GB2392967A - Motor driven leadscrew clutch actuator - Google Patents

Abstract

A cable 30 attaches to a driving plate 24. A clutch actuator 10 has an electric motor 40 which drives a leadscrew cylinder 50 which in turn axially moves the cable 30 via a leadscrew nut 60 to engage or disengage a clutch. In an alternative embodiment, an annular hydraulic slave cylinder (212, Figs 7-9) may be used instead of the cable 30 to actuate the clutch.

Description

1. CLUTCH ACTUATORS

The present invention relates to a clutch control system and in particular to an electric motor actuator for use in connection with a clutch release mechanism 5 which is mounted co-axially of a vehicle clutch.

UK Patent Specification Nos. GB2296550 and GB2338769 the disclosures of

which explicit reference is made and whose content is expressly incorporated in the disclosure content of the present application, disclose clutch release

10 mechanisms comprising a cam mechanism located co-axially of the clutch, rotation of the cam mechanism causing axial displacement of a release bearing, which bears against a diaphragm spring to control engagement and disengagement of the clutch. The cam mechanism is rotated by means of a cable. Typically the cable will be pulled and pushed by means of a remote 15 actuator mechanism.

Instead of the mechanical clutch release mechanism disclosed above the clutch may be controlled by a concentric hydraulic slave cylinder of the type disclosed in US4526258; US4637505; US6273231; US20010011626; US20010047918; or 20 GB2344395 the disclosures of which explicit reference is made and whose

content is expressly incorporated in the disclosure content of the present

application. Typically such concentric slave cylinders are controlled by means of a remote master cylinder of, for example, the type disclosed in GB2313885; GB2317933; GB2325036 or GB2309761, the disclosures of which explicit

25 reference is made and whose content is expressly incorporated in the disclosure

content of the present application. Such master cylinders are connected to the slave cylinder by means of metal pipes or pressure hoses.

Electric motor actuators which are used with the clutch release mechanisms 30 disclosed above, for example as disclosed in GB2325036; GB2313885 and GB2309761, typically utilise a worm and worm gear mechanism, to provide a high drive ratio reduction, in order to convert the high speed, relatively low torque drive

I r - 2 of the electric motor, into a slow speed relatively high torque required to actuate the clutch release mechanism.

Location of an electric motor actuation means, remote from the clutch release 5 mechanism, presents problems with regard to routing of cables or fluid lines and with regard to the compliance of the system. Furthermore, it is not possible to pre-

assemble, test and/or calibrate the system prior to assembly in the vehicle.

The present invention provides a clutch control system with a clutch actuation 10 means which may be pre-assembled with a clutch release mechanism on a common support structure, permitting pre-testing and calibration of the system, before it is assembled in the vehicle. In particular, the concentric clutch release mechanism and clutch actuator can be pre-assembled or may allow preassembly on a clutch housing. This places restraints on the clutch actuator in order to allow 15 it to be accommodated in the restricted space available.

In accordance with the present invention a clutch control system comprises a concentric clutch release mechanism and clutch actuator means mounted in close proximity to the concentric clutch release mechanism, the clutch actuator means 20 comprising an electric motor mounted radially of the clutch release mechanism, the electric motor being connected by a leadscrew and nut mechanism to actuating means for the clutch release mechanism.

Preferably, both clutch release mechanism and clutch actuator means are 25 mounted with respect to one another on a clutch housing, permitting pre-assembly and testing of the clutch release system prior to assembly of the system in the vehicle. According to one embodiment of the present invention, the clutch release 30 mechanism is a concentric cam arrangement having cable means to rotate the

cam mechanism, the leadscrew and nut mechanism being connected to the cable to control rotation of the cam mechanism.

According to an alternative embodiment of the invention, the clutch release 5 mechanism is a concentric hydraulic slave cylinder. The leadscrew and nut mechanism controlling movement of a piston of a master cylinder to provide hydraulic fluid under pressure to the slave cylinder. Preferably, the master cylinder is formed integrally of the slave cylinder, allowing the hydraulic system to be tested and calibrated on the bench.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates in sectional elevation a cable controlled clutch actuator and 15 release mechanism in accordance with the present invention; Figure 2 illustrates in sectional elevation an alternative form of cable controlled clutch actuator for actuation of the release mechanism illustrated in Figure 1; 20 Figure 3 illustrates in sectional elevation a further form of cable controlled clutch actuator for actuation of the release mechanism illustrated in Figure 1; Figure 4 shows a section along the line iv-iv of figure 3; 25 Figure 5 illustrates a modification to the clutch actuator illustrated in figure 3; Figure 6 illustrates a further modification to the clutch actuator illustrated in figure 3; 30 Figure 7 illustrates in sectional end elevation a hydraulic clutch actuator and a release mechanism in accordance with the present invention;

