GB2369657A

GB2369657A - Automatic transmission hydraulic actuation system with separate gear engagement control valves

Info

Publication number: GB2369657A
Application number: GB0029453A
Authority: GB
Inventors: Graham Peter Romer
Original assignee: LuK Lamellen und Kupplungsbau GmbH
Current assignee: LuK Lamellen und Kupplungsbau GmbH
Priority date: 2000-12-02
Filing date: 2000-12-02
Publication date: 2002-06-05
Also published as: GB2373033A; ITMI20012531A1; GB0128679D0; GB0029453D0; GB2373033B; JP2002181188A; DE10149531A1

Abstract

A hydraulic actuation system for an automated transmission system having a clutch which is engaged via a clutch slave cylinder 22 operated under pressure from the system. A main control valve 120 which selectively connects the clutch cylinder 22, via a clutch control valve 122, and second working chambers 119 of gear engagement actuators 114, 115 to an accumulator 275 or to a reservoir 278. The clutch control valve 122 connects or isolates the clutch cylinder 22 to or from the main control valve 120. First gear engagement valves 144, 146 have an open position in which the first working chambers 118 of gear engagement actuators 114, 115 are connected to the accumulator 275 and a closed position in which the chambers 118 are isolated from the accumulator 275. Second gear engagement valves 145, 147 have an open position in which the second working chambers 119 of gear engagement actuators 114, 115 are connected to the main control valve 120 and a closed position in which the chambers 119 are isolated from the main control valve 120. Simple open/closed gear engagement valves 144-147 replaces more complex spool valves, thereby reducing overall system costs.

Description

HYDRAULIC ACTUATION SYSTEMS This invention relates to hydraulic actuation systems and in particular hydraulic actuation systems for automated transmission systems.

In automated transmission systems of, for example, the type disclosed in W097/05410 ; W097/40300 : GBOO05186. 2; GB0024999. 5 or GB0025000. 1, whose content is expressly incorporated in the disclosure content of the present application, fluid pressure actuators are used to control actuation of a clutch actuator mechanism and/or a gear engaging mechanism.

In such systems solenoid control valves are used to control flow of fluid to and from the fluid pressure actuators, so as to control actuation of the clutch and the gear engagement mechanism.

With increasing sophistication of such systems, three or four proportional flow control valves are typically used to control the system. These control valves are normally spool valves having multiple lands and ports. Moreover the valves must be controlled typically to move between three or four positions. These valves are as a consequence relatively expensive and require complex electronic control systems, which adds considerably to the overall cost of the hydraulic actuation system.

The present invention provides a simplified hydraulic actuation system with a view to reducing the cost and complexity of the system.

According to one aspect of the present a hydraulic actuation system for an automated transmission system comprises: a source of hydraulic fluid under pressure; a hydraulic fluid reservoir;

a hydraulic clutch actuator for controlling engagement of a clutch, said hydraulic clutch actuator comprising a single acting ram with a single working chamber; a hydraulic gear engagement actuator for controlling engagement of a gear, said hydraulic gear engagement actuator comprising a double acting ram having a piston defining first and second working chambers the working area of the piston open to the first working chamber being smaller than that open to the second working chamber; a main control valve, the main control valve being switchable between a first position in which the clutch actuator and the second working chamber of the gear engagement actuator are connected to the source of fluid under pressure and a second position in which the clutch actuator and the second working chamber of the gear engagement actuator are connected to the reservoir ; the working chamber of the clutch actuator being connected to the main control valve via a clutch control valve, the clutch control valve being switchable between an open position in which the working chamber of the clutch actuator is connected to the main control valve and a closed position in which the working chamber of the clutch actuator is isolated from the main control valve ; the first working chamber of the gear engagement actuator being connected to the source of hydraulic fluid under pressure via a first gear engagement control valve, the first gear engagement control valve being switchable between an open position in which the first working chamber of the gear engagement actuator is connected to the source of hydraulic fluid under pressure and a closed position in which the first working chamber of the of the gear engagement actuator is isolated from the source of hydraulic fluid under pressure; and the second working chamber of the gear engagement actuator being connected to the main control valve via a second gear engagement control valve, the second gear engagement control valve being switch able between an open position in which the second working chamber of the gear

engagement actuator is connected to the main control valve and a closed position in which the second working chamber of the of the gear engagement actuator is isolated from the main control valve.

