Caterpillar track link and method for manufacturing a caterpillar track link

Abstract

Caterpillar track link (230), a number of which are connected in a loop shape for use in a caterpillar track (20) of a work vehicle, the caterpillar track link (230) comprising: a running surface (42) which is designed to come into contact with a roller (24, 25) for a chassis; a plate surface (41) which is provided on a side opposite the running surface (42) and to which a chain link plate (33) can be attached; a connecting part (45, 46) which is provided between the plate surface (41) and the running surface (42), passing through in a lateral direction (Y) which is perpendicular to the connection direction (X), and which is arranged to allow side surfaces of the caterpillar track link (230) to be connected in the lateral direction (Y); a seat forming part (47) which is formed on the plate surface side (41) of the connecting part (45, 46); and a through hole (48) that extends from the plate surface (41) to the seat forming part (47) and in which a bolt element (34b) can be arranged, the seat formation part (47) includes: a seat surface (47s) in which the through hole (48) is formed and on which a nut element (34a) can be arranged, which is connected to the bolt element (34b), and characterized in that the seat forming part (47) comprises a projection (290) which is formed on the seat forming part (47) near one of the corners (47a) at the ends of the seat forming part (47) in the connection direction (X) from the walls (55a, 55b) which are provided on the sides of the connecting part (45, 46) in the connection direction (X); the corners (47a, 47b) of the ends of the seat-forming part (47) and one corner (47a) of the base (290) are formed in a rounded shape; and a fiber orientation that is formed towards a position (P1) which is on the seat formation part (47) and is near one of the corners (49a) at the ends of the seat formation part (47) in the width direction (Y).

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a crawler track link used in a work vehicle or the like and a method for manufacturing a crawler track link. Description of the state of the art

[0002] Some work vehicles are equipped with a crawler track drive unit for traveling over uneven ground. A crawler track comprises several crawler links, link plates, and the like. Several crawler links are connected endlessly by pins and bushings, and a link plate is attached to each crawler link (see, for example, JP 2014-46873 A and JP S58-67572 A).

[0003] In the structure disclosed in JP 2014-46873 A, a track plate is secured to a crawler link by locking nut elements and bolt elements. Locks are formed on the seat surfaces of the nut elements of the crawler link to limit the rotation of the nut elements. The outer structure of the seat surfaces of the nut elements and the seat surfaces of the lock elements, etc., is formed by performing broaching after forging. In JP 58-67572 A, treads, plate surfaces, seat surfaces, etc., are formed without any broaching, merely by cutting off the burr after forging, etc., by forming a burr at a corner in the width direction of the treads, plate surfaces, and seat surfaces. STATE OF THE ART DOCUMENTS

[0004] JP 2014- 46 873 A, JP S58- 67 572 A, US 2014 / 0 292 068 A1, US 2005 / 0 040 708 A1, EP 0 096 812 A2 and JP S63- 90 485 A.

[0005] US 2014 / 0 292 068 A1 shows a crawler track link according to the preamble of claims 1 and 5. US 2005 / 0 040 708 A1 shows a crawler track link for a work vehicle and EP 0 096 812 A2 shows a method and an apparatus for forging crawler track links. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0006] However, since the outer structure of the seat surface in the crawler link described in JP 2014-46873 A is formed by broaching, ridges are formed. During heat treatment, stress is concentrated on these edges, and cracks and the like may occur. In the method described in JP 58-67572 A, when burrs formed at one of the corners in the width direction of the seat surface are cut off, ridges are formed at both ends of the cut surfaces, and stress may be concentrated there.

[0007] The present invention has for its object to provide a crawler track link and a crawler track link manufacturing method in which a stress concentration can be reduced. MEANS TO SOLVE THE PROBLEM

[0008] The crawler link according to a first aspect of the present invention is a crawler link a plurality of which are looped together for use in a crawler track of a work vehicle, comprising a tread, a plate surface, a connecting portion, a seat forming portion, and a through hole. The tread is configured to contact a crawler roller. The plate surface is provided on an opposite side from the tread, and a link plate can be attached to the plate surface. The connecting portion is provided between the plate surface and the tread, passes through in a width direction perpendicular to the connecting direction, and is configured to allow side surfaces of the crawler link to communicate in the width direction. The seat forming portion is formed on the plate surface side of the connecting portion.The through-hole extends from the plate surface to the seat constituent part, and a bolt member can be arranged in the through-hole. The seat constituent part includes a seat surface and a boss. The seat surface has a through-hole formed therein, and a nut member connected to bolt members is arranged on the seat surface. The boss is formed on the seat constituent part, near one of the corners at the ends of the seat constituent part in the connecting direction, from the walls provided on the sides of the connecting part in the connecting direction. A grain is formed toward a position that is on the seat constituent part and near one of the corners at the ends of the seat constituent part in the width direction.

[0009] The track link according to a second aspect is the track link according to the first aspect, wherein the lug limits rotation of the nut members.

[0010] The crawler link according to a third aspect is the crawler link according to the first aspect, further comprising a projection. The projection is formed to project outward from the boss. The corner is provided on the projection near the boss formed on the seat forming part.

[0011] The crawler link according to a fourth aspect is the crawler link according to the third aspect, further comprising a grooved track. The grooved track is formed on the inner side of the lug to correspond to the projection.

[0012] The crawler link according to a fifth aspect of the present invention is a crawler link a plurality of which are looped together for use in a crawler track of a work vehicle, comprising a tread, a plate surface, a connecting portion, a seat forming portion, and a through hole. The tread is configured to contact a crawler roller. The plate surface is provided on a side opposite to the tread, and a link plate can be attached to the plate surface. The connecting portion is provided between the plate surface and the tread, passes through in a width direction perpendicular to a connecting direction, and is configured to allow side surfaces of the crawler link to connect in the width direction.The seat configuration part has a curved surface shape to form a part of a side surface of an imaginary circular column having a central axis along the width direction, and is formed on the plate surface side of the connecting part. The through hole passes from the plate surface to the seat configuration part, and a bolt member is arranged in the through hole. The seat configuration part is such that the corners at the ends of the seat configuration part in the connecting direction are formed in a rounded shape. A fiber line is formed toward a position located on the seat configuration part and is near one of the corners at the ends of the seat configuration part in the width direction.

[0013] The crawler link according to a sixth aspect is the crawler link according to the fifth aspect, wherein the seat forming part has a seat surface on which a nut member is arranged, which is fixed to the bolt member. The nut member has a shape such that its contact surface with the seat surface conforms to the curved surface shape.

[0014] The crawler link manufacturing method according to a seventh aspect of the present invention is a method for manufacturing a crawler link, a plurality of which are looped together for use on a work vehicle, which includes a seat constituent part having a seat surface on which a nut member is arranged to be fixed to a link plate and which is formed by forging, the method comprising a forming step and a deburring step. The forming step includes preparing a crawler link material in which the seat surface is formed at an angle to a forging direction, the burr is formed on the seat constituent part near one of the corners at the ends of the seat constituent part in a width direction perpendicular to a connecting direction of the crawler link, and the corners at the ends are formed in a rounded shape.The deburring step involves removing part or all of the burr from the track link material formed by the forming step.

[0015] The crawler link manufacturing method according to an eighth aspect of the present invention is the crawler link manufacturing method according to the seventh aspect, wherein a burr removal tool is used in the deburring step, which tool has a burr removal blade for removing burrs on the seat constituent part and a stripping blade for performing stripping treatment on the seat surface. In the burr removal step, the stripping treatment is also performed on the seat surfaces.

[0016] The crawler link manufacturing method according to a ninth aspect is the crawler link manufacturing method according to the seventh aspect, wherein a part of the burr is left in the deburring step to limit rotation of the nut member.

[0017] The crawler link manufacturing method according to a tenth aspect is the crawler link manufacturing method according to the eighth aspect, wherein in the deburring step, a part of the burr is left to restrict rotation of the nut member, and wherein material scraped off from the crawler link material by the scraping treatment accumulates in a groove formed in a portion of the burr of the crawler link material along the seat surface.

