GB2323906A

GB2323906A - A clutch actuator having a control valve arrangement which allows simplified maintenance

Info

Publication number: GB2323906A
Application number: GB9800240A
Authority: GB
Inventors: Joachim Linder; Jorg Willert; Thomas Otto
Original assignee: Mannesmann Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1997-01-08
Filing date: 1998-01-06
Publication date: 1998-10-07
Anticipated expiration: 2018-01-06
Also published as: FR2758168B1; ES2151797A1; JPH10196679A; ES2151797B1; GB9800240D0; FR2758168A1; GB2323906B; JP2887127B2; BR9800268A

Abstract

A clutch actuator (10, fig 1), for a motor vehicle, comprises a pneumatic cylinder 14a having a release bearing (32, fig 1) and a hydraulic positioning servo with a control valve 42a mounted on the cylinder 14a so that it may be simply maintained, inside or outside a housing bell, independent of the cylinder 14a. A valve member 94a is connected to the cylinder 14a by a coupling 160a which does not transmit tilting forces to the valve member 94a. The control valve 42a is switched, by a clutch pedal 62a, between two control states, in the first control state cylinder 14a is pressurized by source 51 and in the second state the cylinder is depressurized through opening 70a. Switching of the control valve depends upon an actual value representing the actual position of the bearing (32, fig 1) and a command value representing a reference position of the bearing (32, fig 1). The valve member 94a which moves with cylinder 14a provides, because of its position relative to housing 40a, the actual value and the position of another valve member 92a provides the command value. A differential value associated with the actual value and the command value is represented by the position of the valve members relative to each other. Each valve member 92, 94a and 97a are capable of moving relative to each other and relative to the housing 40a and the control valve 42a may be in the form of a rotatory valve (see figs 5 to 9).

Description

2323906 1 CLUTCH ACTUATING DEVICE The invention relates to an actuating

device for a friction clutch located in the drive train of a motor vehicle, in particular a commercial motor vehicle, between an internal 5 combustion engine and a gearbox housing.

An actuating device is known for example from DE 33 21 578 C2.

In this device a release bearing able to move essentially coaxially with respect to the friction clutch, serves to operate the friction clutch. A positioning servo with a pressure medium cylinder arrangement acts on the release bearing and the cylinder arrangement can be actuated by way of a control valve connected to a source of pressure medium, depending on a command value representing a reference position and an actual value representing the axial position of the release bearing. The known actuating device uses a vacuum servo power amplifier as the positioning servo. The servo power amplifier constructed in the manner of a vacuum braking force amplifier is constructed integrally with a pneumatic power cylinder and the control valve and is located outside the housing in the form of a bell. Two working chambers of the pneumatic power cylinder are separated from each other by a piston guided to move axially and a resilient diaphragm. one working chamber constructed as the vacuum chamber is connected to an intake manifold system of the internal combustion engine. The other working chamber serving as a control chamber can be connected by means of the control valve either to the vacuum chamber or by way of a pressurecompensating opening to the atmosphere. The actuation of the vacuum servo power amplifier takes place by way of a control rod striking against a valve body of the control valve. The control rod is axially displaced by way of a cam driven by an electric motor. An axial displacement of the control rod results in operation of the control valve so that the piston follows the movement of the control rod in a poweramplified manner. The 2 movement of the piston acts by way of a hydraulic master cylinder on a slave cylinder connected to the master cylinder and located outside the housing bell. The slave cylinder in turn acts on a release lever associated with the release bearing. An emergency actuation of the clutch when the internal combustion engine is stationary, thus when there is no vacuum, is possible due to the fact that the control rod is able to act by way of the valve body of the control valve directly on the piston.

The control valve comprises a valve body, which cooperates with a resilient valve seat. Provided in the valve seat is a connecting channel, by way of which the connection between the control chamber and the ambient air takes place, unless the valve body is pressed against the resilient valve seat, in order to close the connecting channel. A further connecting channel connects the control chamber to the vacuum chamber.

Furthermore, an actuating device of the aforementioned type is 20 known, which comprises a pneumatic power cylinder as the pressure medium power cylinder arrangement. The actuating device is located externally on the housing bell as an integral unit comprising the pneumatic power cylinder, a hydraulic slave cylinder and the control valve. The piston of the pneumatic power cylinder is located on a rod member forming the piston of the hydraulic slave cylinder and the rod member is connected to a plunger, which extends into the inside of the housing bell and acts on a release lever associated with the release bearing.

Connected to the hydraulic slave cylinder is the master cylinder able to be actuated by a clutch pedal and providing a control input to the control valve. Depending on the hydraulic pressure prevailing at the control input, the control valve controls the supply of compressed air to the pneumatic power cylinder or the discharge of air from the pneumatic power cylinder so that a 3 specific hydraulic pressure determined by a compression spring arrangement prevails at the control input. The hydraulic slave cylinder in this case serves as a measuring cylinder, which monitors the position of the rod member and thus indirectly the position of the release bearing. Upon actuation of the master cylinder, by way of the hydraulic slave cylinder serving as a measuring cylinder, force is exerted directly on the rod member and thus on the release bearing, in addition to the actuating forces of the pneumatic power cylinder on account of the supply of compressed air to the latter.

It is desirable to provide an actuating device of the aforementioned type, in which the pressure medium power cylinder arrangement is located within the housing bell. A possible construction is characterised by the fact that the pressure medium power cylinder arrangement is constructed for exerting a force essentially coaxial with the axis of the clutch, on the release bearing. For this purpose the pressure medium power cylinder arrangement can comprise a pressure medium ring cylinder essentially concentric with the axis of the clutch.

In a device of this modified type, in principle, a control valve of the afore-described type could be used with a hydraulic slave cylinder serving as the measuring cylinder, by which, upon actuation of the control valve, force is exerted on the release bearing. However, this would have the drawback that in the case of a pressure medium power cylinder arrangement constructed for exerting on the release bearing a force essentially coaxial with the axis of the clutch, due to the measuring cylinder tilting moments are exerted on the release bearing, unless the measuring cylinder is also constructed to exert forces essentially coaxial with the axis of the clutch on the release bearing, for example is constructed as a measuring ring cylinder essentially concentric with the axis of the clutch. Such a measuring ring 4 cylinder would have the disadvantage that in the case of leakages of the hydraulic measuring cylinder, exchanging the measuring cylinder would necessitate the disconnection of the housing bell from the internal combustion engine. On the other hand, if one used a measuring cylinder located for example on the side of the pressure medium power cylinder arrangement, then the tilting moments exerted in this case on the release bearing imply correspondingly higher mechanical expenditure, in order to absorb or compensate for these tilting moments.

In comparison therewith it is an object of the present invention to make available an actuating device of the aforementioned type with a pressure medium power cylinder arrangement located within the housing bell, in which no appreciable forces, in particular tilting forces, are exerted on the part of the control valve (and a measuring arrangement or the like possibly associated with the control valve) on the release bearing apart from by way of the pressure medium power cylinder arrangement by means of a supplied pressure medium.

A further object of the present invention lies in making available an actuating device of the aforementioned type, which allows simplified maintenance (independently of the arrangement of the pressure medium power cylinder arrangement inside or outside the housing bell) of the control valve or components associated with the latter.

In order to achieve at least one of these objects, it is proposed according to the invention that the control valve arrangement is adjustable between a first control state connecting the pressure medium power cylinder arrangement to the source of pressure medium and a second control state connecting the pressure medium power cylinder arrangement to a pressurecompensating opening. The valve arrangement can be switched between the two control states depending on a differential value associated with the actual value and the command value. The valve arrangement comprises two valve members able to move relative to each other and relative to a valve housing and the command value is represented by the position of a first of the two valve members, the actual value is represented by the position of a second of the two valve members relative to the valve housing and the differential value is represented by the position of the two valve members relative to each other.

The construction according to the invention of the control valve with two valve members, whereof the positions respectively represent a separate value determining the control state of the control valve, facilitates decoupling between the "actual value side" of the positioning servo on the one hand and the "command value side" of the positioning servo on the other hand, so that when changing the command value of the "command value side" of the positioning servo, no appreciable variable forces are exerted on the release bearing apart from by way of the pressure medium power cylinder by means of a supplied pressure medium.

Then also, no appreciable tilting moments are exerted on the release bearing by the "command value side" of the positioning servo. Mechanical expenditure for absorbing or compensating for tilting forces may thus be dispensed with, due to which the actuating device according to the invention can be produced more economically.

Since the actual value and the command value are respectively represented by the position of a specific valve member, an uncomplicated coupling of the control valve to a command value transducer unit on the one hand and to an actual value transducer unit on the other hand, is possible. The control valve may thus be constructed in a maintenance- friendly manner, for example so that it can be exchanged without great expense.

6 The valve arrangement may be adjustable depending on the differential value in a third control state, in which the pressure medium power cylinder arrangement is preferably closed substantially in a pressure medium-tight manner, thus simultaneously connected neither to the pressure medium source nor to the pre s sure- compens at ing opening. A certain state or position of the valve arrangement is then associated with the third control state. However, the third control state may also be distinguished due to the fact that the valve arrangement alternately adopts the position associated with the first control state and the position associated with the second control state, so that the pressure medium power cylinder arrangement is not closed in a pressure mediumtight manner.

It is further proposed that the control valve arrangement has a first signal connection for receiving a command signal indicating the command value, in particular from a clutch pedal and a second signal connection for receiving an actual value signal indicating the actual value, from a transducer associated with the release bearing. Preferably the command signal and the actual value signal then act respectively independently of the respective other signal on exactly one valve member of the two valve members directly, namely the command signal on the first valve member and the actual value signal on the second valve member. The fact that the signals act respectively on exactly one valve member directly, does not preclude the fact that the signals act by way of intermediate components on the respective valve member. The term "act directly" thus serves solely to distinguish between "indirect" actions, in particular of the command signal on the second valve member by way of the positioning servo so that namely by corresponding switching-over of the control valve between the control states by means of the pressure medium power cylinder arrangement it is ensured that 7 the actual value is adjusted corresponding to the input by the command value and also the position of the second valve member representing the actual value changes in a corresponding manner.

The actual value signal may be a hydraulic, pneumatic, mechanical or electrical signal represented in particular by a pressure, a volume, a force, a displacement, an angle, a current intensity or a voltage, in which case possibly associated with the second signal connection are converter means for converting the actual value signal into the actual value.

It is also proposed that the positioning servo comprises a mechanical position-regulating arrangement with a transducer connected or able to be connected mechanically and directly or 1S indirectly to monitor the position of the release bearing. In this connection it is preferred that the transducer acts on the second valve member, in particular is kinematically connected or can be kinematically connected to the latter. The second valve member is preferably essentially rigidly coupled or can be coupled by way of a coupling member if necessary integral with the latter, to the release bearing or the release bearing side of the pressure medium power cylinder arrangement. However, it is also possible that the second valve member, by way of a coupling member preferably essentially rigidly coupled to the latter, if necessary integral with the latter, pretensioned or able to be pre-tensioned against the release bearing or the release bearing side of the pressure medium power cylinder arrangement, is coupled or can be coupled to the latter.

The command signal may be a hydraulic, pneumatic, electrical or optical signal represented in particular by a pressure, a volume, a force, a displacement, an angle, a current, a voltage or a light intensity, in which case if necessary converter means for converting the command signal into the command value are 8 associated with the first signal connection. Preferably the command signal is a pneumatic or hydraulic and most preferably a hydraulic, command signal. In this connection it is proposed that the converter means for converting the pneumatic or hydraulic command signal comprise a piston pre-tensioned in particular by a spring, which is preferably coupled or can be coupled to the first valve member, in particular is integral therewith.

In addition to the first and to the second valve member, the valve arrangement may comprise an auxiliary valve member able to move relative to the valve housing, which member cooperates with the first and/or second valve member in order to provide at least one of the control states.

The auxiliary valve member preferably comprises an action section associated with the first valve member, on which the first valve member acts for the entrairiment of the auxiliary valve member and/or for interrupting at least one pressure medium connection within the control valve, in particular for interrupting the pressure medium connection between the pressure medium power cylinder arrangement and the pre s sure-compens ating opening.

The auxiliary valve member could comprise an action section associated with the second valve member, on which the second valve member acts for the entrainment of the auxiliary valve member and/or for interrupting at least one pressure medium connection within the control valve, in particular for interrupting the pressure medium connection between the pressure medium source and the pressure medium power cylinder arrangement and/or for blocking a pressure medium connection between the pressure medium source and the pressure-compensating opening, which is structurally possible in principle, if necessary.

