GB2207969A

GB2207969A - Servo-device for a double clutch using two over-centre springs

Info

Publication number: GB2207969A
Application number: GB08809277A
Authority: GB
Inventors: Edwin Karch
Original assignee: Sachs Systemtechnik GmbH
Current assignee: Sachs Systemtechnik GmbH
Priority date: 1987-04-29
Filing date: 1988-04-20
Publication date: 1989-02-15
Anticipated expiration: 2008-04-20
Also published as: GB2207969B; FR2614661A1; DE3714211A1; GB8809277D0

Description

2 "/'-'U 7 69 j cl bervo-device for a clutch The invention relates to a

clutch servo-de-7iceg especially for a motor vehicle double clutch, having an electric motor and a transmission which converts the rotary motion of a drive-output shaft of the electric motor into a substantially translational movement of an output member.

From DE-OS No. 3,438,50,4 a motor vehicle friction clutch is known which is engaged and disengaged through a servo-drive system. The servo-drive system is controlled by an ideal value emitter coupled with the clutch pedal, and comprises an electric motor which actuates the control cylinder of a hydraulic clutch release installation, throuEh a crank transmission. A position indicator con-ected with the electric motor here detects the actual position of the servo-drive system.

In such a servo-drive system the electric motor must supply the whole of the force necessary for disengagement. Therefore it has to be comparatively stoutly dimensioned, since the clutch must be released in a comparatively short time, for example fractions of a second.

It is the problem of the invention to indicate a servo-device suitable especially for motor vehicle double clutches, which renders possible a rapid and smooth clutch actuation, with an electric motor of comparatively small dimensions.

This problem is solved by the features as stated in the chnracterising Dart of Claim 1. Within the scope of

2 the invention, in addition to the electric motor two spring storage means are provided. The spring storage means are supported between a component driven in rot,tion by the motor between two end positions, for the one Dart, and a support point of fixed position for tb other part. A first spring storage means supports the electric motor in the movement in the release direction, so that the release movement rroceeds rapidly. In the engagement direction the spring storage means is stressed by the electric motorl in which however it is supported from the clutch spring. In this way the electric motor can be of comparatively slight dimensions. In order to achieve a secure end position of the first spring storage means in its position allocated to the engaged position of the clutch, the first sprinE storage means is expediently situated in a beyronddead-centre Dosition when the clutch is engaged.

Clutches frequently require an actuation force which is irregular in relation to the release distance. This is valid especially for double clutches having two clutch units which are actuated in succession in the movement of the releaser. The actuation force of such a double clutch runs, in dependence upon the release travel, through two maximum values of different maEnitudes, between which there lies a minimum value. In order that even in such a case the torque to be supplied by the electric motor of the servo-device may be kept as constant and low as possible, in accordance with the invention a second spring storaEe means is Drovided which is superimposed, acting contrarily, upon the spring force of the first spring sto--r-aEe means.

in a nartial zone of the rotating movement of the rotating component connected with the first spring storage means. For this purpose, in relaticn to the end position of the component allocated to the engaged position of the clutch, the second spring s'uoraEe means is arranged in such a beyonddead-centre position that it is stressed at least over a partial zone of the rotating movement of the component, while the first spring storage means is being relaxed. The second spring storage means thus evens out, fluctuations of the toroue to be supplied by the electric motor.

In a preferred development the second spring storage means is coupled with the component driven b.-,, the electric motor through an idle-motion device, for example a peE-slot joint, so that the initial anEle of rotation, at which the compensating effect of the second sprinE storage means begins, can be shifted towards the end positions. A stop of fixed location here limits the pivoting movement of the second spring storage means in the enEaEement direiction beyond the end position.

