Shift fork

Abstract

The objective of this invention is to maintain the operability of the shift lever. [Solution] The cylindrical portion has a cylindrical hole that penetrates the cylindrical portion in the front-rear direction. The first bush has a first bush hole that penetrates the first bush in the front-rear direction. The second bush has a second bush hole that penetrates the second bush in the front-rear direction and is located in front of the first bush within the cylindrical hole. The hardness of the second bush is higher than that of the first bush. The shift fork shaft passes through the first bush hole, the second bush hole and the cylindrical hole, allowing the cylindrical portion to move relative to the shift fork shaft in the forward and backward directions. The selector is fixed to the cylindrical portion and supports the sleeve. When the cylindrical portion and the selector move in the forward or backward direction, the selector moves the sleeve in the forward or backward direction and selects a gear that rotates with the sleeve.

Description

Technical Field

[0001] The present invention relates to a shift fork.

Background Art

[0002] As an invention related to a conventional shift fork, for example, a fork support structure described in Patent Document 1 is known. This fork support structure is used in a manual transmission of a type that axially slides a shift fork along the outer periphery of a fork shaft. A bush having a coating on its inner peripheral surface is press-fitted into the fork shaft fitting hole of the shift fork. Thereby, the frictional resistance between the fork shaft and the shift fork is reduced, and the shift operation feeling is maintained well.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in the field of shift forks, maintenance of shift operability is required.

[0005] Therefore, an object of the present invention is to provide a shift fork capable of maintaining shift operability.

Means for Solving the Problems

[0006] The first aspect is that the shift fork includes a cylindrical portion, a selector, a first bush, and a second bush, the cylindrical portion has a cylindrical hole penetrating the cylindrical portion in the front-rear direction, The first bush has a first bush hole that penetrates the first bush in the front-rear direction, and is positioned within the cylindrical hole so as to coincide with the center of the cylindrical hole in the front-rear direction. The second bush has a second bush hole that penetrates the second bush in the front-rear direction, and is located in front of or behind the first bush within the cylindrical hole. The hardness of the second bush is higher than that of the first bush. A manual transmission includes a shift fork shaft and a sleeve. The shift fork shaft passes through the first bushing hole, the second bushing hole, and the cylindrical hole, so that the cylindrical portion can move relative to the shift fork shaft in the forward and rearward directions. The selector is fixed to the cylindrical portion and supports the sleeve, When the cylindrical portion and the selector move forward or backward, the selector moves the sleeve forward or backward, and a gear that rotates together with the sleeve is selected. It's a shift fork.

[0007] The second aspect is, The diameter of the second bush hole is larger than the diameter of the first bush hole. This is the shift fork shown on the first side.

[0008] The third aspect is, The second bush is located in front of the first bush, The diameter of the second bush hole is equal to the diameter of the portion of the cylindrical hole after the first bush. This is a shift fork as described on the first or second side.

[0009] The fourth aspect is, The aforementioned shift fork further comprises a third bushing, The second bush is located in front of the first bush, The third bush has a third bush hole penetrating the third bush in the front-rear direction and is located behind the first bush within the cylindrical hole. The hardness of the second bush is higher than that of the first bush. The shift fork shaft penetrates the third bush hole. The shift fork described on the first side or the second side.

Advantages of the Invention

[0010] According to the present invention, the shift operation performance can be maintained.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a manual transmission 10. [Figure 2] FIG. 2 is a perspective view of a shift fork 18 and a shift fork shaft 20. [Figure 3] FIG. 3 is a top view of a shift fork 18 and a shift fork shaft 20. [Figure 4] FIG. 4 is a cross-sectional view of a shift fork 18. [Figure 5] FIG. 5 is a cross-sectional view of a shift fork 18 and a shift fork shaft 20. [Figure 6] FIG. 6 is a cross-sectional view of a shift fork 118 and a shift fork shaft 120 according to a comparative example. [Figure 7] FIG. 7 is a cross-sectional view of a shift fork 118 and a shift fork shaft 120. ;40]] [Figure 8] FIG. 8 is a cross-sectional view of a shift fork 38.

