GB2385391A - Ratio change actuator with shift arms mounted on coaxial shift shafts - Google Patents

Abstract

A ratio change actuator comprises shift arms 51a-53a which connected to tubular coaxial shift shafts 51-53. Driven gears 46-48 are mounted on respected shift shaft 51-53 and are engaged with drive gears 41a-43a which are rotated by actuators, eg electrical stepping motors 41-43. The shift arms 51a-53a engage link members 56-58 which are connected to shift rods 36-38 that have mounted thereon shift forks 31-33. Each shift fork 31-33 engages a sleeve (22(1), fig 2) of a synchromesh clutch (SM12, SM34, SM35) so that gear ratios can be changed by the shift arms 51a-53a axially moving shift rods 31-38. An actuation regulating mechanism restricts the rotation of the shift shafts 51-53 so that all of the synchromesh clutches (SM12, SM34, SM35) cannot be operated simultaneously. The regulating mechanism may comprise a plurality of fixed disc members having recesses and slots in which are regulating balls and pins.

Description

238539 1

SPECIFICATION

TITLE OF THE INVENTION

RATIO-CHANGE MECHANISM FOR TRANSMISSION

FIELD OF THE INVENTION

The present invention relates to a ratio-change mechanism used for the ratio control of a power transmission, which is equipped with a plurality of speed ratios and through which the driving force of a prime mover is transmitted to drive wheels.

BACKGROUND OF THE INVENTION

As such a power transmission of prior art, for example,

there is a power transmission disclosed in Japanese Laid-Open Patent Publication No. 2000-65199, which power transmission incorporates five speed change ratios for forward drive. The FIRST FIFTH speed input gears are disposed on an input shaft, which is connected to the engine, and the FIRST FIFTH speed output gears, which mesh with the FIRST FIFTH speed input gears, respectively, are provided on an output shaft. These FIRST FIFTH speed input and output gears constitute the FIRST FIFTH speed gear trains, respectively (power transmission paths). Here, the FIRST and SECOND speed output gears are disposed rotatably over the output shaft, and between these gears, a synchromesh mechanism is provided on the output shaft. By the operation of the synchromesh mechanism, the FIRST and SECOND speed output gears are selectively connected to and disconnected from the output shaft so as to set the speed change ratio of the transmission to the FIRST speed

l *' ratio or to the SECOND speed ratio. In a similar arrangement, the THIRD and FOURTH input gears are disposed rotatably over the input shaft, and between these two gears, another synchromesh mechanism is provided on the input shaft. By the operation of this synchromesh mechanism, the THIRD and FOURTH input gears are selectively connected to and disconnected from the input shaft so as to set the speed ratio of the transmission to the THIRD speed ratio or to the FOURTH speed ratio. The operation of the synchromesh mechanisms themselves are controlled by hydraulic actuators, which are arranged to achieve automatic speed ratio control. Such a system that comprises a plurality of hydraulic actuators for achieving automatic speed ratio control is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2000-55184 as a power transmission. On the other hand, in the above mentioned power transmission disclosed in Japanese Laid-Open Patent Publication No. 2000- 65199, the FIFTH input gear is provided rotatably over the input shaft, and the connection and disconnection of the FIFTH input gear is executed through a hydraulically actuated speed-change clutch, which is provided on the input shaft on the side opposite to the engine. When the hydraulic pressure of the speed-change clutch is set to a maximum value, the speed- change clutch is engaged fully to set the speed ratio of the transmission to the FIFTH speed ratio.

In the above mentioned case where the synchromesh mechanisms are used for establishing the FIRST FOURTH speed ratios, it is known that there is a phenomenon called "torque loss", in which the transmission torque becomes zero or closer to zero during a time after the synchronization of a respective synchromesh

l mechanism until the complete meshing of a respective gear for a power transmission. Because of this phenomenon of torque loss, while the operation of the synchromesh mechanisms is being controlled through the hydraulic actuators as mentioned above, the driver may feel an uncontrolled movement of the vehicle. To eliminate such uncontrolled movements, in the above mentioned power transmission disclosed in Japanese Laid-Open Patent Publication No. 2000-65199, while the speed change ratio of the transmission is being switched among the FIRST FOURTH speeds through the synchromesh mechanisms, the hydraulically actuated speed-change clutch, which is used for setting the FIFTH speed ratio, is brought into engagement half way, so that this clutch can transmit the torque of the engine partially while it is sliding. As a result, this partial torque transmission through the clutch effectively prevents the above mentioned uncontrolled movement of the vehicle, which may otherwise felt by the driver during the speed ratio change through the synchromesh mechanisms because of the phenomenon of torque loss.

This prior-art power transmission requires the placement of the above mentioned hydraulically actuated speed-change clutch with a speed-change cylinder to control the operation of the speed-

change clutch, in addition to the synchromesh mechanisms and the hydraulic actuators for controlling the synchromesh mechanisms, over and along the input shaft, for the prevention of uncontrolled movements caused from the phenomenon of torque loss, which is inherent to the synchromesh mechanisms. As mentioned above, this prior-art design requires a hydraulic actuator for each of the synchromesh mechanisms, so the construction of the ratio-change

mechanism is complicated. Therefore, the ratio-change mechanism must be designed with a length in the axial direction of the input shaft long enough to allow the arrangement of these elements along the input shaft. This is an impediment to a further miniaturization for compactness of the ratio-change mechanism and of the power transmission. SUGARY OF THE INVENTION

To solve this problem, it is an object of the present invention to provide a ratio-change mechanism which can execute a speed ratio control only with a plurality of synchromesh mechanisms, while preventing an occurrence of torque loss phenomenon. For compactness, the ratio-change mechanism includes a simple mechanism for controlling the operation of these synchromesh mechanisms. A ratio-change mechanism according to the present invention is used for speed ratio change control in a power transmission that transmits the driving force of a prime mover (for example, the engine 2 described in the following embodiment) to drive wheels through the transmission having a plurality of speed ratios.

The transmission comprises an input member (for example, the input shaft 14 described in the following embodiment), which is connected to the prime mover, an output member (for example, the output shaft 15 described in the following embodiment), which is connected to the drive wheels, a plurality of power transmission gear trains (for example, the FIRST FIFTH speed gear trains GP1 GP5 described in the following embodiment), which provide a plurality of power transmission paths between the input member and the output

member, a plurality of mechanical clutches (for example, the first third synchromesh mechanisms SM12, SM35 and SM34 described in the following embodiment), which selectively set any of the power transmission gear trains for a power transmission to selectively establish the power transmission paths, and a clutch actuation mechanism (for example, the ratio-change actuator 30 described in the following embodiment), which selectively actuates these mechanical clutches. Furthermore, the clutch actuation mechanism comprises a plurality of shift fork members (for example, the firsts third shift forks 31, 32 and 33 described in the following embodiment), which are used to engage and.disengage the mechanical clutches, a shift transmission mechanism, which shifts each of the shift fork members independently in an engaging direction or in a disengaging direction, and a plurality of shift actuators (for example, the first third shift actuators 41 43 described in the following embodiment), which actuate the shift transmission mechanism. Moreover, the shift transmission mechanism comprises a plurality of cylindrical tubular members (for example, the first third shift drive shaft members 51 53 described in the following embodiment) and a plurality of link members (for example, the first third link members 56 58 described in the following embodiment). The tubular members are disposed coaxially over one another, with each tubular member being rotatable independently to be driven by a corresponding shift actuator. The link members connect each of the tubular members to a corresponding shift fork member, so as to shift the shift fork members in the engaging direction or in the disengaging direction in correspondence to the rotation of the tubular members.

In this ratio-change mechanism, the shift transmission

mechanism comprises a plurality of cylindrical tubular members which are disposed coaxially in a telescope-like construction, each member. being rotatable independently from the other members.

Each tubular member is rotated by a shift actuator, and this rotational movement is transmitted through a link member to a shift fork member, so that a corresponding mechanical clutch is engaged or disengaged by the movement of the shift fork member. This arrangement is advantageous for miniaturizing or making-compact the shift transmission mechanism,.which actuates a plurality of mechanical clutches. -..

Preferably, the ratio-change mechanism is provided with a plurality of shift plates (for example, the first third driven gear members 46 48 described in the following embodiment), each shift plate being connected to a corresponding tubular member, so that it rotates together with the respective tubular member.- The ratio change mecharnsm is also preferably provided with a plurality of regulate members (for example, the regulating balls 7173 and the regulating À pins 76 78 described in the following embodiment), each member being positioned between the shift plates. In this arrangement, each regulating member restricts the rotational range of a corresponding tubular member, which is rotated by a shift actuator. As a result, even though the ratio-change mechanism is designed small in size or compact, the mechanical clutches can be controlled securely not to engage simultaneously in plurality.

