Hammer drill

Abstract

To provide a technique that can contribute to facilitating work for connecting a tool holder of a hammer drill to a cylinder.SOLUTION: A hammer drill comprises a tool main body, a tool holder, a cylinder and a connection member. The tool holder, formed in a cylindrical shape, has a long shaft. The tool holder, configured to hold a tip tool movably along the long shaft, is supported on the tool main body rotatably around the long shaft. The cylinder is extended concentrically with the tool holder and is supported on the tool man body rotatably around the long shaft. The connection member lies between the tool holder and the cylinder in a radial direction, which engages with the tool holder and the cylinder and connects the holder to the cylinder so that the tool holder and the cylinder rotate integrally.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a hammer drill, and more particularly to a hammer drill including a tool holder configured to removably hold a tool bit and a cylinder coupled to the tool holder. [Background technology]

[0002] A hammer drill is capable of linearly reciprocating a tool bit along a drive shaft and rotating the tool bit around the drive shaft. To this end, the hammer drill includes a tool holder that holds the tool bit axially movably, and a cylinder that is connected to the tool holder and can rotate integrally with the tool holder. For example, in the hammer drill disclosed in Patent Document 1, the tool holder and the cylinder are connected and fixed to each other by a connecting pin, with the front end of the cylinder fitted onto the outer periphery of the rear end of the tool holder. The connecting pin is inserted from the radial outside of the cylinder into a hole formed in the cylinder and a hole formed in the tool holder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-144550 Summary of the Invention [Problem to be solved by the invention]

[0004] To connect the tool holder and cylinder of the hammer drill, an assembly worker must insert a connecting pin radially while accurately positioning the tool holder and cylinder holes in the axial and circumferential directions so that the holes in the tool holder and cylinder hole communicate with each other. This makes the process of connecting the tool holder and cylinder complicated.

[0005] In view of the above-mentioned circumstances, one non-limiting object of the present disclosure is to provide a technique that contributes to facilitating the work of connecting a tool holder and a cylinder of a hammer drill. [Means for solving the problem]

[0006] According to one non-limiting aspect of the present disclosure, there is provided a hammer drill including a tool body, a tool holder, a cylinder, and a connecting member. The tool holder is cylindrical and has a longitudinal axis. The tool holder is configured to hold a tool bit movably along the longitudinal axis. The tool holder is supported by the tool body so as to be rotatable about the longitudinal axis. The cylinder extends coaxially with the tool holder and is supported by the tool body so as to be rotatable about the longitudinal axis. The connecting member is interposed between the tool holder and the cylinder in the radial direction of the tool holder, and engages with and connects the tool holder and the cylinder so that the tool holder and the cylinder rotate integrally.

[0007] In the hammer drill of this aspect, a connecting member interposed between the tool holder and the cylinder in the radial direction connects the tool holder and the cylinder so that they can rotate together. This makes it easier to align the tool holder and the cylinder compared to conventional connecting structures using connecting pins. Furthermore, a retaining member or the like required for the connecting pin is not required. This makes it easier and simpler to connect the tool holder and the cylinder so that they can rotate together. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of a hammer drill. [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] 3 is a cross-sectional view taken along line III-III in FIG. 2 (however, only the tool bit, the tool holder, and the second elastic holding portion are shown). [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. 2 (however, only a tool holder, a connecting member, and a cylinder are shown). DETAILED DESCRIPTION OF THE INVENTION

[0009] In one non-limiting embodiment of the present disclosure, the longitudinal axis of the tool holder may define the front-to-rear direction of the hammer drill. The tool holder may have a front end configured to receive a tool bit and a rear end. The rear end of the tool holder may be disposed radially outward of the cylinder and connected to the cylinder via a connecting member. A user of the hammer drill may wish to grip an area closer to the tool bit (the area surrounding the front end of the tool holder) to stabilize their working posture. Therefore, this embodiment is advantageous in that the diameter of the front end of the tool holder can be made smaller than that of the rear end of the tool holder.

[0010] In addition to or instead of the above embodiment, the cylinder may have an air vent. The connecting member may be disposed radially outward of the cylinder. The connecting member may have an air passage communicating with the air vent and configured to ensure air circulation between the internal space of the cylinder and the external space of the cylinder. The air vent of the cylinder may be provided for adjusting the drive timing of the tool accessory or for preventing so-called blank strikes. According to this embodiment, even if the connecting member is disposed in a position that covers the air vent, the air passage can maintain the function of the air vent.

[0011] In addition to or instead of the above embodiment, the connecting member may be configured to position the rear end of the tool holder in the front-rear direction. According to this embodiment, the connecting member can perform not only the function of connecting the tool holder and the cylinder but also the function of positioning the tool holder. Therefore, there is no need to provide a separate structure for positioning the tool holder.

[0012] In addition to or instead of the above embodiment, the hammer drill may further include a bearing arranged on the outer periphery of the overlapping portion. The tool holder and the cylinder may be rotatably supported via the bearing. The overlapping portion refers to a portion (area) where the tool holder, the connecting member, and the cylinder overlap in the radial direction. According to this embodiment, the bearing can stably support the tool holder and the cylinder, which are connected via the connecting member and rotate integrally.

[0013] In addition to or instead of the above embodiment, the connection between the tool holder and the connecting member, and the connection between the cylinder and the connecting member may both be by engagement between a recess and a protrusion. According to this embodiment, torque can be reliably transmitted from the cylinder to the tool holder with a simple configuration. Note that examples of engagement between a recess and a protrusion include engagement between a key groove and a key, spline connection (engagement between internal teeth and external teeth), etc.

[0014] In addition to or instead of the above embodiment, the hammer drill may further include a blank-striking suppression mechanism. The blank-striking suppression mechanism may be disposed on a straight line extending from the connecting member substantially parallel to the longitudinal axis of the tool holder. According to this embodiment, the blank-striking suppression mechanism can be disposed by effectively utilizing the space generated by the connecting member being interposed between the tool holder and the cylinder in the radial direction.

[0015] In addition to or instead of the above embodiment, the blank strike suppression mechanism may include a movable member disposed in front of the connecting member and movable in the front-rear direction relative to the cylinder, and a spring that biases the movable member. The connecting member may be configured to function as a spring seat that receives the rear end of the spring. According to this embodiment, the connecting member can also be effectively used as a spring seat for the spring of the blank strike suppression mechanism, making the blank strike suppression mechanism more compact.

