JP2006247792A - Screw fastening tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw fastening tool, restraining run-out of a bit fitted as a tip tool, reducing noise (impact sound) and facilitating maintenance for the tool body. <P>SOLUTION: In this screw fastening tool, a fitting hole 52 of a bit 7 is extended from the tip of an output shaft 14k of an anvil 14 to the other end of the anvil 14 receiving the rotary impact force along the axial direction, and provided with a square hole part 14b engaged with the outer peripheral part 7d of the bit 7 and a through hole part 14e penetrating from the end face (base part) 14g of the square hole part 14b toward the other end of the anvil 14. In the through hole part 14e, an elastic body 21 pressed in from the end face 14g of the square hole part 14b is disposed, the end at the square hole part 14b side of the elastic body 21 is provided with a conical recessed part 21e abutting on the outer peripheral end part 7c in the axial direction of the bit 7, whereby the bit 7 is pressed in the axial direction and in the radial direction by the conical recessed part 21e. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a screw tightening tool for tightening a fastener such as a screw, and more particularly to a bit connection structure for mounting a screw tightening bit or a bolt tightening bit used as a tip tool to an output shaft.

  In general, an impact tool (rotary impact tool), which is an example of an electric screw tightening tool, is provided with a motor as a drive source, a spindle that is rotated by a motor via a power transmission mechanism, and the spindle. A mounting hole (usually having a hammer that movably engages in the axial direction and gives a rotational striking force, and an output shaft that rotates with the striking force of the hammer, and a bit of a tip tool can be attached to the output shaft And an anvil having a hexagonal cross section) and a bit retaining device for fixing a tip tool such as a bit inserted into the mounting hole to the output shaft. Similarly, even in an electric driver tool that does not have a hammer mechanism, a bit retaining device that removably fixes a tip tool such as a driver bit is provided on an output shaft that is rotated by a motor via a power transmission mechanism. An example of such a screw tightening tool is shown in Patent Document 1 below, for example.

  Screw tightening tools are used in various work sites such as construction sites such as houses or buildings and construction sites such as electricity, gas, water, and pipe work, so the heads of bits (tip tools) such as bolts or screws to be tightened According to the shape of the part, there is provided a bit retaining device capable of easily attaching and detaching a screw fastening bit or a bolt fastening bit. As disclosed in Patent Document 1, generally, a bit retaining device has a first engagement groove portion provided at a predetermined position on an outer peripheral portion of a bit, and a first engagement by inserting the bit into a mounting hole. The second engagement groove portion provided on the output shaft is engaged with both grooves of the first engagement groove portion and the second engagement groove portion in a state of retaining the bit, so as to correspond to the groove portion. A steel ball (ball) and a guide sleeve member provided on the output shaft to fix the steel ball to the first engagement groove portion in a freely engageable manner. For example, the guide sleeve member is supported so as to be slidable in the axial direction from the inner end side of the output shaft to the outer end side (tip side). For example, when the guide sleeve member is slid to the outer end side (tip direction) of the output shaft, Can be detached from the first engagement groove on the outer periphery of the bit, and the bit can be inserted into and removed from the mounting hole of the output shaft. On the other hand, if the guide sleeve is slid so as to return from the outer end side to the inner end side in the axial direction with the angular shaft portion (usually hexagonal shaft portion) of the bit inserted into the mounting hole, When the steel ball engages with both the first engagement groove and the second engagement groove, the bit inserted into the attachment hole is fixed in the attachment hole in a retaining state. In general, the sliding movement of the guide sleeve from the outer end side to the inner end side in the output shaft direction is automatically returned by a spring force.

Japanese Utility Model Publication No. 5-9863

  In a screw tightening operation using a screw tightening tool, a plus bit is often used for both heads (both ends) as a screw tightening bit as a tip tool. When tightening a member to be tightened such as a plate with a screw, if the runout (rotational runout) occurs at the tip of the bit mounted on the screw tightening tool, the cross hole of the fastener screw and the cross hole of the tip tool bit will come off. It becomes easy to cause problems such as a decrease in work efficiency and processing accuracy by the screw tightening tool, and damage to a tightening tool and a member to be tightened (workpiece). For this reason, screw tightening tools are required to minimize bit runout of the tip tool. Further, in order to improve workability, an operator may work in a state in which a bit as a tip tool is lengthened and the screw tightening tool main body is separated from a member to be tightened such as a plate. Accordingly, the longer the bit to be used, the more the deflection of the bit becomes larger, which tends to cause problems such as a decrease in processing accuracy and damage to the fasteners. This bit runout is caused by the hexagonal mounting hole of the anvil and the peripheral processing accuracy of the bit. Further, it is also caused by the degree of wear of steel balls (balls) used in the bit retaining device. The technology disclosed in Patent Document 1 includes a socket that functions as a part of an output shaft by fitting an output shaft that applies a rotational force of a motor to a driver bit and a socket to which the bit is attached via an elastic ring. The motor is fitted between the output rotation shafts of the motor without any gaps, and the rotational runout of the socket serving as the output shaft is suppressed. The technology disclosed in this patent document is different from a bit prevention device that is mounted on a socket serving as an output shaft, and that prevents bit fluctuations based on rattling between the driver bits.