Ilin example of embodiment of the invention will be explained hereinafter by reference to a drawing, wherein FIGIMEE 1 shows a represent..tion of principle of a servo-drive system suitable for a motor vehicle double clutch; 2 2-5 FIG= 2 shows three moment curves for the reaction moment of the clutch, the drive moment of an electric notor of the servo-drive system and a first of two sprinE store-e means of the servo-drive system; v 4 - FIGURE 3 shows three moment curves similarly to Figure 2, when using two spring storage means according to Figure 1 It is proposed, for the automatic actuation of friction clutches, to provide electric motorswhich are supported in their work by force storage means, whereby it is possible to use relatively small electric motors. The principle of arrangement is here reproduced in Figure 1. The servodevice 1 consists of an electric motor 2, the worm 4 of which co- operates with a worm wheel 3. A hydraulic control cylinder 5 for the clutch actuation is pivotably mounted and also a spring storage means 7 is articulated to the worm wheel 3 or - as in the present case - on a disc 6 connected fast in rotation with the worm wheel 3. In the present case the spring storage means 7 consists of a compression spring which bears both on a component fast with the housing and on the disc 6, in pivotable manner. The arrangement is here made such that when the friction clutch is in the engaged condition according to the illustration in Figure 1 the spring storage means 7 is arranged by the small anEle V beyond the dead centre. Thus a secure end position of the entire servo- device 1 is guaranteed. To initiate the release movement the worm wheel 3 and the disc 6 are rotated, by means of the electric motor 2, in the counterclockwise direction indicated by the arrow F. In this action the electric motor 2 can move the spring storage means 75 without perceptible force strain, beyond the deadcentre position and after the anglet is travelled the spring storaEe means 7 has a supporting effect for the a 1 force development of the electric motor 2 in the release direction of the friction clutch. The friction clutch is then actuated in a manner not further illustrated - for example hydraulically - with interposition of the control cylinder 5.

In Figure 2 there are reproduced three different curves 11, 12 and 13 of the torque I'lL in dependence upon the anEle 6 that is the angle of rotation of the disc 6 in the direction of the arrow F. The moment curve 11 relates to the torque to be applied to the disc 6 for a double clutch. There it can be seen distinctly that the moment curve 11 has a first maximum which is to be allocated to the first clutch of the double clutch, then a minimum and following that a second maximum which is to be allocated to the second clutch of the double clutch. The moment generated by the spring storage means 7 in relation to the disc 6 is reproduced as curve 13 and acts against the moment curve 11. The curve 13 therefore extends outside the dead-centre position of Figure 1 in the negative moment range. The difference between-the two curves 11 and 13 is the moment curve 12 to be supplied by the electric motor 2, which curve in the present case extends in both the positive and negative moment ranEes. This means that the electric motor 2 is accelerated by the spring storage means 7 in the middle range of angle of rotation, while in the end range of the curve course a very high moment is to be supplied by the electric motor 2. Such a moment co-,irse correspondinE to the moment curve 12 is very unfavourable, since for the ene part the electric motor is to be designed for the maximum force to be supplied and for the other part a uniform course of the release and engagement movements is not achievable.

It is therefore proposed in accordance with the invent- ion to provide a second spring storage means 8 which is arranged according to Figure 1 likewise pivotably between an articulation point fast in space and an articulation point on the disc 6. It is likewise in a beyond-deadcentre position when the double clutch is in the engaged position, but admittedly the spring storage me.-.1ns 8 is pivoted past the pertinent dead centre by a greater angle than is the spring storage means 7 (angle). The angle which is decisive for the spring storage means 8 amounts 0 in order of magnitude to 40 Together with this second spring storage means 8 it is possible to influence the curve 13 according to Figure 2 so that the required force of the electric motor 2 (curve 12) receives a more equalised course. Bv a further constructive detail this curve can be adapted almost gaplessly to the theoretical ideal course.

For this purpose according to Figure 1 the point of artic ulation of the spring storage means 8 is provided on the disc 6 by means of a slot 10, in which a peg 10a engages.