Figure 8 illustrates in sectional side elevation the clutch actuator and release mechanism along the line IV-IV of Figure 7; 5 Figure 9 illustrates the embodiment of Figures 7 and 8, in situ in the clutch housing of a motor vehicle; Figure 10 illustrates in sectional side elevation an alternative fomm of hydraulic clutch master cylinder for use with a clutch actuator and release mechanism of the 10 type illustrated in Figure 7.

Figure 11 illustrates in sectional side elevation a further alternative fomm of hydraulic clutch master cylinder for the clutch actuator and release mechanism illustrated in Figure 7; Figure 12 illustrates in sectional side elevation a further alternative fomm of hydraulic clutch master cylinder for the clutch actuator release mechanism illustrated in Figure 7; 20 Figure 13 illustrates in sectional side elevation a modification to the embodiment illustrated in figure 5; and Figure 14 shows a section along the line xiv-xiv of figure 13.

25 Figure 1 illustrates a clutch actuator 10 for use with a concentric mechanical clutch release mechanism 12 of the type disclosed in GB 2,296, 550 and GB 2,338,769.

Figure 1 is a view showing a section through a clutch housing 14, looking towards the vehicle engine, details of the clutch have however been omitted for clarity.

- 5 The clutch release mechanism 12 comprises a base plate 20 which is secured to the end of the clutch housing 14 adjacent the gearbox (not shown), by means of bolts passing through holes 22 in the base plate 20. The clutch release mechanism 12 is thereby mounted coaxially of the input shaft of the gearbox, 5 between the gearbox and the clutch. A driving plate 24 is mounted coaxially of the base plate 20 for rotation with respect thereto. The driving plate 24 has ramp formations (not shown) and corresponding ramp formations are provided on an annular driven member 26, which is again mounted coaxially of the base plate 20 for movement axially thereof. Rolling bearings are provided between the ramp 10 formations on the driving plate 24 and the driven member 26 so that rotational movement of the driving plate 24 will be translated into axial movement of the driven member 26. The driven member 26 engages a release bearing which in turn engages a diaphragm spring of the clutch so that axial movement of the driven member 26 will engage or disengage the clutch.

A cable 30 is connected to the driving plate 24 by which it may be rotated, a nipple 32 on the cable 30 engaging in an apertured nipple gripping arm on the driven plate 24. A segment shaped radial section 34 is attached to the driving plate 24, to provide a pulley which will guide the cable 30 to move in a plane parallel to that 20 of the driven plate 24.

The clutch actuator 10 comprises an electric motor 40 which is mounted at one end of an actuator housing 42, the actuator housing 42 locating through an aperture 44 in the clutch housing 14, the axis of the motor 40 being disposed in 25 the plane of rotation and tangential to the radial section 34.

The shaft 46 of the electric motor 40 is connected by a drive coupling 48 to a leadscrew cylinder 50. The leadscrew cylinder 50 is mounted in the housing 42 coaxially of the electric motor 40, a thrust roller bearing 52 being provided at the 30 end of the housing 42 adjacent the electric motor 40 and a radial support bearing 54 being provided adjacent the opposite end of housing 42.

- 6 A screw thread 56 is provided on the internal diameter of the leadscrew cylinder 50. A leadscrew 60 is located within the leadscrew cylinder 50, engaging the thread 56 thereof. The cable 30 passes through a central bore 62 in the 5 leadscrew 60, the end of the cable 30 having a nipple formation 64 for engagement of a counterboard formation 66 at the end of the bore 62, adjacent the electric motor 40. A cable guide and buffer end stop 70 and sealing boot 72 are provided at the end of the housing 42 remote from the electric motor 40, to permit movement of the cable 30 therethrough, whilst preventing ingress of 10 contaminants into the housing 42 or leakage of lubricants from the housing 42.

The cable 30 is of high torsional stiffness so that upon rotation of the electric motor 40 it will resist rotation of the leadscrew 60 and the leadscrew 60 will be driven axially of the leadscrew cylinder 50, to pull or push the cable 30, thereby rotating 15 the driving plate 24 in one direction or the other, depending on the direction of rotation of the motor 40. Compensation may be made in the software controlling actuation of the motor 40, for any twisting that does occur in the cable 30.

