Work machine and manufacturing method for spindle used in work machine

Abstract

The present invention improves durability and processability. In a carrier part 43 of a spindle 41 in an impact tool 1, a corner part 46C of a plate connection part 46 is chamfered. In this way it is possible to inhibit the occurrence of a stress concentration in the corner part 46C, and to improve the durability of the impact tool 1. Additionally, a chamfering hole 47 having the depth direction in the front-rear direction is formed from the rear surface of a rear-side carrier plate 44 to the rear part of a front-side carrier plate 45. Further, when viewed from the front-rear direction, a portion of the inner peripheral surface of the chamfering hole 47 and the corner part 46C overlap. In this way it is possible, by using a drill to carry out a hole-drilling process (cutting process) on the carrier part 43 starting from the rear side, to chamfer the corner part 46C across the entirety of the plate connection part 46 in the thickness direction.

Description

Working machine and method for manufacturing spindle used in working machine

[0001] The present invention relates to a work machine and a method for manufacturing a spindle used in the work machine.

[0002] In the work machine described in Patent Document 1 below, the driving force of a motor is transmitted to an impact mechanism by a reducer consisting of a planetary gear mechanism, and a rotational force and an impact force are applied to a tool tip such as a driver bit attached to the impact mechanism. This impact mechanism is composed of a spindle that rotates by the driving force of the motor, a hammer connected to the spindle by a cam mechanism, and an anvil connected to the hammer by the striking claw of the hammer so as to rotate integrally with the hammer.

[0003] The spindle also rotatably supports an idle gear that constitutes a reduction mechanism. Specifically, the spindle has a shaft portion and a pair of disk-shaped wall portions that extend radially outward from the shaft portion, with the outer peripheries of the pair of wall portions connected by a connecting portion. The idle gear is housed between the pair of wall portions.

[0004] Japanese Patent Application Laid-Open No. 2018-86723

[0005] In some spindles, depending on the number of idle gears accommodated, the connecting portion connecting the pair of wall portions may be formed in a generally fan-shaped configuration with the radially inner end at its center when viewed from the axial direction. That is, when viewed from the axial direction, the connecting portion has a corner that protrudes toward the axis of the spindle. For this reason, stress concentration occurs at the corner, and if the connecting portion breaks, the durability of the spindle (work machine) may be reduced.

[0006] On the other hand, by chamfering the corners, it is possible to prevent stress concentration at the corners. In this case, it is necessary to chamfer the corners of the connecting part located between the pair of walls, which may reduce the workability of the spindle. For this reason, it is desirable for a work machine using a spindle to have a structure that can improve durability and workability.

[0007] In consideration of the above, an object of the present invention is to provide a work machine that can improve durability and workability, and a method for manufacturing a spindle used in the work machine.

[0008] One or more embodiments of the present invention are a work machine including: a motor; a spindle that rotates by the driving force of the motor; and a tool holder that holds a tool and is driven by the rotational force of the spindle, wherein the spindle includes a shaft portion, a first wall portion that extends radially outward from the shaft portion; a second wall portion that extends radially outward from the shaft portion and is positioned opposite the first wall portion in the axial direction of the shaft portion; a connecting portion that connects the first wall portion and the second wall portion radially outward of the shaft portion and between the first wall portion and the second wall portion, and has a chamfered corner that is convex toward the shaft portion when viewed from the axial direction; and a chamfering hole that is formed from one of the first wall portion and the second wall portion to the other of the first wall portion and the second wall portion with its depth direction aligned with the corner when viewed from the axial direction.

[0009] One or more embodiments of the present invention are a work machine in which the chamfering hole penetrates one of the first wall portion and the second wall portion, and the chamfering hole formed in the other of the first wall portion and the second wall portion is formed in a concave shape that opens into one of the first wall portion and the second wall portion.

[0010] One or more embodiments of the present invention are directed to a work implement in which the chamfering hole penetrates the first wall and the second wall.

[0011] One or more embodiments of the present invention are directed to a work machine in which the chamfering hole is formed in a circular shape when viewed from the axial direction.

[0012] One or more embodiments of the present invention are directed to a work machine in which the chamfering hole is formed as an elongated hole with a longitudinal direction that is the circumferential direction of the spindle when viewed from the axial direction.

[0013] In one or more embodiments of the present invention, the connecting portion is configured to include a pair of side surfaces that, when viewed from the axial direction, extend in a direction approaching each other as they move radially inward of the shaft portion, and a corner portion formed at the portion where the pair of side surfaces intersect, and a root R portion is formed at the boundary between the side surfaces and the inner surfaces of the first wall portion and the second wall portion.

[0014] One or more embodiments of the present invention are directed to a work machine in which a portion of the chamfering hole overlaps with the shaft portion when viewed in the axial direction.

[0015] One or more embodiments of the present invention are a work machine in which the bit is located on one axial side of the spindle, the second wall portion is disposed on one axial side of the first wall portion, and a thick-walled portion is provided on the second wall portion, and the thick-walled portion overlaps the corner portion when viewed from the axial direction.

[0016] One or more embodiments of the present invention are a work machine in which three connecting portions are provided between the first wall portion and the second wall portion, and the connecting portions are arranged at equal intervals around the shaft portion.

