Transmission and shift control system

The present invention is capable of suppressing gear shift shocks or delays in acceleration with no interruption of driving force and reducing the weight. Disclosed is a transmission which is provided, with multiple stage shift gears so arranged to shift a number of dog clutches to shift a gear to the upper stage of the multiple stage shift gears, and is characterized in that a guide part is provided to a shift operation section and the dog clutches on each of the sages so as to move the lower dog clutch in a neutral direction by a coasting torque acting on the lower stage by a shift rotation of the upper stage to release a meshing engagement when meshing engagements of the lower and upper dog clutches are simultaneously performed by an operation of the shift operation section.

TECHNICAL FIELD

The present invention relates to a transmission and a shift control system that shifts gears of an automobile, a construction machinery, an agriculture vehicle, or the like.

BACKGROUND TECHNOLOGY

Generally, a transmission for a vehicle employing a single clutch inevitably involves gear shift shocks, delays in acceleration, and the like due to interruption of driving force when shifting gears. In a construction machinery an agriculture vehicle, or the like with large running resistance and small speed energy, it becomes stopped as soon as driving force is interrupted when shifting gears and may be hard to shift the gears.

To this, it is known that a twin-clutch transmission involves no interruption of driving force to prevent gear shift shocks or delays in acceleration.

However, there is a problem that the twin-clutch transmission is complicated in structure and heavy in weight.

In contrast, a seamless-shift transmission draws attention as one capable of reducing weight.

FIG. 29is an operationally explanatory view of a seamless-shift transmission. InFIG. 29, for ease of explanation, a shift between a first speed and a second speed will be explained.

The seamless-shift transmission has three first burettes305and three second burettes307that engage with an input shaft between a first speed gear301and a second, speed gear303and move according to shift operation. On the first and second speed gears301and302, meshing teeth301aand303aare formed, and at both ends of the first and second burettes305and305, complicated different faces are formed in front and rear in a rotational direction.

The first and second burettes305and307are configured to move toward the first speed gear301or second speed gear303through a spring concerning an operation of a selecting fork.

With such a structure, for example, when shifting into the first speed gear301, the three first burettes305engage with the meshing teeth301aof the first speed gear301, and thereafter, the remaining three second burettes307engage with the meshing teeth301a.

When shifting into the second speed gear, the three second burettes307engage with the meshing teeth303aof the second speed gear303, and thereafter, the remaining three first burettes305engage with the meshing teeth303a.

With the first burettes305and second burettes307having such complicated faces arid the selecting operation through the spring, it involves no interruption of driving force to prevent gear shift shocks or delays in acceleration and can reduce the weight.

However, there is a problem that the structure having the first burettes305, the second burettes307and the like is complicated and increases in number of parts.

PRIOR ART DOCUMENT

DISCLOSURE OF INVENTION

A problem to be solved by the invention is a complicated structure even if it involves no interruption of driving force to prevent gear shift shocks or delays in acceleration and reduces the weight.

A transmission according to the present invention is capable of involving no interruption of driving force to prevent gear shift shocks or delays in acceleration, reducing the weight, and simplifying the structure. The transmission comprises: multiple stage shift gears fixed to or relatively rotatably supported with driving force transmission shafts; a plurality of clutch rings each having meshing parts on both sides for meshing with the respective shift gears that take two speeds or more away from each other, so as to connect the respective shift gears to the driving force transmission shafts and perform a shifted output; a shift operation part that selectively operates the clutch rings; guide parts that are provided for respective stages of the shift gears between, the clutch rings and the driving force transmission shafts so that, when meshing engagements of the clutch rings of an upper stage and a lower stage are simultaneously performed through the operation of the shift operation part, axial forces oriented in opposite directions that are a meshing-engagement direction and a meshing-release direction are generated on the clutch rings of the upper stage and the lower stage.

A shift control system according to the present invention comprises: a start clutch that transmits and outputs a torque from an engine according to a fastening adjustment; a transmission that shifts gears through a shifting movement of a meshing clutch according to a vehicle speed to output the torque transmitted and output from the start clutch to drive wheels; a clutch actuator that performs the fastening adjustment of the start clutch; a shift actuator that causes the shifting movement of the meshing clutch; a torque detector that detects a transmitting torque toward the drive wheels; a clutch controller that controls the clutch actuator to perform the fastening adjustment so that a transmission torque of the start clutch is reduced during an interval just before and after shifting a gear while maintaining engine output transmitting torque detected by the torque detector at the time of shifting the gear and preventing an excessive shock torque due to the shifting.

The transmission according to the present invention, due to the above-identified means, involves no interruption of a driving force to prevent gear shift shocks or delays in acceleration, reduces the weight, and simplifies the structure.

The shift control system according to the present invention, due to the above-identified means, involves no interruption of a driving force to prevent gear shift shocks or delays in acceleration.