9 Due to the fact that the auxiliary valve member cooperates at the time of production or interruption of at least one, preferably several pressure medium connections within the control valve, the conditions, which must be fulfilled for producing or interrupting the respective pressure connection, can be preset particularly exactly and if necessary independently of the remaining pressure medium connections.

medium Pre-tensioning means, in particular pre-tensioning means acting between the second valve member and the auxiliary valve member, can be provided, to pre-tension the auxiliary valve member in the direction for the action of the second valve member on the associated action section of the auxiliary valve member and/or in the direction for the action of the first valve member on the associated action section of the auxiliary valve member, in particular in order to close the pressure medium connection in a basic state of the actuating device, in which the clutch is not actuated. The pre-tensioning of these pre-tensioning means is chosen to be sufficiently great in order that a seal is still guaranteed and at the same time in order to keep the tilting force possibly produced by the pre-tensioning, minimal. The first and the second valve member and possibly the valve housing may respectively comprise at least one abutment or engagement section for limiting the range of movement of the two valve members relative to each other and possibly for limiting the range of movement of at least one of the valve members relative to the valve housing. Preferably, in the case of abutment of associated abutment sections of the first and second valve member one on the other, a pressure medium connection within the control valve, in particular the pressure medium connection between the pressure medium source and the pressure medium power cylinder arrangement is established.

Furthermore it is proposed that pre-tensioning means acting between the first and the second valve member are provided, in particular in order to keep the pressure-compensating opening open in the basic position. The pre-tensioning of these pretensioning means should be chosen to be sufficiently great in order to still overcome the frictional forces occurring and at the same time to keep the tilting force produced if necessary by the pre-tensioning minimal. The tension of the pretensioning means active between the first and the second valve member is preferably maximum at the time of abutment of abutment sections associated with each other, of the first and second valve member, against each other.

According to one advantageous construction of the actuating 15 device according to the invention, one of the members - first valve member and second valve member - in particular the second valve member, comprises at least one section forming a control edge, which cooperates with at least three pressure medium openings in the other valve member and in the valve housing. These openings may comprise, in particular, a pressure medium opening in the other valve member and two pressure medium openings in the valve housing. Thereby in at least one relative position of the two valve members relative to each other, at the time of a movement of one valve member relative to the other valve member in one direction due to the movement of at least one control edge past at least one of the pressure medium openings, in particular of the pressure medium opening in the other valve member, is produced or interrupted a first pressure medium connection within the control valve. In particular the pressure medium connection between the pressure medium source and the pressure medium power cylinder arrangement is established or interrupted to produce or interrupt another pressure medium connection within the control valve, in particular the pressure medium connection between the pressure- 11 compensating opening and the pressure medium power cylinder arrangement. In this construction, an auxiliary valve member cooperating with the first and/or second valve member and able to move relative to the valve housing is preferably dispensed 5 with.

One of the valve members - first valve member and second valve member - in particular the first valve member, may comprise at least one in particular pin-like engagement section, which engages in an associated slot-like recess in the other valve member, the recess being limited at both ends by stops, for limiting the range of movement of the two valve members relative to each other.

It is proposed as being particularly preferred that the control valve (independently of the remaining structural features) in a basic state of the actuating device without actuation of the clutch, adopts the control state connecting the pressurecompensating opening to the pressure medium power cylinder arrangement. If, when the pressure medium power cylinder arrangement is constructed as a pneumatic power cylinder arrangement, venting of the cylinder arrangement by way of the pressure-compensating opening with respect to the atmosphere occurs, then in the basic state of the actuating device, ambient pressure prevails within the cylinder arrangement, so that undesired pressure variations within the cylinder arrangement owing to foreign influences (for example temperature) are precluded.

The first and the second valve member and - in so far that it is provided - possibly the auxiliary valve member may be mounted to be displaceable along a valve axis in a recess of the valve housing, in which case the actual value and the command value are represented by axial positions of the respective valve 12 member. of the members - f irst valve member, second valve member and possibly auxiliary valve member - at least one can be constructed at least in certain regions as a ring member coaxial with the axis of the valve and surrounds at least one other of these valve members, at least in regions, radially on the outside.

The recess in the valve housing is preferably a ring-shaped recess, which at a radial distance comprises ring-shaped cylindrical walls extending coaxially which extends around a tube member stationary with respect to the valve housing, preferably integral with the latter and extending coaxially with respect to the valve axis. The tube member comprises in the region of its free end, a pressure medium passage opening open in particular in the axial direction, as part of at least one pressure medium connection within the control valve, in particular the pressure medium connection between the pressure medium power cylinder arrangement and the pressure medium source and/or the pressure medium connection between the pressure medium power cylinder arrangement and the pre s sure-compensating opening. It is also proposed that the first valve member comprises a ring section, which surrounds the tube member at least in regions radially on the outside, in which case preferably at least one ring-shaped sealing member acts in a sealing manner between the ring section and the tube member.

Furthermore it is proposed that at least one ring-shaped sealing member acts in a sealing manner between the radially outer ring- shaped cylindrical wall of the ring-shaped recess and the first valve member, in particular the ring section.

In particular it is preferred that the first valve member comprises a tube section axially adjoining the ring section, which tube section surrounds the tube member at least in regions, radially on the outside, in which case preferably at least one ring-shaped sealing member acts in a sealing manner between the tube section and the tube member.

The auxiliary valve member constructed as a ring member may surround the first valve member, in particular the tube section, at least in regions, radially on the outside.

it is proposed as particularly advantageous that the first valve member comprises a closure section adjoining the tube section, extending substantially in the radial direction and covering the pressure medium passage opening in the free end of the tube member in the axial direction. The first valve member acts on the associated ring-shaped and radially inwardly projecting action section of the auxiliary valve member for entrainment and/or for interrupting the at least one pressure medium connection. The action section of the auxiliary valve member may define a pressure medium passage opening in the radial direction, which is part of a pressure medium connection within the control valve, and which, in particular is associated with the pressure-compensating opening or is identical to the latter.

In connection with the construction of the first valve member with the closure section, it is particularly preferred that the first valve member, in the end region of the tube section adjacent to the closure section, comprises at least one pressure medium passage opening, open in particular in the radial direction, as part of at least one pressure medium connection within the control valve, in particular the pressure medium connection between the pressure medium power cylinder arrangement and the pressure medium source and/or the pressure medium connection between the pressure medium power cylinder arrangement and the pressure-compensating opening.

14 The second valve member constructed as a ring member may surround the first valve member and/or if necessary the auxiliary valve member at least in regions, radially on the outside. At least one ring-shaped sealing member may act in a sealing manner between the second valve member and the auxiliary valve member.

Furthermore, at least one ring-shaped sealing member may act in a sealing manner between the radially outer ring-shaped cylindrical wall of the ring recess and the second valve member.

It is proposed that formed radially between the tube section and the auxiliary valve member and/or radially between the second valve member and a ring-shaped cylindrical wall of the valve housing defining the recess radially on the outside is a respective pressure medium channel, in particular pressure medium ring channel, which is part of a pressure medium connection within the control valve, in particular the pressure medium connection between the pressure medium source and the pressure medium power cylinder arrangement. In this connection it is preferred that provided between the two pressure medium channels is a pressure medium connection able to be interrupted by action of the second valve member on this associated action section of the auxiliary valve member, which pressure medium connection preferably comprises at least one pressure medium passage opening open in the radial direction, in the second valve member and/or a ring-shaped chamber defined by the tube section, the auxiliary valve member or the second valve member.

As regards the coupling of the pressure medium source and/or a command signal generator to the control valve, it is proposed that a valve connection connected to the pressure medium source and/or a valve connection connected to the command signal generator respectively comprise a bore in the valve housing, is opening into the recess, in particular directed radially. The bore of the valve connection connected to the command signal generator preferably opens into the recess in the region of a recess base closing off the recess on one axial side, in which case lying opposite the recess base is the ring section of the first valve member serving as a piston for the converter means. The bore of the valve connection connected to the pressure medium source preferably opens into the recess in an end region of the recess adjoining a recess opening, which is open in the axial direction.

As regards the coupling of the pressure medium power cylinder arrangement to the control valve, it is proposed as particularly preferred that a valve connection connected to the pressure medium power cylinder arrangement comprises a first bore opening into the recess, extending in particular through the tube member, as well as preferably a second bore, which adjoins the first bore and extends in the base of the recess.

According to one advantageous variation of the actuating device according to the invention, the valve members, in particular the first and the second valve member, may be mounted to rotate about a valve axis in a recess in the valve housing, in which case the actual value and the command value are represented by rotary positions of the respective valve member.

Of the members - f irst valve and second valve member - one, in particular the second valve member, may comprise a ring section coaxial with the axis of the valve, which surrounds the other valve member of the two valve members at least in regions, radially on the outside. In this connection it is particularly preferred that the ring section of one valve member surrounded radially on the outside by an inner peripheral surface of the valve housing, defining the recess, comprises at least two 16 openings extending in the peripheral direction, offset with respect to each otherin the peripheral direction, separated from each other by a respective section of the ring section and open radially towards the inside and radially towards the outside. In the valve housing there are at least two bores opening into the recess and directed in particular radially, the orifices of the bores being offset with respect to each other in the peripheral direction and in at least one rotary position of one valve member respectively covering another of the openings at least partly. In the other valve member is at least one connecting channel, in particular a through-bore, which in at least one relative rotary position of the two valve members with respect to each other is open with respect to two of the openings, in particular in such that two apertures of the through-bore are covered at least partly by respectively one other of the openings.

For this purpose, it is furthermore provided as particularly advantageous that in each case exactly three bores, in each case exactly three openings and exactly one connecting channel, in particular one through-hole extending radially are provided. In this case, in at least one rotary position region of the two valve members relative to each other and relative to the valve housing by way of two of the bores, two of the openings and the 25. connecting channel, a pressure medium connection is produced between the pressure medium source and the pressure medium power cylinder arrangement. In at least one other rotary position region of the two valve members relative to each other and relative to the valve housing, by way of two of the bores, two of the openings and the connecting channel, a pressure medium connection is produced between the pressure medium power cylinder arrangement and the pressure-compensating opening.

17 The sections of the ring section separating the openings from each other, are preferably dimensioned so that in at least one relative rotary position of the two valve members with respect to each other and/or in at least one rotary position of one valve member relative to the valve housing, at least one channel opening, in particular an aperture of the through-hole in the other valve member and/or at least one of the apertures of the bores in the valve housing is closed by a respective section of the ring section forming in particular a control edge.

Due to the last-mentioned measures, it can be achieved in a simple manner that in at least one rotary position of the two valve members relative to each other and relative to the valve housing, neither a pressure medium connection between the pressure medium power cylinder arrangement and the pressure medium source, nor a pressure medium connection between the pressure medium power cylinder arrangement and the pressure compensating opening is produced. Also, without an additional auxiliary valve member able to be moved with respect to the housing, and thus, by means solely of the first and of the second valve member, three control valve states can be realised, namely "a pressure medium connection between the pressure medium source and the pressure medium power cylinder arrangement", "a pressure medium connection between the pressure medium power cylinder arrangement and the pressure-compensating opening" and "a closure of the pressure medium power cylinder arrangement in a substantially pressure medium- tight manner.

The apertures of the three bores in the valve housing are preferably arranged with the same peripheral angle at a distance apart and preferably respectively cover an equallylarge peripheral angular region. Correspondingly, it is preferred for the three openings in the ring section of one valve member to respectively cover an equally large peripheral angular region 4 18 and to be arranged with the same peripheral angle at the same distance apart. Preferably the apertures of the three bores and correspondingly the three openings are essentially not offset with respect to each other in the axial direction.

Of the three bores, preferably following each other in succession in a predetermined direction of rotation is a bore associated with the pre s sure- compens at ing opening, a bore associated with the pressure medium source and a bore associated with the pressure medium power cylinder arrangement. In the basic state of the actuating device, an aperture of the throughbore in the first valve member lies approximately opposite the bore associated with the pressure-compensating opening and a section of the ring section of the second valve member, forming a control edge, is offset in the direction of rotation with respect to the bore associated with the pres sure- compens at ing opening, but is closely adjacent to the latter. For actuating the clutch, the first valve member is able to rotate in the direction of rotation with respect to the rotary position of the basic state, in particular to the maximum extent approximately as far as a rotary position, in which the aperture of the through-bore lies approximately opposite the bore associated with the pressure medium source.