[0018] The crawler link manufacturing method according to an eleventh aspect of the present invention is the crawler link manufacturing method according to the eighth aspect, wherein the forming step forms a burr on the plate surface that contacts the link plate and is opposite to the seat surface and closer to a first corner among a first corner and a second corner at the ends in the width direction of the plate surface. The burr removal tool includes a first die having a burr punching edge and a stripping edge, and a second die corresponding to the first die. In the deburring step, the crawler link material is arranged in the second die such that the first corner is arranged on the first die side and the second corner is arranged on the second die side. EFFECTS OF THE INVENTION

[0019] The present invention provides a crawler track link and a method of manufacturing a crawler track capable of reducing stress concentration. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing a traveling vehicle to which a crawler belt in one embodiment of the present invention is attached; Fig. 2a is an oblique view of the track chain shown in Fig. 1 is shown, and Fig. 2b is an oblique exploded view of the Fig. 2a; Fig. 3 is an oblique view of the crawler belt and a crawler roller in Fig. 2a; Fig. 4 is a cross section along the AA' line in Fig. 3; Fig. 5a and Fig. 5b are oblique views of the track link in Fig. 2a; Fig. 6a is a front view of the track link in Fig. 5a, Fig. 6b is a rear view of the track link in Fig. 5a, Fig. 6c is a plan view of the track link in Fig. 5a, Fig. 6d is a bottom view of the track link in Fig. 5a, Fig. 6e is a right side view of the track link in Fig. 5a, and Fig. 6f is a left side view of the track link in Fig. 5a; Fig. 7a is a cross section along the BB' line in Fig. 6a, Fig. 7b is a cross section along the CC' line in Fig. 6a, Fig. 7c is a detailed view of the Fig. 6a, and Fig. 7d is a detailed view of the Fig. 6a; Fig. 8 is a flowchart showing a method for manufacturing the crawler track link in Fig. 2a shows; Fig. Figure 9a is an oblique view of the die used in the manufacturing process in Fig. 8 is used, Fig. 9 is a plan view of the die in Fig. 9a, and Fig. 9c is a plan view of the lower die in Fig. 9a; Fig. Figure 10a is a diagram showing the upper die in the post-treatment stage Fig. 8 is not shown, and Fig. 10b is a cross section along the DD' line in Fig. 10a; Fig. 11a is a front view of the molding obtained by molding in Fig. 10b is generated, Fig. 11b is a rear view of the molding, Fig. 11c is a top view of the molding, Fig. 11d is a bottom view of the molding, Fig. 11e is a right side view of the blank and Fig. 11f is a left side view of the mold; Fig. 12a is an oblique view of a molding obtained by post-treatment in Fig. 8 is generated, Fig. 12b is a cross section along the EE' line in Fig. 12a, Fig. 12c is a cross section along the FF' line in Fig. 12a, and Fig. 12d is a cross section along the GG' line in Fig. 12a; Fig. 13a is an oblique view of a state where burr removal and scraping in Fig. 8 are currently being carried out, and Fig. 13b is an oblique view of the first tool in Fig. 13a; Fig. 14a is a diagram of a state in which a second punch member and a third punch member are engaged in burr removal and shaving in Fig. 8 are introduced into the molding, Fig. 14b is a cross section along the HH' line in Fig. 14a, and Fig. 14c is a detailed view of the lower end portion of the second punch member in Fig. 14a; Fig. 15a is a cross-sectional view of a conventional blank formed so that the pressing direction and the seating surface are aligned with each other during forging, and Fig. 15b is a cross-sectional view of the molding in Embodiment 1; Fig. 16a is a cross-sectional photograph of the vicinity of the seat forming part in the conventional molding in Fig. 15a, and Fig. 16b is a cross-sectional photograph of the vicinity of the seat forming part in the molding of this embodiment; Fig. 17a is an oblique view of a crawler track link in Embodiment 2 according to the present invention, Fig. 17b is a detailed view of the vicinity of the seat forming part in Fig. 17a, Fig. 17c is an oblique view of the crawler link in Embodiment 2 according to the present invention, and Fig. 17d is a detailed view of the vicinity of the seat forming part in Fig. 17c; Fig. 18a is a cross section along the KK' line in Fig. 17a, and Fig. 18b is a cross section along the JJ' line in Fig. 17a; Fig. 19 is a diagram showing burr removal and shaving in the method of manufacturing a crawler track link of the Fig. 17a; Fig. 20a is an oblique view of the crawler link in a modification example of an embodiment according to the present invention, Fig. 20b is a front view of the track link in Fig. 20a, and Fig. 20c is a detailed view of the Fig. 20b; and Fig. 21a and Fig. 21b are oblique views of a nut element used for the track link in Fig. 20a is used. DETAILED DESCRIPTION OF THE INVENTION

[0020] The method for manufacturing a crawler track link in an embodiment of the present invention as well as a crawler track link manufactured by this method will be described with reference to the drawings. Embodiment 11. Structure 1-1. Track

[0021] Fig. 1 shows a state in which a crawler belt 20 is provided on a drive unit 2.

[0022] The crawler tracks 20 are provided on the left and right sides of the drive unit 2 and are endless in shape. A crawler frame 21 is arranged along the vehicle's longitudinal direction. An idler wheel 22 is rotatably supported at the front end of the crawler frame 21. A final reduction gear 23b is fixed to the rear end of the crawler frame 21. Sprocket teeth 23a are fixed to the final reduction gear 23b. A plurality of carrier rollers 24 are rotatably provided at the upper part of the crawler frame 21. A plurality of crawler track rollers 25 are rotatably provided at the lower part of the crawler frame 21.

[0023] The crawler chain 20 is wound around the idler wheel 22, the sprocket wheel 23, the carrier rollers 24 and the crawler chain rollers 25.

[0024] Fig. 2a is an oblique view of the crawler track 20. Fig. 2b is an oblique exploded view of the Fig. 2a. Fig. 3 is a partial oblique view of the crawler belt 20 and shows a state in which the crawler belt rollers 25 are rotating. Fig. 4 is a cross section along the AA' line in Fig. 3.

[0025] As in Fig. 2a and Fig. As shown in Figure 2b, the crawler track 20 mainly includes crawler links 30, bushings 31, connecting pins 32, link plates 33, pin members 34b and nut members 34a, and seal members 35. The crawler track 20 is configured to form an endless loop by attaching the link plates 33 to the crawler links 30 and connecting the crawler links 30.

[0026] The link plates 33 are mounted on the plate surfaces 41 (described in detail below) of the crawler links 30 by connecting the bolt members 34b and the nut members 34a. Through holes 331 are formed in the link plates 33, and the through holes 48 are formed in the crawler links 30. The bolt members 34b are inserted into the through holes 331 and the through holes 48 from the link plate 33 side and are fastened to the nut members 34a arranged on the seat surfaces 47s of the crawler links 30.

[0027] As in Fig. 2a and Fig. As shown in Figure 2b, for each track link plate 33, two crawler links 30 are arranged side by side in the width direction of the vehicle body. The two crawler links 30 are formed to be line-symmetrical. The two crawler links 30 aligned in the width direction are both connected to each other to form two rows of loops. As shown in Fig. 4, in the connected crawler links 30 which are adjacent to each other in a single row, the bushing hole 431 of one crawler link 30 and the pin hole 441 of the other crawler link 30 are arranged opposite to each other.

[0028] The bushing 31 has a cylindrical shape and is pressed into the bushing hole 431 of one of the crawler chain links 30. As shown in Fig. 4, the sealing members 35 are arranged at the base of the bushing 31, and are arranged in a large diameter part 441 of the bolt hole 441 of the crawler link 30.

[0029] The connecting pin 32 is inserted inside the bushing 31 and press-fitted into the pin hole 441 of the other crawler link 30. The crawler links 30 of the respective rows are arranged at both ends in the width direction of the bushing 31 and the connecting pin 32, so that the two rows of crawler links 30 are linked together.

[0030] In this way, a crawler link 30 is connected to a crawler link 30 through the bushing hole 431 and the bolt hole 441. In Fig. 2, the connecting direction of the crawler links 30 is denoted by X, and a direction perpendicular to the connecting direction X is denoted as the width direction Y. The connecting direction X may also be referred to as the direction facing from the bushing hole 431 to the pin hole 441 in a crawler link 30, or the direction facing from the pin hole 441 to the bushing hole 431.

[0031] As in Fig. 3 and Fig. 4, the crawler rollers 25 are arranged on the side opposite the link plates 33 with the crawler links 30 therebetween. Two crawler rollers 25 are arranged side by side in the vehicle width direction, and two crawler rollers 25 are rotatably supported by a rotating shaft 251. Each of the crawler rollers 25 abuts the crawler link 30 in this row. As described in detail above, a tread 42 is formed on the side opposite the plate surface 41 of the crawler link 30, and the crawler rollers 25 rotate in contact with the tread 42. The crawler rollers 24 rotate in the same manner. 1-2. Track chain coupling links

[0032] Fig. 5a and Fig. 5b are oblique views of the track link 30 of one row. Fig. 6a is a front view of the crawler link 30, and Fig. 6b is a rear view of the crawler track link 30. Fig. 6c is a plan view of the crawler link 30 and Fig. 6d is a bottom view of the track link 30. Fig. 6e is a right side view of the crawler link 30 and Fig. 6f is a left side view of the track link 30. Fig. 7a is a cross section along the BB' line in Fig. 6a and Fig. 7b is a cross section along the CC' line in Fig. 6a. Fig. 7c and Fig. 7d are detailed views of the Fig. 6a.

