JP4897652B2 - Gear transmission shift mechanism - Google Patents

Description

  The present invention relates to a shift mechanism of a gear transmission, and more particularly to a shift mechanism of a gear transmission having a shift operation force assist function.

  An example of such a gear transmission shift mechanism is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2005-155792). This is because the four fork shafts for switching the transmission gear are guided and supported by the transmission case so as to be movable in the axial direction parallel to each other, and the tip of the lever member provided on the shift and select shaft is provided at one end of each fork shaft. One of the shift heads is selectively engaged, and the selected fork shaft is moved in the axial direction to switch the transmission gear through the shift fork.

  In the technique of Patent Document 1 described above, the shift head is provided at one end of each fork shaft. However, there is a conventional technique in which a shift head is provided at the center of each fork shaft, and FIGS. 1 shows an example of a shift mechanism of a simple gear transmission. In this gear transmission shift mechanism, each of the four fork shafts 2a to 2d arranged in parallel with each other has a pair of support holes formed so that both end portions thereof are coaxially opposed to the transmission case 1. 1a and 1a are slidably guided and supported, and each fork shaft 2a to 2d is axially driven by a detent mechanism 6 comprising three engaging recesses 6a formed on the outer periphery thereof and a lock ball 6b urged by a spring. Are elastically held at the neutral position and at the shift positions on both sides thereof. The shift heads 3a to 3d are held by the retaining ring 9 at the center of the fork shafts 2a to 2d. When the fork shafts 2a to 2d are held at the central neutral position, the shift heads 3a to 3d are axially moved. The groove portions 4a to 4d formed in each of the shift heads 3a to 3d are arranged in a direction orthogonal to each other and are continuous in a direction orthogonal to the axial direction. The fork shafts 2a to 2d are provided with shift forks 5a to 5d for switching the transmission gears, respectively.

A part of the shift and select shaft 7 provided so as to be axially movable and rotatable along the upper side of each shift head 3a to 3d provided on each fork shaft 2a to 2d has a radius toward the shift head 3a to 3d side. One lever member 8 projecting in the direction is fixed, and a tip end portion 8a of the lever member 8 is slidably engaged in each of the groove portions 4a to 4d. The lever member 8 moves in parallel by the axial movement of the shift and select shaft 7 and moves in the groove portions 4a to 4d of the shift heads 3a to 3d whose tip portion 8a is in the neutral position. After selecting the heads 3a to 3d, the shift gear is switched by moving one fork shaft provided with the shift head in the axial direction via the shift head selected by the rotation of the shift and select shaft 7.
Japanese Patent Laying-Open No. 2005-155792 (paragraphs [0013] to [0015], paragraphs [0020] to [0021], FIGS. 1 and 2).

  The above-described techniques shown in FIGS. 8 and 9 have a simple structure and no functional problem in practical use, but it is difficult to adjust the operation force required for the shift. There is a problem that the feeling cannot be obtained. The object of the present invention is to solve such a problem based on the technique shown in FIGS.

  For this purpose, the shift mechanism of the gear transmission according to the present invention is provided with a shift fork for switching the transmission gears and arranged in parallel with each other, and a neutral position in which power transmission is not performed by the transmission gear. A plurality of fork shafts guided and supported by the transmission case so as to be movable in the axial direction between them, and in a state where each of the fork shafts is in a neutral position, the fork shafts are aligned in a direction perpendicular to the axial direction. A plurality of shift heads that are respectively provided on the fork shafts and formed with continuous groove portions in the orthogonal direction, and guided and supported by the transmission case so as to be axially movable and rotatable along one side of the fork shafts. Shift and select shaft, fixed to this shift and select shaft and protruded radially The lever member is provided with a lever member that is slidably engaged in each groove portion, and the lever member has its distal end moved by any one of the parallel movement and swinging accompanying the axial movement and rotation of the shift and select shaft. The shift head selected by the other of the parallel movement and the swing and the shift head is selected after moving in each groove of each shift head provided on each fork shaft in which the section is in the neutral position In the shift mechanism of the gear transmission that moves the fork shaft provided with a shaft in the axial direction and switches the transmission gear through the shift fork, each fork shaft is formed so that both ends thereof are coaxially opposed to the transmission case. A pair of cylinder holes are slidably fitted and supported in a fluid-tight manner, and first and second pressure chambers are formed between both ends and each pair of cylinder holes. The hydraulic fluid is supplied from the oil pump via the first and second supply passages, respectively, and the shift head has two inner peripheral surfaces spaced apart from each other by an axial distance from the outer peripheral surface of the axially intermediate portion of the fork shaft. A control passage is formed that is slidably liquid-tightly fitted between the snap positions and is opened to the inner peripheral surface. Between the fork shaft and the shift head, the shift head is located at two snap positions with respect to the fork shaft. A first detent mechanism is provided for elastically holding at the center position of the lever. The lever member elastically holds the fork shaft provided on the selected shift head in the neutral position in cooperation with the first detent mechanism. A second detent mechanism is provided, and the fork shaft is formed with a pair of first and second oil passages extending inward in the axial direction from both end faces thereof, and The inner ends are each opened to the outer peripheral surface of the fork shaft, and in a state where the shift head is held at the center position, both oil passages communicate with the control passage through the opening to the outer peripheral surface, and either of the shift heads When one of the oil passages located on the opposite side of the snap position is closed by the inner peripheral surface of the shift head, the opening to the outer peripheral surface is closed by the shift head, and the other oil passage is It is configured to communicate with the control passage through the opening to the surface and communicate with the reservoir side of the oil pump from the control recess.

