Changing system in manual transmission

A changing system in a manual transmission is provided. An interlock plate is mounted on a shift-selecting shaft capable of being moved axially in response to a selecting operation and turned about an axis in response to a shifting operation, so that the interlock plate cannot be turned about an axis of the shift-selecting shaft. The interlock plate has a pair of side plate portions which are provided at locations spaced apart from each other in an axial direction of the shift-selecting shaft and through which the shift-selecting shaft extends. A shifting arm disposed between the side plate portions is fixed to the shift-selecting shaft. In such changing system, the shifting arm and an interlock member operatively connected to the shifting arm are interposed between the side plate portions of the interlock plate. Thus, the shifting arm can be used commonly in manual transmissions, in despite of a difference in number of forward speed stages between the manual transmissions, thereby providing a reduction in cost and avoiding an increase in weight due to a variation in number of forward speed stages.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a changing system in a manual transmission in which an interlock plate is mounted on a shift-selecting shaft capable of being moved axially in response to a selecting operation and turned about an axis in response to a shifting operation, so that the interlock plate cannot be turned about the axis of the shift-selecting shaft, the interlock plate having a pair of side plate portions which are provided at locations spaced apart from each other in the direction of the axis of the shift-selecting shaft and through which the shift-selecting shaft extends, and a shifting arm disposed between the side plate portions is fixed to the shift-selecting shaft.

2. Description of the Related Art

Such a system is conventionally known, for example, from Japanese Patent Application Laid-open No. 2001-116142.

In a changing system in a manual transmission having five forward speed stages, a mis-operation preventing reverse locking cam is provided on a shifting arm for preventing the shifting from a fifth speed stage to a reverse speed stage from being conducted directly. On the other hand, in a changing system in a manual transmission having six forward speed stages, there is not a possibility that the shifting from a six speed stage to a reverse speed stage is conducted directly and hence, it is not required that the mis-operation preventing reverse locking cam is provided on the shifting arm. It is a conventional practice that the shape of the shifting arm is greatly varied depending on the number of forward speed stages, or the shifting arm is used commonly with the mis-operation preventing reverse locking cam left as an unnecessary portion in the manual transmission having the six forward speed stages.

In the conventional approach as described above depending on a difference in number of the forward speed stages, there is a possibility that an increase in manufacture cost is brought about, and an increase in weight of the transmission is also brought about due to the remaining unnecessary portion.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a changing system in a manual transmission, wherein the shifting arm is used commonly irrespective of a difference in number of forward speed stages, thereby providing a reduction in cost and preventing an increase in weight due to the variation in number of forward speed stages.

To achieve the above object, according to a first aspect and feature of the present invention, there is provided a changing system in a manual transmission in which an interlock plate is mounted on a shift-selecting shaft capable of being moved axially in response to a selecting operation and turned about an axis in response to a shifting operation, so that the interlock plate cannot be turned about the axis of the shift-selecting shaft, the interlock plate having a pair of side plate portions which are provided at locations spaced apart from each other in the direction of the axis of the shift-selecting shaft and through which the shift-selecting shaft extends, and a shifting arm disposed between the side plate portions is fixed to the shift-selecting shaft, wherein a shifting arm and an interlock member operatively connected to the shifting arm are interposed between the side plate portions of the interlock plate.

With such arrangement of the first feature, a reduction in cost can be provided by using the shifting arm commonly in changing systems in a plurality of manual transmissions having different numbers of forward speed stages. Moreover, the interlock member is selected and operatively connected to the shifting arm. Therefore, it is possible to prevent an increase in weight due to an unnecessary portion left in the shifting arm, by ensuring that a function required for the shifting arm in such a manner that it is varied depending on the number of forward speed stages, is performed by the interlock member.

According to a second aspect and feature of the present invention, in addition to the first feature, as said interlock member, a first interlock member operated to establish a reverse speed stage and a second interlock member functioning to prevent the turning of the shifting arm from a forward highest-speed stage to the reverse speed stage are selected and one of said first and second interlock member is selected alternatively depending on the number of forward speed stages in such a manner that the first interlock member is selected when the number of forward speed stages is an even number, and the second interlock member is selected when the number of forward speed stages is an odd number. With such arrangement, the interlock member can be selected appropriately in any of the changing systems in the manual transmissions having the even number of forward speed stages and the odd number of forward speed stages, and a satisfactory function can be exhibited in each of the changing systems.