[0033] As in Fig. 5 and Fig. 6, the crawler link 30 in this embodiment is a substantially elliptical member curved at both ends and mainly includes a plate surface 41, a tread 42, a first connecting part 43, a second connecting part 44, a first connecting part 45, a second connecting part 46, seat forming parts 47, and through holes 48.

[0034] The plate surface 41 is formed on a first surface portion 51, which is located on the outside when the crawler links 30 are connected into a loop. The plate surface 41 is a flat surface, and two through holes 48 are formed therein. Corners 41a and 41b at both ends in the width direction Y of the plate surface 41 are, as shown in Fig. 7a and Fig. 7b, is formed in a rounded shape. In a state where the Fig. 2 are arranged in two rows, if we define the portion facing inward as a first side surface part 53 and the portion facing outward as a second side surface part 54, the corner 41a is arranged on the side of the second side surface part 54, and the corner 41b is arranged on the side of the first side surface part 53.

[0035] The tread 42 is formed on a second surface portion 52, which is located on the inside of the loop when the crawler links 30 are connected to form a loop. The tread 42 comes into contact with the idler wheel 22, the carrier rollers 24, and the crawler rollers 25, as described above. The corners 42a at both ends in the width direction Y of the tread 42 are, as shown in Fig. 7a and Fig. 7b, formed in a rounded shape.

[0036] The first connecting part 43 and the second connecting part 44 are formed at both ends in the connecting direction X of the crawler track link 30.

[0037] The first connecting part 43 has the socket hole 431 formed along the width direction Y. The socket hole 431 is formed from the first side surface part 53 through the second side surface part 54. The end face 43a of the first connecting part 43 in the connecting direction X is curved to form a substantially annular shape along the socket hole 431 in the front view in Fig. 6a.

[0038] The second connecting part 44 is provided with the bolt hole 441, which passes in the width direction Y from the first side surface part 53 to the second side surface part 54. The end face 44a in the connecting direction X of the second connecting part 44 is curved to form a substantially annular shape along the bolt hole 441 in the front view in Fig. 6a. As in Fig. 5 and Fig. As shown in Fig. 6b, the large-diameter part 441a and a small-diameter part 441b are provided with the bolt hole 441, and the large-diameter part 441a is formed on the side of the first side surface portion 53. A sealing member 35 is fitted in the large-diameter part 441a.

[0039] The crawler links 30 are designed such that in a state where the crawler links 30, as shown in Fig. 2a, are arranged in two rows, the second connecting part 44 is arranged more towards the outside than the first connecting part 43 based on the space between the two rows of links in the width direction Y.

[0040] The first connecting part 45 and the second connecting part 46 are formed to penetrate from the first side surface part 53 to the second side surface part 54 and are spaces that connect both sides surrounding the crawler link 30 (the first side surface part 53 side and the second side surface part 54 side). The first connecting part 45 and the second connecting part 46 are formed between the tread 42 and the plate surface 41, and are aligned between the first connecting part 43 and the second connecting part 44.

[0041] A seat forming part 47 is formed on the side of the plate surface 41 of the first connecting part 45. A seat forming part 47 is also formed on the side of the plate surface 41 of the second connecting part 46. The seat forming parts 47 have seat surfaces 47s on which the Fig. 2a shown nut elements 34a are arranged, and stepped parts 49.

[0042] In this embodiment, the seat surfaces 47s indicate the portions of the seat forming parts 47 where the nut elements 34a are arranged, and it should be understood that the seat forming parts 47 include the area surrounding them. The through holes 48 are formed from the plate surface 41 to the seat forming part 47. More specifically, the through holes 48 are formed between the seat surfaces 47s and the plate surface 41. The above-described bolt elements 34b are inserted into these through holes 48 through the chain link plate 33 in Fig. 2b, and the bolt elements 34b are screwed into the nut elements 34a arranged on the seating surfaces 47s, thereby fastening the chain link plate 33 to the plate surface 41.

[0043] As in Fig. 5b and Fig. As shown in Fig. 6a, the stepped portions 49 are formed in a stepped shape on the seating surfaces 47s to prevent rotation of the bolt members 34b. The stepped portions 49 are formed from the walls 55a and 55b on both sides in the connecting direction X of the first connecting portion 45 toward the through holes 48. The stepped portions 49 are also formed from the walls 55a and 55b on both sides in the connecting direction X of the second connecting portion 46 toward the through holes 48. The wall 55a is the inner edge portion of the socket hole 431 in the first connecting portion 43. The wall portion 55b is the portion separating the first connecting portion 45 from the second connecting portion 46. The wall portion 55c is the inner edge portion of the bolt hole 441 in the second connecting portion 44.

[0044] Thus, forming the stepped parts 49 on both sides laterally surrounding the through holes 48 in the connecting direction X restricts rotation even when the nut members 34a attempt to rotate, so that the stepped parts 49 function as detents.

[0045] As in Fig. As shown in Fig. 7c, the corner 49a formed on the side of the through-hole 48 of the stepped parts 49 in the first connecting part 45 is formed in a rounded shape. Likewise, as shown in Fig. As shown in Figure 7d, the corner 49a formed on the side of the through-hole 48 of the stepped portions 49 in the second connecting portion 46 is formed in a rounded shape. Rounding the corner 49a thus reduces the stress concentration at the corner 49a during heat treatment during manufacturing.

[0046] As in Fig. 7a, which is a cross-section across the first connecting part 45, and in Fig. As shown in Fig. 7b, which is a cross-sectional view taken across the second connecting part 46, the corners 47a and 47b at both ends in the width direction Y of the seat configuration parts 47, which are provided on the plate surface 41 side of the first connecting part 45 and the second connecting part 46, respectively, are formed in a rounded shape. The corner 47a is the location where the seat configuration part 47 and the first side surface part 53 intersect. The corner 47b is the location where the seat configuration part 47 and the second side surface part 54 intersect. The corner 47a indicates the first side surface part 53 side of the seat configuration part 47, and the corner 47b indicates the second side surface part 54 side of the seat configuration part 47.

[0047] This rounded shape allows for a reduction in the stress concentration at the corners 47a and 47b during heat treatment during manufacture.

[0048] The track link 30, which is in Fig. 6 and Fig. 7, the track link in the left row shows in Fig. 4, and the track link 30 in the right row in Fig. 4 is symmetrical with the caterpillar track in the left row.

[0049] As in Fig. As shown in Fig. 4, in the two crawler links 30 arranged side by side in a row, the first connecting part 43 of one crawler link 30 is arranged inward from the second connecting part 44 of the other crawler link 30. It can also be said that the bushing hole 431 of one crawler link 30 is arranged opposite the inside of the pin hole 441 of the other crawler link 30. The bushing 31 is then press-fitted into the bushing hole 431 located on the inside, and the connecting pin 32 inserted into the bushing 31 is press-fitted into the small-diameter part 441b of the pin hole 441 located on the outside. The seal members 35 are arranged at the large-diameter part 441a of the pin hole 441.

[0050] The protrusions 25a projecting around the circumferential direction are also formed at both ends in the width direction Y of the crawler rollers 25. That is, two protrusions 25a of one crawler roller 25 are arranged to laterally surround the two running surfaces 42 of adjacent crawler links 30 from both sides. Consequently, the crawler rollers 25 can rotate without deviating from the running surfaces 42. The corners 42a at both ends in the width direction Y of the running surface 42 of the crawler link 30 are formed here, as shown in Fig. 7a and Fig. 7b, is formed in a rounded shape. Rounding the corners 42a in this manner at both ends of the tread 42 prevents the projections 25a from being scratched or worn. 2. Method for producing a track link

[0051] The method of manufacturing the above-described crawler link 30 will now be described. Fig. 8 is a flowchart of the method for manufacturing the crawler track link in this embodiment. 2-1. Overview of the manufacturing process

[0052] First, in step S10, a round, rod-like material is heat-treated. Manganese-boron steel is used as the material.

[0053] Next, in step S20, the heated bar material is swaged in a die installed in a press or other such forging machine to approximate the rough shape of the crawler track link 30.

[0054] Next, in step S30, blocking is performed on the upset material using a block impression die, whereby the material's shape is brought closer to the track link 30. In this blocking, the block impression die is installed in a press or other forging machine, and the forming is performed.

[0055] Then, in step S40, post-processing is performed on the billet material. An upper die 60a and a lower die 60b (described below) are installed in a forging machine such as a press, and post-processing is performed to produce a blank 61. The forming process from upsetting to post-processing forms a burr 62 at the parting line between the upper and lower dies.

[0056] Next, in step S50, a burr removal tool 80 is used to remove the burr 62 (described below) and shave the seating surfaces 47s'.

