Power tool

Abstract

The present application provides a kind of electric tool.The hammer drill has: motor;Drive side sleeve (40), it can be rotated together in positive direction or reverse direction under the driving of motor;And driven side sleeve (60), it is arranged with drive side sleeve in axial direction, by the load increase on driven side sleeve, driven side sleeve is moved to the direction of away from drive side sleeve, thus the engagement of engaging surface (44A,44B) and engaging surface (66A,66B) of cam tooth (43,65) each other is released, to form torque limiter (72).Moreover, the lead angle (alpha, beta) of the cam tooth of drive side sleeve and driven side sleeve is different in the way of engaging surface (44A,44B) and engaging surface (66A,66B) is engaged in positive rotation side and reverse side, and the transmission torque transmitted from drive side sleeve to driven side sleeve is equal in positive rotation and reverse rotation.According to the present application, the cam tooth of torque limiter can not be easily produced to collapse.

Description

TECHNICAL FIELD

[0001] The present application relates to an electric power tool such as a hammer drill. BACKGROUND

[0002] An electric power tool such as a hammer drill has a torque transmission mechanism including a driving side member that rotates under the drive of a motor and a driven side member that transmits torque from the driving side member. In particular in the torque transmission mechanism, it is known to provide a torque limiter that cuts off the transmission of torque from the driving side member when an excessive load is applied to the driven side member that is the output side. For example, in Patent Literature 1, there is disclosed a hammer drill that provides a gear on a tool holder that holds a bit and an intermediate shaft that is parallel to the tool holder, respectively, so that the rotation of the intermediate shaft can be transmitted to the tool holder via the gears. The gear on the tool holder side (driving side member) here is attached to the tool holder in a manner that it can rotate relative to the tool holder, and engages with a flange (driven side member) that is fixed to the tool holder by interlocking cam teeth. The gear is urged against the flange by a coil spring to form a torque limiter that transmits torque to the flange. Therefore, when an excessive load is applied to the tool holder, the gear moves to the side away from the flange against the urging force of the coil spring, so that the cam teeth disengage from each other, cutting off the transmission of torque.

[0003] [Patent Literature]

[0004] [Patent Literature]

[0005] Patent Literature 1: Japanese Patent No. 5456555 SUMMARY

[0006] [Problems to be Solved by the Invention]

[0007] In the torque limiter of Patent Literature 1, the smaller the amount of backlash of the cam teeth from each other, the more the rotation wobble at the time of operation is suppressed. However, when the amount of backlash is small, it is easy to collide with the next cam tooth before the cam teeth return to the original engaged state at the time of operation of the torque limiter. Therefore, it is possible that a collapse (deformation) occurs on the cam tooth.

[0008] Therefore, an object of the present application is to provide an electric power tool in which a collapse is less likely to occur on the cam tooth of a torque limiter.

[0009] [Means for Solving the Problems]

[0010] To achieve the above object, the present application is an electric power tool having: a motor; a driving side member rotatable in a positive direction or a reverse direction together under driving of the motor; and a driven side member disposed opposite to the driving side member in an axial direction,

[0011] On facing surfaces of the driving side member and the driven side member facing each other, a plurality of cam teeth each having an engagement surface inclined at a prescribed lead angle are provided on concentric circles, and torque is transmitted by engagement of the engagement surfaces of the cam teeth with each other in a rotational direction,

[0012] The members of either one of the driving side member and the driven side member are disposed so as to be movable in the axial direction with respect to the members of the other one, and are urged by an elastic member toward the members of the other one, and the members of one are moved in a direction away from the members of the other one by an increase in load on the driven side member, whereby the engagement of the engagement surfaces of the cam teeth with each other is released, thereby forming a torque limiter,

[0013] The electric power tool is characterized in that,

[0014] The cam teeth of the driving side member and the driven side member are formed so that the lead angles of the engagement surfaces are different between the positive rotation side and the reverse rotation side, and the transmitted torque from the driving side member to the driven side member is equal between the positive rotation and the reverse rotation.

[0015] According to the present application, since the lead angles of the engagement surfaces of the cam teeth are made different, the cam teeth do not easily collide with each other when the torque limiter operates. Even if the cam teeth collide with each other, the impact can be mitigated. Therefore, the cam teeth do not easily collapse. Further, even if the lead angles are made different between the positive rotation and the reverse rotation, the transmitted torque is equal, and therefore the rotation transmission on the torque limiter does not differ. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a partial central longitudinal sectional view of the hammer drill.

[0017] Figure 2 is a perspective view of the driving mechanism portion with the outer housing omitted.

[0018] Figure 3 is an A-A sectional view of Figure 1

[0019] Figure 4 is a B-B sectional view of Figure 3

[0020] Figure 5 is a C-C sectional view of Figure 3

[0021] ​​​Fig. 6 is an explanatory view of a torque limiter in which a drive-side cam portion and a driven-side cam portion are partially expanded.

[0022] Fig. 7 is an explanatory view of a torque limiter in which a drive-side cam portion and a driven-side cam portion are partially expanded.