Further scope of applicability of the present invention will

become apparent from the detailed description given-hereinafter.

However, it should be understood that the detailed description and

specific examples, while indicating preferred embodiments of the

invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the

accompanying drawings which are given by way of illustration only and thus are not limitative of the present invention.

FIG. 1 is a sectional view of a power transmission which includes a ratiochange mechanism according to the present invention.

FIG. 2 is a diagram which describes schematically the construction of the power transmission shown in FIG. 1.

FIG. 3 is a partial sectional view showing part of a synchromesh mechanism that constitutes the ratio-change mechanism. FIGS. 4A 4D are sectional views which describe the operation of this synchromesh mechanism.

FIGS. 5 and 6 are flowcharts describing control steps for an upshift from the FIRST speed ratio to the SECOND speed ratio executed with the ratiochange mechanism.

FIG. 7 is a time diagram that describes chronological changes of the throttle opening, the gear torques, the engine rotational speed, and the sleeve positions that are observed during the upshift from the FIRST speed ratio to the SECOND speed ratio.

FIGS. 8 and 9 are flowcharts describing control steps for an upshift from the SECOND speed ratio to the THIRD speed ratio

executed with the ratio-change mechanism.

FIG. 10 is a time diagram that describes chronological changes of the throttle opening, the gear torques, the engine rotational speed, and the sleeve positions that are observed during the upshift from the SECOND speed ratio to the THIRD speed ratio.

FIGS. 11 and 12 are flowcharts describing control steps for an upshift from the THIRD speed ratio to the FOURTH speed ratio executed with the ratio-change mechanism.

FIG. 13 is a time diagram that describes chronological changes of the throttle opening, the gear torques, the engine rotational speed, and the sleeve positions that are observed during the upshift from the THIRD speed ratio to the FOURTH speed ratio.

FIG. 14 is a perspective view of a ratio-change actuator used for controlling the upshifts.

FIG. 15 is a view of the ratio-change actuator being mounted in the transmission housing.

FIG. 16 is a diagram which describes schematically the construction of the shift-transmission mechanism of the ratio-change actuator. FIGS. 17 and 18 are other perspective views of the ratio-

change actuator, which is used for controlling the upshifts.

FIG. 19 is a front view of the ratio-change actuator, which view describes the structure of the ratio-change actuator.

FIG. 20 is a side view of the ratio-change actuator.

FIG. 21 is a plan view of the ratio-change actuator.

FIG. 22 is a rear view of the ratio-change actuator.

FIG. 23 is a bottom view of the ratio-change actuator.

FIG. 24 is another plan view of the ratio-change actuator.

_ 8

FIG. 25 is a semi-sectional view of the ratio-change actuator. - FIGS. 26A and 26B are, respectively, a bottom view of a first driven gear member and a top view of a second driven gear member. FIGS. 27A and 27B are, respectively, a bottom view of the second driven gear member and a top view of a third driven gear member. JIGS. 28A and 28B are, respectively, a bottom view of the third driven gear member and a top view of a flange member used for rearward drive.

FIGS. 29A and 29B are, respectively, a top view and a bottom view of a regulating member.

FIGS. 30 35 are expanded sectional views of an actuation-regulating mechanism, which views are used for describing the operation of the actuation-regulating mechanism in controlling the upshift from the FIRST speed ratio to the SECOND speed ratio.

- FIGS. 36 41 are expanded sectional views of the actuation-regulating mechanism, which views are used for describing the operation of the actuation-regulating mechanism in controlling the upshift from the SECOND speed ratio to the THIRD speed ratio.

FIGS. 42 47 are expanded sectional views of the actuation-regulating mechanism, which views are used for describing the operation of the actuation-regulating mechanism in controlling the upshift from the THIRD speed ratio to the FOURTH speed ratio.

FIGS. 48 and 49 are expanded sectional views of the actuation-regulating mechanism, which views are used for describing the operation of the actuation-regulating mechanism in controlling

the shift from the NEUTRAL condition to the REVERSE speed ratio.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a preferred embodiment according to the present invention is described in reference to the drawings. FIG. 1 shows a power transmission according to the present invention, and FIG. 2 shows schematically a vehicle which incorporates this power transmission. The power transmission 1 transmits the driving force (torque) of the engine 2 as a prime mover, with a speed ratio control, to drive wheels W and W. The power transmission 1 comprises a ratio-change mechanism 4 and a starting clutch 5, which connects and disconnects the ratio-change mechanism 4 to and from the engine 2, and an electrical control unit (13 CU) 6, which controls the operation of the ratio-change mechanism 4, the clutch 5, etc. The starting clutch 5 comprises a friction disc 7, a pressure disc 8 and a diaphragm spring 9, which are positioned in this order between a flywheel 2b, which is connected to the crankshaft 2a of the engine 2, and the ratio-change mechanism 4. The friction disc 7 is fixed on an end of the input shaft 14 of the ratio-change mechanism 4.

While the central part of the diaphragm spring 9 are held by a clutch cover 10, the inner end of the diaphragm spring 9 is connected to a release bearing 11, which is slidable on the input shaft 14 of the ratio-

change mechanism 4. The outer end of the diaphragm spring 9 meets the pressure disc 8 and pushes it toward the friction disc 7. To the release bearing 11, connected is an end of a release fork 12 whose middle part is supported pivotally by a pivot 12a, and the other end thereof is connected to a starting actuator 13.

In this arrangement, while the starting actuator 13 is not

actuated, the friction disc 7 is sandwiched between the pressure disc 8 and the flywheel 2b by the biasing force of the diaphragm spring 9.

In this condition, the input shaft 14 of the ratio-change mechanism 4 is connected through the friction disc 7 and the flywheel 2b to the crankshaft 2a of the engine 2, so the starting clutch 5 is in a connected condition. On the other hand, while the starting actuator 13 is being actuated, the release fork 12 is swung around the pivot 12a counterclockwise. By this swing, the release bearing 11 pushes the diaphragm spring 9 to go through an elastic deformation that brings the diaphragm spring 9 away from the pressure disc 8. In this condition, the friction disc 7 is released free, so that the input shaft 14 of the ratio-change mechanism 4 is disconnected from the crankshaft 2a of the engine 2. As a result, the clutch is in a disconnected condition.

The starting actuator 13 is actuated hydraulically or electrically, and the operation of the starting actuator 13 is controlled through a hydraulic or electric actuation device 13a by the: ECU 6 with control signals. The starting actuator 13 is actuated only when the vehicle starts. Because of this actuation of the starting actuator 13, the clutch 5 is controlled to be connected, disconnected and again connected to the power source while the vehicle is being started.

Once the vehicle is started, the clutch 5 is kept in the connected condition (even while there is a speed ratio change).

The ratio-change mechanism 4 is an automatic ratio-

change mechanism that is controlled by the ECU 6 in correspondence to the position of the shift lever 6a, which is operated by the driver at the driver's seat. The ratio-change mechanism 4 comprises the above mentioned input shaft (main shaft) 14, an output shaft

(countershaft) 15, forward-drive FIRST FIFTH speed gear trains GP1 GP5 (hereinafter, when all the gear trains are referred, they are called "gear trains GP"), a REVERSE gear shaft 16, a REVERSE gear train GRT, etc. In these gear trains, the THIRD speed gear train comprises a pair of gear trains GP3(1) and GP3(2) having identical numbers of teeth. The input shaft 14, the output shaft 15 and the REVERSE gear shaft 16 are disposed in parallel with one another, and on those shafts, the FIRST speed gear train GP1, the REVERSE gear train GRT, the SECOND speed gear train, the THIRD (1) speed gear train GP3(1), the FIFTH speed gear train GP5, the THIRD (23 speed gear train GP3(2), and the FOURTH speed gear train GP4 are disposed in this order from the side of the engine as shown in the drawings.

The FIRST FIFTH speed gear trains GP1 GP5 (including the two THIRD speed gear trains GP3(1) and GP3(2)) comprise FIRST FIFTH speed input gears GI1 GI5 (including two THIRD speed input gears GI3(1) and GI3(2)), which are disposed on the input shaft 14, and FIRST FIFTH speed output gears GO1 G05 (including two THIRD speed output gears G03(1) and G03(2)), which are disposed on the output shaft 15 to mesh with the FIRST FIFTH speed input gears GI1 GI5, respectively. The gear ratios of these gear trains are lower for the gear trains used for the higher speed ratios.

The REVERSE gear train GRT comprises a REVERSE input gear GIR, which is provided as a one-piece body with the input shaft 14, a REVERSE middle gear GMR, which is provided rotatably on the REVERSE gear shaft 16, and a REVERSE output gear GOR, which is provided rotatably on the output shaft 15. The REVERSE

middle gear GMR is movable axially on the REVERSE gear shaft 16.

