JP2014025499A - Shift fork and speed change gear including the same - Google Patents

Abstract

A shift fork that operates a synchronization mechanism in the axial direction of a shaft in order to switch the gear position of a transmission prevents an edge contact of a claw portion at the tip regardless of the amount of bending, and at a sliding portion A structure that does not easily cause oil film breakage.
A base end portion of a shift fork is supported by a shift rod and is inserted into an annular groove 121 formed in a sleeve 120 of a synchronization mechanism at each distal end portion. And a claw portion 320 extending in the circumferential direction. The slidable contact surface 320a slidably contacting the inner surface 121a of the annular groove 121 in the claw portion 320 is a convex curved surface having a convex middle portion in the extending direction of the claw portion 320.
[Selection] Figure 4

Description

  The present invention relates to a transmission such as an automobile, and more particularly to the structure of a shift fork of a shift shift mechanism.

  2. Description of the Related Art Conventionally, manual transmissions that select one of a plurality of shift stages by operating a shift lever by a driver are known as transmissions for automobiles and the like. In such a manual transmission, a plurality of transmission gears are arranged on a main shaft that receives input from the engine and a countershaft that is parallel to the main shaft, and meshed with each other to form a plurality of transmission gear trains. ing. Any one of the transmission gear trains transmits a driving force to establish a shift stage.

  That is, at least one of the main shaft and the countershaft is provided with a synchronization mechanism (for example, a synchromesh mechanism) for synchronizing the rotation of the freely rotating transmission gear with the rotation of the shaft, and the sleeve of this synchronization mechanism is shifted. The fork is operated toward the adjacent transmission gear to synchronize the rotation of the transmission gear with the rotation of the shaft, and then the transmission gear and the shaft are coupled.

  Specifically, the base end portion of the shift fork is supported by the shift rod, and a claw portion is provided at each of the tip portions divided into two. Then, the shift fork is positioned so as to sandwich the sleeve that rotates integrally with the shaft from the outer peripheral side, the two claw portions are respectively inserted into the annular grooves on the outer periphery of the sleeve, and the inner surface of the annular groove is pressed to press the shaft. It is moved in the axial direction.

  Here, since the claw portion of the shift fork is pressed against the inner surface of the annular groove of the rotating sleeve as described above, there is a risk of promoting wear. For example, when the shift lever is operated violently and the claw portion at the tip of the shift fork strongly presses the inner surface of the annular groove of the sleeve, in the conventional general shift fork F as shown schematically in FIG. This is because the claw portion C is inclined and the edge E on the base end side (side closer to the shift rod) bites into the inner side surface g1 of the annular groove G, so-called edge contact occurs.

  In this regard, the shift fork described in Patent Document 1 has a claw portion C having a tapered trapezoidal shape as schematically shown in FIG. In this way, when the shift fork F is bent relatively large as described above, the sliding contact surface S of the claw portion C inclined as shown in FIG.

JP 2002-310298 A

  However, in the claw portion having the shape as in the conventional example, the sliding contact surface S of the claw portion C that is originally inclined as shown in FIG. There is a risk that the leading edge E of the sword will hit the edge.

  Further, as shown in FIG. 10B, when the shift fork F is relatively greatly bent and the sliding contact surface S of the claw portion C is in a substantially uniform contact state, this time, the sliding contact surface S is now in contact with the sliding contact surface S. As a result, it becomes difficult to smoothly supply the lubricating oil, and there is a possibility that seizure may occur due to the oil film running out.

  In view of these points, an object of the present invention is to prevent the edge of the claw portion from being hit regardless of the amount of bending of the shift fork and to make it difficult to cause an oil film breakage on the sliding contact surface.

