[001] RELEASING SYSTEM WITH CONSISTENT STROKE
UTILIZING WEAR AND TEAR COMPENSATION
[002]
[003]
[004] The invention relates to a releasing system for controlling a dutch and/or

Claim 1 -
[005]
[006] A clutch and/or an acceleration coupling, which may be configured as a
friction clutch, is an element of a motor vehicle drive train that is subjected to great strain. Even though the quality and lifetime of dutch linings have improved considerably, they are subject to operational wear even when used sparingly. A reduction in the thickness of the clutch lining Influences the position of a clutch spring, for example a membrane or disk spring, such that a releasing force or a contact force and thus also the necessary pedal force. Increase. In the state of the art, friction clutches and releasing systems are described that automatically compensate for clutch lining wear.
[007] DE 44 07 665 B4 disdoses a hydraulically actuatable releasing system for
a motor vehicle friction coupling. The releasing system consists of a piston-cylinder unit arranged concentrically to an incoming gear shaft, whose cylinder is affixed to the transmission housing. A piston is arrnged Inside the cylinder, whose lateral surface is at least partially encompassed by a guiding element. A preloading spring arranged on the releasing system serves to hold the release bearing of the releasing system in contact with the contact spring of the friction dutch. Through a retaining mechanisms for the guiding element, the guiding element functions as a stationary component during the inward and outward movement of the piston. The guiding element is initially forced to perform an axial movement when, with wear on the friction linings of the friction clutch, the piston is pushed deeper into the cylinder chamber by the contact spring of the friction dutch. The effect of the retaining mechamism is thereby canceled and the guiding element is displaced by an axial distance until the change In position of the contact

spring of the friction dutch is compensated for. As soon as a new balance of forces has been established, the guiding element comes to a stop. On the basis of this new position of the guiding element, the piston performs its inward movement with the usual piston stroke, where its stroke path is displaced in an axial direction compared to the stroke path of a clutch that is as good as new.
[008] The object of the present invention is to disclose a releasing system for
controding a dutch and/or an acceleration coupling in a motor vehicie. by way of whicn dutcn wrear can oe securely ana simply compensated for and wnicn can be manufactured with little complexity of manufacturing technique.
[009] The object of the invention is achieved by a releasing system of the generic
kind, which also features the characteristic traits of the main claim.
[010]
[011] A releasing system for a clutch and/or an accelerating coupling in a motor
vehicle consists of a piston-cyiinder unit, arranged concentrically to a transmission input shaft. The clutch and/or accelerating coupling is configured as a friction clutch, which can show wear over its lifetime. The piston-cylinder unit features a cylinder and two pistons, such that two pressure chambers in the cylinder are bounded. The cylinder can be arranged on a transmission housing. The first piston of the piston-cylinder unit serves as a working piston, where the second piston of the piston-cylinder unit represents a final position of the releasing system. The friction dutch is operated by the inward and outward movement of the working piston. The two pressure chambers of the piston-cylinder unit can be separately controlled with a pressure medium. The first pressure chamber of the piston-cylinder unit, which is bounded by the two pistons of the piston-cylinder unit, is preferably pneumatically controlled, while the second pressure chamber of the piston-cylinder unit is hydraulically controlled. The second pressure chamber, which is filled with a hydraulic pressure medium, is closed by a check valve In a pressure medium line and by a control valve in a back flow line, as soon as the releasing system fills the first pressure chamber with the corresponding operating pressure. During the rest phase of the dutch, a certain pressure will be maintained in the second pressure chamber of the piston-cyiinder unit by way of an overflow

valve in the hydraulic back flow line; the pressure corresponding to the resting force of a preloading spring. In this way, it is assured that a release bearing of the releasing system always abuts the contact spring of the clutch, which means that a preloading spring can be dispensed with. If wear occurs between a contact disk and the friction linings of the friction clutch, a force is exerted on the release bearing and thus an axial force on the piston-cylinder unit. The two pistons of the piston-cylinder unit will be displaced by this force in the direction of the

spring of the friction clutch that is caused by wear, is compensated for. As soon as a new balance of forces has been established, the two pistons come to a standstill. Through the compensation for wear and tear, the final position of the second piston of the piston-cylinder unit is also displaced in the direction of the transmission-side end of the cylinder, such that there is an axial displacement of the piston stroke when there is a clutch release. Based on this new position of the two pistons, the working piston performs its inward and outward movement with the usual piston stroke, because the first pressure chamber of the prston-cylinder unit is always supplied with a constant pressure by way of the pressure generating device. With continuing operation of the release system, the pistons, due to Increasing wear on the friction dutch, will be increasingly displaced in the direction of the transmission-side end of the cylinder. With maximum dutch wear, the second piston of the piston-cylinder unit reaches a final position on the transmission-side of the cylinder. In this position as well, the working piston performs the usual piston stroke.
[012)
[013] Below, the basic prindple of the invention, which allows for a plurality of
embodiments, will be explained in more detail with reference to a drawing.
[014] The sole Figure shows a release system for controlling a friction clutch in
a motor vehide.

