JP2007326168A - Work tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for stabilizing an actuation torque of a torque limiter in a work tool having a torque limiter. <P>SOLUTION: The work tool 101 has a tip tool 119, a motor 111, and a drive mechanism 117. The drive mechanism 117 has a torque limiter 151 which transmits a torque of the motor to the tip tool 119 under a condition that the torque acting on the tip tool 119 is lower than a predetermined set value, and shields transmission of the torque when a torque exceeding the set value acts on the tip tool 119. An elastic member deciding the transmission torque of the torque limiter 151 is constituted of a plurality of plate springs 159 overlaid in such a manner that axial edges 159b of an elastic deformation part 159a are parallely opposed to each other. A parallel condition maintaining part 173 maintaining a parallel condition of axial edges of a plurality of the leaf springs 159 even when one of a plurality of the leaf springs 159 is relatively displaced to other leaf spring 159 in a radial direction, is provided to the overlaid part of a plurality of the leaf springs. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a work tool that performs a predetermined machining operation by rotating the tip tool around a major axis direction, and in particular, when a load exceeding a predetermined set value is applied to the tip tool, the torque applied to the tip tool The present invention relates to a work tool having a torque limiter that cuts off transmission of.

  Japanese Patent Laid-Open No. 9-57511 (Patent Document 1) discloses a hammer drill with a torque limiter. The torque limiter described in the publication has a configuration in which a torque transmission ball is interposed between a driving gear as a driving side rotating member and a driven flange as a driven side rotating member arranged on the same axis. The ball is held in a radial holding groove formed in the driven flange, and the torque of the driving gear is transmitted to the driven flange by engaging with the cam portion of the driving gear in the circumferential direction. When a torque exceeding a predetermined torque is applied between the drive gear and the driven flange by a disc spring as an elastic member, the ball resists the biasing force of the disc spring acting via the pressing plate. It moves to the inner side in the radial direction along the holding groove and climbs over the cam portion, thereby releasing the locking of the ball with respect to the cam portion of the drive gear and interrupting the transmission of torque.

Generally, a disc spring has a high spring constant. Therefore, a slight change in the compression amount becomes a large load change. In the case of the torque limiter described in the publication, the two disc springs face each other so that the outer diameter side edges come into contact with each other, and the hole is fitted and arranged on the outer periphery of the shaft portion of the driven flange. Is done. In the case of such a configuration, the two disc springs have their mating portions (contact portions) in contact with an annular line, and between the inner periphery of the disc spring hole and the outer periphery of the shaft portion of the driven flange. There is a gap that allows loose fitting. The disc spring is compressed each time the ball gets over the cam portion formed on the driven flange, that is, every time the torque limiter is actuated, but each time the disc spring is mated (abutting portion) in the radial direction. There is a possibility of slipping. When a radial displacement occurs at the mating portion between the disc springs, the stability of the disc spring contact state is impaired, and as a result, the disc spring is tilted and the axial length is changed. The generated load will change. That is, in a configuration in which a plurality of disc springs are used so as to face each other, the operating torque of the torque limiter may fluctuate, and there is still room for improvement in this respect.
Japanese Patent Laid-Open No. 9-57511

  In view of such a point, an object of the present invention is to provide a technique that contributes to stabilization of an operating torque of a torque limiter in a work tool having a torque limiter.

In order to achieve the above object, the invention described in each claim is configured.
The work tool according to the first aspect of the present invention is a tip tool that rotates around the major axis direction to perform a predetermined machining operation, a motor that rotationally drives the tip tool, and transmits torque of the motor to the tip tool. A drive mechanism. The drive mechanism transmits torque of the motor to the tip tool when the torque acting on the tip tool is lower than a predetermined set value, and shuts off torque transmission when torque exceeding the set value acts on the tip tool. Has a limiter. Typically, the “work tool” in the present invention corresponds to a drilling tool used for drilling a workpiece, but is not limited to a drilling tool, and is used for grinding or polishing a workpiece. The present invention can be suitably applied to various working tools that perform machining operations by rotating a tip tool, such as a grinding tool used, an electric wrench that performs a screw tightening operation, or an electric circular saw that performs a cutting operation.

  The torque limiter in the present invention includes a first rotating member, a second rotating member, a ball member, a pressing member, and an elastic member. The first rotating member is arranged to be rotatable around a predetermined axis. The second rotating member is disposed so as to be rotatable about the same axis as the axis of the first rotating member and so that the rotating peripheral surface faces the rotating peripheral surface of the first rotating member. The ball member is held by the first rotating member in a state where relative movement in the circumferential direction of the first rotating member is impossible, and the first rotating member is engaged with the second rotating member in the circumferential direction to perform the first rotation. Torque is transmitted between the member and the second rotating member. The pressing member is disposed so as to be movable in the axial direction of the first rotating member and is capable of contacting the ball member. The elastic member is configured to apply an urging force in the axial direction of the first rotating member to the ball member via the pressing member. The torque limiter maintains the locking of the ball member with respect to the second rotating member in a state where a torque lower than a predetermined set value is applied between the first rotating member and the second rotating member. When the torque between the first rotating member and the second rotating member is transmitted and a torque exceeding the set value acts between the first rotating member and the second rotating member, The ball member moves in the axial direction or the radial direction against the urging force of the elastic member acting via the pressing member, and the circumferential locking with respect to the second rotating member is released, whereby the first rotation Transmission of torque between the member and the second rotating member is released.