  In order to achieve the above-described object, the present invention is directed to a shift fork that operates a synchronization mechanism in the axial direction of a shaft on which a transmission gear is disposed in order to switch the gear position of the transmission. One end of which is supported by a shift rod parallel to the shaft, and each of the front end portions of the shift fork having a claw portion inserted into an annular groove formed in the sleeve of the synchronization mechanism And Each claw portion extends in the circumferential direction in the annular groove, and the slidable contact surface of the claw portion that is in slidable contact with the inner surface of the annular groove is a convex curved surface in which the intermediate portion is convex in the extending direction of the claw portion. It is characterized by being.

  Due to this specific matter, in order to switch the gear stage of the transmission, when the claw portion at the tip of the shift fork inserted in the annular groove of the sleeve of the synchronization mechanism is operated, the shift fork is bent by the reaction force, and the claw portion is It will be inclined in the annular groove of the sleeve. However, since the sliding surface of the claw portion inclined in this way is a convex curved surface, even if it is inclined as described above, the sliding contact portion with the inner surface of the annular groove only changes, and edge contact is unlikely to occur.

  In addition, the sliding contact portion between the sliding contact surface which is a convex curved surface and the inner surface of the annular groove changes depending on the inclination angle of the claw portion, that is, the degree of bending of the shift fork, which is advantageous in preventing wear. Further, since the distance between the sliding contact surface and the inner surface of the annular groove gradually increases as the distance from the sliding contact portion increases, the pressure of the lubricating oil flowing in the circumferential direction of the annular groove by the rotation of the sleeve is directed toward the sliding contact portion. A so-called wedge effect that gradually increases is obtained, and oil film breakage is prevented.

  That is, according to the present invention, it is possible to prevent the edge of the claw portion at the front end from hitting the edge of the shift fork and prevent the oil film from being cut off on the sliding contact surface.

  Preferably, the slidable contact surface may be a convex curved surface having a maximum convex portion on the tip side of the center portion in the direction in which the claw portion extends. The maximum convex portion becomes a sliding contact portion when the claw portion is not substantially inclined (that is, the shift fork is hardly bent), and the sliding contact portion is the base end of the claw portion as the claw portion is inclined. Move to the side. Therefore, if the maximum convex portion is positioned on the distal end side with respect to the central portion of the claw portion as described above, the sliding contact portion that moves to the proximal end side due to the inclination is likely to stay in the sliding contact surface, and the edge contact is more reliably performed. Can be prevented.

  Preferably, the sliding contact surface may be an arcuate convex curved surface in the direction in which the claw portion extends. In this way, even if the inclination angle of the claw portion changes according to the change in the degree of deflection of the shift fork, the gap between the slidable contact surface, which is a convex curved surface, and the inner surface of the annular groove, that is, the wedge shape between the two is constant. Therefore, the wedge effect can be stably obtained.

  In other words, the present invention can be said to be a transmission equipped with a shift fork as described above. This transmission includes at least two shafts parallel to each other and a plurality of transmission gear trains in which a plurality of transmission gears respectively disposed on these shafts are engaged with each other, and at least one of the shafts. And a synchronization mechanism that synchronizes the rotation of one of the transmission gears with the shaft, and operates the synchronization mechanism in the axial direction of the shaft to switch the shift stage. Shift forks. The base end of the shift fork is supported by a shift rod parallel to the shaft, while the front end of the shift fork divided into two is inserted into an annular groove formed in the sleeve of the synchronization mechanism. A claw portion extending in the circumferential direction is provided, and the sliding contact surface of the claw portion that is in sliding contact with the inner surface of the annular groove is a convex curved surface having a convex middle portion in the extending direction of the claw portion. Features.

  In such a transmission, it is preferable that the sliding contact surface of the claw portion at the front end of the shift fork is a convex curved surface having a maximum convex portion on the front end side of the center portion in the extending direction of the claw portion. In addition, even when the shift fork is bent to the maximum by the reaction force when operating the synchronization mechanism and the claw portion at the tip thereof is inclined to the maximum, the sliding groove of the claw portion has the inside of the annular groove. It is preferable that the sliding contact portion with the side surface exists.