The hydraulic actuating system described above replaces the complex proportional flow control valves used hitherto with simple two position solenoid control valves. Even though this may entail the use of more valves, this will nethertheless reduce to overall cost of the system and significantly simplify the electronic control system required to control the valves.

According to a preferred embodiment of the invention a pair of gear engagement actuators are used, a select actuator to control movement of a selector mechanism in a first"select"direction and a shift actuator to control movement of the selector mechanism in a second"shift"direction. Each of the select and shift actuators are provided with first and second gear engagement control valves.

The invention is now described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically a semi-automated transmission system utilising a hydraulic actuation system in accordance with the present invention; Figure 2 shows a gear selector mechanism and associated selector gate of the transmission system illustrated in Fig. 1; Figure 3 illustrates diagrammatically the hydraulic actuation system of the transmission system illustrated in Fig. 1; and Figure 4 shows plots of the condition of the various valves, the clutch engagement and the gear engagement, for typical gear changes from first

gear to second gear and from second gear to third gear, using the hydraulic actuation system illustrated in figure 3.

Fig. 1 of the accompanying drawings shows an engine 10 with a starter and associated starter circuit 10a which is coupled through the main drive friction clutch 14 to a multi-speed synchromeshed lay shaft-type gearbox 12, via a gearbox input shaft 15. Fuel is supplied to the engine by a throttle 16 which includes a throttle valve 18, operated by accelerator pedal 19. The invention is equally applicable to electronic or mechanical fuel injection petrol or diesel engine.

The clutch 14 is actuated by a release fork 20 which is operated by a hydraulic slave cylinder 22 in the form of a single acting ram with a single working chamber 23, under the control of a clutch actuator control means 38.

A gear selector lever 24 operates in a gate 50 having two limbs 51 and 52 joined by a cross track 53 extending between the end of limb 52 and intermediate of the ends of limb 51. The gate 50 defines five positions;"R" at the end of limb 52;"N"intermediate of the ends of the cross track 53; "S"at the junction of limb 51 with the cross track 53; and"+"and"-"at the extremities of limb 51. In limb 51 the lever 24 is biased to the central "S"position. The"N"position of the selector lever 24 corresponds to neutral ; "R"corresponds to selection of reverse gear ;"S"corresponds to selection of a forward drive mode; momentary movement of the lever to the "+"position provides a command to cause the gearbox to shift up one gear ratio; and momentary movement of the gear lever 24 to the"-"position provides a command to cause the gearbox to shift down one gear ratio.

The positions of the lever 24 are sensed by a series of sensors, for example micro switches or optical sensors, positioned around the gate 50. Signals from the sensors are fed to an electronic control unit 36. An output from

the control unit 36 controls a gear engaging mechanism 25, which engages the gear ratios of the gearbox 12, in accordance with movement of the selector lever 24 by the vehicle operator.

In addition to signals from the gear selector lever 24, the control unit 36 receives signals from: sensor 1 9a indicative of the degree of depression of the accelerator pedal 19; sensor 30 indicative of the degree of opening of the throttle control valve 18; sensor 26 indicative of the engine speed; sensor 42 indicative of the speed of the clutch driven plate ; and sensor 34 indicative of the clutch slave cylinder position.

The control unit 36 utilises the signals from these sensors to control actuation of the clutch 14 during take-up from rest and gear changes, for example as described in patent specifications EP0038113, EP0043660, EPO059035, EP0101220 and WO92/13208 whose content is expressly incorporated in the disclosure content of the present application.

In addition to the above mentioned sensors, control unit 36 also receives signals from a vehicle speed sensor 52, ignition switch 54 and brake switch 56 associated with the main braking system, for example the footbrake 58 of the vehicle.

A buzzer 50 is connected to the control unit 36 to warn/indicate to the vehicle operator as certain operating conditions occur. In addition or in place of the buzzer 50 a flashing warning light or other indicating means may be used. A gear indicator 60 is also provided to indicate the gear ratio selected.

