Friction clutch with rolling element supported pressure plate

Abstract

Friction clutch (1) for a motor vehicle drive train, comprising a pressure plate (2) which is rotatable about a longitudinal axis (X), a clutch cover (3) and at least one ramp device (4) which has at least one ramp (5) fixed to the pressure plate (2) or the clutch cover (3) and a rolling element (6) which can roll on the ramp (5), wherein the pressure plate (2), the rolling element (6), and the clutch cover (3) are coordinated with one another such that, by rotating the pressure plate (2) relative to the clutch cover (3) about the longitudinal axis (X), such a rolling movement of the rolling element (6) on the ramp (5) can be achieved that the pressure plate (2) is displaceable along the longitudinal axis (X) for clamping a clutch disc (13) in a power-transmitting manner, wherein the pressure plate (2) is radially supported by the rolling element (6), characterized in that further an actuator (14) is provided, the actuator (14) is an electric motor,which has a stator (15) rotationally coupled to the clutch cover (3) and a rotor (17) rotationally coupled to the pressure plate (2).

Description

[0001] The invention relates to a friction clutch for a motor vehicle drive train with a pressure plate which is rotatable about a longitudinal axis, with a clutch cover and at least one ramp device which has at least one ramp fixed to the pressure plate or the clutch cover and a rolling element which can roll on the ramp, wherein the pressure plate, the rolling element and the clutch cover are coordinated with one another in such a way that by rotating the pressure plate relative to the clutch cover about the longitudinal axis, such a rolling movement of the rolling element on the ramp can be achieved that the pressure plate can be displaced along the longitudinal axis for clamping a clutch disc in order to transmit power.

[0002] Clutches are typically used in automotive engineering to connect or decouple the crankshaft of an internal combustion engine with the input shaft of a manual transmission. An output shaft of the transmission is typically rotationally coupled to at least one drive wheel of the vehicle.

[0003] The present invention can be used with a single clutch, a double clutch, a single-disk clutch, a multi-disk clutch, or a multi-plate clutch. Furthermore, the friction clutch according to the invention can be actuated manually or automatically, with automated clutch actuation being preferred. Therefore, the present friction clutch can be combined with a manual transmission, an automated manual transmission, a dual-clutch transmission, a multi-step automatic transmission, or a continuously variable automatic transmission. The friction clutch according to the invention can be used with a single-mass flywheel, a dual-mass flywheel, or a clutch-disk-side torsional vibration damper.

[0004] A friction clutch of the type mentioned above is known, for example, from DE 10 2012 206 318 A1, which describes a friction clutch with a rotationally driven counterpressure plate device containing a counterpressure plate and a housing, and with a pressure plate that is axially displaceable relative to the counterpressure plate by means of an actuator device in order to axially clamp friction linings of a clutch disc. The pressure plate is delimited relative to the counterpressure plate device and is received in a centered manner by the actuator device so that it can rotate counter to a direction of rotation of the counterpressure plate device, and ramps that are oriented and distributed over the circumference and that rise axially are effectively provided between the counterpressure plate device and the pressure plate. Support rollers that roll on the ramps are accommodated in the counterpressure plate device. Furthermore, centering rollers are provided, the axes of which are arranged orthogonally to a ramp surface of the ramps.

[0005] The friction clutch known from DE 10 2012 206 318 A1 essentially provides axially acting support rollers, whose rotational axes lie essentially in a radial plane around the longitudinal axis, as well as essentially radially acting or centering rollers, whose rotational axes are essentially parallel to the longitudinal axis. This results in a high number of parts and complex assembly.

[0006] According to an unpublished prior art known to the applicant of the present disclosure, a motor vehicle clutch is known having a clutch housing in which a clutch disc is clamped between a pressure plate and a counterpressure plate, wherein the pressure plate rotatably bears against a movement-specifying member such that, upon rotation of the pressure plate relative to the movement-specifying member, an axial movement of the pressure plate is forced, wherein a brake acting against a stationary clutch / gearbox housing is further connected such that, upon activation, it provides a torque that causes the relative rotational movement between the movement-specifying member and the pressure plate. The movement-specifying member preferably has a contour in the manner of a ramp, on which a contact member, such as a roller connected to the pressure plate, rests in a rolling manner.The motion control element is therefore essentially oriented in the axial direction. The ramp can be part of the pressure plate or the clutch housing. Radial guidance of the pressure plate is neither proposed nor described.