[0057] Next, in step S60, the blank subjected to burr removal and shaving is subjected to heat treatment to increase the hardness of the seating surfaces 47s' or the like, and post-machining is performed to form the through holes 48, thereby manufacturing the crawler link 30. 2-2. Post-processing

[0058] In this embodiment, the forming process is divided into three stages: upsetting, preforming, and post-processing, with a die being used for each stage. Because the three stages gradually approach the shape of the crawler link 30, the dies used for upsetting, preforming, and post-processing become increasingly finer. In the following description, forming using post-processing is described as an example. 2-2-1 die

[0059] Fig. 9a is an oblique view of the upper die 60a and the lower die 60b used for post-processing. Fig. 9b is a plan view of the upper die 60a, and Fig. Figure 9c is a plan view of the lower die 60b. Fig. Figure 9b is a top view of the upper die 60a.

[0060] The blank is placed on the lower die 60b after preforming, the upper die 60a is lowered vertically (in the direction of arrow Z) toward the lower die 60b, and pressing is performed between the upper die 60a and the lower die 60b to perform post-treatment and produce a final-shaped blank 61.

[0061] Fig. 10a shows a state in which the upper die 60a has been removed from the state during pressing. Fig. 10b is a cross section of the pressing state and is a cross section along the DD' line in Fig. 9b.

[0062] A lower forming tool 601b formed in the lower die 60b mainly forms the second side surface part 54 of the crawler link 30. An upper forming tool 601a formed in the upper die 60a mainly forms the first side surface part 53 of the crawler link 30.

[0063] Here, the portions of the blank 61 that are formed in the crawler link 30 (the finished product) are indicated by adding an apostrophe to the numbers indicating the components of the crawler link 30. That is, the blank 61 includes a crawler link 30' (more precisely, the portion where the crawler link 30 is formed) and the ridge 62.

[0064] During the forming step, the blank 61 is formed at an angle to the pressing direction of the forging (arrow Z). Fig. 10b are formed at an angle of four degrees to the vertical direction. That is, the seat forming surface 602b of the lower die 60b for forming the seat surface 47s' is formed at an angle of four degrees to the pressing direction (arrow Z) (see θ in Fig. 10b). This inclination is created by the rough shaping.

[0065] Thus, the seat surface 47s' can be formed in a plane without forming a die slope by forming the seat forming surface 602b in an oblique direction with respect to the pressing direction (arrow Z). The angle of inclination is not limited to four degrees and can be any angle that does not require forming a die slope.

[0066] The portions of the upper die 601a and the lower die 601b corresponding to the corners 47a' and 47b' are also formed in a curvature, so that the corners 47a' and 47b' will have a rounded shape at both ends in the width direction Y of the seat surface 47s'.

[0067] Consequently, the corners 47a' and 47b' at both ends in the width direction Y of the seat surface 47s' are formed in a rounded shape by forming. 2-2-2. Shape of the molding

[0068] The shape of the molding 61 after post-treatment is now described.

[0069] Fig. 11a is a front view of the molding 61 after post-treatment, Fig. 11b is a rear view of the blank 61, Fig. 11c is a plan view of the blank 61, Fig. 11d is a bottom view of the blank 61, Fig. 11e is a right side view of the blank 61, and Fig. 11f is a left side view of blank 61. Fig. 11a to Fig. 11f correspond to the Fig. 6a to 6f.

[0070] The burr 62 is formed along the parting surface between the upper die 60a and the lower die 60b during the post-treatment (see Fig. 10a) is formed on the blank 61. The burr 62 consists of an outer peripheral burr portion 70 formed around the outer edge of the crawler link 30', and a first inner burr portion 71, a second inner burr portion 72, a third inner burr portion 73, and a fourth inner burr portion 74 formed in the holes.

[0071] As in Fig. 11a, the outer peripheral ridge portion 70 is composed of a first outer peripheral ridge portion 701 formed around the outer periphery of a first connecting part 43' of the crawler link 30', a second outer peripheral ridge portion 702 formed on a plate surface 41', a third outer peripheral ridge portion 703 formed around the outer periphery of a second connecting part 44', and a fourth outer peripheral ridge portion 704 formed on a tread surface 42'.

[0072] As mainly in Fig. 11f, Fig. 11c and Fig. 11d, the first outer peripheral ridge portion 701 is formed to pass through the approximate center point in the width direction Y of the end face 43a' of the first connecting part 43'. As shown in Fig. As shown in Fig. 11d, the second outer peripheral ridge portion 702 is formed to conform to the shape of the corner 41a' and to be closer to the corner 41a' at the end on the side of the second side surface part 54' on the plate surface 41'. The corner on the opposite side from the corner 41a' is shown as the corner 41b'.

[0073] As in Fig. 11e, Fig. 11c and Fig. 11d, the third outer peripheral ridge portion 703 is formed to pass through the approximate center point in the width direction Y of the end face 44a' of the second connecting part 44'. As shown in Fig. 11c, the fourth outer peripheral ridge portion 704 is formed on the tread 42', and bent to pass through the approximate center in the width direction Y.

[0074] The parting surface between the upper die 60a and the lower die 60b used in the post-treatment is formed such that the outer peripheral burr portion 70 is formed as described above.

[0075] Thus, the outer peripheral ridge portion 70 is formed so as not to pass through the corners at both ends in the width direction Y, and to pass inward from the corners at both ends. Therefore, the corners at both ends in the Y direction of the crawler link 30' can be formed into a rounded shape by forming a curved shape at the positions of the upper die 60a and the lower die 60b corresponding to the corners at both ends in the width direction of the crawler link 30'.

[0076] As in Fig. 11a and Fig. 11b, the first inner ridge portion 71 is formed in a bushing hole 431', the second inner ridge portion 72 is formed in a first connecting part 45', the third inner ridge portion 73 is formed in a second connecting part 46', and the fourth inner ridge portion 74 is formed in a bolt hole 441'.

[0077] Fig. 12a is an oblique view of the blank 61 and Fig. 12b is a cross section along the EE' line in Fig. 12a. Fig. 12c is a cross section along the FF' line in Fig. 12a and Fig. 12d is a cross section along the GG' line in Fig. 12a.

[0078] As in Fig. 12d, the first inner ridge portion 71 is formed at the approximate center point in the width direction Y of the socket hole 431'.

[0079] As in Fig. 12b, the fourth inner ridge portion 74 is formed at the approximate center point in the width direction Y of a small diameter portion 441b' of the bolt hole 441'.

[0080] As in Fig. 12c, the second inner ridge portion 72 is formed closer to the corner 47a' from the corners 47a' and 47b' on the side of the first side surface part 53' at both ends in the width direction Y of the seat forming part 47'.

[0081] The third inner ridge portion 73 is similar to the second inner ridge portion 72 in that the third inner ridge portion 73 is formed closer to the corner 47a' from the corners 47a' and 47b' on the side of the first side surface part 53', at both ends in the width direction Y of the seat forming part 47'.

[0082] It can also be said that the second inner ridge portion 72 and the third inner ridge portion 73 are formed near the rounded corner 47a'.

[0083] As in Fig. 11a, the stepped parts 49' are also formed by forging, and the corners 49a' of the stepped parts 49' are formed in a rounded shape by forging.

[0084] The burr 62 described above is removed in the subsequent burr removal step. 2-3. Burr removal and scraping

[0085] The burr removal and scraping steps are now described in detail. Burr removal and scraping are performed using a burr removal tool 80. Fig. 13a is a diagram of the state when the blank 61 has been placed in the burr removal tool 80. The burr removal tool 80 has a second die 82 that supports the blank 61 and a first die 81 that moves from top to bottom to remove the burr 62. Fig. 13b is an oblique view of the second die 82, which is in Fig. 13a as seen from the back of the paper. (a) Second die

[0086] The second die 82 has a plate-like element 820, a placement space 821, and a support frame 822. As shown in Fig. As shown in FIG. 13b, the placement space 821 is a space formed in an oval shape at the center of the plate-like member 820, is formed to conform to the shape of the crawler link 30', and has the blank 61 placed therein. The support frame 822 is formed around the placement space 821 and supports the outer peripheral ridge portion 70 from below. The support frame 822 is formed in an irregular shape from the plate-like member 820 to support the blank 61 such that the seat surface 47s' of the blank 61 is arranged in the vertical direction.

[0087] The support frame 822 consists of a first support frame part 822a, a second support frame part 822b, a third support frame part 822c, and a fourth support frame part 822d. The first support frame part 822a is the edge of the curved portion of the oval placement space 821 and is flush with the plate-like member 820. The first support frame part 822a mainly supports the first outer peripheral ridge portion 701.

[0088] The second support frame part 822b protrudes in a wave-like shape from the substantially straight edge of the oval placement space 821. The second support frame part 822b supports the second outer peripheral ridge portion 702 formed on the plate surface 41' of the molded article 61.

[0089] The third support frame part 822c is the edge of the curved portion of the oval placement space 821, is formed to protrude from the plate-like member 820, and the height of the third support frame part 822c from the plate-like member 820 is uniform. The third support frame part 822c supports the third outer peripheral ridge portion 703.