The arrangements disclosed above provide a compact arrangement which may 20 be fitted into the limited space available in the vicinity of the clutch housing 14 and which will overcome the problems of routing of cables and compliance due to stretching of long lengths of cable, where the clutch actuators are located in a position remote from the clutch housing 14.

25 Figure 2 shows an alternative form of clutch actuator for use with the clutch release mechanism 12 described with reference to Figure 1.

In the actuator illustrated in figure 2 a leadscrew 160 is mounted coaxially of an actuator housing 142, for movement axially thereof. The actuator housing 142 30 locates through an aperture in the clutch housing 14, the axis of the leadscrew 160 being disposed in the plane of rotation and tangentially of the radial section

- 7 34 of the clutch release mechanism 12. A flange formation 110 is secured to the inner end of the leadscrew 160, the flange fommation 110 extending into close proximity to the internal diameter of the actuator housing 142 and having a plurality of angularly spaced radial projections 112 which slidingly engage in 5 axially extending grooves 114 in the internal diameter of the actuator housing 142, to prevent rotation of the leadscrew 160. A compensating spring 116 acts between the inner end 118 of the actuator housing 142 and the flange fommation 110, to bias the leadscrew 160 away from the inner end 118 of the actuator housing 142.

An electric motor 140 is mounted at the outer end of the actuator housing 142, the axis of the electric motor 140 being parallel to but offset from the axis of the leadscrew 160. A gear 120 is mounted on shaft 146 of the electric motor 140.

Gear 120 meshes with an external gear ring 122 formed on the external diameter 15 of a leadscrew nut 150, which is mounted in the actuator housing 142, coaxially of the leadscrew 160, in rolling bearings 154. The leadscrew nut 150 is fixed axially of the actuator housing 142 and has an internal thread 156 which engages a corresponding thread 158 on the leadscrew 160. Consequently rotation of the leadscrew nut 150 upon rotation of the electric motor 140, will cause axial 20 displacement of the leadscrew 160.

A cable 130 extends through a central bore 162 in the leadscrew 160. The outer end of the bore 162 has a conical counterbore 166. A plurality of segmental conical jaws 180 are located in the counterbore 166 and are biased into the 25 counter bore166 by means of a biasing spring 182, acting between the outer ends of the conical jaws 180 and a cap formation 184 secured to the outer end of leadscrew 160. The conical jaws 180 have serrated internal diameters 186 which will grip the cable 130 with respect to the leadscrew 160, under the biasing force applied by the spring 182. Initially the conical jaws 180 are retained in a retracted 30 position by means of a pin or circlip 188, so that the free end of the cable 130 may be passed through the central bore 162 of the leadscrew 160 and past the conical

- 8 jaws 180. The pin or circlip 188 may then be removed to release the conical jaws 180 to clamp the cable 130, when the cable 130 has been pulled through the leadscrew 160 to the correct datum position.

5 A flexible boot 172 is provided at the inner end 118 of the housing 142, to permit movement of the cable 130 therethrough, and a flexible sleeve 174 is provided between the outer end of housing 142 and the cap formation 184 to accommodate axial movement of the leadscrew 160.

10 As with the previous embodiment, rotation of the electric motor 140 will cause axial movement of the leadscrew 160 to pull or push the cable 130, to release or reengage the clutch, as appropriate, depending on the direction of rotation of the electric motor 140.

15 When the clutch is engaged, the leadscrew 160 will be displaced to the right as illustrated in figure 2, so that the compensating spring 116 will be compressed.

Upon movement of the leadscrew 160 to the left to release the clutch, the load applied by the clutch release spring will first be opposed by the compensating spring 116, so as to assist the electric motor 140. Only after the load applied by 20 the clutch release spring balances that applied by the compensating spring 116 is the motor 140 put under load, in order to complete clutch disengagement. Upon reengagement of the clutch, the initial movement of the release mechanism 112 will be assisted by the clutch release spring and the motor 140 will only be loaded towards the fully engaged position of the clutch, when the load applied by the 25 compensation spring 116 is less than that applied by the clutch release spring.

Typically the point at which the loads applied by the clutch release spring and compensating spring are balanced will be about the mid-point of movement between the fully released and full engaged positions of the clutch. In this manner the maximum load required from the electric motor 140 will be effectively halved, 30 thereby permitting the use of a substantially smaller motor 140.