  Specifically, for example, assuming the maximum value of the load applied to the shift fork when the shift lever is operated violently, considering the interference with the surroundings due to the deflection, the shift fork of the shift fork and the claw at its tip The allowable upper limit value of the inclination angle of the part is set. The size of the slidable contact surface may be determined so that the slidable contact surface includes the slidable contact portion with the inner surface of the annular groove of the sleeve even when the claw portion is inclined to the allowable upper limit value.

  According to the shift fork according to the present invention and the transmission including the shift fork, the sliding contact surface of the claw portion is a convex curved surface in consideration that the shift fork bends and the claw portion at the tip of the shift fork is inclined in accordance with the speed change operation. As a result, it is possible to prevent the claw portion from hitting the edge regardless of the inclination angle, and it is difficult for the oil film on the sliding contact surface to be cut off. Durability can be improved.

It is sectional drawing which shows the gear layout of the manual transmission which concerns on embodiment. It is sectional drawing which shows the engaging part of the fork shaft for 5 speeds, and the 3rd synchromesh mechanism. It is sectional drawing which looked at the shift fork and the shift rod in the axial direction of this shift rod. It is a figure which shows engagement with the sleeve of a shift fork typically, Comprising: (a) sees to the axial direction of a shift rod, (b) is each shown by b arrow of figure (a). It is a figure which shows typically the inclination state of the nail | claw part in the cyclic | annular groove | channel of a sleeve, Comprising: (a) shows the state which is not substantially inclined, (b) shows the state in which it inclined to the maximum substantially, respectively. FIG. 6 is a diagram corresponding to FIG. 4 according to a modified example. FIG. 6 is a diagram corresponding to FIG. 5 according to a modified example. It is a graph which shows the improvement of load resistance by this invention. FIG. 5B is a diagram corresponding to FIG. 5B related to a conventional general shift fork. FIG. 6 is a view corresponding to FIG. 5 relating to a conventional shift fork.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, as an example, a case where the present invention is applied to a synchronous mesh manual transmission (manual transmission) of 5 forward speeds and 1 reverse speed mounted on an FF (front engine / front drive) vehicle will be described. To do.

-Gear layout of manual transmission-
FIG. 1 shows a gear layout of the manual transmission T according to the present embodiment. This gear layout is housed in a transmission case (not shown), and is arranged in parallel with each other, a main shaft (transmission shaft) 1, a counter shaft 2 (transmission shaft), and a reverse shaft 3 (indicated by a two-dot chain line in FIG. 1). Is supported rotatably by the transmission case.

  The main shaft 1 is connected to a crankshaft of an engine (not shown) via a clutch mechanism, and a plurality of speed change gear trains 4 to 8 are provided between the main shaft 1 and the counter shaft 2. . That is, in FIG. 1, a first speed gear train 4, a second speed gear train 5, a third speed gear train 6, a fourth speed gear train 7 and a fifth speed gear train 8 are arranged in order from the right side to the left side. A reverse gear train 10 (10a, 10b) is also provided as a reverse gear train.

  The first speed gear train 4 includes a first speed drive gear 4a attached to the main shaft 1 so as to rotate integrally therewith, and a first speed driven gear 4b rotatably assembled to the counter shaft 2. The first speed drive gear 4a and the first speed driven gear 4b are meshed with each other.

  Similarly, the second gear train 5, the third gear train 6, the fourth gear train 7, and the fifth gear train 8 are also connected to the drive gears 5a, 6a, 7a, 8a on the main shaft 1 and the counter shaft 2, respectively. Driven gears 5b, 6b, 7b, 8b are meshed with each other. In each gear train, one of the drive gears 5a, 6a, 7a, 8a and the driven gears 5b, 6b, 7b, 8b is rotatably assembled to either the main shaft 1 or the counter shaft 2, and the other rotates integrally. It is attached to do.

