Transmission mechanism for work machine, shift fork, and method of manufacturing shift fork

Abstract

The present disclosure pertains to: a transmission mechanism for a work machine; a shift fork; and a method of manufacturing a shift fork. A transmission mechanism 10 is provided with: a countershaft 32 and a shift shaft 56 that are parallel to one another; a first coupling sleeve 41 and a second coupling sleeve 42 that can be displaced along the countershaft 32; and a shift fork 50 comprising a sleeve 53 that can be displaced along the shift shaft 56, a first arm 51 that engages with the first coupling sleeve 41, and a second arm 52 that engages with the second coupling sleeve 42. The shift fork 50 is configured by joining a first member 50A and a second member 50B together. The first member 50A includes a first sleeve 53A constituting one axial side of the sleeve 53, and the first arm 51 which is provided to the first sleeve 53A. The second member 50B includes a second sleeve 53B constituting the other axial side of the sleeve 53, and the second arm 52 which is provided to the second sleeve 53B.

Description

Transmission mechanism for work machine, shift fork, and method for manufacturing shift fork

[0001] The present application claims priority to Japanese Patent Application No. 2023-214710, filed December 20, 2023, and incorporates by reference all of the contents of that application.

[0002] A known transmission for a work machine is disclosed in Patent Document 1. The transmission mechanism includes an auxiliary transmission mechanism including a pair of coupling sleeves. The auxiliary transmission mechanism synchronously displaces the pair of coupling sleeves to select a gear position corresponding to the displacement position. The auxiliary transmission mechanism further includes a shift fork for displacing the pair of coupling sleeves. The shift fork includes a first arm that engages with one of the coupling sleeves, a second arm that engages with the other of the coupling sleeves, and a cylindrical sleeve that connects the two arms. The shift fork configured in this manner can synchronously displace the pair of arms by displacing the sleeve. The work machine disclosed in Patent Document 1 is a combine harvester.

[0003] Japanese Patent Application Laid-Open No. 2018-204635

[0004] A transmission mechanism for a work machine according to one aspect of the present disclosure is a transmission mechanism for a work machine comprising a first axis and a second axis that are parallel to each other, a first coupling sleeve and a second coupling sleeve that are displaceable along the first axis, a sleeve that is displaceable along the second axis, a first arm that is provided on the sleeve and engages with the first coupling, and a second arm that is provided on the sleeve and engages with the second coupling sleeve, wherein the shift fork is formed by connecting a first member that constitutes one axial side and a second member that constitutes the other axial side, the first member including the first sleeve that constitutes one axial side of the sleeve and the first arm that is provided on the first sleeve, and the second member including a second sleeve that constitutes the other axial side of the sleeve and the second arm that is provided on the second sleeve.

[0005] A shift fork according to one aspect of the present disclosure is a shift fork comprising a sleeve through which a shaft is inserted and a pair of arms provided on one axial side and the other axial side of the sleeve, wherein the shift fork is configured by joining a first member constituting the one axial side and a second member constituting the other axial side, the first member including a first sleeve constituting the one axial side of the sleeve and a first arm provided on the first sleeve, and the second member including a second sleeve constituting the other axial side of the sleeve and a second arm provided on the second sleeve.

[0006] A manufacturing method of a shift fork according to one aspect of the present disclosure is a manufacturing method of a shift fork including a sleeve through which a shaft is inserted and a pair of arms provided on one axial side and the other axial side of the sleeve, and includes: a first step of creating a common original member that is the basis for a first member that constitutes the one axial side of the shift fork and a second member that constitutes the other axial side; and a second step of processing the original member to create the first member including a first sleeve that constitutes the one axial side of the sleeve and a first arm provided on the first sleeve, and the second member including a second sleeve that constitutes the other axial side of the sleeve and a second arm provided on the second sleeve.

[0007] According to the present disclosure, the manufacturing costs of a shift fork having a pair of arms can be reduced.

[0008] FIG. 1 is a skeleton diagram showing a transmission mechanism of a work machine according to an embodiment of the present disclosure. FIG. 2 is a partially enlarged view showing an auxiliary transmission mechanism. FIG. 3A is a schematic diagram showing a shift fork. FIG. 3B is a schematic diagram showing a shift fork. FIG. 4A is an exploded perspective view showing a first member and a second member before assembly. FIG. 4B is an exploded perspective view showing the first member and the second member before assembly. FIG. 4C is a perspective view showing the shift fork (the first member and the second member after assembly). FIG. 5 is a partially enlarged view showing a first connecting portion and a second connecting portion. FIG. 6 is an explanatory diagram of a manufacturing method for the first member. FIG. 7 is an explanatory diagram of a manufacturing method for the second member.

[0009] <Problem to be Solved by the Invention> When manufacturing the shift fork having a pair of arms by casting, it is necessary to use a complex mold with two or more punch directions. In other words, it is difficult to manufacture the shift fork using a simple mold with a single punch direction. For this reason, it is difficult to reduce the cost of the shift fork having a pair of arms.

[0010] An object of the present disclosure is to reduce the manufacturing costs of a shift fork having a pair of arms.

[0011] Effect of the Invention According to the transmission mechanism for a work machine, the shift fork, and the method for manufacturing a shift fork of the present disclosure, it is possible to reduce the manufacturing costs of a shift fork having a pair of arms.

[0012] <Summary of Embodiments of the Present Disclosure> The following is a summary of embodiments of the present disclosure. (1) A transmission mechanism for a work machine according to the present disclosure includes a first shaft and a second shaft parallel to each other, a first coupling sleeve and a second coupling sleeve displaceable along the first shaft, a sleeve displaceable along the second shaft, a first arm provided on the sleeve and engaging with the first coupling, and a second arm provided on the sleeve and engaging with the second coupling sleeve. The shift fork is configured by connecting a first member constituting one axial side and a second member constituting the other axial side. The first member includes the first sleeve constituting one axial side of the sleeve and the first arm provided on the first sleeve. The second member includes a second sleeve constituting the other axial side of the sleeve and the second arm provided on the second sleeve.