  In the shift mechanism of the gear transmission according to claim 1, it is preferable that the oil pump has a pressure regulating function.

  The shift mechanism of the gear transmission according to claim 1 or 2, wherein the control passage is a control recess that is opened at an axially intermediate portion of the inner peripheral surface of the shift head, and the control recess is provided in the shift head. It is preferable to provide a discharge port that always communicates with the reservoir.

  The shift mechanism of the gear transmission according to claim 1 or 2, wherein the control passage is a control recess that is opened at an axially intermediate portion of the inner peripheral surface of the shift head, and the fork shaft is opened at the outer peripheral surface thereof. When the shift head is in the center position, a discharge passage may be provided that does not communicate the control recess with the reservoir side of the oil pump, but communicates the control recess with the reservoir side when in the snap position.

  3. The shift mechanism for a gear transmission according to claim 1, wherein the control passages are formed by penetrating through the wall surface of the shift head in the radial direction from the inner peripheral surface toward the outer surface. The first oil passage is communicated with the reservoir side of the oil pump via the first control passage and the second oil passage side when the shift head is in the center position or the snap position on the first oil passage side. The second oil passage is configured to be blocked from the reservoir side by the inner peripheral surface of the shift head in the state where the shift head is located, and the second oil passage is second in the state where the shift head is in the center position or the snap position where the second oil passage is located. In the state where it is in communication with the reservoir side of the oil pump through the control passage and is in the snap position on the first oil passage side, it is blocked from the reservoir side by the inner peripheral surface. It may be.

  According to the first aspect of the present invention, each fork shaft is fitted and supported in a liquid-tight slidable manner in each pair of cylinder holes formed at both ends of the fork shafts so as to be coaxially opposed to the transmission case. The first and second pressure chambers are formed between the both ends and each pair of cylinder holes, and hydraulic oil is supplied to each pressure chamber from the oil pump via the first and second supply passages, respectively. The inner peripheral surface of the shift head is fitted and supported in a liquid-tight manner so as to be slidable between two snap positions with a certain distance in the axial direction on the outer peripheral surface of the axially intermediate portion of the fork shaft. A control path that opens to the fork shaft, and a first detent mechanism that elastically holds the shift head at the center of the two snap positions with respect to the fork shaft. It is the selected A second detent mechanism is provided for elastically holding the fork shaft provided on the head in a neutral position in cooperation with the first detent mechanism. The fork shaft has a pair of first extensions extending inward in the axial direction from both end faces thereof. The first and second oil passages are formed, and the inner ends of the respective oil passages are opened to the outer peripheral surface of the fork shaft. When the shift head is held at the center position, both the oil passages pass through the openings to the outer peripheral surface. Each of the oil passages located on the opposite side of the snap position is closed by the inner peripheral surface of the shift head when the shift head is in one of the snap positions. The other oil passage is communicated with the control passage through an opening to the outer peripheral surface and communicated from the control recess to the reservoir side of the oil pump. Therefore, when the shift head is moved axially with respect to the fork shaft by the lever member to one snap position, one pressure chamber located on the opposite side of the one snap position is operated from the oil pump. Hydraulic pressure is applied, and the other pressure chamber is communicated to the reservoir side, and no operating hydraulic pressure is applied. Therefore, the axial force generated in the fork shaft is the sum of the force that the tip of the lever member pushes the fork shaft through the shift head and the force that presses the fork shaft by the hydraulic pressure applied to one of the pressure chambers. The operating force applied to the lever member is less than the force required to shift the transmission gear by the amount of the hydraulic pressure applied to the pressure chamber. Accordingly, it is possible to improve the shift feeling by reducing the operating force applied to the lever member. Further, what should be added in comparison with the prior art shown in FIG. 8 and FIG. 9 is an oil pump, a first detent mechanism, and members and processing for constituting an oil passage, and a transmission case and a fork which are main members. Since the shaft and the shift head can be used almost as they are, the increase in manufacturing cost required for the implementation is also small.

  Although there are various needs for the shift feeling of the shift mechanism of the gear transmission, the oil pump has a pressure regulating function. According to the invention of claim 2, the output hydraulic pressure of the oil pump is adjusted as necessary. By adjusting, it is possible to widely meet such requirements.

