WO1996023671A1

WO1996023671A1 - Clutch and transmission ratio control

Info

Publication number: WO1996023671A1
Application number: PCT/GB1996/000213
Authority: WO
Inventors: John Spooner; Paul Malcolm Darnell
Original assignee: Automotive Products Plc
Priority date: 1995-02-03
Filing date: 1996-02-01
Publication date: 1996-08-08
Also published as: GB9502140D0; GB2301408A; GB9619563D0; GB2301408B

Abstract

A clutch and transmission ratio control system in which a main solenoid-operated valve (14) distributes pressurized fluid to a clutch actuator (18) or a ratio selector valve (19) in response to signals from an electronic control means (16). The ratio selector valve (19) in turn distributes pressurized fluid to a plurality of ratio selector actuators (20, 21) which control the movement of a plurality of ratio selector elements (20c, 21c). In a preferred construction both the main solenoid-operated valve (14) and ratio selector valve (19) are landed spool valves.

Description

CLUTCH AND TRANSMISSION RATIO CONTROL

This invention relates to systems for the control of clutch engagement and transmission ratio selection in a motor vehicle.

In particular the invention is concerned with the provision of a system for fully automating a semi-automatic transmission of the form described in, for example, the Applicants earlier European patents Nos. 0038113, 0043660, 0059035 and 0101220 by automating gear ratio selection in addition to clutch operation.

According to the present invention there is provided a clutch and transmission ratio control system in which a main solenoid-operated valve distributes pressurised fluid to a clutch actuator or a ratio selector valve in response to signals from an electronic control means, the ratio selector valve in turn distributing pressurised fluid to a plurality of ratio selector actuators which control the movement of a plurality of ratio selector elements.

Preferably the main solenoid operated valve is a spool valve in which a solenoid-operated spool controls the communication of pressurised fluid from an inlet port to a clutch actuator port, a drain port and a ratio selector valve port.

The inlet port of the main solenoid operated valve may be centrally located with the clutch actuator port and ratio selector valve port disposed one on each side of the inlet port and with the drain port located axially outwardly of the actuator port, the valve spool being provided with a number of axially spaced lands which are capable of isolating the inlet port from the other ports in one axial position of the spool, connecting the inlet port to the ratio selector valve port and the clutch actuator port to the drain port in a second axial position of the spool , and connecting the inlet port to the ratio selector valve port and controlling the flow of fluid to and from the clutch actuator port over a range of axial positions.

The ratio selector valve may comprise a solenoid-operated spool valve in which a solenoid-operated spool controls communication between an inlet port connected with the main solenoid-operated valve, actuator ports each connected with a respective ratio selector actuator, and one or more drain ports.

In a two actuator ratio selector control valve the inlet port may be centrally located with two actuator ports disposed one on each side of the inlet port with a drain port located axially outwardly of each actuator port, the valve spool being provided with a central land which closes off the inlet port when the spool is in a central position and two outer lands one on each side of the central land which isolate each actuator port from the adjacent drain port in the central position of the spool, movement of the spool a first distance in one direction from the central position opening communication between the inlet and one actuator port around the central land and movement of the spool a further distance in said one direction closing off communication between the inlet and said one actuator port and opening communication between said one actuator port and the adjacent drain port around one of the outer lands, movement of the spool a first distance in the other direction from the central position opening communication between the inlet and the other actuator port around the central land and movement of the spool a further distance in said other direction closing of communication between the inlet and said other actuator port and opening communication between the other actuator port and the other drain port around the other outer land.

The present invention also provides both a spool-type main solenoid-operated valve and a spool-type ratio selector valve of the form described above.

The invention further provides a clutch and transmission ratio control system as described above in which either the main solenoid-operated valve or the ratio selector valve is replaced by two separate solenoid-operated valves which carry out the two functions of each respective valve.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a clutch control and ratio selection system in accordance with the present invention:

Figure 2 shows a ratio selection gate of the associated gear box;

Figures 3a - 3c show various spool positions of a main solenoid-operated valve which forms part of the control system and

Figure 4 diagrammatically shows various spool positions of a ratio selector valve which also forms part of the control system.