EMBODIMENT FOR CARRYING OUT THE INVENTION

The object capable of involving no interruption of a driving force to prevent gear shift shocks or delays in acceleration, reducing the weight, and simplifying the structure is accomplished by guide parts that, when meshing engagements of meshing clutches of an upper stage and a lower stage are simultaneously performed, move the meshing clutch of the lower stage toward a neutral direction by a coasting torque acting on the clutch of the lower stage, thereby releasing the meshing engagement thereof.

The guide parts are provided for respective stages between the clutch rings and the driving force transmission shafts so that, when the meshing engagements of the clutch rings of the upper stage and the lower stage are simultaneously performed through an operation of a shift operation part, axial forces oriented in opposite directions that are a meshing-engagement direction and a meshing-release direction are generated on the clutch rings of the upper stage and the lower stage.

FIG. 1is a schematic sectional view illustrating a transmission according to Embodiment 1 of the present invention as well as a front differential gear, andFIG. 2is an enlarged sectional view of a relevant part of the transmission.

As illustrated inFIGS. 1 and 2, a transmission1is provided with a main shaft3and a counter shaft5as driving force transmission shafts, and an idler shaft7. These main shaft3and counter shaft5are rotatably supported with a transmission case17through bearings9,11,13, and15, or the like. The idler shaft7is fixed on the transmission case17side.

A first speed gear19, a second speed gear21, a third speed gear23, a fourth speed gear25, a fifth speed gear27and a sixth speed gear29as multiple stage shift gears are fixed to or relatively rotatably supported with the main shaft3or the counter shaft5.

The first speed gear19and third speed gear23on the counter shaft5mesh with output gears31and33of the main shaft3, and the second speed gear21, fourth speed gear25, fifth speed gear27, and sixth speed gear29on the main shaft3mesh with input gears35,37,39, and41of the counter shaft5, respectively.

A reverse idler43on the idler shaft7is arranged to be able to mesh with an output gear44on the main shaft3or an input gear45on the counter shaft5through an axial movement.

The first speed gear19, the second speed gear21, the third speed gear23, the fourth speed gear25, the fifth speed gear27and the sixth speed gear29are able to be connected to the main shaft3or the counter shaft5by first to third meshing clutches47,49, and51to perform a shift output.

The first to third meshing clutches47,49, and51shift gears to upper stages of the multiple stage shift gears by shifting a number of the first to third meshing clutches47,49, and51.

Namely, the first speed gear19, the second speed gear21, the third speed gear23, the fourth speed gear25, the fifth speed gear27and the sixth speed gear29as the multiple stage shift gears are arranged to be shifted by shifting a number of the first to third meshing clutches47,49, and51.

For example, shifting from the first speed gear19into the second speed gear21is performed by shifting the first and second meshing clutches47and49.

The first to third meshing clutches47,49, and51has the same structure in essence and are provided with clutch cam rings53,55, and57, clutch rings59,61, and63, clutch teeth47a,47b,49a,49b,51a,51b,19a,21a,23a,25a,27a, and29aformed on respective opposing faces of the clutch rings59,61, and63and the first speed gear19to the sixth speed gear29.

Therefore, the clutch rings59,61, and63move in an axial direction of the main shaft3or the counter shaft5to make connection for the shift output by selective meshing engagements of the clutch teeth47a,47b,49a,49b,51a,51b,19a,21a,23a,25a,27a, and29a.

On the clutch cam rings53,55, and57of the first to third meshing clutches47,49, and51, v-shaped cam grooves85,87, and89are formed. The clutch cam ring53of the first meshing clutch47is connected to and is rotatable integrally with the counter shaft5. The clutch cam rings55and57of the second and third meshing clutches49and51are connected to and are rotatable integrally with the main shaft3.

The clutch rings59,61, and83of the first to third meshing clutches47,49, and51are arranged on and fitted to outer peripheries of the clutch cam rings53,55, and57, and are axially movable. On inner peripheries of the clutch rings59,61, and63, cam projections71,73, and75are formed to be fitted into and guided by the cam grooves65,67, and69.

On the clutch ring59and reverse idler43, circumferential recessed stripes81and83with which below-mentioned shift forks77and79engage are formed. On an outer periphery of the clutch ring59, the input gear45are formed. On the clutch rings61and63, circumferential protruding stripes89and91with which below-mentioned shift forks85and87engage are formed.

The first to third meshing clutches47,49, and51are selectively operated by a shift operation part93. The reverse idler43is also operated by the shift operation part93.

The shift operation part93is provided inside the transmission case17and has a plurality of shift forks77,79,85, and87, a plurality of shift rods103,105,107, and109, shift arms111,113,115, and117, and a shift drum119.

The shift forks77,79,85, and87are provided for the respective first to third meshing clutches47,49,51and reverse idler43and interlock with the meshing clutches47,49,51and reverse idler43,

The shift rods103,105,107and109support the respective shift forks77,79,85, and87.

The shift arms111,113,115, and117are connected to the respective shift rods103,105,107, and109.

The shift drum119is provided with shift grooves120,121,123, and125and projections at proximal ends of the shift arms111,113,115, and117engage with these shift grooves120,121,123, and125.