  4. The control passage according to claim 3, wherein the control passage is a control recess that is opened at an axially intermediate portion of the inner peripheral surface of the shift head, and the shift head is provided with a discharge port that always communicates with the control recess on the reservoir side of the oil pump. Thus, a gear transmission shift mechanism having an extremely simple structure and easy implementation can be obtained.

  The control passage is a control recess that is opened in the middle in the axial direction of the inner peripheral surface of the shift head. When the shift head is in the center position on the fork shaft, the control recess is located on the reservoir side of the oil pump. According to the invention of claim 4, there is provided a discharge passage for communicating the control recess to the reservoir side when in the snap position, but when the shift head is in the center position with respect to the fork shaft, the operation from the oil pump is performed. Since oil is not discharged to the reservoir side, energy consumption by the oil pump can be reduced.

  Each of the control passages is composed of first and second control passages that are formed through the wall surface of the shift head in a radial direction from the inner peripheral surface to the outer surface. In the state of being in the snap position on the first oil passage side, it communicates with the reservoir side of the oil pump via the first control passage, and in the state of being in the snap position on the second oil passage side, from the reservoir side by the inner peripheral surface of the shift head. The second oil passage is communicated to the reservoir side of the oil pump via the second control passage when the shift head is at the center position or the snap position at the second oil passage side. According to the invention of claim 5, which is configured to be blocked from the reservoir side by the inner peripheral surface in the snap position on the road side. It is possible to process the passage from the outside of the shift head can reduce the manufacturing cost.

  The best mode for carrying out the shift mechanism of the gear transmission according to the present invention will be described below with reference to FIGS. 1 to 5 show only the longitudinal sectional view corresponding to FIG. 9 of the prior art described above, the embodiment shown in FIGS. 1 to 5 is also the same as the prior art shown in FIGS. A plurality of (for example, four) fork shafts 12 that are arranged parallel to each other along a horizontal plane and switch the transmission gears, and each of the fork shafts 12 to 12 is held in a neutral position in the axial direction. In the state, the shift heads 15 to 15 are aligned in the direction orthogonal to the axial direction, and the groove portions 15a to 15a formed in the shift heads 15 to 15 are continuous in the direction orthogonal to the axial direction.

  First, the structure of this embodiment will be described mainly with reference to FIG. A plurality of pairs (for example, four pairs) of bottomed cylinder holes 11 are formed in the transmission case 10 so as to be coaxially opposed to each other, and both end portions of the respective fork shafts 12 are fitted into the opposed cylinder holes 11, Both end faces are supported so as to be slidable in the axial direction between two shift positions where the both end faces come into contact with the bottom face of each cylinder hole 11. The fitting portion between the inlet portion of each cylinder hole 11 and both end portions of the fork shaft 12 is liquid-tightly sealed by an oil seal 14 provided in the transmission case 10, and between each end surface of the fork shaft 12 and each cylinder hole 11. Are formed with first and second pressure chambers 30a, 30b, and an oil pump 35 is connected to the first and second pressure chambers 30a, 30b via first and second supply passages 32a, 32b. Yes. The oil pump 35 has a pressure adjusting function capable of adjusting the operating oil pressure manually or automatically according to the operating state, and the supply passages 32a and 32b are respectively throttled for the pressure chambers 30a and 30b. Portions 32a1 and 32b1 are provided. The hydraulic oil in the reservoir 35a formed by the bottom of the transmission case 10 is sucked by the oil pump 35 and supplied to the pressure chambers 30a and 30b via the supply passages 32a and 32b. Each fork shaft 12 is provided with a boss portion 13a of a shift fork 13 having a fork portion 13b for switching a transmission gear.

  On the outer peripheral surface of the central portion of each fork shaft 12, a substantially rectangular cubic shift head 15 is fitted and supported so as to be liquid-slidable only in the axial direction, and the outer peripheral surface of the fork shaft 12 serving as both sides of the shift head 15. A pair of retaining rings 19a and 19b are fitted so that the shift head 15 can move between two snap positions at a certain distance in the axial direction. Further, between the fork shaft 12 and the shift head 15 on the lower side in FIG. 1, the shift head 15 is positioned with respect to the fork shaft 12 just at the center of the two snap positions abutting against the retaining rings 19 a and 19 b. A first detent mechanism 16 is provided for elastically holding at a central position. This first detent mechanism 16 has a shallow V-shaped engaging recess 17 formed on the outer peripheral surface of the central portion in the axial direction of the fork shaft 12 and the same as the engaging concave portion 17 in the central portion in the axial direction of the shift head 15. Between a guide hole 18a formed in a radial direction at a circumferential position, a lock ball 18 movably held in the guide hole 18a, and a stopper plug 18c for closing the outer end of the guide hole 18a. The spring 18 b is interposed and elastically presses the lock ball 18 toward the engagement recess 17.

  In the center of one side, which is the upper side of the shift head 15 in FIG. 1, a groove portion 15 a having a constant width extending in a direction orthogonal to the axial direction by a pair of protrusions protruding in the axial direction extends over the entire width of the shift head 15. Is formed. In addition, a control recess (control passage) 33 is formed in the axially intermediate portion on the inner peripheral surface of the shift head 15 fitted to the outer peripheral surface of the fork shaft 12, and this control recess 33 is formed in the shift head 15 by a discharge port 33a. It communicates with the outside.