  In the present invention, as a characteristic configuration, the elastic member has a tapered cylindrical elastic deformation portion, and the axial end edge of the elastic deformation portion faces in parallel on the axis of the first rotating member. It is comprised by the some disc spring arrange | positioned in piles. In the overlapping portion of the plurality of disc springs, even if one of the plurality of disc springs is displaced relative to the other disc spring in the radial direction of the first rotating member, the axial direction of the plurality of disc springs A parallel state maintaining unit that maintains the parallel state between the edges is set. In the present invention, the “placed and arranged so as to face each other” is a mode in which the outer diameter side edges of the elastic deformation portions are close to each other and the inner diameter side edges are separated from each other, or the inner diameter of the elastic deformation portion Any of the embodiments in which the side edges are close to each other and the outer diameter side edges are opposed to each other is preferably included. The “parallel state maintaining portion” in the present invention is typically constituted by a flat flat portion extending in the radial direction and formed between the overlapping portions of a plurality of disc springs. And about this plane part, any of the aspect which disk springs contact | abut directly, or the aspect contacted indirectly via an inclusion is included suitably.

  According to the present invention, in the configuration in which a plurality of disc springs are arranged so as to be overlapped so that the axial end edges of the elastically deforming portions face each other in parallel, the parallel state maintaining unit is arranged in the overlapping portion of the plurality of disc springs. The parallel state maintaining portion maintains the parallel state between the axial ends of the plurality of disc springs regardless of the relative displacement in the radial direction between the disc springs. Accordingly, even if the overlapping portions of the disc springs are relatively displaced in the radial direction, the disc springs are prevented from being tilted due to the displacement, so that the axial lengths of the plurality of disc springs (first rotating member) The change in the axial length of the disc spring is suppressed, and the load generated by the disc spring is kept constant. For this reason, the operating torque of the torque limiter is stabilized. Specifically, the disc spring has a hole in the elastic deformation portion with a predetermined gap to allow elastic deformation of the elastic deformation portion with respect to the shaft portion of the first rotation member or the second rotation member, for example. It arrange | positions so that it may loosely fit. In other words, the plurality of disc springs are arranged such that a relative displacement in the radial direction corresponding to the gap is allowed. According to the present invention, in such a configuration, the total length of the plurality of disc springs in the axial direction of the first rotating member is made steady regardless of the relative displacement in the radial direction that occurs between the plurality of disc springs. Is possible.

(Invention of Claim 2)
According to the second aspect of the present invention, the parallel state maintaining portion in the work tool according to the first aspect is interposed between the axial end edges of the plurality of disc springs facing each other in parallel, and the axial direction thereof. It is comprised by the interposition member which has a flat plane which contacts an edge. And even if one disc spring is relatively displaced in the radial direction of the first rotating member with respect to other disc springs, the interposition member maintains the contact state with the axial end edge via the plane. It was set as the structure which maintains the parallel state of the axial direction edge of several disc springs, and makes the full length of the several disc springs in the axial direction of a 1st rotation member steady by this. The “intervening member” in the present invention typically corresponds to a washer. According to the present invention, even if a relative displacement in the radial direction occurs in the overlapped portion of the plurality of disc springs, the axial end edges of the plurality of disc springs are all over the entire circumferential direction with respect to the plane of the interposed member. The contact state is maintained. For this reason, the plurality of disc springs are not inclined due to the relative displacement in the radial direction, and the axial length of the plurality of disc springs does not change. As a result, the load generated by the disc spring is held constant, and the operating torque of the torque limiter is stabilized. Note that the parallel state maintaining portion is formed by, for example, processing the outer diameter side edge or the inner diameter side edge that directly contacts when a plurality of disc springs are stacked, thereby processing the outer diameter side edge or the inner diameter side edge. This can also be realized by providing a flat portion in the edge in the radial direction. However, a configuration in which an interposition member such as a washer, which is a commercially available machine part, is interposed as in the present invention has a flat portion on the disc spring. Cost can be reduced compared with the case of performing planar processing for forming.

(Invention of Claim 3)
According to a third aspect of the present invention, there is provided a work tool that rotates around a major axis direction to perform a predetermined machining operation, a motor that rotates the tip tool, and transmits torque of the motor to the tip tool. A drive mechanism. The drive mechanism transmits torque of the motor to the tip tool when the torque acting on the tip tool is lower than a predetermined set value, and shuts off torque transmission when torque exceeding the set value acts on the tip tool. Has a limiter. Typically, the “work tool” in the present invention corresponds to a drilling tool used for drilling a workpiece, but is not limited to a drilling tool, and is used for grinding or polishing a workpiece. The present invention can be suitably applied to various working tools that perform machining operations by rotating a tip tool, such as a grinding tool used, an electric wrench that performs a screw tightening operation, or an electric circular saw that performs a cutting operation.

  The torque limiter in the present invention includes a first rotating member, a second rotating member, a ball member, a pressing member, and an elastic member. The first rotating member is arranged to be rotatable around a predetermined axis. The second rotating member is disposed so as to be rotatable about the same axis as the axis of the first rotating member and so that the rotating peripheral surface faces the rotating peripheral surface of the first rotating member. The ball member is held by the first rotating member in a state where relative movement in the circumferential direction of the first rotating member is impossible, and the first rotating member is engaged with the second rotating member in the circumferential direction to perform the first rotation. Torque is transmitted between the member and the second rotating member. The pressing member is disposed so as to be movable in the axial direction of the first rotating member and is capable of contacting the ball member. The elastic member is configured to apply an urging force in the axial direction of the first rotating member to the ball member via the pressing member. The torque limiter maintains the locking of the ball member with respect to the second rotating member in a state where a torque lower than a predetermined set value is applied between the first rotating member and the second rotating member. When the torque between the first rotating member and the second rotating member is transmitted and a torque exceeding the set value acts between the first rotating member and the second rotating member, The ball member moves in the axial direction or the radial direction against the urging force of the elastic member acting via the pressing member, and the circumferential locking with respect to the second rotating member is released, whereby the first rotation Transmission of torque between the member and the second rotating member is released.

