VALVE DEVICE OF A PNEUMATICALLY ACTUATABLE FRICTION CLUTCH

Abstract

A valve device (2), of a pneumatically actuatable friction clutch engageable by spring force, includes at least one inlet valve (16, 18) connected on the input side to a pressurized supply line and on the output side to an actuating cylinder of the friction clutch. A pressure-sustaining valve (20, 28) is upstream or downstream of the inlet valve and is designed as a check valve closing in the backflow direction. The pressure-sustaining valve is a springless check valve and includes a housing ring (22, 30) having a retaining basket (36), a closing element (24, 32), and a valve seat (26, 34). The closing element, in the depressurized state and with a positive pressure gradient is held in the retaining basket (36) of the housing ring (22, 30) and, with a negative pressure gradient is pressed out of the retaining basket (36) and against the valve seat (26, 34).

Claims

1. A valve device (2) for a pneumatically actuatable friction clutch, arranged in a vehicle between a drive motor and a gearbox, which friction clutch is configured to be engaged by means of spring force, the valve device comprising: at least one inlet valve (16, 18), which is connectable on an inlet side of the at least one inlet valve to a pressurized supply line and on an outlet side of the at least one inlet valve to a working chamber of an actuating cylinder of the friction clutch, the at least one inlet valve designed as a 2/2-way solenoid seat valve, wherein the working chamber of the friction clutch is configured for being connected to an outlet valve, which outlet valve is connectable on an inlet side of the outlet valve to the working chamber of the actuating cylinder and on an outlet side of the outlet valve to a vent outlet, and the outlet valve is designed as a 2/2-way solenoid seat valve, and a pressure-sustaining valve (20, 28), which is arranged upstream or downstream of the inlet valve (16, 18) and is designed as a check valve which closes in the backflow direction, wherein the pressure-sustaining valve (20, 28) is designed as a check valve without a valve spring and comprises: a housing ring (22, 30) having a retaining cage (36), a closing element (24, 32), and a valve seat (26, 34), wherein the closing element (24, 32) of the pressure-sustaining valve (20, 28), in a depressurized state and/or with a positive pressure gradient from the direction of an the outlet bore of the associated inlet valve (16, 18), is held by interlocking and frictional engagement in the the retaining cage (36) of the housing ring (22, 30) and, wherein the closing element (24, 32) of the pressure-sustaining valve (20, 28), with a negative pressure gradient in the direction of the outlet bore of the associated inlet valve (16, 18), can be lifted out of the retaining cage (36) and pressed against the valve seat (26, 34) to block pressurized air from exiting the working chamber through the at least one inlet valves.

2. The valve device as claimed in claim 1, in wherein the retaining cage (36) of the housing ring (22, 30) comprises retaining webs (38a, 38b, 38c) which are formed radially on the inside of the housing ring (22, 30) and are arranged in a manner distributed around the circumference, and wherein the retaining webs (38a, 38b, 38c) each have an inner surface (40a, 40b, 40c) in the form of a segment of a circle, which inner surfaces together form a retaining geometry, in the form of a segment of a sphere, of the retaining cage (36).

3. The valve device as claimed in claim 2, wherein the closing element (24, 32) of the pressure-sustaining valve (20, 28) is of spherical design and has a spring-elastic surface (44).

4. The valve device as claimed in claim 3, wherein the closing element (24, 32) is composed entirely of a spring-elastic material.

5. The valve device as claimed in claim 3, wherein the closing element (24, 32) has a core of a hard material, and wherein the core is coated with a spring-elastic material.

6. The valve device as claimed in claim 3, wherein the closing element (24, 32) has a central cavity which is surrounded in the form of a spherical shell by the spring-elastic material.

7. The valve device as claimed in claim 3, wherein the spring-elastic material of the closing element (24, 32) is rubber.

8. The valve device as claimed in claim 3, wherein the spring-elastic material of the closing element (24, 32) is silicone rubber.