The recess receiving the valve members may preferably be constructed as a through-bore in the valve housing extending at right angles to the direction of movement of the release bearing, at one end of which the first valve member is accessible, in particular projects, and at the other end of which the second valve member is accessible, in particular projects. In this connection, it is proposed as particularly preferred that one end section of the second valve member projecting from the through-bore in the valve housing supports a rigidly coupled bracket as the coupling member, which acts on 19 the release bearing or the release bearing side of the pressure medium power cylinder arrangement. In particular spring means can act on the bracket and the valve housing and preferably comprises a leg spring which is located around the end section, is pre-tensioned against the latter, or is connected to the latter in a form-locking manner (approximately by means of a slot, in which an engagement section of the bracket engages), so that the bracket is positively entrained. A linear movement of the release bearing or of the release bearing side of the pressure medium power cylinder arrangement can then be converted by way of the bracket into a rotary movement of the second valve member.

In so far that converter means for converting a pneumatic or 15 hydraulic command signal are provided, the spring-pre-tensioned piston of the converter means may be part of a cylinder-piston arrangement, which is separate with respect to the valve members. In this case, the piston is preferably movable in one direction, which extends substantially at right angles to the axis of the valve and a linear movement of the piston can be converted by way of a coupling arrangement acting on the first valve member, in particular a toggle lever arrangement, into a rotary movement of the first valve member.

In order to achieve high operational reliability of the control valve, surface sections of the valve housing, of the first and of the second valve member, bearing one against the other, may be constructed as sealing and/or sliding surfaces, and/or sealing means may be active in a sealing manner between the latter.

The afore-described construction of the control valve according to the variation with valve members mounted to rotate about an axis of the valve in a recess of the valve housing can be readily transferred to a control valve with valve members mounted to slide along an axis of the valve in a recess of the valve housing.

Generally it is true that the release direction of the pressure medium power cylinder arrangement and the release direction of the friction clutch may have any orientation with respect to each other. This is true not solely when the pressure medium power cylinder arrangement is located outside the housing bell and for example is located on the gearbox housing. Particularly for the case where the pressure medium power cylinder arrangement is located inside the housing bell, it is however frequently appropriate if the release direction of the pressure medium power cylinder arrangement and the release direction of the friction clutch are substantially parallel to each other, in which case preferably the axis of the clutch and the axis of the power cylinder arrangement essentially coincide.

The valve axis and the power cylinder arrangement axis may in principle have any orientation with respect to each other and do not need to have any point in common. However, it is preferred that the valve axis and the power cylinder arrangement axis are substantially parallel to each other or in projection on a plane substantially parallel to both axes, are substantially at right angles to each other.

The afore-described measures and preferred embodiments of the control valve or of the valve arrangement both in the case of valve members displaceable along the axis of the valve as well as valve members able to rotate about the axis of the valve respectively themselves and also jointly contribute to the control valve having a compact construction, high operational reliability and which is economical to produce. The control valve may be located completely within the housing bell or at 21 least partly within the housing bell and in the case where the housing bell is connected to the internal combustion engine and the gearbox, is accessible from outside, in particular can be removed. The actuating device can then be easily serviced and possibly repaired, without the housing bell generally formed by a section of a gearbox having to be released from the internal combustion engine. The control valve may be constructed in an integral manner with the pressure medium power cylinder arrangement. However, it is preferred that the control valve is a separate component in particular detachably located on the pressure medium power cylinder arrangement.

With regard to particularly high ease of maintenance, it is proposed as particularly preferred that a control valve component comprising the control valve is offset with respect to a power cylinder component comprising the pressure medium power cylinder arrangement, in a radial direction relative to the power cylinder arrangement axis and is detachably located on a radially outer section of the power cylinder component. In this connection it is particularly advantageous if the control valve component, after the release of possible fastening or/and coupling means acting between the two components, which are preferably accessible from at least one radial direction corresponding essentially to the radial direction, is removable from the power cylinder component substantially in the radial direction. The ease of maintenance resulting from this is noticeable both in the case of control valves located inside as well as outside the housing bell.

The pressure medium may be a pneumatic or hydraulic pressure medium. It is particularly preferred that the pressure medium is a pneumatic pressure medium, in which case the pressure medium source is preferably an excess pressure source supplying a higher pressure than ambient pressure.

22 The invention may be understood more readily, and various other aspects and features of the invention may become more apparent, from consideration of the following description.

Embodiments of the invention will now be described in detail hereafter, by way of examples only, and with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic, partial sectional, view of an actuating device constructed in accordance with the invention; Figure 2 is in a perspective, partial sectional view, of another actuating device constructed in accordance with the invention; Figures 3a, 3b, 4a, 4b are sectional views through a control 15 valve and a part of a pressure medium ring cylinder, of the device shown in Figure 2, and representing different operative states; Figure 5 is a perspective view of a further actuating device constructed in accordance with the invention; Figure 6 is a perspective part-sectional view of the control valve and the pressure medium ring cylinder arrangement of the device shown in Figure 5; Figure 7 is a sectional view through the control valve and the pressure medium ring cylinder arrangement, represented in Figure 5, the view being taken on line VII-VII of Figure 8.

Figure 8 shows a section through the control valve and the pressure medium ring cylinder arrangement represented in Figure 5, the view being taken on line VIII-VIII of Figure 7; Figure 9 is a section through the control valve represented in 30 Figure 5, the view being taken on line IX-IX of Figure 7; Figure 10 is a perspective partial sectional view, of a further embodiment of a control valve used in the device constructed in accordance with the invention, and corresponding to the embodiment shown in Figure 5 and 23 Figures lla and llb are sectional views of the control valve of Figure 10 in different operating states.

Figure 1 shows diagrammatically a device 10 constructedin accordance with the invention serves for actuating a friction clutch located in the drive train of a motor vehicle between an internal combustion engine and a gearbox in a bell-like housing 12. The actuating device 10 employs a pressure medium ring cylinder arrangement 14 constructed as a component, in this case a pneumatic power cylinder arrangement, which will be referred to hereafter also as the actuating cylinder component. The actuating cylinder component 14 comprises a pressure medium ring cylinder, in this case a pneumatic ring cylinder 16, which is formed by a ring-shaped cylindrical chamber 18 in a stationary body part 20 and a pneumatic ring piston member 22. The pneumatic ring piston member 22 is pre-tensioned by spring means 24 in the direction towards the clutch (not shown) and towards the left in Figure 1 and supports sealing rings 26 for sealing the ring-shaped cylinder chamber 18 of the pneumatic ring cylinder 16.

The pneumatic ring cylinder 16 and the pneumaticring piston member 22 are arranged coaxially with respect to an axis A of the clutch. The body part 20 possesses an axial bore, through which extends a transmission input shaft 28 coaxial with respect to the clutch axis A.

A ring section 30 of the pneumatic ring piston member 22 provided at the end of the ring piston member adjacentthe clutch forms an outer ring of a release bearing 32. The release bearing 32 furthermore comprises an inner ring 34 able to rotate with respect to the outer ring 30 and coupled with the clutch.

Rolling elements in the form of balls 36 facilitate relative rotation between the two rings 30 and 34. At the time of 24 actuation of the actuating device 10, the release bearing 32 acts in a known manner, in particular by way of diaphragm spring tongues on the clutch, in order to release the latter for interrupting the flow of power between the gearbox and the internal combustion engine.

The actuating cylinder component 14 supports a control valve unit as a component 40 releasably attached to the actuating cylinder component 14. The unit 40 comprises a control valve arrangement 42 shown only diagrammatically in Figure 1. The unit or control valve component 40 is located so that it projects through an associated opening 44 in the housing bell 12 beyond the outside of the bell and can be dismantled even when the housing bell 12 is connected to the internal combustion engine and the gearbox.

The control valve arrangement 42 is connected by way of a pneumatic line 46 within the control valve component 40, by way of a pneumatic connection 48 to the section of the control valve component 40 projecting beyond the outside of the housing bell 12 and by way of a further pneumatic line 50 to a pneumatic source 51. The control valve arrangement 42 is furthermore connected by way of a line 52 within the control valve component 40, to a connection 54 of the section of the control valve component 40 projecting beyond the outside of the housing bell 12 and by way of a further line 56 to a command signal transmitter unit 60. The command signal transmitter unit 60 is, in the present case, a clutch pedal arrangement 60 with a clutch pedal 62, which is designed for transmitting a command signal in the form of a hydraulic signal by way of the line 56, the connection 54 and the line 52 to the control valve arrangement 42. The lines 52 and 56 are correspondingly hydraulic lines, which are connected by way of the connection 54 constructed as a hydraulic connection.

The control valve arrangement 42 is furthermore connected by way of a pneumatic line 64 within the control valve component 40 and a pneumatic line 66 within the actuating cylinder component 14 to the ring cylinder chamber 18 of the pneumatic ring cylinder 16. Furthermore, the control valve arrangement 42 is connected by way of a pneumatic line 68 within the control valve component to a pressure- compensating opening 70 in an external surface of the control valve component 40 adjacent the clutch.

Axial displacement of the release bearing 32 is transferred to the control valve arrangement 42 by way of mechanical coupling members 72 and 74 as a mechanical actual value displacement signal, as illustrated diagrammatically by the connection 76 (shown in broken line) within the control valve component 40.

For this purpose, the rod-like coupling member 74 projecting into the control valve component 40 is kinematically coupled to a valve member of a valve arrangement comprising three valve members. The three valve members of the valve arrangement are displaceable in the control valve component 40 parallel to the axis A of the clutch. Of the three valve members, a first valve member is associated with the command signal transmitter unit 60, a second (the already mentioned) valve member is associated with the release bearing 32 and kinematically coupled by way of the coupling members 72 and 74 to the latter as regards axial movement, and a third valve member, referred to hereafter as the auxiliary valve member, serves, together with the first and the second valve member, to achieve different control states of the control valve arrangement 42. For a more detailed construction of the control valve arrangement 42, reference should be made to the embodiment of Figures 2 to 4, whereof the control valve arrangement 42a corresponds essentially to the control valve 42 of Figure 1, with regard to method of operation and basic construction. In the case of the control valve arrangement 42, 26 however, it could also readily be a control valve with only two movable, in particular rotatable, valve members. In this respect reference is made to the embodiment of Figures 5 to 9, whereof the control valve arrangement 42b can be used with slight modifications as regards the coupling of one valve member to the release bearing 32 in the embodiment of Figure 1.

The control valve arrangement 42 (or 42a or 42b) switches over between three control states depending on the command signal supplied by the command signal transmitter unit 60, which specifies a reference axial position of the release bearing 32 and on the actual value signal indicating the axial position of the release bearing 32. In a first control state, by way of the control valve arrangement 42, a pneumatic connection is produced between the pneumatic ring cylinder 16 and the pneumatic source 51, so that pneumatic medium, in this case compressed air, is supplied to the chamber 18 of the pneumatic ring cylinder from the pneumatic source 51 and the pneumatic ring piston member 22 is displaced in a corresponding manner in the direction of the clutch. In a second control state of the control valve arrangement 42, a pneumatic relief connection is established between the pneumatic ring cylinder 16 and the pressure- compensating opening 70, so that the pneumatic ring piston member 22 is displaced in the chamber 18 due to the compressive force of the clutch main spring, for example of a diaphragm spring or the like, in which case the compressed air located in the ring cylinder chamber 18 of the pneumatic ring cylinder 16 flows out of the pre s sure- compens at ing opening 70. In a third control state, the ring cylinder chamber of the pneumatic ring cylinder 16 is closed essentially in a pneumatic-tight manner, so that the pneumatic ring piston member 22 retains its momentary axial position.

27 The control valve arrangement 42 and its valve members, forms with the pneumatic power cylinder arrangement 14, the coupling member 72 representing a transmitter member for the actual value signal and the coupling member 74, a mechanical positionregulating arrangement, which due to corresponding switchingover between the three control states, sets the axial position of the release bearing 32 at the reference position indicated by the command signal from the command signal transmitter unit 60.

For this purpose, the momentary position of the release bearing 32 as the actual value is represented by the position of the second valve member and the reference position of the release bearing 32 as the command value is represented by the position of the first valve member. Associated with the actual value and the command value is a differential value, which is represented by the position of the f irst and of the second valve member relative to each other and assumes the value zero, when the actual axial position of the release bearing 32 corresponds to the reference position.