As illustrated in Fig. 2, the gear engagement mechanism 25 comprises three shift rails 111, 11 2, 113 mounted parallel to one another for movement in an axial direction. Each shift rail 111, 112, 113 is associated with two of the gear ratios of the gearbox 12, via a selector fork and synchromesh unit in conventional manner, so that movement of the shift rails 111, 112, 113 in one axial direction will cause engagement of one of the associated gear ratios and axial movement of the shift rail 111, 112, 113 in the opposite axial direction will cause engagement of the other associated gear ratio.

Typically ; first and second gear ratios are associated with shift rail 111, so that axial movement of the shift rail 111 in a first direction will engage first gear or axial movement of shift rail 111 in a second direction will engage second gear; third and fourth gear ratios are associated with shift rail 112, so that axial movement of shift rail 112 in the first direction will engage third gear or axial movement of shift 112 in a second direction will engage fourth gear; and fifth and reverse gear ratios are associated with shift rail 113, so that axial movement of shift rail 113 in the first direction will engage fifth gear while axial movement of shift rail 113 in the second direction will engage reverse gear.

A selector member 110 is mounted for movement in a select direction X transverse to the axes of the shift rails 111, 112, 113 and in a shift direction Y, for movement axially of the shift rails 111, 112 and 113. The selector member 110 may thus be moved in direction X along a neutral plane A-B, so that it may be indexed with and engaged a selected one of the shift rails 111, 112 and 113. The selector member 110 may then be moved in direction Y to move the engaged shift rail 111, 1 12, 11 3 axially in either direction to engage one of the gear ratios associated therewith.

As illustrated in Fig. 3, selector member 110 is movable in the select direction X by means of a fluid pressure operated select actuator 114, along the neutral plane A-B of the gate illustrated in Fig. 2, to align the selector

member 110 with one of the shift rails 111, 112, 113, and thereby select a pair of gears associated with that shift rail. The selector member 110 may then be moved in the shift direction Y by means of a fluid pressure operated shift actuator 115, to move the shift rail 111,112, 113 axially in either direction to engage one of the gear ratios associated therewith.

The actuators 114 and 115 each comprise a double-acting ram having pistons 116,117 respectively, which divide the actuators 114,115 into two working chambers 118,119, the working chambers 118,119 being disposed on opposite sides of each of the pistons 116,117. Operating rods 114a, 115a extend from one side of the pistons 116,117 respectively and are operatively connected with the selector member 110 for movement thereof in the select and shift directions X and Y respectively. As a consequence of the connection of operating rods 114a, 115a to the pistons 116, 117, the working area of pistons 116,117 exposed to working chamber 118 is smaller than the working area of pistons 116, 117 exposed to working chamber 119.

A main solenoid control valve 120 comprises a two way valve having an inlet 138, an outlet 140 and a port 142. The inlet 138 of the main control valve 120 is connected to a source of hydraulic fluid under pressure, in the form of an accumulator 275. An electrically driven positive displacement pump 223 is provided to charge the accumulator 275, via a non-return valve 276. A pressure transducer 280 measures the pressure in the accumulator 275 and, via control unit 36, controls the electrically driven pump 223 to maintain the pressure in the accumulator at an appropriate level. The outlet 140 from the main control valve 120 is connected to a reservoir 278. When the solenoid 120a of the main control valve 120 is de-energised, the valve 120 connects the outlet 140 to the port 142, the valve 120 connecting the inlet 138 to the port 142 when the solenoid 120a is energised.

The working chamber 23 of the clutch slave cylinder 22 is connected to port 142 of the main control valve 120, via a solenoid clutch control valve 122.

The clutch control valve 122 opens the working chamber 23 to port 142, when solenoid 122a of the clutch control valve is de-energised and isolates the working chamber 23 from port 142 of the main control valve 120 when solenoid 122a is energised.

The working chambers 118 of the select and shift actuators 114, 115 are connected directly to the accumulator 275 by solenoid valves 144,146 respectively.