[0023] [Reference numeral explanation]

[0024] 1: hammer drill; 2: housing; 3: outer housing; 4: motor housing; 5: motor; 6: output shaft; 8: front cylinder portion; 9: rear cylinder portion; 10: tool holder; 15: drive mechanism; 16: rotation / impact action portion; 17: rotation / impact switching portion; 18: piston cylinder; 19: hammer; 22: gear; 25: inner housing; 31: 1st intermediate shaft; 32: 2nd intermediate shaft; 35: bearing sleeve; 38: 1st gear; 40: drive-side sleeve; 41A, 41B: washer; 42: drive-side cam portion; 43, 65: cam tooth; 44A, 44B, 66A, 66B: engagement surface; 45, 67: facing surface; 46: avoidance portion; 51: 1st clutch; 54: inner groove; 660: driven-side sleeve; 61: outer groove; 63: pin; 64: driven-side cam portion; 70: 2nd gear; 71: coil spring; 72: torque limiter; 83: flange sleeve; 88: 2nd clutch; 90: mode switching mechanism; 92: switching knob; B: bit. DETAILED DESCRIPTION

[0025] In one embodiment of the present application, it can be that the lead angle of each cam tooth is formed so that the engagement surface on the forward rotation side is smaller than the engagement surface on the reverse rotation side, and the reverse rotation side engagement surface of the cam tooth of the other component is formed so that the lift amount toward the one component side is smaller than the forward rotation side engagement surface. According to this structure, collision of the cam teeth with each other at the time of forward rotation can be effectively avoided. In addition, even if the lift amount of the engagement surface is reduced, it is possible to easily make the transmitted torque equal at the time of forward rotation and reverse rotation.

[0026] In one embodiment of the present application, it can be that there is a final output shaft for mounting a bit, a rotation action of the final output shaft and / or an impact action of the bit can be performed, and a torque limiter is provided to a rotation shaft that is disposed at a stage preceding the final output shaft for transmitting the torque of a motor to the final output shaft. According to this structure, the torque limiter in the drilling mode and the hammer drill mode of the hammer drill can be easily applied.

[0027] In one embodiment of the present application, it can be that there is a rotation shaft for transmitting rotation to a final output shaft and a rotation shaft for an impact action of a bit, and the rotation shaft provided with a torque limiter is the rotation shaft for transmitting rotation. According to this structure, the torque limiter can be easily formed using the rotation shaft for rotation transmission.

[0028] In one embodiment of the present application, the cam teeth of the other member can be inclined toward the direction away from the one member as the rotation direction shifts from the forward direction to the reverse direction, via the facing surface facing the one member, whereby the lift amount toward the one member side decreases. According to this structure, the cam teeth further up the facing surface can be smoothly guided between the cam teeth, and thus collision with the next cam tooth can be effectively avoided.

[0029] In one embodiment of the present application, the inclination of the facing surface can be formed from the center of the rotation direction. According to this structure, even if a retreat portion formed by the inclination is provided, the strength of the cam teeth can be ensured.

[0030] In one embodiment of the present application, the driving-side member and the driven-side member can be sleeve-shaped outer members of the rotation shaft, and a lubricating grease accumulation portion can be recessed in at least one of the inner circumferential surface of the one member and the outer circumferential surface of the rotation shaft. According to this structure, the operation torque by which the one member moves forward and backward by the torque limiter can be stabilized.

[0031] In one embodiment of the present application, the lubricating grease accumulation portion can be a ring-shaped groove formed in the outer circumferential surface of the rotation shaft. According to this structure, the lubricating grease accumulation portion that can appropriately hold the lubricating grease can be easily formed.

[0032] In one embodiment of the present application, a receiving member that receives the other member pushed by the one member in the axial direction can be integrally outer members of the rotation shaft in the rotation direction, and a plurality of washers can be sandwiched in the axial direction between the other member and the receiving member. According to this structure, the generation of frictional heat between the other member and the receiving member can be suppressed. In addition, the lubricating grease can be appropriately held on the sliding surface between the other member and the rotation shaft.

[0033] [Embodiment]

[0034] Hereinafter, an embodiment of the present application will be described with reference to the drawings.

[0035] Figure 1 is a partial central longitudinal sectional view of a hammer drill that is an example of an electric power tool. The hammer drill 1 has a housing 2 that forms an outer contour. The housing 2 has an outer housing 3 on the front side, a motor housing 4 on the rear side thereof, and a handle housing, not shown, on the rear side thereof.

[0036] The motor housing 4 is connected to the outer housing 3 from the front side by four screws at the corners in the front view. A motor 5 is housed in the motor housing 4 in a posture in which an output shaft 6 faces the front. The output shaft 6 protrudes into the outer housing 3, and a pinion 7 is formed at the tip end.

[0037] A not-shown switch that protrudes the trigger forward is housed in the handle case. A not-shown forward / reverse switching knob for switching the rotation direction of the output shaft 6 is provided on the handle case.

[0038] The outer case 3 has a front cylinder portion 8 and a rear cylinder portion 9. The front cylinder portion 8 is a cylindrical shape with a circular cross section that extends forward. The rear cylinder portion 9 is a cylindrical shape with a larger diameter than the front cylinder portion 8. The front cylinder portion 8 is arranged at an eccentric position on the upper side of the rear cylinder portion 9.

[0039] A cylindrical tool holder 10 is coaxially housed in the front cylinder portion 8. The front end of the tool holder 10 protrudes forward from the front cylinder portion 8. A bearing 11 that supports the front portion of the tool holder 10 is held at the front end of the front cylinder portion 8. An oil seal 12 that seals between the front cylinder portion 8 and the tool holder 10 is provided forward of the bearing 11. An operation sleeve 13 is provided at the front end of the tool holder 10 that protrudes from the front cylinder portion 8. The operation sleeve 13 is provided for the purpose of performing a drill bit B attachment / detachment operation at the front end of the tool holder 10.