[0016] In addition to or instead of the above embodiment, the connecting member may be made of sintered metal, which can reduce the weight of the connecting member compared to when machined metal parts or molten metal parts are used.

[0017] In addition to or instead of the above embodiment, the hammer drill may further include an impact bolt slidably disposed within the tool holder in the forward / backward direction and configured to strike the tool bit. The connecting member may be disposed rearward of a sliding portion of the tool holder, which is a portion of the tool holder on which the outer circumferential surface of the impact bolt slides. When the connecting member is used to connect the cylinder to the sliding portion of the tool holder with the impact bolt or to a portion of the tool holder forward of the sliding portion (a portion closer to the tool bit), it becomes necessary to dispose the cylinder radially outward of the tool holder and the connecting member. In this case, the diameter of the portion closer to the tool bit, which may be gripped by a user, becomes larger. In contrast, according to this embodiment, it is possible to avoid an increase in the diameter of the portion closer to the tool bit.

[0018] 1 to 4, a hammer drill 1 according to a representative but non-limiting embodiment of the present disclosure will be specifically described below. The hammer drill 1 is a power tool capable of linearly reciprocating a removably attached tool bit 91 along a drive axis DX (hereinafter referred to as an impact operation) and rotating the tool bit 91 around the drive axis DX (hereinafter referred to as a rotation operation). Examples of the tool bit 91 that can be attached to the hammer drill 1 include a hammer bit and a drill bit.

[0019] First, we will explain the general configuration of the hammer drill 1. As shown in Figure 1, the outer shell of the hammer drill 1 is mainly formed by a main body housing 10 and a handle 17 connected to the main body housing 10.

[0020] The main body housing 10 mainly accommodates a tool holder 5 configured to removably hold a tool bit 91, a motor 2, a drive mechanism 3 configured to drive the tool bit 91 in response to the driving of the motor 2, and a vibration suppression mechanism 8. The drive mechanism 3 and the tool holder 5 are accommodated (supported) in an inner housing (also referred to as a tool body) 13 disposed within the main body housing 10.

[0021] The handle 17 includes a grip portion 171 that is gripped by the user. The grip portion 171 extends in a direction intersecting (more specifically, in a direction substantially perpendicular to) the drive axis DX. One end of the grip portion 171 in the longitudinal direction is provided with a switch lever 175 that is pressed by the user. A switch 176 is housed within the grip portion 171. When the switch 176 is turned on in response to pressing of the switch lever 175, the motor 2 starts to be driven, and the tool bit 91 is reciprocated and / or rotated by the drive mechanism 3.

[0022] The elements (configurations) arranged inside the main body housing 10 will be described below. For convenience, in the following description, the extending direction of the drive shaft DX (hereinafter simply referred to as the drive shaft direction) will be defined as the front-rear direction of the hammer drill 1. In the front-rear direction, the side on which the tool holder 5 is arranged will be defined as the front side of the hammer drill 1, and the side on which the grip portion 171 is arranged will be defined as the rear side. Furthermore, the longitudinal direction of the grip portion 171 will be defined as the up-down direction of the hammer drill 1. In the up-down direction, the side on which the switch lever 175 is arranged will be defined as the upper side, and the opposite side will be defined as the lower side. Furthermore, the direction perpendicular to the front-rear direction and the up-down direction will be defined as the left-right direction.

[0023] The tool holder 5 is a cylindrical member having a longitudinal axis LX1. The tool holder 5 is configured to removably receive a portion of the tool bit 91, to linearly slide the tool bit 91 in the direction of extension of the longitudinal axis LX1, and to hold the tool bit 91 non-rotatably relative to the tool holder 5. The tool holder 5 is supported by the inner housing 13 so as to be rotatable about the longitudinal axis LX1. Therefore, the tool bit 91 can rotate integrally with the tool holder 5 about the longitudinal axis LX1. In this manner, the longitudinal axis LX1 of the tool holder 5 defines the drive axis DX of the tool bit 91. The tool holder 5 is housed in a cylindrical front half portion (hereinafter also referred to as a barrel portion 14) of the inner housing 13. The remaining portion of the inner housing 13 (the rear portion of the barrel portion 14; hereinafter also referred to as a gear housing 15) houses the drive mechanism 3.

[0024] A cylinder 6 is connected to the tool holder 5. The cylinder 6 is a cylindrical member and is arranged coaxially with the tool holder 5 inside the inner housing 13. The cylinder 6 is connected to the rear end of the tool holder 5 via a connecting member 7, and the tool holder 5 and the cylinder 6 are rotatable together around the drive axis DX. Details of the tool holder 5 and the cylinder 6 will be described later.

[0025] The motor 2 in this embodiment is a brush motor. The motor 2 is driven by power supplied from an external AC power supply via a power cord (not shown). However, a brushless motor may be used for the motor 2. The motor 2 may also be driven by power supplied from a rechargeable battery. In this embodiment, the motor 2 is disposed so that the rotation axis of the motor shaft 25 intersects with the drive axis DX. However, the motor 2 may also be disposed so that the rotation axis of the motor shaft 25 extends parallel to the drive axis DX.

[0026] The following describes the drive mechanism 3. The drive mechanism 3 is operably connected to the motor 2 (motor shaft 25) and is driven by the power of the motor 2. The drive mechanism 3 of this embodiment includes a motion conversion mechanism 31 and a striking element 33 for striking motion, and a rotation transmission mechanism 37 for rotational motion.

[0027] The motion conversion mechanism 31 is operably connected to the motor 2 and is configured to convert the rotational motion of the motor shaft 25 into linear motion and transmit the linear motion to the striking mechanism 33. In this embodiment, a crank mechanism having a well-known configuration is used as the motion conversion mechanism 31. Briefly, the motion conversion mechanism 31 includes a crankshaft 311, a connecting rod 313, and a piston 315. The crankshaft 311 is operably connected to the motor shaft 25 and is rotated by the motor shaft 25. The crankshaft 311 has an eccentric pin. The connecting rod 313 is operably connected to the eccentric pin and the piston 315. The piston 315 is housed in a cylinder 6 and is slidable within the cylinder 6.

[0028] Instead of such a motion conversion mechanism 31, a well-known mechanism may be employed that uses a member that oscillates in response to the rotation of the rotating body (e.g., a swash bearing, a wobble plate / bearing) to reciprocate the piston.