[0013] According to the above configuration, the first member and the second member can be manufactured using a simple mold with a single punching direction, and the shift fork can be manufactured using the first member and the second member, thereby reducing the manufacturing cost of the shift fork having a pair of arms.

[0014] (2) In the transmission mechanism for a work machine according to the above aspect (1), it is preferable that the first sleeve has a first connecting portion that connects the second member, and the second sleeve has a second connecting portion that connects the first member, and the first connecting portion and the second connecting portion connect to each other. According to this configuration, the first member and the second member can be connected without using a separate connecting member. This reduces the manufacturing cost of the shift fork that connects the first member and the second member.

[0015] (3) In the transmission mechanism for a work machine according to the above-described (1) or (2), it is preferable that the first coupling portion has a first convex portion that convex in the radial direction of the first sleeve and a first concave portion that concaves in the direction opposite to the convex direction of the first convex portion, and the second coupling portion has a second convex portion that convex in the radial direction of the second sleeve and fits into the first concave portion, and a second concave portion that concaves in the direction opposite to the convex direction of the second convex portion and fits into the first convex portion. According to this configuration, a shift fork formed by the first member and the second member can reliably transmit forces acting toward one and the other axial sides to the first coupling sleeve and the second coupling sleeve. This makes it possible to reliably displace the first coupling sleeve and the second coupling sleeve toward one and the other axial sides.

[0016] (4) Preferably, the transmission mechanism of the work machine according to any one of (1) to (3) further includes a shift mechanism that displaces the shift fork in the axial direction of the second shaft, the shift fork having an engaging portion that engages with the shift mechanism, the engaging portion being provided on either the first member or the second member. According to this configuration, the engaging portion can be easily provided on the shift fork that is formed by the first member and the second member.

[0017] (5) The transmission mechanism of the work machine according to any one of (1) to (4) above preferably further includes a detent mechanism that holds the shift fork at a predetermined position in the axial direction of the second shaft, the detent mechanism including a ball and an elastic member, and one of the first member and the second member preferably including a housing portion that houses the ball and the elastic member. According to this configuration, a detent mechanism can be easily provided in a shift fork that is formed of the first member and the second member.

[0018] (6) A shift fork according to the present disclosure includes a sleeve through which a shaft is inserted, and a pair of arms provided on one axial side and the other axial side of the sleeve. The shift fork is configured by joining a first member that constitutes the one axial side and a second member that constitutes the other axial side. The first member includes a first sleeve that constitutes the one axial side of the sleeve, and a first arm that is provided on the first sleeve. The second member includes a second sleeve that constitutes the other axial side of the sleeve, and a second arm that is provided on the second sleeve.

[0019] According to the above configuration, the shift fork can be manufactured using the first member and the second member that can be manufactured using a simple mold with a single punching direction, thereby reducing the manufacturing cost of the shift fork having a pair of arms.

[0020] (7) In the shift fork according to the aspect (6), it is preferable that the first sleeve has a first coupling portion that couples the second member, and the second sleeve has a second coupling portion that couples the first member, and the first coupling portion and the second coupling portion couple to each other. This configuration allows the first member and the second member to be coupled without using a separate coupling member. This reduces the manufacturing cost of the shift fork configured by coupling the first member and the second member.

[0021] (8) In the shift fork according to the above aspect (6) or (7), it is preferable that the first coupling portion is provided at an end on the other axial side of the first sleeve and has a first convex portion that convex in a radial direction of the first sleeve and a first concave portion that concaves in a direction opposite to the convex direction of the first convex portion, and the second coupling portion is provided at an end on one axial side of the second sleeve and has a second convex portion that convex in a radial direction of the second sleeve and fits into the first concave portion, and a second concave portion that concaves in a direction opposite to the convex direction of the second convex portion and fits into the first convex portion. With this configuration, the first member and the second member can be reliably coupled together with a simple configuration.

[0022] (9) In the shift fork according to any one of (6) to (8), the first coupling portion preferably has a first surface that is a side surface on the other axial side of the first convex portion, a second surface that is a side surface on one axial side of the first convex portion and a side surface on the other axial side of the first recess, and a third surface that is a side surface on one axial side of the first recess, and the second coupling portion preferably has a fourth surface that is a side surface on one axial side of the second convex portion, a fifth surface that is a side surface on the other axial side of the second convex portion and a side surface on one axial side of the second recess, and a sixth surface that is a side surface on the other axial side of the second recess, and the first surface and the sixth surface, the second surface and the fifth surface, and the third surface and the fourth surface preferably face each other. According to the above configuration, a force acting on one axial side and the other axial side can be reliably transmitted by a shift fork constituted by a first member and a second member.

[0023] (10) In the shift fork according to any one of (6) to (9), the first member and the second member preferably have the same shape. According to this configuration, the number of parts of the shift fork formed by joining the first member and the second member can be reduced, thereby reducing the manufacturing cost of the shift fork.

[0024] (11) A manufacturing method of a shift fork according to the present disclosure is a manufacturing method of a shift fork including a sleeve through which a shaft is inserted and a pair of arms provided on one axial side and the other axial side of the sleeve. The manufacturing method of a shift fork according to the present disclosure includes: a first step of producing a common original member that is the basis for a first member that constitutes the one axial side of the shift fork and a second member that constitutes the other axial side of the shift fork; and a second step of processing the original member to produce the first member including a first sleeve that constitutes the one axial side of the sleeve and a first arm provided on the first sleeve, and the second member including a second sleeve that constitutes the other axial side of the sleeve and a second arm provided on the second sleeve.

[0025] According to the above configuration, the first member and the second member can be created from an original member that can be manufactured using a simple mold with a single punching direction, and the shift fork can be manufactured using these members, thereby reducing the manufacturing costs of the shift fork having a pair of arms.