The working chambers 11 9 of the select and shift actuators 114, 11 5 are connected to port 142 of the main control valve 120 by solenoid valves 145, 147 respectively.

The solenoid valves 144,145, 146 and 147 when de-energised are closed, isolating the working chambers 118 from the accumulator 275 and the working chambers 119 from port 142 of the main control valve 120; and when energised are open, connecting the working chambers 18 to the accumulator 275 and the working chambers 119 to port 142 of the main control valve 120.

When the transmission is in gear and the clutch 14 is engaged, the main control valve 120, clutch control valve 122 and gear control valves 144,145, 146 and 147 are all de-energised. In this condition the working chamber 23 of clutch slave cylinder 22 is connected to reservoir 278 via valves 122 and 120, so that the clutch 14 is engaged. The working chambers 118, 119 of the select and shift actuators 114, 115 are closed by valves 144,145, 146 and 147 providing a hydraulic lock which prevents movement of the select and shift actuators 114, 115.

When a gear change is initiated by, for example, the driver of the vehicle moving the gear selector lever 24 momentarily to the"+"position, or by automatic initiation, the main control valve 120 is energised, connecting the working chamber 23 of the clutch slave cylinder 22 to the accumulator 275, thereby applying hydraulic pressure thereto to disengage the clutch 14.

During this period the valves 144,145, 146 and 147 remain de-energised so that working chambers 118, 119 of the select and shift actuators 114, 115 remain closed.

When the clutch 14 is disengaged, solenoid valve 122 is energised, so that the connection between the working chamber 23 and the accumulator 275 is closed and the clutch 14 is clamped in the disengaged position. Upon disengagement and clamping of the clutch 14, solenoid valves 146 and 147 are energised and, depending on the gear currently engaged, the main control valve 120 is controlled to conect the working chamber 119 of the shift actuator 115 to the reservoir 278 or to the accumulator 275. Energisation of solenoid valves 146 and 147 with port 142 of the main control valve 120 connected to the reservoir 278 will create a pressure differential across piston 117 causing the rod 115a to move upwardly as illustrated in figure 3, while energisation of solenoid valves 146 and 147 with port 142 of the main control valve 120 connected to the accumulator 275 will apply even pressure to both sides of piston 117 but due to the area differential will cause the rod 11 5a to move downwardly as illustrated in figure 3. A position sensor in the form of a linear potentiometer 127 is associated with rod 11 5b and provides a signal indicative of the position of the piston 117.

The currently engaged gear may thereby be disengaged by movement of the shift actuator 115 from the position corresponding to the currently engaged gear to a position corresponding to the neutral plane A-B.

If the desired new gear is controlled by the same shift rail 111, 112, 113 as the gear disengaged, for example when changing from 1 st. to 2nd. , then the solenoid valves 146,147 may remain energised until actuator 115 has moved

past the position corresponding to the neutral plane A-B and to the position corresponding to the new gear. The solenoid valves 146, 147 are then de energised, so that the working chambers 118 and 119 are closed, clamping the select actuator 115 in the required position. If however the new gear is controlled by a different shift rail 111, 112, 113, for example when changing from 2nd. to 3rd., then when piston 117 reaches a position corresponding to the neutral plane A-B, the solenoid valves 146,147 of are de-energised, to clamp the selector member 110 in the neutral plane A-B. The solenoid valves 144,145 of the select actuator 114 are now be energised and the main control valve 120 controlled in the manner described above to move rod 114a in an appropriate direction to engage the shift rail 111, 112, 113 corresponding to the new gear desired.

Again a linear potentiometer 126 is associated with the select actuator 114, the potentiometer 126 providing a signal indicative of the position of the piston 116. When the piston 116 is in a position corresponding to the desired shift rail 111, 112, 113 both solenoids 144 and 145 are de-energised clamping of the select actuator 114 in the required position. Solenoid valves 146 and 147 may now be re-energised and the main control valve 120 controlled to engage the new gear, as described above.

When the new gear has been engaged solenoid valves 120 and 122 may be de-energised connecting the working chamber 23 of clutch slave cylinder 22 to the reservoir 278 and allowing the clutch 14 to re-engage. The rate at which the clutch is re-engaged may be controlled to provide smooth take-up of drive, for example as described in EP0038113 ; EP0043660 ; EP0059035 ; Et0101220 or W092/13208, by rapidly switching between the energised and de-energised states of solenoid valve 120.