[0029] The striking element 33 is configured to move linearly and strike the tool bit 91, thereby driving the tool bit 91 linearly along the drive axis DX. In this embodiment, the striking element 33 includes a striker 34 and an impact bolt 35. The striker 34 is disposed in front of the piston 315 in the cylinder 6 and is slidable within the cylinder 6. An air chamber 32 is formed between the striker 34 and the piston 315. The impact bolt 35 is an intermediate element that transmits the kinetic energy of the striker 34 to the tool bit 91. The impact bolt 35 is disposed in front of the striker 34 in the tool holder 5 and is slidable within the tool holder 5.

[0030] When the motor 2 is driven and the piston 315 moves forward, the air in the air chamber 32 is compressed, increasing its pressure. As a result, the striker 34 is pushed forward at high speed and collides with the impact bolt 35, which then transmits kinetic energy to the tool bit 91. As a result, the tool bit 91 moves forward in a straight line along the drive axis DX. On the other hand, when the piston 315 moves rearward, the air in the air chamber 32 expands, decreasing the pressure and drawing the striker 34 rearward. The tool bit 91, pressed against the workpiece, moves rearward. The motion converting mechanism 31 and the striking element 33 repeat these operations.

[0031] The rotation transmission mechanism 37 is operably connected to the motor 2 and configured to transmit the rotational power of the motor shaft 25 to the tool holder 5. The rotation transmission mechanism 37 is a gear reduction mechanism having a known configuration, and the rotational power of the motor 2 is appropriately reduced before being transmitted to the tool holder 5. Simply put, the rotation transmission mechanism 37 includes a small bevel gear 372 provided on an intermediate shaft 371 rotated by the motor shaft 25, and a large bevel gear 374 fixed to the outer periphery of the cylinder 6. When the motor 2 is driven, the rotation transmission mechanism 37 rotates the cylinder 6 and the tool holder 5, and ultimately the tool bit 91 held by the tool holder 5, around the drive axis DX.

[0032] The hammer drill 1 of this embodiment can selectively operate in either an impact-only mode or a rotary impact mode. In the impact-only mode, only the motion conversion mechanism 31 and the impact element 33 are driven, and only an impact operation is performed. In the rotary impact mode, the motion conversion mechanism 31, the impact element 33, and the rotation transmission mechanism 37 are driven, and an impact operation and a rotation operation are performed simultaneously. Any known configuration may be used for switching modes. Therefore, a description of such a configuration will be omitted. However, the hammer drill 1 only needs to be able to selectively perform at least one of an impact operation and a rotation operation, and may have a rotation-only mode in which only a rotation operation is performed in addition to the impact-only mode and the rotary impact mode.

[0033] The tool holder 5 will be described in detail below.

[0034] First, a description will be given of the tool bit (also called a bit) 91 that can be attached to the tool holder 5. As shown in Figures 2 and 3, the tool bit 91 has a shank 911 that is inserted into the tool holder 5. A plurality of angular grooves 913 and a plurality of semicircular grooves 914 are formed on an outer peripheral surface 912 of the shank 911.

[0035] The angular grooves 913 are grooves for transmitting torque and have a generally rectangular or trapezoidal cross section. In this embodiment, three angular grooves 913 are arranged spaced apart from one another in the circumferential direction about the major axis LX2 of the tool bit 91, and each extends substantially parallel to the major axis LX2. The semicircular grooves 914 are grooves for preventing slipout and have a generally semicircular cross section. In this embodiment, two semicircular grooves 914 are arranged at positions opposite each other across the major axis LX2 of the tool bit 91, and each extends substantially parallel to the major axis LX2. The angular grooves 913 and the semicircular grooves 914 are spaced apart from one another in the circumferential direction.

[0036] As shown in FIG. 2, the tool holder 5 is a stepped cylindrical member, and includes a small diameter portion 51, a medium diameter portion 53, and a large diameter portion 55 in this order from the front side.

[0037] The small diameter portion 51 is a portion that receives the shank 911 of the tool bit 91 and slidably holds (contains) the shank 911. For this reason, the inner diameter of the small diameter portion 51 is set to be slightly larger than the outer diameter of the shank 911. The inner peripheral surface 511 of the small diameter portion 51 and the outer peripheral surface 912 of the shank 911 are sliding surfaces that slide against each other.

[0038] The small diameter portion 51 is provided with a plurality of protrusions 513. Each protrusion 513 protrudes radially inward from the inner circumferential surface 511 of the small diameter portion 51 and extends substantially parallel to the major axis LX1 (drive axis DX) of the tool holder 5 (i.e., in the front-to-rear direction). The protrusions 513 are arranged spaced apart from one another in the circumferential direction around the major axis LX1 (drive axis DX) of the tool holder 5. The protrusions 513 are protrusions for transmitting torque, and are arranged at positions in the circumferential direction corresponding to the square groove 913 of the shank 911, and are configured to fit into the square groove 913.

[0039] When the shank 911 is inserted into the small diameter portion 51 with the projection 513 fitted in the square groove 913, the major axis LX2 of the tool bit 91 substantially coincides with the major axis LX1 (drive axis DX) of the tool holder 5. Furthermore, rotation of the tool bit 91 around the drive axis DX relative to the tool holder 5 is restricted, and both side surfaces of the projection 513 and both side surfaces of the square groove 913 each function as a torque transmission surface.

[0040] The small diameter portion 51 is also provided with a plurality of elongated holes 514. Each elongated hole 514 is a through-hole that penetrates the small diameter portion 51 in the radial direction. In this embodiment, the two elongated holes 514 are arranged at positions facing each other across the long axis LX1 and extend substantially parallel to the long axis LX1 (drive axis DX) (i.e., in the front-rear direction). The elongated holes 514 are arranged to face the semicircular grooves 914 of the shank 911 in the radial direction, with the protrusions 513 fitted into the square grooves 913 of the shank 911. A tool retainer 515 for preventing the bit 91 from slipping out is arranged in each of the elongated holes 514. The tool retainer 515 is a generally L-shaped member. The tool retainer 515 is arranged so that a portion of it protrudes radially outward from the small diameter portion 51 and is held within the elongated holes 514 so as to be slidable in the front-rear direction.