[0090] The fourth support frame part 822d is formed at an angle on the substantially straight edge of the oval placement space 821 so that its height decreases from the third support frame part 822c. The fourth support frame part 822d supports the fourth outer peripheral ridge portion 704 formed on the running surface 42' of the molded article 61. (b) First die

[0091] The first die 81 has an outer peripheral part 810, a first punch 811, a second punch 812, a third punch 813 and a fourth punch 814.

[0092] The outer peripheral part 810 has a space 810a that conforms to the shape of the crawler link 30' for removing the outer peripheral burr portion 70 of the blank 61. The outer peripheral burr portion 70 is cut off by being squeezed between the support frame 822 and the outer peripheral part 810.

[0093] The first punch 811 is a substantially cylindrical member that removes the first inner burr portion 71 and creates the bushing hole 431 of the crawler link 30.

[0094] The second punch 812 is a substantially cylindrical member that removes the second inner burr portion 72 and creates the first connecting part 45 of the track link 30.

[0095] The third punch 813 is a substantially cylindrical member that removes the third inner burr portion 73 and creates the second connecting part 46 of the crawler link 30.

[0096] The fourth punch 814 is a substantially cylindrical member that forms the small diameter portion 441b of the bolt hole 441 of the crawler link 30.

[0097] The second stamp 812 and the third stamp 813 are now described

[0098] Fig. 14a is a diagram showing a state where the second punch 812 and the third punch 813 have been inserted into the blank 61. Fig. 14b is a cross section along the HH' line in Fig. 14a. Fig. Figure 14c is a detailed view of the lower end portion of the second punch 812.

[0099] As in Fig. 14b and Fig. As shown in Figure 14c, a burr cutting edge 812a is provided at the lower end of the second punch 812. A stripping edge 812b is also provided at the upper side of the burr cutting edge 812a. The stripping edge 812b protrudes outward beyond the burr cutting edge 812a (see arrow J).

[0100] Since the scraper blade 812b protrudes further toward the seat surface 47s' than the burr punching blade 812a, the seat surface 47s' is scraped by the scraper blade 812b. That is, the scraping is performed together with the burr punching. This scraping produces seat surfaces 47s with guaranteed accuracy.

[0101] The third stamp 813 has the same structure as the second stamp 812.

[0102] Likewise, as in Fig. 14b, the blank 61 is arranged such that the corner 41a' is arranged near the second outer peripheral ridge portion 702 on the first die 81 side and the corner 41b' is arranged on the second die 82 side.

[0103] During this shaving, a force is applied to the seating surfaces 47s' in the thrust direction, but in this embodiment, the second outer peripheral burr portion 702 is formed by the corner 41a' of the plate surface 41' (the side opposite the corner 41b' on the side where the second inner burr portion 72 is formed). Consequently, a large area S1 can be secured over which the second support frame part 822b and the plate surface 41' are opposed, supporting the molding 61 against a force applied in the thrust direction, and shaving can be performed systematically. 3. Working examples and comparative examples

[0104] Fig. 15a is a diagram of a conventional blank 1061 formed by aligning the seating surfaces with the pressing direction during forging. Fig. Figure 15b is a diagram of the molding 61 described above. Fig. 15a is a cross section taken with the FF' line in Fig. 12a. Fig. 15b is the same as Fig. 12c.

[0105] As in Fig. 14a and Fig. As shown in Fig. 14b, the seat surface 47s' of the blank 61 in this embodiment is inclined in the forming direction Z during forming, in contrast to the conventional blank, so that it can be formed in a plane without having to form a die slope, as in the case of the seat surface 1047s' of the conventional blank 1061.

[0106] Moreover, since there is no need for a swage slope, the position of the second inner ridge portion 72 can be closer to the corner 47a' from the corners 47a' and 47b' at both ends in the width direction Y of the seat forming part 47, so that the flatness of the seat surface 47s' can be ensured.

[0107] Since the burr has been removed from the finished crawler link, the difference between the position of the burr on the seat surface of a conventional crawler link and that of the crawler link in this embodiment is difficult to perceive based on the external appearance, but the position of the burr before removal can be identified by checking the grain pattern formed along the external shape of the blank during forging.

[0108] Fig. 16a is a cross-sectional photograph of the vicinity of a seat forming part 1047' in the conventional molding 1061, and Fig. 16b is a cross-sectional photograph of the vicinity of the seat forming part 47' in the molding 61 in this embodiment. As in Fig. 16b, it can be confirmed that the fiber direction of the molded article 61 in this embodiment is directed to a position P1 closer to the corner 47a' of the seat forming part 47'. Fig. 16b one can also see that after machining the texture gradient intersects a dashed line V indicating the seat surface 47s.

[0109] A comparison of the Fig. 16b, which shows a molding of this embodiment, confirms that in the conventional molding 1061, which is shown in Fig. 16a, the fiber direction is toward a position P2, ie closer to the approximate center of the seat forming part 1047'. 4. Main features etc.4-1

[0110] The crawler links 30 of Embodiment 1 are connected in a loop for use in the crawler track 20 of a hydraulic excavator or the like (an example of a work vehicle), and each includes the tread 42, the plate surface 41, the first connecting part 45 (an example of a connecting part), the second connecting part 46 (an example of a connecting part), the seat forming parts 47, and the through holes 48. The tread 42 is in contact with the carrier rollers 24 (an example of a roller for a traveling gear) and the crawler rollers 25 (an example of a roller for a traveling gear). The plate surface 41 is provided on the opposite side from the tread 42, and a link plate 33 is attached thereto.The first connecting part 45 and the second connecting part 46 are between the plate surface 41 and the tread 42, pass in the width direction Y, which is perpendicular to the connecting direction X, and allow the first side surface part 53 (an example of a side surface part) and the second side surface part 54 (an example of a side surface part) of the crawler link 30 to communicate in the width direction Y. The seat forming parts 47 are formed on the plate surface 41 side of the first connecting part 45 and the second connecting part 46. The through holes 48 pass from the plate surface 41 to the seat forming part 47, and the bolt members 34b are arranged therein. The seat forming parts 47 include a seat surface 47s and stepped parts 49. The through holes 48 are formed in the seat surfaces 47s, and nut members 34a, which are fixed to the bolt members 34b, are arranged on the seat surfaces 47s.The stepped portions 49 are formed opposite the seat surfaces 47s, facing the through holes 48 from each of the walls 55a and 55b provided on both sides of the first connecting portion 45 in the connecting direction X, and limit the rotation of the nut members 34a. The corners 47a and 47b of the seat configuration portion 47 in the width direction Y and the corner 49a on the seat surface 47s side of the stepped portion 49 are formed in a rounded shape. A grain is formed toward the position P1, which is on the seat configuration portion 47 and closer to the corner 47a (one of the corners 47a and 47b) at both ends of the seat configuration portion 47 in the width direction Y.

[0111] As in Fig. 6a and Fig. 7a and Fig. 7b, the corner 49a of the stepped part 49 and the corners 47a and 47b in the width direction Y of the seat forming part 47 are formed in a rounded shape, which reduces the concentration of stress and reduces cracking, etc. during heat treatment.

[0112] Since the ridge (the second inner ridge section 72 in Fig. 12c) is formed in an oblique forming step of forging on the side of the corner 47a', the seating surfaces 47s in which the nut elements 34a are arranged can be secured, thus no broaching has to be carried out afterwards and the manufacturing costs can be reduced. 4-2

[0113] In the crawler track link 30 in this embodiment, the stepped parts 49 restrict the rotation of the nut members 34a.

[0114] The stepped parts 49 thus act as locking devices for the nut elements 34a. 4-3

[0115] The method for manufacturing the crawler links in this embodiment is a method for manufacturing crawler links used for use in a hydraulic excavator 100 (an example of a work vehicle) connected into a loop, each having seat forming parts 47 including seat surfaces 47s in which nut members 34a fixed to a link plate 33 are arranged and formed by forging, the method comprising a step S40 (an example of a forming step) and a step S50 (an example of a burr removing step).

[0116] As in Fig. 10b, in step S40 (an example of a forming step), the seat surfaces 47s are formed at an angle to the forging direction Z, at least the second inner burr portion 72 (an example of a burr portion) and the third inner burr portion 73 are formed on the seat forming parts 47' in the vicinity of the corner 47a (out of the corners 47a' and 47b' at both ends of the seat forming parts 47') in the width direction Y perpendicular to the connecting direction X of the crawler link 30', thereby producing a blank 61 (an example of a crawler link material) in which the corners 47a' and 47b' at both ends are formed in a rounded shape. In step S50 (an example of a burr removing step), part or all of the burr 62 is removed from the blank 61 (an example of a crawler link material) formed in step S40 (an example of a forming step).