[0017] One or more embodiments of the present invention are a work machine in which three transmission members that transmit the driving force of the motor are arranged between the first wall portion and the second wall portion, and when viewed from the axial direction, the chamfering hole portion is arranged adjacent to the radially inner side of the shaft portion relative to the corner portion, and the transmission members and the connecting portion are arranged alternately in the circumferential direction of the shaft portion.

[0018] One or more embodiments of the present invention are a method for manufacturing a spindle used in a work machine, the spindle including a shaft portion, a first wall portion extending radially outward from the shaft portion, a second wall portion extending radially outward from the shaft portion and disposed opposite the first wall portion in an axial direction of the shaft portion, a connecting portion that connects the first wall portion and the second wall portion radially outward of the shaft portion and between the first wall portion and the second wall portion and has a chamfered corner, and a front wall portion formed in the first wall portion and the second wall portion with a depth direction aligned with the axial direction. The method for manufacturing a spindle includes a first step of forming the shaft portion and a protrusion extending radially outward from the shaft portion, the protrusion including a chamfering hole portion, a part of the inner surface of which coincides with the corner portion when viewed from the axial direction, a second step of cutting the protrusion from the radially outward side with an end mill to form the first wall portion, the second wall portion, and the connecting portion on the protrusion, and a third step of cutting the protrusion from one side or the other in the axial direction with a drill or an end mill to form the chamfering hole portion and chamfer the corner portion.

[0019] One or more embodiments of the present invention may provide improved durability and processability.

[0020] 3(B) is a longitudinal cross-sectional view showing an impact tool according to the present embodiment; FIG. 3(A) is a longitudinal cross-sectional view showing an enlarged view of the upper part of the impact tool shown in FIG. 1; FIG. 3(A) is a side view of the spindle shown in FIG. 2 as seen from the right side, and FIG. 3(B) is a cross-sectional view (cross-sectional view along line 3B-3B in FIG. 3(A)) showing the interior of the carrier part of the spindle shown in FIG. 3(A) as seen from the front side; FIG. 3(B) is a perspective view of the rear part of the carrier part in a broken state shown in FIG. 3(B) as seen from the diagonally front right; FIG. 3(B) is a cross-sectional view of the lower plate connecting part and the chamfering hole part as seen from the right side; FIG. 3(B) is a perspective view corresponding to FIG. 4 showing the rear part of the carrier part of a spindle of a comparative example; FIG. 3(B) is a cross-sectional view corresponding to FIG. 5 showing a modified example of the chamfering hole part shown in FIG. 5; FIG. 3(B) is a cross-sectional view corresponding to FIG. 3(B) showing another modified example of the chamfering hole part shown in FIG. 5;

[0021] An impact tool 1 as a work machine according to this embodiment will be described below with reference to the drawings. Note that arrows UP, FR, and RH shown as appropriate in the drawings respectively indicate the upper side, front side, and right side of the impact tool 1. In the following description, when the up-down, front-rear, and left-right directions are used, they refer to the up-down, front-rear, and left-right directions of the impact tool 1 unless otherwise specified.

[0022] As shown in Figures 1 and 2, the impact tool 1 is configured as an electric tool that applies rotational force and impact force to a tip tool 70, such as a driver bit, attached to the front end of the impact tool 1 to perform fastening processing, etc.

[0023] The impact tool 1 includes a housing 10 that forms the outer shell of the impact tool 1, a motor 20 housed in the housing 10, and a driving force transmission mechanism 30 that transmits the driving force of the motor 20 to the tool bit 70. Each component of the impact tool 1 will be described below.

[0024] (Regarding the Housing 10) The housing 10 is formed into a hollow, generally I-shape when viewed from the right side. Specifically, the housing 10 includes an upper housing portion 10A that forms the upper end of the housing 10 and extends in the front-to-rear direction, a handle portion 10B that extends downward from a central portion of the upper housing portion 10A in the front-to-rear direction, and a lower housing portion 10C that forms the lower end of the housing 10. The housing 10 is composed of multiple housing members that are assembled together to form the housing 10.

[0025] A trigger 12 is provided at the upper end of the handle portion 10B, and the trigger 12 protrudes forward from the handle portion 10B and can be pulled rearward. A switch mechanism 14 is provided on the handle portion 10B behind the trigger 12. The switch mechanism 14 has a switch (not shown), and pulling the trigger 12 switches the switch from off to on.

[0026] A controller 16 is provided in the lower housing portion 10C. A switch of the switch mechanism 14 is electrically connected to the controller 16, and an output signal corresponding to the operation state of the trigger 12 is output from the switch to the controller 16. A battery 18 is also detachably attached to the lower housing portion 10C. The battery 18 is electrically connected to the controller 16, and supplies power to a motor 20, which will be described later.

[0027] (Regarding the Motor 20) The motor 20 is housed in the rear end of the upper housing portion 10A and is electrically connected to the controller 16. The motor 20 includes a drive shaft 21 whose axial direction is the front-to-rear direction, a rotor 22 connected to the drive shaft 21 so as to be rotatable integrally therewith, and a substantially cylindrical stator 23 disposed radially outward of the rotor 22.