  The shift speed is switched by operating synchromesh mechanisms 11 to 13 (synchronization mechanisms) by shift forks 31 to 33 (see FIG. 3) described later to transmit the driving force from the main shaft 1 to the counter shaft 2. This is done by selecting the gear train to be performed. In the illustrated example, three synchromesh mechanisms 11 to 13 are arranged on the main shaft 1 and the counter shaft 2.

  The first synchromesh mechanism 11 is provided on the counter shaft 2 between the first speed driven gear 4b and the second speed driven gear 5b. When the first synchromesh mechanism 11 operates toward the first-speed driven gear 4b, the first-speed driven gear 4b is connected to the countershaft 2 so as to rotate together, and between the first-speed drive gear 4a and the first-speed driven gear 4b, Power transmission from 1 to the countershaft 2 is performed (establishment of the first gear).

  On the other hand, when the first synchromesh mechanism 11 operates toward the second-speed driven gear 5b, the second-speed driven gear 5b is connected to the countershaft 2 so as to rotate together, and between the second-speed drive gear 5a and the second-speed driven gear 5b, Power transmission from the main shaft 1 to the counter shaft 2 is performed (establishment of the second gear).

  Similarly, the second synchromesh mechanism 12 is provided on the main shaft 1 between the third speed drive gear 6a and the fourth speed drive gear 7a. When the second synchromesh mechanism 12 operates toward the 3rd speed drive gear 6a, the 3rd speed drive gear 6a is connected to the main shaft 1 in a rotationally integrated manner, and between the 3rd speed drive gear 6a and the 3rd speed driven gear 6b, Power is transmitted from the main shaft 1 to the countershaft 2 (establishment of the third speed stage).

  Further, when the second synchromesh mechanism 12 operates toward the 4th speed drive gear 7a, the 4th speed drive gear 7a is connected to the main shaft 1 so as to rotate together, and between the 4th speed drive gear 7a and the 4th speed driven gear 7b. Thus, power transmission from the main shaft 1 to the counter shaft 2 is performed (establishment of the fourth speed stage).

  Further, the third synchromesh mechanism 13 is provided on the main shaft 1 adjacent to the fifth speed drive gear 8a. When the third synchromesh mechanism 13 operates toward the 5-speed drive gear 8a, the 5-speed drive gear 8a is connected to the main shaft 1 in a rotationally integrated manner, and between the 5-speed drive gear 8a and the 5-speed driven gear 8b, Power is transmitted from the main shaft 1 to the counter shaft 2 (establishment of the fifth gear).

  In this way, the rotational driving force of the main shaft 1 is transmitted to the counter shaft 2 via one transmission gear train 4 to 8 selected by the operation of any one of the synchromesh mechanisms 11 to 13 described above. The The rotational driving force transmitted to the counter shaft 2 in this manner is decelerated by the final reduction gear train 15 including the final drive gear 15a and the final driven gear 15b, and then transmitted to the differential device 16.

-Shifting operation mechanism-
In order to perform the above-described speed change operation, the manual transmission T according to the present embodiment includes a speed change operation mechanism for operating the selected synchromesh mechanisms 11 to 13 in accordance with an operation of a shift lever (not shown). Yes. Although only the third synchromesh mechanism 13 is shown in FIG. 2, three shift forks 31 to 33 (see FIG. 3) are arranged corresponding to the respective synchromesh mechanisms 11 to 13, each of which is a shift rod. 51-53.

  FIG. 2 shows an engagement portion between the fifth speed shift rod 53 and the third synchromesh mechanism 13. The shift rod 53 has a base end portion of the shift fork 33 through a boss portion 33 a indicated by a two-dot chain line. Is attached. On the other hand, a claw portion 330 (see FIG. 3) is formed at the tip of the shift fork 33 and is inserted into an annular groove 131 formed on the outer periphery of the sleeve 130 of the third synchromesh mechanism 13.