  In a state where each fork shaft 12 holding each shift head 15 at the center position is held at the neutral position which is exactly the center of the two shift positions described above, each shift head 15 is aligned in a direction orthogonal to the axial direction. The groove portion 15a is continuous in a straight line, but in this state, at a position directly above the groove portion 15a of each shift head 15, one shift and select shaft 20 is capable of moving and rotating in the axial direction. The case 10 is guided and supported. A single lever member 21 protruding in the radial direction toward the shift head 15 is fixed to a part of the shift and select shaft 20. The end portion 21a of the lever member 21 is formed of a part of a continuous cylindrical surface, and both side surfaces thereof are engaged with the groove portions 15a so as to be slidable in a direction perpendicular to the axial direction of the fork shafts 12. The stroke length of the shift and select shaft 20 in the axial direction and the thickness of the lever member 21 are selectively engaged in the groove portions 15a of all the shift heads 15 in which the distal end portion 21a of the lever member 21 that moves is in the neutral position. The value is such that

  Between the shift and select shaft 20 and the transmission case 10 on the upper side thereof, the lever member 21 is located at the center position shown in FIG. 1 and the maximum swing position on both sides thereof (corresponding to each shift position of the fork shaft 12, FIG. 3 shows a state in one of them), and a pair of second detent mechanisms 22 that are elastically held is provided. This second detent mechanism 22 is formed over about half of the outer circumference of the shift and select shaft 20 in the circumferential direction, and includes one cam member 23 in which three shallow V-shaped engaging recesses 23a are formed, and a transmission case. A bottomed cylindrical guide hole 24a formed radially inwardly from the shift and select shaft 20; a lock ball 24 movably held in the guide hole 24a; and a bottom surface of the guide hole 24a; And a spring 24b that elastically presses the lock ball 24 toward the cam member 23. The cam member 23 has such a length that the engaging recess 23 a can be engaged with the lock ball 24 at any position in the axial stroke of the shift and select shaft 20.

  As shown in FIG. 1, in the state where the lever member 21 is held at the center position by the second detent mechanism 22, the shift head 15 is held at the center position with respect to the fork shaft 12 by the first detent mechanism 16. 12 is held in a neutral position. In other words, the fork shaft 12 is held in the neutral position in cooperation with the first and second detent mechanisms 16 and 22.

  As shown in FIG. 1, the fork shaft 12 has a pair of first and second oil passages extending inward in the axial direction from both end surfaces forming part of the wall surfaces of the first and second pressure chambers 30a and 30b. 31a and 31b are formed independently of each other. The inner ends of the oil passages 31a and 31b are opened to the outer peripheral surface of the fork shaft 12 through the first and second communication passages 31a1 and 31b1, respectively, and their positions are set so as to satisfy the following conditions. Yes. That is, each opening is located near both ends in the control recess 33 of the shift head 15 when the shift head 15 is in the center position with respect to the fork shaft 12 as shown in FIG. The paths 31a and 31b are communicated with each other via the control recess 33, and are communicated with the transmission case 10 on the reservoir 35a side of the oil pump 35 via the discharge port 33a. As shown in FIGS. 2 and 3, when the shift head 15 is in the snap position on the first oil passage 31 a side, the opening of the first communication passage 31 a 1 to the outer peripheral surface of the fork shaft 12 is inside the control recess 33. The first oil passage 31a is communicated with the transmission case 10 via the control recess 33 and the discharge port 33a, and the opening of the second communication passage 31b1 to the outer peripheral surface of the fork shaft 12 is formed in the shift head 15. The second oil passage 31 b is cut off from the control recess 33 by being closed by the inner peripheral surface of the control oil. Further, as shown in FIG. 5, when the shift head 15 is in the snap position on the second oil passage 31b side, the second oil passage 31b is similarly connected to the transmission case 10 via the control recess 33 and the discharge port 33a. The first oil passage 31 a is cut off from the control recess 33.

  Next, the operation of the above-described embodiment will be described. When the gear transmission is in the neutral position and no power is transmitted by the transmission gear, as shown in FIG. 1, the lever member 21 operated by the manual shift lever via the shift and select shaft 20 is in the center position. Each fork shaft 12 is in a neutral position, and each shift head 15 is in a central position. In this state, the first and second oil passages 31a and 31b are communicated with each other by the control recess 33 and communicated with the transmission case 10 through the discharge port 33a. The hydraulic oil supplied to the two supply passages 32a and 32b has a pressure of 0 downstream from the throttle portions 32a1 and 32b1, and the first and second oil passages 31a and 31b, and the first and second communication passages 31a1 and 31a1. The oil is discharged to the bottom in the transmission case 10 which is the reservoir 35a of the oil pump 35 through 31b1, the control recess 33 and the discharge port 33a.