When the REVERSE middle gear GMR is at the position shown by real line in FIG. 1, it is set away from the REVERSE input gear GIR and the REVERSE output gear GOR, so that the REVERSE drive is set in disengagement. On the other hand, when the REVERSE middle gear GMR is at the position indicated by two-dot chain line in FIG. 1, it is set to mesh with the REVERSE input gear GIR and the REVERSE output gear GOR, so that the REVERSE drive is set in engagement. . The FIRST speed input gear GI1 of the FIRST speed gear train GP1 is provided as a one-piece body with the input shaft 14, and the FIRST speed output gear GO 1 is provided rotatably on the output shaft 15..A1SO7 the SECOND speed input gear GI2 of the SECOND speed gear train GP2 is provided as a one-piece body with the input shaft 14, and the SECOND speed output gear G02 is provided rotatably on the output shaft 15. Between these FIRST speed output gear GO 1 and the SECOND speed output gear G02, a FIRST/SECOND speed synchromesh mechanism SM12 (first synchromesh mechanism) is provided to switch the speed change ratio of the ratio-change mechanism selectively between the FIRST speed ratio and the SECOND speed ratio.

The FIRST/SECOND speed synchromesh mechanism SM12 has a conventional construction which is well-known in the art.

However, the construction and. operation of the synchromesh mechanism is described here in reference to FIGS. 3 and 4. As the construction of the FIRST/SECOND speed synchromesh mechanism SM12 is symmetrical toward the FIRST speed output gear GO1 and toward the SECOND speed output gear G02, the following

description is made mainly of the side of the synchromesh mechanism

facing the FIRST speed output gear GOT.

As shown in FIG. 3, the FIRST/SECOND speed synchromesh mechanism SM12 comprises a hub 21, a circular sleeve 22, a blocking ring 23 and a synchro-spring 24. The hub 21, which itself is connected to the output shaft 15 with splines, has a plurality of spline teeth 21a that extend axially on the outer surface thereof.

The sleeve 22, which also has a plurality of spline teeth 22a that extend axially on the inner surface thereof, meshes with the hub 21 and therefore is slidable axially with respect to the hub 21. The blocking ring 23 is accommodated in a circular recess 2 lb provided on an axial end of the hub 21, and the synchro-spring 24 is provided around the blocking ring 23.

Into the outer peripheral surface of the sleeve 22, a shift fork SF (corresponding to the first shift fork 31, which is described later) is fitted so that the sleeve 22 is shifted axially with respect to the hub 21 when the shift fork SF is driven by a ratio-change actuator connected thereto (this ratio-change actuator is described later). The axial end portions of some of the spline teeth 22a of the sleeve 22 protrude radially inward as projections 22b, whose bottoms are formed each with first and second slopes 22c and 22d that are continuous inwardly from the axial end thereof as shown in FIG. 3.

The blocking ring 23 comprises an outer ring 26 and an inner ring 27, which are arranged radially outward and inward, respectively, and a taper cone 28, which is positioned between the outer ring 26 and the inner ring 27. The outer and inner rings 26 and 27 are provided each with engaging keys 26a and 27a, and these keys engage with each other and prevent any relative rotation

between the outer ring 26 and the inner ring 27. The outer surface and inner surface of the taper cone 28 are tapered as tapered faces 28a and 28b, respectively, and these tapered faces are slidable on the inner surface of the outer ring 26 and the outer surface of the inner ring 27, respectively.

At the axial ends of the outer ring 26, a plurality of dog teeth 26b are provided extending radially outward (refer to FIG. 4), and at the part of the FIRST speed output gear GO 1 that faces these dog teeth 26b, also provided are a plurality of dog teeth 29a (refer to FIG. 4). The spline teeth 22a of the sleeve 22 are designed to mesh with these dog teeth 26b and 29a. As shown in FIG. 4, the ends of the spline teeth 22a are provided with chamfers 22e, and also, the ends of the dog teeth 26b of the outer ring 26 and the dog teeth 29a of the FIRST speed output gear GO1 are provided with chamfers 26c and 29b, respectively, which can meet with the chamfers 22e of the sleeve 22. Furthermore, the taper cone 28 is provided with a projection 28c that extends axially outward. This projection 28c is received loosely in a recess 29c provided in the FIRST speed output gear GO 1.

The synchro-spring 24 is held by a plurality of spring" supports (not shown) which are provided at a certain interval around the outer periphery of the outer ring 26. As shown in FIG. 3, when the sleeve 22 is at a neutral position, the synchro-spring 24 is surrounded by the dog teeth 26b of the outer ring 26, the axial end of the hub 21 and the axial end portions of the spline teeth 22a of the sleeve 22.

In this construction, when the sleeve 22 is at the neutral position shown in FIG. 3, the projections 22b of the spline teeth 22a of Is

the sleeve 22 are not in contact with the synchro-spring 24. In this condition, the resiliency of the synchro-spring 24 does not act on the outer ring 26, so the outer ring 26 and the inner ring 27 of the blocking ring 23 can rotate with respect to the taper cone 28. As a result, while the outer ring 26 and the inner ring 27 rotate together with the hub 21, the taper cone 28 rotates together with the FIRST speed output gear GO1 as a unit. Therefore, there is no balk motion between the sleeve 22, i.e., the output shaft 15, and the FIRST speed output gear GO1 (refer to FIG. 4A).

From this condition, if the sleeve 22 is slid to the FIRST speed output gear GO1 through the movement of the shift fork 25 actuated by the ratiochange actuator 30, the first slope 22c of the sleeve 22 pushes and moves, through the synchro-spring 24, the outer ring 26 of the blocking ring 23 to the FIRST speed output gear GOT.

In this instance, the chamfers 22e of the spline teeth 22a of the sleeve 22 push the chamfers 26c of the dog teeth 26b of the outer ring 26 (FIG. 4B). As a result, a large friction is generated between the outer ring 26 and inner ring 27 of the blocking ring 23 and the taper cone 28. The action of the chamfers 22e of the sleeve 22 that generates this friction is herein referred as "balk motion".

When this balk motion ceases, there is no rotational difference between the outer ring 26 and inner ring 27 and the taper cone 28, which are now rotating in synchronization. In this condition, there is little or no resistance in the blocking ring 23 against the movement of the sleeve 22, so the spline teeth 22a of the sleeve 22 fit into the gaps of the dog teeth 26b of the outer ring 26 (broken line in FIG. 4B). Then, the spline teeth 22a of the sleeve 22, after meeting with the chamfers 29b of the dog teeth 29a of the FIRST speed output

gear GO1 (FIG. 4C), meshes with the dog teeth 29a of the FIRST speed output gear GO1 (FIG. 4D). As a result, the FIRST speed output gear GO1 is connected completely to the output shaft 15, and the speed change ratio of the ratio-change mechanism 4 is set at the FIRST speed ratio. After the completion of the synchronization between the blocking ring 23 and the FIRST speed output gear GO1 until the meeting of the spline teeth 22a of the sleeve 22 with the chamfers 29b of the dog teeth 29a of the FIRST speed output gear GO1 (i.e., during the interval between the condition shown in FIG. 4B and that shown in FIG. 4C), the friction between the blocking ring 23 and the FIRST speed output gear GO1 is reduced or eliminated, and this condition can cause a phenomenon of torque loss, in which the torque transmitted to the output shaft 15 becomes zero or nearly zero.

On the other hand, if the sleeve 22 is slid to the SECOND speed output gear G02 (this case is not shown in the drawings), the spline teeth 22a of the sleeve 22 mesh with the dog teeth 29a of the SECOND speed output gear G02 after synchronization. As a result, the SECOND speed output gear G02is connected completely to the output shaft 15, and the speed change ratio of the ratio-change mechanism 4 is set at the SECOND speed ratio. If the sleeve 22 is at the neutral position, then the FIRST speed gear train GP1 and the SECOND speed gear train GP2 are both disconnected.

The ratio-change actuator mechanism (clutch actuation mechanism) that shifts the sleeve 22 is driven by an electrical motor, and the operation of the mechanism is controlled by the ECU 6. The construction and operation of this mechanism is described later.

During the balk motion while the spline teeth 22a of the sleeve 22 is pushing the dog teeth 26b of the blocking ring 23, by controlling this

pushing force, the torque transmitted from the input shaft 14 through the FIRST/SECOND speed synchromesh mechanism SM12 to the output shaft 15 can be controlled in magnitude. This pushing force is adjustable by the ratiochange actuator mechanism, which is controlled by the ECU 6. The construction and operation of the FIRST/SECOND speed synchromesh mechanism SM12 is also applicable to the other synchromesh mechanisms SM34 and SM35, which are described later in this section. In this document, if all these synchromesh mechanisms are referred together, then they are referred as "synchromesh mechanisms SM".