- 9 - In the embodiment illustrated in figures 3 and 4, a leadscrew 600 is mounted coaxially of an actuator housing 602 and is drivingly connected to an electric motor 604, the electric motor being mounted coaxially, at one end of housing 602.

The leadscrew 600 has an external thread formation 606. A leadscrew nut 608 5 has an internal screw thread 610, which engages the thread 606 on leadscrew 600, so that the nut will be driven axially of the leadscrew 600, by rotation of motor 604. The housing 602 is of generally rectangular section and the nut has flats 612 which are a close clearance fit with opposed sides 614 of the housing, in order to prevent rotation of the nut 608 with the leadscrew 600.

A clutch actuator cable 620 is attached directly to the nut 608, a nipple 622 on cable 620, locating in the larger diameter portion of a stepped bore 624 passing through the nut 608, parallel to the thread formation 610.

15 With the embodiment described with reference to figures 3 and 4, the loads applied to the leadscrew nut 608 and leadscrew 600, upon actuation of the clutch will be non-axial, thereby resulting in increased friction, requiring a more powerful motor and also reducing the life of the actuator due to increased wear.

20 In the modification illustrated in figure 5, a cage 630 is secured to the leadscrew nut 608. The cage 630 provides a fommation 632 for attachment of the cable 620.

A pair of rollers 634 are furthermore mounted in the cage 630, for engagement of the upper and lower walls of the housing 602, as illustrated in figure 5, in order to react the loads applied to the nut 608 upon actuation of the clutch, thereby 25 reducing friction and wear of the leadscrew 600 and nut 608.

In a further modification to the embodiment illustrated in figure 5, as illustrated in figures 13 and 14, the cage 630' is pivotally attached to leadscrew nut 608, on bunions 638. A single roller 634' is mounted on the cage 630' for engagement of 30 the lower wall 638 of housing 602, as illustrated in figures 13 and 14. Formation 632' for attachment of cable 620 is provided on the cage 630' on the opposite side

- 10 of the bunions 638 to the roller 634'. Tension in the cable 620 will thereby maintain the roller 634' in engagement with the wall 636' of the housing 602, in order to react the loads applied to the nut 608 upon actuation of the clutch.

5 With some cable operated clutch release mechanisms of this type, the point of attachment of the cable to the release mechanism moves axially, as the mechanism is rotated by the clutch actuator. In order to allow for this axial movement the arcuate cable guide 34, as illustrated in figure 1 is formed as a helix. In this manner for a total release travel of 24mm, of the order of 7.5mm 10 axial travel may be accommodated. Additional axial travel may be accommodated by flexing of the cable, provided that the cable has sufficient flexibility and there is enough space within the actuator to allow misalignment of the cable. Where, as in the present invention, it is desirable to locate the actuator as close as possible to the release mechanism, the length of the cable and space 15 restraints will place severe restraints on the degree to which axial travel can be accommodated. In the modification illustrated in figure 6, The leadscrew 600 and leadscrew nut 608 are mounted coaxially of a housing 640 of circular section. A helical groove 20 642 is formed in the wall of the housing. A roller 644, is mounted on the nut 608, for rotation about and axle 646. The roller 644 locates in and engages the side walls of helical groove 642.

As with the embodiment illustrated in figures 3 and 4, the cable 620 is secured to 25 the nut 608 at a point offset from the axis thereof. An arcuate slot 648 is provided through the end of housing 602 for the cable 620.

Upon rotation of the leadscrew 600, engagement of the roller 644 in the groove 642 will prevent nut 608 from rotating with the leadscrew 600, thereby driving the 30 nut 608 axially of the leadscrew 600. As the nut 608 is driven axially of the leadscrew 600, engagement of roller 644 in groove 642 will however cause the

- 11 nut 608 to rotate, so that the cable is moved axially of the release mechanism, between the positions shown in full and broken line in figure 6.

In the embodiment illustrated in figures 7 to 9 an annular hydraulic slave cylinder 5 212 is mounted in a clutch housing 214, adjacent a gear box (not shown), by means of bolts which locate through holes 222 in an actuator housing 242, so that the slave cylinder 212 is coaxial of the gearbox input shaft and is disposed between the gearbox and a clutch, details of the clutch having been omitted for clarity. The housing 242 defines an outer cylindrical wall 220. A tubular member 224, having a flange formation 226, is secured and sealed to the housing 242, coaxially of the outer cylindrical wall 220, to form the inner cylindrical wall of an annular cylinder 228, the end of the annular cylinder 228 adjacent the gearbox being 15 closed by the flange formation 226.