[0041] A holding mechanism 57 for the tool retainer 515 is disposed around the tool holder 5. The holding mechanism 57 includes a chuck ring 571, a front spring bearing 573, a rear spring bearing 575, and a spring 577. The chuck ring 571 is a cylindrical member and is fitted around the outer periphery of the small diameter portion 51 so as to surround the front half of the elongated hole 514. The front spring bearing 573 is an annular member and is fitted around the small diameter portion 51 on the rear side of the tool retainer 515. The rear spring bearing 575 is a cylindrical member having a flange portion and is fitted around the rear end portion of the small diameter portion 51. The spring 577 is disposed between the front spring bearing 573 and the rear spring bearing 575 and biases the front spring bearing 573 and the rear spring bearing 575 so as to move away from each other.

[0042] With the above configuration, the rear spring receiver 575 is held in a position where it abuts against the shoulder portion between the small diameter portion 51 and the medium diameter portion 53. Meanwhile, the front spring receiver 573 abuts against the tool retainer 515 from behind and presses the tool retainer 515 forward. The tool retainer 515 is held in a position where it abuts against the chuck ring 571 from behind (hereinafter referred to as the initial position). At this time, the chuck ring 571 restricts the tool retainer 515 from moving forward and radially outward. In addition, a portion of the tool retainer 515 protrudes from the elongated hole 514 into the small diameter portion 51 and fits into the semicircular groove 914, thereby preventing the bit 91 from coming off the tool holder 5.

[0043] A release cover 581 for releasing the bit bit 91 held by the tool retainer 515 is disposed around the tool retainer 515 and the holding mechanism 57. The release cover 581 is a cylindrical member and is supported on the tool holder 5 so as to be movable in the front-to-rear direction. More specifically, a cylindrical cap 583 is fixed around the front end of the tool holder 5. A chuck cover 585 is fitted to the rear side of the cap 583. The chuck cover 585 is a cylindrical member and covers the tool retainer 515 and most of the holding mechanism 57. The release cover 581 is supported by the chuck cover 585 so as to be slidable in the front-to-rear direction. The release cover 581 is urged forward by a spring 577 via a front spring receiver 573.

[0044] When the user moves the release cover 581 rearward, the release cover 581 moves the front spring receiver 573 and the tool retainer 515 rearward against the biasing force of the spring 577. The tool retainer 515 moves rearward within the elongated hole 514, and becomes movable radially outward of the small diameter portion 51. This makes it possible to remove the tool bit 91.

[0045] The medium diameter portion 53 of the tool holder 5 is connected to the rear end of the small diameter portion 51 and extends rearward. The medium diameter portion 53 has larger inner and outer diameters than the small diameter portion 51. The medium diameter portion 53 is a portion that slidably holds (accommodates) the impact bolt 35. The impact bolt 35 includes a large diameter portion 351 and a small diameter portion 353 that extends rearward from the rear end of the large diameter portion 351 and has an outer diameter smaller than that of the large diameter portion 351. The inner diameter of the medium diameter portion 53 is set to be slightly larger than the outer diameter of the large diameter portion 351 of the impact bolt 35. The inner peripheral surface 531 of the medium diameter portion 53 and the outer peripheral surface 352 of the large diameter portion 351 of the impact bolt 35 are sliding surfaces that slide against each other.

[0046] The large diameter portion 55 of the tool holder 5 is connected to the rear end of the medium diameter portion 53 and extends rearward. The large diameter portion 55 has larger inner and outer diameters than the medium diameter portion 53. A portion of the impact bolt 35 is disposed within the large diameter portion 55. The large diameter portion 55 extends to the rear end of the barrel portion 14.

[0047] The cylinder 6 will be described in detail below.

[0048] The cylinder 6 is a cylindrical member having a substantially uniform inner diameter. The outer diameter of the cylinder 6 is smaller than the inner diameter of the large diameter portion 55 of the tool holder 5. As shown in FIG. 1 , the cylinder 6 slidably holds (accommodates) the piston 315 and the striker 34. A portion of the cylinder 6 is disposed within (radially inside) the rear portion of the large diameter portion 55 of the tool holder 5. In this embodiment, substantially the front half of the cylinder 6 is inserted into the rear portion of the large diameter portion 55 of the tool holder 5. Hereinafter, the portion of the cylinder 6 that is disposed within the tool holder 5 will also be referred to as an insertion portion 61.

[0049] As shown in FIGS. 2 and 4, a plurality of ventilation holes 60 are formed in the insertion portion 61. Although the ventilation holes 60 do not actually appear in FIG. 2, for convenience of explanation, the positions of the ventilation holes 60 in the front-rear direction are shown at the bottom of the cylinder 6. Each ventilation hole 60 is a through-hole for circulating air between the internal space of the cylinder 6 and the external space. In this embodiment, each ventilation hole 60 is provided for adjusting the air pressure inside the cylinder 6 (setting the drive timing of the striker 34) and / or suppressing so-called blank strikes. Note that blank strikes refer to the operation of the striking element 33 when the tool bit 91 is not inserted into the tool holder 5 or when the tool bit 91 is not pressed against the workpiece (also referred to as an unloaded state).

[0050] The connecting structure between the tool holder 5 and the cylinder 6 will be described below.

[0051] 2 and 4, a connecting member 7 is disposed between the tool holder 5 and the cylinder 6 in the radial direction so as to be coaxial with the tool holder 5 and the cylinder 6. The tool holder 5 and the cylinder 6 are connected via the connecting member 7. The connecting member 7 is disposed at a position corresponding to the rear end of the tool holder 5 (the rear end of the large diameter portion 55) and approximately the center of the cylinder 6 in the front-rear direction.

[0052] The connecting member 7 engages with the tool holder 5 and the cylinder 6, respectively, and connects the tool holder 5 and the cylinder 6 so that they rotate integrally. More specifically, the connecting member 7 in this embodiment is a single cylindrical member (also referred to as a sleeve or a ring) that is configured to be able to fit onto the inner periphery of the large diameter portion 55 of the tool holder 5 and to be able to fit onto the outer periphery of the cylinder 6. Furthermore, the connection between the connecting member 7 and the large diameter portion 55 of the tool holder 5 for integral rotation, and the connection between the connecting member 7 and the cylinder 6 for integral rotation, are each achieved by engagement between a recessed portion and a protruding portion.

[0053] Specifically, the connecting member 7 is provided with a plurality of outer protrusions 71 that protrude radially outward from its outer peripheral surface, and a plurality of inner protrusions 73 that protrude radially inward from its inner peripheral surface. In this embodiment, four outer protrusions 71 are provided at equal intervals in the circumferential direction. Each outer protrusion 71 has a rectangular or trapezoidal cross section and extends substantially parallel to the drive shaft DX (in the front-rear direction). Similarly, in this embodiment, four inner protrusions 73 are provided at equal intervals in the circumferential direction. The inner protrusions 73 have the same configuration as the outer protrusions 71.