[0028] The rear end of the drive shaft 21 is rotatably supported by a first motor bearing 24 fixed to the housing 10. Meanwhile, the front end portion of the drive shaft 21 is rotatably supported by a second motor bearing 26, which is fixed to a gear case 25 housed in the upper housing portion 10A. The gear case 25 is formed in a generally stepped cylindrical shape with its axial direction extending in the front-to-rear direction, and the second motor bearing 26 is fitted into approximately the center of the gear case 25. The front end of the drive shaft 21 is disposed within the gear case 25, protruding forward from the second motor bearing 26.

[0029] (Regarding the driving force transmission mechanism 30) The driving force transmission mechanism 30 is composed of a rotary impact mechanism 40 that imparts a rotational force and an impact force to the tip tool 70, and a reduction mechanism 32 that decelerates the rotational force of the motor 20 and transmits it to the rotary impact mechanism 40.

[0030] (Regarding the reduction mechanism 32) The reduction mechanism 32 is configured as a planetary gear mechanism and is disposed inside the gear case 25. Specifically, the reduction mechanism 32 includes a sun gear 33 fixed to the front end of the drive shaft 21 of the motor 20, a ring-shaped ring gear 34 provided radially outward of the sun gear 33, and a plurality of (three in this embodiment) idle gears 35 serving as transmission members provided between the sun gear 33 and the ring gear 34.

[0031] The ring gear 34 is held in the gear case 25 via a damper, and internal teeth are formed on the inner peripheral surface of the ring gear 34. The idle gear 35 is rotatably mounted on a carrier portion 43, which serves as a protrusion of the spindle 41 (described later). Specifically, the idle gear 35 is housed in a gear chamber 43A (see FIG. 3A ) formed in the carrier portion 43 and is rotatably supported by needle rollers 36 provided in the gear chamber 43A, with the front-to-rear direction as the axial direction. The idle gear 35 is also meshed with the internal teeth of the sun gear 33 and the ring gear 34. As a result, when the sun gear 33 rotates, the idle gear 35 rotates about the axis of the needle rollers 36 while revolving about the axis of the sun gear 33, thereby rotating the spindle 41. In other words, the rotational force of the motor 20, reduced by the reduction mechanism 32, is transmitted to the spindle 41, and the rotary impact mechanism 40 is activated.

[0032] (Regarding the Rotary Impact Mechanism 40) The rotary impact mechanism 40 includes a spindle 41, a hammer 50, and an anvil 56 serving as a tool holder.

[0033] 3A and 3B , the spindle 41 has a spindle shaft 42 as a substantially cylindrical shaft portion whose axial direction is the front-to-rear direction, and the spindle shaft 42 is arranged coaxially with the drive shaft 21 of the motor 20. Specifically, the sun gear 33 described above is inserted into the rear end portion of the spindle shaft 42, and the rear end portion of the spindle shaft 42 is rotatably supported by a bearing 60 provided in the gear case 25. A carrier portion 43 extending radially outward from the spindle shaft 42 is provided on the rear end side of the outer periphery of the spindle shaft 42, and the idle gear 35 described above is rotatably provided on the carrier portion 43. The configuration of the carrier portion 43 will be described later.

[0034] The portion of the spindle shaft 42 rearward of the carrier portion 43 is designated as a rear shaft portion 42A (broadly speaking, this is an element that can be understood as a first shaft portion), and the portion of the spindle shaft 42 forward of the carrier portion 43 is designated as a front shaft portion 42B (broadly speaking, this is an element that can be understood as a second shaft portion). The outer diameter of the rear shaft portion 42A is set slightly smaller than the outer diameter of the front shaft portion 42B. A pair of spindle cam grooves 42C is formed on the outer peripheral surface of the front portion of the front shaft portion 42B. When viewed from the radially outer side of the front shaft portion 42B, the pair of spindle cam grooves 42C extend in a generally V-shape. When viewed in cross section from the longitudinal direction, the spindle cam groove 42C is formed in a generally semicircular shape that opens radially outward of the front shaft portion 42B. A steel ball 52 is rotatably inserted into the front end of the spindle cam groove 42C.

[0035] 2, the hammer 50 is formed in a generally cylindrical shape with its axial direction extending in the front-to-rear direction, and an insertion hole 50A extends in the front-to-rear direction through the center of the hammer 50. The front portion of the front shaft portion 42B of the spindle shaft 42 is inserted into the insertion hole 50A, and the hammer 50 is rotatably supported by the spindle 41.

[0036] A pair of hammer cam grooves 50B are formed on the inner peripheral surface of the insertion hole 50A of the hammer 50. The hammer cam grooves 50B extend along the circumferential direction of the hammer 50 when viewed from the front, and are open toward the front. The rear end of the hammer cam groove 50B is formed in a generally V-shape that is open toward the front when viewed from the radially inside of the hammer 50. The pair of hammer cam grooves 50B are arranged 180 degrees apart in the circumferential direction of the hammer 50. A steel ball 52 is rotatably inserted into the hammer cam groove 50B, and is located at the rear end of the hammer cam groove 50B.

