GB2379251A

GB2379251A - Shift drum actuator

Info

Publication number: GB2379251A
Application number: GB0121350A
Authority: GB
Inventors: Bernhard Boll; Y K Park
Original assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG; LuK Lamellen und Kupplungsbau GmbH
Current assignee: Schaeffler Buehl Verwaltungs GmbH; LuK Lamellen und Kupplungsbau GmbH
Priority date: 2001-09-04
Filing date: 2001-09-04
Publication date: 2003-03-05
Also published as: DE10294281D2; GB0121350D0; FR2829215A1; DE10240259A1; ITMI20021880A1; FR2829215B1; WO2003025435A1

Abstract

A shift drum actuator 10 has a hydraulic rotary drive positioned concentrically within the shift drum 12, the shift drum 12 mounted for rotation of a shaft 30. The hydraulic rotary drive has a cylinder 20, the shaft 30 is mounted coaxially with the cylinder 20 and is rotatable relative to the cylinder 20. The external diameter of the shaft 30 is smaller than the internal diameter of the cylinder 20 and the ends of the cylinder 20 are closed to form an annular fluid tight chamber 36. An axial vane 54 on the shaft 30 extends into a sealing engagement with the internal diameter of the cylinder 20 and an axial vane 50 on the internal diameter of the cylinder 20 extends into a sealing engagement with the external diameter of the shaft 30. The vanes 50,54 divide the annular chamber 36 into two fluid tight compartments 62,64. Fluid ports 66,68 provide access for hydraulic fluid into and out of the compartments 62,64. Controlling the flow of the hydraulic fluid controls the rotation of the shift drum 12 which causes shift forks (116,117,118 Fig 3) to move in grooves (110,111,112 Fig 3) to allow gear selection.

Description

GEAR ACTUATORS The present invention relates to gear engagement actuators and in particular shift drum actuators for control of a gear selector mechanism of an automated transmission system of a motor vehicle.

Hitherto shift drum actuators for the automated transmission systems of motor vehicles, for example as disclosed in GB2308874 and GB2311 829 the disclosures of which explicit reference is made and whose content is expressly incorporated in the disclosure content of the present application, have utilised electric motors with high reduction gear mechanisms to drive the shift drum. In one particular form the electric motor drives the shift drum through a worm gear mechanism. This presents particular problems with regard to packaging restraints in the system.

Moreover, for example, as disclosed in GB2354295; GB2308413 ; and GB2358443; the disclosures of which explicit reference is made and whose content is expressly incorporated in the disclosure content of the present application, automated transmission systems commonly utilise hydraulic control systems to control clutch actuation and gear engagement actuation. In such systems it is desirable that both clutch and gear actuation be achieved by hydraulic means using an integrated hydraulic control circuit and consequently linear hydraulic actuators rather than electrically driven shift drums have been used in such systems.

The present invention provides a compact shift drum actuator which is hydraulically driven.

According to one aspect of the present invention a gear engagement actuator comprises a shift drum, the shift drum defining on its outer periphery at least one annular track and a hydraulic rotary drive, the hydraulic rotary drive being formed concentrically within the shift drum, the hydraulic rotary drive comprising

a cylinder, a shaft mounted coaxially of the cylinder, the external diameter of the shaft being smaller than the internal diameter of the cylinder and the ends of the cylinder being closed to define an annular fluid-tight chamber, an axial vane formation on the shaft extending radially into sealing engagement with the internal diameter of the cylinder and an axial vane formation on the internal diameter of the cylinder extending radially into sealing engagement with the external diameter of the shaft in order to divide the annular chamber into two fluid-tight compartments, fluid ports being provided for introduction of hydraulic fluid into and exhaust of hydraulic fluid from each of the compartments, one of the cylinder and shaft constituting a stator and the other of the cylinder and shaft constituting a rotor, the rotor being rotatable with respect to the stator, the stator being attached to a support element and the rotor being drivingly connected to the shift drum.