[0054] Meanwhile, four grooves 551 corresponding to the four outer protrusions 71 are provided on the inner peripheral surface of the rear end of the large diameter portion 55 of the tool holder 5. The grooves 551 have a shape that matches the outer protrusions 71 and extend forward from the rear end of the large diameter portion 55 substantially parallel to the drive axis DX. Furthermore, four grooves 63 corresponding to the four inner protrusions 73 are provided on the outer peripheral surface of the insertion portion 61 of the cylinder 6. The grooves 63 have a shape that matches the inner protrusions 73 and extend from the front end of the cylinder 6 substantially parallel to the drive axis DX. The grooves 63 extend over the entire length of the insertion portion 61. A positioning protrusion 64 is provided on the rear side of the rear end of the groove 63. The positioning protrusion 64 protrudes radially outward from the outer peripheral surface of the cylinder 6. A flange portion 75 is provided at the rear end of the connecting member 7.

[0055] When assembling the hammer drill 1, the connecting member 7 is positioned circumferentially relative to the cylinder 6 so that the inner protrusion 73 fits into the groove 63, and is fitted onto the outer periphery of the cylinder 6 from the front. The connecting member 7 is positioned at a position where its rear end (flange portion 75) abuts against the positioning protrusion 64. Furthermore, the tool holder 5 is positioned circumferentially relative to the connecting member 7 so that the outer protrusion 71 fits into the groove 551, and is fitted onto the outer periphery of the connecting member 7 from the front. The tool holder 5 is positioned at a position where its rear end abuts against the flange portion 75 of the connecting member 7. In other words, the connecting member 7 not only functions to connect the tool holder 5 and the cylinder 6, but also to position the tool holder 5. Therefore, there is no need to provide a separate structure for positioning the tool holder 5.

[0056] Through the above procedure, the tool holder 5 and the cylinder 6 are connected via the connecting member 7 so as to be rotatable together. Both side surfaces of the groove 63 of the cylinder 6, both side surfaces of the inner protrusion 73 of the connecting member 7, both side surfaces of the outer protrusion 71, and both side surfaces of the groove 551 of the tool holder 5 each function as torque transmission surfaces.

[0057] When assembling a hammer drill having a conventional connecting structure using a connecting pin, an assembler must accurately align the hole in the tool holder with the hole in the cylinder in the axial and circumferential directions and then insert the connecting pin radially. In addition, a member to prevent the connecting pin from coming out must be placed radially outside the connecting pin. In contrast, with the connecting structure between the tool holder 5 and the cylinder 6 of this embodiment, the assembler only needs to circumferentially align and fit (move backward) the tool holder 5, connecting member 7, and cylinder 6 in that order, as described above. Furthermore, the conventional retaining member is not required. Therefore, compared to the conventional connecting structure using a connecting pin, the work of connecting the tool holder 5 and the cylinder 6 so that they can rotate together can be simplified and facilitated. Furthermore, an increase in the radial size due to the placement of a retaining member can be prevented.

[0058] A user of the hammer drill 1 may wish to grip the front end region of the hammer drill 1, which is closer to the bit bit 91, in order to stabilize their working posture. When attempting to connect the cylinder 6 to the medium diameter portion 53 or a portion forward of the medium diameter portion 53 (a portion closer to the bit bit 91), it becomes necessary to dispose the cylinder 6 radially outward from the tool holder 5 and the connecting member 7. In this case, the diameter of the front end region of the hammer drill 1 becomes larger. In contrast, in this embodiment, the connecting member 7 is disposed at the rear end of the tool holder 5, i.e., rearward of the medium diameter portion 53 in which the impact bolt 35 is slidably accommodated, radially inward from the tool holder 5, and radially outward from the cylinder 6. This is advantageous in that the diameter of the front end of the tool holder 5, and therefore the diameter of the front end region of the hammer drill 1, can be reduced.

[0059] Furthermore, in this embodiment, the connecting member 7 covers some of the ventilation holes 60 of the cylinder 6 from the radial outside. Therefore, multiple ventilation paths 70 are formed on the inner circumferential surface of the connecting member 7. In this embodiment, each ventilation path 70 is connected to the ventilation hole 60 and is configured to allow air to circulate between the internal space of the cylinder 6 and the external space. Specifically, the ventilation paths 70 are formed as grooves extending in the axial direction of the connecting member 7 over the entire length of the connecting member 7 (from the front end to the rear end). Therefore, the ventilation paths 70 also allow air to circulate between the space in front of the connecting member 7 (the external space of the cylinder 6 inside the tool holder 5) and the space behind the connecting member 7 (the external space of the cylinder 6 behind the tool holder 5). Therefore, even when the connecting member 7 is positioned to cover the ventilation holes 60, the ventilation paths 70 maintain the function of the ventilation holes 60.

[0060] The support structure for the tool holder 5 and the cylinder 6 will be described below.

[0061] 1, the tool holder 5 is rotatably supported at two locations, approximately at the center and at the rear end, by a first bearing 131 and a second bearing 132, which are supported by the inner housing 13. More specifically, the first bearing 131 is supported within the front end of the barrel portion 14, and is fitted onto the outer periphery of the medium diameter portion 53 of the tool holder 5. The second bearing 132 is supported within the rear end of the barrel portion 14, and is fitted onto the outer periphery of the rear end of the large diameter portion 55 of the tool holder 5. In other words, the second bearing 132 is fitted onto the outer periphery of a portion where the tool holder 5, the connecting member 7, and the cylinder 6 overlap in the radial direction (hereinafter also referred to as an overlapping portion 567).

[0062] The cylinder 6 is rotatably supported at two locations, approximately the center and the rear end, by a second bearing 132 and a third bearing 133, which are supported by the inner housing 13. That is, in this embodiment, the single second bearing 132 functions as a bearing for both the tool holder 5 and the cylinder 6 at the overlapping portion 567. By supporting the overlapping portion 567, the second bearing 132 can stably support the tool holder 5 and the cylinder 6, which are connected via the connecting member 7 and rotate integrally. The third bearing 133 is supported within the gear housing 15 and fitted onto the outer periphery of a support portion of a large bevel gear 374 fixed to the rear end of the cylinder 6.