Two further embodiments of an actuating device 10 in accordance with the invention or of individual components thereof will be described hereafter. When describing the respective embodiment, the same reference numerals will be used as in the embodiment or embodiments described previously, for components having the same action or similar components. In this case, solely the differences with respect to the embodiments already described will be discussed and moreover reference will be made expressly to the preceding description of the other embodiment(s). To distinguish between the embodiments, the reference numerals of the two embodiments described hereafter will be characterised by a for the embodiment of Figures 2 to 4 and b for the embodiment of Figures 5 to 9.

28 Figure 2 shows an actuating cylinder component 14a of an actuating device 10, which likewise comprises a pneumatic ring cylinder 16a with a pneumatic ring piston member 22a. The cylinder chamber of the pneumatic ring cylinder 16a is sealed by at least one sealing ring 27a acting between the pneumatic ring piston member 22a and the body part 20a of the actuating cylinder component 14a. A control valve component 40a is releasably flange-mounted on the actuating cylinder component 14a. The control valve component 40a comprises a control valve arrangement 42a with a valve housing 90a, in which, as in the embodiment of Figure 1, three valve members, namely a first valve member 92a, a second valve member 94a and a third or auxiliary valve member 96a are mounted to slide along a valve axis B parallel to the clutch axis A in a ring-shaped recess 98a of the valve housing 90a. The control valve arrangement 42a also comprises a pneumatic connection 48a, to which the pneumatic source 51a is connected by way of the pneumatic line 50a. Furthermore, the control valve arrangement 42a also comprises a hydraulic connection 54a, to which the clutch pedal arrangement 60a is connected by way of the hydraulic line 56a.

The hydraulic connection 54a comprises a bore 100a, which in the region of a base 102a defining the ring-shaped recess 98a on the side remote from the clutch, opens into the ring-shaped recess 98a. The pneumatic connection 48a comprises a bore 104a, which in the end region of the ringshaped recess 98a adjacent the clutch opens into this recess 98a.

The ring-shaped recess 98a, which radially outwards and radially inwards is defined by ring-shaped cylindrical walls of the valve housing 90a extending coaxially at a radial distance apart, extends around a tube member 106a integral with the valve housing 90a, coaxial with respect to the valve axis B and extending from the base 102a in the direction of the clutch.

29 The tube member 106a does not extend as far in the direction of the clutch as the remaining valve housing 90a, so that adjoining a strictly ring-shaped cylindrical recess section of the ring shaped recess 98a, which is thus defined radially inwards and radially outwards, in the direction of the clutch is a cylindrical recess section defined radially outwards but not radially inwards, which for the sake of simplicity is perceived as part of the recess 98a.

Extending through the tube member 106a is an axial bore 108a, which is open in the direction of the clutch and communicates with the ring-shaped recess 98a. Adjoining the bore 108a is a bore 110a in the base 102a and adjoining the latter is a bore 112a in the actuating cylinder component 14a, which opens into 15 the interior of the cylinder of the pneumatic ring cylinder 16a of the actuating cylinder component 14a. A pneumatic connection between the ring-shaped recess 98a and the cylinder chamber of the pneumatic ring cylinder 16a can be produced by way of the said bores.

The strictly ring-shaped cylindrical section of the ring-shaped recess 98a and the first valve member 92a form a hydraulic slave cylinder; for this purpose, an end section of the first valve member 92a remote from the clutch is constructed as a ring shaped cylindrical hydraulic piston section 114a. The hydraulic piston section 114a is guided to slide in a sealing manner by way of two sealing rings 116a and 118a in the ring-shaped cylindrical section of the ring-shaped recess 98a.

Upon actuation of the clutch pedal arrangement 60a causes, on account of the hydraulic medium, in particular hydraulic oil, flowing into the cylinder chamber of the hydraulic slave cylinder and acting on the hydraulic piston section 140a, the first valve member 92a to be displaced, starting from the axial position corresponding to Figure 3a, in the direction of the clutch, in which case the axial position of the first valve member 92a, which is then preset, indicates the reference position of the release bearing 32, not shown in Figures 2 to 4, 5 and thus the command value.

The first valve member 92a comprises a tube section 120a adjoining the hydraulic piston section 114a in the direction Of the clutch, which tube section 120a surrounds the tube member 106a radially on the outside and is guided in a sealing manner on the tube 106a by means of a sealing ring 122a in an annular groove of the tube member 106a close to its end adjacent the clutch. In the position of the first valve member 92a furthest from the clutch and shown in Figure 3a where the hydraulic piston section 114a strikes against the recess base 102a or is directly adjacent to the latter, the tube section 120a projects slightly beyond the tube member 106a in the direction of the clutch. The tube section 120a then ends in an end section 124a extending in the radial direction and covering the interior of the tube section 120a and thus the tube member 106a in the axial direction. This end section 124a will be referred to hereafter as a closure section 124a, on account of its function which is still to be described in detail. Provided in the part of the tube section 120a projecting beyond the tube member 106a in the position of Figure 3a are four bores 126a extending in the radial direction, which establish a connection between the inside of the tube section 120a and the region of the ringshaped recess 98a radially outside the tube section 120a and thus a connection between the cylinder chamber of the pneumatic ring cylinder 16a and the said ring-shaped recess section radially outside the tube section 120a (in this view, the second valve member 94a and the auxiliary valve member 96a are not yet taken into consideration).

31 The second valve member 64a likewise constructed to be ringshaped surrounds the tube section 120a of the ring-shaped first valve member 92a radially on the outside. A ring-shaped end section 128a, remote from the clutch, serves as an abutment section, against which the first valvemember 92a may strike with the side of the hydraulic piston section 114a adjacent the clutch, as a result of a clutch pedal actuation (see Figures 4a and b), due to which a limitation of the axial displacement range of the first valve member 92a in the direction of the clutch, which is variable with the axial position of the second valve member 94a, is achieved. In a ring-shaped recess, the end section 128a supports a sealing ring 130a, by which the end section 128a is guided to slide in a sealing pneumatic-tight manner against the radially outer ring- shaped wall of the ring- shaped recess 98a. Provided between the end section 128a of the second valve member 94a and the hydraulic piston section 114a of the first valve member is a helical compression spring 132a extending around the tube section 120a of the first valve member 92a, which in the position of the valve members corresponding to Figure 3a, in which the end section 128a and the hydraulic piston section 114a do not abut against each other, and all the more in the case of an abutment of the hydraulic piston section 114a against the end section 128a, is subject to a compressive load. The compression spring 132a is thus effective in increasing the axial distance between the hydraulic piston 114a and the end section 128a with respect to the distance of Figure 3a and more than ever with respect to the distance of Figures 3b and Figures 4a and b.

Adjoining the end section 128a of the second valve member 94a, in the direction towards the clutch, is a ringshaped or tubeshaped section 134a of the second valve member 94a, which on account of its function to be described clearly hereafter, of contributing to the guidance of compressed air within the 32 control valve, is referred to hereafter as the guide section 134a. In the position of the second valve member 94a corresponding to Figure 3a, in which it adopts its position furthest from the clutch, and thus has penetrated the ringshaped recess 28a to the maximum extent, the guide section 134a projects slightly from the ring-shaped recess 28a by way of the valve housing 90a in the direction of the clutch.

A ring-shaped recess for a sealing ring 136a is provided in the 10 ringshaped wall of the valve housing 90a defining the ring- shaped recess 98a radially towards the outside. The ring-shaped recess and thus the sealing ring 136a are offset inthe direction of the clutch with respect to the bore 104a, which serves for the supply of pneumatic medium. The sealing ring 136a is active in guiding the guide section 134a in a pneumatic tight manner in the ring-shaped recess 98a. Since a certain, not insignificant radial clearance exists between the radially outer periphery of the guide section 134a and the ring-shaped wall of the valve housing 90a defining the ring-shaped recess 98a radially towards the outside, an annular space 140a is formed between the radially outer radial peripheral surface of the section 134a and the ring-shaped wall of the valve housing 90a. This space 140a is defined axially in the direction towards the clutch by the sealing ring 136a (cf Figure 3b) and axially in the direction towards the recess base 102a by the sealing ring 130a (cf Figure 3b). The bore 104a opens into this annular space 140a which is variable in its axial extent on account of the displaceability of the second valve member 94a.

Provided in the guide section 134a of the second valve member, in the transition region to the end section 128a, but still on the clutch side of the sealing ring 130a, are several throughbores 138a opening into the aforementioned annular space 140a. The bores 138a establish a connection between the annular space 33 140a and the region of the ring-shaped recess 28a radially inside the guide section 134a and axially on the clutch side of the end section 128a. Figures 3 and 4 show two such throughbores 138a. Provided that one does not take into consideration 5 the auxiliary valve member 96a, by way of these through-bores 138a a connection exists between the pneumatic source 51a and the cylinder chamber of the pneumatic ring cylinder 16a, namely by way of the pneumatic line 50a, the pneumatic connection 48a, the bore 104a, the annular space 140a formed within the ring- shaped recess 98a between the second valve member 94a and the valve housing 90a, the through-bores 138a, the bores 126a in the tube section 120a of the first valve member, the bore 108a in the tube member 106a, the bore 110a in the base 102a of the valve housing 90a as well as the bore 112a in the actuating cylinder component 14a. Since the ring-shaped recess 98a is open in the direction of the clutch, in so far that the auxiliary valve member 36a were not present, then at the same time a connection would exist continuously between the cylinder chamber of the pneumatic ring cylinder 16a and the atmosphere and accordingly also between the pneumatic source 51a and the atmosphere, so that compressed air would flow out constantly.

The auxiliary valve member 96a to be described in detail hereafter prevents such an undesirable pneumatic connection between the pneumatic source 51a and the atmosphere and in conjunction with the first valve member 92a and the second valve member 94a, it brings about switchingover between the three control states of the control valve already mentioned in connection with the embodiment of Figure 1, so that the cylinder chamber of the pneumatic ring cylinder 16a is connected either to the pneumatic source 51a (first control state) or is connected to the atmosphere (second control state) or is closed off in a pneumatic-tight manner (third control state).

34 The auxiliary valve member 96a likewise constructed as a ring member is located radially between the guide section 134a of the second valve member 94a and the tube section 120a of the first valve member 92a. The auxiliary valve member 96a extends in the axial direction beyond the closure section 124a of the first valve member 92a in the direction of the clutch and at this end adjacent the clutch comprises an annular section 142a projecting radially inwards, which is associated with the first valve member 92a and on which the first valve member 92a acts with its closure section 124a in the case of a clutch actuation as a result of an axial displacement of the first valve member in the direction of the clutch and due to this entrains the auxiliary valve member 96a. The regions of the closure section 124a bearing against each other in this case and of the action section 142a are in this case in pneumatic-tight sealed engagement.

At its end opposite the section 142a associated with the first valve member 92a, thus remote from the clutch, the auxiliary valve member 96a comprises a further section 144a, associated with the second valve member 94a, which is likewise constructed in the shape of a ring. Clamped between a collar of the auxiliary valve member 96a adjacent to the section 144a and a ring-shaped part 146a fixed (for example screwed or clamped) to the second valve member 94a at its end adjacent the clutch is a compression coil spring 148a surrounding the auxiliary valve member 96a. The spring 148a ensures the auxiliary valve member 96a is pre-tensioned in the direction for abutment and engagement between the section 144a of the auxiliary valve member 96a associated with the second valve member 94a and the side adjacent the clutch of the end section 128a of the second valve member 94a. Unless the closure section 124a of the first valve member 92a abuts against the action section 142a of the auxiliary valve member 96a associated with the first valve member 92a and pushes the latter against the force of the compression spring 148a with respect to the second valve member 94a in the direction of the clutch, on account of the action of the compression spring 148a, engagement between the section 144a of the auxiliary valve member 96a and the end section 128 of the second valve member is produced. The regions of the section 144a and of the end section 128a bearing against each other are thus in pneumatic-tight sealing engagement.

The ring-shaped part 146a of the second valve member 94a supports in a ring-shaped groove a sealing ring 150a, by means of which the auxiliary valve member 96a is guided to slide in a pneumatic-tight manner in the second valve member 94a. Also, the engagement between the ring-shaped part 146a and the second valve member 94a is pneumatic-tight, so that in the case that the closure section 124a of the first valve member 92a does not act on the section 142a of the auxiliary valve member 96a associated therewith, an annular space 152a defined by the tube section 120a of the first valve member 92a and by the auxiliary valve member 96a is closed in a pneumatic-tight manner with respect to the atmosphere. If the section 142a associated with the first valve member 92a, the auxiliary valve member 96a and the closure section 124a of the first valve member 92a are not in engagement with each other, then by way of a ring-shaped opening 154a defined by the section 142a, a connection is produced between the annular space 152a and the atmosphere. This ring-shaped opening 154a thus forms the pressurecompensating opening 70a of the control valve arrangement 42a.