  In the present invention, as a characteristic configuration, a rolling member that rolls on both the rotating peripheral surfaces is interposed between the rotating peripheral surface of the first rotating member and the rotating peripheral surface of the second rotating member. Thus, the relative rotation between the first rotating member and the second rotating member is performed via the rolling operation of the rolling member.

The biasing force of the elastic member in the torque limiter acts in a direction in which the rotating peripheral surface of the first rotating member and the rotating peripheral surface of the second rotating member are brought into contact with each other via the pressing member. Then, during the operation of the torque limiter in which torque exceeding the set value acts between the first rotating member and the second rotating member and the torque transmission is released, the rotating peripheral surface of the first rotating member and the second rotating member In the case of a configuration in which the rotating peripheral surfaces of the rotating members of the rotating members are in relative contact with each other in a plane contact state (idle rotation), friction torque is generated on both peripheral surfaces due to the relative rotation in the contact state. Therefore, there is a possibility that the life of the first and rotating members may be reduced.
According to the present invention, since the relative rotation between the first rotating member and the second rotating member is performed via the rolling operation of the rolling member, the first rotating member and the second rotating member described above are provided. Friction torque due to relative rotation with the rotating member can be reduced. As a result, the heat generated by the friction torque can be suppressed, the durability of the first rotating member and the second rotating member can be improved, and as a result, the operating torque of the torque limiter can be stabilized.

  According to the present invention, in a work tool having a torque limiter, a technique that contributes to stabilization of the operating torque of the torque limiter is provided.

(First embodiment of the present invention)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. This embodiment will be described using an electric hammer drill as an example of a work tool. FIG. 1 is a side sectional view showing the overall configuration of the electric hammer drill according to the present embodiment. As shown in FIG. 1, the hammer drill 101 according to the present embodiment is generally viewed as having a main body 103 that forms an outline of the hammer drill 101, and a hollow shape in a tip region (left side in the drawing) of the main body 103. A hammer bit 119 detachably attached via a tool holder 137 and a hand grip 109 gripped by an operator connected to the opposite side of the hammer bit 119 of the main body 103 are mainly configured. The hammer bit 119 is held by the tool holder 137 so that the linear movement in the major axis direction is possible and the relative rotation in the circumferential direction is restricted. The hammer bit 119 corresponds to the “tip tool” in the present invention. For convenience of explanation, the hammer bit 119 side is referred to as the front, and the hand grip 109 side is referred to as the rear.

  The main body 103 includes a motor housing 105 that houses the drive motor 111, and a gear housing 107 that houses the motion conversion mechanism 113, the striking element 115, and the power transmission mechanism 117. The rotational output of the drive motor 111 is appropriately converted into a linear motion by the motion conversion mechanism 113 and then transmitted to the striking element 115, and the major axis direction of the hammer bit 119 (the left-right direction in FIG. 1) via the striking element 115. Generates an impact force on. The rotation output of the drive motor 111 is transmitted to the hammer bit 119 after being appropriately decelerated by the power transmission mechanism 117, and the hammer bit 119 is rotated in the circumferential direction. The drive motor 111 is energized and driven by a pulling operation of a trigger 109 a disposed on the hand grip 109.

  FIG. 2 is a sectional view showing an enlarged state of the main part of the hammer drill 101. The motion conversion mechanism 113 is mainly composed of a drive gear 121, a driven gear 123, a crankshaft 122, a crank plate 125, a crank arm 127, and a piston 129 as a driver, which are driven to rotate in a horizontal plane by a drive motor 111. The crank shaft 122, the crank plate 125, the crank arm 127 and the piston 129 constitute a crank mechanism. The piston 129 is slidably disposed in the cylinder 141 and performs a linear motion along the cylinder 141 as the drive motor 111 is driven to energize.

  The striking element 115 is slidably disposed on the striker 143 slidably disposed on the bore inner wall of the cylinder 141 and the tool holder 137, and transmits the kinetic energy of the striker 143 to the hammer bit 119. And an impact bolt 145 as an intermediate element. The striker 143 is driven via an air spring in the air chamber 141a of the cylinder 141 in accordance with the sliding movement of the piston 129, and collides (hits) with an impact bolt 145 slidably disposed on the tool holder 137. The striking force is transmitted to the hammer bit 119 via the bolt 145.

  The power transmission mechanism 117 includes an intermediate gear 132 that meshes and locks with the drive gear 121, an intermediate shaft 133 that is rotated from the intermediate gear 132 via the torque limiter 151, and a small bevel gear 134 that is rotationally driven in the horizontal plane together with the intermediate shaft 133. A large bevel gear 135 that meshes with and locks with the small bevel gear 134 and rotates in a vertical plane, and a slide sleeve 147 that meshes with and locks with the large bevel gear 135 and is driven to rotate are mainly configured. The rotational driving force of the slide sleeve 147 is transmitted to the tool holder 137 via the cylinder 141 that rotates together with the slide sleeve 147, and further transmitted to the hammer bit 119 held by the tool holder 137. The power transmission mechanism 117 corresponds to the “drive mechanism” in the present invention.

  In the hammer drill 101 configured as described above, when the driving motor 111 is energized and driven by the pulling operation of the trigger 109a by the user, the piston 129 is connected to the cylinder 141 via the motion conversion mechanism 113 mainly composed of a crank mechanism. The striker 143 linearly moves in the cylinder 141 due to a change in air pressure in the air chamber 141a of the cylinder 141, that is, an action of an air spring. The striker 143 collides with the impact bolt 145 to transmit the kinetic energy to the hammer bit 119.