[0037] A rearward-opening housing groove 50D is formed in the radially intermediate portion of the rear surface of the hammer 50. The housing groove 50D extends circumferentially around the entire circumference of the hammer 50. A hammer spring 54, configured as a compression spring, is housed in the housing groove 50D, and the hammer spring 54 biases the hammer 50 forward. As a result, the steel ball 52 is held within the front end of the spindle cam groove 42C and the rear end of the hammer cam groove 50B, connecting the hammer 50 and spindle 41 so that they can rotate together. When the rotary impact mechanism 40 is activated, the steel ball 52 rolls within the spindle cam groove 42C and the hammer cam groove 50B, causing the hammer 50 to rotate relative to the spindle 41 and move in the forward-backward direction. The rear end of the hammer spring 54 is locked by a locking plate 62 disposed between the spindle 41 and the hammer 50.

[0038] A plurality of hammer claws 50E (three in this embodiment) are integrally provided on the front surface (one axial end surface) of the hammer 50. The thickness direction of each hammer claw 50E is the front-to-rear direction, and each hammer claw 50E is formed in the shape of a generally sector-shaped block that protrudes radially inward of the hammer 50 when viewed from the front, and protrudes forward from the hammer 50. The hammer claws 50E are arranged at equal intervals (every 120 degrees) around the circumference of the hammer 50.

[0039] The anvil 56 is formed in a generally stepped cylindrical shape that is open to the front, and is disposed in front of the hammer 50. Specifically, a connecting shaft 56A having a smaller diameter than the remaining portions is formed at the rear end of the anvil 56, and the connecting shaft 56A is rotatably inserted into the front end of the spindle shaft 42. A longitudinally intermediate portion of the anvil 56 is rotatably held by a sleeve 58 that is held at the front end of the upper housing portion 10A. The tool bit 70 is attached inside the anvil 56 from the front side so as to be immovable relative to the anvil 56.

[0040] Three anvil claws 56B are provided on the outer periphery of the rear end portion of the anvil 56. The anvil claws 56B are formed in a generally rectangular plate shape with the thickness direction in the front-to-rear direction and protrude radially outward from the anvil 56. The anvil claws 56B are arranged at equal intervals (every 120 degrees) around the circumference of the anvil 56 and are also arranged between the hammer claws 50E of the hammer 50. In other words, the hammer claws 50E and the anvil claws 56B are arranged alternately around the circumference of the hammer 50 in a front view.

[0041] When the hammer 50 rotates, the side of the hammer claw 50E abuts against the side of the anvil claw 56B adjacent to it in the rotational direction, and the hammer claw 50E and the anvil claw 56B engage in the circumferential direction of the hammer 50. As a result, a rotational force is applied from the hammer 50 to the anvil 56, causing the anvil 56 to rotate together with the tool bit 70. When the rotational force (torque) for rotating the tool bit 70 exceeds a predetermined value, the hammer 50 moves rearward relative to the anvil 56 so that the hammer claw 50E gets over the anvil claw 56B. When the hammer claw 50E gets over the anvil claw 56B, the hammer 50 rotates relative to the anvil 56, and the hammer claw 50E strikes the adjacent anvil claw 56B, thereby applying a striking force from the hammer 50 to the anvil 56.

[0042] (Regarding the carrier portion 43 of the spindle 41) As shown in Figures 2 to 5, the carrier portion 43 is composed of a rear carrier plate 44 as a first wall portion, a front carrier plate 45 as a second wall portion, plate connecting portions 46 as connecting portions at three locations, and chamfering hole portions 47.

[0043] The rear carrier plate 44 is formed in a generally circular plate shape with its thickness direction in the front-to-rear direction and protrudes radially outward from the front end of the rear shaft portion 42A. Like the rear carrier plate 44, the front carrier plate 45 is formed in a generally circular plate shape with its thickness direction in the front-to-rear direction and protrudes radially outward from the rear end of the front shaft portion 42B. Thus, the rear carrier plate 44 and the front carrier plate 45 are disposed opposite each other with a predetermined gap in the front-to-rear direction, and the space between the rear carrier plate 44 and the front carrier plate 45 forms a gear chamber 43A for accommodating the idle gear 35. The spindle shaft 42 is not provided within this gear chamber 43A. The rear shaft portion 42A and the front shaft portion 42B are separated into front and rear portions by the carrier portion 43, and the interior of the gear chamber 43A is connected to the interiors of the rear shaft portion 42A and the front shaft portion 42B.

[0044] The outer diameter of the rear carrier plate 44 and the outer diameter of the front carrier plate 45 are approximately the same. A thick portion 45A is formed on the radially inner portion of the front surface of the front carrier plate 45, and the plate thickness of the thick portion 45A of the front carrier plate 45 is set to be thicker than the plate thickness of other portions. Furthermore, the plate thickness of the thick portion 45A of the front carrier plate 45 is set to be slightly thicker than the plate thickness of the rear carrier plate 44.