Between the shift forks85and87side and the transmission ease17side, concavo-convex parts127and129and check parts131and133are provided. Between the shift fork77side and the transmission case17side, a concavo-convex part and a check part that have the same structures are provided and are omitted from the drawings.

The concavo-convex parts127and129are formed on the shift forks85and87and have positioning recesses127a,127b,127c,129a,129b, and129c. The positioning recesses127aand129acorrespond to a neutral position and the positioning recesses127b,127c,129b, and129ccorrespond to coast meshing positions.

The check parts131and133are supported on the transmission case17side and push check balls131aand133athrough check springs131band133bso that the check balls131aand133aengage with the concavo-convex parts127and129by elastic force. With these engagements, the first to third meshing clutches47,49, and51can be positioned at the neutral position and the coast meshing positions.

An output of the transmission1is performed from a front differential gear137that engages with an output gear135of the counter shaft5.

Namely, when the shift drum119is driven and rotated by a shift motor (not illustrated) based on a manual operating signal of a shift lever or an accelerator position signal, vehicle speed signal, and the like due to an operation of an accelerator pedal, the shift rods103,105,107, and109are selectively driven in the axial direction through any of the shift arms111,113,115, and117according to a guidance of the shift grooves120,121,123, and125.

With the selectively driving of the shift rods103,105,107, and109, the first to third meshing clutches47,49,51and reverse idler43are selectively operated through any of the shift forks77,79,85, and87. Due to this selective operation, the first speed gear19to sixth speed gear29and reverse idler43selectively operates to shift up or down a gear, or change into reverse.

In the shift operation part93and the first to third meshing clutches47,49, and51, an internally-circulating torque is mechanically inescapably generated regardless of an output torque of the engine when meshing engagements of the clutches of an upper stage and a lower stage are doubly performed through the operation of the shift operation part93. Guide parts G are provided for respective stages and function to move the clutch of the upper stage in a further-meshing-engagement direction by a driving torque acting there on due to the internally-circulating torque and to move the clutch of the lower stage toward a neutral direction by a coasting torque acting thereon due to the internally-circulating torque to release the meshing engagement thereof.

The guide parts G provide the first to third meshing clutches47,49, and51with the cam grooves65,67, and69and the cam projections71,73, and75as mentioned above. Through the cam grooves65,67, and69and the cam projections71,73, and75, the driving torque and coasting torque are transmitted to the first speed gear19, second speed gear21, third speed gear23, forth speed gear25, fifth speed gear27, sixth speed gear29in the coast meshing positions of the first to third meshing clutches47,49, and51. Only in release-standby positions where the clutches shift away from the coast meshing positions toward meshing-release sides, the meshing engagements are guided toward the neutral directions due to the coasting torque.

The guide parts G provide the shift operation part93with a locomotive transmission mechanism M and provide the first to third meshing clutches47,49, and51with below-mentioned driving inclined faces F on only positive driving torque transmission side.

The driving inclined faces F generates locomotive according to the driving torque, to displace the clutch rings59,61, and63of the first to third meshing clutches47,49, and51to the release-standby positions. The inclined faces F may be formed on the clutch teeth on the gear side to provide the similar function.

FIGS. 3 and 4are development views illustrating the cam groove and the cam projection,FIGS. 5 and 6are perspective views illustrating the relationship between the clutch cam ring and the clutch ring.FIG. 7is a perspective view illustrating the clutch cam ring, andFIG. 8is a perspective view illustrating the clutch ring.

As illustrated inFIGS. 3-7, a plurality of the cam grooves65,67, and69are formed on outer peripheries of the clutch cam rings53,55, and57at regular intervals in a circumferential direction. The cam grooves65,67, and69has v-shaped parts65a,67a, and69aformed at axial central portions that include portions corresponding to the neutral positions and level portions65b,67b, and69bformed on both sides thereof.

Accordingly, in a case where the meshing clutches47,49, and51are in at non-release-standby positions, the cam projections71,73, and75are positioned at the level portions65b,67b, and69b, so that the meshing clutches keep the meshing engagements without generating thrust toward the neutral positions even if the coasting torque acts.

The cam projections71,73, and75radially protrude from the inner peripheries of the clutch rings59,61, and63at regular intervals in a circumferential direction so that the cam projections are inserted into and guided by the respective cam grooves65,67, and69.

Therefore, in the coast meshing positions of the first to third meshing clutches47,49, and51, the cam projections71,73, and75are positioned at the level portions65b,67b, and69b, thereby transmitting the driving torque or coasting torque to the first speed gear19, second speed gear21, third speed gear23, fourth speed, gear25, fifth speed gear27, and sixth speed gear29.

In the release-standby positions of the first to third meshing clutches47,49, and51, the cam projections71,73, and75are positioned at the v-shaped portions65a,67a, and69a, so that the meshing are guided toward the neutral direction due to the coasting torque as illustrated inFIG. 4.