[015]
[016] A release system 1 for a friction clutch 2 in a motor vehicle shown in the
Figure consists of a piston-cylinder unit 24 that is arranged concentricaily to a transmission input shaft 12. The friction clutch 2 consists of a flywheei 3, a dutch housing 8, a clutch disk 4 that features two friction linings 5, 6 and a contact spring 10 that is connected, via spacer bolts 9, to a contact disk 7. The contact spring 10 can be configured as a membrane or plate spring and is in connection

of the friction clutch 2, see the patent application publications DE 32 41 248 A1 and DE 197 03 333 B4. The piston-cylinder unit 24 features a cylinder 13 and a first piston 14 and a second piston 17, which delimit a first pressure chamber 16 and a second pressure chamber 19 of the piston-cylinder unit 24. The first piston 14 of piston-cylinder unit 24 serves as a working piston, where the second piston 17 of the cylinder-piston unit 24 represents a final position of the release system 1. In addition, the release system 1 features a hydraulic circuit, consisting of a pressure generating device 23, a pressure regulating means 21, a check valve 20, an overflow valve 27, a control valve 31, a pressure medium line 22, as well as a back flow line 26 and a container that serves as a pressure-medium sink 25. The devices already present in a transmission for supplying lubricante to the transmission can preferably be used as the pressure generating device 23 and the pressure medium sink 25. The pressure medium line 22 and the back flow line 26 are connected to the second pressure chamber 19 of the piston-cylinder unit 24, while the first pressure chamber 16 of the piston-cylinder unit 24 is connected to a further pressure medium iine 29. The pressure medium line 29 is connected to a pneumatic pressure generating device 28, for example a pneumatic pump. The control valve 31 in the hydraulic circuit is connected to an additional pressure medium line 30, which is connected to the pneumatic pressure generating means 28. The first pressure chamber 16 of the piston-cylinder unit 24 can therefore be pneumatically controlled, while the second pressure chamber 19 of the piston-cylinder unit 24 is hydrauiically controlled. Between the cylinder 13 and the first piston 14 of the piston-cylinder unit 24, at feast one sealing means 15 can be arranged. At least one sealing means 18 can also be arranged between

the cylinder 13 and the second piston 17 of the piston-cylinder unit 24. In order to operate the clutch, the first pressure chamber 16 of the piston-cylinder unit 24 is filled via the pneumatic pressure generating device 28 with a corresponding operating pressure. The second pressure chamber 19 of the piston-cylinder unit 24, which is filled with a hydraulic pressure medium, is closed during clutch operation by the check valve 20, which is arranged in the pressure medium line 22,

pressure that controls the clutch release, such that the back flow line 26, between the second pressure chamber 19 of the piston-cylinder unit 24 and the pressure medium sink 25, is interrupted. During the rest phase of the friction clutch 2, a specific pressure is maintained in the second pressure chamber 19 of the piston-cylinder unit 24 by way of an overflow valve 27 in the hydraulic back flow line 26. The pressure produces a rest force which corresponds to a rest force of a preloading spring. This ensures that the release bearing 11 abuts on the contact springs 10 of the clutch 2, which means that a preloading spring can be dispensed with. If wear occurs between the contact disk 7 and the friction linings 5, 6. the contact disk moves in the direction of the flywheel 3 and the position of the contact spring 10 changes. This produces a force on the release bearing 11, such that an axial force acts on the piston-cylinder unit 24. By way of this axial force, the pistons 14,17 will be displaced to the right in the drawing plane, until the change in position of the contact spring 10 of the friction clutch 2, that is due to wear and tear, is compensated for. As soon as a new balance of forces has been established, the pistons 14, 17 come to a standstill. The final position of the release system 1, which is realized by the second piston 17 of the piston-cylinder unit 24, is also displaced to the right In the drawing plane, where there is an axial displacement of the piston stroke with a clutch release. Based on this new position of the pistons 14,17, the first piston 14 of the piston-cylinder unit 24 performs its inward and outward movement with the usual piston stroke, because the first pressure chamber 16 of the piston-cylinder unit 24 can be supplied with a constant pressure via the pressure generating device 28. With continuing operation of the release system 1, the pistons 14, 17, due to increasing wear on the friction

clutch 2, will be increasingly displaced more to the right in the drawing plane.
With maximum clutch wear, the second piston 17 of the piston-cyfinder unit 24
reaches a final position at the transmission-side end of the cylinder 13. In this
position as well, the first piston 14 of the piston-cylinder unit 24 performs the usual
piston stroke.
[017] By way of the release system 1, the operating volume of the clutch release
path remains constant during the entire lifetime. Since the piston-cylinder unit 24

compensated for and clutch operation with a constant piston stroke can be carried out. In that way, the friction clutch 2 or the release system 1 demonstrates the same response during each operation, such that an equal short response time can be realized and maintained.