  Another problem that becomes a problem in screw tightening work with a screw tightening tool is noise generation. Recently, the hitting sound has been reduced by optimizing the hitting timing of the tool, but there is an insufficient noise reduction. Noise during the operation of the screw tightening tool can be classified into two types: a component generated from the tool body and a component generated from a member to be tightened such as a plate on which screw tightening is performed. In particular, it has been found that noise energy generated from the tightened member occupies a large proportion. In order to reduce the noise, it is important to reduce the axial striking force transmitted to the member to be tightened, but the present situation is not realized.

  Further, in a bolt tightening operation in which a hexagon bolt is tightened with a screw tightening tool, a bolt tightening bit in which a hedgagon (hexagon) socket is integrally formed at the tip of the bit is used. In particular, in recent years, screw tightening tools have been reduced in size, weight, and power, and the bit part (hexagonal shaft part) of the tip tool in the mounting hole of the anvil can also be considered. In the conventional anvil bit mounting structure, if the bit is damaged in the anvil, the anvil is clogged, and in the worst case, the entire anvil must be repaired or replaced. .

  Accordingly, a main object of the present invention is to provide a bit connection structure for attaching a bit to an anvil output shaft, which is suitable for use of a long bit, in which the deflection of the bit tip is reduced.

  Another object of the present invention is to provide a bit connection structure that reduces the generation of noise in a screw tightening tool.

  Still another object of the present invention is to provide a bit connection structure in which a broken bit portion can be easily taken out from a mounting hole of an anvil.

  According to one aspect of the present invention, a motor as a drive source, a spindle that is rotated by a power transmission mechanism via a power transmission mechanism, and a spindle that is attached to the spindle and is movable in the direction of the rotation axis of the spindle. And an anvil having a hammer that gives a rotational striking force, an output shaft that is rotated by the rotational striking force of the hammer, and a mounting hole in which a bit can be mounted on the output shaft, and is inserted into the mounting hole. A screw tightening tool comprising a bit retaining device attached to the output shaft of the anvil to fix the bit to the output shaft so that the bit does not come off, wherein the mounting hole is a tip of the output shaft of the anvil A square hole portion extending along the axial direction from the side to the other end side of the anvil receiving the rotational impact force of the hammer, and engaging with a bit outer peripheral portion of the tip tool, and an end surface of the square hole portion A through-hole portion penetrating to the other end of the anvil, and an elastic body press-fitted from an end surface of the square hole portion is disposed in the through-hole portion, and the square hole of the elastic body It has a conical concave portion in contact with the outer peripheral end portion in the axial direction of the bit at the end portion on the portion side, and the bit is pressed in the axial direction and the radial direction by the conical concave portion.

  According to another feature of the present invention, in a state before a fastening tool such as a screw is tightened by the screw tightening tool, the bit is pressed against the bit retaining device by the conical recess of the elastic body, The bit is fixedly held on the output shaft.

  According to still another aspect of the present invention, when the bit is pressed by the output shaft in a state where a fastener such as a screw is tightened by the impact tool, the axial load of the bit is applied to the square hole. It receives by the level | step-difference part in the said attachment hole provided between the part and the said through-hole part, It is characterized by the above-mentioned.

  According to still another feature of the present invention, the elastic body press-fitted into the through-hole portion can be removed by pressing from the other end side of the anvil.

  According to still another aspect of the present invention, the bit retaining device includes a first engagement groove provided at a predetermined position on an outer peripheral portion of the bit, and the first engagement by inserting the bit into the mounting hole. A second engagement groove provided on the output shaft so as to correspond to the joint groove, a steel ball engaged with both the first engagement groove and the second engagement groove, and the steel ball And a guide sleeve member provided on an output shaft for slidably fixing the first engagement groove portion to the first engagement groove portion, and in a state before a fastening tool such as a screw is tightened, the cone of the elastic body The bit is fixedly held on the output shaft by pressing the bit against a steel ball of the bit retaining device by means of a concave portion.

