (see FIG. 3). The "rotational direction D1" here refers to the circumferential direction of the drive shaft 41, and is a direction intersecting with the axial direction D2 of the drive shaft 41.

[0044] As shown in FIGS. 2 and 3, two grooves 412, each having a semicircular cross section, are formed in the outer peripheral surface 411 of the drive shaft 41. Each of the two grooves 412 has a first portion 4121, a second portion 4122, and a third portion 4123. The first portion 4121 is formed along the circumferential direction of the drive shaft 41 (i.e., the rotation direction D1). The first portion 4121 has a first end and a second end in the circumferential direction of the drive shaft 41. The second portion 4122 is formed from the first end of the first portion 4121 toward the rear. Similarly, the third portion 4123 is formed from the first end of the first portion 4121 toward the rear. In other words, each of the two grooves 412 is formed so as to form a trapezoidal curve with its upper base facing forward when viewed from the normal direction of the outer peripheral surface 411 of the drive shaft 41. The "trapezoidal curve" referred to here is a curve formed by a pair of legs and an upper base of a trapezoid with rounded corners. The two grooves 412 are aligned along the circumferential direction of the drive shaft 41 (i.e., the rotation direction D1). When viewed from the normal direction of the outer circumferential surface 411 of the drive shaft 41, each of the two grooves 412 is symmetrical with respect to a line that passes through the center of each of the two grooves 412 and extends in the axial direction D2 of the drive shaft 41. Each of the two grooves 412 corresponds to a first groove in the present disclosure. In the following description, each of the two grooves 412 may be referred to as a first groove 412.

[0045] In this embodiment, as shown in FIG. 3 , two first groove portions 412 are formed on the outer peripheral surface 411 of the drive shaft 41 over the entire circumferential direction. The two first groove portions 412 are connected by two connecting portions 4124 in the rotational direction D1 of the drive shaft 41. Note that FIG. 3 shows only one connecting portion 4124. Each of the two connecting portions 4124 connects one of the two first groove portions 412 to the other first groove portion 412. More specifically, one of the two connecting portions 4124 connects the second portion 4122 of one of the two first groove portions 412 to the second portion 4122 of the other first groove portion 412. Similarly, the remaining connection portion 4124 connects the third portion 4123 of one of the two first groove portions 412 to the third portion 4123 of the remaining first groove portion 412 .

[0046] The third bearing 493 is disposed between a first side wall 522 of the second holder 52 (described later) and the drive shaft 41. The third bearing 493 rotatably supports the drive shaft 41. The third bearing 493 is formed of a roller bearing that supports the outer peripheral surface 411 of the drive shaft 41.

[0047] The hammer 42 is made of metal. The hammer 42 is fitted onto the outer peripheral surface 411 of the drive shaft 41. The hammer 42 rotates in a rotational direction D1 (see FIG. 4) by torque transmitted via the drive shaft 41, thereby rotating the anvil 44 in the rotational direction D1. That is, the direction in which the drive shaft 41 rotates and the direction in which the hammer 42 rotates are the same rotational direction D1. Furthermore, the hammer 42 moves (translates) back and forth relative to the anvil 44 while rotating, thereby applying a striking force to the anvil 44 in the rotational direction D1. That is, the anvil 44 is struck by the hammer 42 in the rotational direction D1.

[0048] Specifically, as shown in Figures 2 and 4, the hammer 42 includes a cylindrical hammer body 420 and a pair of protrusions, namely, hammer claws 423. The pair of hammer claws 423 are arranged at 180-degree intervals on the circular front surface of the hammer body 420. A through-hole 424 that penetrates in the front-rear direction is formed in the center of the hammer body 420 by a cylindrical body extending in the front-rear direction. The cross section of the through-hole 424 is circular. The drive shaft 41 penetrates the through-hole 424 in the front-rear direction.

[0049] As shown in FIGS. 2 and 4 , two grooves 422, each having a semicircular cross section, are formed in the inner circumferential surface 421 of the through hole 424 of the hammer body 420. When viewed from the normal direction of the inner circumferential surface 421, each of the two grooves 422 is formed to have a trapezoidal shape with an upper base at the rear. The two grooves 422 are aligned along the circumferential direction of the through hole 424 (i.e., the rotational direction D1). When viewed from the normal direction of the inner circumferential surface 421, each of the two grooves 422 is line-symmetrical with respect to a line that passes through the center of each of the two grooves 422 and extends in a direction perpendicular to the circumferential direction of the through hole 424 (i.e., the axial direction D2 of the drive shaft 41). Each of the two grooves 422 corresponds to a second groove in the present disclosure. In the following description, each of the two grooves 422 may be referred to as the second groove 422.