[0040] A drive mechanism 15 is provided in the outer case 3. The drive mechanism 15 has a rotation / impact action portion 16 and a rotation / impact switching portion 17 below it.

[0041] The rotation / impact action portion 16 has the tool holder 10, a piston cylinder 18, a ram 19, and an impact rod 20. The piston cylinder 18 is open at the front end and is housed in the rear portion of the tool holder 10 in a manner that allows it to move forward and backward. The ram 19 is housed in the piston cylinder 18 in a manner that allows it to move forward and backward via an air chamber 21. The impact rod 20 is housed in front of the ram 19 in a manner that allows it to move forward and backward in the tool holder 10. The rear portion of the tool holder 10 protrudes into the rear cylinder portion 9. A gear 22 is provided in the rear cylinder portion 9 and on the outer periphery of the tool holder 10.

[0042] An inner case 25 is housed in the rear cylinder portion 9. As Figure 2 shown, the inner case 25 includes a front plate portion 26, an intermediate portion 27, and a rear plate portion 28. The tool holder 10 penetrates the front plate portion 26 and the front plate portion 26 is held in the rear cylinder portion 9. The intermediate portion 27 supports the rear portion of the tool holder 10 via a bearing bush 29. The rear plate portion 28 has an O-ring 30 on the outer peripheral surface to seal between it and the rear cylinder portion 9. The rear plate portion 28 supports the output shaft 6.

[0043] The inner case 25 supports the rotation / impact switching portion 17. As Figure 3 shown, the rotation / impact switching portion 17 has a left and right pair of a first intermediate shaft 31 and a second intermediate shaft 32 on the lower side of the tool holder 10. The first intermediate shaft 31 and the second intermediate shaft 32 are arranged parallel to each other and parallel to the tool holder 10.

[0044] As shown in Figure 4 and Figure 5 The rear end of the first intermediate shaft 31 on the left is rotatably supported to the rear plate portion 28 of the inner housing 25 via a bearing 33. The front end of the first intermediate shaft 31 is rotatably supported to the front plate portion 26 of the inner housing 25 via a bearing 34. A receiving sleeve 35 is integrally attached to the rear portion of the first intermediate shaft 31 by press fitting. The front end of the receiving sleeve 35 has a flange 36. A washer 37 is interposed between the receiving sleeve 35 and the bearing 33.

[0045] The first gear 38 is attached to the receiving sleeve 35. The first gear 38 is engaged with the pinion gear 7 of the output shaft 6, and is rotatable independently of the receiving sleeve 35. A gear-side engaging portion 39 composed of a plurality of teeth extending in the front-rear direction is provided to the front portion of the first gear 38.

[0046] On the front side of the receiving sleeve 35, a drive-side sleeve 40 is attached to the first intermediate shaft 31. The drive-side sleeve 40 is configured to be rotatable independently of the first intermediate shaft 31 and movable in the axial direction. Between the receiving sleeve 35 and the drive-side sleeve 40, two washers 41A, 41B are attached to the first intermediate shaft 31 so as to overlap in the axial direction. The front washer 41A abuts against the rear end of the drive-side sleeve 40. The rear washer 41B abuts against the flange 36 of the receiving sleeve 35.

[0047] A drive-side cam portion 42 is provided to the front portion of the drive-side sleeve 40. The drive-side cam portion 42 is annular, and has three cam teeth 43, 43... arranged on concentric circles on the front surface thereof and projecting in the forward direction.

[0048] Figure 6A is a partial expanded view of the drive-side cam portion 42. The cam teeth 43 have engagement surfaces 44A, 44B on the front and rear in the circumferential direction, and are formed in a trapezoidal shape in cross section extending in the radial direction of the drive-side cam portion 42. The engagement surface 44A is the positive rotation (left rotation in the forward direction) side, and the engagement surface 44B is the reverse rotation side. However, in the cam teeth 43, an opposing surface 45 facing the driven-side sleeve 60 described later is an inclined surface inclined so as to gradually lower as it approaches the reverse rotation side from the center in the circumferential direction. Therefore, a notch-shaped avoidance portion 46 is formed on the engagement surface 44B side of the opposing surface 45. Accordingly, the lift amount (amount of standing up to the driven-side sleeve 60 side) of the engagement surfaces 44A, 44B becomes smaller on the engagement surface 44B side than on the engagement surface 44A side.

[0049] In addition, the lead angle (angle with respect to a plane orthogonal to the axis of the drive-side cam portion 42) a of the engagement surface 44A is smaller than the lead angle β of the engagement surface 44B.

[0050] A first spline portion 50 is formed on the outer periphery of the drive side sleeve 40 on the rear side of the drive side cam portion 42.

[0051] A first clutch 51 is spline-coupled to the first spline portion 50. The first clutch 51 is configured to be able to rotate integrally with the drive side sleeve 40 and to be able to move in the front-rear direction. The first clutch 51 has a front engagement portion 52 composed of a plurality of claws. The first clutch 51 has a rear engagement portion 53 extending in the front-rear direction and composed of a plurality of teeth. The first clutch 51 has its rear engagement portion 53 able to engage with the gear side engagement portion 39 of the first gear 38 in a rearward position. Thus, rotation of the first gear 38 is transmitted to the drive side sleeve 40 via the first clutch 51.