  In this state, the shift and select shaft 20 is selectively moved in the axial direction by the shift lever to move the lever member 21 in parallel, and the tip 21a is moved in each groove 15a of each shift head 15 in the neutral position. Any one shift head 15 is selected. Next, when the shift and select shaft 20 is rotated counterclockwise by the shift lever and the lever member 21 is shifted, the selected fork shaft 12 moves the shift fork 13 engaged with the clutch hub of the transmission gear. 2, the shift head 15 moves to the right with respect to the fork shaft 12 against the elastic holding force of the first detent mechanism 16 as shown in FIG. It becomes the snap position on the first oil passage 31a side that comes into contact with. In this state, since the first oil passage 31a remains connected to the reservoir 35a via the control recess 33 and the discharge port 33a, the hydraulic pressure of the oil pump 35 is not applied to the first pressure chamber 30a. Since the oil passage 31b is cut off from the control recess 33 by the inner peripheral surface of the shift head 15, the hydraulic pressure of the oil pump 35 is applied to the second pressure chamber 30b, and the selected fork shaft 12 has a shift resistance of the transmission gear. Start to move to the right.

  If the lever member 21 is further swung in the counterclockwise direction by the shift lever, the shift head 15 and the fork shaft 12 that are in contact with each other via the retaining ring 19a move integrally to the right and move to FIG. The rightward force applied to the fork shaft 12 during the shift position on the side of the first oil passage 31a shown in the figure is the force F1 that the tip 21a of the lever member 21 pushes the fork shaft 12 through the shift head 15, 2 is the sum of the force F2 that presses the fork shaft 12 by the hydraulic pressure from the oil pump 35 applied to the pressure chamber 30b, and the force F1 applied to the lever member 21 for shifting, and hence the operating force applied to the shift lever, is the second pressure chamber. This is less than the force required to shift the transmission gear by the force F2 due to the hydraulic pressure applied to 30b.

  In this embodiment, at the shift position shown in FIG. 3, the lever member 21 is held at the maximum swinging position by the second detent mechanism 22, and is held in that position even when the hand is released from the shift lever. 2 The pressure in the pressure chamber 30b is held at the shift position. If the lever member 21 is returned to the center position by the shift lever from this state, the fork shaft 12 does not move lightly for the same reason as described above, and first resists the elastic holding force of the second detent mechanism 22 as shown in FIG. As a result, the lever member 21 swings in the clockwise direction, and the shift head 15 returns to the center position with respect to the fork shaft 12. In this state, the oil passages 31 a and 31 b communicate with each other by the control recess 33 as in the case of FIG. Thus, the pressure of the hydraulic fluid that is communicated with the transmission case 10 and supplied to both the supply paths 32a and 32b becomes zero. If the lever member 21 is further returned in the shift direction by the shift lever, the shift head 15 moves to the left with respect to the fork shaft 12 against the elastic holding force of the first detent mechanism 16 as shown in FIG. It becomes a snap position on the second oil passage 31b side that abuts on 19b. In this state, contrary to FIGS. 2 and 3, the hydraulic pressure of the oil pump 35 is not applied to the second pressure chamber 30 b, but the first oil passage 31 a is separated from the control recess 33 by the inner peripheral surface of the shift head 15. As a result, the hydraulic pressure of the oil pump 35 is applied to the first pressure chamber 30a, and the fork shaft 12 starts to move to the left against the shift resistance.

  When the lever member 21 is further swung in the clockwise direction by the shift lever, the shift head 15 and the fork shaft 12 that are integrally in contact with each other via the retaining ring 19b move leftward, and the second detent mechanism 22 is moved to the left. If the lever member 21 is stopped at the neutral position by the above, the neutral position shown in FIG. 1 is obtained. During this time, the leftward force applied to the fork shaft 12 is caused by the force F1 that the tip 21a of the lever member 21 pushes the fork shaft 12 through the shift head 15 and the hydraulic pressure from the oil pump 35 that is applied to the first pressure chamber 30a. This is the sum of the force F3 that presses the fork shaft 12, and the force F1 that is applied to the lever member 21 for shifting, and therefore the operating force that is applied to the shift lever, is that the transmission gear is applied by the amount of force F3 due to the hydraulic pressure applied to the first pressure chamber 30a. Less than the force required to return to the neutral position. The operation when the fork shaft 12 is shifted to the second oil passage 31b side from the neutral position and returned to the neutral position is substantially the same as that described above.

  As described above, the operating force applied to the lever member 21 for shifting is necessary for shifting the transmission gear by the amount of the force due to the hydraulic pressure of the oil pump 35 applied to the first or second pressure chamber 30a, 30b. Since the force is less than the force, the shift feeling can be improved by reducing the operating force applied to the lever member 21. Further, the transmission case 10, the fork shaft 12 and the shift head 15 which are the main members as compared with the prior art shown in FIGS. 8 and 9 can be used almost as they are, and what should be added is an oil pump 35, a first detent mechanism. 16 and the members and processing for constituting the oil passage, the processing of the oil passage with respect to the shift head 15, that is, the addition of the control recess 33 and the discharge port 33a is very simple, and is necessary for the implementation. Only a small increase in manufacturing costs is sufficient.