[0050] Two steel members 45 are sandwiched between the two first groove portions 412 of the drive shaft 41 and the two second groove portions 422 of the hammer 42. That is, each of the two steel members 45 is movably housed in a cam groove X1 (see FIG. 2) that is made up of the first groove portions 412 and the second groove portions 422. When the hammer 42 is fitted onto the outer circumferential surface 411 of the drive shaft 41, the cam groove X1 is made up of one first groove portion 412 and one second groove portion 422 that face each other. More specifically, when the hammer 42 is fitted on the outer peripheral surface 411 of the drive shaft 41 and the drive shaft 41 rotates in the rotation direction D1, the cam groove X1 is a groove that regulates the trajectory of the steel member 45 sandwiched between the one first groove portion 412 and the one second groove portion 422, by using one first groove portion 412 and one second groove portion 422 that face each other. The impact tool 1 of this embodiment has two cam grooves X1. The two cam grooves X1 and the two steel members 45 constitute a cam mechanism. That is, the torque of the drive shaft 41 is transmitted to the hammer 42 via the two steel members 45, causing the hammer 42 to rotate. The steel member 45 is housed in the cam groove X1 and can move within the cam groove. As the two steel members 45 move along the cam groove X1, the hammer 42 becomes movable in the axial direction D2 (front-rear direction) relative to the drive shaft 41 and rotatable in the rotation direction D1.

[0051] As shown in FIG. 5, each of the two cam grooves X1 has a first portion X11, a second portion X12, and a third portion X13. FIG. 5 illustrates the shape of the cam groove X1 as it would appear when developed in the rotational direction D1. The first portion X11 is formed along the rotational direction D1 and has a first end E1 (the left end in FIG. 5) and a second end E2 (the right end in FIG. 5) in the rotational direction D1. The second portion X12 extends from the first end E1 and is inclined with respect to the first portion X11. That is, the second portion X12 extends from the first end E1 along a direction intersecting the rotational direction D1. Similarly, the third portion X13 extends from the second end E2 and is inclined with respect to the first portion X11. That is, the third portion X13 extends from the second end E2 along a direction intersecting the rotational direction D1. The second portion X12 extends in a direction different from the direction in which the third portion X13 extends. More specifically, in Fig. 5, the second portion X12 extends in a lower left direction, and the third portion X13 extends in a lower right direction.

[0052] Assume that the rotation direction D1 of the drive shaft 41 is the forward direction. In the above case, when the hammer 42 strikes the anvil 44, the steel member 45 moves through the first portion X11 of the cam groove X1, i.e., is located at position P1 (see FIG. 5). On the other hand, before or after the hammer 42 strikes the anvil 44, the steel member 45 moves through the second portion X12 of the cam groove X1, i.e., is located at position P2 (see FIG. 5). In short, in the above case, the steel member 45 moves within the cam groove along the first locus T1.

[0053] On the other hand, assume that the rotation direction D1 of the drive shaft 41 is in the opposite direction. In the above case, when the hammer 42 strikes the anvil 44, the steel member 45 moves through the first portion X11 of the cam groove X1, i.e., is located at position P1. On the other hand, before or after the hammer 42 strikes the anvil 44, the steel member 45 moves through the third portion X13 of the cam groove X1, i.e., is located at position P3 (see FIG. 5). In short, in the above case, the steel member 45 moves within the cam groove along the second locus T2.

[0054] As described above, in the impact tool 1 of this embodiment, each of the two steel members 45 moves along the first portion X11 of the cam groove X1 when the hammer 42 strikes the anvil 44, and moves along the second portion X12 or the third portion X13 of the cam groove X1 before or after the hammer 42 strikes the anvil 44. As a result, the steel member 45 moves along the rotational direction D1 when the hammer 42 strikes the anvil 44. Because the hammer 42 moves in the same direction as the steel member 45, in the impact tool 1 of this embodiment, the hammer 42 moves along the rotational direction D1 when striking the anvil 44. That is, the hammer 42 strikes the anvil 44 along the rotational direction D1. In other words, the hammer 42 can suppress the component force in the axial direction D2 of the drive shaft 41 that is applied to the anvil 44. As a result, the impact tool 1 of this embodiment has the advantage of being able to reduce vibrations in the fastening component that occur when the hammer 42 strikes.