An embodiment of the invention is now described by way of example only, with reference to the accompanying drawings in which :- Figure 1 shows a sectional side elevation of a gear engagement actuator in accordance with the present invention; Figure 2 is a section along the line ll-ll of Fig. 1; Figure 3 shows diagramatically a multi-ratio gearbox utilising a gear engagement actuator in accordance with the present invention; Figure 4 shows a projection of the tracks of the shift drum illustrated in figure 3; Figure 5 shows diagramatically a hydraulic control circuit for an automated transmission system utilising the gear engagement actuator in accordance with the present invention; and

Figure 6 shows a double shift drum actuator in accordance with the present invention.

As illustrated in Figs. 1 and 2 a gear engagement actuator 10 comprises a shift drum 12 defining an annular track 14 in its outer periphery.

A cylinder 20 having a closed end 22 is secured at its closed end to a connector plate 24. The opposite end of the cylinder 20 is closed by means of end plate 26 which is secured and sealed to the cylinder 20 in suitable manner. A shaft 30 is rotatably mounted coaxially of the cylinder 20 in rolling bearings 32,34 in the closed end 22 and end plate 26 respectively. The shaft 30 extends through the end plate 26 and is sealed with respect thereto to produce an annular fluidtight chamber 36 between the shaft 30 and cylinder 20.

The end of the shaft 30 extending through end plate 26 has a flange formation 38. The shift drum 12 is secured to the flange formation 38 by means of angularly spaced screws 40 or other suitable fastening means, so as to be rotatable with the shaft 30. The shift drum 12 is secured to flange formation 38 adjacent one end and extends coaxially of the cylinder 20 towards the connector plate 24. An axial bearing 42 is provided between the connector plate 24 and adjacent end of the shift drum 12.

An end support 44 defining a spigot formation 46 by which the shift drum 12 may be supported on, for example a gearbox or clutch housing, is mounted at the opposite end of the shift drum 12 by means of a rolling bearing 48.

A first axially extending vane formation 50 is secured to the inner periphery of the cylinder 20 by means of screws 52. The vane formation 50 extends radially towards the shaft 30. A second axially extending vane formation 54 is secured to the external diameter of shaft 30 by means of screws 56. The vane formation 54 extends radially towards the internal diameter of the cylinder 20.

Sealing tips 60 are provided on the vane formation 50 for sealing engagement of

the shaft 30, closed end 22 of the cylinder 20 and end plate 26, and on the vane formation 54 for sealing engagement of the internal diameter, closed end 22 and end plate 26 of the cylinder 20, thereby dividing the annular chamber 36 into two fluid-tight compartments 62,64.

Bores 66,68 are provided through connector plate 26 and the closed end 22 of cylinder 20, the bores 66,68 opening to compartments 62,64, one on either side of and adjacent the vane 50. Stop means (not shown) is provided for limiting rotation of shaft 30, so that the vane 54 does not pass or obscure the bores 66,68.

As illustrated diagrammatically in Fig. 3, the transmission system of a motor vehicle comprises a gearbox 70. An input shaft 72 of the gearbox 70 is connected to the output shaft 74 of an engine 76, via a friction clutch 78. The clutch 78 is of conventional design comprising a driven plate 80, which is mounted for rotation with the input shaft 72 of the gearbox 70, the driven plate 80 being adapted to selectively frictionally engage a flywheel 82 mounted for rotation with the output shaft 74 of the engine 76.

A clutch slave cylinder 222 is provided for engagement and disengagement of clutch 78.

An output shaft 84 from the gearbox 70 is mounted parallel to the input shaft 72. A series of gears 85 to 90 are mounted on the input shaft 72 for rotation therewith. A corresponding series of gears 95 to 100 are mounted on the output shaft 84 for rotation relative thereto. Gears 85 to 89 and gears 95 to 99 are arranged in intermeshing pairs and are sized to provide different gear ratios; gears 85 and 95 providing a fifth gear ratio; gears 86 and 96 providing a fourth gear ratio; gears 87 and 97 providing a third gear ratio; gears 88 and 98 providing a second gear ratio; and gears 89 and 99 providing a first gear ratio.