The annular space 152a between the auxiliary valve member 96a and the tube section 120a of the first valve member 92a is constantly connected by way of the bores 126a and the bores 108a, 110a and 112a to the cylinder chamber of the pneumatic ring cylinder 16a. Whether this annular space 152a is also 36 connected by way of the bores 138a, the annular space 140a between the second valve member 94a and the valve housing 90a and the pneumatic connection 104a, 48a, 50a to the pneumatic source 51a, depends on the position of the auxiliary valve member 96a relative to the second valve member 94a. I f the section 144a of the auxiliary valve member 96a, associated with the second valve member 94a, is not in engagement with the end section 128a of the second valve member 94a (this is solely the case when the closure section 124a of the first valve member 92a acts on the section 142a associated with the auxiliary valve member 96a and entrains the auxiliary valve member 96a in the direction of the clutch against the force of the compression spring 148a), the annular space 152a and thus the cylinder chamber of the pneumatic ring cylinder 16a are in pneumatic connection with the pneumatic source 51a (Figures 4a and 4b).

If, on the other hand, the section 144a and the end section 128a of the second valve member 94a are in engagement, then the pneumatic connection between the pneumatic source 51a, and the cylinder chamber of the pneumatic ring cylinder 16a is interrupted. The cylinder chamber of the pneumatic ring cylinder 16a is then either closed in a pneumatictight manner (this is the case when simultaneously the closure section 124a of the first valve member 92a acts on the associated section 142a of the auxiliary valve member 96a; Figure 3b), or the annular space 152a and thus the cylinder chamber of the pneumatic ring cylinder 16a are connected by way of the pres sure- compensating opening 70a to the atmosphere. This is the case when the closure section 124a of the first valve member 92a does not act on the associated action section 142a of the auxiliary valve member 96a; of Figure 3a.

The method of operation of the control valve arrangement 42a depends on the fact that the second valve member 94a with its axial position represents the actual position of the release 37 bearing 32 (not shown). For this purpose, the second valve member 94a is connected by way of a fork-shaped coupling section 160a, integral with the second valve member 94a, and without clearance, to a flange-like end section 162a of the pneumatic ring piston member 22a, adjacent to the clutch. The second valve member 94a and the pneumatic ring piston member 22a are thus axially rigidly kinematically coupled. On the other hand, the axial position of the first valve member 92a represents the axial reference position of the release bearing 32. Associated with the actual position of the release bearing 32 and the reference position of the release bearing is a differential value, which is represented by the relative position of the first valve member 92a and of the second valve member 94a with respect to each other. If, at the time of release of the clutch, the actual position of the release bearing corresponds to the reference position, then the first valve member 92a and the second valve member 94a adopt a certain relative position with respect to each other, namely that relative position, in which simultaneously an engagement between the section 142a of the auxiliary valve member 96a and the closure section 124a of the first valve member 92a and the section 144a of the auxiliary valve member 96a and the end section 128a of the second valve member 94a is produced, so that the cylinder chamber of the pneumatic ring cylinder 16a is closed in a pneumatic-tight manner (cf Figure 3b).

The method of operation of the control valve arrangement 42a will be clearest if one considers a series of control conditions during an actuation of the clutch. In the basic state, when the clutch pedal arrangement 60 is not actuated, the control valve arrangement 42a adopts the state illustrated in Figure 3a. In this basic state, the cylinder chamber of the pneumatic ring cylinder 16a is connected by way of the pre s sure- compensating opening 70a to the atmosphere, so that atmospheric pressure 38 prevails in the cylinder chamber. Extraneous influences (for example temperature), which otherwise could lead to an undesirable pressure change in the cylinder chamber, thus play no part. Since the section 144a of the auxiliary valve member 96a (also referred to as the sealing piston) is in engagement with the end section 128a of the second valve member 94a (also referred to as the release displacement unit), the compressed air of the pneumatic source 51a is held back.

If the pedal 62a is actuated by the driver, then the first valve member 92a (also referred to as the pedal displacement unit) is moved in the direction of the clutch (towards the left in the drawings). Initially because engagement between the section 142a of the auxiliary valve member 96a and the closure section 124a of the first valve member 92a is established, the venting of the cylinder chamber of the pneumatic ring cylinder 16a by way of the pres sure- compensating opening 70a is closed (Figure 3b). Then, the pneumatic connection between the pneumatic source 91a and the cylinder chamber of the pneumatic ring cylinder 16 is produced due to the fact that the first valve member 92a entrains the auxiliary valve member 96a with respect to the second valve member 94a, thus against the force of the compression spring 148a and displaces the section 144a of the auxiliary valve member 96a, lifting it from the end section 128a of the second valve member 94a in the direction of the clutch (Figure 4a). Now, compressed air may flow from the pneumatic source 51a into the cylinder chamber of the pneumatic ring cylinder 16a, so that the pneumatic ring piston member 22a moves against the force of the diaphragm spring in the direction of the clutch. The pneumatic ring piston member 22a in this case entrains the second valve member 94a by way of the coupling section 160a in the direction of the clutch, so that also the second valve member 94a follows the displacement predetermined by the first valve member 92a (Figure 4b). If the pedal 62a is 39 then not actuated further, the second valve member 94a f inally reaches an axial position, in which both the closure section 124a of section 128a of section cylinder the first valve member 92a acts on the associated 142a of the auxiliary valve member 96a the end section the second valve member 94a acts on the associated 144a of the auxiliary valve member 96a, so that the chamber of the pneumatic ring cylinder 16a is closed in a pneumatic-tight manner. An equilibrium of forces then prevails between the diaphragm spring force on the pneumatic ring piston member and the force exerted by the compressed air in the cylinder chamber of the pneumatic ring cylinder 16a on the pneumatic ring piston member, so that the pneumatic ring piston member 22a and thus the release bearing is retained in the axial position that is reached (cf Figure 3b).

If the clutch pedal 62a is released partially or completely, then the compression spring 132a acting between the first valve member 92a and the second valve member 94a is able to displace the first valve member 92a with respect to the second valve member 94a in the direction of the recess base 102a, so that the engagement between the closure section 124a of the first valve member 92a and the associated section 142a of the auxiliary valve member 96a is discontinued and the cylinder chamber of the pneumatic ring cylinder 16a is vented by way of the pressure- compensating opening 70a, until either (in the case of a clutch pedal 62a released only partly) this engagement is reestablished or (in the case of a complete release of the clutch pedal 62a) the basic state of Figure 3a is once again reached. The diaphragm spring of the clutch, on account of the venting of the cylinder chamber, is able to displace the pneumatic ring piston member 22a and thus the second valve member 94a away from the clutch in the direction of the gearbox.

In contrast to the embodiments of Figures 1 to 4, in which the valve members of the control valve arrangement for the representation of the axial actual position of the release bearing or of the pneumatic ring piston member by the axial displacement position of the second valve member and for the representation of the axial reference position of the release bearing 32 or of the pneumatic ring piston member by the axial displacement position of the first valve member, are displaceable along the valve axis, in the embodiment of Figures 5 to 9, the f irst valve member 92b and 94b is able to rotate about a valve axis B' for the representation of the axial actual position of the release bearing 32 or of the pneumatic ring piston member 22b by the rotary position of the second valve member 94b and for the representation of the reference position of the release bearing 32 or of the pneumatic ring piston member 22b by the rotary position of the first valve member 92b.

The valve housing 90b comprises a circular cylindrical throughbore 180b, which extends coaxially with respect to the valve axis B' at right angles through the valve housing 90b, is open towards both sides and receives two valve members, i.e. the first valve member 22b and the second valve member 94b. A third or auxiliary valve member is not provided in this embodiment, so that the control states of the control valve are realised solely by the first valve member 92b and the second valve member 94b.

Three radial bores 182b, 184b and 186b located in a common plane at right angles to the valve axis B', open into the through-bore 180b, whereby in each case with respect to the valve axis B', the same peripheral angular spacing lies between the radial bore 182b and the radial bore 184b, between the radial bore 184b and the radial bore 186b and between the radial bore 186b and the radial bore 182b and the three bores respectively cover a peripheral angular region of the same extent. In the view 41 according to Figure 8, the three radial bores follow each other along the periphery of the through-bore 180b in clockwise direction in the sequence 182b, 184b and 186b.

The radial bore 182b produces a connection between the interior of the through-bore 180b and the atmosphere and serves as the pre s sure- compens at ing opening 70b of the control valve. The radial bore 184b is part of the pneumatic connection 48b and thus by way of the pneumatic line 50b produces a pneumatic connection between the interior of the through-bore 180b and the pneumatic source 51b. Adjoining the radial bore 186b are bores 188b in the body part 20b of the actuating cylinder component 14b, by which a connection is produced between the interior of the through-bore 180b and the cylinder chamber of the pneumatic ring cylinder 60b (cf Fig. 8). It is to be noted that in this description, the first valve member 92b is still not taken into consideration. The intersecting bores 190b and 192b are closed with respect to the outside of the body part 20b by closure balls 194b which are pressed-in.

The first valve member 92b comprises a circular cylindrical main section 198b received in the through-bore 180b and coaxial with the valve axis B', adjoining which is a circular cylindrical journal section 200b of the first valve member 92a, which section is likewise coaxial with the valve axis B' and projects from the through-bore 180b on one side (the left-hand of Figure 7). The main section 198b comprises a through-bore 202b directed radially with respect to the valve axis B', which bore lies in the same plane, at right angles to the valve axis B', as the radial bore 182b, 184b and 186b.

The main section 198b of the first valve member 92b in the through-bore 180b is surrounded by a circular cylindrical ring section 204b of the second valve member 94b, which fills the 42 remaining annular space between the main section 198b and the inner peripheral surface of the through-bore 180b and is coaxial with the valve axis B'. Adjoining the ring section 204b in the direction of the end of the through-bore 180b opposite the journal section 200b is a circular wall section of the second valve member 94b, still located in the through-bore 180b and corresponding substantially in radius to the latter, adjoining which once again is a circular cylindrical journal section 208b, projecting from the throughbore 180b and coaxial with the valve axis B'. The journal section 200b of the first valve member thus projects on one side of the through-bore 180b and the journal section 208b of the second valve member thus projects on the other side of the through-bore 180b.

The ring-shaped section 204b of the second valve member comprises three slot-like through- recesses 210b, 212b and 214b, referred to as slots or openings, which extend in the peripheral direction respectively relative to the valve axis B', and lie in the same plane at right angles to the valve axis B' as the radial bores 182b, 184b and 186b and the through-bore 202b. The openings 210b, 212b and 214b in each case cover a peripheral angle of the same size. The radial bores 182b, 184b, 186b, the through-bore 202b and the openings 210b, 212b and 214b extend in the axial direction in each case over the same axial region of the control valve arrangement, as can be seen clearly in Figure Provided in the outer peripheral surface of the ring-shaped section 204b of the second valve member 94b, on both sides of the openings 210b, 212b, 214b are sealing rings 216b and in the main section 198b of the first valve member 92b is a sealing ring 218b offset with respect to the through-bore 202b in the direction of the journal section 200b. These sealing rings 216b and 218b serve to seal the axial region of the through-hole 280b 43 comprising the radial bores 182b, 184b and 186b, the throughbore 202b and the openings 210b, 212b and 214b, between the sealing rings 216b at the two open ends of the through-bore 180b, in a pneumatic-tight manner. Furthermore, spring rings which can be seen in Figure 7 but are not designated by a reference numeral, are provided, which secure the second valve member 94b in the through-bore 180b and the first valve member 92b with its main section 198b inside the ring-shaped section 104b of the second valve member 94b.

The two valve members 92b and 94b are able to rotate with respect to each other solely in a restricted manner, since two pins 220b, offset radially with respect to the valve axis B', are provided on the axial end face of the main section 198b of the first valve member 92b, opposite the journal section 200b, which pins engage in a respective recess 222b in the wall section 206b of the second valve member 94b, which recess extends along a circular arc (see Figures 7 and 9). On account of the dimensions of the recesses 222b, relative rotatability of the two valve members over an angular region amounting to approximately 75" to 800 is facilitated.