[0055] In this embodiment, each of the two cam grooves X1 has a modified trapezoidal shape. The term "modified trapezoidal shape" used here refers to a modified trapezoidal shape, specifically a shape obtained by rounding the corners of a trapezoid. More specifically, each of the two cam grooves X1 has a shape such that the cam curve of each of the two steel members 45 is a modified trapezoidal curve, i.e., a shape that realizes continuous changes in acceleration in each of the two steel members 45. The term "cam curve of the two steel members 45" used here refers to the motion curve of each of the two steel members 45 moving along the corresponding cam groove X1. In other words, in each of the two cam grooves X1, the portion where the first portion X11 and the second portion X12 are connected and the portion where the first portion X11 and the third portion X13 are connected are smoothly curved rather than bent. Furthermore, when viewed from the normal direction of the plane of each of the two cam grooves X1 (the direction perpendicular to the paper surface of FIG. 5 ), each of the two cam grooves X1 is line-symmetric with respect to a line that passes through the center of each of the two cam grooves X1 and extends in a direction perpendicular to the longitudinal direction (rotational direction D1) of the first portion X11 (i.e., the axial direction D2 of the drive shaft 41). The two cam grooves X1 are line-symmetric with respect to the center line of the rotational direction D1. That is, the longitudinal dimension of the second portion X12 and the longitudinal dimension of the third portion X13 in each of the two cam grooves X1 are the same. With the above configuration, it is possible to suppress changes in acceleration when each of the two steel members 45 moves through the cam groove X1. That is, it is possible to suppress changes in acceleration when the hammer 42 moves. As a result, the impact tool 1 of this embodiment has the advantage of being able to further reduce vibrations in the fastening component that occur when the hammer 42 strikes.

[0056] In this embodiment, each of the two steel members 45 has a spherical shape. This configuration allows the steel members 45 to move easily within the cam groove, which makes it easier for the hammer 42 to move in the axial direction D2 (front-rear direction) and rotate in the rotational direction D1. This has the advantage that the hammer 42 can efficiently apply a striking force to the anvil 44 in the rotational direction D1.

[0057] Furthermore, a coil spring 43 is provided behind the hammer body 420, and the coil spring 43 applies a spring force in the forward direction to the hammer 42. The hammer 42 moves backward against the spring force of the coil spring 43, and the retracted hammer 42 moves forward due to the spring force.

[0058] The anvil 44 is disposed in front of the hammer 42. The anvil 44 is made of metal. The anvil 44 rotates in a rotational direction D1 due to torque transmitted from the rotating hammer 42. In other words, the direction in which the hammer 42 rotates and the direction in which the anvil 44 rotates are the same rotational direction D1.

[0059] Specifically, as shown in FIG. 2 , the anvil 44 includes an anvil body 440, an anvil shaft 441, and a pair of anvil claws 442. The anvil body 440 is cylindrical. The anvil shaft 441 is connected to the anvil body 440 and protrudes forward in the axial direction from the front surface of the anvil body 440. The anvil shaft 441 corresponds to an output shaft protruding forward from the front surface of the anvil body 440. The pair of anvil claws 442 are arranged at 180-degree intervals on the outer periphery of the anvil body 440 and protrude from the side surfaces of the anvil body 440 in the radial direction of the anvil body 440. The anvil body 440 faces the hammer body 420 in the front-rear direction. As the hammer 42 rotates, the anvil claws 442 collide with the hammer claws 423 in the rotation direction D1 of the hammer 42.

[0060] A tool bit (not shown) is attached to the tip (front end) of the anvil shaft 441. That is, the anvil shaft 441 has a structure capable of holding the tool bit at its tip in the direction of the rotation axis of the hammer 42. The tool bit is a bit for rotating fastening parts such as bolts and nuts.

[0061] The outer peripheral surface of the anvil 44 is journaled by a first bearing 491 and a second bearing 492 (see FIG. 2). The first bearing 491 and the second bearing 492 rotatably support the anvil 44. The first bearing 491 is configured as a roller bearing that journals the outer periphery of the anvil body 440. The second bearing 492 is configured as a ball bearing that journals the outer periphery of the anvil shaft 441. The first bearing 491 and the second bearing 492 suppress oscillation, vibration, etc. of the rotating anvil 44. It is sufficient that the first bearing 491 and the second bearing 492 have a configuration that at least rotatably supports the anvil shaft 441.