According to a third aspect and feature of the present invention, in addition to the second feature, a plurality of shifting pieces are disposed in parallel in a direction along the axis of the shift-selecting shaft and capable of being alternatively brought into engagement with the shifting arm depending on the selecting operation, and the first interlock member is operatively connected to the shifting arm in such a manner that preselected one of the forward speed stage shifting pieces is driven by a predetermined amount at an initial stage of a shifting operation to a reverse position and returned to an original position at a final stage of the shifting operation. With such arrangement, when the shifting arm is driven toward the reverse position in order to establish the reverse speed stage, the preselected forward speed stage shifting piece is driven by the predetermined amount at the initial stage of the shifting operation by the first interlock member operated in operative association with the shifting arm, and hence, a main shaft is braked as when a predetermined forward speed stage is established, and the braking of the main shaft is released at a final stage of the shifting operation. Therefore, an exclusive mechanism for the reverse speed stage is not required, and the main shaft can be braked temporarily during establishment of the reverse speed stage to prevent the generation of a gear chattering. Additionally, it is possible to provide the compactness of the manual transmission in a direction along an axis of the main shaft and to provide a reduction in weight of the manual transmission by a value corresponding to that the exclusive mechanism is not required.

According to a fourth aspect and feature of the present invention, in addition to the third feature, the interlock plate capable of being moved in the axial direction of the shift-selecting shaft and incapable of being turned about an axis is mounted to the shift-selecting shaft to cover a portion of the interlock arm and a portion of said first interlock member, and the interlock plate is provided with a recess adapted to accommodate a portion of the preselected forward speed stage shifting piece driven by the predetermined amount at the initial stage of the shifting operation. With such arrangement, the braking of the main shaft can be achieved reliably by ensuring that the preselected forward speed stage shifting piece is operated reliably by the predetermined amount during the establishment of the reverse speed stage.

The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described by way of an embodiment with reference toFIGS. 1to15. Referring first toFIG. 1, a transmission case11of a manual transmission M for a vehicle having an even number of, e.g., six forward speed stages and one backward speed stage, is comprised of a right case half12and a left case half13separated from each other at a split surface extending in a longitudinal direction of a vehicle body. An engine E is connected to one end of a main shaft SM through a shifting clutch CL. The main shaft SM is rotatably supported on the right and left case halves12and13with ball bearings14and15interposed therebetween. A counter shaft SC parallel to the main shaft SM is rotatably supported at its axially one end to the right case half12through a roller bearing16, and at the axially other end to the left case half13through a ball bearing17.

The counter shaft SC is formed into a cylindrical shape, so that a lubricating oil can flow through the counter shaft SC. A guide member19is mounted at one end of the counter shaft SC for guiding the oil from an oil passage18defined in the right case half12into the counter shaft SC. An oil passage20is defined in the left case half13to communicate with the other end of the counter shaft SC, and a bolt22is threadedly engaged into the left case half13and has a collar22aclamping an inner race of the ball bearing17between the collar22aitself and a step21formed on an outer periphery of the other end of the counter shaft SC. The cylindrical bolt22for flowing of the lubricating oil therethrough is screwed into an inner periphery of the other end of the counter shaft SC in order to fix the inner race of the ball bearing17, whereby a distance between the other end of the counter shaft SC and the left case half13can be set at a small value, and a reduction in size of the transmission case11can be achieved. Further, an oil passage23is coaxially provided in the main shaft SM with one end closed and with the other end opening into the other end of the main shaft SM. A guide member24for guiding the oil from the oil passage20in the left case half13into the oil passage23is mounted at the other end of the main shaft SM.

The shifting clutch CL includes a clutch wheel25fixedly connected to a crankshaft of the engine E, a pusher plate26disposed on one side of the clutch wheel25, a clutch disk28which has facings27,27on opposite surfaces thereof and which is interposed between the clutch wheel25and the pusher plate26and connected to the main shaft SM through a damper29, and a diaphragm spring30for biasing the pusher plate26in a direction to clamp the facings27,27between the clutch wheel25and the pusher plate26. In a usual state of the shifting clutch CL, the crankshaft25and the main shaft SM are connected to each other by clamping the facings27,27between the clutch wheel25and the pusher plate26by the repulsing force of the diaphragm spring30. In the shifting conducted by the shifting clutch, the crankshaft and the main shaft SM are disconnected from each other by operating a release bearing32leftwards as viewed inFIG. 1by a release fork31.

A main first-speed gear34and a main second-speed gear35are fixedly mounted on the main shaft SM, and a main third-speed gear36, a main fourth-speed gear37, a main fifth-speed gear38and a main sixth-speed gear39are relatively rotatably supported on the main shaft SM. On the other hand, a counter first-speed gear40and a counter second-speed gear41are relatively supported on the counter shaft SC and meshed with the main first-speed gear34and the main second-speed gear35, respectively. A counter third-speed gear42, a counter fourth-speed gear43, a counter fifth-speed gear44and a counter sixth-speed gear45are fixedly mounted on the counter shaft SC and meshed with the main third-speed gear36, the main fourth-speed gear37, the main fifth-speed gear38and the main sixth-speed gear39.