[0052] An annular inner groove 54 is formed on the outer peripheral surface of the first intermediate shaft 31 on the front side of the drive side sleeve 40. Three inner fitting grooves 55, 55,... are formed on the outer peripheral surface of the first intermediate shaft 31 at the positions of the inner groove 54. The inner fitting grooves 55 extend in the front-rear direction crossing the inner groove 54 and are formed at equal intervals in the circumferential direction of the first intermediate shaft 31.

[0053] A driven side sleeve 60 is fitted to the first intermediate shaft 31 at the positions of the inner groove 54 and the inner fitting grooves 55. An annular outer groove 61 is formed on the inner peripheral surface of the driven side sleeve 60. The outer groove 61 has substantially the same front-rear width as the inner groove 54 of the first intermediate shaft 31. Three outer fitting grooves 62, 62,... are formed on the inner peripheral surface of the driven side sleeve 60. The outer fitting grooves 62 extend in the front-rear direction crossing the outer groove 61 and are formed at equal intervals in the circumferential direction of the driven side sleeve 60. The outer fitting grooves 62 are formed over the entire length of the driven side sleeve 60.

[0054] Three pins 63, 63,... are fitted between the inner fitting grooves 55 of the first intermediate shaft 31 and the outer fitting grooves 62 of the driven side sleeve 60, straddling both. The driven side sleeve 60 is linked to the first intermediate shaft 31 by the pins 63 in a manner that is integral in the rotational direction and separable in the front-rear direction.

[0055] A driven side cam portion 64 is provided on the rear portion of the driven side sleeve 60. The driven side cam portion 64 is annular and has three cam teeth 65, 65,... on its rear surface, which are disposed on concentric circles and project rearward.

[0056] As Figure 6AAs shown, the cam teeth 65 also have engagement surfaces 66A, 66B on the front and back in the circumferential direction and are formed in a trapezoidal shape in a cross section extending in the radial direction of the driven-side cam portion 64. The engagement surface 66A is the positive rotation side, and the engagement surface 66B is the reverse rotation side. However, in the cam teeth 65, the facing surface 67 facing the driving-side sleeve 40 is flat. The lead angles a, β of the engagement surfaces 66A, 66B are formed at the same angles as the lead angles a, β of the engagement surfaces 44A, 44B of the driving-side cam portion 42 of the driving-side sleeve 40. That is, the lead angle a of the engagement surface 66A is smaller than the lead angle β of the engagement surface 66B.

[0057] The second gear 70 is formed on the front of the first intermediate shaft 31. The second gear 70 engages with the gear 22 of the tool holder 10. Between the driven-side sleeve 60 and the second gear 70, a coil spring 71 is externally fitted on the first intermediate shaft 31. The driven-side sleeve 60 is urged to the retracted position by the coil spring 71. In the retracted position, the driven-side cam portion 64 abuts against the driving-side cam portion 42, and the cam teeth 43, 65 are engaged with each other in the rotational direction. That is, the driving-side cam portion 42 and the driven-side cam portion 64 form a torque limiter 72 that is engaged in the rotational direction by the applied force of the coil spring 71.

[0058] Therefore, in the retracted position of the first clutch 51, the rotation of the first gear 38 is transmitted to the driving-side sleeve 40 via the first clutch 51. The rotation of the driving-side sleeve 40 is transmitted to the driven-side sleeve 60 by the engagement of the driving-side cam portion 42 and the driven-side cam portion 64. The rotation of the driven-side sleeve 60 is transmitted to the first intermediate shaft 31 by the pin 63. Therefore, the second gear 70 rotates and rotates the tool holder 10 via the gear 22.

[0059] In the retracted position of the driven-side sleeve 60, the outer groove 61 of the driven-side sleeve 60 overlaps the inner groove 54 of the first intermediate shaft 31 in the radial direction. Therefore, the two grooves 61, 54 become a lubricating grease storage portion.

[0060] In this torque limiter 72, when the drill bit B is accidentally locked or the like, a load exceeding the applied force of the coil spring 71 is applied to the driven-side sleeve 60 from the tool holder 10 side. Then, in the case of positive rotation, as shown in FIG. 8, the driven-side cam portion 64 (the driven-side sleeve 60) advances between the driving-side cam portion 42 by the guidance of the engagement surfaces 44A, 66A of the cam teeth 43, 65 to each other, whereby the cam teeth 65 ride over the cam teeth 43. Since the driving-side cam portion 42 (the driving-side sleeve 40) continues to rotate in this state, as shown in FIG. 9, the cam teeth 65 move relatively in the circumferential direction on the facing surface 45 of the cam teeth 43. Then, when the cam teeth 65 reach the relief 46, as shown in FIG. 10, the cam teeth 65 are disengaged from the cam teeth 43. Figure 6B Figure 6C Figure 7A Figure 7B ​​​As shown, the cam tooth 65 moves circumferentially relative to the avoidance part 46 while being forced backward by the helical spring 71. Therefore, the cam tooth 65 relatively passes over the cam tooth 43, as... Figure 7C As shown, it engages again with the next cam tooth 43 adjacent in the circumferential direction. At this time, since the cam tooth 65 retracts along the avoidance part 46, the cam tooth 65 is able to engage with the next cam tooth 43 without colliding with it, and engage with it again between the cam teeth 43, 43.