[0062] Then, as the drive shaft 41 rotates in the rotation direction D1 due to torque transmitted from the motor 3 via the planetary gear mechanism 48, the hammer 42 receives torque transmitted from the drive shaft 41 via the above-mentioned cam mechanism and rotates in the rotation direction D1 around the drive shaft 41 as its rotation axis. When the hammer 42 is not performing a striking operation, the hammer 42 and the anvil 44 rotate together while the pair of hammer claws 423 of the hammer 42 contacts the pair of anvil claws 442 of the anvil 44 in the rotation direction. When the anvil 44 rotates in the rotation direction D1, the anvil shaft 441 also rotates, and the tool bit also rotates in the rotation direction D1. As a result, the fastening member also rotates in the rotation direction D1 due to the torque of the tool bit.

[0063] As the fastening member rotates and is tightened into a screw hole or the like, the axial force increases, and the tightening torque of the fastening member increases. As the tightening torque increases, the component of the force generated between the hammer 42 and the anvil 44 that moves the hammer 42 backward also increases. When the tightening torque reaches a predetermined value or greater, the hammer 42 moves backward against the spring force of the coil spring 43. As the hammer 42 moves backward, the pair of hammer claws 423 of the hammer 42 climb over the two anvil claws 442 of the anvil 44, and the hammer 42 rotates. Thereafter, the hammer 42 moves forward due to the spring force of the coil spring 43. When the drive shaft 41 rotates approximately half a turn, the pair of hammer claws 423 of the hammer 42 collide with the side surfaces of the pair of anvil claws 442 of the anvil 44. That is, the hammer claws 423 collide with the anvil claws 442 every time the drive shaft 41 rotates approximately half a turn. That is, the hammer 42 applies a striking force (rotational striking force) to the anvil 44 every time the drive shaft 41 makes approximately a half rotation while repeatedly moving backward and forward.

[0064] (2-7) Holding stand The first holder 51 and the second holder 52 hold the drive shaft 41. The first holder 51 and the second holder 52 are housed in the housing 2 and are held by the housing 2 between the hammer 42 and the motor 3.

[0065] Specifically, the first holder 51 is held on the inner surface of the housing 2 so that the outer peripheral surface of the first holder 51 faces the portion where the first section 21 and the second section of the housing 2 are connected. As shown in FIG. 2 , the first holder 51 has a cylindrical shape and includes a rear wall 511 and a side wall 512. The rear wall 511 is an annular plate member. The thickness direction of the rear wall 511 is along the front-to-rear direction. The side wall 512 has a cylindrical shape that extends forward from the outer peripheral edge of the rear wall 511.

[0066] The second holder 52 has a cylindrical shape and includes a main wall 521, a first side wall 522, and a second side wall 523. The main wall 521 is an annular plate member. The thickness direction of the main wall 521 is along the front-rear direction. The first side wall 522 has a cylindrical shape extending forward from the outer circumferential edge of the main wall 521. The outer circumferential surface of the first side wall 522 of the second holder 52 contacts the inner circumferential surface of the rear wall 511 of the first holder 51. The second side wall 523 has a cylindrical shape extending forward from the inner circumferential edge of the main wall 521. A protrusion 524 protruding toward the rotation shaft 31 of the motor 3 is formed on the inner circumferential surface of the second side wall 523. The protrusion 524 in this embodiment has a circular shape with an insertion hole 5241 provided in the center.

[0067] The second holder 52 is disposed in front of the partition wall 224 with its main wall 521 facing the partition wall 224 of the second section 22. The outer peripheral surface of the second side wall 523 of the second holder 52 contacts the inner peripheral edge of the insertion hole 2241 of the partition wall 224. The rotating shaft 31 of the motor 3 passes through the insertion hole 2241 of the partition wall 224 and the insertion hole 5241 of the protrusion 524 on the second side wall 523 of the second holder 52, and the tip (front end) of the rotating shaft 31 is located inside the first holder 51. The outer peripheral surface of the side wall 512 of the first holder 51 is in close contact with the portion of the housing 2 where the first section 21 and the second section are connected, so that the second holder 52 is held by the housing 2.

[0068] The planetary gear mechanism 48 is housed inside the side wall 512 of the first holder 51. An annular internal gear 483 of the planetary gear mechanism 48 is attached to the side wall 512 along the inner periphery of the side wall 512. A sun gear 481 of the planetary gear mechanism 48 is located at the center of the annular internal gear 483. The front end of the rotating shaft 31 of the motor 3 is fitted into the rear end of the sun gear 481, and the sun gear 481 rotates together with the rotating shaft 31. The three planetary gears 482 of the planetary gear mechanism 48 are meshed with the sun gear 481 and the internal gear 483 between the sun gear 481 and the internal gear 483. The shaft portions of the three planetary gears 482 are inserted into the flange 413 of the drive shaft 41, so that the drive shaft 41 is connected to the three planetary gears 482.