A reverse idling shaft SR parallel to the main shaft SM and the counter shaft SC is fixedly supported at its opposite ends on the right and left case halves12and13. A reverse idling gear46slidably supported on the reverse idling shaft SR can be meshed simultaneously with a main reverse gear47fixedly mounted on the main shaft SM and a counter reverse gear48relatively non-rotatably supported on the counter shaft SC.

A first/second-speed synchronizing mechanism S1mounted on the counter shaft SC includes a sleeve49which is movable in a range limited in an axial direction of the counter shaft SC and which is non-rotatable relative to the counter shaft SC. Any of the counter first-speed gear40and the counter second-speed gear31can be selected alternatively and coupled to the counter shaft SC by operating a first/second-speed shifting fork50retaining the sleeve49leftwards or rightwards as viewed in FIG.1. More specifically, when the sleeve49is moved rightwards as viewed inFIG. 1, the counter first-speed gear40is coupled to the counter shaft SC, thereby establishing a first speed stage. When the sleeve49is moved leftwards as viewed inFIG. 1, the counter second-speed gear41is coupled to the counter shaft SC, thereby establishing a second shift stage. The counter reverse gear48is integrally formed on the sleeve49.

A third/fourth speed synchronizing mechanism S2mounted on the main shaft SM includes a sleeve51which is movable in a range limited in an axial direction of the main shaft SM and which is non-rotatable relative to the main shaft SM, so that any of the main third-speed gear36and the main fourth-speed gear37can be selected alternatively and coupled to the main shaft SM by operating a third/fourth-speed shifting fork52retaining the sleeve51leftwards or rightwards as viewed in FIG.1. More specifically, when the sleeve51is moved rightwards as viewed inFIG. 1, the main third-speed gear36is coupled to the main shaft SM, thereby establishing a third shift stage. When the sleeve51is moved leftwards as viewed inFIG. 1, the main fourth-speed gear37is coupled to the main shaft SM, thereby establishing a fourth speed stage.

A fifth/sixth-speed synchronizing mechanism S3mounted on the main shaft SM includes a sleeve53which is movable in a range limited in the axial direction of the main shaft SM and which is non-rotatable relative to the main shaft SM, so that any of the main fifth-speed gear38and the main sixth-speed gear39can be selected alternatively and coupled to the main shaft SM by operating a fifth/sixth-speed shifting fork54retaining the sleeve53leftwards or rightwards as viewed in FIG.1. More specifically, when the sleeve53is moved rightwards as viewed inFIG. 1, the main fifth-speed gear38is coupled to the main shaft SM, thereby establishing a fifth speed stage. When the sleeve53is moved leftwards as viewed inFIG. 1, the main sixth-shift gear39is coupled to the main shaft SM, thereby establishing a sixth speed stage.

The reverse idling gear46is rotatably retained on a reverse shifting fork55, so that it can be meshed with the main reverse gear47and the counter reverse gear48by sliding the reverse idling gear46from a position shown by a solid line inFIG. 1to a position shown by a dashed line inFIG. 1by the reverse shifting form55, thereby establishing a reverse speed stage.

When one of the first to sixth speed stages and the reverse speed stage is established selectively in the above-described manner, the rotation of the counter shaft SC is transmitted to a differential58through a final driving gear56and a final driven gear57and further to a right axle65and a left axle66from the differential58.

A change lever L of a changing system for selectively establishing one of the first to sixth speed stages and the reverse speed stage is operated in an operating pattern shown inFIG. 2, so that the change lever L can be moved to any of a first/second-speed selecting position P1, a third/fourth-speed selecting position P2, a fifth/sixth-speed selecting position P3and a reverse selecting position P4by operating the change lever L in a selecting direction shown by SE. In addition, any of a first-speed position D1and a second-speed position D2can be selected by operating the change lever L in a shifting direction SH perpendicular to the selecting direction SE in the first/second-speed selecting position P1. Any of a third-speed position D3and a fourth-speed position D4can be selected by operating the change lever L in the shifting direction SH in the third/fourth-speed selecting position P2. Any of a fifth-speed position D5and a sixth-speed position D6can be selected by operating the change lever L in the shifting direction SH in the fifth/sixth-speed selecting position P3. Further, a reverse position R can be selected by operating the change lever L in the shifting direction SH in the reverse selecting position P4.