[0026] (12) In the shift fork manufacturing method according to the above aspect (11), the first member has a first connecting portion that connects to the second member, the second member has a second connecting portion that connects to the first member, and the base member has a processed portion that is to be processed into the first connecting portion or the second connecting portion, and the second step preferably includes a step of performing a first process on the processed portion to produce the first member, and a step of performing a second process on the processed portion to produce the second member. According to this configuration, only one type of base member can be manufactured using a simple mold with a single punching direction, and the base member can be subjected to the first process to manufacture the first member and the second process to manufacture the second member. This reduces the manufacturing costs of a shift fork having a pair of arms.

[0027] (13) In the shift fork manufacturing method according to the above (11) or (12), it is preferable that the original material further has a second processed portion that is processed into an engaging portion that engages with a shift mechanism that displaces the sleeve in the axial direction, and that either the first processing or the second processing includes processing that removes at least a portion of the second processed portion. According to this configuration, an engaging portion can be easily provided in a shift fork manufactured from a single type of original material.

[0028] (14) In the method for manufacturing a shift fork according to the above-described (11) or (12), it is preferable that the first processing and the second processing are the same processing, and the first member and the second member have the same shape. According to this configuration, a base member can be manufactured using a simple mold with a single punching direction, and the first member and the second member can be manufactured from this base member. This reduces the manufacturing cost of a shift fork having a pair of arms.

[0029] (15) In the method for manufacturing a shift fork according to any one of (11) to (14), the first step preferably includes a step of producing the base member by casting. According to this configuration, the base member is manufactured using a simple mold with a single punching direction, and the base member is subjected to a first processing step to manufacture a first member, and then subjected to a second processing step to manufacture a second member, thereby manufacturing the shift fork. This reduces the manufacturing costs of a shift fork having a pair of arms.

[0030] <Details of the embodiments of the present disclosure> Hereinafter, the details of the embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0031] [Overall Configuration of Transmission Mechanism] FIG. 1 is a skeleton diagram showing a transmission mechanism of a work machine according to one embodiment of the present disclosure. FIG. 2 is a partially enlarged view showing the auxiliary transmission mechanism. FIG. 1 shows a transmission mechanism 10 according to one embodiment of the transmission mechanism of a work machine according to the present disclosure. The transmission mechanism 10 shown in this embodiment is a transmission mechanism (transmission) for a combine harvester, which is an example of a work machine. As shown in FIG. 1, the transmission mechanism 10 includes a main transmission mechanism 20, an auxiliary transmission mechanism 30, a clutch mechanism 60, a drive mechanism 70, and a shift mechanism 80. Note that the transmission mechanism of a work machine according to the present disclosure may also be a transmission mechanism for a work machine other than a combine harvester.

[0032] [Main Transmission Mechanism] In the transmission mechanism 10 of this embodiment, the main transmission mechanism 20 is configured by a hydrostatic continuously variable transmission (HST). The main transmission mechanism 20 includes an input shaft 21 and an output shaft 22. The main transmission mechanism 20 adjusts the driving force (rotational force) input from a prime mover such as an engine via the input shaft 21 using a planetary gear mechanism (not shown) or the like, and outputs the driving force from the output shaft 22 after adjusting the rotation speed, rotation direction, etc. It should be noted that the main transmission mechanism in the transmission mechanism of the present disclosure is not limited to this configuration.

[0033] [Auxiliary Transmission Mechanism] The auxiliary transmission mechanism 30 further changes the speed (adjusts the rotation speed) of the driving force output from the main transmission mechanism 20. As shown in FIG. 2, the auxiliary transmission mechanism 30 is housed inside the transmission case 11. As shown in FIGS. 1 and 2, the auxiliary transmission mechanism 30 includes an input shaft 31 and a countershaft 32. The input shaft 31 is coaxially connected to the output shaft 22 and rotates integrally with the output shaft 22. The input shaft 31 includes an input gear 33 including a low-speed gear 33a, a high-speed gear 33b, and a medium-speed gear 33c. The low-speed gear 33a, the high-speed gear 33b, and the medium-speed gear 33c are fixed on the input shaft 31. The low-speed gear 33a, the high-speed gear 33b, and the medium-speed gear 33c rotate integrally with the input shaft 31 (output shaft 22).

[0034] The subtransmission mechanism 30 further includes a first coupling sleeve 41 and a second coupling sleeve 42. The first coupling sleeve 41 and the second coupling sleeve 42 are configured to be displaceable along the countershaft 32 (in other words, in the axial direction of the countershaft 32). The subtransmission mechanism 30 selects a gear position (one of low speed, medium speed, high speed, and neutral) in accordance with the displacement of the first coupling sleeve 41 and the second coupling sleeve 42. The first coupling sleeve 41 and the second coupling sleeve 42 are displaced synchronously along the countershaft 32 in accordance with the displacement of a shift fork 50, which will be described later.

[0035] The counter shaft 32 is disposed parallel to the input shaft 31. The counter shaft 32 includes a first gear 34, a second gear 35, a third gear 36, a first coupling gear 37, a second coupling gear 38, and a counter gear 39.

[0036] The first gear 34 includes a first input gear 34a, a first output gear 34b, and a first gear shaft 34c. The first gear shaft 34c is cylindrical and rotatably supported on the counter shaft 32. The first input gear 34a meshes with the low-speed gear 33a. The first output gear 34b is configured to mesh with a first coupling sleeve 41.

[0037] The second gear 35 includes a second input gear 35a, a second output gear 35b, and a second gear shaft 35c. The second gear shaft 35c is cylindrical and rotatably supported on the counter shaft 32. The second input gear 35a meshes with the high-speed gear 33b. The second output gear 35b is configured to be able to mesh with the first coupling sleeve 41.