The two valve members 92b and 94b are constructed with the openings 210b, 212b and 214b, with the through-bore 202b, the pins 220b and the recesses 222b in succession so that the through-bore 202b is connected in any possible relative rotary position of the two valve members, on its one side to the opening 214b and on its other side either to the opening 210b, or to the opening 212b or is closed by a section 224b forming a closure and control section, between the two openings 210b and 212b, in a pneumatic-tight manner. The opening 210b is in this case constantly connected to the pre s sure- compens at ing opening 70b, the opening 212b is thus constantly connected by way of the bore 184b to the pressure medium source 51b and the opening 214b 44 is thus constantly connected by way of the bore 186b to the cylinder chamber of the pneumatic ring cylinder 16b.

The second valve member 94b is kinematically coupled to the pneumatic ring piston member 22b so that exactly one rotary position of the second valve member 94b is associated with each axial position (relative to the clutch axis) of the pneumatic ring piston member 22b and thus of the release bearing 32. For this purpose, non-rotatably located on the journal section 208b of the second valve member 94b is a bracket 226b, which is pre tensioned by a helical spring surrounding the journal section 208b, acting on the bracket 226b and on the valve housing 90b (cf Figures 5 and 7), against the flange-like end section 162b of the pneumatic ring piston member 22b. The bracket 226b thus acts on the side of the end section 162b remote from the clutch.

Non-rotatably located on the journal section 208b is a lever 230b, which with a piston rod 232b of a cylinder-piston arrangement 234b forms a twin-member toggle lever. The cylinder-piston arrangement 234b is a hydraulic slave cylinder, which is connected by way of the connection 94b and the hydraulic line 56b to the clutch pedal arrangement 60b. A piston 236b on the piston rod 232b is pre-tensioned by a helical compression spring 238b in the direction of reducing the cylinder chamber of the hydraulic slave cylinder 234b.

The hydraulic slave cylinder 234b is constructed as a component with the valve housing 90b.

The toggle lever arrangement comprising the lever 230b and the piston rod 232 serves for converting a sliding movement of the piston 236b into a rotary movement of the first valve member 92b. Exactly one rotary position of the first valve member 92b is associated with each sliding position of the piston 236b.

In a basic position of the control valve arrangement, in which the clutch pedal 92b of the clutch pedal arrangement 60b is not depressed and the pneumatic ring piston member 22b is not released, and thus adopts its axial position furthest from the clutch, the aperture of the through-bore 200b, opposite the opening 214b, in the main section 198b of the first valve member 92b, is approximately opposite the pre s sure- compens at ing opening 70b and the closure and control section 224b is offset somewhat with respect to the pre s sure- compensating opening 70b, relating to Figure 8 in clockwise direction, in the direction of the bore 184b. The other aperture of the through-bore 202b lies opposite the opening 214b thus is not closed by the section 240b of the ring section 204b of the second valve member 94b, separating the opening 214b from the opening 212b. Thus, in the basic state described, there is a continuous venting connection between the cylinder chamber of the pneumatic ring cylinder 16b and the pre s sure- compensating opening 70b, namely by way of the bores 192b, 190b, 186b, the opening 214b, the through-bore 202b and the opening 210b. The compressed air of the pneumatic source 91b is in this case retained by the closure and control section 225b and the section 240b of the ring section 204b of the second valve member 94b.

Now if the clutch pedal 62b is actuated by the driver, then the firstvalve member 92b (also referred to as the pedal displacement unit) with the aperture of the through-bore 202b, hitherto lying approximately opposite the venting opening 70b, is rotated in the direction of the bore 184b forming the compressed air inlet opening. In this case, by travelling over the closure and control section 224b, forming a control edge, between the opening 210b and the opening 212b, first of all the venting is closed, in that the closure and control section 224b closes the through-bore 202b, then the connection between the 46 cylinder chamber of the pneumatic ring cylinder 16b and the pneumatic source 51b is produced, namely by way of the bore 184b, the opening 112b, the throughbore 202b, and the bores 186b, 188b, 190b and 192b. Now if compressed air flows into the cylinder chamber, the pneumatic ring piston member 22b moves against the force of the diaphragm spring in the direction of the clutch. In this case, the second valve member (referred to as the release displacement unit) follows the rotary angle predetermined by the first valve member. During the supply of compressed air to the cylinder chamber of the pneumatic ring cylinder 16b, a flowing-out of the compressed air supplied from the pressure-compensating opening 70b is prevented by the closure and control section 224b and a section of the ring section 204b of the second valve member 94b separating the opening 214b from the opening 210b.

If the clutch pedal is kept in the actuating position reached, on reaching the rotary angle predetermined by the first valve member, the closure and control section 224b once again closes the through-bore 202b in the main section 198b of the first valve member 92b so that the supply of compressed air is interrupted, but also no venting connection is produced between the cylinder chamber of the pneumatic ring cylinder 16b and the pres sure- compensating opening 70b. An equilibrium of forces then prevails between the force exerted by the diaphragm spring on the pneumatic ring piston member 22b and the force exerted by the compressed air in the cylinder chamber of the pneumatic ring cylinder 16b on the pneumatic ring piston member 22b.

If the clutch pedal 62b is released again, then the first valve member 92b is rotated in the opposite direction on account of the spring force exerted by the spring 238b on the piston 236b, so that now once again the venting connection between the pressure-compensating opening 70b and the cylinder chamber of 47 the pneumatic ring cylinder 16b is established and the pneumatic ring piston member 22b is pushed by the force of the diaphragm spring away from the clutch in the direction of the gearbox with corresponding rotation of the second valve member 94b.

As the preceding comments made clear, in the embodiments described previously with reference to Figures 5 to 9, the reference position of the pneumatic ring piston member 22b and thus of the release bearing and the momentary actual position of the pneumatic ring piston member 22b and thus of the release bearing are represented by rotary positions of the first valve member 92b or of the second valve member 94br With its rotary position, the first valve member thus represents a command value and with its rotary position the second valve member thus represents an actual value, on the basis of which the control valve switches over between the control states indicated generally in relation to Figure 1. In this case a differential value may be associated with the command value and the actual value, which differential value is represented by the relative rotary position of the two valve members with respect to each other.

It should be noted as important that even with a valve member jointly rotatable and representing by rotary positions the command value, the actual value and the differential value, one could work with a rotatable auxiliary valve member, which cooperates with the first and the second valve member, in order to achieve the control states by closing or opening pressure medium connections within the control valve. Conversely, also in a control valve, with axially displaceable valve members for representation of the command value, the actual value and the differential value, it is possible to work solely with two valve members, thus to dispense with an additional auxiliary valve member able to slide along the valve axis, in that one of the 48 two valve members is constructed with a control edge, which switches over between two alternative pressure medium connections or closes a pressure medium path common to the two pressure medium connections.

The transferability of the operating principles from a control valve with valve members arranged to rotate and representing the said values by rotary positions, to a control valve with valve members arranged to slide and representing the said values by sliding positions (and vice versa) will be made particularly clear if one compares the embodiment of Figures 5 to 9 with the embodiment of Figures 10 and 11 to be described hereafter. In the embodiment of Figures 10 and 11, the same reference numerals as in the embodiment of Figures 5 to 9 are largely used, in which case for the purpose of distinguishing between them the reference numerals for the embodiment of Figures 10 and 11 are characterised by the letter "c". As regards the embodiment of Figures 10 and 11, reference will be made expressly to the preceding description of the embodiment of Figures 5 to 9 and only the differences between the two embodiments will be described.

In the same way as the control valve arrangement 42b, the control valve arrangement 42c comprises two valve members located in a valve housing 90c, namely a first valve member 92c and a second valve member 94c. In contrast to the embodiment of Figures 5 to 9, these valve members are able to slide along a valve axis W' and represent the command value, the actual value and the differential value by sliding or axial positions. In this respect reference can be made to the embodiment of Figures 2 to 4.

A great similarity between the control valve arrangement of Figures 5 to 9 and the control valve arrangement of Figures 10 49 and 11 results from the fact that the control valve arrangement of Figures 10 and 11 with respect to its construction in the axial direction corresponds essentially by a certain extent to a "development" of the control valve arrangement of Figures 5 to 9 with respect to its construction in the peripheral or rotational direction. Thus, a corresponding rotary position of the valve members 92b and 94b can be associated with each axial position of the valve members 92c and 94c.

The valve body 90c comprises a circular cylindrical recess 180c coaxial with the valve axis B'',' in which the second valve member 94c is received to slide along the valve axis B''. The second valve member 94c comprises a circular cylindrical recess 300c, likewise coaxial with the valve axis B'', in which the first valve member 92c is arranged to slide with a control section 302c along the valve axis B''. The first valve member 92c comprises a section 200c projecting from the valve housing 90c and receiving the command value and the second valve member 94c, comprises a section 208c projecting on the opposite side from the valve housing 90c and receiving the actual value.

The valve housing 90c comprises three bores 182c, 186c and 184c offset with respect to each other in the axial direction (valve axis B''), which follow each other in this sequence in the direction from the section 200c to the section 208c. The axial distance between the bores 182c and 186c is equal to the axial distance between the bores 186c and 184c. The bores are directed radially with respect to the valve axis B' ' and open out in the recess 180c of the valve housing 90c. The bores 182c, 184c, 186c are also offset with respect to each other in the peripheral direction; however this is not important for the operation of the control valve and serves solely for the control valve to have a short overall construction in the axial direction.

The second valve member 94c comprises three openings 210c, 214c and 212c offset with respect to each other in the axial direction (valve axis B''), in which case the openings follow each other in the said sequence in the direction from the section 200c to the section 208c. Each of the said openings is formed by an elongated recess, extending in the axial direction, and a bore lying radially further inwards and provided in the axial centre of the recess, so that a connection between the outside of the second valve member 94c and the recess 300c provided therein can be produced by the elongated recess and the bore. In each axial position of the second valve member 94c, the opening 210c is open to the bore 182c, the opening 214c is open to the bore 186c and the opening 212c is open to the bore 184c, since the respective elongated recess of the relevant opening covers the respective bore in the valve housing radially on the inside. Without taking the first valve member 92c into consideration, a connection thus always exists between the bores 182c, 186c and 184c and the recess 300c inside the second valve member 94c and thus a connection exists between the bores.

The control section 302c of the first valve member 92c now serves to open and close the connections between the bores 182c, 186c and 184c depending on the axial relative positions of the two valve members. For this purpose, the control section 302c comprises two closure sections 306c and 308c respectively forming a control edge, which, provided that they cover the radially inner bore of the respective opening 210c or 212c, close the latter with respect to the recess 300c in the second valve member 94c.

Between the two closure sections 306c and 308c, the control section 302c of the first valve member 92c comprises a ringshaped recess, which is open radially towards the outside and 51 forms an annular channel 202c. The annular channel 202c is open in any axial relative position of the two valve members with respect to each other at least to the opening 214c and thus to the bore 186c leading to the pressure medium power cylinder 5 arrangement.

Depending on the axial relative position of the two valve members to each other, the annular channel 202c is open either solely to the opening 214c and thus to the bore 186c or either additionally also to the opening 212c and thus to the bore 184c leading to the pressure medium supply or to the opening 210c and thus to the bore 182c, which serves as the pressurecompensating opening 70c.

In the basic position of the control valve arrangement shown in Figure lla, in which the clutch is not disengaged, a venting connection exists between the bore 186c and the bore 182c by way of the annular channel 202c. If the first valve member 94c is moved towards the left according to the illustration in Figure 11, corresponding to a command value increasing as a result of a clutch pedal actuation for example, then first of all the radially inner bore of the opening 210c is closed by the closure section 306c, before the closure section 308c, which in the basic position has closed the radially inner bore of the opening 212c, has thus moved so far past this radially inner bore until a pressure medium connection is produced between the bores 186C and 184c in the control valve housing 90c by way of the openings 212c, 214c and the annular channel 202c and pressure medium is supplied to the power cylinder arrangement. Figure llb shows the control valve arrangement in a state of maximum clutch actuation, in which such a pressure medium connection is established between the bores 184c and 186c.

52 In the case of a non-maximum clutch actuation, when the actual value is equal to the command value, the two valve members adopt such an axial relative position with respect to each other that the closure section 306c closes the radially inner bore of the opening 210c and the closure section 208c closes the radially inner bore of the opening 212c, so that no pressure medium connection between the pressure medium power cylinder arrangement on the one hand and neither the pressurecompensating opening 70c nor the bore 184c leading to the pressure medium supply, on the other hand, exists.

Apart from the bores and openings in the valve housing 90c and in the second valve member 94c, the valve housing and the two valve members 92c and 94c are constructed to be essentially rotationally symmetrical with respect to the valve axis B' 1.