[0061] As the cam teeth 43 and 65 repeatedly pass over and re-engage with each other, the drive sleeve 40 idles relative to the driven sleeve 60. Therefore, the rotational transmission to the driven sleeve 60 and the first intermediate shaft 31 is cut off.

[0062] On the other hand, when the first clutch 51 moves to the first forward position, it disengages from the first gear 38. Therefore, the rotation of the first gear 38 is no longer transmitted to the drive-side sleeve 40. Consequently, torque is no longer transmitted to the driven-side sleeve 60 and the first intermediate shaft 31, which are engaged with the drive-side sleeve 40.

[0063] A lock plate 75 is provided on the lower left side of the first intermediate shaft 31. The lock plate 75 has a locking pawl 76 facing rearward. A coil spring 77 is provided on the front side of the lock plate 75. When the first clutch 51 advances to a second forward position, which is further forward than the first forward position, the locking pawl 76 engages with the front engagement portion 52 of the first clutch 51. Therefore, the rotation of the first clutch 51 and the drive-side sleeve 40 is locked. Thus, the rotation of the first intermediate shaft 31 and the tool holder 10 is locked by the driven-side sleeve 60 engaging with the drive-side sleeve 40.

[0064] like Figure 5 As shown, the rear end of the second intermediate shaft 32 on the right is rotatably supported on the rear plate portion 28 of the inner housing 25 via a bearing 80. The front end of the second intermediate shaft 32 is rotatably supported on the front plate portion 26 via a bearing 81. At the rear of the second intermediate shaft 32, a third gear 82 that meshes with the pinion 7 of the output shaft 6 is integrally fixed. In front of the third gear 82, a flange sleeve 83 is externally mounted to the second intermediate shaft 32 in a separate and rotatable manner. A swash bearing 84 with an inclined axis is provided on the flange sleeve 83. An arm 85 is provided protruding upward on the outer ring of the swash bearing 84. The top end of the arm 85 is connected to the rear end of the piston cylinder 18. On the inner circumference of the flange sleeve 83, a flange side engaging sleeve 86 extending in the front-rear direction and having multiple teeth is integrally joined.

[0065] A second spline portion 87 is formed on the second intermediate shaft 32 in front of the flange sleeve 83. A second clutch 88 is splined onto the second spline portion 87. The second clutch 88 is configured to rotate integrally with the second intermediate shaft 32 and move back and forth, and has a clutch-side engagement portion 89 extending in the back-forward direction and composed of multiple teeth at its rear. In the retracted position, the clutch-side engagement portion 89 of the second clutch 88 engages with the flange-side engagement sleeve 86 of the flange sleeve 83. Therefore, the rotation of the second intermediate shaft 32 is transmitted to the flange sleeve 83 via the second clutch 88. When the second clutch 88 moves forward, the clutch-side engagement portion 89 disengages from the flange-side engagement sleeve 86, and the rotation of the second intermediate shaft 32 is no longer transmitted to the flange sleeve 83.

[0066] like Figures 1-4 As shown, a mode switching mechanism 90 is provided below the first intermediate shaft 31 and the second intermediate shaft 32. The mode switching mechanism 90 has a lever 91 and a switching knob 92.

[0067] Rod 91 is arranged parallel to the first intermediate shaft 31 and the second intermediate shaft 32. The rear end of rod 91 is supported by the rear plate portion 28, and the front end is supported by the rear cylinder portion 9. Rod 91 has two movable plates, a first plate 93 and a second plate 94. The first plate 93 is penetrated by rod 91 at the rear end. The second plate 94 is penetrated by rod 91 at the front end. The front end of the first plate 93 engages with the outer periphery of the first clutch 51. The front end of the second plate 94 engages with the outer periphery of the second clutch 88. A first coil spring 95 is externally mounted on rod 91 on the front side of the first plate 93. A second coil spring 96 is externally mounted on rod 91 on the front side of the second plate 94. The first coil spring 95 applies force to the first plate 93 towards a retracted position where it abuts against the front surface of the rear plate portion 28. This retracted position is the retracted position of the first clutch 51, which retracts together with the first plate 93. The second coil spring 96 applies force to the second plate 94 in a retracted position abutting against the second eccentric pin 98 (described later). This retracted position is the retracted position of the second clutch 88, which retracts together with the second plate 94.

[0068] The positions of the first plate 93 and the second plate 94 can be changed by switching knob 92. Switching knob 92 is configured to rotate towards the lower surface of the rear cylinder 9. Two eccentric pins, a first eccentric pin 97 and a second eccentric pin 98, protrude into the rear cylinder 9 from the switching knob 92. The first eccentric pin 97 engages with the first plate 93 from the rear, and the second eccentric pin 98 engages with the second plate 94 from the rear.

[0069] Therefore, by the rotational operation of the switching knob 92, the forward and backward positions of the first plate 93 and the second plate 94 (the first clutch 51 and the second clutch 88) are switched by the first eccentric pin 97 and the second eccentric pin 98. That is, the operation mode can be switched to the drilling mode, the hammer drill mode, the hammering mode (rotation lock), and the hammering mode (neutral).