A further gear 102 meshes between gears 90 and 100 to reverse the direction of rotation and provide a reverse gear ratio.

Synchromesh units 104,105, 106, are provided between the gears 99 and 100; 97 and 98; and 95 and 96, respectively. Axial movement of the synchromesh unit 104 to the left as illustrated in Fig. 3 will thereby rotatably secure gear 99 to the output shaft 84, while axial movement of synchromesh unit 104 to the right will rotatably secure gear 100 to the output shaft 84.

Likewise, axial movement of synchromesh unit 105 will selectively rotatably secure gear 97 or gear 98 to the output shaft 84 and axial movement of the synchromesh unit 106 will selectively rotatably secure gear 95 or gear 96 to the output shaft 84.

Speed sensors 107 and 108 are provided for monitoring the speed of rotation of the gearbox input shaft 72 and output shaft 84 and providing signals proportional thereto which are sent to an electronic control unit.

The shift drum actuator 10 is mounted within the gearbox housing, parallel to input and output shafts 72, 84. The shift drum 12 has three circumferential groves in its outer periphery, defining tracks 110,111 and 112. As illustrated in figure 4, each track 110,111, 112, has an annular portion 113, a first divergent portion 114 diverging to one side of the annular portion 113 and a second divergent portion 115 diverging to the other side of the annular portion 113. The divergent portions 114 and 115 of each track 110, 111, 112 are offset angularly from those of the other tracks 110,111, 112.

Three shift forks 116,117, 118 are slidably mounted on rail 119 for movement parallel to the axis of rotation of the shift drum 1 2 and input and output shafts 72,82. Shift fork 116 engages synchromesh unit 104 on one side and engages in the track 110 of the shift drum 12 on the other side; shift fork 117 engages synchromesh unit 105 on one side and engages in the track 111 of the shift drum 12 on the other side; and shift fork 118 engages synchromesh unit 106 on one side and engages in the track 112 of the shift drum 1 2 on the other side.

When the shift drum 12 is rotated, while the shift forks 116, 117, 118 engage the annular portions 113 of tracks 110, 111, 11 2 respectively, there will be no movement of the shift forks 116, 117 or 118 or the associated synchromesh units 104,105, 106 and the gears 95 to 100 will remain disengaged from output shaft 84. However when a shift fork 116, 117, 118 engages a divergent portion 114 or 1 1 5 of the track 11 0, 111, 11 2, the shift fork 116, 117, 118 will be moved axially of the output shaft 84, to one side or the other, thereby shifting the associated synchromesh unit 104,105, 106 and engaging one of the gears 95 to 100, associated therewith. As the divergent portions 114, 115 of the tracks 110, 111, 112 are offset angularly, only one gear 95 to 100 may be engaged with the output shaft at any time. A change from one gear to another may consequently be effected by disengaging the clutch 78 and rotating the shift drum 12, so that the currently engaged gear is disengaged and target gear engaged.

For example for a change from 1 gear to 2nd gear :- initially the shift drum 12 will be rotated to a position in which shift fork 116 engages divergent portion 114 of track 110, so that the shift fork 116 and synchromesh unit 104 is displaced to the left as illustrated in figure 3, thereby engaging gear 99 with the output shaft 84; upon disengagement of clutch 78, the shift drum 12 is rotated, so that the shift fork 116 engages the annular portion 113 of track 110, the shift fork 116 and synchromesh unit 104 thereby being moved to the central position and gear 99 being disengaged from output shaft 84, to disengage 1 sot gear; and the shift drum 1 2 being further rotated so that shift fork 117 engages the divergent portion 11 5 of track 111, thereby moving shift fork 11 7 and synchromesh unit 105 to the right to engage gear 98 with the output shaft 84 and engage 2nd gear.

With the transmission system disclosed above, when the vehicle is stationery with the gearbox in neutral, the synchromesh units 104,106. 108 will be at their mid-positions, so that all of the gears 95 to 100 will be rotatable relative to the output shaft 84. The clutch slave cylinder 222 will be de-energised so that clutch 18 is engaged. Consequently, even though clutch 78 is engaged, no drive will be transmitted to the output shaft 84.