[0063] In this embodiment, both the tool holder 5 and the cylinder 6 are machined metal parts (for example, iron parts), while the connecting member 7 is made of sintered metal (a sintered part) to reduce its weight.

[0064] In this embodiment, as described above, the connecting member 7 is interposed between the tool holder 5 and the cylinder 6 in the radial direction. Therefore, as shown in FIG. 2 , a space (gap) exists in front of the connecting member 7 between the inner circumferential surface of the large diameter portion 55 of the tool holder 5 and the outer circumferential surface of the insertion portion 61 of the cylinder 6. Therefore, this space is utilized to arrange the blank strike suppression mechanism 65. It can also be said that the blank strike suppression mechanism 65 is arranged on a straight line extending from the connecting member 7 substantially parallel to the major axis LX1 of the tool holder 5.

[0065] The blank strike suppression mechanism 65 includes a movable sleeve 651 and a biasing spring 653. The movable sleeve 651 is a cylindrical member fitted onto the outer periphery of the front end of the cylinder 6 so as to be slidable in the front-rear direction. The biasing spring 653 is disposed between the movable sleeve 651 and the connecting member 7 in the front-rear direction. The front end of the biasing spring 653 abuts against the movable sleeve 651, and the rear end of the biasing spring 653 abuts against a flange portion 75 of the connecting member 7. In other words, the connecting member 7 (flange portion 75) not only functions to connect the tool holder 5 and the cylinder 6, but also functions as a spring seat for the biasing spring 653. The movable sleeve 651 is biased forward relative to the cylinder 6 by the biasing force of the biasing spring 653, and thus biases the impact bolt 35 forward.

[0066] In an unloaded state where the tool bit 91 is not pushed rearward of the tool holder 5, the movable sleeve 651 is positioned to release air from inside the cylinder 6. This prevents the striker 34 from striking the impact bolt 35 (so-called blank striking).

[0067] The vibration suppression mechanism 8 will now be described.

[0068] The vibration suppression mechanism 8 is a mechanism for reducing the possibility of vibration caused by backlash (unexpected loosening, gap) between the tool holder 5 and the tool bit 91, and is provided around the drive shaft DX. As shown in FIG. 2 , the vibration suppression mechanism 8 of this embodiment includes a first elastic retaining portion 81 and a second elastic retaining portion 82 provided on the small diameter portion 51 of the tool holder 5. The second elastic retaining portion 82 is arranged rearward of the first elastic retaining portion 81 and spaced apart in the front-to-rear direction. Both the first elastic retaining portion 81 and the second elastic retaining portion 82 are configured to elastically hold the shank 911 while applying a biasing force toward the inside in the radial direction of the tool holder 5 to the shank 911 so that the biasing forces acting on the shank 911 are balanced.

[0069] 2 and 3, each of the first elastic retaining portion 81 and the second elastic retaining portion 82 includes three balls 83, three intervening members 84, and one elastic ring 87. The elastic ring 87 of the first elastic retaining portion 81 and the elastic ring 87 of the second elastic retaining portion 82 differ in axial and radial dimensions, but have essentially the same function.

[0070] The balls 83 are held in the small diameter portion 51 so as to be movable in the radial direction of the tool holder 5. More specifically, three holding holes 517 for the balls 83 of the first elastic holding portion 81 are formed in the front part (front side of the elongated hole 514) of the small diameter portion 51 of the tool holder 5. Three holding holes 517 for the balls 83 of the second elastic holding portion 82 are formed in the rear end part (rear side of the elongated hole 514) of the small diameter portion 51 of the tool holder 5.

[0071] The three retaining holes 517 are arranged at the same position in the front-rear direction and at equal intervals in the circumferential direction around the long axis LX1 (drive axis DX). The retaining holes 517 are arranged (offset) so as not to overlap with the above-mentioned protrusions 513 and long holes 514. Each retaining hole 517 extends in the radial direction of the small diameter portion 51 and is a through-hole that connects the internal space of the small diameter portion 51 with the external space. In each of the first elastic retaining portion 81 and the second elastic retaining portion 82, three balls 83 are respectively arranged in the three retaining holes 517 so as to be rollable. The radially inner end of each retaining hole 517 is configured so that the balls 83 do not come out radially inward. In this embodiment, the balls 83 are made of metal (e.g., steel).

[0072] The intervening member 84 is a member configured to rotatably receive (hold) the ball 83, and is interposed between the ball 83 and the elastic ring 87, and is held by the small diameter portion 51 so as to be movable in the radial direction of the tool holder 5. More specifically, the intervening member 84 has a receiving surface 85 configured to generally match a part of the outer circumferential surface (spherical surface) of the ball 83. The intervening member 84 is disposed radially outward of the ball 83 within the retaining hole 517, and is slidable within the retaining hole 517. Note that the intervening member 84 in this embodiment is made of metal (for example, steel).

[0073] The elastic ring 87 is an annular elastic body having uniform inner and outer diameters. The elastic ring 87 is attached to the outer periphery of the small diameter portion 51 so as to cover the three retaining holes 517 in each of the first elastic retaining portion 81 and the second elastic retaining portion 82. The elastic ring 87 is configured to bias the balls 83 radially inward via the intervening member 84. The elastic ring 87 in this embodiment is made of rubber.

[0074] With the above-described configuration, when the shank 911 of the tool bit 91 is not inserted into the small diameter portion 51 of the tool holder 5, the ball 83 is positioned radially innermost within the retaining hole 517 by the biasing force of the elastic ring 87. At this time, a portion of the ball 83 protrudes from the retaining hole 517 into the small diameter portion 51. As the shank 911 is inserted into the small diameter portion 51, the ball 83 abuts against and is pressed against the outer peripheral surface of the shank 911, and moves radially outward together with the intervening member 84 against the biasing force of the elastic ring 87. When the shank 911 is positioned within the small diameter portion 51, the ball 83 is biased radially inward by the elastic ring 87 and is pressed against the shank 911 so as to be rollable relative to the outer peripheral surface of the shank 911 (see FIG. 3 ).

[0075] 2, in this embodiment, the elastic ring 87 of the first elastic retaining portion 81 is held in the front-rear direction between the chuck ring 571 and the chuck cover 585. The elastic ring 87 of the first elastic retaining portion 81 not only functions to bias the balls 83 radially inward, but also functions to absorb impacts in the front-rear direction.