[0045] The plate connecting portion 46 is disposed between the outer periphery of the rear carrier plate 44 and the outer periphery of the front carrier plate 45 to connect them. The thickness direction of the plate connecting portion 46 is the front-to-rear direction, and the plate connecting portion 46 is formed in a generally sector-shaped block shape that protrudes radially inward of the spindle 41 in a front view. Specifically, the plate connecting portion 46 includes a pair of inclined surfaces 46A that form side surfaces of the plate connecting portion 46 on both sides of the spindle 41 in the circumferential direction, and an outer surface 46B that forms a side surface of the plate connecting portion 46 on the radially outer side of the spindle 41. The outer surface 46B is disposed flush with the outer periphery of the rear carrier plate 44 and the outer periphery of the front carrier plate 45. The inclined surfaces 46A are inclined in directions approaching each other as they extend radially inward of the spindle 41 in a front view. Furthermore, the angle between the pair of inclined surfaces 46A is set to an acute angle in a front view. The intersection of the pair of inclined surfaces 46A forms an acute corner 46C. The corner 46C is a chamfered corner, and the inner peripheral surface of a chamfering hole 47 (described later) is flush with the corner 46C. That is, the corner 46C is not a so-called pin angle (a corner formed only by a line) but is formed as a corner formed by a curved surface. When viewed from the front-rear direction, the corner 46C overlaps the thick portion 45A of the front carrier plate 45. In addition, a root rounded portion 46D is formed at the boundary between the inclined surface 46A and the inner peripheral surfaces of the rear carrier plate 44 and the front carrier plate 45. That is, the root rounded portion 46D is formed by an arc-shaped surface, and the inclined surface 46A and the inner peripheral surfaces of the rear carrier plate 44 and the front carrier plate 45 are smoothly connected by the root rounded portion 46D.

[0046] Three support holes 48 are formed through the rear carrier plate 44 and the front carrier plate 45 in the front-rear direction. The support holes 48 are arranged between circumferentially adjacent plate connecting portions 46 and are arranged at equal intervals around the circumferential direction of the spindle 41. Both front-rear end portions of the needle rollers 36 are fitted into the support holes 48, and the needle rollers 36 are supported by the carrier portions 43. As a result, the idle gears 35 supported by the needle rollers 36 are housed in the gear chamber 43A and are arranged between circumferentially adjacent plate connecting portions 46. In other words, the idle gears 35 and the plate connecting portions 46 are arranged alternately around the circumferential direction of the spindle 41.

[0047] The chamfering hole 47 is a hole whose depth direction is the front-rear direction. The chamfering hole 47 is formed in a circular shape when viewed in the front-rear direction, and is formed from the rear surface of the rear carrier plate 44 to the rear part of the front carrier plate 45. In other words, the chamfering hole 47 is a hole that penetrates the rear carrier plate 44 in the front-rear direction, and is configured as a concave stop hole that opens to the rear side of the front carrier plate 45.

[0048] The chamfering hole 47 is disposed adjacent to the plate connecting portion 46 on the radially inner side of the spindle 41, as viewed from the front-rear direction, and a portion of the chamfering hole 47 overlaps with the pre-chamfered corner 46C of the plate connecting portion 46. That is, as will be described in detail later, the carrier portion 43 is drilled from the rear side using a cutting tool such as a drill to form the chamfering hole 47 in the rear carrier plate 44 and the front carrier plate 45, thereby chamfering the corner 46C of the plate connecting portion 46. As a result, as viewed from the front-rear direction, a portion of the inner circumferential surface of the chamfering hole 47 coincides with the corner 46C. In other words, the inner circumferential surface of the chamfering hole 47 is flush with the corner 46C. Furthermore, as viewed from the front-rear direction, a portion of the chamfering hole 47 overlaps with the outer periphery of the front shaft portion 42B of the spindle shaft 42.

[0049] (Regarding the manufacturing method of the spindle 41) In the manufacturing method of the spindle 41, the first step is to form the spindle shaft 42 and the carrier portion 43 that extends radially outward from the spindle shaft 42 and does not have a gear chamber 43A by casting, cutting, etc. (see the carrier portion 43 shown by the dotted line in Figure 3 (A)).

[0050] Next, as a second step, as shown in FIG. 3A , an end mill EM is used to cut the front-rear middle portion of the carrier portion 43 from the radially outer side to form the rear carrier plate 44, the front carrier plate 45, and the plate connecting portion 46 in the carrier portion 43 (second step). In this case, the insertion direction of the end mill EM into the carrier portion 43 is appropriately changed to perform the cutting process on the carrier portion 43. As a result, a gear chamber 43A is formed between the rear carrier plate 44 and the front carrier plate 45. Note that in the second step, a root rounded portion 46D is formed between the inclined surface 46A of the plate connecting portion 46 and the inner circumferential surfaces of the rear carrier plate 44 and the front carrier plate 45, but the corners 46C of the plate connecting portion 46 are not chamfered (see the radially inner end of the plate connecting portion 46 indicated by the two-dot chain line in FIG. 3B ).