The control system includes an hydraulic pump 10 driven by an electric motor 11 and which draws fluid from a sump 12. Fluid from pump 10 is supplied to an accumulator 13 and hence to a main solenoid-operated valve 14. A pressure sensitive switch 15 is also provided which sends a signal to an electronic control unit 16 if the pressure in the system supplying valve 14 falls below a predetermined level. On receipt of this signal the control unit 16 issues a signal to electric pump 11 via line 17 to switch on the electric pump 11 in order to raise the system pressure above a further predetermined level. Main solenoid-operated valve 14 controls the supply of pressurised fluid to a clutch actuator 18 via line 50 and, via line 49, to a ratio selector valve 19 and to the rod ends 20a and 2la of gear selector actuators 20 and 21. In turn the ratio selector valve 19 distributes pressurised fluid to the head ends 20b and 21b of actuators 20 and 21. Using actuators 20 and 21 the gear ratios of an associated gear box (not shown) whose ratio selection gate is shown at 22 in figure 2 can be selected by the control system using a combination of movements in the X direction of figure 2 using actuator 20 and in the Y direction of figure 2 using actuator 21.

Returning now to the details of the system, the main solenoid-operated valve 14 comprises an outer portion 30 which is inserted into a bore 31 in a housing 32 and is held stationary therein. Outer portion 30 defines, in conjunction with bore 31, annular feed passages 33,34 and 35 which are connected respectively to the ratio selector valve 19, the inlet from pump 10 and the clutch actuator 18.

Within outer valve portion 30 is disposed an axially movable landed spool 36 which, when solenoid 14a of valve 14 is not actuated, it is maintained in the position shown in figures 1 and 3a by return springs 37 and 38. Return spring 38 acts against a threaded nut 39 whose axial position within a threaded bore 40 controls the spring loading on spool 36 as described in the Applicant's co-pending application No. 9308539 . 7 .

Spool 36 includes an axially extending drilling 41 which connects chambers 42 and 43 at both ends of the spool. These chambers are connected via drain line 60 with sump 12. Figures 1 and 3a show spool 36 in the switched-off position occupied when the solenoid 14a of the valve 14 is not activated. In this position spool lands 44 and 45 isolate the annular inlet feed passage 34 from feed passages 33 and 35. Outer spool land 46 allows communication between feed passage 33 and drain line 60 via chamber 42, drilling 41 and chamber. Outer land 47 isolates annular feed passages 35 from drain line 60. Thus in the figure 1 switched-off position no flow occurs from inlet feed passage 34 to passages 33 and 35 and any pressure in line 49 is drained to line 60 to depressurise actuators 20 and 21.

As indicated previously, the output from supply passage 33 passes to the inlet 48 of ratio selector valve 19 and also to the rod ends 20a and 21a of gear selector actuators 20 and 21 respectively. The output from annular feed passage 35 passes to clutch actuator 18 via line 50. Pressurisation of actuator 18 releases the associated clutch (not shown) via a linkage 18a which includes a release bearing 18b.

The basic constructional details of ratio selector valve 19 are similar to those of main solenoid-operated valve 14 and thus those components of valve 19 having a similar function to the components of valve 14 have been similarly numbered with their reference numerals increased by 100.

The lands on spool 136 of valve 19 are somewhat different from those of spool 36 of valve 14 and when the solenoid 19a of valve 19 is switched-off the spool 136 occupies the position shown in figures 1 and 4a in which annular feed passages 133,134 and 135 are again isolated from each other.

As can be seen from figure 1, feed passage 133 outputs pressure to the head end 20b of gear selector actuator 20 whilst feed passage 135 outputs pressure to the head end 21b of gear selector actuator 21.

Both actuators 20 and 21 have rods and associated linkages indicated in figure 1 at 20c and 21c respectively which effect movements of an associated gear selection linkage (not shown) in direction X and Y respectively. The position of each actuator rod 20c and 21c is indicated by a position sensor 20d and 21d respectively which feed back position signals to control unit 16.

Actuators 20 and 21 operate on a differential area principle under which if, for example, the supply pressure from line 49 is applied to both ends of actuator 20 the actuator rod 20c will move to the right, the rod 20c being moved to the left by connecting pressure from line 49 to the rod end of actuator 20 only and allowing fluid to drain from the head end of the actuator.