[0007] Furthermore, a friction clutch with an actuating device is known from DE 10 2013 215 024 A1. The friction clutch has a pressure plate, a counterpressure plate and a clutch cover, wherein a clutch disc can be received between the pressure plate and the counterpressure plate, wherein the pressure plate is annular, the actuating device has a ramp device between the pressure plate and the clutch cover for the axial displacement of the pressure plate and the actuating device further has an actuator for rotating the pressure plate in the circumferential direction relative to the clutch cover, wherein the clutch cover has a support element for which the actuator supports the pressure plate radially inward or outward on the support element and is supported radially outward or inward on the pressure plate. In particular, a longitudinal expansion element is proposed as the actuator, which has at least one piezo element or a stack of piezo elements.Furthermore, the ramp device preferably has at least one run-up ramp and a rolling element supported thereon. The ramp device is arranged between the pressure plate and the clutch cover, the run-up ramp being attached to the pressure plate and / or the clutch cover, and the rolling element is rotatably mounted either on the clutch cover, on the pressure plate, or between a run-up ramp on the pressure plate and a run-up ramp on the clutch cover. The ramp device thus acts in the axial direction, and the pressure plate is supported in the radial direction by means of the actuator or linear expansion element.

[0008] Another clutch arrangement in an axle differential is known from DE 102 52 974 A1. The clutch's disk pack is actuated by a ramp device.

[0009] The present invention aims to simplify a generic friction clutch and make it more cost-effective. In particular, the automation and / or electrification of the generic friction clutch should be enabled and / or improved. In particular, the financial outlay should at least not increase and preferably be reduced compared to a conventional friction clutch with wear adjustment and hydraulic actuation. For safety reasons, it is preferred if the friction clutch according to the invention is suitable for being designed as a self-opening or "normally open" friction clutch.

[0010] The object is achieved according to the invention by the characterizing features of claim 1. In a generic friction clutch, the pressure plate is radially supported by the rolling element. This makes it possible to fulfill the functions of both axial support or guidance and radial support or guidance using a single component or assembly. Thus, two separate components or assemblies are not required. This results in reduced costs and assembly effort.

[0011] The longitudinal axis may also be referred to as a longitudinal direction or the like. Unless otherwise specified, terms such as "radial," "radial direction," "tangential," "circumferential direction," or the like refer to the longitudinal axis.

[0012] Further developments according to the invention are claimed in the subclaims and are described below.

[0013] Having the clutch cover adjacent to the pressure plate along its longitudinal axis allows for particularly direct power transmission. This results in a simple design, which allows for cost savings.

[0014] It can be provided that the at least one ramp device has a ramp fixed to the pressure plate and a ramp fixed to the clutch cover. Thus, the rolling element is guided between two ramps. On the one hand, this enables the rolling element to be guided particularly reliably, thus ensuring and / or increasing the functional reliability of the friction clutch. On the other hand, this enables the axial displacement to be increased while maintaining the ramp pitch and the angle of rotation about the longitudinal axis, thus reducing the axial installation space of the ramp device.

[0015] If the ramps of at least one ramp device are designed to be opposite each other, constant forces acting on the rolling element during rolling are achieved, so that the reliability of the friction clutch can be further increased.

[0016] It may be provided that the ramp attached to the pressure plate is formed integrally with the pressure plate, thus reducing manufacturing costs. Additionally or alternatively, it may be provided that the ramp formed on the clutch cover is formed integrally with the clutch cover; this also results in reduced manufacturing costs.

[0017] Smaller, and thus lighter and more cost-effective, rolling elements or ramp devices can be used if a plurality of ramp devices is provided. It is preferred to provide a maximum of 10 ramp devices. It is particularly preferred to provide three or four ramp devices.

[0018] A particularly uniform load distribution in the pressure plate and in the clutch cover results when the ramp devices of the plurality of ramp devices are evenly distributed in a circumferential direction around the longitudinal axis.

[0019] When cage-guided rolling elements are used, the reliability of the friction clutch is increased, as the position of each rolling element on the assigned ramp(s) is reliably ensured. A cage guiding the rolling element(s) can compensate or absorb centrifugal forces acting on the rolling element(s).

[0020] Rolling elements that can be considered are, in particular, spherical, roller-like, cylindrical, conical, truncated cone-like, spherical or barrel-like.

[0021] The ramp can also be referred to as a traverse, a rolling element raceway, a rolling element track, a raceway, or simply a track. The ramp device, or the multitude of ramp devices, can be described as angular contact ball bearing-like, helix-like, or ball screw-like, whereby the term "ball" is not to be construed as limiting.

[0022] According to a preferred embodiment, the ramps or tracks extend in the circumferential direction, are simultaneously oriented both radially and axially, and have an axial gradient along the circumferential direction. The gradient or inclination in the axial direction corresponds to an increment of actuation. Thus, the ramps have a geometry that can be manufactured in one manufacturing step, such as pressing or milling.