While the THIRD (1) and FIFTH speed input gears GI3(1) and GI5 of the THIRD (1) and FIFTH speed gear trains GP3(1) and GP5, which are positioned next in the order from the SECOND speed gear train GP2, are provided rotatably on the input shaft 14, the THIRD and FIFTH speed output gears G03(1) and G05 are connected to the output shaft 15 so as to rotate together as one body.

Between the THIRD (1) and FIFTH speed input gears GI3(1) and GI5, the THIRD/FIFTH speed synchromesh mechanism SM35 (second synchromesh mechanism), which has the same construction as the FIRST/SECOND speed synchromesh mechanism SM12, is positioned to connect selectively the THIRD (1) speed input gear GI3(1) or the FIFTH speed input gear GI5 to the input shaft 14 or disconnect them altogether. When the input shaft 14 is connected with the output shaft 15 through the THIRD (1) speed gear train GP3(1) or through the FIFTH speed gear train GP5, the speed change ratio of the ratio-

change mechanism 4 is set at the THIRD speed ratio or at the FIFTH speed ratio, respectively.

In the same way, while the THIRD (2) and FOURTH speed

input gears GI3(2) and GI4 of the THIRD (2) and FOURTH speed gear trains GP3(2) and GP4 are also provided rotatably on the input shaft 14, the THIRD (2) and FOURTH speed output gears G03(2) and G04 are connected to the output shaft 15 so as to rotate together as one body. Between the THIRD (2) and FOURTH speed input gears GI3(2) and GI4, the THIRD/FOURTH speed synchromesh mechanism SM34 (third synchromesh mechanism), which has the same construction as the above described synchromesh mechanisms, is positioned to connect selectively the THIRD (2) speed input gear GI3(2) or the FOURTH speed input gear GI4 to the input shaft 14 or disconnect them altogether. When the input shaft 14 is connected with the. output shaft 15 through the THIRD (2) speed gear train GP3(2) or through the FOURTH speed gear train GP4, the speed change ratio of the ratio-change mechanism 4 inset at the THIRD speed ratio or at the.FOURTH speed ratio, respectively.

A connection gear 18 is provided as a one-piece body with the output shaft 15, and this connection gear l8 always meshes with a gear 19a of a differential mechanism 19. Therefore, the driving force of the engine 2 with a speed ratio control provided through a speed change ratio of the ratio-change mechanism 4 is transmitted À from the output shaft 15 through the differential mechanism 19 to the drive wheels W and W. thus rotating these drive wheels W and W. In this embodiment, the ECU 6 is a ratio-change controller, and it is a microcomputer (not shown) that includes a RAM unit, a ROM unit, a CPU, and an I/O interface. The ECU 6 controls the operation of the ratio-change mechanism 4 and the clutch 5 by actuating the starting actuator 13 and the ratio-change actuator 30 in correspondence to the shift position of the shift lever 6a, which is

detected through a shift-position sensor 6b. In addition, the ECU 6 executes the throttle control of the engine 2 by actuating a throttle actuator 3 (torque control) in connection to the control of the ratio-

change mechanism 4.

Now, an upshift speed ratio control from the FIRST speed ratio to the SECOND speed ratio, which is accompanied by a torque-

replenishment management, executed by the ECU 6 is described in reference to the flowcharts of FIGS. 5 and 6 and to the time diagram of FIG. 7. The torque-replenishment management is to prevent torque loss so as to prevent a feeling of uncontrolled movement of the vehicle, which may otherwise occur during the engagement and disengagement of a synchromesh mechanism for an upshift of the ratio-change mechanism 4. These flowcharts of FIGS. 5 and 6 are actually one:flowchart, which is continuous through the circled "A"s in these charts.

While the ratio-change mechanism 4 is at the FIRST speed ratio, in which the FIRST speed gear train GP1 is engaged through the FIRST/SECOND speed synchromesh mechanism SM12, if the control flow receives a ratio-change signal that triggers an upshift from this FIRST speed ratio to the SECOND speed ratio at Step S1, it proceeds to Step S2, and so on to initiate a control for disengaging the synchromesh mechanism from the FIRST speed gear train GP1 as a preliminary step for the upshift to the SECOND speed ratio (time It in FIG. 7). At first, at Step S2, the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 is shifted and pushed onto THIRD (1) speed gear train GP3(1), and simultaneously, the sleeve of the THIRD/FOURTH speed synchromesh mechanism SM34 is shifted and pushed onto the THIRD (2) speed gear train GP3(2). In other

l l e words, a balk motion is generated by both the synchromesh mechanisms SM35 and SM34.

This balk motion causes the torque of the engine to be transmitted through the THIRD (1) speed gear train GP3(1) and the THIRD (2) speed gear train GP3 (2) to the output shaft. When the torque transmitted by the balk motions through the THIRD (1) speed gear train GP3(1) and the THIRD (2) speed gear train GP3(2) (this is hereinafter referred to as "synchro-torque") becomes equal to the engine torque at Step S3, i.e., when the engine torque is transmitted almost completely through the THIRD (1) speed gear train GP3(1) and the THIRD (2) speed gear train GP3(2) and when the torque transmitted through the FIRST speed gear train GP1, which has been in engagement, becomes almost nil (time t2 in FIG. 7), the control flow proceeds to Step S4. Here, the thrust to disengage the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 from the gear train for the FIRST speed ratio (FIRST extraction force) is increased, so that the action to remove the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 Tom the FIRST speed output gear GO1 is executed smoothly while the torque transmitted through the FIRST speed gear train GP1 is almost nil.

When the sleeve is disengaged in this way, the torque transmission through the FIRST speed gear train GP1 becomes nil, but the torque transmission through the THIRD (1) speed gear train GP3(1) and through the THIRD (2) speed gear train GP3(2) is maintained. As a result, there is no phenomenon of torque loss.

When the action to disengage the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 from the gear train for the FIRST speed ratio completes (i.e., when the FIRST

extraction action completes), the control flow proceeds from Step S5 to Step S6 and Step S7. Here, the operation of the throttle actuator 3 of the engine 2 is controlled to lower the output torque of the engine at Step S6 (time t2 t3), and a balk motion in which the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 is pushed onto the gear train for the SECOND speed ratio is initiated at Step S7 (time t3 t4 t5). In this instance, the rotational speed of the engine decreases, and this decreasing rotational speed is determined whether it has reached the speed (SECOND synchronous rotational speed)-that makes the rotational speed of the SECOND speed output gear G02 of the SECOND speed gear train GP2 synchronous to the rotational speed of the output shaft at Step S8. If the result-of the determination is that the rotational speed of the engine has reached the SECOND synchronous rotational speed, then the control flow proceeds to Step S9 (time t5). In the SECOND speed gear train GP2, the SECOND speed input gear GI2, which is connected to the engine, rotates at a rotational speed that corresponds to the rotational speed of the engine while the SECOND speed output gear G02, which is to be connected to the drive wheels W. should rotate at a rotational speed that corresponds to the rotational speed of the drive wheels W. Here, the SECOND synchronous rotational speed is the speed that makes the SECOND speed output gear G02 synchronous with the output shaft 15 prior to engagement.

While the rotational speed of the engine is maintained at the SECOND synchronous rotational speed, the throttle actuator 3 is controlled to increase the torque of the engine at Step S9, and the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 is shifted to the gear train for the SECOND speed ratio at Step S10

(time t5 t6). By this action, the ratio-change mechanism 4 is completely set at the SECOND speed ratio, so that the power of the engine is transmitted completely through the SECOND speed gear train GP2 (this condition is hereinafter referred to as " SECOND in-

gear state"). In this instance, even if a phenomenon called "gear-out" occurs, the driver never has a feeling of the vehicle moving in an uncontrolled condition because the balk motion is maintained through the THIRD/FOURTH speed synchromesh mechanism SM34 and the THIRD/FIFTH speed synchromesh mechanism SM35.

After the ratio-change mechanism 4 is set in the SECOND in-gear state at Step Sll, the control flow proceeds to Step S12.

Here, the thrust for the balk motion that has maintained the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 to the THIRD (1) speed gear train GP3(1) is reduced, and also, the thrust for the balk motion that has maintained the THIRD/FOURTH speed synchromesh mechanism SM34 to the THIRD (2) speed gear train GP3(2) is reduced (time t6 t7). When these thrusts pushing these synchromesh mechanisms SM34 and SM35 have become nil at Step S13, the control Dow proceeds to Step S14, where both these sleeves are returned to their respective neutral positions, and the upshift from.the FIRST speed ratio to the SECOND speed ratio completes (time t7).