Reference numerals

1 release system
2 friction clutch
3 flywheel mass
4 clutch disk
5 friction lining
6 friction lining
( conraa QISK
8 clutch housing
9 spacer bolts
10 contact spring, membrane or plate spring
11 release bearing
12 transmission input shaft
13 cylinder
14 first piston or the piston-cyiinder unit, working piston
15 sealing means
16 first pressure chamber of the piston-cylinder unit
17 second piston of the piston-cylinder unit
18 sealing means
19 second pressure chamber of the piston-cylinder unit
20 check valve
21 pressure regulating means, throttle
22 pressure medium line
23 pressure generating device
24 piston-cylinder unit
25 pressure medium sink
26 back flow line
27 overflow valve
28 pressure generating device
29 pressure medium line
30 pressure medium line
31 control valve

CLAIMS
1. A releasing system (1) for a clutch and/or an accelerating coupling (2)
in a motor vehicle, consisting of a piston-cylinder unit (24) that features a
cylinder (13) arranged concentrically to a transmission input shaft (12), whereby
the releasing system (1) automatically compensates for wear and tear on the
clutch and/or accelerating coupling (2), characterized in that the piston-cylinder

19) in the cylinder (13) of the piston-cylinder unit (24) are bounded, which chambers can be acted on separately by a pressure medium.
2. The releasing system (1) according to claim 1, characterized in that the
first pressure chamber (16) of the piston-cylinder unit (24) can be pneumatically
controlled by a pressure generating device (28).
3. The releasing system (1) according to claim 1, characterized in that the
second pressure chamber (19) of the piston-cylinder unit (24) can be hydraulically
controlled by a pressure generating device (23).
4. The releasing system (1) according to one of the claims 1 to 3,
characterized in that at least one sealing means (15,18) is arranged respectively
between the cylinder (13) and the pistons (14, 17).
5. The releasing system (1) according to one of the claims 1 to 4,
characterized in that the clutch or acceleration coupling (2) can be operated by
way of a first piston (14) of the piston-cylinder unit (24), and the second piston (17)
of the piston-cylinder unit (24) represents a final position of the releasing system
(1)-
6. The releasing system (1) according to one of the previous claims,
characterized in that the second pressure chamber (19) of the piston-cylinder
unit (24) is connected via a pressure medium line (22) to the pressure generating
device (23) and via a back flow line (26) to a pressure medium sink (25).
7. The releasing system (1} according to claim 6, characterized in that the
pressure generating device (23) and the pressure medium sink (25) of the
releasing system (1) are preferably formed of devices for supplying lubricant to the
transmission that are already present In a transmission.

8. The releasing system (1) according to claim 6 or 7, characterized in that
a check valve (20), a pressure regulating means (21), and the pressure generating
device (23) are arranged in the pressure medium line (22).
9. The releasing system (1) according to claim 6, characterized in that an
overflow valve (27) and a control valve (31) are arranged in the back flow line (26).
10. The releasing system (1) according to one of the previous claims,
characterized in that a pressure generating device (28) is connected to the first

line (29) and connected to the control valve (31) via a pressure medium line (30).
11. The releasing system (1) according to one of the previous claims,
characterized in that the clutch and/or accelerating coupling (2) is configured as
a friction clutch.
12. A method of controlling a releasing system (1) of a clutch and/or
accelerating coupling (2) in a motor vehicle, consisting of a piston-cylinder unit (24)
arranged concentrically to a transmission input shaft (12), whereby the releasing
system (1) automatically compensates for wear and tear on a clutch, characterized
in that two pistons (14, 17) of the piston-cylinder unit (24) delimit two pressure
chambers (16, 19), which are controlled separately with a pressure medium.
13. The method according to claim 12, characterized in that the firat
pressure chamber (16) of the piston-cylinder unit (24) is pneumatically controlled
via a pressure generating device (28).
14. The method according to claim 12, characterized in that the second
pressure chamber (19) of the piston-cylinder unit (24) is hydraulically controlled via
a pressure generating device (23).
15. The method according to claims 12 to 14, characterized in that the
clutch and/or accelerating coupling is operated via the first piston (14) of the
piston-cylinder unit (24) and a final position of the releasing system (1) is produced
by way of the second piston {17) of the piston-cylinder unit (24).
16. The method according to one of the previous claims, characterized in
that the second pressure chamber (19) of the piston-cylinder unit (24), during a
clutch activation, is closed by a checK valve (20) in a pressure medium line (22)
and by a control valve (31) in a back flow line (26) as soon a corresponding

operating pressure acts on the first pressure chamber (16) of the piston-cylinder unit (24).
17. The method according to one of the previous claims, characterized in that during the rest phase of the clutch, a certain pressure is maintained by way of an overflow valve (27) in the back flow line (26) in the second pressure chamber (19) of the piston-cylinder unit (24).

cylinder unit (24) remains constant during the entire lifetime of the clutch and/or accelerating coupling (2).
19. A use of a piston-cylinder unit (24), which features two pistons (14,17),
in order to compensate for wear and tear of a clutch and/or accelerating
coupling (2).
20. A use of a device for supplying lubricant to a transmission, which
serves as a pressure generation device (23) and pressure medium sink (25) for an
hydraulic circuit of a releasing system (1) for a clutch and/or accelerating
coupling (2).