  On the other hand, the rotation output of the drive motor 111 is transmitted to the cylinder 141 via the power transmission mechanism 117. Accordingly, the cylinder 141 is rotationally driven in the vertical plane, the tool holder 137 connected and fixed by the cylinder 141 and the connecting pin 171 is rotationally driven, and the hammer bit 119 held by the tool holder 137 is further moved. It is rotated integrally. Thus, the hammer bit 119 performs the hammering operation in the axial direction and the drilling operation in the circumferential direction, and performs a drilling operation on the workpiece (concrete).

  The hammer drill 101 according to the present embodiment allows the hammer bit 119 to perform only the drill operation in addition to the working mode in the hammer drill mode in which the hammer bit 119 performs the hammer operation and the circumferential drill operation. It is possible to switch to a working mode in the drill mode or a working mode in the hammer mode in which only the hammer operation is performed by the hammer bit 119. However, the mode switching mechanism is not directly related to the present invention. Therefore, the description is omitted.

  Next, the torque limiter 151 incorporated in the power transmission mechanism 117 will be described in detail with reference to FIGS. FIG. 3 shows the overall configuration of the torque limiter 151. The torque limiter 151 transmits the torque of the power transmission mechanism 117 to the hammer bit 119 when the torque acting on the hammer bit 119 is lower than the set value, and when torque exceeding the set value is applied to the hammer bit 119, the torque limiter 151 Provided to block transmission.

  The torque limiter 151 is driven by the intermediate gear 132 rotated by the drive gear 121 (see FIG. 2), the driven flange 153 coupled to the intermediate shaft 133 (see FIG. 2) via a key, and the torque of the intermediate gear 132. A plurality of balls 155 that transmit to the flange 153, a plurality (two) of disc springs 159 that exert a biasing force via the pressing plate 157 to hold each ball 155 in the torque transmitting position, and two disc springs 159 It is mainly composed of a flat washer 173 interposed therebetween. The intermediate gear 132 corresponds to the “first rotating member” in the present invention, the driven flange 153 corresponds to the “second rotating member” in the present invention, and the ball 155 corresponds to the “ball member” in the present invention. Correspond. The pressing plate 157 corresponds to the “pressing member” in the present invention, the disc spring 159 corresponds to the “elastic member” in the present invention, and the washer 173 includes the “parallel state maintaining portion” and the “intervening” in the present invention. Corresponds to “member”.

  The intermediate gear 132, the intermediate shaft 133, the driven flange 153, the pressing plate 157, the disc spring 159, and the washer 173 are arranged in layers on the same axis in the vertical direction (direction intersecting the long axis direction of the hammer bit 119). . A driven flange 153 is disposed on the lower surface side of the intermediate gear 132 with the intermediate gear 132 therebetween, and a pressing plate 157 is disposed on the upper surface side. The intermediate gear 132 is formed with a plurality of ball holding holes 132a at predetermined intervals in the circumferential direction around the rotation axis. The ball holding hole 132a is a through hole having a circular cross section that penetrates in the axial direction, and a ball 155 is fitted in each ball holding hole 132a. Each ball 155 has a lower end projecting from the lower surface of the intermediate gear 132 and contacting the upper surface of the driven flange 153, and an upper end projecting from the upper surface of the intermediate gear 132 and can contact the lower surface of the pressing plate 157. Yes. The pressing plate 157 is loosely fitted to the cylindrical portion 153a of the driven flange 153, and is arranged so that the disc spring 159 overlaps the upper surface thereof. The disc spring 159 is positioned on the cylindrical portion 153a via a nut 161 screwed into the cylindrical portion 153a.

  The two disc springs 159 have an elastic deformation portion 159a formed in a circular disc shape without a bottom, that is, a tapered cylindrical shape, and an outer diameter side edge 159b of the elastic deformation portion 159a of one disc spring 159 is The washer 173 is in contact with the flat lower surface (side surface) 173a of the washer 173, and the outer edge 159b of the elastic deformation portion 159a of the other disc spring 159 is in contact with the flat upper surface (side surface) 173b of the washer 173. And is fitted into the cylindrical portion 153a of the driven flange 153 in a loose fit. The outer diameter side edge 159b corresponds to the “overlapping portion” and “axial end edge” in the present invention, and the flat lower surface 173a and upper surface 173b of the washer 173 correspond to “plane” in the present invention. Also, the inner diameter side edge of the elastic deformation portion 159 a of one disc spring 159 is in contact with the upper surface of the pressing plate 157, and the inner diameter side edge of the elastic deformation portion 159 a of the other disc spring 159 is in contact with the lower surface of the nut 161. Has been. The disc spring 159 arranged as described above applies a biasing force via the pressing plate 157 so as to hold each ball 155 in the torque transmission position.

  4 and 5 each show a driven flange 153. On the contact surface of the driven flange 153 with the ball 155, a plurality of cam portions 163 projecting in the axial direction of the driven flange 153 are formed at predetermined intervals in the circumferential direction centering on the axis of the driven flange 153. Each cam portion 163 is formed in a substantially mountain shape having a slope portion 163a and a flat portion 163b. As shown in FIG. 6, the torque of the intermediate gear 132 is transmitted to the driven flange 153 by locking the ball 155 to the inclined surface portion 163a of the cam portion 163 in the rotational circumferential direction. As shown, the ball 155 moves up the slope portion 163a of the cam portion 163 and rides on the flat portion 163b while pushing up the pressing plate 157 against the urging force of the disc spring 159. Thus, the transmission of torque from the intermediate gear 132 to the driven gear 153 is released. 6 and 7, the arrow X indicates the rotation direction of the intermediate gear 132.