FIGS. 9 and 10are schematic views illustrating the relationship among the shift fork, the check part, and the meshing clutch,FIG. 11is a development view illustrating the clutch ring, andFIG. 12illustrate a meshing engagement of a dog clutch in which (a) is a development view illustrating a coast meshing position and (b) is a development view illustrating a standby meshing position. InFIGS. 9-12, the third meshing clutch will be explained. Since the same applies to the first and second meshing clutches, duplicative explanation is omitted.

As illustrated inFIGS. 9-12, in the third meshing gear51, the clutch teeth51aand51bof the clutch ring63, and the clutch teeth25aand29aof the fourth speed gear25and the sixth speed gear29have tooth spaces in a circumferential arrangement that are larger than tooth thicknesses. A circumferentially-meshing face of each of the clutch teeth51a,51b,25a, and29ais inclined so that a root of a tooth is slightly narrowed.

At roots of the clutch teeth51aand51bof the clutch ring63, the driving inclined faces F are formed on meshing faces that receive the driving torque, respectively.

Therefore, if the third meshing clutch51performs a meshing engagement connection with and is connected to the sixth speed gear29and tire driving torque acts on the clutch, the clutch ring63is displaced due to the driving inclined faces F as illustrated inFIG. 12(b). At this time, the recess129bformed on the shift fork87pushes the ball133aback to apply a pressure on the spring133band store energy in the spring as illustrated inFIG. 10.

The displacement is allowed by a looseness provided between the four speed shift arm117and the shift groove125inFIG. 1. Due to this displacement, the clutch ring63becomes positioned at the release-standby position where the clutch ring is displaced away from the coast meshing position toward the meshing-release side. Next, if the driving torque turns into the coasting torque, the teeth are pushed toward an opposite side and put out of the faces F illustrated inFIG. 12. Accordingly, the meshing engagement becomes deeper by the action of the recess129band the ball133adue to the aforementioned energy of the spring133bas illustrated inFIG. 12(a).

In this state, since the cam projection75inFIG. 2is positioned at the level portion69bof the cam groove69, no thrust acting on the clutch ring63is generated.

On the other hand, when starting to shift a gear to the upper stage, the shift drum119inFIG. 13rotates to eliminate the aforementioned looseness with respect to the shift arm117according to a shape of the shift groove125of the lower stage, thereby maintaining the release-standby position. At this time, the projection75is shifted from the level portion69bto an inclined face of the cam groove69, the coasting torque is applied to the lower stage gear according to the meshing engagement of the upper stage gear, and a thrust component for a movement toward the neutral direction is obtained due to the inclined face of the cam groove69. Concrete shifting action will be explained later.

Where, only a shift-up operation into the fifth speed (upper stage) from the fourth speed (lower stage) will be explained, for ease of explanation. The same applies to shift-up operations into the other stages.

FIGS. 13-16illustrate operations at the time of shifting up a gear. Since the drive torque is applied to the clutch teeth25afor the fourth speed, the clutch ring63becomes in the release-standby position as illustrated inFIG. 14due to the function of the inclined faces F. Namely, the projections75of the clutch ring63in the fourth speed position are on the slanted faces of the cam grooves69. At this time, if the shift-up operation into the fifth speed is carried out by the rotation of the shift drum119, the shift groove123functions to operate the clutch ring61through the shift arm115, shift rod107, and shift fork85. With this operation, the clutch ring61engages with the fifth speed gear27so that the fourth speed gear25and the fifth speed gear27simultaneously perform the meshing engagements.

At this time, the coasting torque occurs on the fourth speed side and the driving torque occurs on the fifth speed side due to the internally-circulating torque that is mechanically inescapably generated by the simultaneous meshing engagement regardless of the output torque of the engine. Through the function of the inclined faces of the cam grooves69and67, these torque generates the thrust toward the neutral direction that is rightward in the drawings on the clutch ring63in the fourth speed position and the thrust toward the direction that is rightward in the drawings to deepen the meshing engagement on the clutch ring61in the fifth speed position. Due to this, the clutch rings63and61are shifted to given positions and the shift-up operation into the fifth speed is completed as illustrated inFIG. 15.

As an aspect of the transmission1, when the clutch rings59,61, and63axially move, the clutch ring on the lower stage rotates to be relatively delayed and the clutch ring on the upper stage rotates to be relatively antecedent with respect to the cam rings53,55, and57rotating integrally with the main shaft3or the counter shaft5under the function of the inclined faces of the cam grooves65,67, and69. This operation eliminates relative speed among the clutch teeth19a,21a,23a,25a,27a, and29aof the lower and upper gears that rotate at different speeds so that the doubly-meshing engagements are allowed, and generates a synchronization effect to absorb gear shift shocks.

If the shift-up operation is performed while engine braking occurs, the clutch ring63in the fourth speed position is shifted in a condition where the ring does not position at the release-standby position. At this time, the clutch ring61engages with the fifth speed gear27by the shift-up operation, so that a further coasting torque acts on the fourth speed, but the clutch ring63in the fourth speed position is not at the release-standby position so that the thrust component toward the neutral direction is not generated.