[0038] The third gear 36 includes a third input gear 36a, a third output gear 36b, and a third gear shaft 36c. The third gear shaft 36c is cylindrical and rotatably supported on the counter shaft 32. The third input gear 36a meshes with the medium speed gear 33c. The third output gear 36b is configured to be able to mesh with the second coupling sleeve 42.

[0039] The first coupling gear 37, the second coupling gear 38, and the counter gear 39 are fixed on the axis of the counter shaft 32. The first coupling gear 37, the second coupling gear 38, and the counter gear 39 rotate integrally with the counter shaft 32.

[0040] The first coupling sleeve 41 is configured to be displaceable along the countershaft 32 within an axial range in which the first output gear 34b, the first coupling gear 37, and the second output gear 35b are located. The first coupling gear 37 is disposed adjacent to the first output gear 34b. The first coupling gear 37 and the first output gear 34b are configured to be able to mesh with the first coupling sleeve 41. When the first coupling sleeve 41 is displaced to a position spanning the first coupling gear 37 and the first output gear 34b, the first coupling gear 37 and the first output gear 34b are connected by the first coupling sleeve 41. At this time, the first gear 34 can rotate integrally with the counter gear 39, and the driving force transmitted from the low-speed gear 33a to the first gear 34 is transmitted to the countershaft 32 via the first coupling gear 37. At this time, the subtransmission mechanism 30 is in a state in which "low speed" is selected. When the first coupling sleeve 41 is displaced to a position other than the position where it straddles the first coupling gear 37 and the first output gear 34b, the first coupling gear 37 and the first output gear 34b are disengaged from each other. At this time, the first coupling gear 37 and the first output gear 34b are not involved in the transmission of driving force.

[0041] The first coupling gear 37 is further disposed adjacent to the second output gear 35b. The second output gear 35b is configured to be able to mesh with the first coupling sleeve 41. When the first coupling sleeve 41 is displaced to a position spanning the first coupling gear 37 and the second output gear 35b, the first coupling gear 37 and the second output gear 35b are connected by the first coupling sleeve 41. At this time, the second gear 35 can rotate integrally with the counter gear 39, and the driving force transmitted from the high-speed gear 33b to the second gear 35 is transmitted to the counter shaft 32 via the first coupling gear 37. At this time, the subtransmission mechanism 30 is in a state in which "high speed" is selected. When the first coupling sleeve 41 is displaced to a position other than the position spanning the first coupling gear 37 and the second output gear 35b, the first coupling gear 37 and the second output gear 35b are disengaged and are not involved in the transmission of driving force.

[0042] The second coupling sleeve 42 is configured to be displaceable along the countershaft 32 within an axial range in which the third output gear 36b and the second coupling gear 38 are located. The second coupling gear 38 is disposed adjacent to the third output gear 36b. The second coupling gear 38 and the third output gear 36b are configured to be able to mesh with the second coupling sleeve 42. When the second coupling sleeve 42 is displaced to a position in which it straddles the second coupling gear 38 and the third output gear 36b, the second coupling gear 38 and the third output gear 36b are connected by the second coupling sleeve 42. At this time, the third gear 36 can rotate integrally with the counter gear 39, and the driving force transmitted from the medium speed gear 33c to the third gear 36 is transmitted to the countershaft 32 via the second coupling gear 38. At this time, the subtransmission mechanism 30 is in a state in which the "medium speed" is selected. If the second coupling sleeve 42 is displaced to a position other than the position spanning the second coupling gear 38 and the third output side gear 36b, the second coupling gear 38 and the third output side gear 36b are disconnected and are no longer involved in the transmission of driving force.

[0043] In this way, the sub-transmission mechanism 30 changes the speed of the driving force according to the positions of the first coupling sleeve 41 and the second coupling sleeve 42, and outputs the driving force from the counter gear 39. Note that the sub-transmission mechanism 30 is in a "neutral" state when the first coupling sleeve 41 and the second coupling sleeve 42 are positioned so as not to straddle two gears. In this state, the sub-transmission mechanism 30 is in a state in which the driving force input to the input shaft 31 is not output from the counter shaft 32 (a so-called neutral state).

[0044] [Clutch Mechanism] The clutch mechanism 60 is a mechanism that selectively transmits the driving force output from the auxiliary transmission 30 to the left or right drive mechanism 70. The clutch mechanism 60 includes an input gear 62 fixed on an input shaft 61, a pair of left and right side clutches 63 (a first side clutch 63a and a second side clutch 63b), and a pair of left and right side gears 64 (a first side gear 64a and a second side gear 64b). The left and right side clutches 63a, 63b are fixed on the input shaft 61. When the first side clutch 63a is activated, the first side clutch 63a and the first side gear 64a are connected to each other, enabling the transmission of driving force. At this time, the first side clutch 63a transmits driving force to the drive mechanism 70 via the first side gear 64a. When the second side clutch 63b is activated, the second side clutch 63b and the second side gear 64b are connected to each other, enabling the transmission of driving force. At this time, the second side clutch 63b transmits the driving force to the drive mechanism 70 via the second side gear 64b.

[0045] [Drive Mechanism] The drive mechanism 70 transmits the drive force transmitted from the clutch mechanism 60 to a travel device (not shown) of the work machine. The speed change mechanism 10 of this embodiment is for a combine harvester, and the drive mechanism 70 drives the crawler-type travel device. The drive mechanism 70 includes a pair of left and right drive shafts 71 (first drive shaft 71a and second drive shaft 71b), a pair of left and right drive gears 72 (first drive gear 72a and second drive gear 72b) fixed to the drive shafts 71, and a pair of left and right drive wheels (sprockets) 73 (first drive wheel 73a and second drive wheel 73b). The drive wheels 73 drive endless crawlers (not shown). The drive mechanism 70 may further include a brake mechanism (not shown) that adjusts the drive force of each of the left and right drive shafts 71 (first drive shaft 71a and second drive shaft 71b).