[0023] It could also be stated that the at least one ramp device is designed in such a way that by rotating the pressure plate relative to the clutch cover, the pressure plate executes a screwing movement or a rotational movement towards or away from the clutch cover along the longitudinal axis.

[0024] If the ramp attached to the pressure plate and the pressure plate are designed as two separate components, this allows for a high degree of flexibility, similar to a modular system. If the ramp attached to the clutch cover and the clutch cover are designed as separate components, this also allows for a high degree of flexibility, similar to a modular system.

[0025] According to a further aspect, which can also be claimed independently, at least one axial spring is arranged between the pressure plate and the clutch cover, which preloads the ramp device along the longitudinal axis. The term "axial spring" can be replaced or clarified by the terms "axially acting spring" and / or "axially oriented spring". On the one hand, the axial springs can assume a transport securing function when rolling elements are inserted at least partially axially between the pressure plate and the clutch cover, namely in such a way that the clutch cover and the pressure plate are pulled towards each other along the longitudinal axis. On the other hand, the axial springs can assume a securing function in order to have a restoring effect on the pressure plate in a displaced state.

[0026] In a further development, a plurality of axial springs can be provided. This increases reliability in the event of a spring break, while also allowing the installation of weaker, smaller, and therefore lighter springs. Preferably, the axial springs are evenly distributed circumferentially to create a uniform axial preload between the pressure plate and the clutch cover.

[0027] It is preferred if the axial springs are tension elements or tension springs in order to achieve the aforementioned effects in a structurally simple manner.

[0028] In a further development, it can be provided that a guide element, such as a shell, a guide plate or a bolt, is provided radially outwardly on a section of the axial spring with respect to the longitudinal axis of the friction clutch in order to absorb, divert or compensate for centrifugal forces acting on the axial spring.

[0029] According to a further aspect of the invention, which can also be claimed independently, at least one tangential spring is arranged between the pressure plate and the clutch cover. The term "tangential spring" can be replaced or clarified by the terms "tangentially acting spring" and / or "tangentially oriented spring." Such a tangential spring can be used to reset a rotation of the pressure plate that causes displacement of the pressure plate. In this respect, the tangential spring serves a safety function in the sense of a normally open clutch.

[0030] It is preferable if the position or arrangement of the tangential spring within the adjustment range of the pressure plate corresponds, on average, to a ramp gradient. This promotes the return of the pressure plate.

[0031] It is preferred if the tangential spring is provided kinematically parallel to the at least one ramp device in order to kinematically easily reset the pressure plate. In other words, it can be provided that the at least one disc spring preloads the pressure plate relative to the clutch cover in a clutch disc-unclamping direction in order to act as a safety function in the sense of a normally open clutch ("safe-fail principle").

[0032] When the friction clutch rotates, the tangential spring can be subjected to centrifugal force, which can change the spring characteristics. To counteract this effect, the tangential spring can be provided with an arc-like shape and / or that the tangential spring is mounted at least radially outward in / on an arc-like spring guide. It can be specified that the arc-like spring guide extends essentially in the circumferential direction. The tangential spring can be designed as an arc spring, which acts similarly to the design known from dual-mass flywheels between a stop or holding element on the pressure plate side and a stop or holding element on the clutch cover side.

[0033] In a further development, a plurality of tangential springs can be provided. This increases reliability in the event of a spring break, while also allowing the use of weaker, smaller, and thus lighter springs. Preferably, the tangential springs are evenly distributed circumferentially to create a uniform tangential preload between the pressure plate and the clutch cover.

[0034] It is preferred if the tangential springs are tension elements or tension springs in order to achieve the aforementioned effects in a structurally simple manner.

[0035] It is preferred if the axial spring is attached directly to the pressure plate and / or if the axial spring is attached directly to the clutch cover and / or if the tangential spring is attached directly to the pressure plate and / or if the tangential spring is attached directly to the clutch cover. By means of a direct attachment, the number of components, and thus the weight, and / or the number of assembly steps can be reduced, thus resulting in a smaller, lighter, and cheaper friction clutch.

[0036] It can also be provided to provide one and / or a spring carrier or spring carrier or a spring support element or spring support element on the pressure plate and / or on the clutch cover, so that in order to simplify assembly of the friction clutch, the spring is first attached to the spring carrier before the spring carrier is attached to the clutch cover or to the pressure plate. If load-bearing areas are only required in certain sections of the pressure plate or in the clutch cover, the spring carrier can be provided in place of the load-bearing area in the area of ​​a weight-saving recess to save weight. If the spring carrier is a sheet metal component, the spring carrier can be of simple construction and lightweight.