  FIG. 3 shows three shift forks 31 to 33 supported respectively on the three shift rods 51 to 53 in the axial direction, and a mechanism 55 (inner member 55a) for selecting and operating one of them. FIG. 5 is a cross-sectional view taken around the interlock member 55b and the like. As is well known, the operation of the shift lever (not shown) is transmitted to the select control lever 55c via a cable or the like (not shown), and the shift select shaft 50 rotates around the axis in response to the select operation of the shift lever. Slide in the axial direction according to the operation.

  Then, when the shift select shaft 50 is rotated, for example, a 5-speed shift rod 53 is selected, and when the 5-speed shift rod 53 is moved in the axial direction by the sliding movement of the shift select shaft 50, as shown in FIG. In addition, the shift fork 33 supported by the fifth speed shift rod 53 operates the sleeve 130 of the third synchromesh mechanism 13 to be engaged.

  Since the manual transmission according to this embodiment is in the fifth forward speed, the third synchromesh mechanism 13 is provided with a transmission gear (fifth speed drive gear 8a) only on one side (right side in FIG. 2). However, the first synchromesh mechanism 11 and the second synchromesh mechanism 12 are provided with transmission gears on both sides thereof (see FIG. 1). Except for this point, the engagement portion between the shift rod 51 for the first and second speeds and the first synchromesh mechanism 11 and the engagement between the shift rod 52 for the third and fourth speeds and the second synchromesh mechanism 12. The joint part has the same structure.

  Since the structures of the first, second and third synchromesh mechanisms 11 to 13 are the same, the third synchromesh mechanism 13 shown in FIG. 2 will be briefly described. First, for example, the clutch hub 17 is spline-fitted so as to rotate integrally with the main shaft 1, and the sleeve 130 is spline-fitted on the outer peripheral side thereof. That is, the sleeve 130 rotates integrally with the main shaft 1 via the clutch hub 17 and is slidable in the axial direction of the main shaft 1.

  On the other hand, a gear piece 8c is spline-fitted to the 5-speed drive gear 8a adjacent to the clutch hub 17 so as to rotate integrally. Since the gear piece 8c is not engaged with the clutch hub 17 in the state shown in FIG. 2, the gear piece 8c and the fifth speed drive gear 8a are not connected to the clutch hub 17 when the third synchromesh mechanism 13 is not operating. Relative rotation is possible.

  The gear piece 8c is provided with a cone portion, and a synchronizer ring 14 is fitted on the outer peripheral side thereof. The synchronizer ring 14 includes a cone portion having a tapered inner peripheral surface corresponding to the cone portion of the gear piece 8c, and the rotation of the gear piece 8c and the clutch hub 17 is synchronized by the contact between the two cone portions. be able to.

  That is, as described above, when the shift fork 33 is operated by the 5-speed shift rod 53 and the sleeve 130 of the synchromesh mechanism 13 is moved toward the 5-speed drive gear 8a, the rotation is first synchronized by the synchronizer ring 14. Thereafter, when the sleeve 130 meshes with the gear piece 8c, the fifth speed drive gear 8a rotates integrally with the clutch hub 17, that is, the main shaft 1.

-Claw part of shift fork-
As described above, the shift forks 31 to 33 for operating the synchromesh mechanisms 11 to 13 have a horseshoe shape surrounding the outer half of the sleeves 110, 120, and 130 as shown in FIGS. And each base end part of the shift forks 31-33 is supported by the shift rods 51-53 which penetrates the boss | hub part 33a.

  On the other hand, at the tip of the shift forks 31 to 33 divided into two branches, the annular grooves of the sleeves 110, 120 and 130 of the synchromesh mechanisms 11 to 13 (the annular groove 121 of the sleeve 120 is shown in FIG. Claw portions 310, 320, and 330 are provided to be inserted into the groove 131 (shown in FIG. 2 respectively).