Control unit 16 also receives other input signals, indicated diagrammatically at S in figure 1, indicative of various vehicle operating parameters such as clutch engagement position measured by sensor 51, throttle pedal position and gear engaged signal from sensors 20d and 21d. Full constructional and operational details of the electronic control unit 16 can be found in the Applicants previously referred to earlier patents and will not therefore be given here. It is sufficient to say that control unit 16 issues signals to solenoid 14a which controls the position of spool 36 to control the rate of engagement and disengagement of the clutch operated by actuator 18 and also the distribution of pressurised fluid to valve 19. Similarly control unit 16 also issues signals to solenoid 19a to control the operations of actuators 20 and 21 in order to select the operative ratio in the associated transmission which control unit 16 has deemed appropriate.

Before beginning a detailed operation of the control system the spool positions which spools 36 and 136 may occupy depending on the current applied to solenoids 14a and 19a will be briefly described.

Figure 1 shows spool 36 in its switched-off position when no solenoid current is applied to solenoid 14a. On application of a first level of current to solenoid 14a spool 36 is movable to the right from the figure 1 position (also shown in figure 3a) to the figure 3b position in which fluid from inlet passage 34 can flow to outlet passage 33 via flowpath F around spool land 44 and fluid can flow from clutch actuator 18 to drain line 60 around spool land 47 by drain path D.

If the solenoid current is further increased spool 36 can be displaced further to the right to the figure 3c position in which land 45 bridges the feed passage 35. This is the so-called null clutch control position from which the spool 36 can be moved to the right (by increasing solenoid current) in order to connect passage 35 with pressure from passage 34 or to the left (by decreasing solenoid current) in order to connect passage 35 with the drain line 60.

Thus the level of clutch engagement is controlled by the electronic control unit 16 by varying the solenoid current thus moving spool 36 to the left or right from the null position shown in figure 3c. As will be noted, when the spool 36 is in its null position or is being moved to the left or right to control the position of the clutch actuator 18 the feed passage 33 always remains connected to the inlet passage 34 so that pressure is available to valve 19 and to the rod ends 20a and 21a of actuators 20 and 21.

Valve spool 136 occupies the position shown in figures 1 and 4a when the solenoid 19a is switched-off. Figures 4b to 4f show the five basic positions of spool 136 corresponding to different solenoid current levels.

When in the switched-off figure 4a position the feed passages 133,134 and 135 are all isolated from each other and from the return line 160 by lands 144,145,146 and 147.

Movement of spool 136 to the figure 4b position locates land 145 bridging feed passage 135. This is the so-called Y-null position from which the spool can be moved to the left to the figure 4c position (by decreasing solenoid current) to connect feed passage 135 with drain line 160 to provide return flow DY or to the right to the fig 4d position (by increasing solenoid current) to connect feed passage 135 (and hence end 21b of Y actuator 21) with the inlet feed passage 134 to provide a flow PY of fluid to actuator 21.

In the figure 4b to 4d positions feed passage 133 remains isolated both from the drain line 160 and from the inlet feed passage 134 by land 144.

The figure 4e position is arrived at by applying further solenoid current to displace spool 136 still further to the right. In this position land 144 bridges the inlet annular feed passage 134 cutting off the flow from passage 134 to the passages 133 and 135. This is the so called null or central position of the spool 136 in which movement of the spool to the left initiates flow to the head end 21b of Y actuator 21 and movement of spool 136 to the right initiates pressurisation of the head end 20b of the X actuator 20.

The application of still further solenoid current displaces spool 136 further to the right to the figure 4f position in which the land 146 bridges the feed passage 133. This is the so-called X-null position from which the spool can be moved to the left to the figure 4g position (by decreasing solenoid current) to connect inlet feed passage 134 with feed passage 133 and to provide a flow PX to the head end 20b of the X-actuator 20. Spool 136 can also be moved to the right of the X-null position (by increasing solenoid current) to provide a return flow DX from feed passage 133 to drain line 160 down the central bore 141 in spool 136 as shown in figure 4h.