As illustrated in Fig. 5, a hydraulic control circuit for an automated transmission system utilising a shift drum actuator as illustrated in figures 1 to 3 comprises a hydraulic accumulator 275 and a reservoir 278 for hydraulic fluid. An electrically-driven pump 223 is provided to charge the accumulator 275 via a non-return valve 276. A pressure transducer 282 is provided to measure the accumulator pressure and send signals corresponding thereto to the electronic control unit. A pressure release valve 280 is provided between the outlet from the pump 223 and a reservoir 278 to ensure that the pressure supplied by the pump 223 does not exceed a maximum predetermined value. The electric motor driven pump 223 is controlled by the electronic control unit, in response to the signals from the pressure transducer 282, in order to maintain the accumulator 275 at an appropriate pressure.

A solenoid operated main control valve 120 comprises a housing 122, defining a bore 124. A spool 126 is slidably located in the bore 124, the spool 126 having three axially spaced circumferential lands 128,130, 132 which sealingly engage the bore 124. A solenoid 134 acts on one end of the spool 126, so that upon energisation of the solenoid 134, the spool 126 is moved axially of the bore 124 against a load applied by a compression spring 136, acting on the opposite end of the spool 126.

An inlet 138 to the bore 124 of valve 120 is connected to the accumulator 275.

An outlet 140 from the bore 124 of the main control valve 120 is connected to the reservoir 278. A first port 142 from bore 124 is connected to working compartments 62 and 64 of the shift drum actuator 10 via a valve 144 and a second port 148 is connected to the clutch slave cylinder 222.

The valve 144 is a solenoid operated valve having a housing 150 defining a bore 151 with a spool 152 slideably mounted in the bore 151. The spool 152 has three axially spaced circumferential lands 154,156, 158, the lands sealingly engaging the bore 151. An axial bore 160 opens to end 162 of the spool 152 and connects to a cross-bore 164, the cross-bore 164 opening between lands 154 and 156 of the spool 152. A solenoid 166 acts on end 168 of spool 152 remote from the end 162, so that upon energisation of the solenoid 166, the spool 152 will move axially of the bore 151 against a load applied by a compression spring 170 acting on end 162 of the spool 152.

An inlet 172 to the bore 151 is connected to port 142 of the main control valve 120. An outlet 174 from the bore 151 is connected to the reservoir 278. A first port 176 opening to the bore 151 is connected one compartment 62 of actuator 10 and a second port 178 opening to the bore 151 is connected to the second compartment 64 of actuator 10.

When the transmission is in gear and the clutch engaged, the solenoids 1 34 and 166 will be de-energised and valves 120 and 144 will be in the rest positions illustrated in Fig. 4. In this position, the clutch slave cylinder 222 is connected via port 148 and outlet 140 of the main control valve 120 to the reservoir 278; the compartment 62 of actuator 10 will be connected to the reservoir 278 via port 176, passageways 164,160 and outlet 174 of valve 144; and compartment 64 of the actuator 10 will be connected to the reservoir 278 via port 178 and outlet 174 of the valve 144. There will consequently be no movement of the clutch slave cylinder 222 nor the actuator 10.

When a gear change is initiated by, for example, the driver of the vehicle moving a gear selector lever or by automatic initiation, solenoid 1 66 is energised to move spool 152 of valve 144 to a second position in which land 156 closes port 176 and land 158 closes port 178, thereby isolating compartments 62 and 64 from both the accumulator 275 and the reservoir 278 and hydraulically locking the actuator 10.

The solenoid 134 of the main control valve 120 is then energised to move the spool 126 of main control valve 120 to a second position. In this second position the main control valve connects the clutch slave cylinder 222 to accumulator 275 via port 148 and inlet 138 and inlet 172 of valve 144 to the accumulator 275, via port 142 and inlet 138. Hydraulic fluid under pressure is thus introduced into the clutch slave cylinder 222 causing the clutch 78 to disengage.