[0046] When the driving force is transmitted from the clutch mechanism 60 to the first drive gear 72a, the drive mechanism 70 drives the first drive wheel 73a via the first drive shaft 71a. When the driving force is transmitted from the clutch mechanism 60 to the second drive gear 72b, the drive mechanism 70 drives the second drive wheel 73b via the second drive shaft 71b.

[0047] When both the left and right side clutches 63 a, 63 b of the clutch mechanism 60 are engaged, the transmission mechanism 10 can rotate the pair of left and right traveling devices at the same speed. This allows the working machine (combine) to travel straight. Furthermore, when only one of the first side clutch 63 a and the second side clutch 63 b is engaged, the transmission mechanism 10 can change the direction of the working machine (combine) to either the left or the right.

[0048] [Shift Mechanism] The shift mechanism 80 is a mechanism for selecting a gear position in the sub-transmission mechanism 30. The shift mechanism 80 of this embodiment includes an sub-transmission lever 81. The sub-transmission lever 81 is rotatably supported by a rotary shaft 82 and is disposed near a driver's seat of a work machine (not shown). The transmission mechanism 10 allows a user seated in the driver's seat to select a gear position of the sub-transmission mechanism 30 by rotating the sub-transmission lever 81. An end 83 of the sub-transmission lever 81 engages with the shift fork 50. The rotation of the sub-transmission lever 81 displaces the shift fork 50 along the shift shaft 56 (in the axial direction). The sub-transmission mechanism 30 is configured to be able to select a gear position (low speed, high speed, medium speed, or neutral) by displacing the shift fork 50 according to the rotational position of the sub-transmission lever 81.

[0049] 1 and 2, the subtransmission mechanism 30 includes a shift fork 50. As shown in FIGS. 1 and 2, the shift fork 50 includes a first arm 51, a second arm 52, and a sleeve 53. In other words, the shift fork 50 in the transmission mechanism 10 of the present disclosure has a structure in which the first arm 51 and the second arm 52 are connected by the sleeve 53.

[0050] The sleeve 53 has a shaft hole 54. A shift shaft 56 is inserted into the shaft hole 54 of the shift fork 50. The shift shaft 56 is supported by the transmission case 11 in an orientation parallel to the counter shaft 32. The shift fork 50 has an engaging portion 55. The engaging portion 55 has a groove 55a with which an end 83 of the auxiliary shift lever 81 engages. The shift fork 50 is configured to be displaceable along the shift shaft 56 (in the axial direction of the shift shaft 56). The configuration of the shift fork 50 will be described in detail later.

[0051] [Detent Mechanism] The subtransmission mechanism 30 further includes a detent mechanism 59. The detent mechanism 59 holds the shift fork 50 at a predetermined axial position of the shift shaft 56. The detent mechanism 59 includes a ball 59a, an elastic member 59b, a housing 59c formed in the sleeve 53, and a ring-shaped groove 56a formed in the outer peripheral surface of the shift shaft 56. The groove 56a is formed to correspond to the position of each housing 59c when the subtransmission lever 81 is rotated to each of the low-speed, high-speed, medium-speed, and neutral positions. For example, when the subtransmission lever 81 is rotated to the low-speed position, the housing 59c (ball 59a and elastic member 59b) of the detent mechanism 59 is positioned at a position corresponding to the low speed. At this time, the ball 59a fits into the groove 56a formed in the low-speed position, and the elastic member 59b presses the ball 59a. In this way, the detent mechanism 59 holds the shift fork 50 in the low-speed position. The detent mechanism 59 operates in the same way when the auxiliary speed change lever 81 is rotated to a position other than the low-speed position. Note that the detent mechanism 59 allows the shift fork 50 to move in the axial direction when a force equal to or greater than a predetermined force acts on the shift fork 50 in the axial direction of the shift shaft 56.

[0052] [Detailed Configuration of the Shift Fork] Figures 3A and 3B are schematic diagrams showing the shift fork. Figures 4A and 4B are exploded perspective views showing the first member and the second member before assembly. Figure 4C is a perspective view showing the shift fork (the first member and the second member after assembly). Figure 5 is a partially enlarged view showing the first connecting portion and the second connecting portion. Note that Figure 3A shows the shift fork 50 when viewed from the same direction as Figure 2, and Figure 3B shows the shift fork 50 when viewed from the opposite side of Figure 3A. The perspective views of Figures 4A and 4B show the shift fork 50 from different angles and viewpoints. Figure 4C shows the shift fork 50 when viewed from the same angle and viewpoint as Figure 4A.

[0053] 3A, 3B, and 4A to 4C, the shift fork 50 constituting the transmission mechanism 10 of the present disclosure is formed by joining a first member 50A and a second member 50B. The first member 50A is a member constituting one axial side of the shift fork 50, and the second member 50B is a member constituting the other axial side of the shift fork 50.

[0054] The shift fork 50 constituting the transmission mechanism 10 of the present disclosure includes a first arm 51, a second arm 52, and a sleeve 53. The sleeve 53 is composed of a first sleeve 53A constituting one axial side and a second sleeve 53B constituting the other axial side. The first sleeve 53A has a first coupling portion 57. The first coupling portion 57 is formed at the end of the first sleeve 53A on the other axial side. The second sleeve 53B has a second coupling portion 58. The second coupling portion 58 is formed at the end of the second sleeve 53B on one axial side.

[0055] The first member 50A includes a first sleeve 53A, a first arm 51 provided on the first sleeve 53A, and a first connecting portion 57. The second member 50B includes a second sleeve 53B, a second arm 52 provided on the second sleeve 53B, and a second connecting portion 58.

[0056] The first member 50A and the second member 50B are integrally formed by joining the first joining portion 57 and the second joining portion 58. As a result, the shift fork 50 is formed by the first member 50A and the second member 50B.