  According to the present invention, an elastic body press-fitted from the end face of the square hole portion is disposed in the through hole portion, and an axial direction of the bit is provided at an end portion of the elastic body on the square hole portion side. A conical recess that abuts on the outer peripheral end of the bit, and the conical recess presses the bit in the axial direction and the radial direction. The operability can be improved.

  According to the present invention, since the elastic body is press-fitted into the through-hole portion of the anvil, the axial force (blowing force) transmitted from the anvil to the bit is interrupted to generate from the tightened member. Noise can be reduced.

  Further, according to the present invention, the elastic body provided in the through hole portion of the anvil is made removable by the through hole, so that the bolt tightening bit portion (the bolt tightening hexagon socket of the bolt tightening) clogged in the anvil. The damaged part of the shaft part can be easily removed. Therefore, it is not necessary to replace the anvil when the bit is broken.

  The above and other objects of the present invention as well as the above and other novel features of the present invention will become more apparent from the following description of the present specification and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  FIG. 1 is a sectional view showing an entire tool in which a screw tightening tool according to the present invention is applied to a cordless type impact driver. 2 and 3 are partially enlarged sectional views showing a connection structure between the anvil and the bit of the screw tightening tool shown in FIG. 1, and FIG. 2 shows a state before the screw is fastened to the member to be fastened. Indicates a state in which the screw is fastened to the member to be fastened. 4 and 5 are partially enlarged sectional views of the anvil of the screw tightening tool shown in FIG. 1, FIG. 4 is a sectional view including a bit mounting member attached to the anvil, and FIG. 5 is a sectional view of the anvil itself. Indicates. 6A and 6B are structural views of an elastic body press-fitted into the through hole of the anvil. FIG. 6A is a left side view, FIG. 6B is a front view (cross-sectional view), and FIG.

  First, the entire screw tightening tool will be described with reference to FIG. A screw tightening tool 6 according to an embodiment of the present invention extends from one end (the left end in the drawing) to the other end (the right end in the drawing) along a horizontal axis in the same direction as the rotation axis of the motor 2 described later. A tool body composed of a body housing portion 6a and a handle housing portion 6b depending from the body housing portion 6a. The distal end portion of the body housing portion 6a receives a rotational impact force from the tool body and is tightened. A driver bit (tip tool) 7 for fastening the screw 8 of the fastening tool to the attaching member 11 is detachably attached. Instead of the driver bit 7 as a tip tool, a bolt tightening bit can be mounted as will be described later.

  A motor 2 serving as a drive source is attached to one end of the body housing portion 6a, and a tip tool 7 that outputs a rotational impact force is attached to the other end of the body housing portion 6a. In the middle part of the body housing part 6a, a power transmission mechanism part (deceleration mechanism part) 50 for transmitting a rotational force in the direction of the rotational axis of the motor 2, an impact mechanism part 51 for giving the rotational impact force, and the impact mechanism part 51 An anvil 14 that transmits the rotational impact force to the tip tool 7 is mounted.

  A battery pack case 1 serving as a driving power source for the motor 2 is detachably attached to the handle housing portion 6b at the lower end portion of the handle housing portion 6b. The battery pack case 1 has a battery pack main body 1a, and most of the battery pack main body 1a is inserted and accommodated in the handle housing portion 6b. The battery pack main body 1a is electrically connected to the motor 2 via the switch 6c.

  The rotational force of the rotating shaft 2a of the motor 2 is transmitted to the spindle 9 constituting a part of the impact mechanism portion 51 through the speed reduction mechanism portion 50 engaged with the gear teeth provided at the end of the rotating shaft 2a. . The power transmission mechanism (deceleration mechanism) 50 includes a pinion gear (sun gear) 2b provided on the rotating shaft 2a and a plurality of planetary gears 3 meshing with the pinion gear 2b, which are incorporated in the inner cover 50a. It is. The spindle 9 is given a rotational force that is decelerated relative to the rotation of the motor 2 by the speed reduction mechanism 50.