Modes for Carrying Out the Invention

[0012] (Embodiment)<; [Structure of Manual Transmission 10] The structure of the manual transmission 10 according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the manual transmission 10. FIG. 1 is a cross-sectional view orthogonal to the vertical direction. FIG. 2 is a perspective view of the shift fork 18 and the shift fork shaft 20. FIG. 3 is a top view of the shift fork 18 and the shift fork shaft 20. FIG. 4 is a cross-sectional view of the shift fork 18. FIG. 5 is a cross-sectional view of the shift fork 18 and the shift fork shaft 20. FIGS. 4 and 5 are cross-sectional views orthogonal to the left-right direction. Hereinafter, the direction in which the shift fork shaft 20 extends is defined as the front-rear direction. Also, the directions orthogonal to the front-rear direction are defined as the left-right direction and the vertical direction. Note that the front-rear direction, the left-right direction, and the vertical direction are merely defined for convenience of explanation, and the front-rear direction, the left-right direction, and the vertical direction during actual use of the manual transmission 10 do not have to coincide with the front-rear direction, the left-right direction, and the vertical direction in this specification.

[0013] In this specification, that X is located in front of Y means the following. X and Y are arranged in this order from the front to the rear, and at least a part of X overlaps at least a part of Y when viewed in the rear direction. In this specification, that X is located in front of Y means the following. A virtual plane including the front end of Y and orthogonal to the front-rear direction is defined. The whole of X is located in front of the virtual plane. When viewed in the rear direction, at least a part of X may overlap at least a part of Y, or at least a part of X may not overlap at least a part of Y when viewed in the rear direction. Note that the positional relationship in the front-rear direction has been described, but the positional relationships in the left-right and vertical directions are the same as those in the vertical direction, so the description is omitted.

[0014] In this specification, the front end of X means the point located most in front in X. The front end portion of X means the front end of X and the periphery of the front end of X. Note that the definitions of the rear end, the left end, the right end, the upper end, and the lower end are the same as those of the front end, so the description is omitted. The definitions of the rear end portion, the left end portion, the right end portion, the upper end portion, and the lower end portion are the same as those of the front end portion, so the description is omitted.

[0015] The manual transmission 10 is applied to four-wheeled vehicles. The manual transmission 10 is a transmission for transmitting power generated by the engine to the wheels. In the manual transmission 10, the driver can manually change gears by operating the clutch pedal and shift lever. As shown in Figures 1 and 2, the manual transmission 10 comprises a transmission case 12, a shaft 14, a sleeve 16, a shift fork 18, a shift fork shaft 20, a selector shaft 22, and gears G3, G4.

[0016] The transmission case 12 is a housing that contains the shaft 14, sleeve 16, shift fork 18, shift fork shaft 20, selector shaft 22, and gears G3 and G4.

[0017] The shaft 14 is located inside the transmission case 12. The shaft 14 extends in the front-rear direction. The shaft 14 is supported by the transmission case 12 so that it can rotate about a central axis that extends in the front-rear direction.

[0018] Gear G3 is the gear used when the driver selects third gear. Gear G3 is supported on shaft 14 so that it can rotate around a central axis that extends in the front-to-back direction. Gear G3 can also rotate around shaft 14 around the central axis that extends in the front-to-back direction.

[0019] Gear G4 is the gear used when the driver selects fourth gear. Gear G4 is located after gear G3. Gear G4 is supported by shaft 14 so that it can rotate around a central axis that extends in the front-rear direction. Gear G4 can also rotate around shaft 14 around the central axis that extends in the front-rear direction.

[0020] The sleeve 16 has an annular shape with a central axis extending in the front-rear direction. The sleeve 16 is positioned between gear G3 and gear G4. The sleeve 16 is supported by the shaft 14 so that it can rotate about the central axis extending in the front-rear direction. The sleeve 16 can rotate together with the shaft 14. The sleeve 16 can also move in the forward and backward directions. The sleeve 16 includes a synchronous mesh mechanism. However, since the synchronous mesh mechanism has a common structure, its explanation will be omitted.