[0057] The first arm 51 includes a pair of claws 51a, 51b, an arm 51c, and a pair of ribs 51d. The pair of claws 51a, 51b engage with a groove 41a (see FIG. 2) formed on the outer circumferential surface of the first coupling sleeve 41. The first arm 51 engages with the groove 41a at two circumferential locations (the pair of claws 51a, 51b). The arm 51c has a double-arm shape that surrounds half of the outer circumferential surface of the first coupling sleeve 41 and supports the pair of claws 51a, 51b from the first sleeve 53A. The rib 51d connects the first sleeve 53A and the arm 51c and reinforces the strength of the arm 51c.

[0058] The second arm 52 includes a pair of claws 52a, 52b, an arm 52c, and a pair of ribs 52d. The pair of claws 52a, 52b engage with a groove 42a (see FIG. 2) formed on the outer circumferential surface of the second coupling sleeve 42. The second arm 52 engages with the groove 42a at two circumferential locations (the pair of claws 52a, 52b). The arm 52c has a double-arm shape that surrounds half of the outer circumferential surface of the second coupling sleeve 42 and supports the pair of claws 52a, 52b from the second sleeve 53B. The rib 52d connects the second sleeve 53B and the arm 52c and reinforces the strength of the arm 52c. The rib 52d also contributes to securing a space (accommodation portion 59c) for accommodating the detent mechanism 59 inside the second member 50B.

[0059] As shown in FIG. 2 , the shift fork 50 has a shift shaft 56 inserted through the shaft hole 54 with the first arm 51 engaged with the first coupling sleeve 41 (groove 41 a) and the second arm 52 engaged with the second coupling sleeve 42 (groove 42 a). The shift shaft 56 is parallel to the countershaft 32. The shift fork 50 (sleeve 53) is configured to be displaceable in the axial direction along the shift shaft 56. The first coupling sleeve 41 and the second coupling sleeve 42 are displaced synchronously with the displacement of the shift fork 50 in the direction along the shift shaft 56 (axial direction).

[0060] 5, the first coupling portion 57 has a first protrusion 57a ​​and a first recess 57b. The first protrusion 57a ​​is a portion that protrudes in the radial direction of the first sleeve 53A, and the first recess 57b is a portion that is recessed in the direction opposite to the protrusion of the first protrusion 57a. The first protrusion 57a ​​fits into a second recess 58b, which will be described after the second coupling portion 58. The first recess 57b fits into the second protrusion 58a, which will be described after the second coupling portion 58.

[0061] The second coupling portion 58 has a second protrusion 58a and a second recess 58b. The second protrusion 58a is a portion that protrudes in the radial direction of the second sleeve 53B and fits into the first recess 57b. The second recess 58b is a portion that is recessed in the opposite direction to the protrusion of the second protrusion 58a and fits into the first protrusion 57a.

[0062] The first connecting portion 57 and the second connecting portion 58 are connected to each other by fitting the first convex portion 57a ​​and the second concave portion 58b together and by fitting the second convex portion 58a and the first concave portion 57b together.

[0063] As described above, according to the shift fork 50 of this embodiment, the first member 50A and the second member 50B can be connected together without using a separate connecting member (in other words, without increasing the number of parts), which makes it possible to reduce the manufacturing cost of the shift fork 50 configured by connecting the first member 50A and the second member 50B.

[0064] The first coupling portion 57 further includes a first surface 57c, a second surface 57d, and a third surface 57e. The first surface 57c is a side surface on the other axial side of the first protrusion 57a. The second surface 57d is a side surface on one axial side of the first protrusion 57a ​​and a side surface on the other axial side of the first recess 57b. The third surface 57e is a side surface on one axial side of the first recess 57b.

[0065] The second coupling portion 58 further includes a fourth surface 58c, a fifth surface 58d, and a sixth surface 58e. The fourth surface 58c is a side surface on one axial side of the second protrusion 58a. The fifth surface 58d is a side surface on the other axial side of the second protrusion 58a and is a side surface on one axial side of the second recess 58b. The sixth surface 58e is a side surface on the other axial side of the second recess 58b.

[0066] In the shift fork 50, the first surface 57c and the sixth surface 58e, the second surface 57d and the fifth surface 58d, and the third surface 57e and the fourth surface 58c are opposed to each other. In the shift fork 50 configured as described above, when a force acts on the engaging portion 55 provided on the first member 50A in one axial direction, the second surface 57d presses the fifth surface 58d, thereby reliably transmitting the force in one axial direction to the second member 50B. In addition, in the shift fork 50 configured as described above, when a force acts on the engaging portion 55 provided on the first member 50A in the other axial direction, the first surface 57c presses the sixth surface 58e, and the third surface 57e presses the fourth surface 58c, thereby reliably transmitting the force in the other axial direction to the second member 50B. Therefore, although the shift fork 50 is configured to be divided into a first member 50A and a second member 50B in the axial direction, the first coupling sleeve 41 and the second coupling sleeve 42 can be reliably displaced to one side and the other side in the axial direction.

[0067] [Method of Manufacturing Shift Fork] Fig. 6 is an explanatory diagram of a method of manufacturing a first member. Fig. 7 is an explanatory diagram of a method of manufacturing a second member. As shown in Figs. 6 and 7, the first member 50A and the second member 50B constituting the shift fork 50 of the present disclosure are manufactured from a common base member 150.

[0068] As shown in Figures 6 and 7, the original part 150 includes an arm portion 151 that is the base of the first arm 51 and the second arm 52, a sleeve portion 153 that is the base of the first sleeve 53A and the second sleeve 53B, and a shaft hole portion 154 that is the base of the shaft hole 54. The original part 150 further includes a first processed part 160 and a second processed part 170. Note that the original parts 150 shown in Figures 6 and 7 are viewed from different angles, but are a common part and have the same shape. The original part 150 is manufactured by casting.