This slot 10 effects a dela-ved action of the spring storage means 8 in an angle range CC of about 0 to 20 0 according to the existing conditions of the double clutch and trans mission ratios of the transmission elements. 'With the aid of this slot 10 it is now possible to achieve a moment course which is reproduced in Figure 3. Here again 11 represents the typical moment cu--ve for a double clutch. The moment curve 15 is composed of the effect of the two spring storage means 7 and 8 in combination with the slot 10. The moment curve 14, which represents the power requirement of the electric motor and in this case extends nearly horizontally in a narrow tolerance range, is produced as difference between the two moment curves 11 and 15. The moment curve 15 with its kink adapted to the curve 11 is produced inthat only the spring storage means 7 comes into effect in the angle ranEe as far as the kink (corresponding to.P). Then suddenly the added spring storage means 8 acts against this, so that the ty ical curve 15 is produced.

JP I- It adapts itself to the undulatory course of the moment curve 11 in such a way that the moment curve 14 for the electric motor 2 has a nearly ho.rizontal course. For the spring storage means 8 a stop 9 is provided which holds the spring storage means 8 in an end region of the slot 10 according to Figure 1 when the friction clutch is in the engaged position.

0 1 a i m s I.) Clutch servo-device, especially for a motor vehicle double clutch, having an electric motor (2) and a transmissien (3, 41 6) which converts the rot,ting movement of a drive-output shaft of the electric motor (2) into a substantially translational movement of an output member (5), characterised in that the transmission (3, 4 6) comprises a component (6) driven in rotation about an axis of rotation between two end positions in the drive movement of the output member (5), the first end position of which component is allocated to the engaged position of the clutch and the second end position is allocated to the r-leased -Dos"on of the clutch in that two spring storage e.i- -L L -L 5 - means 8) with dead-centre positions offset in angle in relation to one another are held each between a first Joint arranged with fixed location and a second joint eccentric of the axis of rotation and arranEed on the co=ponent, where a first one of the two spring storaEe means (7) is relaxed from the first to the second end position in the roteting movement of the component (6) and is stressed from the second to the first end position in the rotating movement5 and in that a second of the two spring st.o-.aEe means (8) assumes a beyond-dead-centre position when the component (6) is in the first end position, in such a mray that at least over a partial range of the rotating movement of the conDonent (6) from thie first to the second end position the second spring sto--!- age means (8) is stressed while the first spring storage means (7) is relaxed.

1 1

Claims

2.) Clutch servo-device according to Claim 1, characterised in that both

the first (7) and the second (8) spring storage means assume in the first end position a beyond-dead-centre position, and the second spring storage means (8) in the first end position is offset in relation to its deadcentre position by a greater beyonddead-centre an gl a (,6) of the component (6) then is the first spring storage means (7).

3.) Clutch servo-device according to Claim 1 or 2. characterised in that the second spring storage means (8) is supported in the first end position on a stop (9) of fixed location and in that the second joint of the second spring storage means comprises an idle-notion device (10, 10a) which permits a free anF-.le (d') of rotation of pre- determined size of the component (6) in relation to the second spring storage means (8).

4.) Clutch servo-device according to Claim 3, characte--ised in that the idle-motion device is form-ed as a peg-slot joint (10, 10a) between the component (6) and the first spring storage means (7).

5.) Clutch servo-device according to Claim 3 or 4, characterised in that the beyond-dead-centre angle of rotation of the first sprin7. storage means (7) is smaller than the free angle (,c() of rotption.

6.) Clutch servo-device according to one of ClaiT.ns 3 to 5, characterised in thall the free anEle (oC) of 0 rotation is less than 20 Clutch servo-device acco rding to one of Claims 3 to 6, characterised in that the beyond-dead-centre angle 0) of rotntion of the second sprinE storage means (8) amounts 0 to approxinatel-y 40 8.) Clutch servo-device substantially as described with reference to Figure 1 of the accompanying drawings.

Published 1988 at The Pate=. Off-ce. State House- 66 7-1 High Holborn. London WC1R 4TP- Fi=ther copies may be oba.r.ci frcr.-, The Patent 051ce. Sales Braneb. St Ma-y- Cray. Orp.ng::on. Rent BR5 3RD. Printed by Multiplex techrucries hd. S, Marv Cray. Kent Con 187