An annular piston 230 is slidably located in the annular cylinder 228 and sealed with respect to the inner and outer cylindrical walls thereof by means of seal 232.

The end of the piston 230 adjacent the open end of the annular cylinder 228 is 20 secured to a rolling thrust bearing 234 which is adapted to engage a diaphragm release spring of the clutch. A helical compression spring 236 acts between the housing 242 and thrust bearing 234 to urge the thrust bearing 234 into engagement with the clutch release spring.

25 The housing 242 also defines a master cylinder 270, the axis of the cylinder 270 being disposed transverse to and offset from the axis of the annular cylinder 228.

Cylinders 228 and 270 are interconnected by passageway 272 which is formed in the housing 242.

30 A cylindrical extension 280 is secured at its inner end to the master cylinder 270 and extends coaxially thereof, the outer end of the extension 280 emerging

- 12 through an aperture 282 in the wall of the clutch housing 214. An electric motor 240 is located at the outer end of cylindrical extension 280, coaxially of the cylindrical extension 280 and master cylinder 270.

5 The shaft 246 of the electric motor 240 defines a leadscrew 260. A leadscrew nut 250 is slidably located in the cylindrical extension 280. The leadscrew nut 250 has a flange formation 252 which extends into close proximity with the wall of the cylindrical extension 280 and has a plurality of angularly spaced projections 254 which engage in axially extending grooves 282 in the wall of the cylindrical 10 extension 280, in order to prevent rotation of the leadscrew nut 250. The leadscrew nut 250 has a thread formation 256, which engages a corresponding thread formation 258 on the leadscrew 260.

A piston 290 is slidably located in the master cylinder 270. The leadscrew nut 250 15 is connected to the piston 290 by means of a ball and socket joint 264, which locates in a socket formation 266 in the adjacent end of piston 270. At the junction between the cylindrical extension 280 and the master cylinder 270 an annular recess 284 is defined in which are located a retaining ring 286 and a sealing ring 288, the sealing ring 288 sealingly engaging the piston 290.

A compensating spring 216 acts between the flange formation 252 and outer end of cylindrical extension 280, to urge the leadscrew nut 250 towards the master cylinder 270.

25 When the clutch is engaged the leadscrew nut 250 will be disposed to the right of the cylindrical extension 280 and the piston 290 is located at the outer end of master cylinder 270, as illustrated in Figure 7. Upon energisation of the electric motor 240 to disengage the clutch, rotation of the leadscrew 260 will cause the leadscrew nut 250 to be displaced to the left, pushing piston 290 into the master 30 cylinder 270, so that hydraulic fluid therein is displaced under pressure into the slave cylinder 212, to apply an axial load to the clutch release spring which will

- 13 disengage the clutch. To re-engage the clutch, the motor 240 is reversed to screw the leadscrew nut 250 back to the right and retract the piston 290, so that hydraulic fluid flows back into the master cylinder 270, allowing the slave cylinder 212 to retract and the clutch to reengage.

The compensating spring 216 acts in similar manner to compensating spring 116 of the embodiment illustrated in Figure 2, to reduce the load required from the electric motor 240.

10 In the embodiment illustrated in Figures 7 to 9, the cylindrical extension 280 acts as a reservoir for hydraulic fluid, the seal 268 permitting passage of fluid from cylindrical extension 280 into the master cylinder 270, upon return movement of the leadscrew nut 250 and piston 290 to the right, in order to compensate for leaked fluid and for wear of the components of the clutch. In order to ensure that 15 fluid is fed from the cylindrical extension 280 to the master cylinder 270, the housing 242 is disposed relative to the clutch housing 214, so that the cylindrical extension 280 is inclined upwardly from the master cylinder 270 to the electrical motor 240, at an angle of at least 20 , as illustrated in Figure 9. The hydraulic fluid in the reservoir defined by cylindrical extension 280 also serves to lubricate the 20 leadscrew mechanism 250,260.

As illustrated in Figure 10, a concentric slave cylinder 212 of the type disclosed with reference to Figures 7 to 9, as defined by a housing 342 also defines a pair of master cylinders 370',370", the master cylinders 370',370" being disposed 25 diametrically of one another, the cylinders 370',370" being disposed transverse to an offset from the axis of the annular cylinder 228 of the slave cylinder 212.

Master cylinders 370',370" are interconnected with annular cylinder 228, by passageways 372 formed by the housing 342.