  As shown in FIGS. 2 and 3, the impact mechanism 51 is housed in a hammer case 5b made of a metal material such as an aluminum alloy, and a spindle 9 to which a rotational force is applied via the speed reduction mechanism 50, and the spindle 9 The hammer 5 is movably engaged with the spindle 9 so as to be movable in the direction of the axis of rotation, and gives a rotary striking force. The anvil 14 rotates with the striking force of the hammer 5 and has an output shaft 14k. The hammer 5 and the anvil 14 respectively have two hammer convex portions (blow portions) 5a and two anvil convex portions 14a that are symmetrically arranged at two locations on the rotation plane, and the hammer convex portion 5a and the anvil. The convex part 14a exists in the position which meshes with a rotation direction. As described later, the rotational impact force is transmitted by the meshing of the convex portions 5a and 14a. Further, the hammer 5 is slidable in the axial direction relative to the spindle 9 in a ring region surrounding the spindle 9 and is urged forward in the axial direction by the spring 4. An inverted V-shaped (substantially triangular) cam groove 5 c is provided on the inner peripheral surface of the hammer 5. On the other hand, a V-shaped cam groove 9 a is provided in the axial direction on the outer peripheral surface of the spindle 9, and a ball (steel ball) 10 inserted between the cam groove 9 a and the inner peripheral cam groove 5 c of the hammer 5. The hammer 5 rotates through the. At this time, if the rotational torque of the hammer 5 is smaller than the load torque for rotating the fastener 8 such as a screw of the workpiece (workpiece) 11, the hammer 5 moves along the cam groove 9a. When the spring 4 is retracted while being compressed while being twisted and the hammer convex portion 5a is separated from the coupling with the anvil convex portion 14a, the hammer 5 gets over the anvil 14, and further, the hammer 5 is biased by the spring 4 and cams. Receiving the guide by the groove 9a, it advances while rotating, and impact torque is given to the anvil convex portion 14a of the anvil 14 in front of the rotation by the hammer convex portion (striking portion) 5a. As will be described later, this impact torque is transmitted to the driver bit 7 attached to the output shaft 14k of the anvil 14, and further, the rotational impact torque is transmitted from the driver bit 7 to the fastener screw 8 to be fastened. Tighten to (see Fig. 3).

  Next, the operation | movement of the rotation impact by the above structure is demonstrated. The rotational force of the spindle 9 is transmitted to the hammer 5 via the cam mechanisms 9a and 5c, and the spindle 9 and the hammer 5 start to rotate together. Before the half rotation, as described above, the hammer 5 and the convex portions 5a and 14a of the anvil 14 mesh with each other. The spindle 9 and the hammer 5 are twisted relatively, and the hammer 5 starts to retract while the spring 4 is contracted. If the hammer 5 gets over the height of the anvil convex part 14a after starting to move backward, the mesh with the anvil 14 is released. The hammer 5 is accelerated in the rotational direction by the elastic energy stored in the spring 4 in addition to the rotational force of the spindle 9 and starts moving forward. While the hammer 5 is being accelerated, the hammer convex portion 5a and the anvil convex portion 14a are engaged with each other again. At this time, a strong rotational striking force is applied to the anvil 14, via the bit 7. Transmitted to screw 8. Thereafter, the hammer 5 starts to retract again, and the above operation is repeated.

  Next, an attachment device for attaching the driver bit 7 to the anvil 14 used in the present invention will be described. As shown in FIGS. 4 and 5, the output shaft 14 k of the anvil 14 has a mounting hole 52 in which the bit 7 can be mounted. The attachment hole 52 has a square hole portion 14b and a through hole portion 14e. The square hole portion 14b extends along the axial direction from the tip end side of the output shaft 14k to the other end side of the anvil 14 that receives the rotational striking force of the hammer 5, and the outer peripheral portion 7d (see FIG. 2). The cross-sectional shape of the square hole portion 14b is, for example, a hexagonal hole corresponding to a hexagonal bit. The through hole portion 14e penetrates from the step portion (end surface of the square hole portion) 14g of the square hole portion 14b to the other end side of the anvil 14 that receives the rotational impact force of the hammer 5. The diameter of the through hole 14e is smaller than the diameter of the square hole 14b, and the step 14g is formed at the boundary between the square hole 14b and the through hole 14e. The anvil 14 including the square hole portion 14b is generally manufactured by a cold forging technique.

  As shown in FIGS. 4 and 5, a bit retaining device 53 for detachably attaching the bit 7 shown in FIG. 2 or 3 is attached to the tip of the output shaft 14 k of the anvil 14. In general, the bit 7 is formed of, for example, a hexagonal column, and has cross-shaped driver portions 7a at both end portions (both heads) in the axial direction. On the base side of the cross driver portion 7a, a groove portion (first engagement groove portion) 7b for retaining is formed over the entire circumference.