Above all, rotary position-fixing means (not shown in the drawings) are provided, which interrupt the rotational symmetry and preclude a relative rotation between the second valve member 94c and the valve housing 90c, so that guaranteed that the opening 210c is open to opening 214c is open to the bore 186c and it is constantly the bore 182c, the the opening 21c is open to the bore 184c. The bores 182c, 186c and 184c and correspondingly also the openings 210c, 214c and 212c are, as already mentioned, in addition to their mutual stagger in the axial direction also staggered with respect to each other in the peripheral direction (with respect to the valve axis B''), in order to keep the control valve short in the axial direction.

Basically one could spread apart the bores 182c to 186c and accordingly the openings 210c to 214c axially so that the elongated recesses of the openings, extending in the axial direction, no longer overlap in projection on the valve axis B''. so that in place of the elongated recesses, ring-shaped channels in the manner of the ring- shaped channel 202c could be provided on the outer periphery of the second valve member 94c.

53 In this case, the second valve member 94c could adopt any rotary position relative to the valve housing 90c, as is also the case for the first valve member (also already shown in the embodiment of Figures 10 and 11).

To summarise, the invention relates to an actuating device for a friction clutch located in the drive train of a motor vehicle between an internal combustion engine and a gearbox in a housing bell, comprising a release bearing arrangement and a positioning servo arrangement comprising a pressure medium power cylinder arrangement, for the release bearing arrangement, the positioning servo arrangement comprising a control valve connected to a source of pressure medium. The control valve comprises a valve arrangement, which depending on an actual value representing the axial position of the release bearing arrangement and a command value representing a reference position of the release bearing arrangement can be switched between at least two control states. In a first control state, a pressure medium connection exists between the pressure medium power cylinder arrangement and the pressure medium source and a second control state, a pressure medium connection exists between the pressure medium power cylinder arrangement and a pre s sure- compensating opening. The valve arrangement comprises two valve members able to move relative to each other and relative to a valve housing, the command value being represented by the position of a first of the two valve members and the actual value being represented by the position of a second of the two valve members relative to the valve housing and a differential value associated with the actual value and the command value being represented by the position of the two valve members relative to each other.

54

Claims

Claims

1. An actuating device (10) for a friction clutch located in the drive train of a motor vehicle, between an internal combustion engine and a gearbox in a housing (12); said device comprising a release bearing (32) able to move substantially coaxially with respect to the friction clutch, for operating the friction clutch; 10 a positioning servo with a pressure medium cylinder arrangement (14) acting on the release bearing (32) and a control valve arrangement (42) connected to a source of pressure medium (51) for operating the cylinder arrangement (14) depending on a command value representing a reference 15 position and an actual value representing the axial position of the release bearing (32); wherein the control valve arrangement (42) comprises two valve members (92a, 94a, 96a; 92b, 94b) able to move relative to each other and relative to a valve housing (40, 90a, 90b) such that 20 the command value is represented by the position of a first (92a; 92b) of the two valve members and the actual value being represented by the position of a second (94a; 94b) of the two valve members relative to the valve housing (40; 90a; 90b) and a differential value is represented by the position of the two 25 valve members (92a, 94a; 92b, 94b) relative to each other and the control valve arrangement is adjustable between a first control state connecting the chamber of the pressure cylinder arrangement (14) to the source of pressure medium (51) and a second control state connecting the chamber of the pressure 30 cylinder arrangement (14) to a pressure-compensating opening (70), which valve arrangement can be switched between the two control states depending on the differential value associated with the actual value and the command value.

2. An actuating device according to claim 1 wherein the cylinder arrangement (14) employs a ring cylinder (16) substantially concentric with the axis of the clutch and located within the housing (12).

3. An actuating device according to Claim 1 or 2, wherein the control valve arrangement is also adjustable depending on the differential value in to a third control state in which the chamber of the cylinder arrangement is closed in a substantially pressure medium-tight manner.

4. An actuating device according to any one of the preceding Claims, wherein the control valve arrangement (42) has a first connector (54) for receiving a command signal indicating the command value, and actual value signal release bearing (32) a second connector (76) for receiving an indicating the actual value derived from the 5. An actuating device according to Claim 4, wherein the command signal and the actual value signal act independently of one another directly on an associated respective one valve member of the two valve members (92a, 92b, 94a, 94b).

6. An actuating device according to Claim 4 or 5, wherein 25 the actual value signal is an hydraulic, pneumatic, mechanical or electrical signal represented in particular by a pressuref a volume, a force, a displacement, an angle, a current intensity or a voltage, and converter means serve for converting the actual value signal into the actual value.

An actuating device according to one of the preceding Claims, wherein the positioning servo comprises a mechanical position-regulating arrangement (42, 64, 16, 72, 74) with a transducer (72) connected to or connectable to the release 56 bearing mechanically to monitor directly or indirectly the position of the release bearing (32).

8. An actuating device according to Claim 7, wherein the 5 transducer (72; 160a; 226b) acts on the second valve member (94a; 94b).

9. An actuating device according to Claim 8, wherein the second valve member (94a) is coupled directly or indirectly to the release bearing or to the release bearing side (162a) of the cylinder (14a).

10. An actuating device according to Claim 8, wherein the second valve member (94b), is coupled indirectly with pretension to the release bearing or to the release bearing side (162b) of the cylinder arrangement (14b).

11. An actuating device according to one of the preceding Claims, wherein the command signal is an hydraulic, pneumatic, electrical or optical signal represented in particular by a pressure. a volume, a force, a displacement, an angle, a current, a voltage or a light intensity, and converter means (114a, 234b) serves for converting the command signal into the command value.

12. An actuating device according to Claim 11, wherein the converter means serves for converting a pneumatic or hydraulic command signal and comprises a pre-tensioned piston (114a; 236b) which is coupled directly or indirectly to the first valve member (92a; 92b).

13. An actuating device according to one of the preceding Claims, wherein the control valve arrangement also comprises an auxiliary valve member (96a) able to move relative to the valve 57 housing (90a), which member cooperates with the first (92a) or/and second (94a) valve member, in order to provide at least one of the control states.

14. An actuating device according to Claim 13, wherein the auxiliary valve member (96a) comprises a section (142a) associated with the first valve member (92a), on which the first valve member (92a) acts for the entrainment of the auxiliary valve member (96a) and/or for interrupting at least one pressure medium connection within the control valve arrangement (42a).

15. An actuating device according to Claim 13 or 14, wherein the auxiliary valve member (96a) comprises a section (144a) associated with the second valve member (94a), on which the second valve member (94a) acts for the entrainment of the auxiliary valve member (96a) and/or for interrupting at least one pressure medium connection within the control valve (42a), and/or for blocking a pressure medium connection between the pressure medium source (51a) and the pressure-compensating opening (70a).

16. An actuating device according to one of Claims 13 to 15, and further comprising pre-tensioning means, for pre-tensioning the auxiliary valve member (96a) in the direction of action of the second valve member (94a) on the associated section of the auxiliary valve member (144a) and/or in the direction of action of the first valve member (92a) on the associated section (142a) of the auxiliary valve member (96a).

17. An actuating device according to any one of the preceding Claims, wherein the first valve member (92a) and the second valve member (94a) comprise at least one abutment or engagement section (102a, 114a, 128a) for limiting the range of movement of the two valve members relative to each other.

58 18. An actuating device according to any one of the preceding claims, wherein at least one of the f irst and second valve members (92a, 94a) and the housing (90a) have engagement 5 sections (102a, 114a, 128a) for limiting the range of movement of at least one of the valve members relative to the housing.

19. An actuating device according to Claim 17, wherein both valve members have engagement sections and when the associated 10 engagement sections (114a, 128a) of the first (92a) and second (94a) valve member engage one on the other, a pressure medium connection is created within the control valve arrangement (42a).

20. An actuating device according to any one of the preceding Claims, wherein pre-tensioning means (132a) acts between the first (92a) and the second (94a) valve member.

21. An actuating device according to Claim 20, when 20 dependent on claim 18 or 19, wherein the tension of the pre- tensioning means (132a) active between the first (92a) and the second (94a) valve member is at a maximum at the time of abutment of the engagement sections (114a, 128a) of the first (92a) and second (94a) valve members.

22. An actuating device according to one of the preceding Claims, wherein one of the valve members (92b; 92c) comprises at least one section (224b; 306c, 308c) with a control edge, which cooperates with at least three pressure medium openings (7 Ob, 30 184b, 202b; 210c, 212c, 214c) in the other valve member (92b; 94c) and in the valve housing (90b; 90c), in order, in at least one relative position of the two valve members (92b, 94b; 92c, 94c) to each other, at the time of a movement of one valve member relative to the other valve member in one direction due 59 to the movement of at least one control edge (224b; 306c, 308c) past at least one of the pressure medium openings, to interrupt or produce a first pressure medium connection within the control valve arrangement, and to produce or interrupt another pressure medium connection within the control valve arrangement (42b; 42c).

23. An actuating device according to any one of the preceding Claims, wherein one of the valve members (92b, 94b) 10 comprises at least one pinlike engagement section (220b), which engages in an associated slot-like recess (222b) in the other valve member (94b), the recess (222b) being limited at both ends by stops, for limiting the range of movement of the two valve members (92b, 94b) relative to each other.

24. An actuating device according to any one of the preceding Claims, wherein the control valve arrangement (42) in a basic state of the actuating device without actuation of the clutch, adopts the control state connecting the pressure20 compensating opening (70) to the cylinder arrangement (14).

25. An actuating device according to any one of the preceding Claims, wherein at least the first valve member (92a) and the second valve member (94a) are mounted to be displaceable 25 along a valve axis (B) in a recess (98a) of the valve housing (90a), and the actual value and the command value are represented by axial positions of the respective valve member (92a; 94a).

26. An actuating device according to Claim 24, wherein at least one of the valve members (92a, 94a), is constructed at least in a certain region as a ring member coaxial with the axis of the valve arrangement and surrounds at least one other (92a; 92a, 94a) of these valve members, at least in a region, radially on the outside.

27. An actuating device-according to Claim 25 or 26, wherein the recess is a ring-shaped recess (98a), which at a radial distance comprises ringshaped cylindrical walls extending coaxially and which extends around a tube member (106a) stationary with respect to the valve housing (90a), and extending coaxially with respect to the valve axis (B), the tube member comprising in the region of its free end a pressure medium passage opening (108a) open in particular in the axial direction, as part of at least one pressure medium connection within the control valve arrangement (42a).

28. An actuating device according to Claim 27, wherein the first valve member (92a) comprises a ring section (114a), which surrounds the tube member (106a) at least in regions radially on the outside, and at least one ring-shaped sealing member (118a) acts to seal between the ring section (114a) and the tube member (106a).

29. An actuating device according to Claim 27 or 28, wherein at least one ring-shaped sealing member (116a) acts in a sealing manner between the radially outer ring-shaped cylindrical wall of the ring-shaped recess (98a) and the first valve member (92a).

30. An actuating device according to Claim 28, wherein the first valve member (92a) comprises a tube section (120a) axially adjoining the ring section, which tube section surrounds the tube member (106a) at least in regions, radially on the outside, and at least one ring-shaped sealing member (122a) acts to seal between the tube section (120a) and the tube member (106a).

61 31. An actuating device according to Claim 13 or any one of Claims 14 to 30 when appended to Claim 13 wherein the auxiliary valve member (96a) is constructed as a ring member to surround the first valve member (92a), at least in regions, radially on the outside.

32. An actuating device according to Claim 31 when dependent on Claim 30, wherein the first valve member (92a) also comprises a closure section (124a) adjoining the tube section (120a), extending substantially in the radial direction and covering the pressure medium passage opening (108a) in the free end of the tube member (106a) in the axial direction, by which the first valve member (92a) acts on an associated ring-shaped and radially inwardly projecting section (142a) of the auxiliary valve member (96a) for entrainment and/or for interrupting the at least one pressure medium connection.

33. An actuating device according to Claim 32, wherein the section (142a) of the auxiliary valve member (96a) defines a pressure medium passage opening (154a) in the radial direction, which is part of a pressure medium connection within the control valve arrangement (42a).

34. An actuating device according to Claim 32 or 33, wherein 25 the first valve member (92a), in the end region of the tube section (120a) adjacent to the closure section (124a), comprises at least one pressure medium passage opening (126a), open in particular in the radial direction, as part of at least one pressure medium connection within the control valve.

35. An actuating device according to Claim 26 or any one of Claims 27 to 34 when dependent on Claim 26, wherein the second valve member (94a) is constructed as a ring member to surround the first valve member (92a).