Referring toFIGS. 3 and 4, a cover member71is coupled to an upper portion of the left case half13in the transmission case11to cover an opening70provided in the left case half13, and a guide bore72is provided in a central portion of the cover member71. An upper portion of a shift-selecting shaft73is fitted into the guide bore72to protrude upwards from a cover plate71, so that the shift-selecting shaft73can be turned about its axis and slid in an axial direction. A seal member74is interposed between the cover member71and the shift-selecting shaft73.

An engagement bore75is provided in the shift-selecting shaft73at a portion protruding upwards from the cover member71, and a selecting lever76is engaged in the engagement bore75. The selecting lever76is secured to a turning shaft77extending in a direction perpendicular to the axis of the shift-selecting shaft73. The turning shaft77is turnably supported on a casing78fixedly mounted on the cover member71.

The selecting lever76is turned in response to the operation of the change lever L in the selecting direction SE (see FIG.2). The selecting lever76is turned to any of the first/second-speed selecting position P1, the third/fourth-speed selecting position P2, the fifth/sixth-speed selecting position P3and the reverse selecting position P4, as shown inFIG. 3, by the movement of the change lever L to any of the first/second-speed selecting position P1, the third/fourth-speed selecting position P2, the fifth/sixth-speed selecting position P3and the reverse selecting position P4. The shift-selecting shaft73is also moved linearly in a direction of its axis in response to the turning of the selecting lever76.

A first cam79is fixed to the turning shaft77within the casing78, and a second cam80having an axis parallel to the turning shaft77is fixedly provided on a shaft81which is turnably supported in the casing78and is meshed with the first cam79. A first flat abutment face79aand a second abutment face79bleading to the first abutment79aat a right angle are formed on the first cam79to face the second cam80. The first flat abutment face79ais adapted to perpendicularly intersect a plane including the axis of the shaft81, when the turned position of the selecting lever76turned in unison with the turning shaft77is the fifth/sixth-speed selecting position. The second cam80is formed, so that it can be brought into abutment against and in engagement with the first and second abutment faces79aand79bof the first cam79, when the turned position of the selecting lever76is the fifth/sixth-speed selecting position.

A solenoid84is mounted to the casing78and has an axis which is substantially parallel to the first abutment face79aof the first cam79, when the turned position of the selecting lever76is the fifth/sixth-speed selecting position. The solenoid84includes a rod83which is adapted to protrude into a protruding position in an energized state of the solenoid84and to retreat in a non-energized state of the solenoid84. A tip end of the rod83is adapted to abut against the second cam80. Moreover, a torsion spring82is mounted between the casing78and the second cam80, and exhibits a spring force in a direction to push the second cam80against the tip end of the rod83.

The solenoid84is brought into the energized state, when a vehicle speed exceeds, for example, 15 km/hr. In this state, the second cam80is turned against the spring force of the torsion spring82to a position in which the second cam80can be engaged with the first cam79, by the rod83lying in the protruding position. When the turned position of the selecting lever76is the fifth/sixth-speed selecting position, the second cam80is engaged with the first and second abutment faces79aand79bof the first cam79, thereby inhibiting the turning of the selecting lever76from the fifth/sixth-speed selecting position to the reverse position. In other words, in a state in which the vehicle speed exceeds, for example, 15 km/hr, the reverse position cannot be selected.

In this case, the solenoid84is positioned so that its operating axis is substantially perpendicular to a direction of a force which is applied from the first cam79to the second cam80upon the turning of the selecting lever76from the fifth/sixth-speed selecting position to the reverse position. Therefore, the force by turning of the selecting lever76from the fifth/sixth-speed selecting position to the reverse position cannot be applied to the solenoid84. The solenoid84may be formed to exhibit a relatively small electromagnetic force.

In the case where the selecting lever76lying in the fifth/sixth-speed selecting position is turned to the third/fourth-speed selecting position when the vehicle speed exceeds, for example, 15 km/hr, the second cam80can be turned in a clockwise direction as viewed inFIG. 3, while the first cam79is pushing the rod83of the solenoid84, that is, the turning of the selecting lever76from the fifth/sixth-speed selecting position toward the third/fourth-speed selecting position is permitted.

On the other hand, when the vehicle speed is a low speed, for example, equal to or lower than 15 km/hr, as well as when an ignition switch for the engine E is closed, the rod83is retracted by bringing the solenoid84into the non-energized state, and the second cam80is also turned, following the displacement of the rod83, to a position in which it is not engaged with the first cam79(a position shown in a dashed line in FIG.3). Therefore, when the turned position of the selecting lever76is the fifth/sixth-speed selecting position, the second cam80cannot be engaged with the first cam79, that is, the turning of the selecting lever76from the fifth/sixth-speed selecting position to the reverse position is permitted.