9. The valve device as claimed in claim 1, wherein the pressure-sustaining valve (20, 28) is connected downstream of the inlet valve (16, 18) and is arranged adjacent the outlet bore of the inlet valve (16, 18), and wherein the edge of the outlet bore of the inlet valve (16, 18) serves as and/or is designed as a valve seat (26, 34) of the pressure-sustaining valve (20, 28).

10. The valve device as claimed in claim 1, wherein the closing element (24, 32) is pressed against the valve seat in response to a drop in pressure in the supply line when the inlet valve is open to maintain a pressurized state in the working chamber of the friction clutch.

11. The valve device as claimed in claim 10, wherein the closing element is held in the retaining cage and moved from the retaining cage without a spring force applied thereto.

12. The valve device as claimed in claim 1, wherein, during the positive pressure gradient when the pressure in the supply line is greater than the pressure in the working chamber, pressurized air flows past the closing element and through the holding ring toward the working chamber when the closing element is pressed against and held by the closing ring and the inlet valve is open.

13. The valve device as claimed in claim 12, wherein during the negative pressure gradient when the pressure in the supply line drops below the pressure in the working chamber, pressurized air flows through the holding ring and presses the closing element against the valve seat, and is blocked from flowing through the inlet valve when the inlet valve is open.

14. The valve device as claimed in claim 2, wherein apertures are defined circumferentially between the retaining webs, through which apertures pressurized air will flow when the closing element is held by the holding ring, the inlet valve is open, and the pressure in the supply line greater than the pressure in the working chamber.

15. The valve device as claimed in claim 14, wherein the apertures are arranged circumferentially around the closing element when the closing element is held in the retaining cage.

16. The valve device as claimed in claim 1, wherein the at least one inlet valve includes two inlet valves each having an associated connecting channel in communication with a common outlet channel for connecting to the working chamber of the friction clutch, wherein the connecting channels are connected in parallel to the outlet channel.

17. The valve device as claimed in claim 1, wherein the closing member remains retained in the holding ring during normal pressurization and depressurization of the working chamber of the friction clutch via controlled opening and closing of the inlet and outlet valves, and the closing element shifts out of retention from the holding ring only in response to a fault in the supply line in which the pressure in the supply line drops and backflow from the pressurized working chamber forces the closing element out of the holding ring.

18. The valve device as claimed in claim 1, wherein pressurized air from the supply line flows past the closing element and to the working chamber when the closing element is held in the retaining ring and the inlet valve is opened.

19. The valve device as claimed in claim 1, wherein the closing element is held in the retaining ring without a spring force applied thereto.

20. The valve device as claimed in claim 19, wherein the closing element is moved out of the retaining without a spring force applied thereto.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present disclosure is explained in greater detail below by means of an exemplary embodiment illustrated in the appended drawings. In the drawings:

[0017] FIG. 1 is a partial perspective sectional view illustrating a control module of a valve device of a pneumatically actuatable friction clutch having two inlet valves and two pressure-sustaining valves according to the present disclosure,

[0018] FIG. 2 a perspective sectional view and side view illustrating a housing ring and a closing element of the pressure-sustaining valve according to FIG. 1, and

[0019] FIG. 3 is a diagram illustrating time curves of a supply pressure and a clutch pressure.

DETAILED DESCRIPTION

[0020] A valve device 2, illustrated in FIG. 1, of a pneumatically actuatable friction clutch has two inlet valves 16, 18 and two pressure-sustaining valves 20, 28, which are arranged in a two-part housing 6, 8 of a control module 4. The inlet valves 16, 18 are designed as 2/2-way solenoid seat valves and are each arranged in one of two connecting channels 10, 12, which connecting channels 10, 12 are arranged in parallel between an inlet channel, not visible here, to which a pressurized supply line is connected, and an outlet channel 14, to which an actuating cylinder, not shown here, of the friction clutch is connected. The pressure-sustaining valves 20, 28 are designed as check valves without valve springs, which check valves close in the backflow direction and are in each case connected downstream of one of the inlet valves 16, 18 in the respective connecting channel 10, 12.