[0069] The manufacturing method of the shift fork 50 (see FIG. 4C) of the present disclosure includes a step of manufacturing the original member 150 (hereinafter also referred to as the first step), and a step of processing the original member 150 to manufacture the first member 50A and the second member 50B (hereinafter also referred to as the second step).

[0070] [First Step] The base member 150 is manufactured using a simple mold with a single punching direction. In the manufacturing method of the shift fork 50 of this embodiment, the first step includes a step of manufacturing the base member 150 by casting.

[0071] [Second Step] As shown in FIG. 6, the second step includes a step of manufacturing the first member 50A by performing a first processing on the first processed portion 160 and the second processed portion 170.

[0072] The first processing includes processing to form the first arm 51 from the arm portion 151, processing to form the first sleeve 53A from the sleeve portion 153, and processing to form the shaft hole 54 from the shaft hole portion 154. Specifically, the first processing forms the first arm 51, the first sleeve 53A, and the shaft hole 54 by machining (cutting, grinding, polishing, etc.).

[0073] The first processing includes processing for forming the first coupling portion 57 from the first processed portion 160. Specifically, the first processing includes processing for forming the first convex portion 57a, the first concave portion 57b, the first surface 57c, the second surface 57d, and the third surface 57e by machining (cutting, grinding, polishing, etc.).

[0074] The first processing also includes a step of forming the engaging portion 55 from the second workpiece 170. Specifically, the first processing includes processing of forming a groove 55a (engaging portion 55) in the second workpiece 170 by machining (cutting, grinding, polishing, etc.). This provides the engaging portion 55 in the first member 50A. The first processing may also include surface treatments such as heat treatment and nitriding treatment on the first joining portion 57 and the engaging portion 55.

[0075] In this manner, in the shift fork 50 of this embodiment, the engaging portion 55 is provided on either the first member 50A or the second member 50B (the first member 50A in this embodiment). According to the shift fork 50 configured in this manner, the engaging portion 55 can be easily provided on the shift fork 50 that is made up of the first member 50A and the second member 50B.

[0076] As shown in FIG. 7, the second step includes a step of manufacturing a second member 50B by performing a second processing on the first processed portion 160 and the second processed portion 170.

[0077] The second processing includes processing to form the second arm 52 from the arm portion 151, processing to form the second sleeve 53B from the sleeve portion 153, and processing to form the shaft hole 54 from the shaft hole portion 154. Specifically, the second processing forms the second arm 52, the second sleeve 53B, and the shaft hole 54 by machining (cutting, grinding, polishing, etc.).

[0078] The second processing includes processing for forming the second bonding portion 58 from the first processed portion 160. Specifically, the second processing includes processing for forming the second convex portion 58a, the second concave portion 58b, the fourth surface 58c, the fifth surface 58d, and the sixth surface 58e by machining (cutting, grinding, polishing, etc.). Note that the second processing may include surface treatment of the second bonding portion 58, such as heat treatment or nitriding.

[0079] The second processing also includes processing of the second workpiece 170. Specifically, the second processing includes processing to remove at least a portion of the second workpiece 170 by machining (cutting, grinding, polishing, etc.). The portion of the original member 150 that was the second workpiece 170 becomes in a form that cannot be used as the engaging portion 55 in the second member 50B after the second processing.

[0080] Furthermore, the second processing includes processing the accommodating portion 59c in the second member 50B. Specifically, the second processing includes processing a hole that will become the accommodating portion 59c by machining (cutting, grinding, polishing, etc.). According to the manufacturing method of the shift fork 50 of the present disclosure, by machining a hole in the second member 50B, the detent mechanism 59 can be easily provided in the shift fork 50. Note that, although the shift fork 50 of the present embodiment has the accommodating portion 59c provided in the second member 50B, the accommodating portion 59c may also be provided in the first member 50A.

[0081] The manufacturing method of the shift fork 50 of this embodiment makes it possible to easily provide the engaging portion 55 by providing the engaging portion 55 machined from the second processed portion 170 in the first member 50A and removing at least a portion of the second processed portion 170 in the second member 50B.

[0082] Conventionally, when manufacturing a shift fork having a pair of arms by casting, it is necessary to use a complex mold with two or more drawing directions, which increases the cost of manufacturing the mold and the time required for manufacturing. The complex configuration of the mold increases the manufacturing cost of such a shift fork.

[0083] 6 and 7 by casting, a simple mold with a single punching direction can be used. The shift fork 50 of this embodiment is manufactured by manufacturing the first member 50A and the second member 50B from the original member 150 manufactured using the simple mold, and then combining these members to manufacture the shift fork 50 having the first arm 51 and the second arm 52. According to this manufacturing method of the shift fork 50, the use of a mold with a simple configuration can reduce the manufacturing costs of the shift fork 50.

[0084] [Regarding Alternative Shift Fork Embodiments] The shift fork 50 described above has different shapes for the first and second connecting portions 57 and 58, resulting in different shapes for the first and second members 50A and 50B. However, the shift fork 50 of the present disclosure may be configured by connecting the first and second members 50A and 50B of the same shape. In this case, the first and second connecting portions 57 and 58 have the same shape, and the engaging portion 55 is configured by the first and second members 50A and 50B. In this case, the first and second processes are the same process, and only one type of member is required to be manufactured by dividing the shift fork 50 into two equal parts in the axial direction from one type of base member 150. In this shift fork 50, the processing of the base member 150 is unified into one process, enabling more efficient manufacturing of the first and second members 50A and 50B and reducing the number of parts. Therefore, when the shift fork 50 is configured using the first member 50A and the second member 50B of the same shape, the manufacturing cost of the shift fork 50 can be further reduced.

[0085] The above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and includes all modifications within the scope equivalent to the configurations described in the claims.