[0037] The pressure plate and / or the clutch cover may be a cast component or a sheet metal component. It is preferred if the pressure plate and / or the clutch cover are made of metal.

[0038] According to the invention, an actuator is further provided which has a stator rotationally coupled to the clutch cover and a rotor rotationally coupled to the pressure plate. The term "rotationally coupled" refers to a rotation of the coupled parts about the longitudinal axis, in such a way that, as described using the example of the clutch cover and the stator, a rotation of the clutch cover about the longitudinal axis causes or causes a rotation of the stator about the longitudinal axis. By means of the actuator, a rotation of the pressure plate relative to the clutch cover about the longitudinal axis can be caused. In this case, the actuator is advantageously independent of an absolute rotational movement of the clutch cover and the pressure plate about the longitudinal axis, so that a control or a driver of the actuator for relative rotation can be designed accordingly simply.Here and in the following, the term “relative twisting” refers to a twisting of the pressure plate relative to the clutch cover or to a twisting of the clutch cover relative to the pressure plate.

[0039] The stator can also be described as a quasi-stationary outer housing of the actuator. The term "quasi-stationary" refers to a local coordinate system fixed to the clutch cover.

[0040] The stator can, for example, have a coil of the actuator, in particular an electrical coil or a coil through which electrical current flows, or a plurality of coils of the actuator. In this respect, the stator can be referred to as a coil carrier. An actuator with coils represents a common actuator design, so proven knowledge or supplied parts can be used. This enables a cost-effective actuator.

[0041] The rotor can have one magnet or a plurality of magnets. It is preferred if the magnet is a permanent magnet. The same applies to the plurality of magnets. In this respect, the rotor can also be referred to as a magnet carrier. An actuator with one magnet or a plurality of magnets allows for the use of proven expertise or supplier parts. This enables a cost-effective actuator and thus a cost-effective friction clutch.

[0042] According to a preferred embodiment, the actuator is designed as an electrically operated internal rotor motor.

[0043] It should not go unmentioned at this point that the stator can also be designed as a magnet carrier and / or the rotor as a coil carrier.

[0044] If the actuator is designed as a hydraulic actuator, in particular of the rotary piston type, the friction clutch according to the invention can be combined with a known hydraulic clutch actuation. Such hydraulic actuators are also known, for example, from the field of camshaft adjusters. For example, it is conceivable to provide a rotary piston type actuator in which one chamber can be connected to a clutch pedal or a pump via a hydraulic connection, while the other chamber is spring-loaded. In favor of a tangential spring as described above, the spring-loaded chamber could also be omitted entirely, thus further reducing costs.

[0045] Arranging the rotor and stator concentrically with each other allows for easy coupling to the clutch cover or pressure plate. To save axial space, it is preferred if the stator is mounted radially within the rotor, or if the rotor is mounted radially within the stator.

[0046] It is preferred if the rotor and / or the stator are arranged and configured such that an axle or shaft for driving the clutch cover and / or the clutch disc can be passed through. This can be achieved, for example, by designing the rotor and / or the stator as a hollow cylinder.

[0047] To achieve a replaceable or interchangeable design, as well as a design that is easy to manufacture and assemble, it is preferred if the clutch cover has a clutch cover flange and the stator has a stator flange that is opposite to the clutch cover flange. For the same reasons, it is preferred if the pressure plate has a pressure plate flange and the rotor has a rotor flange that is opposite to the pressure plate flange.

[0048] According to a further aspect of the invention, the rotor can be operatively connected to the pressure plate directly or via a gear mechanism. A planetary gear mechanism is proposed as the gear mechanism. The gear mechanism has the advantage of enabling a compact actuator through torque transmission. This not only reduces the overall installation space required for the friction clutch but also reduces the weight of the friction clutch. For the same reasons, a gear mechanism can be provided additionally or alternatively between the stator and the clutch cover.

[0049] Particularly suitable transmissions are static or quasi-static power or torque-transmitting transmissions. Examples include hydrostatic transmissions, force-locking transmissions such as friction gears, or positive-locking transmissions such as gear transmissions. The advantage of static or quasi-static power or torque-transmitting transmissions is that only a reduced energy input or no energy input at all is required to keep the friction clutch actuated, i.e., to maintain a relative rotation. This allows the energy requirement of the friction clutch to be reduced, so that the friction clutch according to the invention enables fuel savings or general operating cost savings.