A shifting lever85is fixed to the shift-selecting shaft73below the selecting lever76and adapted to be turned together with the shift-selecting shaft74in response to the operation of the change lever L in the shifting direction SH. When the change lever L is in the first/second-speed selecting position P1, the third/fourth-speed selecting position P2, the fifth/sixth-speed selecting position P3or the reverse selection position P4, the shift-selecting shaft73is in the neutral position. The shift-selecting shaft73is turned in a counterclockwise direction as viewed inFIG. 4from the neutral position in response to the operation of the change lever L to the first-speed position D1, the third-speed position D3or the fifth-speed position D5, and turned in a clockwise direction as viewed inFIG. 4from the neutral position in response to the operation of the change lever L to the second-speed position D2, the fourth-speed position D4, the sixth-speed position or the reverse position R.

Referring also toFIGS. 5 and 6, an interlock plate86is mounted to the shift-selecting shaft73. The interlock plate86includes a pair of upper and lower side plate portions86aand86bdisposed at locations spaced apart from each other in an axial direction of the shift-selecting shaft73to extend through the shift-selecting shaft73. A pair of locking claws86cand86dleading to the side plate portions86aand86b, respectively. A slit87is defined between the locking claws86cand86dto extend along a plane perpendicular to the axis of the shift-selecting shaft73.

A guide groove88is provided in the interlock plate86to extend along the axis of the shift-selecting shaft73, and a detent pin89is fixed to the left case half13of the transmission case11and fitted into the guide groove88. Therefore, the movement of the interlock plate86in a direction along the axis of the shift-selecting shaft73is permitted, but the turning of the interlock plate86about the axis of the shift-selecting shaft73is inhibited.

A shifting arm90and an interlock arm91which is a first interlocking member are interposed between the side plate portions86aand86bof the interlock plate86in such a manner that a portion of each of the arms is covered with the interlock plate86. The shift-selecting shaft73extends through the shifting arm90and the interlock arm91. The shifting arm90is fixed to the shift-selecting shaft73by a bolt92, and the interlock arm91is operatively connected to the shifting arm90.

Provided between the shifting arm90and the interlock plate86is a detent mechanism99comprising a bottomed cylindrical retaining tube93mounted to the interlock plate86and having an axis perpendicular to the axis of the shift-selecting shaft73, a ball94retained in the retaining tube93for movement in a direction along an axis of the retaining tube93, a spring95mounted under compression between the retaining tube93and the ball94to exhibit a spring force for biasing the ball94toward the shifting arm90, and recesses96,97and98provided at three points spaced at equal distances apart from each other in a circumferential direction of the shifting arm90, so that they can accommodate a portion of the ball94.

The shifting arm90and the shift-selecting shaft73can be stopped with moderation by the detent mechanism99at three positions: any of the first-speed position, the third-speed position and the fifth-speed position; the neutral portion; and any of the second-speed position, the fourth-speed position, the sixth-speed position and the reverse position.

The shifting arm90has a drive portion90aintegrally provided thereon. The drive portion90ais disposed in the slit87defined between the locking claws86cand86dof the interlock plate86.

A first/second-speed shifting piece101, a third/fourth-speed shifting piece102, a fifth/sixth-speed shifting piece103and a reverse shifting piece104are arranged in the direction along the axis of the shift-selecting shaft73. Tip ends of the shifting pieces101to104are formed into a substantially U-shape so that notches101a,102a,103aand104aare defined therein, respectively. These tip ends are disposed to sandwich the locking claws86cand86dof the interlock plate86from opposite sides, so that the drive portion90aof the shifting arm90can be alternatively engaged into any of the notches101ato104a.

Referring carefully particularly toFIG. 3, a retainer124is in abutment against an upper surface of the interlock plate86, more specifically, an upper surface of the side plate86a, and a spring125is interposed between the retainer124and the cover member71. The shift-selecting shaft73is provided with an annular step73afacing the interlock plate86, and a spring127is interposed between a spring-receiving plate126received on the step73aand the retainer124. Thus, in a state in which the shifting lever85is in the neutral position and no operating force is applied to the selecting lever76, the selecting lever76is biased toward the third/fourth-speed position, and the change lever L is retained in the third/fourth-speed selecting position P2, by spring forces exhibited by the two springs125and127acting on the shift-selecting shaft73.