  In the above-described embodiment, the oil pump 35 is provided with a pressure adjusting function that can adjust the operating oil pressure manually or automatically according to the operating state. In this way, the oil pump 35 is manually operated according to the preference of the driver. Alternatively, the shift operation force can be automatically adjusted according to the traveling state such as the vehicle speed, and various shift feeling needs can be met.

  Next, a first modification of the above-described embodiment will be described with reference to FIG. The first modification is different from the above-described embodiment only in the structure in which the opening to the outer peripheral surface of the fork shaft 12 of the first and second oil passages 31a and 31b is opened and closed by the shift head 15. However, there is no discharge port 33a, and instead a pair of first and second discharge passages 34a, 34b are formed in the fork shaft 12, so this difference will be mainly described.

  As shown in FIG. 6, the first and second discharge passages 34 a and 34 b are a pair of groove-like recesses extending in the axial direction that are opened on the outer peripheral surface of the fork shaft 12, and the first and second oil passages. The first and second communication passages 31a1 and 31b1 communicated with the inner ends of 31a and 31b are formed immediately outside in the axial direction of the respective openings to the outer peripheral surface of the fork shaft 12. Therefore, in the first modified example, the first and second oil passages 31a and 31b are communicated by the control passage 33 at the same time when the shift head 15 is at the center position as shown in FIG. If the shift head 15 is moved to the snap position on the first oil passage 31a side as shown in FIG. 6 (b), the control recess 33 remains in communication with the first oil passage 31a. At the same time as communicating with the reservoir 35a via the discharge passage 34a, it is blocked from the second oil passage 31b by the inner peripheral surface of the shift head 15, and the shift head 15 is moved to the snap position on the second oil passage 31b. Then, the control recess 33 is communicated to the reservoir 35a side via the second discharge passage 34b while being communicated with the second oil passage 31b, and at the same time is blocked from the first oil passage 31a by the inner peripheral surface of the shift head 15. And it has a structure that is.

  In the state shown in FIG. 6A in which the shift head 15 is at the center position, the first and second oil passages 31a and 31b are communicated with each other by the control recess 33 and are blocked from the outside. 2 The hydraulic pressure of the oil pump 35 is applied to the pressure chambers 30 a and 30 b (see FIGS. 1 to 5) and the control recess 33. However, since the hydraulic pressure applied to the fork shaft 12 and the shift head 15 is balanced, the fork shaft 12 and the shift head 15 are not moved in any direction.

  In this state, as described above, if the lever member 21 is selectively moved in the axial direction, any one shift head 15 is selected by the tip 21a, and then the lever member 21 is shifted in the counterclockwise direction. As in the above-described embodiment, first, the shift head 15 moves to the right with respect to the fork shaft 12 to the snap position on the first oil passage 31a side, and further shifts in the counterclockwise direction to move to the second pressure chamber. Fork shaft 12 is shifted to the first oil passage 31a side by the hydraulic pressure generated in 30b. During this time, the operating force applied to the shift lever is less than the force required to shift the transmission gear by the amount of the hydraulic pressure applied to the second pressure chamber 30b. If the lever member 21 is returned from this state by the shift lever, the fork shaft 12 returns to the center position by the hydraulic pressure generated in the first pressure chamber 30a as in the above-described embodiment. The operation when the fork shaft 12 is shifted to the second oil passage 31b side from the neutral position and returned to the neutral position is substantially the same as that described above.

  Even in the first modified example, as described above, the operating force applied to the lever member 21 for shifting is reduced, so that the operating force applied to the lever member 21 can be reduced to improve the shift feeling. Further, compared with the prior art shown in FIGS. 8 and 9, the manufacturing cost required for the implementation is only slightly increased. In particular, according to the first modification, the hydraulic oil from the oil pump 35 is not discharged to the reservoir 35a side when the shift head 15 is in the center position with respect to the fork shaft 12. Energy consumption can be reduced.

  Next, a second modification of the above-described embodiment will be described with reference to FIG. The second modification is different from the above-described embodiment and the first modification only in the structure in which the opening to the outer peripheral surface of the fork shaft 12 of the first and second oil passages 31a and 31b is opened and closed by the shift head 15. The only difference is that the control recess 33 and the discharge port 33a constituting the control passage 33 are changed to the one composed of the two control passages 33b1 and 33b2, and the other structures are the same. I will explain the points. FIG. 7 shows a cross section that is 90 degrees different from those in FIGS. 1 to 5, and therefore the groove 15 a and the first detent mechanism 16 are not shown.