[0069] (2-8) Elastic member The elastic member 9 is made of an elastic material and is provided at at least one end in the axial direction D2 (front-rear direction) of the drive shaft 41. In this embodiment, the elastic member 9 is provided at both the front end and the rear end of the drive shaft 41. This configuration has the advantage of further reducing vibrations to the fastening component that occur when the hammer 42 strikes. Note that the "elastic material" referred to in this disclosure is a material that has elasticity, such as a rubber material or a resin material. "Elasticity" here refers to the property of being deformed when a load is applied, but returning to its original shape when the load is released.

[0070] As shown in FIG. 2 , the elastic member 9 of this embodiment includes a first elastic member 91 and a second elastic member 92. The first elastic member 91 and the second elastic member 92 are annular. The first elastic member 91 is provided at the front end of the drive shaft 41. The first elastic member 91 is sandwiched between the front surface of the drive shaft 41 and the rear surfaces of the pair of anvil claws 442 of the anvil 44 in the front-rear direction. On the other hand, the second elastic member 92 is provided at the rear end of the drive shaft 41. The second elastic member 92 is sandwiched between the rear surface of the drive shaft 41 and the front surface of the protrusion 524 of the second side wall 523 of the second holder 52 in the front-rear direction.

[0071] (3) Effects In the impact tool 1 according to this embodiment, each of the two cam grooves X1 has a first portion X11, a second portion X12, and a third portion X13, as shown in FIG. 5 . The first portion X11 is formed along the rotational direction D1 and has a first end E1 and a second end E2 in the rotational direction D1. The second portion X12 extends from the first end E1 and is inclined relative to the first portion X11. Similarly, the third portion X13 extends from the second end E2 and is inclined relative to the first portion X11. Each of the two steel members 45 moves through the first portion X11 of the cam groove X1 when the hammer 42 strikes the anvil 44, and moves through the second portion X12 or third portion X13 of the cam groove X1 before or after the hammer 42 strikes the anvil 44. As a result, the steel member 45 moves along the rotational direction D1 when the hammer 42 strikes the anvil 44. Because the hammer 42 moves in the same direction as the steel member 45, in the impact tool 1 of this embodiment, the hammer 42 moves along the rotation direction D1 when striking the anvil 44. That is, the hammer 42 strikes the anvil 44 along the rotation direction D1. In short, the hammer 42 can suppress the component force in the axial direction D2 of the drive shaft 41 that is applied to the anvil 44. As a result, the impact tool 1 of this embodiment has the advantage of being able to reduce vibrations that are generated in the fastening component when the hammer 42 strikes.

[0072] In the impact tool 1 according to this embodiment, each of the two cam grooves X1 has a modified trapezoidal shape. This can suppress changes in acceleration when each of the two steel members 45 moves through the cam groove X1. In other words, it can suppress changes in acceleration when the hammer 42 moves. This provides the impact tool 1 according to this embodiment with the advantage of being able to further reduce vibrations that are generated in the fastening components when the hammer 42 strikes them.

[0073] In the impact tool 1 according to this embodiment, each of the two steel members 45 has a spherical shape. Since the steel members 45 can easily move in the cam groove, the hammer 42 can easily move in the axial direction D2 (front-rear direction) and rotate in the rotational direction D1. This has the advantage that the hammer 42 can efficiently apply a striking force to the anvil 44 in the rotational direction D1.

[0074] In the impact tool 1 according to this embodiment, the elastic member 9 is made of an elastic material and is provided at least at one end in the axial direction D2 (front-rear direction) of the drive shaft 41. This has the advantage of further reducing vibrations that are generated in the fastening component when the hammer 42 strikes.

[0075] (4) Variations The above-described embodiment is merely one of various embodiments of the present disclosure. The above-described embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. The following modified examples may be realized in appropriate combination.

[0076] In the above-described embodiment, the impact tool 1 includes two cam grooves X1, but may include three or more cam grooves X1. Also, the impact tool 1 may include only one cam groove X1. That is, the number of cam grooves X1 is not limited.