[0021] FIG. 1 illustrates the first inlet valve 16 and the associated first pressure-sustaining valve 20 in the installed state and the second inlet valve 18 and the associated second pressure-sustaining valve 28 in the uninstalled state above the housing 8. The inlet valves 16, 18 can be of identical construction or can have different opening cross sections. The pressure-sustaining valves 20, 28 are of identical construction and in each case comprise a housing ring 22, 30 with a retaining cage 36 (FIG. 2), a closing element 24, 32 and a valve seat 26, 34.

[0022] FIG. 2 illustrates, by way of example, the housing ring 30 and the closing element 32 of the second pressure-sustaining valve 28 on an enlarged scale. The closing element 32 of the pressure-sustaining valve 28 is of spherical design, and the retaining cage 36 of the housing ring 30 comprises retaining webs 38a, 38b, 38c, which are arranged radially on the inside of the housing ring 30 in a manner distributed around the circumference and have inner surfaces 40a, 40b, 40c, which are in the form of segments of a circle and form a retaining geometry, in the form of a segment of a sphere, of the retaining cage 36. There are sufficiently large apertures 42 around the circumference between the retaining webs 38a, 38b, 38c for the throughflow of compressed air in the open state of the pressure-sustaining valve 28.

[0023] The closing element 32 has a spring-elastic surface 44. For this purpose, the closing element 32 can be produced entirely from a spring-elastic material, such as rubber or silicone rubber, or can have a core made of a hard material which is coated with a spring-elastic material. In the installed state, the pressure-sustaining valves 20, 28 are in each case arranged close to the outlet bore of the associated inlet valve 16, 18 and use the edge of the relevant outlet bore as a valve seat 26, 34.

[0024] To disengage the friction clutch, the inlet valves 16, 18 are supplied with current and are thereby opened. The working chamber of the actuating cylinder of the friction clutch is thereby supplied with air from the supply line, as a result of which the friction clutch is disengaged against the restoring force of a closing or pressure spring. To engage the friction clutch, the inlet valves 16, 18 are switched off and thereby closed again, and outlet valves, not shown here, designed as 2/2-way solenoid seat valves, are supplied with current and thereby opened. The working chamber of the actuating cylinder of the friction clutch is thereby vented into a vent line leading to a vent outlet, as a result of which the friction clutch is engaged again under the action of the closing or pressure spring, this being known per se to a person skilled in the art.

[0025] In the unpressurized state and with a positive pressure gradient, that is to say when the pressure in the supply line is higher than in the working chamber of the actuating cylinder, the closing element 24, 32 of the respective pressure-sustaining valve 20, 28 is held by interlocking and frictional engagement in the retaining cage 36 of the housing ring 22, 30. In the case of a negative pressure gradient, that is to say when the pressure in the supply line is lower than in the working chamber of the actuating cylinder, this being established in the case of a drop in the supply pressure in the supply line caused by a fault, the closing element 24, 32 is pushed out of the retaining cage 36 and pressed against the respective valve seat 26, 34 of the inlet valves 16, 18. In this way, the connecting channels 10, 12 are blocked and release of air from the actuating cylinder and thus unintentional engagement of the friction clutch is prevented.

[0026] In the diagram shown in FIG. 3, the effect of the pressure-sustaining valves 20, 28 is illustrated on the basis of the curves of the supply pressure pv which is present in the supply line and of the clutch pressure p.sub.K which is effective in the working chamber of the actuating cylinder of the friction clutch, over the time t in seconds s. Up to time t = 10 s, the supply pressure pv is increased three times from 0 Pa to about 3 × 10.sup.5 Pa and reduced again to 0 Pa. When the inlet valves 16, 18 are open and the pressure-sustaining valves 20, 28 are not present or active, the clutch pressure p.sub.K follows the supply pressure p.sub.v with a delay of approximately 0.5 s when air is admitted to the actuating cylinder and almost without any delay when the actuating cylinder is vented.