[0070] In the drilling mode, the first clutch 51 is located at the retreat position, and the second clutch 88 is located at the advance position. Therefore, the rotation of the first gear 38 becomes a state of being transmitted to the tool holder 10. On the other hand, the rotation of the third gear 82 and the second intermediate shaft 32 becomes a state of not being transmitted to the flange sleeve 83. Therefore, when the drive motor 5 rotates the output shaft 6, the drill bit B and the tool holder 10 rotate together.

[0071] In the hammer drill mode, the first clutch 51 and the second clutch 88 are both located at the retreat position. Therefore, the rotation of the first gear 38 becomes a state of being transmitted to the tool holder 10. On the other hand, the rotation of the third gear 82 and the second intermediate shaft 32 also becomes a state of being transmitted to the flange sleeve 83. Therefore, when the output shaft 6 rotates, the drill bit B rotates, and at the same time, the flange sleeve 83 rotates to swing the arm 85 forward and backward. Therefore, the piston cylinder 18 reciprocates to reciprocate the ram 19, thereby impacting the drill bit B via the impact lever 20.

[0072] In the hammering mode (rotation lock), the first clutch 51 is located at the second advance position, and the second clutch 88 is located at the retreat position. Therefore, the rotation of the first gear 38 becomes a state of not being transmitted to the tool holder 10. However, since the first clutch 51 is engaged with the lock plate 75, the rotation of the tool holder 10 is locked. On the other hand, the rotation of the third gear 82 and the second intermediate shaft 32 becomes a state of being transmitted to the flange sleeve 83. Therefore, when the output shaft 6 rotates, the drill bit B is fixed around the axis without rotating, the flange sleeve 83 rotates, and the arm 85 swings forward and backward. Therefore, only the impact action of the drill bit B is performed.

[0073] In the hammering mode (neutral), the first clutch 51 is located at the first advance position, and the second clutch 88 is located at the retreat position. Therefore, the rotation of the first gear 38 becomes a state of not being transmitted to the tool holder 10. However, since the first clutch 51 is not engaged with the lock plate 75, the rotation of the tool holder 10 becomes free. On the other hand, the rotation of the third gear 82 and the second intermediate shaft 32 becomes a state of being transmitted to the flange sleeve 83. Therefore, when the output shaft 6 rotates, the drill bit B does not rotate, the flange sleeve 83 rotates, and the arm 85 swings forward and backward. Thus, only the impact action of the drill bit B is performed.

[0074] Thus, in the torque limiter 72, when the drill 1 is operated in the drill mode or the hammer drill mode, the cam teeth 43 of the driving-side cam portion 42 of the driving-side sleeve 40 and the cam teeth 65 of the driven-side cam portion 64 of the driven-side sleeve 60 are engaged with each other to transmit the torque, regardless of the rotation direction of the motor 5. In this case, in the cam teeth 43 of the driving-side cam portion 42, the lift amount of the engagement surface 44B on the reverse rotation side is smaller than the lift amount of the engagement surface 44A on the forward rotation side by the relief portion 46, but since the lead angle β is larger than the lead angle α of the engagement surface 44A on the forward rotation side, the transmitted torque is the same in the forward rotation and the reverse rotation.

[0075] Also, in the torque limiter 72, when the drill bit B is unexpectedly locked or the like, a load exceeding the applied force of the coil spring 71 is applied to the driven-side sleeve 60 from the tool holder 10 side. Then, as described above, the driven-side sleeve 60 moves forward and backward to repeatedly engage and disengage the cam teeth 65 of the driven-side cam portion 64 with respect to the cam teeth 43 of the driving-side cam portion 42. Thus, the driving-side sleeve 40 idles to cut off the rotation transmission to the driven-side sleeve 60. At this time, the cam teeth 65 of the driven-side cam portion 64 are not collided with respect to the cam teeth 43 of the driving-side cam portion 42 to be engaged again, and thus, the collapse of the cam teeth 43 and 65 is not easily generated.

[0076] The hammer drill 1 (power tool) of the above-described type includes the motor 5, the driving-side sleeve 40 (driving-side member) that is rotatable in the positive direction or the negative direction by the driving of the motor 5, and the driven-side sleeve 60 (driven-side member) that is disposed opposite to the driving-side sleeve 40 in the axial direction. Further, on the facing surfaces of the driving-side sleeve 40 and the driven-side sleeve 60 that face each other, a plurality of cam teeth 43 and 65 having engagement surfaces 44A and 44B and 66A and 66B inclined at prescribed lead angles α and β are respectively disposed on concentric circles, and the torque is transmitted by the engagement of the engagement surfaces 44A and 44B of the cam teeth 43 and the engagement surfaces 66A and 66B of the cam teeth 65 in the rotation direction. Also, the driven-side sleeve 60 is disposed so as to be movable in the axial direction with respect to the driving-side sleeve 40, and is biased to the driving-side sleeve 40 side by the coil spring 71 (elastic member), and when the load on the driven-side sleeve 60 increases, the driven-side sleeve 60 moves in the direction away from the driving-side sleeve 40, and thereby the torque limiter 72 for releasing the engagement of the engagement surfaces 44A and 44B of the cam teeth 43 and the engagement surfaces 66A and 66B of the cam teeth 65 with each other is formed. Further, the cam teeth 43 and 65 of the driving-side sleeve 40 and the driven-side sleeve 60 are formed so that the lead angles α and β of the engagement surfaces 44A and 44B and 66A and 66B on the forward rotation side and the reverse rotation side are different, and the transmitted torque from the driving-side sleeve 40 to the driven-side sleeve 60 is the same in the forward rotation and the reverse rotation.

