GB2387209A

GB2387209A - A clutch operated by an electric motor having leadscrew and nut mechanism

Info

Publication number: GB2387209A
Application number: GB0207989A
Authority: GB
Inventors: Richard Brian Moseley; Leigh Darren Fraser; David Anthony Harries; Julian Alistair Buckler; John Vivian Comfort
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: 2002-04-06
Filing date: 2002-04-06
Publication date: 2003-10-08
Also published as: GB0207989D0

Abstract

A clutch actuator comprises a concentric clutch release mechanism 12 connected to an electric motor 40 by a cable 30 and leadscrew and nut mechanism 50, 60. The cable 30 is of high torsional stiffness so that upon rotation of the motor 40 it will resist rotation of the leadscrew 60 and the leadscrew 60 will be driven axially of the nut 50, to pull or push the cable 30, thereby rotating a driving plate 24 which disengages/engages a clutch via clutch release mechanism 12. A compact arrangement is provided by locating the actuator in close proximity to the release mechanism 12 and mounting the motor 40 tangentially with respect to the release mechanism 12. In another embodiment the cable 30 is replaced with a hydraulic system having master and slave cylinders (270, 212, fig 4) formed in a common housing and connected to the leadscrew mechanism 50, 60.

Description

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 s mechanism 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

10 application, disclose clutch release 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.

15 Typically the cable will be pulled and pushed by means of a remote actuator mechanism.

Instead of the mechanical clutch release mechanism disclosed above the clutch may be controlled by a concentric hydraulic slave cylinder of the 20 type disclosed in US4526258; US4637505; US6273231; US20010011626; US20010047918; or 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 25 remote master cylinder of, for example, the type disclosed in GB231 3885; GB2317933; GB2325036 or GB2309761, the disclosures

of which explicit 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, so pipes or pressure hoses.

f

Electric motor actuators which are used with the clutch release mechanisms 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 s high speed, relatively low torque drive 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 to release 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.

Is The present invention provides a clutch control system with a clutch actuation 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 to can be pre-assembled or may allow preassembly on a clutch housing.

This places restraints on the clutch actuator in order to allow it to be accommodated in the restricted space available.

In accordance with the present invention a clutch control system 25 comprises a concentric clutch release mechanism and clutch actuator means mounted in close proximity to the concentric 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 actuating means so for the clutch release mechanism.

b 1.

Preferably, both clutch release mechanism and clutch actuator means are 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 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 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 15 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 20 reference to the accompanying drawings, in which: Figure 1 illustrates in sectional elevation a clutch actuator and release mechanism in accordance with the present invention; 25 Figure 2 illustrates in sectional elevation an alternative form of clutch actuator for actuation of the release mechanism illustrated in Fig. 1; Figure 3 illustrates in sectional end elevation a clutch actuator and a release mechanism of an alternative embodiment of the present invention;

Figure 4 illustrates in sectional side elevation the clutch actuator and release mechanism along the line IV-IV of Fig. 3; and Figure 5 illustrates the embodiment of Figs. 3 and 4, in situ in the clutch s housing of a motor vehicle.

Fig. 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.

Fig. 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.

Is 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, between the gearbox and the clutch. A to 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 as ramp 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 so 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 5 the cable 30 to move in a plane parallel to that 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 lo being disposed in 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 15 housing 42 coaxially of the electric motor 40, a thrust roller bearing 52 being provided at the 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.

to 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 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 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 the driving plate 24 in one direction s 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 Jo may 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. Fig. 2 shows an alternative form of clutch actuator for use with the clutch release mechanism 12 described with reference to Fig. 1.

In the actuator illustrated in figure 2 a leadscrew 160 is mounted to coaxially of an actuator housing 142, for movement axially thereof. The actuator housing 142 locates through an aperture in the clutch housing 14, the axis of the leadscrew 1 60 being disposed in the plane of rotation and tangentially of the radial section 34 of the clutch release mechanism 12. A flange formation 1 10 is secured to the inner end of the leadscrew 25 160, the flange formation 1 10 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 axially extending grooves 1 14 in the internal diameter of the actuator housing 142, to prevent rotation of the leadscrew 160. A compensating spring so 1 16 acts between the inner end 1 18 of the actuator housing 142 and the

flange formation 110, to bias the leadscrew 160 away from the inner end 11 8 of the actuator housing 142.

An electric motor 140 is mounted at the outer end of the actuator 5 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 of a leadscrew nut 150, which is mounted in the actuator housing 142, coaxially of the leadscrew lo 1 60, 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 1 40, will cause axial 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 counter bore166 by means of a biasing to spring 182, acting between the outer ends of the conical jaws 180 and a cap formation 184 secured to the outer end of leadscrew 1 60. 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 5 retracted 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 1 62 of the leadscrew 160 and past the conical jaws 180. The pin or circlip 188 may then be removed to release the conical jaws 180 to clamp the cable 1 30, when the cable 130 has been pulled through the leadscrew 160 to 30 the correct datum position.

A flexible boot 172 is provided at the inner end 1 18 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.