  As shown in FIG. 7, the first and second control passages 33b1 and 33b2 constituting the control passage 33 of the second modification are larger in diameter than the communication passages 31a1 and 31b1, and the wall surface of the shift head 15 is the inner peripheral surface. A pair of through-holes formed so as to extend parallel to each other in the radial direction from the outer surface to the outer surface thereof, the center distance thereof being smaller than the communication paths 31a1 and 31b1, and the shift head 15 being in the center position In the state shown in FIG. 7 (a), the communication passages 31a1 and 31b1 are opened on the inner sides of the respective inner peripheries of the control passages 33b1 and 33b2 in the vicinity of the separated positions. Accordingly, in the second modification, at the central position, the oil passages 31a and 31b are communicated with the reservoir 35a via the control passages 33b1 and 33b2, and the shift head 15 is connected to the first oil passage as shown in FIG. If the first oil passage 31a is communicated with the reservoir 35a via the first control passage 33b1, the second oil passage 31b is blocked by the inner peripheral surface of the shift head 15 if moved to the snap position on the side of the passage 31a. If the shift head 15 is moved to the snap position on the second oil passage 31b side, the second oil passage 31b remains in communication with the reservoir 35a via the second control passage 33b2, and the first oil passage 31a is connected to the shift head. The structure is cut off by 15 inner peripheral surfaces.

  In the state shown in FIG. 7A in which the shift head 15 is at the center position, each of the first and second oil passages 31a and 31b communicates with the reservoir 35a. The hydraulic oil supplied to the two oil passages 31a and 31b has a downstream pressure of 0 from the throttle portion provided in each supply passage (both see FIG. 1), and each of the oil passages 31a and 31b and the control passages. It is discharged to the reservoir 35a through 33b1 and 33b2.

  In this state, as described above, if the lever member 21 is selectively moved in the axial direction, any one shift head 15 is selected by the tip 21a, and then the lever member 21 is shifted in the counterclockwise direction. As in the above-described embodiment and the first modification, first, the shift head 15 moves rightward with respect to the fork shaft 12 to the snap position on the first oil passage 31a side, and further shifts in the counterclockwise direction. The fork shaft 12 is shifted to the first oil passage 31a side by the hydraulic pressure generated in the second pressure chamber 30b. During this time, the operating force applied to the shift lever is less than the force required to shift the transmission gear by the amount of the hydraulic pressure applied to the second pressure chamber 30b. If the lever member 21 is returned from this state by the shift lever, the fork shaft 12 returns to the center position by the hydraulic pressure generated in the first pressure chamber 30a as described above. The operation when the fork shaft 12 is shifted to the second oil passage 31b side from the neutral position and returned to the neutral position is substantially the same as that described above.

  Also in the second modified example, as described above, since the operating force applied to the lever member 21 for shifting is reduced, it is possible to improve the shift feeling by reducing the operating force applied to the lever member 21. Further, compared with the prior art shown in FIGS. 8 and 9, the manufacturing cost required for the implementation is only slightly increased. In particular, according to the second modification, the first and second control passages 33b1 and 33b2 forming the control passage 33 can be easily processed from the outside of the shift head 15, so that the manufacturing cost can be reduced. .

  In the above-described embodiment and each modified example, the selection motion for selecting one fork shaft 12 from the plurality of fork shafts 12 to 12 and the shift motion for switching the transmission gear by moving the selected fork shaft 12 in the axial direction. Although the lever member 21 provided on the shift and select shaft 20 has a parallel motion and a swing motion, the select motion and the shift motion may be a swing motion and a parallel motion of the lever member 21, respectively. In that case, the shift and select shaft 20 may be arranged in parallel with each fork shaft 12.

  In the above-described embodiment and each modification, each fork shaft 12 has been described as having a shift position on both sides of the neutral position, and each shift head 15 has a snap position on both sides of the center position. The fork shaft 12 and the shift head 15 corresponding thereto may be implemented by providing a shift position and a snap position only on one side.

  The gear transmission shift mechanism according to the present invention may be implemented by providing a detent mechanism (see reference numeral 6) similar to the prior art shown in FIG. 9 between each fork shaft 12 and the transmission case 10. In this case, the engaging recess 23a of the cam member 23 of the second detent mechanism 22 may be set only at the center position, and the engaging recess corresponding to the maximum swing position may be excluded.

It is sectional drawing along the axial direction of the fork shaft in the neutral position which shows the principal part of one Embodiment of the shift mechanism of the gear transmission by this invention. It is sectional drawing similar to FIG. 1 in the snap position of embodiment shown in FIG. It is sectional drawing similar to FIG. 1 in the shift position of embodiment shown in FIG. FIG. 2 is a cross-sectional view similar to FIG. 1 at one stage during the return of the embodiment shown in FIG. 1. FIG. 2 is a cross-sectional view similar to FIG. 1 at another stage during the return of the embodiment shown in FIG. 1. It is sectional drawing of the principal part which shows the 1st modification of embodiment shown in FIG. It is sectional drawing of the principal part which shows the 2nd modification of embodiment shown in FIG. It is a top view which shows an example of the shift mechanism of the gear transmission by a prior art. It is 9-9 sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Transmission case, 11 ... Cylinder hole, 12 ... Fork shaft, 13 ... Shift fork, 15 ... Shift head, 15a ... Groove part, 16 ... 1st detent mechanism, 20 ... Shift and select shaft, 21 ... Lever member, 21a ... tip portion, 22 ... second detent mechanism, 30a, 30b ... pressure chamber (first pressure chamber, second pressure chamber), 31a, 31b ... oil passage (first oil passage, second oil passage), 32a, 32b ... supply path (first supply path, second supply path), 33 ... control passage (control recess), 33a ... discharge port, 33b1, 33b2, ... control passage (first control passage, second control passage), 34a, 34b ... discharge passage (first discharge passage, second discharge passage), 35 ... oil pump, 35a ... reservoir.