[0076] More specifically, when a so-called blank strike occurs, the bit 91 struck by the impact bolt 35 may move the tool retainer 515 forward at high speed, causing it to collide with the chuck ring 571. The elastic ring 87 can mitigate the impact from the chuck ring 571 to the chuck cover 585 and the cap 583 when the tool retainer 515 collides. Note that the elastic ring 87 is also used in existing hammer drills for the purpose of mitigating such impact. Therefore, by setting the position of the first elastic retaining part 81 in accordance with the position of this elastic ring 87, the first elastic retaining part 81 can be configured without adding any additional parts.

[0077] On the other hand, the elastic ring 87 of the second elastic retaining portion 82 is held by utilizing the holding mechanism 57 of the tool retainer 515 described above. Specifically, an annular holding groove is formed on the inner circumferential surface of the cylindrical portion of the rear spring bearing 575, and the elastic ring 87 is fitted into this groove and held therein. Therefore, although the elastic ring 87 of the second elastic retaining portion 82 has smaller axial and radial dimensions than the elastic ring 87 of the first elastic retaining portion 81, it functions in the same manner as the elastic ring 87. In this way, in this embodiment, a part of the holding mechanism 57 of the tool retainer 515 is effectively used to hold the elastic ring 87 of the second elastic retaining portion 82.

[0078] The operation of the vibration suppression mechanism 8 will now be described.

[0079] When the hammer drill 1 operates in the impact-only mode or the rotary impact mode, the tool bit 91 reciprocates linearly in the front-to-rear direction. At this time, the outer peripheral surface 912 of the shank 911 of the tool bit 91 slides against the inner peripheral surface 511 of the small diameter portion 51 of the tool holder 5. However, due to, for example, a dimensional error, play may occur between the outer peripheral surface 912 of the shank 911 and the inner peripheral surface 511 of the small diameter portion 51. In such a case, when the shank 911 slides back and forth within the small diameter portion 51, the major axis LX2 of the tool bit 91 is tilted (misaligned) with respect to the major axis LX1 of the tool holder 5, causing the shank 911 to collide with the inside of the small diameter portion 51, resulting in vibration and noise.

[0080] In contrast, in this embodiment, the first elastic retaining portion 81 and the second elastic retaining portion 82 provided on the small diameter portion 51 that slides against the shank 911 elastically retain the shank 911 while biasing the shank 911 radially inward so that the biasing forces acting on the shank 911 are balanced. Therefore, even if there is play between the shank 911 and the small diameter portion 51, misalignment can be suppressed. This reduces vibrations caused by the shank 911 colliding with the inside of the small diameter portion 51. Furthermore, the elastic ring 87 can damp vibrations generated in the bit 91. Furthermore, when the hammer drill 1 operates in the rotary impact mode, the rotation axis of the bit 91 can be stabilized.

[0081] In particular, in this embodiment, the first elastic retaining portion 81 and the second elastic retaining portion 82 elastically retain two locations of the shank 911 while biasing them radially inward in the front-to-rear direction. Therefore, the possibility of misalignment can be more reliably reduced compared to when only one of the first elastic retaining portion 81 and the second elastic retaining portion 82 is provided. In addition, the two elastic rings 87 can more effectively damp vibrations generated in the bit 91.

[0082] In this embodiment, in both the first elastic retaining portion 81 and the second elastic retaining portion 82, the three balls 83 are arranged at equal intervals in the circumferential direction so that the biasing force acting on the shank 911 via the three balls 83 from the elastic ring 87 is balanced. This prevents a force from acting in one direction on the tool bit 91 and more reliably reduces the possibility of misalignment. Furthermore, since only one elastic ring 87 is used, the number of parts can be reduced while efficiently biasing the three balls 83 radially inward. Furthermore, the elastic ring 87 can effectively damp vibrations occurring in the tool bit 91 by utilizing the properties of rubber. Furthermore, the interposing member 84 facilitates rotation of the balls 83 and reduces wear on the elastic ring 87 compared to when the rubber elastic ring 87 directly supports the balls 83.

[0083] The correspondence between each component (feature) of the above embodiment and each component (feature) of the present disclosure or invention is shown below. However, each component of the embodiment is merely an example and does not limit each component of the present disclosure or invention.

[0084] The inner housing 13 is an example of a "tool body" according to the present disclosure. The second bearing 132 is an example of a "bearing." The groove 551 and the outer protrusion 71 are an example of a "recess" and a "protrusion," respectively. The groove 63 and the inner protrusion 73 are an example of a "recess" and a "protrusion," respectively. The movable sleeve 651 is an example of a "movable member." The biasing spring 653 is an example of a "spring." The medium diameter portion 53 of the tool holder 5 is an example of a "sliding portion."

[0085] It should be noted that the above embodiment is merely an example, and the hammer drill according to the present disclosure is not limited to the illustrated hammer drill 1. For example, the following modifications can be made. Furthermore, at least one of these modifications can be adopted in combination with the hammer drill 1 illustrated in the embodiment and at least one of the features described in each claim.

[0086] The connection structure of the tool holder 5 and the cylinder 6 via the connecting member 7 can be modified as appropriate, as long as the connecting member 7 is disposed between the tool holder 5 and the cylinder 6 in the radial direction and connects them so that they can rotate integrally. For example, the shapes, numbers, and arrangements of the grooves 551, 63, the outer protrusion 71, and the inner protrusion 73 can be modified as desired. Furthermore, contrary to the embodiment, the tool holder 5 and the connecting member 7 may be connected by engagement between a protrusion provided on the inner circumferential surface of the tool holder 5 and a groove provided on the outer circumferential surface of the connecting member 7. The connection between the cylinder 6 and the connecting member 7 can also be modified in a similar manner.

[0087] The configuration of the tool holder 5 and the elements arranged therein may be changed as appropriate. For example, the shape, number, and arrangement of the protrusions 513 and the elongated holes 514 of the tool holder 5 are merely examples and may be changed as appropriate depending on the engagement structure with the tool bit 91. The vibration suppression mechanism 8 may also be omitted. The same applies to the configuration of the cylinder 6 and the elements arranged therein. For example, the shape, number, and arrangement of the vent holes 60 in the cylinder 6 and the configuration and arrangement of the blank strike suppression mechanism 65 may be changed as appropriate. These elements may also be omitted.