[0051] Next, as a third step, as shown in FIG. 5 , a drill DR is used to drill holes in the carrier portion 43, forming chamfering holes 47 in the carrier portion 43 and chamfering the corners 46C of the plate connecting portion 46 (third step). Specifically, the drill DR is used to cut the rear carrier plate 44 of the carrier portion 43 from the rear side, penetrating the rear carrier plate 44 to form the chamfering holes 47. Next, the corners 46C of the plate connecting portion 46 of the carrier portion 43 are cut to chamfer the corners 46C. Next, the front carrier plate 45 of the carrier portion 43 is cut from the rear side to form the concave chamfering holes 47. This chamfers the corners 46C throughout the entire thickness of the plate connecting portion 46. Furthermore, after or during the formation of the chamfering holes 47 in the carrier portion 43, another drill is used to drill holes in the carrier portion 43, forming support holes 48 in the carrier portion 43.

[0052] (Operation and Effect) Next, the operation and effect of this embodiment will be described.

[0053] In the impact tool 1 configured as described above, when the operator pulls the trigger 12 to drive the motor 20, the rotational force of the motor 20 is transmitted to the carrier portion 43 of the spindle 41 by the speed reduction mechanism 32, causing the spindle 41 to rotate about its central axis. The rotational force of the spindle 41 is transmitted to the hammer 50 by the steel ball 52, the spindle cam groove 42C, and the hammer cam groove 50B, causing the hammer 50 to rotate integrally with the spindle 41. When the hammer 50 rotates, the anvil 56 rotates together with the hammer 50 due to engagement between the hammer claw 50E and the anvil claw 56B. This causes the tip tool 70 to rotate together with the anvil 56, allowing the workpiece to be fastened.

[0054] When the rotational force (torque) required to rotate the tool bit 70 during fastening is low, the engagement between the hammer claw 50E and the anvil claw 56B is maintained. On the other hand, for example, at the end of fastening, when the rotational force (torque) required to rotate the tool bit 70 exceeds a predetermined value, the rotation of the tool bit 70 and the anvil 56 stops. Meanwhile, because the driving force of the motor 20 continues to be transmitted to the spindle 41 by the reduction mechanism 32, the driving force of the motor 20 rotates the hammer 50 relative to the anvil 56, and a rotational impact force is applied to the tool bit 70.

[0055] Specifically, the steel ball 52 rolls in the hammer cam groove 50B and the spindle cam groove 42C, and the hammer 50 moves rearward relative to the spindle 41 and the anvil 56 against the biasing force of the hammer spring 54. At this time, the hammer 50 moves rearward relative to the anvil 56 while the side surface of the hammer claw 50E slides over the side surface of the anvil claw 56B. When the amount of rearward movement of the hammer 50 exceeds the amount of overlap between the hammer claw 50E and the anvil claw 56B in the front-to-rear direction, the engagement between the hammer claw 50E and the anvil claw 56B is released.

[0056] After the engagement between the hammer claw 50E and the anvil claw 56B is released, the hammer claw 50E rotates to overcome the anvil claw 56B, and the hammer 50 is instantly pushed forward by the biasing force of the hammer spring 54. This causes the hammer claw 50E to engage with the next anvil claw 56B. As a result, a rotational impact force is applied from the hammer 50 to the anvil 56. Therefore, an excellent tightening force can be applied from the tip tool 70 to a tightening member such as a screw.

[0057] As described above, in the impact tool 1, the driving force of the motor 20 is transmitted to the hammer 50 and the anvil 56 by the spindle 41, thereby applying a rotational force and an impact force to the tool bit 70. The spindle 41 also accommodates the idle gear 35 of the reduction mechanism 32 in a gear chamber 43A of the carrier portion 43, where it is rotatably supported. The carrier portion 43 has a rear carrier plate 44 and a front carrier plate 45 that are arranged opposite each other in the front-to-rear direction, and the rear carrier plate 44 and the front carrier plate 45 are connected by a plate connecting portion 46. The plate connecting portion 46 also has a corner 46C that protrudes toward the spindle shaft 42 when viewed from the front-to-rear direction. As a result, stress may be concentrated at the corner 46C due to the force input to the spindle 41 (carrier portion 43) during operation of the impact tool 1. If the corner 46C is damaged due to stress concentration at the corner 46C, the durability of the spindle 41 and the impact tool 1 may be reduced.

[0058] Here, the corner 46C of the plate connecting portion 46 is chamfered. This suppresses stress concentration at the corner 46C and improves the durability of the impact tool 1. Furthermore, a chamfering hole 47, whose depth direction is the front-rear direction, is formed in the carrier portion 43. Specifically, the chamfering hole 47 is formed from the rear surface of the rear carrier plate 44 to the rear portion of the front carrier plate 45. That is, the chamfering hole 47 penetrates the rear carrier plate 44 and is formed in the rear portion of the front carrier plate 45. Furthermore, when viewed from the front-rear direction, a portion of the inner circumferential surface of the chamfering hole 47 coincides with the corner 46C. As described above, in the third step of the manufacturing method of the spindle 41, by performing drilling (cutting) on ​​the carrier portion 43 from the rear side using the drill DR, the corner 46C can be easily chamfered throughout the entire thickness direction of the plate connecting portion 46. This improves the workability of the spindle 41. As a result, the durability and workability of the impact tool 1 can be improved.