  On the contact surface of the driven flange 153 with the ball 155, a circumferential groove 165 having a curved surface having substantially the same curvature as the spherical surface of the ball 155 is formed over the entire circumference including the cam portion 163. Thereby, the contact between the ball 155 and the driven flange 153 is a line contact regardless of the position of the ball 155 in the inter-cam portion region 164, the slope portion 163a of the cam portion 163, or the flat portion 163b. The groove 165 of the slope portion 163a is continuously formed in the circumferential direction from the deepest groove portion to the shallowest groove portion while maintaining substantially the same curvature as the curvature of the spherical surface of the ball 155. Further, the groove 165 of the flat portion 163b is continuously formed in the circumferential direction at the same depth as the shallowest groove portion of the groove 165 of the slope portion 163a while maintaining substantially the same curvature as the curvature of the spherical surface of the ball 155. Yes. Further, a circumferential groove 167 (see FIG. 3) having a curved surface having substantially the same curvature as the spherical surface of the ball 155 is formed on the contact surface of the pressing plate 157 with the ball 155 over the entire circumference. Thereby, the contact between the ball 155 and the pressing plate 157 is also a line contact.

  Of the grooves 165 formed over the entire circumference of the driven flange 153, the region between the cam portion 163 and the cam portion 163, that is, the groove 165 of the inter-cam portion region 164 other than the cam portion 163 is the inter-cam portion region 164. When the ball 155 is present, the lower surface of the pressing plate 157 is brought into contact with the upper surface of the annular thick portion (boss portion) on the inner diameter side of the intermediate gear 132 and a predetermined gap is formed between the lower surface of the pressing plate 157 and the ball 155. The depth is such that C occurs (see FIGS. 3 and 6). That is, the groove 165 in the inter-cam part region 164 maintains the same curvature as that of the spherical surface of the ball 155 in the circumferential direction at the same depth as the deepest groove part of the groove 165 in the slope part 163a of the cam part 163. It is formed continuously. As a result, when the ball 155 is in the inter-cam portion region 164 and at the torque transmission position where the ball 155 is locked to the inclined surface portion 163a of the cam portion 163, the biasing force (load) of the disc spring 159 is It is set as the structure which does not act on 155. In other words, the driven flange 153 is configured to have a biasing force non-addition region where the biasing force of the disc spring 159 does not act on the ball 155. When the ball 155 is in the inter-cam portion region 164, the ball 155 is allowed to roll.

  Next, the operation of the torque limiter 151 configured as described above will be described. When the driving motor 111 is driven to perform a hammer drilling operation or a drilling operation using the hammer drill 101, the ball 155 is moved to the driven flange 153 in a state where the torque acting on the hammer bit 119 is lower than a predetermined set value. The torque of the intermediate gear 132 is transmitted to the driven flange 153 by being engaged with the inclined surface portion 163a of the cam portion 163 (see FIG. 6). For this reason, the hammer bit 119 is rotationally driven from the driven flange 153 via the intermediate shaft 133, the small bevel gear 134, the large bevel gear 135, the slide sleeve 147, the cylinder 141, and the tool holder 137. When the hammer bit 119 is driven to rotate, the pressing plate 157 is brought into contact with the upper surface of the intermediate gear 132 and the state where the urging force of the disc spring 159 does not act on the ball 155 is maintained. At this time, the locking position (power transmission position) of the ball 155 with respect to the cam portion 163 is allowed to change as the torque acting on the hammer bit 119 varies. That is, the ball 155 is allowed to transmit torque while changing its position between a position contacting the lower surface (groove 167) of the pressing plate 157 and a position separating it.

  On the other hand, when a torque greater than the set value acts on the hammer bit 119, the ball 155 moves up the inclined surface 163 a of the cam portion 163 while pushing up the pressing plate 157 against the biasing force of the disc spring 159, and the cam portion 163. The flat portion 163b is taken up and the locking with the cam portion 163 is released (see FIG. 7). Thereby, the transmission of torque from the intermediate gear 132 to the driven flange 153 is released.

  In the present embodiment, the grooves 165 and 167 formed by curved surfaces having the same curvature as the spherical surface of the ball 155 are provided at the contact portions of the driven flange 153 and the pressing plate 157 with the ball 155, respectively. The contact with the driven flange 153 and the pressing plate 157 of 155 can be a line contact. As a result, the contact portion between the ball 155 and the driven flange 153 and the contact portion between the ball 155 and the pressing plate 157 are increased as compared with the conventional point contact, and the wear of the ball 155, the driven flange 153, and the pressing plate 157 is reduced. it can.

  Further, according to the present embodiment, with respect to the groove 165 formed on the entire circumference of the driven flange 153, the region other than the cam portion 163, that is, the groove 165 in the inter-cam portion region 164 between the adjacent cam portions 163 is set deeply. When the ball 155 is placed at that position, the pressing plate 157 comes into contact with the upper surface of the intermediate gear 132, thereby forming a predetermined gap C between the ball 155 and the pressing plate 157, and the disc spring 159. The urging force is not configured to act. Since the ball 155 placed at this position is allowed to roll arbitrarily, the contact portion of the ball 155 with respect to the driven flange 153 or the pressing plate 157 always changes. As a result, local wear of the ball 155 can be reduced. Thus, according to the present embodiment, the durability of the torque limiter 151 can be improved.