Upon disengagement of the clutch 78, solenoid 134 may be energised to move the main control valve back to a null position. In this null position, the port 148 is closed by land 132, isolating port 148 from the inlet 138 and the outlet 140, so that the clutch will be clamped in the disengaged position, port 142 of the main control valve 120 however remains connected to the accumulator 275.

The energising current to solenoid 166 of the valve 144 may then be reduced, moving the valve 144 to a third position, in which compartment 62 is connected to accumulator 275 via port 176 and inlet 172 of the valve 144 and port 142 and inlet 138 of main control valve 120 and compartment 64 is connected to the reservoir 278 via port 178 and outlet 174 of the valve 144, so that the pressure of fluid acting on vane 54 will cause the shaft 30 and shift drum 12 attached thereto to rotate in an anticlockwise direction; or increased to move spool 152 to a fourth position in which compartment 62 is connected to reservoir 278 via port 176, bores 164 and 160 and outlet 174 and compartment 64 is connected to the accumulator 275 via port 178 and inlet 172 of the valve 144 and port 142 and inlet 138 of main control valve 120, so

that the pressure of fluid acting on vane 54 will cause the shaft 30 and shift drum 12 attached thereto to rotate in a clockwise direction. By suitable control of valve 144 the shift drum 1 2 may be rotated to disengage the currently engaged gear and engage a target gear.

A position sensor 226 provides a signal indicative of the angular position of the shift drum 12. The position sensor 226 may be a linear potentiometer 228 which is mounted transverse to the axis of rotation of the shift drum 12. The linear potentiometer 228 having a plunger 230 which engages a spiral cam surface 232 on the shift drum 12, so that as the shift drum 12 rotates, the plunger 230 will move in and out of the potentiometer 228, to vary the voltage of the signal. Alternatively the position sensor 226 may be a rotary potentiometer which is rotated by rotation of the shift drum 12 to provide a voltage which varies with the angular position of the shift drum 1 2.

Signals from the position sensor 226 are fed to the electronic control unit to provide an indication of the position of the shift drum 1 2 corresponding to precalibrated positions corresponding to engagement of each of the gear ratios.

Measurements from the position sensor 226 may then be used by a closed loop control system to control valve 144, to move shift drum 12, to the predetermined positions to engage the desired gear ratios.

When the desired gear ratio has been engaged, the solenoid 166 of valve 144 is energised to move the valve 144 back to its null position, closing the ports 176 and 178 and creating a hydraulic lock preventing further movement of the actuators 10.

Solenoid 134 of the main control valve 120 may then be de-energised to move the main control valve 120 back to its rest position as illustrated in figure 5, thereby allowing fluid from the clutch slave cylinder 222 to be returned to the reservoir 278, permitting re-engagement of the clutch 78. The main control valve 120 may be switched between its rest and second positions, so that the

clutch 78 is re-engaged in controlled manner, for example as disclosed in EP0038113; EP0043660; EP0059035; EP01 01220 or W092/13208.

When the clutch 14 has been re-engaged, solenoid 134 of the master control valve 120 may be de-energised, so that it returns to the rest position illustrated in Figure 5. The solenoid 166 of the valve 144 may then be de-energised to release pressure from compartments 62 and 64 of the shift drum actuator.

While the use of a single shift drum as described above has cost advantages, for some gear changes it will be necessary to move through one or more gears in order to get to the target gear. This will slow down the gear change and will also have an adverse effect on the life of synchromesh units and gears. It may consequently be desirable to use more than one shift drum actuator in accordance with the present invention. More than one shift drum may also be required with gearboxes having greater numbers of gear ratios. Furthermore in twin clutch transmission systems of the type disclosed in co-pending UK Patent Applications GB 0028310 and GB 0103312 the disclosures of which explicit reference is made and whose content is expressly incorporated in the disclosure content of the present application, a double shift drum drive is desirable, one shift drum being arranged for control of gears in association with one clutch and a second shift drum being arranged for control of shifts in association with the other clutch.

Figure 6 illustrates a double shift drum actuator in which two actuators 10,10' as described above are mounted back to back on a common connector plate 24'.