Referring also toFIG. 7, the interlock arm91is sandwiched between the shifting arm90and the side plate86aof the interlock plate86, and has a cylindrical portion91awhich is integrally provided thereon so that its tip end is sliding contact with the shifting arm90, and through which the shift-selecting shaft73extends. First and second projections105and106are provided in the interlock arm91at locations spaced apart from each other in a circumferential direction of the shift-selecting shaft73outside the cylindrical portion91a, and protrude toward the shifting arm90. A projection107is provided in the shifting arm90at a location corresponding to between the projections105and106to protrude toward the interlock arm91.

A torsion spring108is mounted between the shifting arm90and the interlock arm91to surround the cylindrical portion91aof the interlock arm91, and exhibits a spring force for biasing the shifting arm90and the interlock arm91in a direction to bring the projection107of the shifting arm90into engagement with the projection105of the interlock arm91. Thus, when the shifting arm90is turned from the neutral position to any of the second-speed position, the fourth-speed position, the sixth-speed position and the reverse position as well as from any of the first-speed position, the third-speed position and the fifth-speed position to the neutral position, the interlock arm91is turned in operative association with the shifting arm90by pushing of the projection105pushed by the projection107. When the shifting arm90is turned from any of the second-speed position, the fourth-speed position, the sixth-speed position and the reverse position to the neutral position as well as from the neutral portion to any of the first-speed position, the third-speed position and the fifth-speed position, the interlock arm91is turned in operative association with the shifting arm90by the spring force of the torsion spring108.

The first/second-speed shifting piece101is fixed to a first/second-speed shifting rod (not shown) which is supported in the transmission case11for movement in a direction parallel to the axis of the counter shaft SC and which includes the first/second-speed shifting fork50. The third/fourth-speed shifting piece102is fixed to a third/fourth-speed shifting rod110which is supported in the transmission case11for movement in a direction parallel to the axis of the main shaft SM and which includes the third/fourth-speed shifting fork52. The fifth/sixth-speed shifting piece103is fixed to a fifth/sixth-speed shifting rod111which is supported on the transmission case11for movement in the direction parallel to the axis of the main shaft SM and which includes the fifth/sixth-speed shifting fork54.

The reverse shift piece104is fixed to a reverse shifting rod112supported in the transmission case11for movement in a direction parallel to the axis of the reverse idling shaft SR. On the other hand, the reverse shifting fork55is turnably carried on a support plate113fixed to the right case half12of the transmission case11through a shaft114parallel to the shift-selecting shaft73. A drive arm115integrally formed on the reverse shifting piece104is engaged with the reverse shifting fork55in such a manner that it turns the reverse shifting fork55in response to the operation of the reverse shifting piece104together with the reverse shifting rod112.

The interlock arm91functions in the following manner: When the interlock arm91is turned for shifting in operative association with the turning of the shifting arm90caused with the operation for shifting to the reverse position, it drives the a preselected forward speed stage shifting piece, e.g., the third/fourth-speed shifting piece102by a predetermined amount at a initial stage of such shifting turning, and returns the third/fourth-speed shifting piece102to its original position at a final stage of the shifting turning. In this manner, the reverse speed stage is established, while preventing the generation of a gear chattering, by temporarily braking the main shaft SM.

The interlock arm91is integrally provided with first and second drive arm portions116and117overhanging outwards at locations spaced apart from each other in the circumferential direction of the shift-selecting shaft73. The third/fourth-speed shifting piece102is integrally provided with a first engagement arm portion118capable of being brought into engagement with the first drive arm portion116, and a second engagement arm portion119capable of being-brought into engagement with the second drive arm portion117, and the notch102ais sandwiched between the first and second engagement arm portions118and119.

The first drive arm portion116is formed so that it can be brought into engagement with the first engagement arm portion119from the side of the notch102awith the selecting movements of the shifting arm90and the interlock arm91in response to the operation of the change lever L lying in the neutral position to the reverse selecting position P4. The second drive arm portion117is formed so that it can be brought into engagement with the second engagement arm portion119from the side of the notch102awith the shifting of the shifting arm90and the interlock arm91in response to the operation of the change lever L to the reverse position R in the reverse selecting position P4.

When the change lever L is brought into the reverse selecting position P4, the first drive arm portion116is brought into engagement with the first engagement arm portion118, as shown in FIG.8A. At this time, the drive portion90aof the shifting arm90is in a position corresponding to the reverse shifting piece104, as shown in FIG.8B.

When the change lever L is operated for shifting to the reverse position R in the reverse selecting position P4, the first engagement portion118is pushed at an initial stage of such shifting operation by the first drive arm portion116with the turning of the interlock arm91, as shown inFIG. 9A, whereby the third/fourth-speed shifting piece102is pushed by a predetermined amount toward the fourth-speed position, as shown in FIG.9B. In order to ensure the movement of the third/fourth-speed shifting piece102toward the fourth-speed position in this case, the interlock plate86is provided with a recess120which accommodates a portion of the third/fourth-speed shifting piece102driven by the predetermined amount.