In the above described way, when the ratio-change mechanism 4 is upshifted from the FIRST speed ratio to the SECOND speed ratio, the THIRD/FOURTH and THIRD/FIFTH speed synchromesh mechanisms SM34 and SM35 are brought to the gear trains for the THIRD speed ratio as balk motions. Through these motions, the torque of the engine is transmitted to the output

shaft 15 to replenish the toque which may otherwise disappear at the initiation of the engagement of the FIRST/SECOND speed synchromesh mechanism SM12. Therefore, there is no torque loss, so there is no moment for the driver to feel an uncontrolled movement of the vehicle. This torque replenishment is executed independently from and without any effect on the upshift operation because it uses the THIRD/FOURTH and THIRD/FIFTH speed synchromesh mechanisms SM34 and SM35, not the FIRST/SECOND speed synchromesh mechanism SM12, which is involved directly in the upshift. Furthermore, this arrangement for achieving the torque replenishment, which is executed by the existing synchromesh mechanisms SM, does not require any extra part or unit, so this design does not lengthen the ratio-change mechanism 4 axially.

In this embodiment, the two synchromesh mechanisms SM34 and SM35 are used to replenish a large torque required at the upshift from the FIRST speed ratio to the SECOND speed ratio. - In other words, a large torque being replenished is shared through the two synchromesh mechanisms SM34 and SM35, so that the capacity of each synchromesh mechanism can be small to allow miniaturization of the synchromesh mechanisms. If such miniaturization is not in consideration, then only one synchromesh mechanism, for example, THIRD/FIFTH speed synchromesh mechanism SM35, can be used for the torque replenishment.

The above description is an example of control for an

upshift from the FIRST speed ratio to the SECOND speed ratio, and similar controls can be executed for upshifts involving other speed ratios. FIGS. 8 10 show control steps for executing an upshift from the SECOND speed ratio to the THIRD speed ratio, and FIGS. 11 13

show control steps for executing an upshift from the THIRD speed ratio to the FOURTH speed ratio.

At first, the control for executing an upshift from the SECOND speed ratio to the THIRD speed ratio is described in reference to FIGS. 8 10. At first, when a ratio-change signal that triggers an upshift from this SECOND speed ratio to the THIRD speed ratio is received at Step S21 (time It in FIG. 10), the control flow proceeds to Step S22, the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 is shifted and pushed onto THIRD (1) speed gear train GP3(1) for a balk motion, and simultaneously, the sleeve of the THIRI)/FOURTH speed synchromesh mechanism SM34 is shifted and pushed onto the THIRD (2) speed gear train GP3(2) for a balk motion.

When the torque transmitted by the balk motions through the THIRD (1) speed gear train GP3(1) and the THIRD (2) speed gear train GP3(2) becomes equal to the engine torque at Step S23 (time t2 in FIG. 10) (synchrotorque), the control flow proceeds to Step S24.

Here, the thrust to disengage the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 from the gear train for the SECOND speed ratio (SECOND extraction force) is increased, so that the action to remove the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 from the SECOND speed output gear G02 is executed smoothly while the torque transmitted through the SECOND speed gear train GP2 is almost nil. When the sleeve is disengaged in this way, the torque transmission through the SECOND speed gear train GP2 becomes nil, but the torque transmission through the THIRD (1) speed gear train GP3(1) and through the THIRD (2) speed gear train GP3(2) is maintained.

Therefore, there is no chance for a phenomenon of torque loss to occur.

When the action to disengage the sleeve of the FIRST/SECOND speed synchromesh mechanism SM12 from the gear train for the SECOND speed ratio completes (i.e., when the SECOND extraction action completes) at Step S25, the control flow proceeds to Step S26, where the operation of the throttle actuator 3 of the engine 2 is controlled to lower the output torque of the engine (time t2 time t3). Then, the control flow proceeds to Step S27, where the thrust for the balk motion that is pushing the sleeve of the THIRD/FOURTH speed synchromesh mechanism SM34 onto the THIRD (2) speed gear train GP3(2) is decreased (time t4 t5). When the thrust for the balk motion becomes almost nil at Step S28, the control flow proceeds to Step S29, where a balk motion to push the sleeve of the THIRD/FOURTH speed synchromesh mechanism SM34 onto the FOURTH speed gear train GP4 is initiated (time t6 t7 t8). In this instance, the rotational speed of the engine decreases, and this decreasing rotational speed is determined whether it has reached the speed (THIRD synchronous rotational speed) that is synchronous to the THIRD speed gear train GP3 at Step S30. If the result of the determination is that this speed has reached the THIRD synchronous rotational speed, then the control flow proceeds to Step S31 (time t6).

While the rotational speed of the engine is maintained at the THIRD synchronous rotational speed, the throttle actuator 3 is controlled to increase the torque of the engine at Step S31, and the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 is shifted to the gear train for the THIRD speed ratio at Step S32 (time t7 t8). By this action, the ratio-change mechanism 4 is completely set at the TRD speed ratio, so that the power of the engine is

transmitted completely through the THIRD speed gear train GP3 (this condition is hereinafter referred to as "THIRD in-gear state").

In this instance, even if a phenomenon called "gear-out" occurs, the driver never experiences a feeling of the vehicle moving in an uncontrolled condition, because the balk motion through the THIRD/FOURTH speed synchromesh mechanism SM34 is maintained. After the ratio-change mechanism 4 is set in the THIRD in-gear state at Step S33, the control flow proceeds to Step S34, where the thrust for the balk motion that has maintained the sleeve of the THIRDtFOURTH speed synchromesh mechanism SM34 to the FOURTH speed gear train GP4 is reduced (time t8 to). When this thrust pushing the synchromesh mechanism SM34 has become nil at Step S35, the control flow proceeds to Step S36, where the sleeve of the THIRD/FOURTH speed synchromesh mechanism SM34 is returned to its neutral position, and the upshift Tom the SECOND speed ratio to the THIRD speed ratio completes (time t9). It is clear from the above description that the THIRD speed ratio is established

by the THIRD/FIFTH speed synchromesh mechanism SM35 through the THIRD (1) speed gear train GP3(1).

Now, the control for executing an upshift from the THIRD speed ratio to the FOURTH speed ratio is described in reference to FIGS. 11 13. At first, when a ratio-change signal that triggers an upshift from this THIRD speed ratio to the FOURTH speed ratio is received at Step S41 (time tl), the control flow proceeds to Step S42, the sleeve of the THIRD/FOURTH speed synchromesh mechanism SM34 is shifted and pushed onto the FOURTH speed gear train GP4 for a balk motion.

When the torque transmitted by this balk motion through the FOURTH speed gear train GP4 becomes equal to the engine torque at Step S43 (time t2 in FIG. 13) (synchro-torque), the control flow proceeds to Step S44. Here, the thrust to disengage the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 from the gear train for the THIRD speed ratio (THIRD extraction force) is increased, so that the action to remove the sleeve of the TRD/FIFTH speed synchromesh mechanism SM35 from the gear train for the THIRD speed ratio is executed smoothly while the torque transmitted through the THIRD speed gear train GP3 is almost nil.

When the sleeve is disengaged in this way, the torque transmission through the THIRD speed gear train GP3 becomes nil, but the torque transmission through the FOURTH speed gear train GP4 is maintained by the balk motion of the TH[RD/FOURTH speed synchromesh mechanism SM34 as described above. Therefore there is no chance for a phenomenon of torque loss to occur.

When the action to disengage the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 from the gear train for the THIRD speed ratio completes (i.e., when the THIRD extraction action completes) at Step S45, the control flow proceeds to Step S46, where the operation of the throttle actuator 3 of the engine 2 is controlled to lower the output torque of the engine (time t2 time t3). Then, the control flow proceeds to Step S47, where a balk motion to push the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 onto the FIFTH speed gear train GP5 is initiated (time t3 t4 t5). In this instance, the rotational speed of the engine decreases, and this decreasing rotational speed is determined whether it has reached the speed (FOURTH synchronous rotational

speed) that is synchronous to the FOURTH speed gear train GP4 at Step S48. If the result of the determination is that this speed has reached the FOURTH synchronous rotational speed, then the control flow proceeds to Step S49 (time t8).

While the rotational speed of the engine is maintained at the FOURTH synchronous rotational speed, the throttle actuator 3 is controlled to increase the torque of the engine at Step S49, and the sleeve of the THIRD/FOURTH speed synchromesh mechanism SM34 is shifted to the gear train for the FOURTH speed ratio at Step S50 (time t5 t6 t7). By this action, the ratio-change mechanism 4 is completely set at the FOURTH speed ratio, so that the power of the engine is transmitted completely through the FOURTH speed gear train GP4 (this condition is hereinafter referred to as "FOURTH in-

gear state"). In this instance, even if a phenomenon called "gear-out" occurs with the TH[RD/FOURTH speed synchromesh mechanism SM34, the driver never experiences a feeling of the vehicle moving in an uncontrolled condition, because the balk motion through the THIRD/FIFTH speed synchromesh mechanism SM35 is maintained.