  Here, the shift fork 33 supported by the 5-speed shift rod 53 among the three shift forks 31-33 operates the third synchromesh mechanism 13 only on the one-side 5-speed drive gear 8a. The claw portion 330 is also configured to be in contact with only one side of the 5-speed drive gear 8a. Except for this point, the three shift forks 31 to 33 have substantially the same structure. The shift fork 32 that operates the sleeve 120 of the mesh mechanism 12 will be described in detail.

  First, as described above, when the gear position is switched, the claw portion 320 at the tip of the shift fork 32 is pressed against the inner side surface 121a of the annular groove 121 of the sleeve 120 into which the shift fork 32 is inserted. For example, in the case of the second synchromesh mechanism 12, if the sleeve 120 is moved to the adjacent third speed drive gear 6a side, the third speed stage is established, and the second synchromesh mechanism 12 can be moved to the adjacent fourth speed drive gear 7a side. 4th gear is established.

  In this way, when switching to the 3rd speed stage or the 4th speed stage, the main shaft 1 that receives the rotational force from the engine normally rotates at a high speed, and the clutch hub 17 and the sleeve 120 also rotate together with this. Therefore, when the inner surface 121a of the annular groove 121 of the sleeve 120 is pressed by the claw portion 320 of the shift fork 32, the sliding contact surface 320a of the claw portion 320 slides while receiving a load.

  For example, when the shift lever is operated violently when shifting down from the fourth speed to the third speed, the load between the inner surface 121a of the annular groove 121 of the sleeve 120 and the sliding contact surface 320a of the claw portion 320 increases. In the conventional general shift fork F schematically shown in FIG. 9, the claw C is inclined by the bending, and the edge E on the base end side (the side closer to the shift rod) of the sliding contact surface S is the annular groove G. There was a risk of wear being promoted by the so-called edge hitting that bites into the inner surface g1.

  In this regard, in the manual transmission T of the present embodiment, as shown for the shift fork 32 in FIG. 4, the pawl of the shift fork 32 inserted into the annular groove 121 of the sleeve 120 and extending in the circumferential direction (vertical direction in the figure). In the portion 320, the sliding contact surface 320 a that is in sliding contact with the inner side surface 121 a of the annular groove 121 is an arc-shaped convex curved surface whose central portion is the maximum convex portion in the extending direction of the claw portion 320.

  Thus, first, as shown in FIG. 5 (a), in the state where the claw portion 320 is not inclined, the sliding contact surface 320a of the claw portion 320 has an annular portion of the sleeve 120 at the central portion which is the maximum protrusion. It is in sliding contact with the inner surface 121a of the groove 121. The distance between the inner surface 121a of the annular groove 121 and the sliding contact surface 320a gradually increases as the distance from the sliding contact portion increases toward the distal end side and the proximal end side.

  That is, a wedge-shaped gap W is formed between the inner side surface 121 a of the annular groove 121 of the sleeve 120 and the sliding contact surface 320 a of the claw portion 320. Accordingly, as indicated by an arrow F in FIG. 5A, the pressure of the lubricating oil flowing in the circumferential direction of the annular groove 121 (from the bottom to the top in the figure) by the rotation of the sleeve 120 is slidably contacted in the wedge-shaped gap W. A so-called wedge effect that gradually increases toward the part is obtained, and oil film breakage hardly occurs.

  As described above, when the shift lever is operated violently during the downshift from the fourth gear to the third gear, the shift fork 32 is bent as shown in FIG. In the groove 121, the claw portion 320 of the shift fork 32 is inclined so as to fall rightward in the drawing. However, even if the claw portion 320 is inclined in this way, the sliding contact portion between the sliding contact surface 320a of the claw portion 320 which is a convex curved surface and the inner side surface 121a of the annular groove 121 only moves to the proximal end side. The edge hit as described with reference to FIG.