However, (1) an absolute value of the coasting torque at the time of the engine braking is smaller than that of the torque at the time of acceleration so that a frictionai force acting on the meshing clutch is small; and (2) a strong thrust component is generated on the clutch ring61in the fifth speed position by the function of the inclined face of the cam groove67. This thrust is transmitted through the shift fork85and shift rod107in the fifth speed position and the shift drum119to the shift rod109and shift fork87in the fourth speed position, to drive the clutch ring63in the forth speed position toward the neutral direction that is rightward in the drawings. Therefore, nothing hinders the shift-up operation in such a situation.

Even if the driving torque acts, the clutch ring63does not position at the release-standby position with absence of the inclined faces F. Even in this case, however, the clutch ring63is forcibly shifted toward the neutral direction due to the transmission of the force transmitted from the shift mechanism in the fifth speed position.

Accordingly, the inclined faces F are not fundamental to the present invention, and they are for smoothly shifting gears.

Further, the present embodiment performs the shift operation by the shift grooves120,121,123, and125of the shift drum119(cylindrical cam). Instead, the present invention is realised by a planer cam, driving each shift rod by controlled hydraulic pressure, an electric motor, or air pressure.

When reducing speed, there is no need for the seamless shift unlike at the time of the acceleration. This is because the reducing speed is mainly performed by brakes, the output from the engine has no relevance to the reducing speed basically, and there is no problem even if the driving torque from the engine or engine braking torque is interrupted. Accordingly, similar to a standard manual transmission, the clutch ring61in the fifth speed position of the upper stage is shifted into neutral illustrated inFIG. 16to interrupt the input, and then the clutch ring63meshes with the fourth speed gear27to shift down a gear.

From the above, it becomes the meshing engagement state inFIG. 13. In this way, the present embodiment has different modes of transitions for the meshing engagements in the shift-up operation and shift-down operation. This is based on that the shift rings61and63of the upper stage and lower stage are independent and linking shapes of the shift grooves125and123of the cylindrical cam119.

A mechanism for such different shift modes in the shift-up operation and shift-down operation will be explained with reference toFIG. 17.

In the fourth speed illustrated inFIG. 13, the shift, arm117and the shift arm115are at a position115aand a position117ainFIG. 17. If the shift drum119rotates frontward in the drawing to shift up a gear, the shift arm115moves from a position115b1through a position115b2to a position115caccording to an inclined face of the shift groove123. At this time, a double engagement is caused and the shift arm117automatically moves to a position117b2from a position117b1due to the function of the inclined face of the cam groove69of the cam ring57to be shifted into neutral. Further, the shift arm is shifted to a position117caccording to the rotation of the shift drum119. From the above, the shift-up operation from the fourth speed to the fifth speed is completed.

During the meshing engagement of the clutch in the fifth speed, the shift fork117is kept the neutral position by the check part133as illustrated inFIG. 1by the check mechanism illustrated, inFIG. 9. The shift drum119rotates, even if the shift groove125involves a looseness with respect to the shift arm117at the position117b2ofFIG. 17, so that the shift arm117is kept the neutral at the position117b2by the aforementioned check part133.

On the other hand, the shift arm115is shifted from the position115cto the position115b1so that both the clutches in the fourth speed and fifth speed become neutral as illustrated inFIG. 16.

If the shift drum119further rotates, the shift fork117is shifted from the position117b2to the position117a, the clutch ring63meshes with the clutch teeth25aof the fourth speed gear25, and the shift-down operation is completed as illustrated inFIG. 13.

The transmission may reverse orientations of inclined faces of cam grooves and positions of inclined faces F with respect to clutch, teeth under the aforementioned shifting principle so that the clutch ring on the lower stage side is guided toward the further-meshing-engagement direction and the clutch ring on the upper stage side is guided toward the neutral direction according to functions of the guide parts G when meshing engagements of the clutch rings of the upper stage and the lower stage are simultaneously performed.

This is because a shift-down operation is required to obtain more driving force when a construction machinery an agriculture vehicle, a heavy-duty truck or the like runs on mud or climbs a slope at a low speed, i.e., is under large running resistance and small speed energy. In such a situation, if a driving force is interrupted even for a short time when shifting down a gear in a standard meshing transmission, the vehicle becomes stopped to make it difficult to climb the slope or the like. The present invention can shift gears without interruption of the driving force, so that it is easy to shift down the gears to keep on running.

FIGS. 18-20illustrate modified examples in whichFIGS. 18 and 19are schematic sectional views illustrating a transmission as well as a front differential gear, andFIG. 20is a schematic sectional view illustrating a transmission.

InFIG. 18, a torsion bar3ais incorporated into a main shaft3. The main shaft3is provided with, in addition to the torsion bar3a, a hollow part3bincluding output gear31and33, and the like, and, an input part3cthat receives a driving input from an engine side.

The torsion bar3ais integrated, and coaxial with the input part3c. The torsion bar3ais relatively rotatably supported with the hollow part3bthrough bushings3dand3e.