62 36. An actuating device according to Claim 35 when dependent on claim 31, wherein at least one ring-shaped sealing member (150a) acts to seal between the second valve member (94a) and 5 the auxiliary valve member (96a).

37. An actuating device according to Claim 36 when dependent on Claim 27, wherein said ring-shaped sealing member (150a) acts to seal between the radially outer ring-shaped cylindrical wall of the ring recess (98a) and the second valve member (94a).

38. An actuating device according to Claim 32 or any one of Claims 33 to 37 when dependent on Claim 32, wherein formed radially between the tube section (120a) and the auxiliary valve member (96a) and/or radially between the second valve member (94a) and a ring-shaped cylindrical wall of the valve housing (90a) defining the recess (98a) radially on the outside is a respective pressure medium channel (140a, 152a).

39. An actuating device according to Claim 38, wherein a pressure medium connection between the pressure medium channels (140, 152a) is able to be interrupted by the action of the second valve member (94a) on this associated section (144a) of the auxiliary valve member (96a), and the pressure medium connection comprises at least one pressure medium passage (138a) open in the radial direction in the second valve member (94a) and/or a ring-shaped chamber defined by the tube section (120a), the auxiliary valve member (96a) or the second valve member (94a).

40. An actuating device according to Claim 27 or any one of the Claims 28 to 39 when appended to Claim 27, and further comprising a valve connection (48a) connected to the pressure medium source (51a) and/or a valve connection (54a) connected to 63 the command signal generator (60a) and comprising a bore (104a; 100a) in the valve housing (90a), opening into the recess (98a).

41. An actuating device according to Claim 40, wherein the bore (100a) of the valve connection (54a) connected to the command signal generator (60a) opens into the recess in the region of a recess base (102a) closing off the recess (98a) on one axial side, and lying opposite the recess base is the ring section (114a) of the first valve member (92a) serving as a piston.

42. An actuating device according to Claim 40, wherein the bore (104a) of the valve connection (48a) connected to the pressure medium source (51a) opens into the recess (98a) in an end region of the recess adjoining a recess opening, which is open in the axial direction.

43. An actuating device according to Claim 42 and further comprising a valve connection connected to the cylinder 20 arrangement (14a) and comprising a first bore (108a) opening into the recess (98a), extending through the tube member (106a) and a second bore (110a), which adjoins the first bore (108a) and extends in the base of the recess (102a).

44. An actuating device according to one of Claims 1 to 24, wherein the first valve member (92b) and the second valve member (94b) are mounted to rotate about a valve axis (B') in a recess (180b) in the valve housing (90b), and the actual value and the command value are represented by rotary positions of the respective valve member (92b; 94b).

45. An actuating device according to Claim 44, wherein one of the valve members comprises a ring section (204b) coaxial 64 with the axis of the valve (BI), which surrounds the other valve member (92b) of the at least in regions radially on the outside.

46. An actuating device according to Claim 45, wherein the ring section (204b) of the one valve member (94b) surr.ounded radially on the outside by an inner peripheral surface of the valve housing (90b) and defining a recess (180b), comprises at least two openings (210b, 212b, 214b) extending in the peripheral direction, offset with respect to each other in the peripheral direction, separated from each other by a respective section (224b; 240b; 242b) of the ring section (204b) and open radially towards the inside and radially towards the outside, at least two bores (182b, 184b, 186b) in the housing (90b) open into the recess (180b) the openings of the bores being offset with respect to each other in the peripheral direction at least one rotary position of one valve member (94b) respectively covering another of the openings at least partly and that provided in the other valve member (92b) has at least one connecting channel, which in at least one relative rotary position of the two valve members (92b, 94b) with respect to each other is open with respect to two of the openings, so that the two openings of the through-bore (202b) are covered at least partly by respectively one other of the openings.

47. An actuating device according to Claim 46, wherein there are three bores (182, 184b, 186b), with three openings (210b, 212b, 214b) and one connecting channel, extending radially so that in at least one rotary position region of the two valve members (92b, 94b) relative to each other and relative to the valve housing (90b) by way of two (184b, 186b) of the bores, two (212b, 214b) of the openings and the connecting channel (202b) a pressure medium connection is produced between the pressure medium source (51b) and the cylinder arrangement (14b) and in at least one other rotary position region of the two valve members (92b, 94b) relative to each other and relative to the valve housing (90b), by way of two (182b, 186b) of the bores, two (210b, 214b) of the openings and the connecting channel (202b), a pressure medium connection is produced between the cylinder arrangement (14b) and the pressure- compensating opening (70b).

48. An actuating device according to Claim 46 or 47, wherein the sections (224b, 240b, 242b) of the ring section (204b) separating the openings (210b, 212b, 214b) from each other are dimensioned so that in at least one relative rotary position of the two valve members (92b, 94b) with respect to each other and/or in at least one rotary position of one valve member (94b) relative to the valve housing (90b), at least one channel opening of the connecting channel, in the other valve member (92b) and/or at least one of the apertures of the bores in the valve housing (90b) is closed by a respective section (224b) of the ring section (204b) which forms a control edge.

49. An actuating device according to Claim 48, wherein at least one rotary position of the two valve members (92b, 94b) relative to each other and relative to the valve housing (90b), neither a pressure medium connection between the cylinder arrangement (14b) and the pressure medium source (51b), nor a pressure medium connection between the cylinder arrangement (14b) and the pressure-compensating opening (70b) is produced.

50. An actuating device according to one of Claims 47 to 49, wherein the three bores (182b, 184b, 186b) are arranged with the same peripheral angle at a similar distance apart.

51. An actuating device according to one of Claims 47 to 50, wherein the three openings (210b, 212b, 214b) respectively cover an equally large peripheral angular region and are arranged with the same peripheral angle at a similar distance apart.

66 52. An actuating device according to Claim 50 or 51 wherein one of the three bores, (182b) is associated with the pressurecompensating opening (70b), another bore (184b) is associated with the pressure medium source (51b) and a further bore (186b) is associated with the cylinder arrangement (14b) and the bores follow each other in a predetermined direction of rotation, whereby in the basic state of the actuating device (10b), an aperture of the through-bore (202b) in the first valve member (92b) lies approximately opposite the bore (182b) associated with the pressure - compens at ing opening (70b), a section (204b) of the ring section (204b) of the second valve member (94b), forming a control edge, is offset in the direction of rotation with respect to the bore (182b) associated with the pressurecompensating opening (70b), but is closely adjacent to the latter, and to actuate the clutch, the first valve member (92b) is able to rotate in the direction of rotation with respect to the rotary position of the basic state, in particular to the maximum extent approximately as far as a rotary position, in which the aperture of the through-bore (202b) lies approximately opposite the bore (184b) associated with the pressure medium source (51b).

53. An actuating device according to any one of Claims 44 to 25 52, wherein the recess is constructed as a through-bore (180b) in the valve housing (90b) extending at right angles to the direction of movement of the release bearing, at one end of which the first valve member (92b) is accessible, and at the other end of which the second valve member (94b) is accessible.

54. An actuating device according to Claim 53 when dependent on Claim 10 wherein one end section (206b) of the second valve member (94b) projects from the through-bore (184b) in the valve housing (90b) and supports a rigidly coupled bracket (226b) as 67 the coupling member, which acts on the release bearing or the release bearing side (162b) of the cylinder arrangement (14b), through spring means (238b) acting on the bracket (226) and the valve housing (90b).

55. An actuating device according to Claim 54, wherein the spring means (238b) comprises a leg spring (238) located around the end section (208b) which is pre-tensioned against the latter, so that a linear movement of the release bearing or of the release bearing side (162b) of the cylinder arrangement (14b) can be converted by way of the bracket (226b) into a rotary movement of the second valve member (94b).

56. An actuating device according to Claim 53, 54 or 55 when dependent on Claim 12, wherein the pre-tensioned piston (236b) of the converter means is part of a cylinder-piston arrangement (234b), which is separate with respect to the valve members (92b, 94b), the piston (236b) of the cylinder-piston arrangement being moveable in one direction, which extends substantially at right angles to the axis of the valve (B') so that a linear movement of the piston (236b) can be converted by way of a coupling arrangement (230b, 232b), acting on the first valve member (92b), into a rotary movement of the first valve member (92b).

57. An actuating device according to any one of Claims 44 to 56, wherein surface sections of the valve housing (90b) and of the first (92b) and the second (94b) valve member, bear one against the other and are constructed as sealing and/or sliding surfaces, or as sliding surfaces in which case sealing means (216b, 218b) are active in a sealing manner between the surfaces.

68 58. An actuating device according to Claim 25, wherein apart from the first valve member (92c) and the second valve member (94c), no further valve member is mounted to slide in the recess (180c) of the valve housing (90c) along the valve axis (B'').

59. An actuating device according to Claim 58, wherein one of the valve members (92c, 94c) comprises a ring section (204c) coaxial with the valve axis (B''), which surrounds the other valve member (92c) at least in regions on the outside.

60. An actuating device according to Claim 59, wherein the ring section (204c) of the one valve member (94c) surrounded on the outside by an inner surface of the valve housing (90c), defining the recess (180c) and comprises at least two openings (210b, 212b, 214b), extending in the axial direction, offset with respect to each other in the axial direction and separated from each other by a respective section of the ring section (204c) and open towards the inside and outside, at least two bores (182c, 184c, 186c) in the valve housing (90c) open into the recess (180c), the orifices of the bores being offset with respect to each other in the axial direction and in at least one axial position of one valve member (94c) respectively cover another of the openings at least partly and is provided in the other valve member (92c) is at least one connecting channel (202c), in at least one relative axial position of the two valve members (92c, 94c), the channel being open with respect to two of the openings.

61. An actuating device according to Claim 60, wherein there are three bores (182c, 184c, 186c), three openings (210c, 212c, 214c) and one connecting channel (202c), extending along an outer surface of the other valve member (92c), in at least one axial position region of the two valve members (92c, 94c) relative to each other and relative to the valve housing (90c) 69 by way of two (184c, 186c) of the bores, two (212c, 214c) of the openings and the connecting channel (202c), a pressure medium connection is produced between the pressure medium source and the cylinder arrangement and in at least one other axial position region of the two valve members (92c, 94c) relative to each other and relative to the valve housing (90c), by way of two (182c, 186c) of the bores, two (210c, 214c) of the openings and the connecting channel (202c), a pressure medium connection is produced between the cylinder arrangement and the pressurecompensating opening (70c).

62. An actuating device according to Claim 60 or 61, wherein at least one axial position of the two valve members (92c, 94c) relative to each other and relative to the valve housing (90c), neither a pressure medium connection between the cylinder arrangement and the pressure medium source, nor a pressure medium connection between the cylinder arrangement and the pressure-compensating opening (70c) is produced.

63. An actuating device according to any one or more of the preceding Claims, wherein the control valve arrangement (42) is located within the housing (12), but is accessible from outside, for dismantlement.

64. An actuating device according to any one or more of the preceding Claims, wherein the release direction of the cylinder arrangement (14) and the release direction of the friction clutch are essentially parallel to each other and the clutch axis (A) and the cylinder arrangement axis (A) essentially coincide.

65. An actuating device according to any one or more of the preceding Claims, wherein the valve axis (B; B') and the power cylinder arrangement axis (A) have no point in common.

66. An actuating device according to Claim 65, wherein the valve axis (B) and the cylinder arrangement axis (A) are essentially parallel to each other.

67. An actuating device according to Claim 65, wherein the valve axis (B') and the cylinder arrangement axis (A) are substantially at right angles to each other in projection on a plane substantially parallel to both axes.

68. An actuating device according to any one or more of the preceding Claims, wherein the control valve arrangement (42) is detachably located on the cylinder arrangement (14).

69. An actuating device according to Claim 68, wherein a control valve unit or component (40) comprising the control valve arrangement (42) isoffset with respect to a cylinder component (14) comprising the cylinder arrangement (14), in a radial direction relative to the cylinder arrangement axis (A) and is detachably located on a radially outer section of the cylinder component (14).

70. An actuating device according to Claim 69, wherein the control valve component (40), is removable from the cylinder component (14) substantially in the radial direction after release of possible fastening or/and coupling means acting between the two components.

71. An actuating device according to any one or more of the preceding Claims, wherein the pressure medium is a pneumatic pressure medium.

72. An actuating device for use with friction clutches substantially as described herein with reference to, and as illustrated in any one accompanying drawings.

or more of the Figures of the