It will be appreciated from the above description, when the spool is in the figure 4d condition and pressurised fluid is directed to feed passage 135 and hence to the Y actuator, the X actuator is completely isolated both from the source of pressure and also from the drain line 160 by lands 144 and 146 respectively. Similarly when in the figure 4g condition and pressurised fluid is directed to the X actuator, flow to and from the Y actuator is prevented by lands 144 and 145 respectively.

Having now described the various operational positions of the spools 36 and 136 a brief description will be given of the operation of the valves 14 and 19 to control clutch actuator 18 and ratio selector actuators 20 and 21 respectively.

Assuming that the vehicle fitted with the control system is stationary with the engine turned off, and that the transmission is in neutral. When the ignition key is turned on it will be assumed that the system is pressurised either as a result of residual pressure from a previous operation of the vehicle or due to initial priming of the system by the pump 10 being turned on ahead of the operation of the ignition switch by, for example, the system sensing the presence of the operator in the vehicle and initiating operation of the pump. Such a system charging arrangement is disclosed in the Applicants co-pending UK Patent Application No.9310540.1.

Initially when the system is activated the main valve 14 will be in the figure l position so that no pressurised fluid is fed to valve 19 and land 47 cuts-off communication between clutch actuator 18 and drain line 60.

In fact land 47 is provided with a small cross-section leakage path which extends axially across land 47 thus providing very low level drainage of pressure from actuator 18 to drain line 60 even in the figure 1 position. This leakage path is provided in order to ensure a natural tendency for the pressure in clutch actuator 18 to leak away over a relatively long period of time so that the associated clutch will become engaged.

To begin the selection of first gear in order to enable the vehicle to drive away from rest, the system moves the spool 136 of valve 19 to its null or central position shown in figure 4e. The valve 14 is then switched-on to move spool 36 to a position to the right of the figure 3c position in order to pressurise clutch actuator 18 to disengage the associated clutch and also to supply pressurised fluid to valve 19.

Assuming that the transmission is in neutral, the selector mechanism must be moved in the X directions either to the left or right depending on its currently occupied position which reguires the appropriate movement of actuator 20 to the left or right. This is achieved by switching-off pressure to valve 19, by returning valve 14 to the figure 3a position and then moving spool 136 of valve 19 to the so called X-null position (figure 4f) in which land 146 bridges feed passage 133. Pressure is then re-applied to valve 19 by displacing spool 36 to the right to the figure 3c null position thus also ensuring that the clutch actuator 18 remains in its pressurised disengaged position. The position of X actuator 20 is then controlled by movement of spool 136 to the left or right of this its X-null position (figure 4f) to occupy positions 4g and 4h respectively until the X position of the selector mechanism is aligned with the first gear selection plane in the gear box.

When the reguired X movement has been achieved the Y movement is commenced by switching-off the supply of pressure to valve 19 using valve 14, as described above, moving the spool 136 to the Y-null position in which spool 145 bridges feed passage 135, switching-on the supply of pressure to valve 19 using valve 14 and achieving the required movement in direction Y by displacing spool 136 to the left or right of the Y-null position (i.e. to figure 4c or 4d).

When selection of first gear is completed the clutch is re-engaged in a progressive manner under the control of control unit 16. This is achieved by moving spool 36 to the figure 3b position in which the rate of re-engagement of the clutch is controlled by the flow along the drain path D. When the clutch is completely re-engaged (i.e. actuator completely drained) valve 14 is placed in its switched-off condition which in turn cuts-off the flow of pressurised fluid to valve 19. The gear selection and clutch engagement sequences is then completed by switching-off solenoid 19a.

If the control unit 16 determines that a ratio change from first to, for example, second gear is required the following sequence takes place.

Initially valve 19 has its spool 136 moved to the X-null position (figure 4f) and valve 14 is moved to the position in which the clutch is being disengaged (i.e. with the spool positioned to the right of that shown in figure 3c in order to pressurise actuator 18).

Whilst the clutch is being disengaged a small adjustment in the X direction of the position of the selector mechanism is made by small movements from the X-null position to ensure that the selector mechanism is centrally positioned in the plane of movement of the selector mechanism containing ratios 1 and 2. (i.e. plane A of figure 2).