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.

When the clutch is engaged, the leadscrew 160 will be displaced to the right as illustrated in figure 2, so that the compensating spring 1 16 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 Is be opposed by the compensating spring 1 16, so as to assist the electric motor 140. Only after the load applied by the clutch release spring balances that applied by the compensating spring 1 16 is the motor 140 put under load, in order to complete clutch disengagement. Upon reengagement of the clutch, the initial movement of the release 20 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 compensation spring 1 16 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 Us 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, thereby permitting the use of a substantially smaller motor 140.

so In the embodiment illustrated in figures 3 to 5 an annular hydraulic slave cylinder 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 lo 228 adjacent the gearbox being 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 15 the annular cylinder 228 is 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.

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.

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

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 5 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 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 lo formation 258 on the leadscrew 260.

A piston 290 is slidably located in the master cylinder 270. The leadscrew nut 250 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 Is 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.

to 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.

When the clutch is engaged the leadscrew nut 250 will be disposed to 25 the right of the cylindrical extension 280 and the piston 290 is located at the outer end of master cylinder 270, as illustrated in Fig. 4. 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 cylinder 270, so that so hydraulic fluid therein is displaced under pressure into the slave cylinder 212, to apply an axial load to the clutch release spring which will

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 Fig. 2, to reduce the load required from the electric motor 240.

10 In the embodiment illustrated in Figs. 3 to 5, 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, upom 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 Is the clutch. In order to ensure that 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 Fig. 5. The hydraulic 20 fluid in the reservoir defined by cylindrical extension 280 also serves to lubricate the leadscrew mechanism 250,260.

Various modifications may be made without departing from the invention.

For example, the cable operated clutch release mechanism of the 2s embodiments illustrated in Figs.1 and 2 may be of different design, utilising, for example, helical screw treads to translate rotational movement of the driving plate into axial movement.

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

In an alternative embodiment of the hydraulic mechanism described with reference to Figs.3 to 5, the master cylinder piston may be connected to the leadscrew and the motor adapted to drive the leadscrew nut, in 5 similar manner to the embodiments shown in Figs. 1 and 2. Moreover, 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 to of annular configuration or multiple master cylinders/pistons may be provided. The hydraulic mechanism described with reference to Figs. 3 to 5 may also be used with multiple concentric slave cylinders, separate master Is cylinders for each cylinder of the slave cylinder being provided at angularly spaced locations on a common housing.

In the embodiment illustrated in figure 3 instead of having interengaging formations on the leadscrew nut 250 and housing 242 to prevent rotation to of the leadscrew nut 250, other means may be used. For example spring 216 may serve this purpose. Alternatively the use of two or more mastercylinder/pistons driven by the same leadscrew nut will prevent rotation of the leadscrew nut.

:5 The inclusion of compensating springs 1 16, 216 in the mechanisms of the present invention is optional.

The patent claims submitted with the application are proposed formulations without prejudice to the achievement of further patent so 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 5 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.

10 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 15 of one of the objects of the preceding sub-claims. i 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

to 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 25 new process stages or sequences of process stages via combinable characteristics, even where they concern manufacturing, testing and work processes.

Claims

1. A clutch control system comprising a concentric clutch release mechanism and clutch actuator means mounted in close proximity 5 to the concentric 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.

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 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 torsional stiffness so as to prevent rotation of the leadscrew. 25

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 driven axially of the leadscrew nut, the leadscrew nut being attached to one end of a cable, the other end of the so cable being attached to the clutch release mechanism.

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

5

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

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

9. A clutch control system according to any one of claims 2 to 8 in which the clutch release mechanism and the clutch actuator means are secured to a clutch housing.

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

20

1 1. A clutch control system according to claim 10 in which the clutch actuator comprises a master cylinder formed in a common housing with the slave cylinder, the master cylinder being disposed transverse to and offset from the axis of the slave cylinder and the slave cylinder and master cylinder being interconnected by a 25 passageway defined by the housing, said leadscrew and nut mechanism being arranged to control movement of a piston in the master cylinder.

12. A clutch control system according to claim 11 in which a 30 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.

13. A clutch control system according to claim 1 1 or 12, in which the s leadscrew nut is connected to the master cylinder piston, by means of a ball and socket joint.

14. A clutch control system according to any one of claims 1 1 to 13 in which the leadscrew and leadscrew nut are located in a cylindrical to extension of the master cylinder, the motor being located coaxially of the master cylinder at the end of the cylindrical extension remote from the master cylinder.

Is

15. A clutch control system according to claim 14 in which the cylindrical extension acts as a reservoir for hydraulic fluid.

16. A clutch control system according to claim 15 in which a seal is located in a recess in the wall of the master cylinder, the seal being to adapted to allow passage of hydraulic fluid from the reservoir into the master cylinder, upon movement of the piston out of the master cylinder.

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

18. A clutch control system substantially as described herein with reference to, and as shown in, Fig. 1, Fig. 2 or Figs. 3 to 5 of the so accompanying drawings.