[0117] As in Fig. 15a and Fig. As shown in Fig. 15b, due to the forging direction Z thus inclining with respect to the seat surfaces 47s' and also due to the formation of the second inner burr portion 72 and the third inner burr portion 73 near the corner 47a' at the end of the seat forming part 47', unlike when the forging direction Z is made to coincide with the seat surface 47s', there is no need for a swage slope in the seat surface portion, and no burr is formed on the seat surfaces 47s'. Consequently, the seat surfaces 47s' can be formed in a plane. Also, broaching does not need to be performed after forming, and in this embodiment, for example, only shaving can be performed along with burr removal instead of broaching, and this reduces costs. 4-4

[0118] In the method for manufacturing a crawler link in this embodiment, the burr removal tool 80 used in step S50 (an example of a burr removal step) includes the burr cutting edge 812a (an example of a burr removal edge) and the scraping edge 812b. The burr cutting edge 812a removes the second inner burr portion 72 (an example of a burr) on the seat formation parts 47. The scraping edge 812b scrapes the seat surfaces 47s'.

[0119] Since the burr removal step and scraping can be performed at the same time, manufacturing will take less time. 4-5

[0120] In the method for manufacturing a crawler track link in the present embodiment, as shown in Fig. 11d and Fig. As shown in Fig. 12c, the result of step S40 (an example of a forming step) is that the second outer peripheral burr portion 702 (an example of a burr part) is formed on the plate surface 41' (which is in contact with the link plate 33 and is the surface opposite from the seat surfaces 47s') closer to the corner 41a' (an example of a first corner) (among the corner 41a' (an example of a first corner) and the corner 41b' (an example of a second corner)) at both ends in the width direction Y of the plate surface 41'. The burr removal tool 80 includes the first die 81 having the burr punching edge 812a (an example of a burr removal edge) and the stripping edge 812b, and the second die 82 corresponding to the first die 81.In step S50 (an example of a burr removal step), the blank 61 (an example of a crawler link material) is arranged in the second die 82 so that the corner 41a' is arranged on the first die 81 side, and the corner 41b' is arranged on the second die 82 side.

[0121] Thus, forming the second outer peripheral ridge portion 702 closer to an end side on the plate surface 41', which is the side opposite to the seating surfaces 47s', secures a surface S1 (see Fig. 14b) via which the load exerted on the seating surfaces 47s' during the scraping of the seating surfaces 47s' in the thrust direction is supported. Embodiment 2

[0122] Next, the method for manufacturing a crawler track link and the crawler track link of a second embodiment according to the present invention will be described.

[0123] The crawler link in Embodiment 2 differs from the crawler link in Embodiment 1 in the structure of the side where rotation of the nut elements is prevented. Therefore, the description will focus on how this Embodiment 2 differs from Embodiment 1. 1. Structure

[0124] Fig. 17a is an oblique view of a crawler track link 230 as seen from above on the side of the second side surface part 54. Fig. 17b is a detailed view of the area near the seat forming part 47 in Fig. 17a. Fig. 17c is an oblique view of the crawler link 230 as seen from above on the side of the first side surface part 53. Fig. 17d is a detailed view of the area near the seat forming part 47 in Fig. 17c. Fig. 18a is a cross section along the KK' line in Fig. 17a and Fig. 18b is a cross section along the LL' line in Fig. 17a.

[0125] As in Fig. 17 and Fig. 18, the crawler link 230 in this Embodiment 2 differs from the crawler links 30 in Embodiment 1 in that the crawler link 230 includes lugs 290 that use a ridge instead of the stepped portions 49.

[0126] The projections 290 are formed on the seat-forming parts 47, closer to the corner 47a on the side of the second side surface part 54 of the seat-forming part 47. The projection 290 is formed between the wall 55a and the wall 55b in the first connecting part 45. Likewise, the projection 290 is formed between the wall 55b and the wall section 55c in the second connecting part 46.

[0127] As in Fig. 18a and Fig. As shown in Fig. 18b, the corners 290a at both ends in the width direction Y of the edge 290e on the tread 42 side of the boss 290 are formed in a rounded shape, which reduces the stress concentration.

[0128] A projection 291 is provided on the crawler link 230 to protrude outwardly from the projection 290. As shown in Fig. 17c and Fig. As shown in Fig. 17d, the protrusion 291 is formed on the first side surface part 53 from the seat forming part 47 of the first connecting part 45 to the seat forming part 47 of the second connecting part 46. Similarly, the corner 47a on the second side surface part 54 side of the seat forming part 47 is formed in a rounded shape and is part of the protrusion 291. That is, it can be said that the boss 290 is formed on the seat forming part 47 and closer to the rounded corner 47a.

[0129] Likewise, as in Fig. 17b and Fig. 18a and Fig. 18b, concave groove traces 292 are formed on the inside of the lugs 290, corresponding to the projections 291. The groove traces 292 are traces of a groove formed by the accumulation of chips in a groove formed in the blank 261 (described below).

[0130] As described above, in the crawler link 230 in this Embodiment 2, since part of the burr is used to form the boss 290, the burr needs to be located more toward the outside than in Embodiment 1 to secure the seating surfaces 47s. Therefore, the projection 291 is formed and the burr is moved more toward the outside than in Embodiment 1. 2. Method for producing a track link

[0131] The manufacturing method of the crawler link of Embodiment 2 differs from Embodiment 1 in the burr removal and shaving (step S50). Therefore, the description will focus on the burr removal and shaving.

[0132] Fig. 19 is a diagram illustrating burr removal and shaving in Embodiment 2. Fig. 19 is a cross section at a position corresponding to the Fig. 14b, but the viewing direction is different from that of Fig. 14b is reversed. A second punch 2812 in Embodiment 2 has a burr cutting edge 2812a having a different shape from that of the burr cutting edge 812a of the second punch 812 in Embodiment 1, to form the boss 290 by leaving a portion of the second inner burr portion 72. The second punch 2812 in Embodiment 2 has a cylindrical main body 2812c, a burr cutting edge 2812a disposed on the lower side of the main body 2812c, and a stripping edge 2812b disposed on the lower side of the main body 2812c. The main body 2812c is formed in an outer shape that substantially matches the shape of the first connecting part 45. The burr punching edge 2812a has a smaller diameter than the main body 2812c to leave the shoulder 290.The stripping edge 2812b is arranged on the main body 2812c to be on the side of the seat surface 47s' of the blank 261. Also, the stripping edge 2812b is arranged above the burr punching edge 2812a in the height direction.

[0133] When the second punch 2812 is inserted into the second inner burr portion 72, a portion of the second inner burr portion 72 is removed by the burr cutting edge 2812a to form the first connecting portion 45. Likewise, a portion of the second inner burr portion 72 is left to form the boss 290'.

[0134] The scraping is performed by scraping the surface of the seat 47s' with the scraping edge 2812b. The chips generated by the scraping collect in the groove 262 of the blank 261. The chips accumulated in this groove 262 are integrated with the groove 262 by heat, thereby forming the groove marks 292 described above.

[0135] Furthermore, the corners 290a at both ends in the width direction Y of the projection 290 are subsequently formed into a rounded shape by machining.

[0136] The crawler link 230 of Embodiment 2 is produced by the above steps. 3. Main features, etc.3-1

[0137] The crawler link 230 of Embodiment 2 is one of a plurality of crawler links connected in a loop for use in the crawler track 20 of a hydraulic excavator or the like (an example of a work vehicle), and includes the tread 42, the plate surface 41, the first connecting part 45 (an example of a connecting part), the second connecting part 46 (an example of a connecting part), the seat forming parts 47, and the through holes 48. The tread 42 is in contact with the carrier rollers 24 (an example of a roller for a traveling gear) and the crawler rollers 25 (an example of a roller for a traveling gear). The plate surface 41 is provided parallel to the tread 42, and the link plate 33 is fixed thereto.The first connecting part 45 and the second connecting part 46 are between the plate surface 41 and the tread 42, pass in the width direction Y, which is perpendicular to the connecting direction X, and allow the first side surface part 53 (an example of a side surface part) and the second side surface part 54 (an example of a side surface part) of the crawler link 30 to communicate in the width direction Y. The seat forming parts 47 are formed on the plate surface 41 side of the first connecting part 45 and the second connecting part 46. The through holes 48 pass from the plate surface 41 to the seat forming part 47, and the bolt members 34b are arranged therein. The seat forming parts 47 include the seat surfaces 47s and the bosses 290. The seating surfaces 47s have the through holes 48 formed therein, and the nut members 34a, which are fastened with the bolt members 34b, are arranged therein.The projections 290 are provided on the seat forming parts 47, near the corner 47a from the corners 47a and 47b at both ends of the seat forming parts 47 in the width direction Y. The projections 290 are formed from the walls 55a and 55b provided on both sides of the first connecting part 45 in the connecting direction X. The projections 290 are formed from the walls 55b and 55c provided on both sides of the second connecting part 46 in the connecting direction X. The edges 290e of the projections 290 and the corners 47a and 47b at both ends of the seat forming parts 47 are formed in a rounded shape. A fiber path is formed toward the position P1 near the corner 47a (one of the corners 47a and 47b at both ends of the seat forming parts 47 in the width direction Y) on the seat forming parts 47. 3-2

[0138] In the track link 30 in this embodiment, the projections 290 limit the rotation of the nut elements 34a. Thus, the stepped portions 49 act as locks for the nut elements 34a.