Ends of the torsion bar3aand hollow part3bprotrude outward from a bearing9, and an inside of a cap3gthat is joined to the torsion bar3awith, a bolt3fengages with an outer periphery of the end of the hollow part3bthrough splines.

The remaining structure is the same as the aforementioned embodiment.

Therefore, if a torque from the engine is input to the main shaft3, it can be input to the hollow part3bon the output gears31,33, and the like side through the torsion bar3a.

As a result, an appropriate torque transmission toward the output gears31,33, and the like side can be performed even if exponential torque is input from the engine.

InFIG. 19, a torque converter141is attached to a main shaft3so that a torque from an engine can be input to the main shaft3through the torque converter141.

InFIG. 20, a counter shaft5is provided with, helical splines5aand5b, internal helical splines of respective input gears35,37,39, and41on the counter shaft5engage with the one helical spline5aand a first gear19engages with the other spline5b. On both sides of each of the input gears35,37,39,41, and first gear19, disc springs5care provided. Accordingly, the input gears35,37,33,41, and first gear19are axially pushed by the helical splines5aand5bso as to be positioned by the disc springs5cwhen the counter shaft5rotates.

Embodiment 2 accomplishes the object capable of involving no interruption of driving force to prevent gear shift shocks or delays in acceleration, reducing the weight, and simplifying the structure by shift operations through meshing clutches and a clutch control of a start clutch.

FIG. 21is a schematic view illustrating a shift control system.

As illustrated inFIG. 21, a shift control system201is provided with a start clutch203, a transmission205, a clutch actuator207, a shift actuator209, and a controller211as a torque detector and a clutch controller.

The start clutch203transmits and outputs a torque from an engine213by a fastening adjustment.

The transmission205shifts gears through shifting movements of dog clutches215and217as meshing clutches according to a vehicle speed to output the torque transmitted and output from the start clutch203to rear wheels225aand225bas drive wheels via a propeller shaft219, a final reduction gear221, and drive shafts223aand223b.

Where, the transmission205will be explained, as a forward four speed transmission and it will take no account of diameters of gears, for ease of explanation. The transmission205is provided with a first speed gear227, a second speed gear229, a third speed gear231, and a fourth speed gear233that mesh with counter gears237,239,241, and243of a counter shaft35.

When the dog clutch215meshes with the first speed gear227, a shift output for the output of the start clutch203is performed to the propeller shaft219through the fourth speed gear233, counter gear243, counter gear237, and first speed gear227.

When the dog clutch215meshes with the second speed gear229, a shift output for the output of the start clutch203is performed to the propeller shaft219through the fourth speed gear233, counter gear243, counter gear239, and second speed gear229.

When the dog clutch217meshes with the third speed gear231, a shift output for the output of the start clutch203is performed to the propeller shaft219through the fourth speed gear233, counter gear243, counter gear241, and third speed gear231.

When the dog clutch217meshes with the fourth speed gear231, the output of the start clutch203is directly output to the propeller shaft219.

The clutch actuator207performs a fastening adjustment of the start clutch203and uses a hydraulic actuator or the like. For example, an electric motor receives a signal from the controller211and is operated to drive a push rod of a master cylinder, thereby adjusting a fastening force of the start clutch203and controlling a transmission torque.

The shift actuator209causes the shift movements of the dog clutches215and217and is provided with a shift drum245, shift forks247and249, standby mechanisms251and253, and the like.

The shift drum245is provided with grooves245aand245bfor the shifting, and is configured to be driven and rotated by a shift motor (not illustrated) based on a manual operating signal of a shift lever, or an accelerator position signal, vehicle speed signal, and the like due to an operation of an accelerator pedal. The accelerator position is detected by an accelerator position sensor258and is input to the controller211.

The shift forks247and249are attached to shift rods257and259and the shift rods257and259engage with tire shift drum245through the standby mechanism251and253, respectively.

The controller211has a function as the torque detector that calculates a generated torque of the engine213according to the accelerator position and the number of rotation of the engine213to estimate a torque “A” that is transmitting by the start clutch toward, the rear wheels225aand225b. The number of rotation of the engine213is detected by a revolution sensor265and is input to the controller211.

A shift operation is detected from a shift member, the shift controller211, and the like, to perform the fastening adjustment so that a transmission capacity of the start clutch is reduced to “A” during an interval just before and after shifting a gear.

The controller211is configured to output signals for cutting off combustion, fuel, and the like to the engine213when reducing the transmission torque of the start clutch203. However, it may be configured not to output the signals for cutting off the combustion, fuel, and the like to the engine213when reducing the transmission torque of the start clutch203.

FIG. 22illustrate a relationship between a standby mechanism and a dog clutch in which (a) is a schematic view illustrating a standby state and (b) is a schematic view illustrating an after-operation state.

InFIG. 22, only the standby mechanism251on the dog clutch215side will be explained. The standby mechanism on the dog clutch217side is the same structure.

As illustrated inFIG. 22, the standby mechanism251is provided with a cylinder267, pistons269aand269b, a coil spring271. The cylinder267is integrally provided, with a shift arm261aand is movable in an axial direction of the shift rod257. In addition, in the standby mechanism253, a shift arm261bis used instead.