[0021] As shown in Figures 2 to 4, the shift fork 18 comprises a cylindrical portion 18a, a selector 18b, a selector pocket 18c, a first bush 24, and a second bush 26.

[0022] The cylindrical portion 18a has a cylindrical shape with a central axis extending in the front-rear direction. Therefore, the cylindrical portion 18a has a cylindrical hole H1 that penetrates the cylindrical portion 18a in the front-rear direction. The cylindrical portion 18a includes a first part 18a-1 and a second part 18a-2. The first part 18a-1 is located in front of the second part 18a-2. The diameter D1 of the cylindrical hole H1 in the first part 18a-1 is greater than the diameter D2 of the cylindrical hole H1 in the second part 18a-2.

[0023] The selector 18b is fixed to the cylindrical portion 18a. In this embodiment, the selector 18b is located below the cylindrical portion 18a. The selector 18b has an arc shape with a central axis extending in the front-rear direction. The selector 18b supports the sleeve 16. Specifically, the selector 18b is in contact with the outer circumferential surface of the annular sleeve 16. The sleeve 16 can rotate relative to the selector 18b about its central axis extending in the front-rear direction.

[0024] The selector pocket 18c is fixed to the cylindrical portion 18a. In this embodiment, the selector pocket 18c extends forward from the outer circumferential surface of the cylindrical portion 18a. The shift fork 18 described above is made of a metal such as iron or aluminum. The shift fork 18 is manufactured by casting or forging.

[0025] The first bush 24 has a cylindrical shape with a central axis extending in the front-rear direction. The first bush 24 has a first bush hole h1 that penetrates the first bush 24 in the front-rear direction. The diameter of the outer surface of the first bush 24 is equal to the diameter D1 of the cylindrical hole H1. The first bush 24 is press-fitted into the cylindrical hole H1. As a result, the first bush 24 is located inside the cylindrical hole H1. More precisely, the first bush 24 is located inside the cylindrical hole H1 so as to coincide with the center C0 of the cylindrical hole H1 in the front-rear direction. The rear end of the first bush 24 is in contact with the front end of the second part 18a-2. The hardness of the first bush 24 is lower than the hardness of the shift fork 18. The first bush 24 is made of resin.

[0026] The second bush 26 has a cylindrical shape with a central axis extending in the front-rear direction. The second bush 26 has a second bush hole h2 that penetrates the second bush 26 in the front-rear direction. The diameter d2 of the second bush hole h2 is greater than the diameter d1 of the first bush hole h1. Furthermore, the diameter d2 of the second bush hole h2 is equal to the diameter D2 of the portion of the cylindrical hole H1 behind the first bush 24. That is, the diameter d2 of the second bush hole h2 is equal to the diameter D2 of the cylindrical hole H1 in the second part 18a-2.

[0027] Furthermore, the diameter of the outer surface of the second bush 26 is equal to the diameter D1 of the cylindrical hole H1. The second bush 26 is press-fitted into the cylindrical hole H1. As a result, the second bush 26 is positioned in front of the first bush 24 within the cylindrical hole H1. The front end of the second bush 26 coincides with the front end of the cylindrical hole H1. The rear end of the second bush 26 does not contact the first bush 24. Therefore, there is a small gap between the rear end of the second bush 26 and the front end of the first bush 24. The second bush 26 is made of resin. The hardness of the second bush 26 is higher than that of the first bush 24. However, the hardness of the second bush 26 is lower than that of the shift fork 18. Hardness is measured, for example, on a Shore hardness scale.

[0028] The selector shaft 22 is a component that transmits the driver's shift operation to the shift fork 18. The selector shaft 22 is connected to the selector pocket 18c. The selector shaft 22 moves forward or backward in response to the driver's shift operation. As a result, the shift fork 18 is moved forward or backward by the selector shaft 22.