[0088] In view of the spirit of the present invention and the above-described embodiments, the following aspects are constructed, and at least one of the following aspects may be adopted in combination with the features of the embodiments and their variants, or at least one of the features described in each claim. [Aspect 1] The connecting member is a single cylindrical member (sleeve, ring). [Aspect 2] The air passage is a groove formed on the inner peripheral surface of the connecting member and extending over the entire length of the connecting member in the axial direction. [Aspect 3] One end of the ventilation passage opens into a space formed inside the tool holder and outside the cylinder, and the other end of the ventilation passage opens into a space outside the tool holder and the cylinder. [Aspect 4] the long axis defines a front-to-rear direction of the hammer drill; The hammer drill is a first bearing that rotatably supports the front end portion of the tool holder; a second bearing that rotatably supports an overlapping portion where the rear end portion of the tool holder, the connecting member, and the cylinder overlap in the radial direction; The cylinder further includes a third bearing that rotatably supports the rear end of the cylinder. [Aspect 5] Hammer drills are a motor having a motor shaft; a piston slidably received in the cylinder along the longitudinal axis, the piston operatively coupled to the motor shaft and configured to reciprocate along the longitudinal axis in response to rotation of the motor shaft; a striker that is slidably housed in the cylinder along the longitudinal axis and that is configured to reciprocate in response to the reciprocating movement of the piston; an impact bolt that is accommodated in the tool holder so as to be slidable along the longitudinal axis and that is configured to strike the tool bit in response to impact by the striker; a plurality of gears operably coupled to the motor shaft and configured to rotate the tool holder in response to rotation of the motor shaft. [Explanation of symbols]

[0089] 1: hammer drill, 10: main body housing, 13: inner housing, 131: first bearing, 132: second bearing, 133: third bearing, 14: barrel portion, 15: gear housing, 17: handle, 171: grip portion, 175: switch lever, 176: switch, 2: motor, 25: motor shaft, 3: drive mechanism, 31: motion conversion mechanism, 311: crankshaft, 313: connecting rod , 315: piston, 32: air chamber, 33: striking element, 34: striker, 35: impact bolt, 351: large diameter portion, 352: outer peripheral surface, 353: small diameter portion, 37: rotation transmission mechanism, 371: intermediate shaft, 372: small bevel gear, 374: large bevel gear, 5: tool holder, 51: small diameter portion, 511: inner peripheral surface, 513: protrusion, 514: elongated hole, 515: tool retainer, 517: retaining hole, 5 3: Medium diameter portion, 531: Inner surface, 55: Large diameter portion, 551: Groove, 567: Overlapping portion, 57: Retaining mechanism, 571: Chuck ring, 573: Front spring holder, 575: Rear spring holder, 577: Spring, 581: Release cover, 583: Cap, 585: Chuck cover, 6: Cylinder, 60: Ventilation hole, 61: Insertion portion, 63: Groove, 64: Positioning protrusion, 65: Blank strike prevention mechanism, 651: Movable sleeve , 653: biasing spring, 7: connecting member, 70: ventilation passage, 71: outer protrusion, 73: inner protrusion, 75: flange portion, 8: vibration suppression mechanism, 81: first elastic retaining portion, 82: second elastic retaining portion, 83: ball, 84: interposing member, 85: receiving surface, 87: elastic ring, 91: tip tool, 911: shank, 912: outer peripheral surface, 913: square groove, 914: semicircular groove, DX: drive shaft, LX1: long shaft, LX2: long shaft

Claims

1. A tool body, a cylindrical tool holder having a long axis, configured to hold a tool bit movably along the long axis and supported by the tool body rotatably about the long axis; a cylinder extending coaxially with the tool holder and supported by the tool body so as to be rotatable about the longitudinal axis; a connecting member that is interposed between the tool holder and the cylinder in the radial direction of the tool holder and that engages with and connects the tool holder and the cylinder so that the tool holder and the cylinder rotate integrally, the connecting member is a cylindrical member, The hammer drill, wherein the connection between the tool holder and the connecting member, and the connection between the cylinder and the connecting member are both achieved by engagement between a recess and a protrusion.

2. A hammer drill as claimed in claim 1, the connecting member is (i) connected to the tool holder by engagement between a portion of an outer periphery of the connecting member and a portion of an inner periphery of the tool holder, and (ii) connected to the cylinder by engagement between a portion of the inner periphery of the connecting member and a portion of an outer periphery of the cylinder.

3. 2. The hammer drill according to claim 1, the long axis defines a front-to-rear direction of the hammer drill; the tool holder has a front end configured to receive the tool bit and a rear end; The hammer drill, wherein the rear end of the tool holder is disposed radially outside the cylinder and is connected to the cylinder via the connecting member.

4. 4. The hammer drill according to claim 3, the cylinder has a vent configured to adjust air pressure inside the cylinder; the connecting member is disposed radially outward of the cylinder, The connecting member has an air passage that communicates with the air vent hole and is configured to ensure air circulation between the internal space of the cylinder and the external space of the cylinder.

5. 4. The hammer drill according to claim 3, The hammer drill, wherein the connecting member is configured to position the rear end of the tool holder in the front-rear direction.

6. 2. The hammer drill according to claim 1, a bearing disposed on an outer periphery of an overlapping portion where the tool holder, the connecting member, and the cylinder overlap in the radial direction, The hammer drill is characterized in that the tool holder and the cylinder are rotatably supported via the bearing.

7. The hammer drill according to any one of claims 1 to 6, The hammer drill further includes a blank strike suppression mechanism disposed on a straight line extending from the connecting member substantially parallel to the longitudinal axis.

8. 8. The hammer drill according to claim 7, the long axis defines a front-to-rear direction of the hammer drill; the blank strike suppression mechanism is disposed in front of the connecting member and includes a movable member movable in the front-rear direction relative to the cylinder, and a spring that biases the movable member; The hammer drill is characterized in that the connecting member is configured to function as a spring seat that receives a rear end of the spring.

9. 2. The hammer drill according to claim 1, The hammer drill is characterized in that the connecting member is made of sintered metal.

10. 2. The hammer drill according to claim 1, the long axis defines a front-to-rear direction of the hammer drill; an impact bolt disposed within the tool holder so as to be slidable in a front-rear direction and configured to strike the tool bit; The hammer drill is characterized in that the connecting member is disposed rearward of a sliding portion of the tool holder, which is a portion on which an outer peripheral surface of the impact bolt slides.

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