[0077] In the above-described embodiment, the portion where the first portion X11 and the second portion X12 are connected and the portion where the first portion X11 and the third portion X13 are connected in each of the two cam grooves X1 are not bent but are smoothly curved. However, the portion where the first portion X11 and the second portion X12 are connected and the portion where the first portion X11 and the third portion X13 are connected may be bent.

[0078] In the above embodiment, each of the two cam grooves X1 is line-symmetric with respect to the center line of the rotational direction D1, but this does not have to be the case. That is, the longitudinal dimension of the second portion X12 and the longitudinal dimension of the third portion X13 in each of the two cam grooves X1 may be different.

[0079] In the above-described embodiment, each of the two steel members 45 is spherical, but may be ellipsoidal or cylindrical.

[0080] (summary) The impact tool (1) of the first embodiment includes a drive shaft (41), a hammer (42), an anvil (44), and a steel member (45). The drive shaft (41) has a first groove (412) formed in its outer circumferential surface (411) and is rotated in a rotational direction (D1) by a motor (3). The hammer (42) has a second groove (422) formed in its inner circumferential surface (421) and is fitted to the outer circumferential surface (411) of the drive shaft (41). The anvil (44) is struck in the rotational direction (D1) by the hammer (42). The steel member (45) is movably housed in a cam groove (X1) formed by the first groove (412) and the second groove (422). The hammer (42) is movable in the axial direction (D2) of the drive shaft (41) and rotatable in the rotation direction (D1) as a result of the steel member (45) moving along the cam groove (X1). The cam groove (X1) has a first portion (X11), a second portion (X12), and a third portion (X13). The first portion (X11) is formed along the rotation direction (D1) and has a first end (E1) and a second end (E2) in the rotation direction (D1). The second portion (X12) extends from the first end (E1) and is inclined relative to the first portion (X11). The third portion (X13) extends from the second end (E2) and is inclined relative to the first portion (X11). The steel member (45) moves through the first portion (X11) of the cam groove (X1) when the hammer (42) strikes the anvil (44), and moves through the second portion (X12) or the third portion (X13) of the cam groove (X1) before or after the hammer (42) strikes the anvil (44).

[0081] This embodiment has the advantage of reducing vibrations that occur in the fastening components when the hammer (42) strikes them.

[0082] In the impact tool (1) of the second embodiment, the cam groove (X1) in the first embodiment has a modified trapezoidal shape.

[0083] This embodiment has the advantage of being able to further reduce vibrations that occur in the fastening components when the hammer (42) strikes them.

[0084] In the impact tool (1) of the third embodiment, the steel member (45) in the first or second embodiment is spherical.

[0085] This embodiment has the advantage that the hammer (42) can efficiently apply a striking force to the anvil (44) in the rotational direction (D1).

[0086] The impact tool (1) of the fourth aspect is any one of the first to third aspects, and further includes an elastic member (9) made of an elastic material and provided at at least one end of the drive shaft (41) in the axial direction (D2).

[0087] This embodiment has the advantage of being able to further reduce vibrations that occur in the fastening components when the hammer (42) strikes them. [Explanation of symbols]

[0088] 1 impact tool 3 motors 9 Elastic member 41 Drive shaft 411 Outer surface 412 Groove (first groove) 42 Hammer 421 Inner surface 422 Groove (Second Groove) 44 Anvil 45 Steel parts D1 Rotation direction D2 Axial direction E1 1st end E2 2nd end X1 Cam groove X11 Part 1 X12 2nd part X13 3rd part

Claims

1. a drive shaft having a first groove formed on its outer peripheral surface and rotated in a rotational direction by a motor; a hammer having a second groove formed on an inner peripheral surface thereof and fitted to the outer peripheral surface of the drive shaft; an anvil to which the hammer applies a strike in the rotational direction; a steel member movably accommodated in a cam groove formed by the first groove portion and the second groove portion, the hammer is movable in the axial direction of the drive shaft and rotatable in the rotation direction by the steel member moving along the cam groove, The cam groove is a first portion formed along the rotation direction and having a first end and a second end in the rotation direction; a second portion extending from the first end and angled relative to the first portion; a third portion extending from the second end and angled relative to the first portion; The steel member is When the hammer strikes the anvil, the first portion of the cam groove moves; The hammer moves the second portion or the third portion of the cam groove before or after striking the anvil. Impact tool.

2. The cam groove has a modified trapezoidal shape. The impact tool according to claim 1 .

3. The steel member is spherical in shape. The impact tool according to claim 1 .

4. The drive shaft further includes an elastic member formed of an elastic material and provided at least at one end in the axial direction. The impact tool according to claim 1 .

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