[0059] Furthermore, the chamfering hole 47 is formed in a circular shape when viewed from the front-to-rear direction. Therefore, the corner 46C can be easily chamfered by drilling using the drill DR as described above. Furthermore, the machining time for the chamfering hole 47 can be shortened compared to when the cross-sectional shape of the chamfering hole 47 is elongated, for example. Therefore, the workability of the spindle 41 can be further improved.

[0060] The chamfering hole 47 is a hole that penetrates the rear carrier plate 44 in the front-to-rear direction, and is configured as a concave stop hole that opens to the rear side in the front carrier plate 45. Therefore, the strength of the carrier part 43 can be increased compared to when the chamfering hole 47 is configured as a hole that penetrates the rear carrier plate 44 and the front carrier plate 45.

[0061] Furthermore, the side surface of the plate connecting portion 46 is formed by a pair of inclined surfaces 46A, and a root R portion 46D is formed at the boundary between the inclined surfaces 46A and the inner circumferential surfaces of the rear carrier plate 44 and the front carrier plate 45. This makes it possible to effectively prevent damage to the plate connecting portion 46 while suppressing stress concentration at the boundary. This point will be explained below by comparing with a spindle of a comparative example shown in Figure 6. Note that in Figure 6, parts formed in the same manner as the spindle 41 of this embodiment are assigned the same reference numerals.

[0062] As shown in this figure, in the spindle of the comparative example, instead of forming a chamfering hole 47 in the carrier portion 43, an end mill is inserted into the gear chamber 43C and used to cut the corner 46C, thereby chamfering the corner 46C. In this case, the end mill processing also forms a root rounded portion 46D at the boundary between the corner 46C and the inner circumferential surfaces of the rear carrier plate 44 and the front carrier plate 45. As a result, the intersection (indicated by arrow C in FIG. 6 ) between the root rounded portion 46D of the inclined surface 46A and the root rounded portion 46D of the corner 46C becomes a relatively sharp corner. As a result, in the spindle of the comparative example, stress concentration is likely to occur at the intersection, which may damage the plate connecting portion 46.

[0063] In contrast, as shown in FIG. 4 , in this embodiment, the chamfering holes 47 penetrate the plate connecting portion 46 in the front-rear direction, and the corners 46C are chamfered. This prevents the formation of sharp corners (intersections) at the intersections between the root rounded portions 46D of the inclined surfaces 46A and the corners 46C. That is, according to this embodiment, the root rounded portions 46D are formed at the boundaries between the corners 46C and the inner circumferential surfaces of the rear carrier plate 44 and the front carrier plate 45, while suppressing stress concentration at the intersections between the root rounded portions 46D and the corners 46C. Therefore, damage to the plate connecting portion 46 can be effectively suppressed while suppressing stress concentration at the boundaries between the inclined surfaces 46A and the inner circumferential surfaces of the rear carrier plate 44 and the front carrier plate 45.

[0064] Furthermore, when viewed from the front-rear direction, a portion of the chamfering hole 47 overlaps with the outer periphery of the front shaft portion 42B of the spindle shaft 42. Therefore, the cross-sectional area of ​​the plate connecting portion 46 can be made larger than in a configuration in which the chamfering hole 47 is disposed radially outward so as not to overlap with the front shaft portion 42B. This makes it possible to effectively ensure the strength of the plate connecting portion 46.

[0065] The tool bit 70 is located in front of the spindle 41, and the front carrier plate 45 is disposed in front of the rear carrier plate 44. In the impact tool 1, a rotational force and an impact force are applied to the tool bit 70. Therefore, when the rotational force and the impact force are applied to the tool bit 70, a reaction force acting on the carrier portion 43 is greater on the front carrier plate 45 than on the rear carrier plate 44. A thick-walled portion 45A is formed on the radially inner portion of the front surface of the front carrier plate 45, and a corner 46C overlaps with the thick-walled portion 45A when viewed from the front-rear direction. In other words, a thin-walled portion is formed on the front carrier plate 45 radially outward of the corner 46C, and the thin-walled portion is formed around the entire circumferential circumference of the front carrier plate 45. This contributes to reducing the weight of the spindle 41 while ensuring the strength of the boundary between the front carrier plate 45 and the corner 46C, where a larger reaction force acts, in the carrier portion 43. In other words, damage to the corner portion 46C can be effectively suppressed, while contributing to a reduction in the weight of the spindle 41.

[0066] In this embodiment, the chamfering holes 47 are formed in the carrier part 43 using the drill DR in the third step of the spindle 41, but the chamfering holes 47 may be formed in the carrier part 43 using an end mill. In this case, as shown in Fig. 7 , the bottom surface of the chamfering holes 47 formed in the front carrier plate 45 is formed flat.

[0067] In addition, in this embodiment, the chamfering holes 47 are formed as through-holes in the rear carrier plate 44 and as concave stop holes that are open to the rear in the front carrier plate 45. However, as shown in Fig. 8, the chamfering holes 47 may be formed as through-holes in both the rear carrier plate 44 and the front carrier plate 45. This further improves the workability of the spindle 41. In this case, the chamfering holes 47 are located radially outward compared to this embodiment.