[0077] According to this structure, since the lead angles a, β of the engagement surfaces 44A, 44B of the cam teeth 43 and the engagement surfaces 66A, 66B of the cam teeth 65 are different, the cam teeth 43, 65 do not easily collide with each other when the torque limiter 72 operates. Even if the cam teeth 43, 65 collide with each other, the impact can be mitigated. Therefore, collapse of the cam teeth 43, 65 is not easily caused. Further, even if the lead angles a, β are made different between the forward rotation and the reverse rotation, the transmitted torque is the same, and therefore, the rotation transmission in the torque limiter 72 does not differ.

[0078] The lead angles a, β of the cam teeth 43, 65 are formed such that the engagement surface 44A, 66A on the forward rotation side is smaller than the engagement surface 44B, 66B on the reverse rotation side, and the engagement surface 44B on the reverse rotation side in the cam teeth 43 of the driving side sleeve 40 is formed such that the lift amount to the driven side sleeve 60 side is smaller than the engagement surface 44A on the forward rotation side. Therefore, the collision of the cam teeth 43, 65 with each other at the time of the forward rotation can be effectively avoided. Further, even if the lift amount of the engagement surface 44B is reduced, the transmitted torque can be easily made equal between the forward rotation and the reverse rotation.

[0079] The tool holder 10 (final output shaft) for mounting the drill bit B, whereby the rotational operation of the tool holder 10 and / or the impact operation of the drill bit B can be performed, and the torque limiter 72 are provided on the 1st intermediate shaft 31 (rotation shaft) configured at the front stage of the tool holder 10 for transmitting the torque of the motor 5 to the tool holder 10. Therefore, the torque limiter 72 in the drilling mode and the hammer drill mode in the hammer drill 1 can be easily applied.

[0080] The 1st intermediate shaft 31 (rotation shaft) for transmitting rotation to the tool holder 10 and the 2nd intermediate shaft 32 (rotation shaft) for the impact operation of the drill bit B, and the rotation shaft on which the torque limiter 72 is provided is the 1st intermediate shaft 31 for transmitting rotation. Therefore, the torque limiter 72 can be easily formed using the 1st intermediate shaft 31.

[0081] The cam teeth 43 of the driving side sleeve 40 are inclined to the direction away from the driven side sleeve 60 as the cam teeth 43 approach the reverse rotation side from the forward rotation side by the facing surface 45 facing the driven side sleeve 60, and therefore, the lift amount to the driven side sleeve 60 side is reduced. Therefore, the cam teeth 65 on the facing surface 45 can be smoothly guided between the cam teeth 43, 43, and therefore, the collision with the next cam teeth 43 can be effectively avoided.

[0082] The inclination of the facing surface 45 is formed from the center of the rotation direction. Therefore, even if the avoidance portion 46 formed by the inclination is provided, the strength of the cam teeth 43 can be ensured.

[0083] The drive-side sleeve 40 and the driven-side sleeve 60 are sleeve-shaped outer members that are fitted to the first intermediate shaft 31. An inner groove 54 and an outer groove 61, which are lubricant accumulation portions, are recessed in the inner peripheral surface of the driven-side sleeve 60 and the outer peripheral surface of the first intermediate shaft 31. Therefore, the action torque of the driven-side sleeve 60 moving forward and backward by the torque limiter 72 can be stabilized.

[0084] The lubricant accumulation portion is an annular inner groove 54 (groove) formed in the outer peripheral surface of the first intermediate shaft 31. Therefore, the lubricant accumulation portion that can appropriately hold lubricant can be easily formed.

[0085] The receiving sleeve 35 (receiving member) that receives the drive-side sleeve 40 pushed by the driven-side sleeve 60 in the axial direction is integrally fitted to the first intermediate shaft 31 in the rotational direction. Two washers 41A and 41B are sandwiched in the axial direction between the drive-side sleeve 40 and the receiving sleeve 35. Therefore, the generation of frictional heat between the drive-side sleeve 40 and the receiving sleeve 35 can be suppressed. In addition, lubricant can be appropriately held on the sliding surface between the drive-side sleeve 40 and the first intermediate shaft 31.

[0086] Next, a modification example will be described.

[0087] The avoiding portion provided to the cam tooth is not limited to an inclined plane. The avoiding portion can be formed as an inclined curved surface (including a concave curved surface and a convex curved surface), or as a concave notch.

[0088] The number of cam teeth of each of the drive-side cam portion and the driven-side cam portion can be increased or decreased.

[0089] In the above-described mode, the cam tooth provided with the avoiding portion can be provided to the drive-side cam portion, but can also be provided to the driven-side cam portion.

[0090] However, the avoiding portion is not provided to the cam tooth, and only the lead angle of the engagement surface is changed, and the collapse of the cam tooth can also be suppressed. For example, even if the lead angle of the engagement surface on the forward rotation side is made smaller than that on the reverse rotation side, the cam teeth do not easily collide with each other at the time of the torque limiter action at the time of forward rotation, and even if they collide, the impact can be suppressed.