[0050] A planetary gear is proposed in particular as the transmission design. More precisely, a planetary gear comprising a sun gear, a planet carrier with preferably three planets, and a ring gear is proposed. This encompasses every kinematic variant of a rotary coupling of the three components—ring gear, planet carrier, and sun gear—with the components or assemblies: pressure plate, clutch cover, rotor, and stator. For example, the planet carrier can be attached to the pressure plate. For example, the planet carrier can be attached to the rotor. For example, the clutch cover can be attached to the stator and the planet carrier, the rotor to the sun gear, and the pressure plate to the ring gear.

[0051] For weight savings, it is particularly recommended to mount the individual planets on the planet carrier using plain bearings. For system reliability, a captive device, such as a snap ring, can be provided to secure the planets to the planet carrier.

[0052] The aforementioned designs of a planetary gear enable the use of a small, lightweight actuator due to a torque transmission.

[0053] If an active component of the actuator, such as a coil, is provided so that it rotates with the pressure plate or the clutch cover, an energy transfer to the actuator that enables rotation may be necessary. If the actuator is a hydraulic actuator, the use of a hydraulic rotary feedthrough is proposed. If the actuator is electrically operated, i.e. if the actuator is an electric motor, an inductive energy transfer is proposed. More precisely, an inductive energy transfer device arranged axially to the active component of the actuator is proposed. Alternatively or additionally, an inductive energy transfer device arranged radially to the active component of the actuator is proposed. Inductive energy transfer devices have the advantage that they are not subject to aging, so that the service life of the friction clutch can be increased.If the actuator is an electric actuator, a contact energy transmission device can also be arranged axially and / or radially to the active component of the actuator. Such a contact energy transmission device can be, for example, spring-loaded carbon pins or brushes. It is preferred if the axially and / or radially arranged energy transmission device is adjacent to the active component of the actuator in order to achieve a compact overall system and short transmission paths.

[0054] According to a further aspect of the present invention, which can also be claimed independently, it is proposed to provide a plurality of actuators, such as electric motors. These actuators can, for example, be provided fastened to the clutch cover. These actuators can be provided in an operative relationship with the pressure plate, driving the clutch cover through the clutch cover. Depending on the spatial or kinematic requirements, the actuators of the plurality of actuators can be attached or mounted on the clutch cover axially parallel to the longitudinal axis or at an angle, for example with the interposition of an angular gear. A plurality of actuators can be advantageous compared to a single actuator in terms of power-to-weight ratio.

[0055] To achieve or ensure consistent actuation of the friction clutch, a speed-dependent logic can be provided, which provides or outputs an engine control variable depending on the speed of the clutch cover and / or the speed of the pressure plate. This has the advantage of compensating for centrifugal force effects. In particular, the speed-dependent logic can be provided in a control unit or a driver of the actuator.

[0056] In order to enable a creeping gear, it is proposed to provide a logic controlling clutch slip at a predetermined value in the control unit or the driver of the actuator.

[0057] The actuator's fuel efficiency can be increased by incorporating a braking device, such as an electromagnetic brake, into the actuator. This braking device enables energy-efficient maintenance of a relative rotational position. If the brake is an electrically released brake, energy can be saved during the applied-hold period. If the brake is an electrically closed brake, safety requirements such as a normally open brake can be met.

[0058] If the actuator, or the actuator and the gearing between the pressure plate and the clutch cover, are non-self-locking, this enables a normally open friction clutch that meets safety requirements. It is advantageous if the actuator is supplied with power inductively. Alternatively, known power supply methods, such as using brushes, are certainly conceivable.

[0059] To summarize and highlight the proposal, among other things, is that after a gear is engaged in a vehicle transmission, an actuator such as an electric motor attached to the friction clutch rotates the pressure plate relative to the clutch cover. This causes the rolling elements or running elements to roll on their inclined raceways. The pressure plate therefore covers an axial path. This rotation is maintained until a desired or predetermined contact pressure of the pressure plate is reached. Slippage conditions in the clutch can be adjusted using suitable logic. In one embodiment, the friction clutch according to the invention can therefore have the advantage that a hydraulic path for clutch actuation and / or a device for wear adjustment can be dispensed with. The friction clutch according to the invention therefore enables significant cost savings.Particularly when a planetary gear is provided, in conjunction with the inclined ramps or tracks, the advantage is that even low drive torques from the actuator are sufficient to generate the required clutch actuation forces. Furthermore, the displacement travel of the pressure plate or the clutch actuation travel can be limited to the necessary extent.