[0139] Thus, rounding the corners 47a and 47b at both ends of the seat forming parts 47 and the edges 290e of the boss 290 reduces the concentration of stress and reduces cracking and the like during heat treatment.

[0140] Likewise, the projections 290 that prevent rotation of the nut members 34a can be formed by leaving a portion of the burr in removing the burr left in the forming step, so that there is no need for broaching or other such post-machining to form the projections 290, which keeps the manufacturing cost lower. 3-3

[0141] The crawler link 230 in Embodiment 2 further includes the projection 291. The projection 291 is formed to project outward from the lugs 290. The corner 47a formed near the lugs 290 of the seat forming members 47 is provided on the projection 291.

[0142] Thus, rounding the corner 47a formed on the projection 291 reduces the concentration of stress. 3-4

[0143] The crawler link 230 in Embodiment 2 further includes the groove tracks 292. The groove tracks 292 are formed on the inner side of the boss 290 to correspond to the projection 291.

[0144] The groove marks 292 are formed when the seat surface 47s' is scraped, and the chips generated by this scraping accumulate in the groove 262. Forming this groove 262 for collecting the chips allows the seat surfaces to be scraped accurately without being disturbed by the scraping. 3-5

[0145] The method for manufacturing the crawler link 230 in Embodiment 2 is a method for manufacturing a plurality of crawler links to be looped together for use in the hydraulic excavator 100 (an example of a work vehicle), each having seat forming parts 47 including seat surfaces 47s in which nut members 34a fixed to a link plate 33 are arranged, the method comprising a step S40 (an example of a forming step) and a step S50 (an example of a burr removing step).

[0146] In step S40 (an example of a forming step), the seat surfaces 47s' are formed at an angle to the forging direction Z, and at least the second inner burr portion 72 (an example of a burr portion) and the third inner burr portion 73 are formed on the seat forming parts 47' near the corner 47a (out of the corners 47a' and 47b' at both ends of the seat forming parts 47') in the width direction Y perpendicular to the connecting direction X of the crawler link 30', thereby producing a blank 261 (an example of a crawler link material) in which the corners 47a' and 47b' at both ends are formed in a rounded shape. In step S50 (an example of a burr removing step), part or all of the burr 62 is removed from the blank 261 (an example of a crawler link material) formed in step S40 (an example of a forming step).

[0147] As a result of the forging direction Z thus inclining with respect to the seat surfaces 47s' and also the formation of the second inner ridge portion 72 and the third inner ridge portion 73 in the vicinity of the corner 47a' at the end of the seat forming part 47', there are, as shown in Fig. 15a and Fig. 15b, unlike when the forging direction Z is aligned with the seating surfaces 1047s', there is no need for a die slope in the seating portion, and no burr is formed on the seating surfaces 47s'. Consequently, the seating surfaces 47s' can be formed in a plane. Likewise, broaching does not need to be performed after forming, and in this embodiment, instead of broaching, for example, only shaving needs to be performed along with burr removal, and this reduces costs. 3-6

[0148] In the method for manufacturing the crawler link 230 in Embodiment 2, the burr removal tool 80 used in step S50 (an example of a burr removal step) includes the burr cutting edge 2812a (an example of a burr removal edge) and the scraping edge 2812b. The burr cutting edge 2812a removes the second inner burr portion 72 (an example of a burr) on the seat formation parts 47. The scraping edge 2812b scrapes the seat surfaces 47s'.

[0149] Since the burr removal step and scraping can be performed at the same time, manufacturing will take less time. 3-7

[0150] In the method for manufacturing the crawler link 230 in Embodiment 2, in step S50 (an example of a burr removal step), a part of the second inner burr portion 72 (an example of a burr portion) is left to restrict the rotation of the nut members 34a, and material shaved off from the blank 261 (an example of a crawler link material) by shaving accumulates in the grooves 262 formed in a portion of the second inner burr portion 72 of the blank 261 along the seating surfaces 47s'. Consequently, the chips generated by the shaving accumulate in the grooves 262. Thus, forming the chip collecting grooves 262 enables the seating surfaces to be accurately shaved without being affected by the chips. 3-8

[0151] In the method for manufacturing the crawler track link 230 in Embodiment 2, in step S40 (an example of a forming step), the second outer peripheral burr portion 702 (an example of a burr portion) on the plate surface 41', which is in contact with the link plate 33 and opposing seat surfaces 47s', is formed closer to the corner 41a' (an example of a first corner) out of the corner 41a' (an example of a first corner) and the corner 41b' (an example of a second corner) at both ends in the width direction Y of the plate surface 41' (see Fig. 19). The burr removal tool 80 includes a first die 81 having a burr punching edge 812a (an example of a burr removal edge) and a stripping edge 812b, and a second die 82 corresponding to the first die 81. In step S50 (an example of a burr removal step), the blank 61 (an example of a track link material) is arranged in the second die 82 such that the corner 41a' is arranged on the first die 81 side and the corner 41b' is arranged on the second die 82 side.

[0152] Thus, forming the second outer peripheral ridge portion 702 closer to an end side on the plate surface 41', which is on the opposite side from the seating surfaces 47s', ensures that a surface S1 (see Fig. 19) via which the load exerted on the seating surfaces 47s' during scraping of the seating surfaces 47s' in the thrust direction is supported. Other embodiments

[0153] An embodiment of the present invention has been described above, but the present invention is not limited to or by the above embodiment, and various modifications are possible without departing from the gist of the invention. (A) Examples of a work vehicle include a hydraulic excavator, a bulldozer, a wheel loader, etc. (B) In the above embodiments 1 and 2, two seats and two connecting parts (the first connecting part 45 and the second connecting part 46) were formed, but only one connecting part may be formed, or three or more connecting parts may be formed. (C) In Embodiment 1, in the first connecting part 45, the stepped parts 49 were formed from both of the walls 55a and 55b, but they may be formed from only one or the other wall. In other words, the stepped part 49 should function as locks for the nut elements 34a. Similarly, in the second connecting part 46, the stepped parts 49 may be formed from only the wall 55b or 55c. (D) In ​​the crawler link 230 of Embodiment 2, the concave groove marks 292 are visible, but the grooves 262 may be filled with chips so that the groove marks are not visible. The groove marks 292 may also be formed above the surface. (E) In Embodiment 2, the projection 290 in the first connecting part 45 extends up to the walls 55a and 55b, but it may be interrupted in the middle. In other words, the projection 290 should function as a lock for the nut elements 34a. Similarly, the projection 290 in the second connecting part 46 may be interrupted in the middle from the wall 55b to the wall 55c. (F)

[0154] In the above embodiment 1, the stepped part 49 was provided up to the seat forming part 47, and in the embodiment 2, the projection 290 was provided, both of which function as locks for the nut elements, but these are not the only options. For example, as in the oblique view in Fig. 20a, the curved surface 390 may be formed on the seat forming part 47. Fig. 20b is a front view of the crawler link 330. Fig. 20c is a detailed view of the area near the curved surface 390 of the first connecting part 45.

[0155] As in Fig. 20a and Fig. 20b, the curved surfaces 390 are formed instead of the stepped parts 49 on the seat forming parts 47 of the crawler link 330. As shown in Fig. As shown in Fig. 20c, the curved surface 390 is provided within the first connecting part 45 to form a part of an imaginary cylinder N having a central axis M along the width direction Y. Part of the curved surface 390 (or the entire surface) forms the seat surface 47s, and a through hole 48 is provided therein. The corners 47a and 47b (see Fig. 20a) at both ends in the width direction Y of the seat forming part 47 are formed in a rounded shape. A fiber direction is formed toward a position near the corner 47a.

[0156] The crawler chain link 330 is produced in the same way as in embodiments 1 and 2, with the forging direction at an angle to the seating surfaces 47s.

[0157] Fig. 21a and Fig. 21b are oblique views of a nut element 350 used in the crawler link 330. As in Fig. 21a and Fig.As shown in Fig. 21b, the nut member 350 is in the approximate shape of a hexagonal prism, on the bottom of which a curved surface 350c is formed that curves convexly downward. The curved surfaces 350c are formed to coincide with the curved surfaces 390 of the seat forming parts 47 of the first connecting part 45 and the second connecting part 46. That is, in a state where the curved surfaces 350c of the nut members are arranged on the seat surfaces 47s, the curved surfaces 350c are provided to form part of the side surfaces of imaginary cylinders N having a central axis M along the width direction Y.