  By the way, the disc spring 159 has a merit that a transmission torque is large and an arrangement space is small, so that the disc spring 159 is suitably used for the torque limiter 151. However, when the two disc springs 159 are arranged so as to face each other so that the outer diameter side edge 159b of the elastically deforming portion 159a directly abuts, the cam portion 163 of the driven flange 153 is placed on the ball. When 155 gets over, that is, when the torque limiter 151 is operated (when the disc spring 159 is compressed), there is a gap between the inner circumference of the hole of the disc spring 159 and the outer circumference of the cylindrical portion 153a. There is a possibility that the outer diameter side edge 159b which is the overlapping portion of 159 is shifted in the radial direction. When a relative displacement in the radial direction occurs between the outer diameter side edges 159b of the disc springs 159, the stability regarding the contact state of the two disc springs 159 is impaired, and the disc springs 159 are tilted to increase the axial length. Thus, the load generated by the disc spring 159 changes.

  In view of the above, in the present embodiment, a flat washer 173 is interposed between two disc springs 159 arranged to face each other. That is, the outer diameter side edge 159b of the elastic deformation portion 159a of one disc spring 159 contacts the lower surface (side surface) of the washer 173, and the outer diameter side edge 159b of the elastic deformation portion 159a of the other disc spring 159 is the washer. The top surface (side surface) of 173 is configured. For this reason, when the torque limiter 151 is operated, even if a relative displacement in the radial direction occurs between the two disc springs 159, the outer diameter side edge 159b of the elastically deforming portion 159a of the two disc springs 159 has a washer. The state of contacting the entire circumferential direction with respect to 173 is maintained, and the parallel state of the disc springs 159 is maintained. For this reason, the disc spring 159 does not tilt, and the total axial length of the disc springs 159 (the axial length of the driven flange 153) does not change. That is, the total length of the two disc springs 159 can be made steady regardless of the relative displacement of the two disc springs 159 in the radial direction. Therefore, the load generated by the disc spring 159 is kept constant, and the operating torque of the torque limiter 151 is stabilized. In the present embodiment, the manufacturing cost can be reduced because the commercially available washer 173 is used as the interposed member interposed between the two disc springs 159.

(Second embodiment of the present invention)
Next, a torque limiter 151 according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 is an enlarged view of the main part. As shown in FIG. 8, in the second embodiment, in the configuration in which two disc springs 159 are arranged so as to face each other so that the outer diameter side edges 159b of the elastic deformation portions 159a abut each other, A flat surface portion 159c that comes into contact with the outer diameter side edge 159b, which is the overlapping portion of the disc springs 159, is provided. Even if it occurs, the disc springs 159 are kept parallel to each other, thereby preventing the disc springs 159 from being inclined due to the deviation and suppressing the change in the axial length of the disc springs 159. Except for this configuration, the configuration is the same as that of the first embodiment described above. Therefore, among the illustrated members, the same constituent members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, for each of the outer diameter side edges 159b of the elastically deforming portions 159a of the two disc springs 159, the surfaces facing each other are planarized in parallel to the outer diameter side edge 159b, and the outer diameter side An annular flat surface portion 159c is formed over the entire circumferential direction of the end edge 159b. Each flat surface portion 159c corresponds to a “parallel state maintaining portion” in the present invention. The radial length (region) of each flat portion 159c is set to a dimension larger than at least the radial gap formed between the hole inner surface of the disc spring 159 and the outer surface of the cylindrical portion 153a of the driven flange 153. The Thus, when the torque limiter 151 is operated, even if a relative radial shift occurs in the outer diameter side edge 159b of the two disc springs 159, the outer diameter side edge 159b of the two disc springs 159 is flat. A state of contacting the entire surface in the circumferential direction by the portion 159c, that is, an annular contact state is maintained. For this reason, the disc spring 159 does not tilt, and the axial length of both disc springs 159 (the axial length of the driven flange 153) does not change. That is, since the total length of the two disc springs 159 can be made steady regardless of the relative displacement in the radial direction of the two disc springs 159, the load generated by the disc spring 159 is held constant, and the torque limiter 151 is maintained. The operating torque of is stabilized. In the case of this embodiment, since the flat portion 159c is provided directly on the disc spring 159, the number of parts is reduced.

(Third embodiment of the present invention)
Next, a third embodiment of the present invention will be described with reference to FIG. This third embodiment corresponds to the invention described in claim 3, and is an improved durability of the cam portion 163 of the torque limiter 151 in order to stabilize the operating torque of the torque limiter 151. .

  In the first embodiment described above, as shown in FIG. 6, the ball 155 is locked to the inclined surface portion 163 a of the cam portion 163 of the driven flange 153, and the torque transmitted from the intermediate gear 132 to the driven flange 153. In the power transmission state of the limiter 151, a predetermined gap C is formed between the ball 155 and the pressing plate 157 by the pressing plate 157 coming into contact with the upper surface of the intermediate gear 132 and the biasing force of the disc spring 159. Is configured not to act on the ball 155. The biasing force of the disc spring 159 acting on the intermediate gear 132 through the pressing plate 157 is received by the lower surface of the intermediate gear 132 coming into contact with the upper surface of the driven flange 153 in a plane contact. That is, in a state where the ball 155 does not ride on the flat portion 163 b of the cam portion 163, the intermediate gear 132 is sandwiched between the pressing plate 157 and the driven flange 153 while receiving the biasing force of the disc spring 159.

  When the torque limiter 151 is operated, an idle rotation (relative rotation) occurs between the driven gear 132 and the driven flange 153. When the torque limiter 151 is operated, the ball 155 rides on the flat portion 163b of the cam portion 163. When there is not (between the cam portions 163), frictional torque due to slip is generated between the intermediate gear 132 and the driven flange 153 and between the intermediate gear 132 and the pressing plate 157. Since the idling rotational speed when the torque limiter is activated is high, the heat generated by the friction torque is large, thereby reducing the life of the cam portion 163. Therefore, the operating torque of the torque limiter 151 is reduced.