  As shown in FIGS. 2 and 4, the bit retaining device 53 includes the first engagement groove portion 7 b provided at a predetermined position on the outer peripheral portion of the bit 7 b and the bit 7 in the square hole portion 14 b of the mounting hole 52. Is inserted into the output shaft 14k so as to correspond to the first engagement groove 7b, the first engagement groove 7b and the second engagement. The steel ball 15 is engaged with both grooves of the groove portion 14c, and the guide sleeve member 16 is provided on the output shaft 14k for fixing the steel ball 15 to the first engagement groove portion 7b.

  As shown in FIG. 4, the steel balls 15 are disposed at two locations around the cylinder of the output shaft 14k. The steel ball 15 has a groove portion (long hole portion) 14c provided on the side surface of the anvil 14 by a step portion (projecting portion) 16a on the inner peripheral side of the guide sleeve member 16 disposed on the outer peripheral end of the anvil 14. The inside can enter and exit inside or outside the inner peripheral surface of the square hole portion 14b. The groove part (elongate hole part) 14c provided on the side surface of the anvil 14 has a groove width or a hole diameter so that the steel ball 15 does not fall inside the square hole part 14b.

  As shown in FIG. 4, the guide sleeve member 16 is rotatably or slidably attached to the outer periphery of the anvil 14 and is mounted so as not to fall off by a retaining ring 17 and a washer 18 in the axial direction. Further, a compression spring 19 is interposed between the guide sleeve member 16 and the washer 18, and the guide sleeve member 16 is urged in the B direction (see FIG. 1) by the compression spring 19. The guide sleeve member 16 is always urged by the compression spring 19 and, as shown in FIG. 2, abuts against the step surface 14d (see FIG. 5) of the anvil 14 by the step portion (projecting portion) 16a inside the guide sleeve member 16. The steel ball 15 is held inside the square hole portion 14b. Thus, if the bit 7 is inserted into the square hole portion 14b of the anvil 14, the steel ball 15 is engaged or hooked with the retaining groove portion 7b of the bit 7, and the bit 7 can be fixedly held. If the guide sleeve member 16 is moved in the A direction (see FIG. 2) against the spring force of the compression spring 19, the step portion 16a of the guide sleeve member 16 is moved in the A direction from the groove portion (long hole portion) 14c. Moving. By this movement, the inner peripheral diameter of the guide sleeve member 16 increases, and the steel ball 15 moves outward in the radial direction from the inner peripheral surface of the square hole portion 14b. As a result, the engagement or latching between the steel ball 15 and the retaining groove 7b of the bit 7 is released, and the bit 7 can be attached and detached.

  In the tip tool mounting apparatus configured as described above, the bit 7 can be easily inserted or removed while the guide sleeve 16 is moved in the A direction. In addition, when the bit 7 is mounted in the mounting hole 52, the steel ball 15 is securely held by engaging the retaining groove 7 b of the bit 7 and the groove (long hole) 14 c of the anvil 14. can do.

  In the mounting device for the bit 7 including the above configuration, the following bit runout prevention structure is further mounted according to the present invention. The cause of rotational runout of the bit 7 is rattling between the mounting hole 52 (square hole portion 14b) of the anvil 14 and the bit 7 fitted in the mounting hole 52, and the square hole portion (hexagonal hole portion). ) Due to the bending accuracy (machining accuracy) of 14b. According to the present invention, the elastic body 21 is disposed in the through hole portion 14e of the anvil 14 in order to prevent this rotational shake.

  That is, as shown in FIG. 4, an elastic body 21 press-fitted from the stepped portion 14g of the square hole portion 14b is disposed in the through hole portion 14e, and the end portion of the elastic body 21 on the square hole portion 14b side is disposed. Has a conical recess 21e that abuts on the outer peripheral end (tapered portion) 7c of the bit 7 in the axial direction, and the bit 7 is pressed in the axial direction and the radial direction by the conical recess 21e.