When the shifting operation of the change lever L further progresses, the engagement of the first drive arm portion116with the first engagement arm portion118is released, as shown inFIG. 10A, and the application of an urging force from the first drive arm portion116to the third/fourth-speed shifting piece102is released. On the other hand, the second drive arm portion117is brought into engagement with the second engagement arm portion119from the side of the notch102a, and the second engagement arm portion119is pushed by the second drive arm portion117with the shifting of the interlock arm91toward the reverse position. This causes the third/fourth-speed shifting piece102to be returned from the fourth-speed position to the neutral position, as shown in FIG.10B.

At a final stage of the shifting operation of the change lever L toward the reverse position R, the second engagement arm portion119is further pushed by the second drive arm portion117, as shown inFIG. 11A, and the third/fourth-speed shifting piece102is returned to the neutral position, as shown in FIG.11B.

When the change lever L is further operated for shifting from the reverse position R toward the neutral position, the first drive arm portion116is put into abutment against the first engagement arm portion118from outside, as shown inFIG. 12A, whereby the turning of the interlock arm91is inhibited. Therefore, the shifting arm90is turned with the interlock arm91left as it is, while compressing the torsion spring108, so that the drive portion90aof the shifting arm90is returned to the neutral position, as shown in FIG.12B.

When the change lever L is then returned from the reverse selecting position P4to the third/fourth-speed selecting position P2, the abutment of the first drive arm portion116against the first engagement arm portion118is released, whereby the interlock arm91is turned until the projection105is put into abutment against the projection107by the spring force of the torsion spring108. In this manner, the interlock arm91is returned to a state before the start of the reverse shifting operation.

After the main shaft SM is once braked as described above to establish the reverse speed stage, there starts the simultaneous meshing of the reverse idling gear46slidable in a direction parallel to the main shaft SM and the counter shaft SC with the counter reverse gear48provided on the sleeve49of the first/second-speed synchronizing mechanism S and the main reverse gear47secured to the main shaft SM. However, if the sleeve49is moved with the sliding meshing of the reverse idling gear46with the counter reverse gear48, it is difficult for the main shaft SM to be rotated by the function of the first/second-speed synchronizing mechanism S1, and a thrust load provided upon the meshing of the reverse idling gear46with the main reverse gear47is increased.

Therefore, a restricting face121is formed at an end of the interlock plate86opposite from an operational direction123of the interlock plate86with the selecting operation of the change lever L toward the reverse position R, as shown in FIG.14. The restricting face121is formed in such a manner that among side faces of the interlock plate86facing the second-speed position, the fourth-speed position, the sixth-speed position and the reverse position, one side at the end opposite from the operational direction123protrudes by a protrusion amount d from the remaining side faces. When the drive portion90aof the shifting arm90is in one of positions corresponding to the shifting pieces101,102and103other than the reverse shifting piece104, as shown inFIG. 14A, the restricting face121is not opposed to any of the shifting pieces101to104. However, when the shifting arm90is driven for selection to a position where the drive portion90ais opposed to the reverse shifting arm104, as shown inFIG. 14B, the restricting face121is opposed with a very small gap to one of side faces of the notch101ain the first/second-speed shifting piece101, which is on the side of the second-speed position.

Therefore, even if a force toward the counter first-speed gear40is applied to the sleeve49provided with the counter reverse gear48in response to the sliding meshing of the reverse idling gear46with the counter reverse gear48caused with the shifting operation of the shifting arm90toward the reverse position, the movement of the sleeve49retained by the first/second-speed shifting fork50toward the counter first-speed gear40is inhibited, because the movement of the first/second-speed shifting fork50operatively connected to the first/second-speed shifting piece101by the abutment of the first/second-speed shifting piece101against the restricting face121.

In the manual transmission having six forward speed stages, the shifting arm90and the interlock arm91operatively connected to the shifting arm90are interposed between the side plate portions86aand86bof the interlock plate86, as described above, but in a manual transmission having an even number of, e.g., five forward stages, a shifting arm90and a reverse locking cam member128as a second interlock member having a shape different from that of the interlock arm91and operatively connected to the shifting arm90are interposed between the side plate portions86aand86bof the interlock plate86, as shown in FIG.15.

The reverse locking cam member128is adapted to prevent the mis-operation by inhibiting the turning of the shifting arm90from a fifth-speed position which is a forward highest-speed position to the reverse position. The reverse locking cam member128is operatively connected to the shifting arm90in an operative-connection structure similar to the operative-connection structure between the shifting arm90and the interlock arm91in the manual transmission having six forward six speed stages.