  Therefore, as shown in FIG. 10, the torque limiter 151 according to the third embodiment includes a plurality of circumferentially extending portions between the driven flange 153 and the intermediate gear 132 and between the intermediate gear 132 and the pressing plate 157. Thrust load balls 175 and 177 are interposed so that the axial load (thrust direction) due to the biasing force of the disc spring 159 is received by rolling contact. The thrust load balls 175 and 177 correspond to a “rolling member” in claim 3. In the present embodiment, the two disc springs 159 are arranged so as to face each other so that the outer diameter side edges 159b come into contact with each other. Except for the above configuration, the configuration is the same as that of the first embodiment described above. Therefore, among the illustrated members, the same constituent members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, when the torque limiter 151 is operated, when the ball 155 does not ride on the flat portion 163b of the cam portion 163 (see FIG. 6 when it is between the cam portions 163), the intermediate gear 132 is The driven flange 153 and the pressing plate 157 are idle (relative rotation) in the rolling contact state via the thrust load balls 175 and 177. As described above, according to the present embodiment, the configuration in which the biasing force of the disc spring 159 is received by rolling makes it possible to reduce unnecessary friction torque and suppress heat generation. As a result, the life of the cam portion 163 of the driven flange 153 is extended, and the operating torque of the torque limiter 151 is stabilized.

  Further, in the present embodiment, the thrust load ball 175.177 is arranged on an annular groove rail 153b formed on the driven flange 153 and an annular groove rail 132b formed on the intermediate gear 132, respectively. Yes. Therefore, when the torque limiter 151 is operated, when the ball 155 rides on the flat portion 163b of the cam portion 163 (see FIG. 7), the axial distance between the intermediate gear 132 and the driven flange 153, and the intermediate gear 132 Even if the axial distance from the pressing plate 157 increases, the thrust load balls 175 and 177 do not fall off.

  In the above-described embodiment, the ball 155 held by the intermediate gear 132 is engaged with the cam portion 163 of the driven flange 153 to transmit torque, and the ball 155 moves in the axial direction of the intermediate gear 132. In the case of the torque limiter 151 of the type in which the engagement with the cam portion 163 is released and the transmission of torque is cut off, the ball held by the driven flange 153 as disclosed in Patent Document 1 Is engaged with the cam portion 163 provided on the intermediate gear 132, and torque is transmitted. When the ball moves in the radial direction of the driven flange 153, the engagement with the cam portion is released and the torque transmission is interrupted. The present invention may be applied to a torque limiter of a type to be used.

Further, the washer 173 is interposed between the two disc springs 159 described in the first embodiment to maintain a parallel state between the disc springs 159, and the intermediate gear 132 described in the third embodiment is driven. It is possible to carry out in combination with a friction torque reduction technique for reducing the friction torque by interposing the thrust load balls 175 and 177 between the flange 153 and between the intermediate gear 132 and the pressing plate 157, respectively. . In addition, the technology for providing a flat portion on the outer diameter side edge 159b of the two disc springs 159 described in the second embodiment to maintain the parallel state between the disc springs 159, and the friction described in the third embodiment. It can be implemented in combination with torque reduction technology. The number of disc springs 159 is not limited to two.
Moreover, although this Embodiment demonstrated the hammer drill 101 as an example of an example of a working tool, it is not restricted to this, It is applicable if it is a working tool which performs a predetermined | prescribed processing work by rotational movement of a front-end tool. is there.

In view of the gist of the present invention, the following modes can be configured.
(Aspect 1)
“A work tool according to claim 1,
The parallel state maintaining portion is constituted by flat portions that are in contact with each other in a planar shape and are formed at respective axial end edges facing the parallel shape of the plurality of disc springs.
Even if the one disc spring is displaced relative to the other disc spring in the radial direction of the first rotating member, the flat portions maintain the contact state in a planar shape, so that the plurality of disc springs are maintained. A work tool characterized by maintaining the parallel state between the axial edges of each of the plurality of disc springs, thereby stabilizing the overall length of the plurality of disc springs in the axial direction of the first rotating member. "

  According to the invention described in the aspect 1, the number of parts can be reduced because the flat portion as the parallel state maintaining portion is formed directly on the disc spring.

1 is a side sectional view showing an overall configuration of a hammer drill according to a first embodiment of the present invention. It is a side view which shows the principal part of a hammer drill. It is a longitudinal cross-sectional view which shows the whole structure of a torque limiter. It is a top view which shows a driven flange. It is an expanded sectional view based on the AA line in FIG. It is explanatory drawing which shows the transmission state of the torque between an intermediate | middle gear and a driven flange. It is explanatory drawing which shows the transmission interruption | blocking state of the torque between an intermediate | middle gear and a driven flange. It is a longitudinal cross-sectional view which shows the whole structure of the torque limiter which concerns on 2nd Embodiment. It is a principal part enlarged view of 2nd Embodiment. It is a longitudinal cross-sectional view which shows the whole structure of the torque limiter which concerns on 3rd Embodiment.