30 A pair of pistons 390',390" are slidingly located, one in each of the cylinders 370',370" and are sealed with respect thereto by annular seals 388, the seals 388

- 14 being located in circumferential grooves 384 formed at the ends of pistons 390',390" adjacent the slave cylinder 212.

An electric motor 340 is mounted at the outer end of cylindrical extension 380 of 5 the portion of housing 342 defining the cylinders 370', 370", the axis of the motor 340 being parallel to and spaced centrally of the axis of the cylinders 370',370", on a common plane therewith.

The output shaft 346 of the motor 340 defines leadscrew 360, the free end of the 10 leadscrew 360 engaging a bearing 366 mounted in a portion of the housing 342, between cylinders 370',370".

A leadscrew nut 350 is mounted on the leadscrew 360, a thread formation 356 on the leadscrew nut 350 engaging a corresponding thread formation 358 on the 15 leadscrew 360. The leadscrew nut 350 has a flange formation 352, to which the outer ends of pistons 370'.370" are secured.

A compensating spring 316 acts between the flange formation 352 and the outer end of the cylindrical extension 380, to urge the leadscrew nut 350 towards the 20 cylinders 370',370".

As with the embodiment disclosed with reference to Figures 7 to 9, rotation of the electric motor 340 will be translated to axial movement of the leadscrew nut 350, which is prevented from rotating by the pistons 390',390". The pistons 390',390" 25 may thereby be moved to the left as illustrated in Figure 10, in order to force hydraulic fluid into the slave cylinder 212 and release the clutch, or to the right to allow hydraulic fluid to drain from the slave cylinder 212 and release the clutch.

As with the embodiment illustrated in Figures 7 to 9, the cylindrical extension 380 30 also defines a hydraulic reservoir. Passageways 330 are provided in the housing 342 to connect the cylindrical extension 380 to the cylinders 370',370", at a point

- 15 which will be disposed on the slave cylinder side of the pistons 390',390", when the pistons 390',390" are at the outermost limit of their movement and will be closed by the pistons 390',390" at the start of their movement towards the slave cylinder 212. When the pistons 390',390" are fully retracted fluid may 5 consequently flow from the reservoir defined by cylindrical extension 380 to the cylinders 370',370", via passageways 330, to replenish fluid leaking from cylinders 370'.370" or slave cylinder 212 and to accommodate any wear of the clutch components. A breather 332 is also provided to the cylindrical extension 380 to maintain the reservoir at atmospheric pressure.

While in the above embodiment a pair of cylinders 370',370" are defined by housing 342, more than two cylinders 370',370" may be arranged, preferably symmetrical of the leadscrew 360.

15 In the embodiment illustrated in Figure 11, a clutch actuator 410 has a cylindrical housing 480. A fixed annular piston 490 is located coaxially of the cylindrical housing 480 at one end thereof. An axial bore 472 of the piston 490 is connected to the annular cylinder 228 of the slave cylinder 212, as illustrated in figures 7 to 9. 20 A closed master cylinder 470 is slidably mounted on the external

surface of piston 490 and is sealed with respect thereto by means of Oring 488, which is mounted in an annular groove 484 adjacent the open end of cylinder 470. A flange formation 452 is provided adjacent the open end of the cylinder 470, a radial projection 454 on the flange formation 452 extending into an axial groove 482 in 25 the wall of the cylindrical housing 480, in order to prevent rotation of the cylinder 470. An electric motor 440 is mounted at the end of the cylindrical portion 480 remote from the piston 490, the axis of the electric motor 440 being coaxial of the 30 cylindrical housing 480. The output shaft 446 of the electric motor 440 defines a leadscrew cylinder 460, the leadscrew cylinder defining a nut formation 450 at the

- 16 end adjacent the piston 490. The nut fommation 450 has an internal screw thread formation 456, which engages a corresponding screw thread 458 on the external surface of the cylinder 470.

5 A compensating spring force 416 acts between the flange formation 452 and the outer end of the cylindrical housing 480, to urge the cylinder 470 towards the piston 490.

Electric motor 440 may thereby be used to move cylinder 470 axially of the piston 10 490, forcing hydraulic fluid into the annular cylinder 228 of slave cylinder 212, as it is moved to the left, as illustrated in Figure 11 and allowing hydraulic fluid to exit the annular chamber 228 as it is moved to the right, as illustrated in Figure 11.