  As shown in FIGS. 4 and 6, the elastic body 21 includes a shaft portion 21 a provided for fitting with the through-hole portion 14 e of the anvil 14, and a cone provided at the end portion on the square hole portion 14 b side. And a concave portion 21e. The conical recess 21e is formed so as to be engaged with or fitted to the outer peripheral end (tapered portion) 7c of the cross driver bit 7 in contact with the tapered inner peripheral portion 21b. A small hole portion 21d having a smaller diameter than the conical recess portion 21e is formed on the inner diameter of the bottom portion of the conical recess portion 21e so that the elastic body 21 can be easily deformed by contact with the outer peripheral end portion 7c of the bit 7. ing. The elastic body 21 is formed by press-fitting the shaft portion 21a in the B direction into a through-hole portion 14e provided in a terminal surface (stepped portion) 14g of the square hole portion 14b of the anvil 14, whereby the square hole portion 14b. Is fixedly held in a through hole portion 14e communicating with the end surface 14g. The elastic body 21 is automatically fixed at a predetermined position because the step portion 21c provided on the elastic body 21 is hooked on the step portion 14h (see FIG. 5) formed on the inner peripheral surface of the through hole portion 14e. The Further, since the stepped portion 14h functions as a stopper, the elastic body 21 does not fall off to the hammer 5 side (B direction) by press-fitting in the B direction.

  As shown in FIG. 2, in the state before the screw 8 is fastened to the member to be fastened 11 (see FIG. 1), a large force does not act on the bit 7 in the B direction. The outer peripheral end of the bit 7 is pressed in the A direction by (biasing force). The bit 7 pushed out in the direction A is pushed out until the retaining groove 7b of the bit 7 hits the steel ball 15 in the groove 14c of the anvil 14, and stops at the position where the steel ball 15 is engaged. As a result, the outer peripheral end 7 c of the bit 7 is pressed in the radial direction by the conical recess 21 e of the elastic body 21, and there is no radial play between the bit 7 and the elastic body 21. Further, the guide sleeve 16 is moved in the B direction by the spring force of the compression spring 19, and the steel ball 15 is urged to the inside of the inner peripheral surface of the square hole portion 14b by the step portion 16a. It is adjusted to the center position of the hole 14b. In this way, the vibration can be suppressed by the action of the elastic body 21 and the steel ball 15 without being affected by the processing accuracy of the square hole portion 14b.

  Furthermore, by providing the small hole portion 21d, the elastic body 21 is easily deformed when the tip of the bit 7 comes into contact with the shaft portion 21a of the elastic body 21. Thereby, a substantially uniform load can be applied to the elastic body 21 with respect to the variation in the length of the bit 7 in the axial direction, in other words, the variation in the length of the bit taper portion 7c. That is, the difference between the pressing force when the bit 7 having the short bit taper portion 7c is inserted and the pressing force when the bit 7 having the long bit taper portion 7c is inserted becomes small. Due to the variation in the thickness, a difference in the rotational shake prevention effect of the bit 7 is less likely to occur, and stable performance can be exhibited.

  Next, as shown in FIG. 3, when the screw 8 is tightened to the member to be tightened 11, the tool body is pressed in the A direction to prevent the cross hole bit 7 from coming off from the cross hole of the screw 8. A state in which thrust is applied and rotational impact force is applied will be described. In this state, the bit 7 moves in the B direction, the outer peripheral end (tapered portion) 7c of the bit 7 hits the stepped portion 14g of the anvil 14, and receives the load of the bit 7 by the stepped portion 14g of the anvil 14. Become. Accordingly, a clearance is generated between the retaining groove 7b of the bit 7 and the steel ball 15, and a large load is not applied to the steel ball 15. As a result, the wear of the steel ball 15 can be prevented and the life can be extended.

  In the state of loading to the bit 7 shown in FIG. 3, the elastic body 21 is deeply fitted to the outer peripheral end (tapered portion) 7 c of the bit 7, but is provided on the inner diameter of the conical recess 21 e of the elastic body 21. Since the small hole portion 21d is present, it does not abut against the tip end portion of the outer peripheral end portion 7c of the bit 7, and the elastic body 21 is not damaged such as a crack. Further, since the outer peripheral end portion (tapered portion) 7c of the bit 7 abuts against the stepped portion 14g of the anvil 14, an unnecessarily large force does not act on the elastic body 21, and as a result, the life of the elastic body 21 is extended. Can also be planned.

  Next, in order to reduce the noise when the screw 8 is fastened to the tightening member 11 (see FIG. 3), as described above, the axial striking force transmitted to the tightening member 11 can be reduced. is important. According to the present invention, the elastic body 21 disposed at the bottom of the square hole portion 14b can reduce transmission of force in the axial direction to the bit 7 when the hammer 5 strikes the anvil 14. it can. Accordingly, the axial excitation force transmitted to the tightening member 11 is reduced, and noise generated from the tightening member 11 can be reduced.