  In addition, the sliding contact portion between the sliding contact surface 320a that is a convex curved surface and the inner side surface 121a of the annular groove 121 depends on the degree of inclination (inclination angle) of the claw portion 320 that is inclined as described above, that is, how the shift fork 32 is bent. This is advantageous in preventing wear of the inner surface 121a of the annular groove 121.

  Furthermore, in this embodiment, since the sliding contact surface 320a is formed in an arc shape in the extending direction of the claw portion 320, even if the degree of inclination of the claw portion 320 changes as described above, the arc shape The wedge shape of the gap W between the slidable contact surface 320a and the inner surface 121a of the annular groove 121 is kept constant. For this reason, the wedge effect which affects the flow of the lubricating oil between the sliding contact surface 320a of the claw part 320 and the inner surface 121a of the annular groove 121 can be stably obtained.

  In the present embodiment, the shift fork is assumed in consideration of the magnitude of the load applied to the shift fork 32 when the shift lever is operated violently as described above, and considering the interference with the surroundings due to the bending thereof. 32, that is, an allowable upper limit value of the inclination angle of the claw portion 320 at the tip thereof is set. The size of the slidable contact surface 320a is set so as to include the slidable contact portion with the inner surface 121a of the annular groove 121 even when the claw portion 320 is inclined to the allowable upper limit value.

  Thus, even if the degree of bending of the shift fork 32 and the degree of inclination of the claw 320 at the tip thereof vary depending on how the shift lever is operated or the engine speed is different (for example, the claw 320 is maximum). Even in a tilted state), the sliding contact portion with the inner surface 121a of the annular groove 121 exists in the sliding contact surface 320a of the claw portion 320, and the above-described effects can be obtained more reliably.

-Modification-
6 and 7 show a modification of the shift fork 32. As shown for the shift fork 32 in the figure, the shift forks 31, 32, and 33 of this modification have the sliding contact surface 320 b of the claw portion 320 maximally at the front end side with respect to the center portion in the extending direction of the claw portion 320. An arc-shaped convex curved surface having a convex portion is formed. Except for this point, the structure of the shift fork 32 is the same as that of the above-described embodiment, and the structure of the other manual transmission T is also the same. .

  According to this modification, as shown in FIG. 7A, when the shift fork 32 is not substantially bent (the claw portion 320 is not substantially inclined), the maximum convex portion of the sliding contact surface 320b, that is, the sleeve 120. The sliding contact portion with the inner surface 121a of the annular groove 121 is located closer to the tip end side of the sliding contact surface 320b. For this reason, as shown in FIG. 7 (b), as the flexure increases and the inclination of the claw portion 320 increases, the sliding contact portion of the sleeve 120 with the inner surface 121a of the annular groove 121 changes the position of the claw portion 320. Even if it moves to the base end side (upper side in the figure), the sliding contact portion tends to stay in the sliding contact surface 320b.

  That is, in this modified example as well, the edge contact of the claw portion 320 at the tip can be prevented regardless of the amount of bending of the shift fork 32, and the oil film cut off of the sliding contact surface 320b is also effective. Can be prevented. In addition to this, the allowable upper limit value of the inclination angle of the claw 320 so that the sliding contact surface 320b does not hit the edge, in other words, the allowable upper limit value of the deflection of the shift fork 32 is increased. Can be prevented.

  FIG. 8 shows the maximum load that can maintain the oil film of the lubricating oil in the gap W between the sliding contact surface 320b of the claw portion 320 of the shift fork 32 and the inner surface 121a of the annular groove 121 of the sleeve 120 in the modified example. It is a graph figure of the result calculated | required by experiment. As illustrated in FIG. 9, in the conventional claw portion C, the maximum load is suppressed to about 300 N due to edge contact or poor lubrication, but in the above modification, the load resistance is improved up to about four times. ing.

-Other embodiments-
In the above-described embodiment, the case where the present invention is applied to a five-speed transmission for an FF vehicle is described as an example. However, the present invention is not limited to this, and other than the five-speed for FR and RR vehicles. The present invention can be applied to a multi-stage transmission, and is not limited to a manual transmission, and can be applied to various transmissions such as DCT (Dual Clutch Transmission).