[0060] In other words, to summarize briefly, the friction clutch according to the invention, according to one embodiment, provides a normally open friction clutch in order to satisfy safety aspects. Furthermore, a co-rotating actuator or actuator drive, such as an electric motor, is proposed. Furthermore, a transmission element is proposed, such as a magnet carrier or a rotor carrier, in order to transmit a rotor movement of the electric motor to the pressure plate or pressure disk in order to thereby achieve a relative movement or relative rotation or relative rotation between the pressure plate and the clutch cover. By providing rolling elements or rolling bodies and ramps between the clutch cover and the pressure plate, the relative rotation results in an axial displacement of the pressure plate. A gear, preferably a planetary gear, is proposed. In this case, the planet carrier can, for example, be connected to the magnet carrier, i.e., for example.The gear unit can be connected to the rotor, with the gearbox acting as a transmission link between the rotor and the pressure plate. If the rolling elements are radially confined, for example, by means of a cage, this has the additional benefit of compensating or absorbing any centrifugal force acting on the rolling elements. The function of the normally open friction clutch can be realized with tangentially acting return springs. The function of a transport lock can be realized with axially acting return springs.

[0061] The invention is described below using several embodiments. They depict: Fig. 1 is a perspective top view of a first embodiment of the invention, wherein the friction clutch is cut away for illustration purposes and a clutch cover is omitted, Fig. 2 a sectional perspective view of a clutch cover according to the first embodiment, Fig. 3 a cross section along a longitudinal axis of the friction clutch according to the first embodiment, Fig. 4 an enlarged view of the Fig. 3 area marked IV, Fig. 5 an enlarged view of the Fig. 3 area marked with V, Fig. 6 an enlarged view of the Fig. 3 area marked VI according to the first embodiment, Fig. 7 an enlarged view corresponding to the Fig. 3 of a friction clutch according to a second embodiment of the invention, marked VI, Fig. 8 is a perspective top view of the friction clutch according to the second embodiment, wherein a clutch cover is omitted for illustration purposes, and Fig. 9 a perspective view of the friction clutch according to the second embodiment.

[0062] The figures are merely schematic and serve only to aid understanding of the invention. The same or comparable elements are provided with the same reference numerals. Features of one embodiment may also be included in the other embodiments. They are therefore interchangeable.

[0063] A first embodiment of the invention is described below with reference to Fig. 1 to 6. A friction clutch 1 according to the invention according to the first embodiment comprises a pressure plate 2 and a clutch cover 3. The friction clutch 1 is rotatable overall about a longitudinal axis X. The longitudinal axis X simultaneously defines a radial direction Y and a circumferential direction Z, cf. Fig. 3.

[0064] The friction clutch 1 has three ramp devices 4, each with two ramps 5 and each with a rolling element 6. In the present case, the ramps 6, which can also be referred to as raceways, are each provided as a pressure plate ramp 7 and a clutch cover ramp 8. The ramps 5 extend in the circumferential direction Z and are inclined in the axial direction X. The pressure plate ramps 7 point radially outwards, and the clutch cover ramps 8 point radially inwards. The pressure plate ramps 7 and the clutch cover ramps 8 are inclined in the same axial direction, i.e., apart from their radial orientation and their concave profile, they are parallel. The pressure plate ramps 7 and the clutch cover ramps 8 are therefore designed to be oppositely identical. The rolling elements 6 are spheres, and the pressure plate ramps 7 and the clutch cover ramps 8 are concave in opposite directions to the spherical rolling elements 6.

[0065] A spring carrier 9 is attached to the pressure plate 2. The spring carrier 9 attaches axial springs 10 and tangential springs 11 to the pressure plate 2. For this purpose, spring retaining holes 12 are formed in the spring carrier 9. Spring retaining holes 12 are also formed in the clutch cover 3. The axial springs 10 and the tangential springs 11 are each designed as tension springs in the form of helical springs. The axial springs 10 pull the pressure plate 2 and the clutch cover 3 together in the axial direction. As can be seen in particular from the Fig. 1, the tangential springs 11 are arranged approximately parallel to the raceways 5. Thus, the tangential springs 11 preload the pressure plate 2 relative to the clutch cover 3 in a circumferential direction. For example, the spring carrier 9 is flanged to the pressure plate 2 by means of rivets 37. As can be seen from the Fig. As can be seen from Figures 3 to 5, a clutch disc 13 is arranged axially next to the pressure plate 2.

[0066] In an initial position (not shown in the figure), the pressure plate 2 does not touch the clutch disc 13. When the pressure plate 2 is rotated relative to the clutch cover 3, the rolling elements 6 roll on the respective pressure plate ramp 7 and the respective clutch cover ramp 8, so that the pressure plate 2 is displaced along the longitudinal axis X toward the clutch disc 13 until a desired degree of contact force is present between the pressure plate 2 and the clutch disc 13. This contact force can generate friction between the clutch disc 13 and the pressure plate 2 for transmitting power. Thus, by rotating the pressure plate 2 relative to the clutch cover 3 about the longitudinal axis X, such a rolling movement of the rolling elements 6 on the ramps 5 can be achieved that the pressure plate 2 is displaced along the longitudinal axis X for clamping the clutch disc 13 which transmits the power.