The double shift drum actuator is preferably mounted inside a gearbox housing 300 parallel to the input and output shafts of the gearbox. The spigot formation 46 on the end support 44 of one shift drum actuator 10 engages a socket formation 302 on an internal surface of the gearbox housing 300, while spigot formation 46'of the other shift drum actuator 10'engages through a bore 304 in a clutch housing 306. A set screw 308 locates the double shift drum assembly axially and rotatably with respect to the clutch housing 306.

The double shift drum assembly described with reference to figure 6, may be controlled by a hydraulic circuit similar to that described with reference to figure 5, separate valves 144 being provided for the individual control of each shift drum actuator 10, 10'. However where the double shift drum is used in a twin clutch transmission system, the hydraulic control circuit will have two master control valves 120, one for control of each of the clutches, and the valve 144 for each actuator 10, 10'will be controlled by a different master control valve 120.

Various modifications may be made without departing from the invention. For example, in the embodiment described above, the shift drum 12 may be rotationally mounted on the cylinder 20 by means of rolling bearings.

Furthermore the shift drum may be compliantly mounted with respect to the shaft 30, for example by means of a resilient bush which is mounted, under compression, between the flange formation 38 and an internal diameter of the shift drum 12, in order to provide axial and/or radial compliance.

According to an alternative embodiment of the invention, the shaft 30 may form the stator, being non-rotationally mounted with respect to the connector plate 24, the cylinder 20 being mounted on the shaft 30 for rotation with respect thereto and the shift drum 12 being mounted for rotation with the cylinder 20.

According to a further embodiment, the cylinder 20 may be defined by the internal diameter of the shift drum 12.

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

1. A gear engagement actuator comprising a shift drum, the shift drum defining on its outer periphery at least one annular track and a hydraulic rotary drive, the hydraulic rotary drive being formed concentrically within the shift drum, the hydraulic rotary drive comprising a cylinder, a shaft mounted coaxially of the cylinder, the external diameter of the shaft being smaller than the internal diameter of the cylinder and the ends of the cylinder being closed to define an annular fluid-tight chamber, an axial vane formation on the shaft extending radially into sealing engagement with the internal diameter of the cylinder and an axial vane formation on the internal diameter of the cylinder extending radially into sealing engagement with the external diameter of the shaft in order to divide the annular chamber into two fluid-tight compartments, fluid ports being provided for introduction of hydraulic fluid into and exhaust of hydraulic fluid from each of the compartments, one of the cylinder and shaft constituting a stator and the other of the cylinder and shaft constituting a rotor, the rotor being rotatable with respect to the stator, the stator being attached to a support element and the rotor being drivingly connected to the shift drum.

2. A gear engagement actuator according to claim 1 in which the cylinder is mounted non-rotatably, the shaft being rotatable relative to the cylinder and the shift drum being mounted on the shaft for rotation therewith.

3. A gear engagement actuator according to claim 2 in which the cylinder is mounted on a connector plate which defines the fluid ports.

4. A gear engagement actuator according to claim 3 in which an axial bearing is provided between an end of the shift drum and the connector plate.

5. A gear engagement actuator according to any one of claims 2 to 4 in which the shift drum is mounted on a flange formation on the shaft.

6. A gear engagement actuator according to any one of claims 2 to 5 in which a support plate engages one end of the shift drum, the support plate being rotatably mounted with respect to the shift drum.

7. A gear engagement actuator according to claim 6 in which the support plate defines a spigot formation for engagement of a socket formation on a support structure.

8. A gear engagement actuator according to claim 1 in which the shaft is non-rotatably mounted, the cylinder is mounted for rotation on the shaft and the shift drum is mounted on the cylinder for rotation therewith.

9. A gear engagement actuator according to claim 8 in which the cylinder is defined by the internal diameter of the shift drum.

10. A gear engagement actuator according to any one of claims 1 to 9 in which the shift drum is compliantly mounted with respect to the rotor.

11. A gear engagement actuator substantially as described herein with reference to and as shown in figures 1 to 6 of the accompanying drawings.