  In the above-described embodiment, the central portion of the sliding contact surface 320a of the claw portion 320 of the shift fork 32 is set as the maximum protruding portion. On the other hand, in the modified example, the maximum protruding portion is shifted toward the tip of the sliding contact surface 320a. For example, the maximum protrusion may be shifted toward the base end of the sliding contact surface 320a.

  Furthermore, it is not necessary to form the slidable contact surfaces 320a and 320b in an arc shape in the extending direction of the claw portion 320 as in each of the above-described embodiments, and may be a parabolic shape or an elliptic curve shape, for example. Further, not only the direction in which the claw portion 320 extends but also the width direction orthogonal thereto may be curved, and in this case, the sliding contact surfaces 320a and 320b may be spherical.

  INDUSTRIAL APPLICABILITY The present invention can improve the wear resistance of the claw portion of the shift fork and thereby improve the durability of the transmission, and is highly effective when applied to a manual transmission of a vehicle.

T Manual transmission (transmission)
1 Main shaft (shaft with transmission gear)
2 Countershaft (shaft on which transmission gears are installed)
4-8 Multi-stage transmission gear trains 4a-8a Drive gear (transmission gear)
4b-8b Driven gear (transmission gear)
11-13 Synchromesh mechanism (synchronous mechanism)
110, 120, 130 Sleeve 120a, 130a Annular groove 31-33 Shift fork 310, 320, 330 Claw part 320a Sliding surface 51-53 Shift rod

Claims (6)

A shift fork that operates a synchronization mechanism in the axial direction of a shaft on which a transmission gear is disposed in order to switch a gear stage of a transmission,
The base end portion is supported by a shift rod parallel to the shaft, and the bifurcated tip portion has a claw portion inserted into an annular groove formed in the sleeve of the synchronization mechanism,
Each of the claw portions extends in the circumferential direction in the annular groove, and the slidable contact surface of the claw portion that is in slidable contact with the inner surface of the annular groove is a convex curved surface in which the intermediate portion is convex in the extending direction of the claw portion. A shift fork characterized by that. The shift fork according to claim 1, wherein
A shift fork in which the slidable contact surface is a convex curved surface having a maximum convex portion on the tip side of the center portion in the direction in which the claw portion extends. The shift fork according to claim 1 or 2,
A shift fork in which the sliding contact surface is an arcuate convex curved surface in the direction in which the claw portion extends. At least two shafts parallel to each other;
A plurality of transmission gear trains formed by meshing a plurality of transmission gears respectively disposed on the shaft;
A synchronization mechanism provided in at least one of the shafts so as to be operable in an axial direction, and for synchronizing the rotation of any one of the transmission gear trains with the shaft;
A shift fork that operates the synchronization mechanism in the axial direction of the shaft in order to switch the gear position,
While the base end portion of the shift fork is supported by a shift rod parallel to the shaft, the front end portion of the bifurcated shift fork is inserted into an annular groove formed in the sleeve of the synchronization mechanism, and is Claw portion extending in the direction is provided,
The transmission according to claim 1, wherein the sliding contact surface of the claw portion that is in sliding contact with the inner side surface of the annular groove is a convex curved surface having a convex middle portion in the extending direction of the claw portion. The transmission according to claim 4,
A transmission in which a sliding contact surface of a claw portion at a tip of the shift fork is a convex curved surface having a maximum convex portion on a tip side of the center portion in a direction in which the claw portion extends. The transmission according to any one of claims 4 and 5,
Even in a state where the shift fork is maximally bent by a reaction force when operating the synchronization mechanism and the claw portion at the tip thereof is inclined to the maximum, the inner surface of the annular groove is placed in the sliding contact surface of the claw portion. A transmission that is configured to have a sliding contact portion.

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