[0029] The shift fork shaft 20 has a cylindrical shape that extends in the front-rear direction. The diameter D11 of the shift fork shaft 20 is substantially equal to the diameter d1 of the first bush hole h1. The shift fork shaft 20 passes through the first bush hole h1, the second bush hole h2, and the cylindrical hole H1. At this time, the shift fork shaft 20 contacts the inner circumferential surface of the first bush hole h1, but does not contact the inner circumferential surface of the second bush hole h2 or the inner circumferential surface of the second part 18a-2. This allows the cylindrical part 18a to move relative to the shift fork shaft 20 in the front and rear directions.

[0030] In the manual transmission 10 described above, when the driver shifts gears and moves the selector shaft 22 forward, the selector pocket 18c moves forward. This causes the sleeve 16 to move forward, and the sleeve 16 to engage with gear G3. As a result, the shaft 14, sleeve 16, and gear G3 rotate together as a unit. That is, gear G3 is selected by the driver. On the other hand, when the driver shifts gears and moves the selector shaft 22 backward, the selector pocket 18c moves backward. This causes the sleeve 16 to move backward, and the sleeve 16 to engage with gear G4. As a result, the shaft 14, sleeve 16, and gear G4 rotate together as a unit. Gear G4 is selected by the driver. As described above, when the cylindrical part 18a and selector 18b move forward or backward, the selector 18b moves the sleeve 16 forward or backward, and gear G3 or gear G4, which rotates together with the sleeve 16, is selected.

[0031] [effect] The shift fork 18 maintains the operability of the shift. This will be explained below with reference to the drawings. Figure 6 is a cross-sectional view of the shift fork 118 and shift fork shaft 120 according to the comparative example. Figure 7 is a cross-sectional view of the shift fork 18 and shift fork shaft 20. In the shift fork 118 according to the comparative example, the same components as the shift fork 18 are given reference numerals that are 100 added to the reference numerals of the components of the shift fork 18.

[0032] In the comparative example shift fork 118, the diameter of the cylindrical hole H1 in the cylindrical portion 118a is diameter D1. The first bush 124 and the third bush 128 are located within the cylindrical hole H1. The front end of the first bush 124 coincides with the front end of the cylindrical hole H1. The rear end of the third bush 128 coincides with the rear end of the cylindrical hole H1. The material of the first bush 124 is the same as the material of the third bush 128. Therefore, the hardness of the first bush 124 is the same as the hardness of the third bush 128.

[0033] In such a shift fork 118, as shown in Figure 6, the shift fork shaft 120 may tilt due to the driver's shift operation. As a result, the shift fork shaft 120 is pressed with a large force against the vicinity A of the front end of the first bush 124 and the vicinity B of the rear end of the third bush 128. If this condition is repeated, the vicinity A of the front end of the first bush 124 and the vicinity B of the rear end of the third bush 128 will wear down. As a result, the operability of the shift will decrease.

[0034] On the other hand, in the shift fork 18, the first bush 24 is positioned so as to coincide with the center C0 in the front-rear direction of the cylindrical bore H1. The second bush 26 is positioned in front of the first bush 24 within the cylindrical bore H1. As shown in Figure 7, when the shift fork shaft 20 tilts due to the driver's shift operation, the shift fork shaft 20 is pressed with a large force against the vicinity C of the front end of the second bush 26. However, since the hardness of the second bush 26 is higher than that of the first bush 24, the vicinity C of the front end of the second bush 26 is less prone to wear. As a result, the shift operability of the shift fork 18 is less likely to deteriorate.

[0035] Furthermore, in the shift fork 18, the diameter d2 of the second bush hole h2 is larger than the diameter d1 of the first bush hole h1. As a result, when the shift fork shaft 20 is not tilted, the second bush 26 does not come into contact with the shift fork shaft 20. Therefore, the second bush 26 does not obstruct the shift fork shaft 20 from moving forward or backward.

[0036] (modified version) The following describes a modified shift fork 38 with reference to the drawings. Figure 8 is a cross-sectional view of the shift fork 38.