Claims (5)

Shift forks for switching the transmission gears are provided and arranged parallel to each other, and are guided and supported in the transmission case so as to be movable in the axial direction between a shift position where power transmission by the transmission gear is performed and a neutral position where power transmission is not performed. In the state where each of the fork shafts and each of the fork shafts are in the neutral position, the fork shafts are respectively provided in the fork shafts so as to be aligned in a direction orthogonal to the axial direction and in the orthogonal direction. A plurality of shift heads formed with continuous grooves, a shift and select shaft guided and supported by the transmission case so as to be axially movable and rotatable along one side of the plurality of fork shafts; It is fixed to the select shaft and protrudes in the radial direction, and its tip part slides into each groove part. It comprises a lever member that is engaged,
Each of the shift heads provided on each of the fork shafts, the tip of which is located at the neutral position by any one of parallel movement and rocking accompanying axial movement and rotation of the shift and select shaft. The shift head selected by one of the parallel movement and the swing and the fork shaft provided with the shift head are moved in the axial direction. In a shift mechanism of a gear transmission that switches the transmission gear via the shift fork,
Each fork shaft is fitted and supported in a liquid-tight slidable manner in each pair of cylinder holes formed so that both ends thereof are coaxially opposed to the transmission case. First and second pressure chambers are formed between the pair of cylinder holes,
Each of the pressure chambers is supplied with hydraulic oil from an oil pump via the first and second supply paths,
The shift head is fitted and supported in a fluid-tight manner so that its inner peripheral surface is slidable between two snap positions at a certain distance in the axial direction on the outer peripheral surface of the axially intermediate portion of the fork shaft. A control passage opening in the inner peripheral surface is formed,
A first detent mechanism is provided between the fork shaft and the shift head to elastically hold the shift head with respect to the fork shaft at a central position of the two snap positions.
The lever member is provided with a second detent mechanism that elastically holds a fork shaft provided in the selected shift head in the neutral position in cooperation with the first detent mechanism,
The fork shaft is formed with a pair of first and second oil passages extending inward in the axial direction from both end faces thereof, and the inner ends of the oil passages are respectively opened on the outer peripheral surface of the fork shaft,
In a state where the shift head is held at the center position, both the oil passages are communicated with the control passage through an opening to the outer peripheral surface, and the shift head is in one of the snap positions. Then, the one oil passage located on the opposite side of the snap position is closed from the control passage by the opening to the outer peripheral surface being closed by the inner peripheral surface of the shift head, and the other oil passage is the outer peripheral surface. A gear transmission shift mechanism characterized in that it is configured to communicate with the control passage through an opening to the surface and communicate with the reservoir side of the oil pump from the control recess.   2. The gear transmission shift mechanism according to claim 1, wherein the oil pump has a pressure regulating function.   3. The shift mechanism of the gear transmission according to claim 1, wherein the control passage is a control recess that is opened at an axially intermediate portion of an inner peripheral surface of the shift head, and the control recess includes the control recess. A shift mechanism for a gear transmission, characterized in that a discharge port is provided for continuous communication with the reservoir side of the oil pump.   3. The shift mechanism of the gear transmission according to claim 1 or 2, wherein the control passage is a control recess opened at an axially intermediate portion of the inner peripheral surface of the shift head, and the fork shaft has an outer peripheral surface thereof. When the shift head is in the center position, the control recess is not communicated with the reservoir side of the oil pump, but when the shift head is in the snap position, a discharge passage is provided that communicates the control recess with the reservoir side. A shift mechanism for a gear transmission, characterized by that.   3. The shift mechanism for a gear transmission according to claim 1 or 2, wherein the control passages are formed so as to pass through the wall surface of the shift head in the radial direction from the inner peripheral surface toward the outer surface. The first oil passage communicates with the reservoir side of the oil pump via the first control passage when the shift head is in the snap position at the center position or the first oil passage side. And in the state of being in the snap position on the second oil passage side, the shift head is configured to be blocked from the reservoir side by the inner peripheral surface of the shift head, and the second oil passage has the shift head at the central position or the In the state at the snap position on the second oil passage side, it communicates with the reservoir side of the oil pump via the second control passage and at the first oil passage side. Shifting mechanism for a gear transmission in a state in serial snap position, characterized by being configured to be cut off from the reservoir side by the inner peripheral surface.

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