After the ratio-change mechanism 4 is set in the FOURTH in-gear state at Step Set, the control flow proceeds to Step S52, where the thrust for the balk motion that has maintained the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 to the FIFTH speed gear train GP5 is reduced (time t7 t8). When this thrust pushing the THIRD/FIFTH speed synchromesh mechanism SM35 has become nil at Step S53, the control flow proceeds to Step S54, where the sleeve of the THIRD/FIFTH speed synchromesh mechanism SM35 is returned to its neutral position, and the upshift from the THIRD speed ratio to the FOURTH speed ratio completes

(time t8). In this transmission, the FIFTH speed gear train GP5 is not used for ordinary driving.

In the above described control, every time when the ratio-

change mechanism 4 is upshifted from a speed ratio to a next higher speed ratio, a torque replenishment is executed to prevent any occurrence of transmission-torque loss, so the driver never feels an uncontrolled movement of the vehicle. Every torque replenishment is executed through a synchromesh mechanism which is not involved in the upshift operation currently being performed, so it never affects the upshift operation. Furthermore, it should be noted that this torque replenishment in this embodiment according to the present invention is performed with synchromesh mechanisms which are presently available and are usually incorporated in the ratio-change mechanism. Each upshift control described above is executed by shifting axially the sleeve 22 of the respective synchromesh mechanism SM12, SM34 or SM35. The construction and operation of a ratio-change actuator 30, which is used for shifting the sleeves 22 of the synchromesh mechanisms axially for the shift control, is described in the following.

As shown in FIG. 14 FIG. 25 (FIG. 16 shows schematically the construction of a forward drive ratio-change actuator, which is used for electrically controlled speed ratio change control), the ratio-change actuator 30 comprises a first shift fork 31, which engages to the sleeve 22(1) of the first synchromesh mechanism SM12, a second shift fork 32, which engages to the sleeve 22(2) of the second synchromesh mechanism SM35, and a third shift fork 33, which engages to the sleeve 22(3) of the third synchromesh

mechanism SM34. The first shift fork 31 has a pair of claws 31a and 31a at an end thereof, and the first shift fork 31 is positioned with these claws fitting to a groove provided on the sleeve 22(1) and is connected to a first shift rod 36, which is axially movably supported in the transmission housing HSG. Similarly, the second shift fork 32 has a pair of claws 32a and 32a at an end thereof, and the second shift fork 32 is positioned with these claws fitting to a groove provided on the sleeve 22(2) and is connected to a second shift rod 37, which is axially movably supported in the transmission housing HSG. Also, similarly, the third shift fork 33 has a pair of claws 33a and 33a at an end thereof, and the third shift fork 33 is positioned with these claws fitting to a groove provided on the sleeve 22(3) and is connected to a third shift rod 38, which is axially movably supported in the transmission housing HSG. Each of these first third shift rods 36 38 is provided with a plurality of detent slots 36a, 37a and 38a, which are used to determine its axial shift position.

Furthermore, a cylindrical reverse drive shift tube 39 is provided axially movably over the third shift rod 38, and the reverse drive shift tube 39 has an engaging arm 39a, which is fixed thereon and engages to the second shift rod 37 to prevent the reverse drive shift tube 39 from rotating (while allowing axial movement). The reverse drive shift tube 39 also includes a shift arm 39b attached thereon, which arm engages to a REVERSE middle gear GMR to shift it axially.

As shown in the drawings, a shift transmission mechanism 40 is provided externally out of the transmission housing HSG, and it comprises first third shift actuators 41 43, which are, for example, electrical stepping motors. The shift transmission mechanism 40

includes first third driven gear members 46 48, each of which has a driven gear therearound, and these driven gears mesh with first third drive gears 41a 43a provided on the first third shift actuators 41 43. The first third driven gear members 46 48 are connected to first third shift drive shaft members 51 53, respectively, which are coaxially disposed cylindrical tubular members and are rotatable with respect to one another. In addition, first third shift arms 51a, 52a and 53a, each of which extends radially outward, are provided at the lower ends of the respective first third shift drive shaft members 51 53.

Furthermore, over the third shift drive shaft member 53, which is disposed at the outermost position of the three shift drive shaft members, a reverse shift drive shaft member 54 having a reverse shift arm 54a at the lower end thereof is provided coaxially.

At the top end of the reverse shift drive shaft member 54, provided fixedly is a disc-like reverse flange member 49 comprising a connection arm 49a, which extends radially outward, and a connection pin 49b, which stands upward on the connection arm 49a.

In addition, a wire, which is pulled and released in correspondence to the operation of the shift lever 7, is connected to the connection pin 49b. The first third shift arms 51a, 52a and 53a are in engagement with first third link members 56 58, which are connected to the first third shift rods 36 38, respectively.

Specifically, as shown in FIG. 23, a U-shaped receptor 56a is provided at an end of the first link member 56, which is connected to the first shift rod 36 and extends laterally, and the first shift arm 61a is fit in the Ushaped receptor 56a. In this arrangement, when the first shift

drive shaft member 51 is rotated by the first shift actuator 41 through the first drive gear 41a and the first driven gear member 46, the first shift arm 51a rotating together with the first shift drive shaft member 51 shifts the first shift rod 36 axially, through the first link member 56. As the first shift fork 31 is connected to the first shift rod 36, the first shift fork 31 is also shifted axially to meet and move the sleeve 22(1) of the first synchromesh mechanism SM12 axially. Therefore, if the rotational drive of the first shift actuator 41 is controlled appropriately, the operation of the first synchromesh mechanism SM12 can be controlled through the axial shift of the sleeve 22(1).

In the same way, if the rotational drive of the second and third shift actuators 42 and 43 is controlled appropriately, the operation of the second and third synchromesh mechanisms SM35 and SM34 can be controlled on the basis of the same operational principle. On the other hand, the reverse shift arm 54a is received and fit in a U-shaped receptor 59a provided at an end of a reverse link member 59, which is connected to the reverse drive shift tube 39. In this arrangement, when the driver operates the shift lever 7 to the REVERSE position, because this operation is linked through the above mentioned wire to the connection pin 49b, thereverse shift drive shaft member 54 is rotated. As a result, the reverse shift arm 54a rotates and, through the reverse link member 59, shifts the reverse drive shift tube 39 axially on the third shift rod 38. This axial shift of the reverse drive shift tube 39 also shifts the REVERSE middle gear GMR axially through the shift arm 39b to engage or disengage the REVERSE speed ratio in the ratio-change mechanism 4.

As described, the first third shift arms 51a, 52a and 53a

and the reverse shift arm 54a are received and fit, respectively, in the U-shaped receptor 56a, 57a, 58a and 59a provided at ends of the first third link members 56 58 and the reverse link member 59, which are positioned next to one another. Therefore, the shift mechanism (the first third link members, the reverse link member, and the shift rods and claws connected to these members), which is incorporated conventionally in a manual transmission, needs no change to control the operation of each synchromesh mechanism independently. It is clear from this that, according to the present invention, an automatic transmission based on a manual transmission can be achieved with little change of the overall design but a little change in the ratio-

change mechanism.

As described above, the rotational drive of the first third shift actuators 41 43 is controlled so as to control the operation of the first third synchromesh mechanisms SM12, SM35 and SM34.

As the first third shift actuators 41 43 are operable independently in this arrangement, there is a concern that a plurality of synchromesh mechanisms may be actuated for engagement simultaneously. To solve this problem, the shift transmission mechanism 40 in this embodiment includes an actuation-regulating mechanism. This actuation-regulating mechanism comprises a regulating member 60 (refer to FIGS. 25 and 29), which is fixed in the housing HSG. The regulating member 60 comprises first third semi-circular disc portions 61, 62 and 63 extending laterally and among the first third driven gear members 46 48 and the reverse flange member 49, which are rotatable with respect to one another because needle bearings 71 74 are provided therebetween. On the

sides of the first third driven gear members 46 48 and the reverse flange member 49 that face the first third semi-circular disc portions 61, 62 and 63, various recesses and slots are provided along arc A and arc B as shown in FIG. 26 FIG. 28.