The interlock91and the reverse locking cam member128having different shapes are prepared in advance, and any of a combination of the shifting arm90and the interlock arm91and a combination of the shifting arm90and the reverse locking cam member128can be alternatively selected whether the manual transmission is of the six forward speed stages or of the five forward speed stages.

The operation of the present embodiment will be described below. In the case of the manual transmission having the six forward speed stages, the shifting arm90and the interlock arm91operatively connected to the shifting arm90are interposed between the pair of side plate portions86aand86bof the interlock plate86mounted to the shift-selecting shaft73. In the case of the manual transmission having the five forward speed stages, the shifting arm90and the reverse locking cam member128operatively connected to the shifting arm90are interposed between the side plate portions86aand86b.

Therefore, a reduction in cost can be achieved by having the shifting arm for common use in the changing systems of a plurality of manual transmissions having different numbers of forward speed stages. Moreover, either one of the interlock arm91and the reverse locking cam member128each having a shape depending on the number of the forward speed stages is selected depending on the number of the forward speed stages and operatively connected to the shifting arm90. Therefore, it is possible to prevent an increase in weight due to an unnecessary portion remaining in the shifting arm90, since a function required for the shifting arm90is performed by any of the interlock arm91and the reverse locking cam member128in such a manner that it is selected depending on the number of the forward speed stages.

The interlock arm91used in the manual transmission having the six forward speed stages is operated to establish the reverse speed stage, and the reverse locking cam member128used in the manual transmission having the five forward speed stages functions to prevent the turning of the shifting arm90from the neutral position to the reverse position. Either the interlock arm91or the reverse locking cam member128is alternatively selected depending on whether the number of the forward speed stages is an even number or an odd number. Therefore, a satisfactory function can be exhibited in each of the changing systems in appropriate correspondence to the number of the forward speed stages.

In addition, the interlock arm91functions to drive, by a predetermined amount, the third/fourth-speed shifting piece102at a preselected forward speed stage at an initial stage of the shifting operation to the reverse position, and to return the third/fourth-speed shifting piece102to the original position at a final stage of the shifting operation. When the shifting arm90is driven for shifting toward the reverse position, the main shaft SM is braked, as when the third/fourth-speed shifting piece102establishes the third speed stage, and the braking of the main shaft SM is released at the final stage of the shifting operation.

Therefore, an exclusive mechanism for the reverse speed stage is not required, and the main shaft SM can be braked temporarily during establishment of the reverse speed stage to prevent the generation of a gear chattering. Additionally, it is possible to provide the compactness of the manual transmission in the direction along the axis of the main shaft SM and to provide a reduction in weight of the manual transmission by a value corresponding to that the exclusive mechanism is not required.

Moreover, the recess120is provided in the interlock plate86for accommodation of a portion of the third/fourth-speed shifting piece102driven by the predetermined amount at the initial stage of the shifting operation and hence, the braking of the main shaft SM can be achieved reliably by ensuring that the third/fourth-speed shifting piece102is driven reliably by the predetermined amount during the establishment of the reverse speed stage.

Further, the interlock plate86is formed into a shape such that when the shifting arm90having the drive portion90aengaged with the reverse shifting piece104is turned for shifting to establish the reverse speed stage, the movement of the first/second-speed shifting piece101in the same direction as a direction of sliding movement of the reverse idling gear46is inhibited. Therefore, the movement of the first/second-speed shifting piece101in the same direction as a direction of sliding movement of the reverse idling gear46is inhibited by the interlock plate68, when the shifting arm90is turned for shifting toward the reverse position in order to establish the reverse speed stage. Thus, even if a force for moving the sleeve49of the first/second speed synchronizing mechanism S1is applied to the sleeve49when the reverse idling gear46is brought into sliding engagement with the counter reverse gear48, the sleeve49cannot be moved, because the movement of the first/second-speed shifting piece101operatively connected to the first/second-speed shifting fork50retaining the sleeve49is inhibited. As a result, in the starting of the simultaneous engagement of the reverse idling gear46with the counter reverse gear48and the main reverse gear47after the main shaft SM is once braked, the synchronizing effect of the first/second-speed synchronizing mechanism S1ensures that such a phenomenon deteriorating the rotation of the main shaft SM cannot occur, and a thrust load provided upon the meshing of the reverse idling gear46with the main reverse gear47cannot be increased, so that the reverse shifting load can be reduced.

Although the embodiment of the present invention has been described in detail, it will be understood that the present invention is not limited to the above-described embodiment, and various modifications in design may be made without departing from the spirit and scope of the invention defined in the claims.