[0037] The shift fork 38 differs from the shift fork 18 in that it further comprises a third bush 28. More specifically, the third bush 28 has a third bush hole h3 that penetrates the third bush 28 in the longitudinal direction. The third bush 28 is located behind the first bush 24 in the cylindrical hole H1. The diameter d3 of the third bush hole h3 is greater than the diameter d1 of the first bush hole h1. The diameter d3 of the third bush hole h3 is equal to the diameter d2 of the second bush hole h2.

[0038] Furthermore, the third bush 28 is made of resin. The hardness of the third bush 28 is higher than that of the first bush 24. In this embodiment, the hardness of the third bush 28 is equal to that of the second bush 26. However, the hardness of the third bush 28 is lower than that of the shift fork 18. In such a shift fork 38, the shift fork shaft 20 passes through the third bush hole h3.

[0039] The shift fork 38 described above can achieve the same effect as the shift fork 18.

[0040] (Other embodiments) The shift fork according to the present invention is not limited to the shift fork 18, but can be modified within the scope of its gist.

[0041] The second bush 26 may be located behind the first bush 24 within the cylindrical bore H1.

[0042] The shift forks 18 and 38 are used to select either the 3rd gear G3 or the 4th gear G4, but they may also be used to select a gear other than the 3rd gear G3 or the 4th gear G4.

[0043] In addition, it is not a mandatory requirement that the diameter d2 of the second bush hole h2 be larger than the diameter d1 of the first bush hole h1 in the shift fork 18.

[0044] In addition, it is not a mandatory requirement that the diameter d2 of the second bush hole h2 and the diameter d3 of the third bush hole h3 be larger than the diameter d1 of the first bush hole h1 in the shift fork 38. [Explanation of Symbols]

[0045] 10: Manual transmission 12: Mission Case 14: Shaft 16: Sleeves 18,38: Shift fork 18a:Cylinder part 18a-1: Part 1 18a-2: Part 2 18b: Selector 18c: Selector pocket 20: Shift fork shaft 22: Selector shaft 24: First Bush 26: Second Bush 28: Third Bush 118: Shift fork 118a: Cylinder part 120: Shift fork shaft 124: First Bush 128: Third Bush C0:Center G3, G4: Gear H1,: Cylindrical hole h1: First bush hole h2: Second bush hole h3: Third bush hole

Claims

1. The shift fork comprises a cylindrical section, a selector, a first bushing, and a second bushing. The cylindrical portion has a cylindrical hole that penetrates the cylindrical portion in the front-to-back direction, The first bush has a first bush hole that penetrates the first bush in the front-rear direction, and is positioned within the cylindrical hole so as to coincide with the center of the cylindrical hole in the front-rear direction. The second bush has a second bush hole that penetrates the second bush in the front-rear direction, and is located in front of or behind the first bush within the cylindrical hole. The hardness of the second bush is higher than that of the first bush. A manual transmission includes a shift fork shaft and a sleeve. The shift fork shaft passes through the first bushing hole, the second bushing hole, and the cylindrical hole, so that the cylindrical portion can move relative to the shift fork shaft in the forward and rearward directions. The selector is fixed to the cylindrical portion and supports the sleeve, When the cylindrical portion and the selector move forward or backward, the selector moves the sleeve forward or backward, and a gear that rotates together with the sleeve is selected. Shift fork.

2. The diameter of the second bush hole is larger than the diameter of the first bush hole. The shift fork according to claim 1.

3. The second bush is located in front of the first bush, The diameter of the second bush hole is equal to the diameter of the portion of the cylindrical hole after the first bush. A shift fork according to claim 1 or claim 2.

4. The aforementioned shift fork further comprises a third bushing, The second bush is located in front of the first bush, The third bush has a third bush hole that penetrates the third bush in the front-rear direction, and is located behind the first bush within the cylindrical hole. The hardness of the third bush is higher than that of the first bush. The shift fork shaft penetrates the third bushing hole, A shift fork according to claim 1 or claim 2.

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