  In the screw tightening tool 6 described above, the driver bit 7 is replaced, and a bolt tightening bit (heg gon socket) 12 is mounted in the square hole portion 14b of the output shaft 14k of the anvil 14 as shown in FIG. When the bolts and nuts 13 for fastening the members to be tightened 11, 11a and 11b are tightened, the bit shaft portion (hexagon shaft portion) 12a may be damaged. As shown in FIG. 8, breakage of the bolt fastening bit 12 is likely to occur at the bit shaft portion 12a having the weakest strength, and in particular, there is a high probability that it will occur at the tip surface 14f of the anvil 14. If it breaks in the square hole portion 14b, it may become clogged in the square hole portion 14b, making it impossible to pick out the remaining member using pliers or the like.

  According to the present invention, as shown in FIGS. 9A, 9B, and 9C, the remaining member in the square hole portion 14b can be easily removed. That is, as shown in FIGS. 9A and 9B, the pin 20 is inserted into the through hole 14e from the engagement side of the hammer 5 of the anvil 14 and the elastic body 21 is pushed out, so that the square hole of the anvil 14 is extruded. The damaged bit shaft portion 12a clogged in the portion 14b can be taken out from the front end surface 14f of the anvil 14. As shown in FIG. 9C, if the elastic body 21 is press-fitted again into the through hole 14e from the stepped portion 14g after the bit shaft portion 12a is taken out, the function of the tool body returns to the original state. Bit 12 can be reattached.

  Another advantage of press-fitting the elastic body 21 into the through-hole portion 14e of the mounting hole 52 is that a large amount of lubricating grease is used by the elastic body 21 inside the hammer case 5b (see FIG. 2) of the screw tightening tool 6. It is sealed and can prevent grease leakage.

  As will be apparent from the above description, according to the present invention, an elastic body press-fitted from the end surface of the square hole portion is disposed in the through hole portion, and the elastic body on the square hole portion side of the elastic body is disposed. The end has a conical recess that contacts the outer peripheral end of the bit in the axial direction, and the conical recess presses the bit in the axial direction and the radial direction, thereby suppressing the deflection of the bit tip. Therefore, the operability of the screw tightening tool can be improved.

  Further, according to the present invention, since the elastic body is press-fitted in the through hole portion of the anvil, the axial force (blowing force) transmitted from the anvil to the bit is cut off, so that the tightening member The generated noise can be reduced.

  Furthermore, according to the present invention, the elastic body provided in the through hole portion of the anvil is removable by the through hole, so that the bolt tightening bit portion (the bolt tightening hexagon socket of the bolt tightening) clogged in the anvil. The damaged part of the shaft part can be easily removed. Therefore, it is not necessary to replace the anvil when the bit is broken.

  In the above embodiment, the rotary impact tool (impact tool) has been described. However, the present invention is not limited to the rotary impact tool, and the output shaft of the rotary tool not provided with a means for imparting the rotational impact, such as an electric driver tool. Further, it can be applied as a bit connection structure for attaching a bit.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. It is.

Sectional drawing of the screw fastening tool which concerns on one Embodiment of this invention. The partial expanded sectional view in the state before screw fastening with the screw fastening tool shown in FIG. The partial expanded sectional view in the state at the time of screw fastening with the screw fastening tool shown in FIG. The partial expanded sectional view which shows the anvil and elastic body which are used for the screw fastening tool shown in FIG. The partial expanded sectional view which shows the anvil used for the screw fastening tool shown in FIG. The partial expanded sectional view which shows the elastic body used for the screw fastening tool shown in FIG. The partial expanded sectional view which used the bit for bolt fastening with the screw fastening tool shown in FIG. The partial expanded sectional view which shows the state which the bit for bolt fastening was damaged with the screw fastening tool shown in FIG. FIG. 9 is a state diagram when a bolt tightening bit shaft portion damaged by the screw tightening tool shown in FIG. 8 is taken out.