Axially extending grooves 492 are provided on the inner end of piston 490. The 15 seal 488 is arranged so that at the limit of movement of the cylinder 470, towards motor 440, the seal 488 will be positioned on the grooved portion of the piston 490. Hydraulic fluid is thus allowed to leak into cylinder 470 through the grooves 492, from a reservoir defined by cylindrical housing 480 into chamber 470 to replace fluid therein, when the cylinder 470 is at the limit of its towards the motor 20 440.

Unlike the embodiments illustrated with reference to Figures 7 to 9 and Figure 10, in this embodiment, the cylindrical housing 480 should be orientated downwardly from the end defining piston 490 to the electric motor 440, so that fluid will be able 25 to flow downwardly from the reservoir into the master cylinder 470, passed seal 488. In the embodiment illustrated in Figure 12, a clutch actuator 510 has a cylindrical housing 580. A closed master cylinder 570 is defined by the cylindrical housing 30 580. The master cylinder 570 is connected to annular chamber 228 of the slave

- 17 cylinder 212, via passageway 572. A square pin formation 574 extends centrally of the master cylinder 570 from the closed end of master cylinder 570.

An piston 590 Ridably engages in the master cylinder 570, the piston 590 being 5 sealed with respect to the wall of the master cylinder by sealing element 588. A cylindrical extension 592 extends coaxially of the piston 590, away from the closed end of cylinder 570. The pin formation 574 engages a complimentary shaped, closed axial bore in the piston 590/extention 592, to prevent rotation of the piston 590/extention 592. The extension 592 of piston 590 has a screw thread formation 10 558 on its external diameter.

An electric motor 540 is mounted at the end of cylindrical housing 580 remote from the master cylinder 570, the axis of the electric motor 540 being coaxial or the master cylinder/piston assembly 570/590. The output shaft 546 or the electric 15 motor 540 defines a leadscrew cylinder 560. The leadscrew cylinder 560 defines a nut formation 550 at the end thereof remote from the motor 540. The nut fommation 550 has an internal screw thread formation 556, which engages screw thread formation 558 on the extension 592 of piston 590.

20 Electric motor 540 may thereby be used to move piston 590 axially of the master cylinder 570, forcing hydraulic fluid into the annular chamber 228 of slave cylinder 212, as shown in figures 7 to 9, as the piston 590 moves to the left as illustrated in Figure 12 and allowing hydraulic fluid to be returned from the slave cylinder 212 to the master cylinder 570, as the piston 590 is moved to the right as illustrated in 25 Figure 12.

The cylindrical housing 580 between master cylinder 570 and the electric motor 540 also defines a reservoir for hydraulic fluid. Axial grooves 530 are provided in the end of the master cylinder 570, the grooves 530 providing a passageway 30 between the reservoir and the master cylinder 570, when the piston 590 is at the limit of its movement towards the motor 540. Fluid may consequently pass from

- 18 the reservoir into the master cylinder 570, through passageways 530 when the piston 590 is fully retracted from the master cylinder 570. The passageway 530 is closed to the master cylinder 570 by sealing element 588, upon movement of the piston 590 away from the electric motor 540.

The clutch actuators illustrated in figures 11 and 12 may be fommed integrally of the housing defining a concentric slave cylinder 212, in the manner disclosed with reference to figures 7 to 9 and 10. Alternatively the clutch actuators 410,510 may be remote from the clutch slave cylinder and connected by pipes or hydraulic 10 hoses.

Various modifications may be made without departing from the invention. For example, the cable operated clutch release mechanism of the embodiments illustrated in Figures 1 to 6,13 and 14 may be of different design, utilising, for 15 example, helical screw treads to translate rotational movement of the driving plate into axial movement.

In the embodiment illustrated in Figure 2, the self-clamping arrangement for the cable may be omitted, the cable being of fixed length or being manually clamped 20 at the appropriate position.

In an alternative embodiment of the hydraulic mechanism described with reference to Figures 7 to 9, the piston may be formed integrally of the leadscrew or leadscrew nut or be connected thereto in some other manner.

According to alternative embodiments the master cylinder/piston may be of annular configuration.

The hydraulic mechanisms described with reference to Figures 7 to 9, 10, 11 or 30 12 may also be used with multiple concentric slave cylinders, separate master

- 19 cylinders for each cylinder of the slave cylinder being provided at angularly spaced locations on a common housing.

In the embodiment illustrated in Figure 7 to 9, or11, instead of having 5 interengaging formations on the leadscrew nut 250 and housing 242 to prevent rotation of the leadscrew nut 250, other means may be used. For example spring 216 may serve thispurpose The inclusion of compensating springs 116, 216 in the mechanisms of the present 10 invention is optional.