According to a preferred embodiment of the invention, the positions of the select and shift actuators 114, 115 for each of the gear ratios and the neutral plane A-B are calibrated and the potentiometers 126 and 127 are used in a

closed loop control circuit, to control the main control valve 120 and valves 144, 145, 146 and 147, to move the pistons 116 and 117 of the select and shift actuators 114, 115 to predetermined positions, in order to disengage the currently selected gear and engage the new gear.

Figure 4 shows typical gear changes from first gear to second and from second gear to third gear.

As illustrated in figure 4, initially the vehicle is in first gear with the clutch engaged. In this condition the main control valve 120 and valves 122,144, 145,146 and 147 are de-energised connecting the clutch slave cylinder to reservoir and clamping the select and shift actuators 114, 115 in a position corresponding to first gear.

Upon initiation of a change from first gear to second gear at time to, the main control valve 120 is energised to connect the clutch slave cylinder to the accumulator 275, thereby disengaging the clutch 14.

When the clutch 14 is disengaged at time ti, valve 122 is energised to clamp the clutch 14 in its disengaged position. Valves 146 and 147 are also energised, applying pressure to both sides of piston 117, causing rod 11 5a to move downwardly as illustrated in figure 3, causing shift rail 111 to disengage first gear and engage second gear.

When second gear is engaged at time t2, valves 146 and 147 are deenergised to clamp the select and shift actuators 114, 115 in a position corresponding to second gear. The main control valve 120 and valve 122 are then de-energised, connecting the clutch slave cylinder 22 to the reservoir 278, so that the clutch 14 re-engages, the clutch becoming fully engaged at time t3.

Upon initiation of a change from second gear to third gear at time t4 the main control valve 120 is energised to connect the clutch slave cylinder 22 to the accumulator 275, to disengage the clutch 14.

When at time t5 the clutch is disengaged, valve 122 is energised to clamp the clutch 14 in its disengaged position. The main control valve 120 and valves 146 and 147 are then energised to connect working chamber 118 of select actuator 115 to accumulator 275 and working chamber 119 to reservoir 278, thereby causing rod 11 5a to move upwardly and shift rail 111 to disengage second gear.

At time t6 when second gear is disengaged and the selector member 110 is aligned with the neutral plane A-B, valves 146 and 147 are de-energised to clamp the shift actuator 115 in a position corresponding to the neutral plane A-B. The main control valve 120 and valves 144 and 145 are then energised to apply pressure to both sided of piston 116 of the select actuator 114, thereby causing rod 114a to move to the right as illustrated in figure 3.

When at time t7, the selector member 110 is aligned with shift rail 112, valves 144 and 145 are de-energised to clamp the select actuator 114. The main control valve 120 is then de-energised and valves 146 and 147 energised to move shift rail 112, to engage third gear.

When third gear is engaged at time ts, valves 146 and 147 are de-energised to clamp the select actuator 115. Valve 122 is then de-energised to reconnect the clutch slave cylinder 22 to the reservoir 278 and allow the clutch to re-engage.

According to a preferred embodiment of the invention the main control valve 120, the solenoid valves 122, 144, 145, 146 and 147, and/or the cylinders of the select and shift actuators 114, 115, may be defined by a common

housing, the bores/cylinders of the various components being appropriately inter-connected by passages through the common housing. The valve/actuator pack so formed would be mounted on or adjacent the gearbox 12.

The electrically driven pump 223, accumulator 275, reservoir 278 and control unit 36 may also be mounted with the valve/actuator pack or may be mounted remotely thereof and inter-connected thereto by, for example, elastomeric pressure hoses.

Various modifications may be made without departing from the invention.

For example, while in the above embodiment the hydraulic circuit has been described with reference to a semi-automated transmission system, the invention is equally applicable to fully-automated transmission systems or to automated manual transmission systems.