Explanation of symbols

101 Hammer drill (work tool)
DESCRIPTION OF SYMBOLS 103 Main body part 105 Motor housing 107 Gear housing 109 Grip 109a Trigger 111 Drive motor 113 Motion conversion mechanism 115 Impact element 117 Power transmission mechanism 119 Hammer bit (tip tool)
121 Drive gear 123 Driven gear 125 Crank plate 127 Crank arm 129 Piston 132 Intermediate gear (first rotating member)
132a Ball holding hole 132b Channel rail 133 Intermediate shaft 133a Key 134 Small bevel gear 135 Large bevel gear 137 Tool holder 141 Cylinder 141a Air chamber 143 Strike 145 Impact bolt 147 Slide sleeve 151 Torque limiter 153 Driven flange (second rotating member)
153a Cylindrical portion 153b Groove rail 155 Ball (ball member)
157 Pressing plate (pressing member)
159 Disc spring (elastic member)
159a Elastic deformation part 159b Outer diameter side edge (overlapping part) (Axial direction edge)
159c Plane part (parallel state maintaining part)
161 Nut 163 Cam portion 163a Slope portion 163b Flat portion 165 Groove 164 of driven flange Region between cam portions (intermediate region)
167 Pressing plate groove 171 Connecting pin 173 Washer (parallel state maintaining part, interposition member)
173a Bottom surface (plane)
173b Upper surface (plane)
175, 177 Thrust load ball (rolling member)

Claims (3)

A tip tool that rotates around the long axis direction to perform a predetermined machining operation;
A motor for rotationally driving the tip tool;
A drive mechanism for transmitting the torque of the motor to the tip tool;
The drive mechanism transmits the torque of the motor to the tip tool when the torque acting on the tip tool is lower than a predetermined set value, and when the torque exceeding the set value acts on the tip tool, A work tool having a torque limiter for blocking transmission of torque,
The torque limiter is
A first rotating member arranged to be rotatable around a predetermined axis;
A second rotating member arranged so as to be rotatable about the same axis as the axis of the first rotating member and so that the rotating peripheral surface faces the rotating peripheral surface of the first rotating member;
The first rotating member is held by the first rotating member in a state in which relative movement in the circumferential direction of the first rotating member is impossible and is locked in the circumferential direction with respect to the second rotating member. A ball member that transmits torque between the second rotating member and the second rotating member;
A pressing member that is arranged so as to be movable in the axial direction of the first rotating member, and that can contact the ball member;
An elastic member that exerts an urging force in the axial direction of the first rotating member on the ball member via the pressing member;
In a state where a torque lower than the set value is acting between the first rotating member and the second rotating member, the locking of the ball member with respect to the second rotating member is maintained. Torque is transmitted between the first rotating member and the second rotating member, and a torque exceeding the set value acts between the first rotating member and the second rotating member. Sometimes, the ball member moves in the axial direction or the radial direction against the biasing force of the elastic member acting via the pressing member, and the circumferential locking with respect to the second rotating member is released, Thereby, the transmission of torque between the first rotating member and the second rotating member is released,
The elastic member has a tapered cylindrical elastic deformation portion, and a plurality of the elastic members are arranged on the axis of the first rotating member so that axial end edges of the elastic deformation portion face each other in parallel. Composed of disc springs
Even if one of the plurality of disc springs is relatively displaced in the radial direction of the first rotating member with respect to the other disc spring, the plurality of disc springs are disposed in the overlapping portion of the plurality of disc springs. The working tool characterized by the parallel state maintenance part which maintains the parallel state of the axial direction edges of each other being set. The work tool according to claim 1,
The parallel state maintaining unit is configured by an interposed member having a flat plane that is interposed between the axial end edges of the plurality of disc springs facing in parallel and in contact with the axial end edges,
Even if the one disc spring is displaced relative to the other disc spring in the radial direction of the first rotating member, the interposition member maintains a contact state with the axial end edge via the plane. By maintaining, the parallel state of the axial edges of the plurality of disc springs is maintained, whereby the total length of the plurality of disc springs in the axial direction of the first rotating member is stabilized. Work tools. A tip tool that rotates around the long axis direction to perform a predetermined machining operation;
A motor for rotationally driving the tip tool;
A drive mechanism for transmitting the torque of the motor to the tip tool;
The drive mechanism transmits the torque of the motor to the tip tool when the torque acting on the tip tool is lower than a predetermined set value, and when the torque exceeding the set value acts on the tip tool, A work tool having a torque limiter for blocking transmission of torque,
The torque limiter is
A first rotating member arranged to be rotatable around a predetermined axis;
A second rotating member arranged so as to be rotatable about the same axis as the axis of the first rotating member and so that the rotating peripheral surface faces the rotating peripheral surface of the first rotating member;
The first rotating member is held by the first rotating member in a state in which relative movement in the circumferential direction of the first rotating member is impossible and is locked in the circumferential direction with respect to the second rotating member. A ball member that transmits torque between the second rotating member and the second rotating member;
A pressing member that is arranged so as to be movable in the axial direction of the first rotating member, and that can contact the ball member;
An elastic member that exerts an urging force in the axial direction of the first rotating member on the ball member via the pressing member;
In a state where a torque lower than the set value is acting between the first rotating member and the second rotating member, the locking of the ball member with respect to the second rotating member is maintained. Torque is transmitted between the first rotating member and the second rotating member, and a torque exceeding the set value acts between the first rotating member and the second rotating member. Sometimes, the ball member moves in the axial direction or the radial direction against the biasing force of the elastic member acting via the pressing member, and the circumferential locking with respect to the second rotating member is released, Thereby, the transmission of torque between the first rotating member and the second rotating member is released,
A rolling member that rolls on both the rotating peripheral surfaces is interposed between the rotating peripheral surface of the first rotating member and the rotating peripheral surface of the second rotating member, and the first rotating member A work tool characterized in that relative rotation between the first rotating member and the second rotating member is performed through a rolling operation of the rolling member.

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