When the clutch is disengaged valve 19 is switched-off using valve 14 and the spool 136 moved to the Y-null position. Valve 14 is then switched to the clutch null position shown in figure 3c to maintain the clutch disengagement and movements of spool 136 made from the Y- null position to effect the necessary movement in the Y direction to move from first to second ratio selection position.

When the selection of second gear ratio is completed valve 14 is moved to the figure 3b position to achieve a controlled re-engagement of the clutch under the control of unit 16.

When the clutch is re-engaged valve 14 is switched-off which in turn switches-off the flow of fluid to valve 19 which is then in turn switched-off.

It will be seen from the above description that the control system is capable of using valve 14 for controlling the engagement and disengagement movement of clutch actuator 18 and also for controlling the supply of pressurised fluid to ratio selector valve 19. By a combination of movements of the spools 36 and 136 of valves 14 and 19 operation of actuators 20 and 21 is controlled to effect the desired gear ratio selection. Although in the system described above only two spool- type solenoid-operated valves are used, the system could be modified so that valve 14 is replaced by two separate valves one of which controls the flow of fluid to and from clutch actuator 18 the other which controls the flow of fluid to valve 19 and the rod ends of actuators 20 and 21.

Similarly the valve 14 could operate with two separate valves one of which controls the flow of fluid to the head end of actuator 20 and the other which controls the flow of fluid to head end of actuator 21.

Each of the above suggested modified systems would this thus consist of three valves and not the two valves of the present invention.

Claims

1. A clutch and transmission ratio control system in which a main solenoid-operated valve distributes pressurised fluid to a clutch actuator or a ratio selector valve in response to signals from an electronic control means, the ratio selector valve in turn distributing pressurised fluid to a plurality of ratio selector actuators which control the movement of a plurality of ratio selector elements.

2. A system according to claim 1 in which the main solenoid operated valve is a spool valve in which a solenoid-operated spool controls the communication of pressurised fluid from an inlet port to a clutch actuator port, a drain port and a ratio selector valve port.

3. A system according to claim 2 in which the inlet port of the main solenoid operated valve is centrally located with the clutch actuator port and ratio selector valve port disposed one on each side of the inlet port and with the drain port located axially outwardly of the actuator port, the valve spool being provided with a number of axially spaced lands which are capable of isolating the inlet port from the other ports in one axial position of the spool, connecting the inlet port to the ratio selector valve port and the clutch actuator port to the drain port in a second axial position of the spool, and connecting the inlet port to the ratio selector valve port and controlling the flow of fluid to and from the clutch actuator port over a range of axial positions.

4. A system according to any one of claims 1 to 3 in which the ratio selector valve comprises a solenoid-operated spool valve in which a solenoid-operated spool controls communication between an inlet port connected with the main solenoid-operated valve, actuator ports each connected with a respective ratio selector actuator, and one or more drain ports.

5. A system according to claim 4 for use with two ratio selector actuators in which the inlet port of the ratio selector valve is centrally located with two actuator ports disposed one on each side of the inlet port and with a drain port located axially outwardly of each actuator port, the valve spool being provided with a central land which closes off the inlet port when the spool is in a central position and two outer lands one on each side of the central land which isolate each actuator port from the adjacent drain port in the central position of the spool, movement of the spool a first distance in one direction from the central position opening communication between the inlet and one actuator port around the central land and movement of the spool a further distance in said one direction closing off communication between the inlet and said one actuator port and opening communication between said one actuator port and the adjacent drain port around one of the outer lands, movement of the spool a first distance in the other direction from the central position opening communication between the inlet and the other actuator port around the central land and movement of the spool a further distance in said other direction closing of communication between the inlet and said other actuator port and opening communication between the other actuator port and the other drain port around the other outer land.

6. A system according to any one of claims 4 or 5 in which the main solenoid-operated valve is replaced by two separate solenoid-operated valves one of which controls the flow of fluid to and from the clutch actuator and the other of which controls the flow of fluid to the ratio selector valve.

7. A system according to any one of claims 1 to 3 in which the ratio selector valve is replaced by two separate solenoid-operated valves which control the flow of fluid to separate ratio selector actuators.

8. A clutch and transmission control system constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.