[0067] Due to the partially radial alignment of the ramps 5, i.e., the pressure plate ramps 7 and the clutch cover ramps 8, the pressure plate 2 is radially supported by the rolling elements 6. More precisely, the pressure plate 2 is radially supported along the longitudinal axis X on the clutch cover 3. This compensates for the centrifugal forces acting on the rolling elements 6 and, because a separate radial bearing is not required, enables a weight-saving and cost-saving mounting of the pressure plate 2 on the clutch cover 3.

[0068] The axial springs 10 prevent the pressure plate ramps 7 and the clutch cover ramps 8 from lifting off the respective rolling elements 6 in the axial direction.

[0069] At the same time, the relative rotation stretches the tangential springs 11, so that after a shutdown or when a torque causing the relative rotation decreases, the pressure plate 2 is automatically rotated back in a direction that unclamps the clutch disc 13. Thus, safety requirements for a normally open friction clutch 1 are met.

[0070] Referring to the Fig. 3 and Fig. 6, a drive for the relative rotation of the friction clutch 1 is described below.

[0071] The friction clutch 1 is driven by an actuator 14 for relative rotation, i.e., for actuating the friction clutch 1. The actuator is an electric motor. The actuator 14 has a stator 15.

[0072] The stator 15 is essentially constructed from several coils 16 and is hollow-cylindrical in shape. A rotor 17 is provided radially inside the stator 15. The rotor 17 is essentially constructed from permanent magnets 18 and is also hollow-cylindrical in shape. A rotor carrier 19 is attached radially inside to the rotor 17. The rotor carrier 19 is hollow-cylindrical in shape. A ball bearing 21 is provided axially at each end of the stator 15 and the rotor 17. The ball bearings 21 maintain an air gap between the stator 15 and the rotor 17. The stator 15 and the rotor 17 are concentric with each other and with the longitudinal axis X.

[0073] The ball bearings 21 guide the rotor carrier 19 radially and axially on a stator carrier 20. The stator carrier 20 is secured to the clutch cover 3 via rivets 37 in the manner of a flange. Therefore, the rotor carrier 19 is supported on the clutch cover 3 via the ball bearings 21, the stator carrier 20, and the rivets 37.

[0074] In the first embodiment, two slip rings 22 are mounted radially on the outside of the stator carrier 20. The slip rings 22 are electrically connected to the coils 16. Current can be supplied to the coils 16 via the slip rings 22 and brushes (not shown) that rub against the slip rings 22, so that the coils 16 generate a magnetic field that acts on the permanent magnets 18 to generate a torque.

[0075] In the present case, a planetary gear, designated as a whole by 23, is arranged between the rotor 17 and the pressure plate 2. The planetary gear 23 is merely a preferred example of a gear that operatively connects the rotor 17 to the pressure plate 2.

[0076] The planetary gear set 23 comprises a ring gear 24 mounted radially on the inside of the pressure plate 2. A ring gear toothing 25 is cut, for example, into the pressure plate 2. The rotor carrier 19 carries a sun gear 26 and supports a planet carrier 27. To enable rotation between the planet carrier 27 and the sun gear 26, a slight fit, such as a transition fit 28, exists between the planet carrier 27 and the sun gear 26. For example, the rotor carrier 19 is dimensioned H7 radially on the inside, and the planet carrier 27 is dimensioned j7 radially on the outside. The planet carrier 27 carries three planets 29. The planets 29 are mounted on the planet carrier 27 via plain bearings 30 so as to be rotatable about respective planetary axes parallel to the longitudinal axis X. To prevent the planets 29 from becoming lost, a press sleeve 31 is pressed into each planet carrier 27.

[0077] If the actuator 14 is energized via the slip rings 22, the actuator 14 generates a torque between the stator carrier 15, which is fixed to the clutch cover, and the rotor carrier 19. This torque acts from the rotor carrier 19 via the planetary gear 23 onto the pressure plate 2. This causes the pressure plate 2 to rotate relative to the clutch cover 3. As described above, this causes the pressure plate 2 to be actuated or disengaged in the axial direction. In the present case, a spur gearing is selected for a sun gear toothing 32, a planetary gear toothing 33, and the ring gear toothing 25. The spur gearing ensures that, for example, the ring gear toothing 25 can slide on the planetary gear toothing 33 in the axial direction.

[0078] According to a modification of the first embodiment not shown in the figure, the planet carrier 27 is not mounted on the rotor carrier 19, but the planet carrier 27 is connected in a rotationally fixed manner to the clutch cover 3 via rivets 37, for example in the manner of a flange.