Explanation of symbols

1: Battery pack case 1a: Battery pack body 2: Motor 2a: Motor rotating shaft 2b: Pinion gear (sun gear)
3: Planetary gear 4: Spring 5: Hammer 5 a: Hammer convex part (striking part) 5 b: Hammer case 5 c: Cam groove on hammer inner peripheral surface 6: Screw tightening tool 6 a: Body housing part 6 b: Handle housing part 6 c: Switch 7: Bit 7a: Cross driver 7b: Engaging groove (first engaging groove)
7c: Bit outer peripheral end (tapered portion) 7d: Bit outer peripheral portion 8: Screw 9: Spindle 9a: Spindle outer peripheral cam groove 10: Cam ball (steel ball) 11: Fastened member 12: bolt tightening Attached bit (Hegzagon socket)
12a: Bit shaft portion (hexagon shaft portion) 12b: Groove portion (first groove portion)
13: Hexagon bolt 14: Anvil 14a: Anvil convex part 14b: Square hole part (hexagonal hole part) of anvil
14c: Anvil engagement groove (second engagement groove) (long hole)
14d: Stepped surface 14e: Through hole 14f: Anvil tip surface 14g: Stepped portion (end surface of square hole) 14h: Stepped portion 14k of through hole: Output shaft of anvil 15: Steel ball (ball)
16: Guide sleeve member 16a: Stepped portion (projecting portion) 17: Retaining ring 18: Washer 19: Compression spring 20: Pin 21: Elastic body 21a: Shaft portion of elastic body 21b: Tapered portion 21c: Stepped portion 21d of elastic body : Small hole 21e of elastic body 21e: Conical recess 50 of elastic body 50: Power transmission mechanism (deceleration mechanism) 50a: Inner cover 51: Impact mechanism 52: Mounting hole 53: Bit retaining device

Claims (6)

A motor serving as a drive source; a spindle to which rotation is given by a motor via a power transmission mechanism; a hammer attached to the spindle and movably engaged in the direction of the rotation axis of the spindle to give a rotational striking force; An anvil having an output shaft that is rotated by a rotational striking force of the hammer and having a mounting hole in which the bit can be attached to the output shaft, and the output shaft so that the bit inserted into the mounting hole cannot be removed. A screw fastening tool comprising a bit retaining device attached to the output shaft of the anvil for fixing to the anvil,
The mounting hole extends along the axial direction from the front end side of the output shaft of the anvil to the other end side of the anvil that receives the rotational striking force of the hammer, and engages with the outer peripheral portion of the bit. And a through-hole portion penetrating from the end surface of the square hole portion to the other end side of the anvil,
An elastic body that is press-fitted from the end surface of the square hole portion is disposed in the through hole portion, and an end portion of the elastic body on the square hole portion side is in contact with an outer peripheral end portion in the axial direction of the bit. A screw tightening tool having a conical concave portion in contact with the bit and pressing the bit in an axial direction and a radial direction by the conical concave portion.   The bit is fixedly held on the output shaft by pressing the bit against the bit retaining device by the conical recess of the elastic body in a state before the fastening tool such as a screw is tightened by the screw tightening tool. 2. The screw tightening tool according to claim 1, wherein   When the bit is pressed by the output shaft in a state where a tightening tool such as a screw is tightened by the screw tightening tool, an axial load of the bit is provided between the square hole portion and the through hole portion. The screw tightening tool according to claim 1, wherein the screw tightening tool is received by a stepped portion.   2. The screw tightening tool according to claim 1, wherein the elastic body press-fitted into the through-hole portion can be removed by pressing from the other end side of the anvil.   The bit retaining device includes a first engagement groove portion provided at a predetermined position on an outer peripheral portion of the bit, and the output shaft so as to correspond to the first engagement groove portion by inserting the bit into the mounting hole. A second engaging groove portion provided, a steel ball engaging both the first engaging groove portion and the second engaging groove portion, and engaging the steel ball with the first engaging groove portion The screw tightening tool according to any one of claims 1 to 4, further comprising a guide sleeve member provided on an output shaft for freely fixing. A motor serving as a drive source, an output shaft having a mounting hole to which a rotational force is applied by the motor via a power transmission mechanism and a bit can be mounted, and the bit inserted into the mounting hole are prevented from being removed. A screw tightening tool including a bit retaining device for fixing to the output shaft,
The mounting hole extends along the axial direction from the distal end side of the output shaft to the other end side of the output shaft where the power transmission mechanism is disposed, and engages with an outer peripheral portion of the bit. And a through-hole portion penetrating from the end surface of the square hole portion to the other end side of the output shaft,
An elastic body that is press-fitted from the end surface of the square hole portion is disposed in the through hole portion, and an end portion of the elastic body on the square hole portion side is in contact with an outer peripheral end portion in the axial direction of the bit. A screw tightening tool having a conical concave portion in contact with the bit and pressing the bit in an axial direction and a radial direction by the conical concave portion.

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