[0158] In a state where the nut member 350 is disposed on the seat surface 47s of the first connecting part 45, an opposite side surface 350s arranged parallel to the central axis M is opposed to the walls 55a and 55b. In a state where the nut member 350 is disposed on the seat surface 47s of the second connecting part 46, the opposite side surface 350s arranged parallel to the central axis M is opposed to the walls 55b and 55c.

[0159] When the nut member 350 is brought together with the seat surface 47d so that the curved surface 350c and the curved surface 390 face each other, the rotation of the nut members 350 is restricted when the curved surface 350c abuts the curved surface 390 of the crawler link 330 and the side surface 350s abuts the walls 55a, 55b, and 55c. INDUSTRIAL APPLICABILITY

[0160] The crawler track link and the method for manufacturing a crawler track link of the present invention have the effect of reducing stress concentration and as such are useful in that they can be used in work vehicles, etc. REFERENCE SYMBOL LIST 2 drive unit 3 vehicle body 20 caterpillar tracks 21 chain frames 22 wheel 23 sprocket 23a Sprocket teeth 23b Final reduction gear 24 carrier roll 25 crawler roller 25a projection 30 track links 30' track link 31 socket 32 connecting bolts 33 Chain link plate 34a Nut element 34b Bolt element 35 Sealing element 41 plate area 41a' Corner 41b' Corner 41' record surface 42 tread 42a corner 42' running surface 43 first connecting part 43a' front side 43' first connecting part 44 second connecting part 44a' front side 44' second connecting part 45 first connecting part 45' first connecting part 46 second connecting part 46' second connecting part 47 Seating part 47a corner 47a' Corner 47b corner 47b' Corner 47s seat 47s' seat 47' seating section 48 through hole 49 stepped part 49a corner 49a' Corner 49' stepped section 51 first area part 52 second area part 53 first side surface part 53' first side surface part 54 second side panel part 55a Wall 55b Wall 55c wall 60a upper die 60b lower die 61 molded parts 62 ridge 70 outer peripheral ridge section 71 first inner ridge section 72 second inner ridge section 73 third inner ridge section 74 fourth inner ridge section 80 Burr removal tool 81 first die 82 second die 100 hydraulic excavators 230 track link 251 rotating shaft 261 molding 262 groove 290 approach 290a corner 290e Rand 291 lead 292 groove track 431 bushing hole 431' socket hole 441 bolt hole 441a Large diameter part 441b Small diameter part 441b' Small diameter part 441' bolt hole 601a upper die 601b lower die 602b Seating area 701 first outer circumferential ridge section 702 second outer circumferential ridge section 703 third outer circumferential ridge section 704 fourth outer circumferential ridge section 810 outer peripheral part Room 810a 811 first stamp 812 second stamp 812a Burr punching cutter 812b stripping edge 813 third stamp 814 fourth stamp 820 plate-like element 821 placement room 822 support frame 822a first support frame part 822b second support frame part 822c ​​third support frame part 822d fourth support frame part 1047s' seat 1047' Seating formation part 1061 molding 2812 second stamp 2812a Burr punch cutter 2812b stripping edge 2812c main body

Claims

[1] A crawler track link (230), a number of which are connected to one another in a loop-like manner for use in a crawler track (20) of a work vehicle, the crawler track link (230) comprising: a running surface (42) adapted to come into contact with a roller (24, 25) for a landing gear; a plate surface (41) provided on a side opposite the tread (42) and to which a chain link plate (33) can be attached; a connecting part (45, 46) provided between the plate surface (41) and the tread (42) while passing in a width direction (Y) perpendicular to the connecting direction (X), and configured to allow side surfaces of the crawler link (230) to connect in the width direction (Y); a seat forming part (47) formed on the plate surface side (41) of the connecting part (45, 46); and a through hole (48) extending from the plate surface (41) to the seat forming part (47) and in which a bolt element (34b) can be arranged, wherein the seat forming part (47) comprises: a seat surface (47s) in which the through hole (48) is formed and on which a nut element (34a) connected to the bolt element (34b) can be arranged, and characterized by that the seat forming part (47) comprises a projection (290) formed on the seat forming part (47) near one of the corners (47a) at the ends of the seat forming part (47) in the connecting direction (X) from the walls (55a, 55b) provided on the sides of the connecting part (45, 46) in the connecting direction (X); the corners (47a, 47b) of the ends of the seat forming part (47) and a corner (47a) of the extension (290) are formed in a rounded shape; and a fiber path formed toward a position (P1) that is at the seat forming part (47) and near one of the corners (49a) at the ends of the seat forming part (47) in the width direction (Y). [2] A crawler track link according to claim 1, wherein the lug (290) limits the rotation of the nut member (34a). [3] Caterpillar track link according to claim 1, further comprising a projection (291) projecting outwardly from the extension (290), wherein the corner (47a) is provided on the projection (291) in the vicinity of the boss (290) formed on the seat forming part (47). [4] A crawler track link according to claim 3, further comprising a groove track (292) formed on the inner side of the boss (290) to correspond to the projection (291). [5] A crawler track link (330), a number of which are connected to one another in a loop-like manner for use in a crawler track (20) of a work vehicle, the crawler track link (330) comprising: a running surface (42) adapted to come into contact with a roller (24, 25) for a landing gear; a plate surface (41) provided on a side opposite the tread (42) and to which a chain link plate (33) can be attached; a connecting part (45, 46) provided between the plate surface (41) and the tread (42) while passing in a width direction (Y) perpendicular to a connecting direction (X), and configured to allow side surfaces of the crawler link (330) to connect in the width direction (Y); a seat forming part (47) having a curved surface shape (390) to form a part of a side surface of an imaginary circular column having a central axis along the width direction (Y), and formed on the plate surface side (41) of the connecting part (45, 46); and a through hole (48) extending from the plate surface (41) to the seat forming part (47) and in which a bolt element (34b) can be arranged, characterized by Corners (47a, 47b) at the ends of the seat forming part (47) in the connecting direction (X) which are formed in a rounded shape; and a fiber path formed toward a position (P1) that is on the seat forming part (47) and near one of the corners (47a) at the ends of the seat forming part (47) in the width direction (Y). [6] Caterpillar track link according to claim 5, wherein the seat forming part (47) has a seat surface (47s) on which a nut element (350) is arranged, which is fastened to the bolt element (34b), and wherein the nut element (350) has a shape such that its contact surface with the seat surface coincides with the curved surface shape (390). [7] A method for producing a crawler track link (30; 230; 330), a number of which are looped together for use on a work vehicle, the crawler track link (30; 230; 330) comprising a seat forming part (47) having a seat surface (47s) on which a nut element (34a; 350) is arranged to be fixed to track link plates (33), the crawler track link (30; 230; 330) being formed by forging, the method for producing a crawler track link (30; 230; 330) comprising: a forming step for producing a crawler link material in which the seat surface (47s) is formed at an angle to a forging direction, a burr (62) is formed on the seat forming part (47) near one of the corners (47a, 47b) at the ends of the seat forming part (47) in a width direction (Y) perpendicular to a connecting direction (X) of the crawler link (30; 230; 330), and the corners (47a, 47b) at the ends are formed in a rounded shape; and a burr removing step of removing part or all of the burr (62) of the crawler link material formed by the forming step. [8] A method for producing a crawler track link according to claim 7, wherein a burr removal tool (80) used in the burr removal step comprises: a burr removal blade (2812a) for deburring the seat forming part (47); and a scraper blade (2812b) for performing a scraper treatment on the seat surface (47s), and wherein in the burr removal step, the stripping treatment is also carried out on the seating surfaces (47s). [9] A method of manufacturing a crawler track link according to claim 7, wherein a part of the burr (62) is left in the burr removing step to limit rotation of the nut member (34a; 350). [10] A method for producing a crawler track link according to claim 8, wherein in the burr removal step a part of the burr (62) is left to limit rotation of the nut element (34a; 350), and Material scraped off by the scraping treatment of the crawler link material accumulates in a groove (262) formed in a portion of the ridge (62) of the crawler link material along the seat surface (47s). [11] A method of manufacturing a crawler track link according to claim 8, wherein in the forming step, a ridge (62) is formed on the plate surface (41) which comes into contact with the chain link plate (33) and is opposite to the seat surface (47s) and closer to a first corner from the first corner and a second corner at the ends in the width direction (Y) of the plate surface (41), the burr removal tool comprises a first die (81) with a burr cutting edge (2812a) and a stripping edge (2812b) and a second die (82) corresponding to the first die (81), and in the burr removing step, the crawler link material is arranged in the second die (82) such that the first corner is arranged on the first die side and the second corner is arranged on the second die side.

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