[0027] From time t = 10 s, from which the supply pressure pv rises again from 0 Pa to approximately 3 × 10.sup.5 Pa, the pressure-sustaining valves 20, 28 are present and active. The inlet valves 16, 18 are then opened at time t = 11.5 s, with the result that air is admitted to the working chamber of the actuating cylinder and the friction clutch is disengaged. After the supply pressure pv drops to 0 Pa at time t = 14 s as a result of a fault, the pressure-sustaining valves 20, 28 close automatically, with the result that the clutch pressure p.sub.K drops by a pressure difference Δp of approximately 0.2 × 10.sup.5 Pa as a result of the switching time but is then kept very largely constant over a period of time Δt of approximately 10 seconds. In a starting process with the drive engine running and the starting gear engaged, this period of time is sufficient by far to disengage the starting gear and/or to stop the drive engine. In such a starting situation, the effect of the pressure-sustaining valves 20, 28 can thus reliably prevent uncontrolled abrupt starting of the relevant vehicle.

[0028] FIG. 3 also shows that the pressure-sustaining valve 20, 28 without a valve spring advantageously completely ignores a certain, comparatively small drop in the clutch pressure p.sub.k before it performs its function as a check valve. In the example presented, this pressure difference Δp is approximately 0.2 × 10.sup.5 Pa at time t = 14 s at an outlet pressure of 3 × 10.sup.5 Pa. Such a pressure drop does not yet lead to closing of the friction clutch.

[0029] As a result of the spring-elastic surface 44, the closing elements 24, 32 conform in a form-fitting manner to the inner surfaces 40a, 40b, 40c of the retaining webs 38a, 38b, 38c of the housing rings 22, 30 in the open state of the pressure-sustaining valves 20, 28 and to the edges, acting as valve seats 26, 34, of the outlet bores of the inlet valves 16, 18 in the closed state of the pressure-sustaining valves 20, 28. It is therefore possible for the housing rings 22, 30 and retaining webs 38a, 38b, 38c of the pressure-sustaining valves 20, 28 to be of relatively simple design and to be produced at low cost. Moreover, as a result, no mechanical fine machining of the inlet valves 16, 18 in the region of the bore edges 26, 34 of the outlet bores is required. Because the pressure-sustaining valves 20, 28 are closed only in the event of a very rarely occurring pressure drop in the supply pressure pv while the actuating cylinder of the friction clutch is being supplied with air, this type of construction of the pressure-sustaining valves 20, 28 is largely free of wear in comparison with conventional check valves and is therefore very functionally reliable.

[0030] While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

[0031] Reference signs [0032] 2 valve device [0033] 4 control module [0034] 6 first part of the housing [0035] 8 second part of the housing [0036] 10 first connecting channel [0037] 12 second connecting channel [0038] 14 outlet channel [0039] 16 first inlet valve, 2/2-way solenoid seat valve [0040] 18 second inlet valve, 2/2-way solenoid seat valve [0041] 20 first pressure-sustaining valve, check valve [0042] 22 first housing ring [0043] 24 first closing element, ball [0044] 26 first valve seat, bore edge [0045] 28 second pressure-sustaining valve, check valve [0046] 30 second housing ring [0047] 32 second closing element, ball [0048] 34 second valve seat, bore edge [0049] 36 retaining cage [0050] 38a first retaining web [0051] 38b second retaining web [0052] 38c third retaining web [0053] 40a first inner surface [0054] 40b second inner surface [0055] 40c third inner surface [0056] 42 apertures between retaining webs [0057] 44 surface of the closing element [0058] P pressure [0059] p.sub.K clutch pressure [0060] p.sub.v supply pressure [0061] t time, point in time [0062] Δp pressure difference [0063] Δt period of time