The patent claims submitted with the application are proposed formulations without prejudice to the achievement of further patent protection. The applicant 15 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 20 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

25 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.

- 20 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 5 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 10 they concern manufacturing, testing and work processes.

Claims (1)

1. - 21 Claims

   1. A clutch control system comprising a concentric clutch release mechanism and clutch actuator means mounted in close proximity to the concentric 5 clutch release mechanism, the clutch actuator means comprising an electric motor mounted radially of the clutch release mechanism, the electric motor being connected by a leadscrew and nut mechanism to the actuating means for the clutch release mechanism.

   10 2. A clutch control system according to claim 1 in which the clutch actuator is driven by cable means.

   3. A clutch control system according to claim 2 in which a leadscrew cylinder is connected coaxially to the motor, the leadscrew cylinder having an 15 internal screw thread which engages a corresponding thread on a leadscrew, the leadscrew being connected to one end of a cable, the other end of the cable being connected to the clutch release mechanism.

   4. A clutch control system according to claim 3 in which the cable is of high 20 torsional stiffness so as to prevent rotation of the leadscrew.

   5. A clutch control system according to claim 2 in which the electric motor is drivingly connected to a leadscrew nut, the leadscrew nut engaging a leadscrew so that on rotation of the leadscrew nut the leadscrew will be 25 driven axially of the leadscrew nut, the leadscrew nut being attached to one end of a cable, the other end of the cable being attached to the clutch release mechanism.

   6. A clutch control system according to claim 5 in which clamping means is 30 provided to clamp the cable with respect to the leadscrew, at an appropriate datum position.

   - 22 7. A clutch control system according to claim 5 or 6 in which means is provided for preventing rotation of the leadscrew.

   5 8. A clutch control system according to claim 7 in which formations are provided on the leadscrew for engagement of corresponding axially extending formations on a housing to prevent rotation of the leadscrew.

   9. A clutch control system according to claim 2 in which a leadscrew is 10 drivingly connected to an electric motor, a leadscrew nut engages the leadscrew, the leadscrew nut being restrained from rotation with the leadscrew, the cable means being attached to the leadscrew nut at a position off-set from the axis of the leadscrew.

   15 10. A clutch control system according to claim 9 in which means is provided of reacting non-axial forces on the leadscrew nut.

   11. A clutch control system according to claim 9 or 10 in which means is provided for adjusting alignment of the cable relative to the clutch release 20 mechanism, as the actuator moves the cable.

   12. A clutch control system according to any one of claims 1 to 11 in which the clutch release mechanism and the clutch actuator means are secured to a clutch housing.

   13. A clutch control system according to claim 1 in which the clutch release mechanism is a concentric hydraulic slave cylinder.

   14. A clutch control system according to claim 13 in which the clutch actuator 30 comprises a master cylinder formed in a common housing with the slave cylinder, the master cylinder being disposed transverse to and offset from

   - 23 the axis of the slave cylinder and the slave cylinder and master cylinder being interconnected by a passageway defined by the housing, said leadscrew and nut mechanism being arranged to control movement of a piston in the master cylinder.

   15. A clutch control system according to claim 14 in which a leadscrew is drivingly attached to the electric motor, the leadscrew nut engaging the leadscrew and being connected to the piston of the master cylinder for movement of the piston axially of the master cylinder.

   16. A clutch control system according to claim 14 or 15, in which the leadscrew nut is connected to the master cylinder piston, by means of a ball and socket joint.

   15 17. A clutch control system according to any one of claims 14 to 16 in which the leadscrew and leadscrew nut are located in a cylindrical housing, the motor being located coaxially of the master cylinder at the end of the cylindrical housing remote from the master cylinde.

   20 18. A clutch control system according to claim 17 in which the cylindrical housing acts as a reservoir for hydraulic fluid.

   19. A clutch control system according to claim 16 in which a seal is located in a recess in the wall of the master cylinder, the seal being adapted to allow 25 passage of hydraulic fluid from the reservoir into the master cylinder, upon movement of the piston out of the master cylinder.

   20. A clutch control system according to any one of the preceding claims in which a compensating spring acts on the leadscrew or leadscrew nut.

   - 24 21. A clutch control system substantially as described herein with reference to, and as shown in, Figure 1, Figure 2, Figures 3 and 4, Figure 5, Figure 6, Figures 7 to 9, Figure 10, Figure 11, Figure 12 or Figures 13 and 14 of the accompanying drawings.