[0091] In addition, even if the avoiding portion is not provided to the cam tooth, for example, as long as the compression amount of the coil spring of the torque limiter and the like is mechanically changed at the time of forward rotation and at the time of reverse rotation, the transmitted torque can be made equal at the time of forward rotation and at the time of reverse rotation.

[0092] The rotation stop of the driven-side sleeve is not limited to the rotation stop by the pin. Key coupling or spline coupling can also be employed.

[0093] In the above-described mode, the grease accumulation portion is formed by grooves provided on the driven-side sleeve and the first intermediate shaft, respectively, but can be formed by a groove provided on either one. The width of the groove can be changed. A plurality of grooves can be provided.

[0094] In the above-described mode, the driven-side sleeve is provided to be movable forward and backward to engage with or disengage from the driving-side sleeve, but the reverse can also be possible. That is, the driving-side sleeve can be provided to be movable forward and backward to engage with or disengage from the driven-side sleeve.

[0095] The driving-side member and the driven-side member are not limited to the sleeve shape. The elastic member can also be a coil spring or the like other than a spiral spring.

[0096] In the above-described mode, there are two intermediate shafts, and the torque limiter is provided on one of the intermediate shafts, but if the intermediate shafts are one, the torque limiter can be provided on the intermediate shaft.

[0097] In addition, the torque limiter is not limited to the case where it is provided on the intermediate shaft (rotary shaft) of the front stage of the tool holder. For example, there are cases where a gear provided on the tool holder is used as a driving-side member separate from the tool holder, and a driven-side member is provided integrally on the tool holder, and the gear is urged toward the driven-side member by a spiral spring or the like, thereby forming a torque limiter. The present application can also be applied to this torque limiter.

[0098] In addition, the orientation of the motor is not limited to the front-rear direction, and can be changed as appropriate.

[0099] The motor is not limited to a brush motor, and a brushless motor can also be used.

[0100] The power source can not be a commercial power source, but can be a battery pack.

[0101] The impact action can not be a piston cylinder, but can be a structure in which a piston reciprocates within a fixed cylinder. There can be no impact rod, but a structure in which a ram directly impacts a drill bit. There can be a structure in which a crank mechanism is provided to convert the rotation of the motor into reciprocating motion of a piston cylinder or the like.

[0102] The present application is not limited to a hammer drill, but can also be applied to other power tools such as a screwdriver or the like, as long as it is a structure having a mechanical torque limiter.

Claims

1. An electric power tool having a motor, a driving-side member, and a driven-side member, wherein the driving-side member is rotatable in a forward direction or a reverse direction by driving of the motor; the driven-side member is disposed opposite to the driving-side member in an axial direction; a plurality of cam teeth each having an engagement surface inclined at a predetermined lead angle are disposed on concentric circles on facing surfaces of the driving-side member and the driven-side member facing each other, and torque is transmitted by engagement of the engagement surfaces of the cam teeth with each other in a rotational direction; the members of either one of the driving-side member and the driven-side member are disposed so as to be movable in the axial direction with respect to the members of the other one, and are urged toward the members of the other one by an elastic member, and the members of one are moved away from the members of the other one by an increase in load on the driven-side member, whereby the engagement of the engagement surfaces of the cam teeth with each other is released, thereby forming a torque limiter; and the electric power tool is characterized in that the cam teeth of the respective driving-side member and driven-side member are formed so that the lead angles of the engagement surfaces are different between the forward direction and the reverse direction, and the transmitted torque from the driving-side member to the driven-side member is equal between the forward direction and the reverse direction.

2. The electric power tool according to claim 1, wherein the lead angle of each of the cam teeth is formed so that the engagement surface on the forward direction side is smaller than the engagement surface on the reverse direction side, and the engagement surface on the reverse direction side in the cam teeth of the members of the other one is formed so as to have a lift amount toward the members of one that is smaller than the engagement surface on the forward direction side.

3. The electric power tool according to claim 1, wherein there is a final output shaft for mounting a drill bit, and a rotational action of the final output shaft and / or an impact action of the drill bit can be performed, the torque limiter is disposed on a rotational shaft that is arranged at a stage preceding the final output shaft, and that transmits torque of the motor to the final output shaft.

4. The electric power tool according to claim 3, wherein there is a rotational shaft for transmitting rotation to the final output shaft and a rotational shaft for the impact action of the drill bit, and the rotational shaft on which the torque limiter is disposed is the rotational shaft for transmitting the rotation.

5. The electric power tool according to any one of claims 1 to 4, wherein the cam teeth of the members of the other one are inclined toward a direction away from the members of one by a facing surface facing the members of one as the forward direction side approaches the reverse direction side, whereby the lift amount toward the members of one becomes smaller.

6. The electric power tool according to claim 5, wherein the inclination of the facing surface is formed starting from the center of the rotational direction.

7. The electric power tool according to claim 3 or 4, wherein the driving-side member and the driven-side member are sleeve-shaped outer members of the rotational shaft, and a grease accumulation portion is recessed in at least one of an inner peripheral surface of the members of one and an outer peripheral surface of the rotational shaft. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 8. The electric power tool according to claim 7, characterized in that the grease accumulation portion is a ring-shaped groove formed in an outer circumferential surface of the rotating shaft.

9. The electric power tool according to claim 7, characterized in that a receiving member that receives the other member pushed by the one member in the axial direction is integrally attached to the rotating shaft in the rotational direction, and a plurality of washers are sandwiched in the axial direction between the other member and the receiving member.

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