FIG. 26A is a bottom view of the first driven gear member 46. The first driven gear member 46 has two recesses 46a and 46b along arc A and a recess 46c along arc B. In the drawing, the part shown in hatching is the surface of the first driven gear member 46 on which the needle bearing rolls. In the following figures, the hatched parts are also the surfaces where the respective needle bearings roll. FIG. 26B is a top view of the second driven gear member 47, which faces the bottom surface of the first driven gear member 46. On this top surface, the second driven gear member 47 has a recess 47a and a slot 47b along arc A and a slot 47c along arc B. FIG. 27A is a bottom view of the second driven gear member 47 with the above mentioned slots 47b and 47c. On this bottom surface, the second driven gear member 47 has two recesses 47d and 47e along arc A. FIG. 27B is a top view of the third driven gear member 48, which faces the bottom surface of the second driven gear member 47. On this top surface, the third driven gear member 48 has two slots 48a and 48b and a recess 48c along arc A and a recess 48d along arc B. FIG. 28A is a bottom view of the third driven gear member 48 with the above mentioned slots 48a and 48b. On this bottom surface, the third driven gear member 48 has a recess 48e along arc A. FIG. 28B is a top view of the reverse flange member 49, which faces the bottom surface of the third driven gear member 48. On this top surface, the reverse flange member 49 has three recesses 49a, 49b

and 49c along arc A. FIGS. 30 49 are expanded sectional views of the actuation-regulating mechanism comprising the regulating member 60, the first third driven gear members 46 48 and the reverse flange member 49. As shown in this assembled condition, first third regulating balls 71 73 and first third regulating pins 76 78 are provided in the recesses and slots of the first third driven gear members 46 48 and in through-holes which are provided through the first third semi-circular disc portions 61, 62 and 63 of the regulating member 60. In the drawings, the relations of these members are shown in a top-to-bottom order opposite of that shown in FIG. 25, and this mechanism is sectioned along arc A and arc B and opened to help the following description. All the drawings show the

same section, and the rotational shifts of the first third driven gear members 46 48 and the reverse flange member 49 are shown as lateral shifts. FIG. 30 shows all the above mentioned recesses and slots with their indication numbers, but other drawings do not include all these indication numbers to avoid redundancy because the recesses and slots occupy the same positions in all the drawings. In reference to these drawings, the operation of the actuation-regulating mechanism is now described in correspondence to the speed ratio change control executed through the first third shift actuators 41 43. FIGS. 30 34 show sequentially the rotational shifts of the first third driven gear members 46 48 and the reverse flange member 49 that occur for the upshift of the ratio-change mechanism from the FIRST speed ratio to the SECOND speed ratio, which upshift operation is controlled as described above in reference to FIG.

5 FIG. 7. In this case, the reverse flange member 49 is fixed stationary because the shift lever 7 is in the forward drive range.

FIG. 30 shows the condition where the ratio-change mechanism 4 is set at the FIRST speed ratio. In this condition, the first driven gear member 46 is rotated leftward in the drawing, and the sleeve 22(1) of the first synchromesh mechanism SM12 is shifted completely to the FIRST speed ratio side. As shown in the drawing, in this condition, the second driven gear member 47 can be rotated leftward as far as the clearance that is provided by the slots 47c and 47b against the respective regulating pins 77 and 78 and by the movement of the regulating ball 73 in the recess 47a allows. With this clearance, the sleeve 22(2) of the second synchromesh mechanism SM35 can be shifted toward the THIRD(1) speed ratio side to achieve a balk motion but no further than that. In this instance, the regulating ball 72 is lifted upward into the recess 48c.

Similarly, the third driven gear member 48 can be rotated leftward as far as the clearance that is provided by the slots 48a and 48b against the respective regulating pins 78 and 76j by the recess 48d against the regulating pin 77 and by the recess 48c against the regulating ball 72, which is lifted therein, allows. With this clearance, the sleeve 22(3) of the third synchromesh mechanism SM34 can be shifted toward the THIRD(2) speed ratio side to achieve a balk motion but no further than that. In this instance, the regulating ball 71 is lifted upward into the recess 49a.

FIG. 31 shows the condition where the second and third synchromesh mechanisms SM35 and SM34 are set in the respective balk motions. In this condition, the second and third driven gear members 47 and 48 cannot be rotated leftward any further.

As shown in FIG. 32, while the balk motions are maintained, the first driven gear member 46 is rotated rightward to shift the sleeve 22(1) of the first synchromesh mechanism SM12 into the neutral position for the FIRST extraction action, which is described above. Then, as shown in FIG. 33, the first driven gear member 46 is rotated further rightward to shift the sleeve 22(1) of the first synchromesh mechanism SM12 to the SECOND speed ratio side, so that a balk motion is achieved by this rightward rotation. In this condition, because of the regulating pins 77 and 78, the second and third driven gear members 47 and 48 can be shifted only between the position for the above described balk motion and the neutral position, so there is no possibility for the second and third synchromesh mechanisms SM35 and SM34 to be actuated for engagement simultaneously. From this condition, the first driven gear member 46 is rotated further rightward, and the first driven gear member 46 is brought into the rightmost position as shown in FIG. 34. In this condition, the sleeve 22(1) of the first synchromesh mechanism SM12 is shifted completely into the SECOND speed ratio side, and the ratio-

change mechanism is set at the SECOND speed ratio for a power transmission through the SECOND speed gear train GP2. Then, the second and third driven gear members 47 and 48 are returned to the neutral position to release the second and third synchromesh mechanisms SM35 and SM34 from the respective balk motions as shown in FIG. 35, completing the control executed for the upshift to the SECOND speed ratio.

In this condition, the regulating ball 73 is in the recess 47a, restricting the movement of the second driven gear member 47, and

the regulating pin 77 is in the recess 48d, restricting the movement of the third driven gear member 48. Therefore, while the SECOND speed ratio is established in this condition, there is no possibility for the second and third synchromesh mechanisms SM35 and SM34 to be actuated for setting another speed ratio. Furthermore, the regulating pin 78 is in the recess 49c, restricting the movement of the reverse flange member 49. Therefore, there is no possibility also for the REVERSE speed ratio to be established.

Now, the rotational shifts of the first third driven gear members 46 48 and the reverse flange member 49 for executing the upshift from the SECOND speed ratio to the THIRD speed ratio are described in reference to FIGS. 36 41, which show sequentially the rotational shifts of these members. These rotational shifts correspond to the control steps described above in reference to FIG. 8 FIG. 10.

FIG. 36 shows the condition where the ratio-change mechanism is set at the SECOND speed ratio. In this condition, the first driven gear member 46 is rotated to the rightmost position as described above, and the sleeve 22(1) of the f irst synchromesh mechanism SM12 is shifted completely to the SECOND speed ratio side. The other members, i.e., the second and third driven gear members 47 and 48 and the reverse flange member 49 are at the neutral position.

In this condition, the second driven gear member 47 can be rotated leftward as far as the clearance that is provided by the movement of the regulating ball 73 in the recess 47a allows. With this clearance, by lifting the regulating ball 72 upward into the recess 48c, the sleeve 22(2) of the second synchromesh mechanism SM35 can

be shifted toward the THIRD(1) speed ratio side to achieve a balk motion but no further than that. Similarly, the third driven gear member 48 can be rotated leftward as far as the clearance that is provided by the slots 48a and 48b against the respective regulating pins 78 and 76, by the recess 48d against the regulating pin 77 and by the recess 48c against the regulating ball 72, which is lifted therein, allows. With this clearance, by lifting the regulating ball 71 upward into the recess 49a, the sleeve 22(3) of the third synchromesh mechanism SM34 can be shifted toward the THIRD(2) speed ratio side to achieve a balk motion but no further than that.

For this upshift, at first, the second and third driven gear members 47 and 48 are shifted leftward to bring the second and third synchromesh mechanisms SM36 and SM34 into the respective balk motions as shown in FIG. 37. It is clear from the drawing that the second and third driven gear members 47 and 48 cannot be rotated leftward any further than the position where they are shifted for the respective balk motions.

As shown in FIG. 38, while the balk motions are maintained, the first driven gear member 46 is rotated leftward to shift the sleeve 22(1) of the first synchromesh mechanism SM12 into the neutral position for the SECOND extraction action. Then, as shown in FIG. 39, the third driven gear member 48 is rotated rightward to shift the sleeve 22(3) of the third synchromesh mechanism SM34 so as to terminate the balk motion. After the termination of the balk motion, the third driven gear member 48 is rotated further rightward to push the sleeve 22(3) of the third synchromesh mechanism SM34 to the gear train for the FOURTH speed ratio so as to achieve a balk motion.

Then, the second driven gear member 47 is rotated leftward to engage the sleeve 22(2) of the second synchromesh mechanism SM35 to the THIRD speed gear train GP3(1) as shown in FIG. 40. In the condition where the sleeve 22(2) of the second synchromesh mechanism SM35 is shifted completely to the THIRD speed ratio side, the ratio-change mechanism is set at the THIRD speed ratio for a power transmission through the THIRD speed gear train GP3(1). As shown in FIG. 41, the third driven gear member 48 is returned to the neutral position to disengage the third synchromesh mechanism SM34 so as to terminate the balk motion.