[0086] 10 Transmission mechanism 32 Counter shaft (first shaft) 41 First coupling sleeve 42 Second coupling sleeve 50 Shift fork 50A First member 50B Second member 51 First arm (arm) 52 Second arm (arm) 53 Sleeve 55 Engagement portion 56 Shift shaft (second shaft) 57 First connecting portion 57a ​​First convex portion 57b First concave portion 57c First surface 57d Second surface 57e Third surface 58 Second connecting portion 58a Second convex portion 58b Second concave portion 58c Fourth surface 58d Fifth surface 58e Sixth surface 59 Detent mechanism 59a Ball 59b Elastic member 59c Storage portion 80 Shift mechanism 150 Original member 160 First processed portion 170 Second processed portion

Claims

1. A transmission mechanism for a working machine comprising: a first axis and a second axis parallel to each other; a first coupling sleeve and a second coupling sleeve displaceable along the first axis; and a shift fork having a sleeve displaceable along the second axis, a first arm provided on the sleeve and engaging with the first coupling, and a second arm provided on the sleeve and engaging with the second coupling sleeve, wherein the shift fork is formed by connecting a first member constituting one axial side and a second member constituting the other axial side, the first member including a first sleeve constituting one axial side of the sleeve, and the first arm provided on the first sleeve, and the second member including a second sleeve constituting the other axial side of the sleeve, and the second arm provided on the second sleeve.

2. A transmission mechanism for a work machine as described in claim 1, wherein the first sleeve has a first connecting portion that connects the second member, the second sleeve has a second connecting portion that connects the first member, and the first connecting portion and the second connecting portion connect to each other.

3. A transmission mechanism for a work machine as described in claim 2, wherein the first connecting portion has a first convex portion that is convex in the radial direction of the first sleeve and a first concave portion that is concave in the opposite direction to the convex direction of the first convex portion, and the second connecting portion has a second convex portion that is convex in the radial direction of the second sleeve and fits into the first concave portion, and a second concave portion that is concave in the opposite direction to the convex direction of the second convex portion and fits into the first convex portion.

4. A transmission mechanism for a work machine as described in claim 1 or claim 2, further comprising a shift mechanism that displaces the shift fork in the axial direction of the second shaft, the shift fork having an engagement portion that engages with the shift mechanism, the engagement portion being provided on either the first member or the second member.

5. A transmission mechanism for a work machine as described in claim 1 or claim 2, further comprising a detent mechanism for holding the shift fork at a predetermined axial position of the second shaft, the detent mechanism including balls and an elastic member, and one of the first member and the second member including a housing portion for housing the balls and the elastic member.

6. A shift fork comprising: a sleeve through which a shaft is inserted; and a pair of arms provided on one axial side and the other axial side of the sleeve, wherein the shift fork is configured by joining a first member constituting one axial side and a second member constituting the other axial side, the first member including a first sleeve constituting one axial side of the sleeve and a first arm provided on the first sleeve, and the second member including a second sleeve constituting the other axial side of the sleeve and a second arm provided on the second sleeve.

7. The shift fork according to claim 6, wherein said first sleeve has a first connecting portion that connects said second member, said second sleeve has a second connecting portion that connects said first member, and said first connecting portion and said second connecting portion connect to each other.

8. A shift fork as claimed in claim 7, wherein the first connecting portion is provided at the other axial end of the first sleeve and has a first convex portion which convexes in the radial direction of the first sleeve and a first concave portion which is concave in a direction opposite to the convex direction of the first convex portion, and the second connecting portion is provided at one axial end of the second sleeve and has a second convex portion which convex in the radial direction of the second sleeve and fits with the first concave portion, and a second concave portion which is concave in a direction opposite to the convex direction of the second convex portion and fits with the first convex portion.

9. A shift fork as claimed in claim 8, wherein the first connecting portion has a first surface which is a side surface on the other axial direction side of the first convex portion, a second surface which is a side surface on one axial direction side of the first convex portion and which is a side surface on the other axial direction side of the first recess, and a third surface which is a side surface on one axial direction side of the first recess; the second connecting portion has a fourth surface which is a side surface on one axial direction side of the second convex portion, a fifth surface which is a side surface on the other axial direction side of the second convex portion and which is a side surface on one axial direction side of the second recess, and a sixth surface which is a side surface on the other axial direction side of the second recess, and the first surface and the sixth surface, the second surface and the fifth surface, and the third surface and the fourth surface oppose each other.

10. A shift fork according to claim 6 or 7, wherein said first member and said second member have the same shape.

11. A manufacturing method for a shift fork comprising: a sleeve through which a shaft is inserted; and a pair of arms provided on one axial side and the other axial side of the sleeve, the manufacturing method including: a first step of creating a common original part that is the basis for a first member that constitutes one axial side of the shift fork and a second member that constitutes the other axial side; and a second step of machining the original part to create the first member including a first sleeve that constitutes one axial side of the sleeve and a first arm provided on the first sleeve, and the second member including a second sleeve that constitutes the other axial side of the sleeve and a second arm provided on the second sleeve.

12. A method for manufacturing a shift fork as claimed in claim 11, wherein the first member has a first connecting portion that connects to the second member, the second member has a second connecting portion that connects to the first member, the original member has a first processed portion that is machined to the first connecting portion or the second connecting portion, and the second step includes a step of performing a first processing on the first processed portion to create the first member, and a step of performing a second processing on the first processed portion to create the second member.

13. A method for manufacturing a shift fork as set forth in claim 12, wherein the original member further has a second processed portion that is processed into an engagement portion that engages with a shift mechanism that displaces the sleeve in the axial direction, and either the first processing or the second processing includes processing to remove at least a portion of the second processed portion.

14. The method of manufacturing a shift fork according to claim 12, wherein the first processing and the second processing are the same processing, and the first member and the second member have the same shape.

15. A method of manufacturing a shift fork as set forth in claim 11 or 12, wherein the first step includes a step of producing the original member by casting.

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