The pistons269aand269bare restricted in axially outward movements with respect to the cylinder267by snap rings207aand207band are restricted in axial movements exceeding a given amount with respect to the shift rod257.

The coil spring271is interposed between the pistons269aand269b.

A tip end side of the shift fork247engages with a clutch, ring273of the dog clutch215, and meshing teeth273a,273b,227a, and229aare formed on both faces of the clutch ring273and opposing faces of the first speed gear227and the second speed gear229.

Then, the shift arm261ais operated by a guidance of the groove245aaccording to the rotation of the shift drum245. Due to this, even if the cylinder267is axially driven toward the second speed gear229, a meshing engagement is held by a frictional force between the meshing teeth273aof the clutch ring273and the meshing teeth227aof the first speed gear227as long as the fastening force of the start clutch203is sufficient.

Accordingly, the spring271is compressed between the piston269athat moves together with the cylinder267through the snap ring270band the piston289bthat is positioned by the snap ring272a, and stores a pressing force. Keeping on storing the pressing force causes the dog clutch215to stand by the shifting movement.

When receiving a signal of a completion of the shift operation of the shift actuator, an output torque is cut for an instant in time by cutting off the combustion of the engine, fuel or the like.

As a result, the frictional force between the meshing teeth273aof the clutch ring273and the meshing teeth227aof the first speed gear227is reduced. The pressing force stored in the spring271exceeds the reduced frictional force, whereby the shift fork247instantly operates through the shift rod257.

Through this operation, the clutch ring273moves toward the second speed gear229, the meshing teeth273bmesh with the meshing teeth229aof the second speed gear229, and the second speed gear229performs the shift output.

At this time, the transmission torque of the start clutch203is reduced to at least “A” for maintaining a transmitting torque between the rear wheels225aand225bas drive wheels to shift the gear, thereby reducing a shock at the time of shifting the gear.

FIG. 23is a graph illustrating a change in a driving torque applied to the rear wheels225aand225bwhen a driving input torque is steeply interrupted, e.g., a meshing engagement of a shifting clutch transitions to neutral.

As illustrated, inFIG. 23, the driving torque on the rear wheels225aand225bdoes not instantly become zero as illustrated with, an arrow even if the meshing engagement of the meshing clutch is shifted into neutral so that the driving torque is interrupted, and it reduces with a temporal declination due to natural frequency. Generally, time until the torque becomes zero is about 0.1 to 0.2 second. The declination is determined according to an inertia mass of an upstream of the drive shafts223aand223b, the propeller shaft219, and the like and a rigidity of the drive shafts223aand223b, the propeller shaft219, and the like.

If the shift is instantly performed and time to stay into neutral is a very short time of about 0.02 second, the shift can be completed while the reduction of the driving torque on the rear wheels is small. The shift in a short time is easily realized by a combination of the meshing clutches with no synchronizing mechanism and the standby mechanisms.

FIG. 24is a graph illustrating a gear shift shock when forcibly shifting up into an upper stage gear without a disengagement of the star clutch. Once a driving force is interrupted and then a large shock torque is generated due to energy of motion according to a difference with respect to a rotation speed of the engine.FIG. 25is a graph illustrating a change in torque when shifting up into an upper stage gear with a standard shift operation. It shows an interruption of the driving force for a long time.

From the above, the large shock is generated if the shift operation is performed while keeping the engagement of the start clutch as illustrated inFIG. 24, the interruption of the driving force occurs for a long time if the standard shift operation is performed, with the disengagement of the clutch, and a driver feels strange particularly in an automated manual transmission that shifts gears regardless of a driver's intention.

FIG. 26is a graph illustrating a change in clutch transmission torque capacity and a torque transmission characteristics according to the shift control system of the present embodiment. The rapidly instantly shift operation hardly involves a reduction in torque and an appropriate control of the start clutch has a less interruption of the driving torque and a less gear shift shock. A hatched portion inFIG. 26is a shock torque absorbed by a sliding in the clutch.

As illustrated inFIG. 26, the present embodiment does not cut off the start clutch203at the time of shifting a gear, but reduces the transmission torque of the start clutch203to “A” during an interval just before and after shifting a gear according to the generated torque of the engine just before the shifting.

Through such a control of the transmission torque of the start clutch203, the transmission torque in the start clutch,203is reduced while maintaining the transmitting torque between the start clutch203and the rear wheels225aand225b, thereby realising the shift operation with the reduction of the gear shift shock and no interruption of acceleration.

If it reduces the transmission torque of the start clutch203and outputs signals for cutting off combustion, fuel, and the like to the engine213, the instant shift operation is further secured according to the reduction of the output torque of the engine213by the standby mechanisms that are pre-shifted.

As a dotted line inFIG. 21, between the start clutch203and the rear wheels225aand225b, on a downstream side of the transmission205in the present embodiment, a fly wheel275is attached as an inertial mass that urges an inertial rotation. Due to this, natural frequency of a driving force transmission system on the rear wheels225aand225bside is lowered, the declination in torque reduction illustrated inFIG. 23becomes smaller, and the transmission torque between the rear wheels225aand225bis surely maintained.