[0068] Furthermore, in the present embodiment, in the third step of the spindle 41, the carrier portion 43 is cut from the rear side by the drill DR to form the chamfering holes 47 in the carrier portion 43, but the carrier portion 43 may also be cut from the front side by the drill DR to form the chamfering holes 47 in the carrier portion 43. In this case, the chamfering holes 47 are configured as holes that pass through the front carrier plate 45 and as concave stop holes that open to the front side in the rear carrier plate 44.

[0069] In addition, in this embodiment, the chamfering hole 47 is formed in a circular shape when viewed from the front-rear direction, but the shape of the chamfering hole 47 is not limited to this. For example, as shown in Fig. 9, the chamfering hole 47 may be formed in an elongated hole shape with the circumferential direction of the spindle 41 as the longitudinal direction.

[0070] DESCRIPTION OF SYMBOLS 1...Impact tool (work machine), 20...Motor, 35...Idle gear (transmission member), 41...Spindle, 42...Spindle shaft (shaft portion), 43...Carrier portion (protruding portion), 44...Rear carrier plate (first wall portion), 45...Front carrier plate (second wall portion), 45A...Thick portion, 46...Plate connecting portion (connecting portion), 46A...Inclined surface (side surface), 46D...Root R portion, 47...Chamfering hole portion (hole portion), 56...Anvil (tool holding portion), 70...Tool

Claims

1. A working machine comprising: a motor; a spindle rotated by the driving force of the motor; and a tool holder for holding a tool tip and driven by the rotational force of the spindle, wherein the spindle includes: a shaft portion; a first wall portion extending radially outward from the shaft portion; a second wall portion extending radially outward from the shaft portion and positioned opposite the first wall portion in the axial direction of the shaft portion; a connecting portion connecting the first wall portion and the second wall portion radially outward of the shaft portion and between the first wall portion and the second wall portion, the connecting portion having a chamfered corner portion that is convex towards the shaft portion when viewed in the axial direction; and a chamfering hole portion formed from one of the first wall portion and the second wall portion to the other of the first wall portion and the second wall portion with the depth direction being the axial direction, and a part of the inner circumferential surface coinciding with the corner portion when viewed in the axial direction.

2. A work machine as described in claim 1, wherein the chamfering hole penetrates one of the first wall portion and the second wall portion, and the chamfering hole formed in the other of the first wall portion and the second wall portion is formed in a concave shape that opens into one of the first wall portion and the second wall portion.

3. A work machine according to claim 1, wherein the chamfering hole penetrates the first wall portion and the second wall portion.

4. A work machine according to claim 1, wherein the chamfering hole is formed in a circular shape when viewed in the axial direction.

5. A work machine according to claim 1, wherein said chamfering hole is formed as an elongated hole having a longitudinal direction parallel to the circumferential direction of said spindle when viewed from said axial direction.

6. The working machine described in claim 1, wherein the connecting portion includes a pair of side surfaces which, when viewed in the axial direction, extend in a direction approaching each other as they move radially inward of the shaft portion, and a corner portion formed at a portion where the pair of side surfaces intersect, and a root R portion is formed at the boundary portion between the side surfaces and the inner surfaces of the first wall portion and the second wall portion.

7. A work machine according to claim 1, wherein a portion of said chamfering hole overlaps with said shaft portion when viewed in the axial direction.

8. A work machine as described in claim 1, wherein the bit is located on one side of the spindle in the axial direction, the second wall portion is disposed on one side of the first wall portion in the axial direction, and the second wall portion is provided with a thick portion that overlaps with the corner portion when viewed from the axial direction.

9. A work machine as claimed in any one of claims 1 to 8, wherein three connecting portions are provided between the first wall portion and the second wall portion, and the connecting portions are arranged at equal intervals in the circumferential direction of the shaft portion.

10. A work machine as described in claim 9, wherein three transmission members for transmitting the driving force of the motor are arranged between the first wall portion and the second wall portion, and when viewed from the axial direction, the chamfering hole portion is arranged adjacent to the radially inner side of the shaft portion relative to the corner portion, and the transmission members and the connecting portions are arranged alternately in the circumferential direction of the shaft portion.

11. A method for manufacturing a spindle used in a work machine, the spindle including: a shaft portion; a first wall portion extending radially outward from the shaft portion; a second wall portion extending radially outward from the shaft portion and disposed opposite the first wall portion in the axial direction of the shaft portion; a connecting portion connecting the first wall portion and the second wall portion radially outward of the shaft portion and between the first wall portion and the second wall portion and having a chamfered corner portion; and a chamfering hole portion formed in the first wall portion and the second wall portion with the depth direction being the axial direction, the chamfering hole portion having a part of an inner circumferential surface coinciding with the corner portion when viewed from the axial direction; and a first step of forming the shaft portion and a protrusion portion extending radially outward from the shaft portion; and a second step of cutting the protrusion portion from the radially outward with an end mill to form the first wall portion, the second wall portion, and the connecting portion on the protrusion portion. a third step of cutting the protrusion from one or the other axial side with a drill or an end mill to form the chamfering hole and chamfer the corner.

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