As a result, the control for executing the upshift to the THIRD speed ratio completes.

In this condition, the regulating ball 73 is in the recess 46c, restricting the movement of the first driven gear member 46, and the regulating ball 72 is in the recess 48c, restricting the movement of the third driven gear member 48. Therefore, while the THIRD speed ratio is established in this condition, there is no possibility for the first and third synchromesh mechanisms SM12 and SM34 to be actuated for setting another speed ratio. Furthermore, the regulating pin 76 is in the recess 49b, restricting the movement of the reverse flange member 49. Therefore, there is no possibility also for the REVERSE speed ratio to be established.

Now, the rotational shifts of the first third driven gear members 46 48 and the reverse flange member 49 for the upshift from the THIRD speed ratio to the FOURTH speed ratio are described in reference to FIGS. 42 47, which show sequentially the rotational shifts of these members. These drawings show sequentially the control steps that correspond to the control described

above in reference to FIG. 11 FIG. 13.

FIG. 42 shows the condition where the ratio-change mechanism is set at the THIRD speed ratio. In this condition, the second driven gear member 47 is rotated to the leftmost position as described above, and the sleeve 22(2) of the second synchromesh mechanism SM35 is shifted completely to the THIRD(1) speed ratio side. The other members, i.e., the first and third driven gear members 46 and 48 and the reverse flange member 49, are all at the neutral position.

In this condition, the third driven gear member 48 can be rotated rightward as far as the clearance that is provided by the movement of the regulating ball 72 in the recess 48c allows. With this clearance, by lifting the regulating ball 71 upward into the recess 49a, the sleeve 22(3) of the third synchromesh mechanism SM34 can be shifted to the FOURTH speed ratio side to achieve a balk motion but no further than that. For this upshift, at first, the third driven gear member 48 is rotated rightward to set the third synchromesh mechanism SM34 for a balk motion as shown in FIG. 43. It is clear from this drawing that the third driven gear member 48, which has been shifted rightward to the position for the balk motion, cannot be rotated rightward any further.

While this balk motion is maintained, as shown in FIG. 44, the second driven gear member 47 is rotated rightward to shift the sleeve 22(2) of the second synchromesh mechanism SM35 to the neutral position for the THIRD extraction action described above.

Then, the second driven gear member 47 is rotated further rightward to push the sleeve 22(2) of the second synchromesh mechanism SM35 to the gear train for the FIFTH speed ratio so as to achieve a balk

motion as shown in FIG. 46.

After that, the third driven gear member 48 is shifted rightward, as shown in FIG. 46, to engage the sleeve 22(3) of the third synchromesh mechanism SM34 to the gear train for the FOURTH speed ratio. As the sleeve 22(3) of the third synchromesh mechanism SM34 is shifted completely to the FOURTH speed ratio side, the ratio-change mechanism is set at the FOURTH speed ratio for a power transmission through the FOURTH speed gear train GP4. As shown in FIG. 47, the second driven gear member 47 is returned to the neutral position to disengage the third synchromesh mechanism SM35 so as to terminate the balk motion. As a result, the control executed for the upshift to the FOURTH speed ratio completes.

In this condition, the regulating pin 77 is in the recess 46b, restricting the movement of the first driven gear member 46, and the regulating ball 72 is in the recess 47e, restricting the movement of the second driven gear member 47. Therefore, while the FOURTH speed ratio is established in this condition, there is no possibility for the first and second synchromesh mechanisms SM12 and SM35 to be actuated for setting another speed ratio. Furthermore, the regulating ball 71 is in the recess 49a, restricting the movement of the reverse flange member 49. Therefore, there is no possibility also for the REVERSE speed ratio to be established.

Now, the establishment of the REVERSE speed ratio is described in reference to FIGS. 48 and 49. FIG. 48 shows the NEUTRAL condition, where the first third driven gear members 46 48 and the reverse flange member 49 are all at the neutral position.

As described above, when the driver operates the shift lever 7 to the REVERSE position, the reverse flange member 49 is rotated

rightward to set the REVERSE speed ratio as shown in FIG. 49.

- In this condition, where the ratio-change mechanism is set at the REVERSE speed ratio, the regulating pin 78 is in the recess 46a, restricting the rotational movement of the first driven gear member 46, the regulating pin 76 is in the recess 47d, restricting the rotational movement of the second driven gear member 47, and the regulating ball 71 is in the recess 48e, restricting the rotational movement of the third driven gear member 48. Therefore, while the REVERSE speed ratio is established in this condition, there is no possibility for any forward drive speed ratio to be established.

As described above, the shift transmission mechanism according to the present invention comprises coaxially disposed cylindrical tubular members in a telescope-like construction, each member being rotatable independently. Each tubular member is rotated by a shift actuator, and this rotational movement is transmitted through a link member to a shift fork member, so that a corresponding mechanical clutch is engaged or disengaged by the movement of the shift fork member. This arrangement allows miniaturization of the shift transmission mechanism, which actuates a plurality of mechanical clutches.

Furthermore, the ratio-change mechanism according to the present invention is provided with a plurality of shift plates, each of which is connected to a corresponding tubular member and rotates together with the respective tubular member, and with a plurality of regulating members, each member being positioned between the shift plates. In this case, each regulating member is designed to restrict the rotational range of a corresponding tubular member, which is rotated by a shift actuator. As a result, even though the ratio-change

mechanism is small in size or compact, the mechanical clutches can be controlled securely not to engage simultaneously in plurality.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. RELATED APPLICATIONS

This application claims the priority of Japanese Patent Application No. 2001-396709 filed on December 27, 2001, which is incorporated herein by reference.

Claims (7)

WHAT IS CLAIMED IS:

1. A ratio-change mechanism for a transmission, used for speed ratio change control in a power transmission that transmits a driving force of a prime mover to drive wheels through said transmission having a plurality of speed ratios; wherein: said transmission comprises an input member, which is connected to said prime mover, an output member, which is connected to said drive wheels, a plurality of power transmission gear trains, which provide a plurality of power transmission paths between said input member and said output member, a plurality of mechanical clutches, which selectively set said power transmission gear trains for a power transmission so as to selectively establish said power transmission paths, and a clutch actuation mechanism, which selectively actuates said mechanical clutches; said clutch actuation mechanism comprises a plurality of shift fork members, which are used to engage and disengage said mechanical clutches, a shift transmission mechanism, which shifts each of the shift fork members independently in an engaging direction or in a disengaging direction, and a plurality of shift actuators, which actuate said shift transmission mechanism; and said shift transmission mechanism comprises a plurality of cylindrical tubular members and a plurality of link members, said tubular members being disposed coaxially over one another with each tubular member being rotatable independently by a corresponding one of said shift actuators, and said link members connecting each of said tubular members to a corresponding one of said shift fork

r members and shifting said shift fork members in said engaging direction or in said disengaging direction in correspondence to the rotation of said tubular members.

À.

2. The ratio-change mechanism for a transmission, as set forth in 'claim 1, wherein said mechanical clutch' comprises a synchromesh mechanism.

3. The ratio-change mechanism for a transmission as set.

forth in claim 1 or 2, wherein: : ' said shift actuators comprise electrical stepping motors; ' drive gears provided' on drive shafts of said electrical stepping motors mesh with driven gears provided on said tubular n?embers; and said tubular 'members are rotated through.said driven gears by said electrical stepping motors, which rotate said drive gears.

4. The ratio-change mechanism for a transmission, as set forth in claim 1 or 2, wherein:: a plurality of shift plates are provided, each shift plate being connected to a corresponding one of said tubular members so as to rotate together as a unit; a plurality of regulating members are provided, each regulating member being positioned between said shift plates; and said regulating members restrict rotational ranges of said tubular members, which are rotated by said shift actuators, so as to prevent said mechanical clutches from engaging simultaneously in plurality.

À

5. The ratio-change mechanism for a transmission, as set forth in claim 4, wherein: said shift actuators comprise electrical stepping motors; duve gears provided on drive shaflcs of said electrical stepping motors mesh with driven gears which are provided around outer peripheries of said shift plates; and said tubular members are rotated by said electrical stepping motors, which rotate said shift plates.

6. The ratio-change mechanism for a.transmission, as set forth in claim 5, wherein: said regulating members comprise a plurality of disc members and a plurality of regulating balls and regulating pins; À said disc members are fixed stationary. to be positioned between facing surfaces of said shift plates; and said regulating balls and regulating pins are positioned in À a plurality of recesses and slots. that are provided in facing surfaces of said shier plates and disc members.

7. A ratio-change mechanism for a transmission, substantially as hereinbefore described with reference to the accompanying drawings.