FIG. 27is a control flowchart according to the present embodiment.

The flowchart ofFIG. 27is carried out according to the engine start-up.

In Step S201, a process of “a manually or automatically shifting instruction” is carried out.

The manually shifting instruction causes the controller211to output a signal to the shift actuator209according to the instruction when, for example, shifting up or down a gear by operating a shift lever in a manual mode.

The shift actuator209rotates the shift drum245through the rotation of the electric motor, to arbitrarily operate the dog clutches215and217through the shift arms261and263, shift rods257and259, standby mechanisms251and253, and shift forks247and249so that the transmission205shifts a gear.

The automatically shifting instruction causes the controller211to calculate an appropriate shift stage based on the number of rotation of the engine, accelerator position, and vehicle speed and output a signal to the shift actuator209according to the calculation. With the output signal, the shift operation is performed in the same way as the above.

In this shift operation, when of, for example, shifting from the first speed gear227into the second speed gear229as mentioned above, the standby mechanism251stores and keeps the pressing force to cause the dog clutch215to stand by the shifting movement.

In Step S202, a process of “detecting a transmitting torque1toward the rear wheels” is carried out.

In Step S203, the clutch actuator reduces the fastening force of the start clutch according to the result in Step S202.

In Step S204, the torque of the meshing clutch is interrupted in an instant of time. Due to this, the frictional force of the meshing clutch is reduced, the clutch ring273is instantly moved toward the second speed gear229by the energy of the standby mechanism, and the meshing teeth273bengage with the meshing teeth229aof the second speed gear229to perform the shift operation by the second speed gear229.

In Step S205, a process of “fastening the clutch 100 percent again” is carried out to complete the shift operation.

Embodiment 2 of the present invention is provided with the start clutch203that transmits and outputs the torque from the engine213according to the fastening adjustment, the transmission5that shifts gears through the shifting movements of the dog clutches215and217according to the vehicle speed to output the torque transmitted and output from the start clutch203to the rear wheels225aand225b, the clutch actuator207that performs the fastening adjustment of the start clutch203, the shift actuator209that causes the shifting movement of the dog clutches215and217, the torque detector211that detects the transmitting torque toward the rear wheels225aand225b, the controller (clutch controller)211that controls the clutch actuator209to perform the fastening adjustment so that a transmission torque2of the start clutch203is reduced while maintaining the transmitting torque1detected by the controller (torque detector)211at the time of shifting the gear.

Accordingly, it can shift a gear while maintaining a torsional torque just before shifting the gear between shift driven gears and the rear wheels225aand225b, thereby involving no interruption of the driving force and preventing gear shift shocks and delays in acceleration.

Additionally, it can largely reduce the weight with respect to a twin-clutch transmission and simplify the structure with use of the dog clutches215and217.

The controller211calculates the transmitting torque1at the time of shifting the gear according to the accelerator position and the number of rotation of the engine213.

Accordingly, the transmission torque2of the start clutch203can be reduced while accurately maintaining the transmitting torque1at the time of shifting the gear.

The standby mechanisms251and253are interposed so as to maintain the pressing force due to the coil spring271till the transmission torque of the meshing clutch is reduced by cutting off the combustion or the like through the controller211, thereby causing the dog clutches215and217to stand by the shifting movement.

Accordingly, although it has the simple structure with the use of the dog clutches215and217, the shift, operation is instantly performed while maintaining the transmitting torque “A” at the time of shifting the gear.

The fly wheel275is provided between the start clutch203and the rear wheels225aand225bto urge the inertial rotation.

Accordingly, the natural frequency of the driving force transmission system on the rear wheels225aand225bside is lowered, the declination in torque reduction illustrated inFIG. 23becomes smaller, and the reduction in torque of the drive wheels can be minimized.

FIG. 28is a graph, illustrating a change in number of rotation of the engine. As explained with reference toFIGS. 21-27, it causes a clutch control to stand by in a given engagement condition before shifting a gear according to the accelerator position and the number of rotation of the engine213, and it measures a differentiated value of the number of rotation, of the engine at the time of shifting the gear. It controls so that the clutch engagement is weakened if the differentiated value is smaller than a target value and the clutch engagement is strengthened if the differentiated value is larger than the target value. The target value is a proper negative amount as illustrated in the drawing.

Therefore, it generates a most appropriate transmission torque to be able to smoothly shift gears.

In the shift control system according to Embodiment 2 of the present invention, the standby mechanisms251and253may be omitted. In this case, the shift rods257and259are directly attached to the shift forks247and249so that the shift arms261and263directly operate the shift rods257and259.

Even in this case, the instant shift can be performed by a solenoid or the like when the transmission torque2of the start clutch203is reduced.

The shift control system according to Embodiment 2 of the present invention can be realised by the transmission1of Embodiment 1 instead of the transmission205.