Moreover while in the embodiment described above the clutch slave cylinder 22 is connected directly to the main control valve 120 a remote displacement valve with position sensing means of the type disclosed in EP 0702760 whose content is expressly incorporated in the disclosure content of the present application, may be interposed between the main control valve 120 and clutch slave cylinder 22.

The patent claims submitted with the application are proposed formulations without prejudice to the achievement of further patent protection. The applicant reserves the right to submit claims for further combinations of characteristics, previously only disclosed in the description and/or drawings.

References back used in sub-claims refer to the further development of the subject of the main claim by the characteristics of the respective sub-claim ; they are not to be understood as a waiver with regard to achieving

independent item protection for the combination of characteristics in the related sub-claims. Since the subject of the sub-claims can form separate and independent inventions with reference to the prior art on the priority date, the applicant reserves the right to make them the subject of independent claims or of division declarations. Furthermore, they may also contain independent inventions which demonstrate a design which is independent of one of the objects of the preceding sub-claims.

The embodiments are not to be considered a restriction of the invention.

Rather, a wide range of amendments and modifications is possible within the scope of the current disclosure, especially those variations, elements and combinations and/or materials which, for example, the expert can learn by combining individual ones together with those in the general description and embodiments in addition to characteristics and/or elements or process stages described in the claims and contained in the drawings with the aim of solving a task thus leading to a new object or new process stages or sequences of process stages via combinable characteristics, even where they concern manufacturing, testing and work processes.

Claims

CLAIMS 1. A hydraulic actuation system for an automated transmission system comprising: a source of hydraulic fluid under pressure; a hydraulic fluid reservoir; a hydraulic clutch actuator for controlling engagement of a clutch, said hydraulic clutch actuator comprising a single acting ram with a single working chamber; a hydraulic gear engagement actuator for controlling engagement of a gear, said hydraulic gear engagement actuator comprising a double acting ram having a piston defining first and second working chambers the working area of the piston open to the first working chamber being smaller than that open to the second working chamber; a main control valve, the main control valve being switchable between a first position in which the clutch actuator and the second working chamber of the gear engagement actuator are connected to the source of fluid under pressure and a second position in which the clutch actuator and the second working chamber of the gear engagement actuator are connected to the reservoir; the working chamber of the clutch actuator being connected to the main control valve via a clutch control valve, the clutch control valve being switchable between an open position in which the working chamber of the clutch actuator is connected to the main control valve and a closed position in which the working chamber of the clutch actuator is isolated from the main control valve ; the first working chamber of the gear engagement actuator being connected to the source of hydraulic fluid under pressure via a first gear engagement control valve, the first gear engagement control valve being switchable between an open position in which the first working chamber of the gear engagement actuator is connected to the source of hydraulic fluid under pressure and a closed position in which the first working chamber of

the of the gear engagement actuator is isolated from the source of hydraulic fluid under pressure ; and the second working chamber of the gear engagement actuator being connected to the main control valve via a second gear engagement control valve, the second gear engagement control valve being switchable between an open position in which the second working chamber of the gear engagement actuator is connected to the main control valve and a closed position in which the second working chamber of the of the gear engagement actuator is isolated from the main control valve.
2. A hydraulic actuation system according claim 1 in which the main control valve is in its second position when the solenoid is de-energised.
3. A hydraulic actuation system according claim 1 or 2 in which the clutch control valve is in its open position when the solenoid is de-energised.
4. A hydraulic actuation system according claim 1 in which the first and second gear control valves are in their closed positions when the solenoids are de-energised.
5. A hydraulic actuation system according any one of the preceding claims in which the gear engagement mechanism includes two gear engagement actuators, a select actuator for moving a selector member in a first direction and a shift actuator for moving the selector member in a second direction, the working chambers of the select and shift actuators each having first and second gear control valves.
6. A hydraulic actuation system according to any one of the preceding claims in which a plurality of the components are defined by a common housing, the components being interconnected with one another in appropriate manner by passageways formed in the common housing.
7. A hydraulic actuation system substantially as described herein with reference to and as shown in Figs. 1 to 4 of the accompanying drawings.
8. An automated transmission system including a hydraulic actuation system as claimed in any one of claims 1 to 7.