[0079] According to a further modification of the first embodiment, not shown in the figure, the clutch cover 3 is the planet carrier 27. The planets 29 are mounted via the plain bearings 30 on the rivets 37 or on other bolts or projections of the clutch cover 3 designed and arranged as planetary axes (“planetary axis” in the sense of a physical component).

[0080] Otherwise, the modifications of the first embodiment correspond to the first embodiment.

[0081] A second embodiment of the invention is described below with reference to Fig.7 to 9. The same features or comparable features as in the first embodiment or the modifications of the first embodiment are provided with the same reference numerals and will not be described again.

[0082] In the second embodiment, no slip rings 22 are provided. In the second embodiment, an inductive transmitter 34 is arranged axially next to the stator 15. The inductive transmitter 34 has an inductive receiver 35 fixed to the stator and an inductive transmitter 36 fixed to the clutch housing. By means of the inductive transmitter 36, a voltage can be generated in the inductive receiver 35, which generates an electric current flowing through the coils 16. Thus, by means of the inductive transmitter 34, a relative rotation can be generated between the clutch cover 3 and the pressure plate 2, as otherwise described above.

[0083] Otherwise, the second embodiment corresponds to the first embodiment. List of reference symbols 1 friction clutch 2 pressure plate 3 clutch covers 4 Ramp equipment 5 Ramp 6 rolling elements 7 Pressure plate ramp 8 Clutch cover ramp 9 spring carriers 10 axial spring 11 Tangential spring 12 spring retaining hole 13 Clutch disc 14 Actuator or electric motor 15 Stator 16 coil 17 Rotor 18 permanent magnet 19 rotor carrier 20 stator carriers 21 ball bearings 22 Slip ring 23 planetary gears 24 ring gear 25 ring gear teeth 26 Sun gear 27 planet carriers 28 Transition fit 29 Planet 30 plain bearings 31 press sleeve 32 sun gear teeth 33 planetary gearing 34 inductive transformers 35 inductive receivers 36 inductive transmitters 37 rivet X Longitudinal axis Y radial direction Z circumferential direction

Claims

[1] Friction clutch (1) for a motor vehicle drive train, comprising a pressure plate (2) which is rotatable about a longitudinal axis (X), a clutch cover (3) and at least one ramp device (4) which has at least one ramp (5) fixed to the pressure plate (2) or the clutch cover (3) and a rolling element (6) which can roll on the ramp (5), wherein the pressure plate (2), the rolling element (6) and the clutch cover (3) are coordinated with one another in such a way that, by rotating the pressure plate (2) relative to the clutch cover (3) about the longitudinal axis (X), such a rolling movement of the rolling element (6) on the ramp (5) can be achieved that the pressure plate (2) can be displaced along the longitudinal axis (X) for clamping a clutch disc (13) in a power-transmitting manner, wherein the pressure plate (2) is radially supported by the rolling element (6), characterized bythat an actuator (14) is further provided, the actuator (14) being an electric motor having a stator (15) rotationally coupled to the clutch cover (3) and a rotor (17) rotationally coupled to the pressure plate (2). [2] Friction clutch (1) according to claim 1, characterized by that the at least one ramp device (4) has a ramp (7) fixed to the pressure plate (2) and a ramp (8) fixed to the clutch cover (3), wherein the ramps (5) are preferably designed to be opposite one another. [3] Friction clutch (1) according to one of claims 1 to 2, characterized by that the ramp (7) fixed to the pressure plate (2) is formed integrally with the pressure plate (2), and / or that the ramp (8) formed on the clutch cover (3) is formed integrally with the clutch cover (3). [4] Friction clutch (1) according to one of claims 1 to 3, characterized by that a plurality of ramp devices (4) are provided. [5] Friction clutch (1) according to one of claims 1 to 4, characterized by that at least one axial spring (10) is arranged between the pressure plate (2) and the clutch cover (3), which prestresses the ramp device (4) along the longitudinal axis (X). [6] Friction clutch (1) according to one of claims 1 to 5, characterized by that at least one tangential spring (11) is arranged between the pressure plate (2) and the clutch cover (3). [7] Friction clutch (1) according to claim 6, characterized by that the at least one tangential spring (11) prestresses the pressure plate (2) relative to the clutch cover (3) in a clutch disc-unclamping direction. [8] Friction clutch (1) according to one of claims 6 to 7, characterized by that the tangential spring (11) is mounted at least radially outwardly in / on an arcuate spring guide.

9. Friction clutch (1) according to one of the preceding claims, characterized bythat the rotor (17) is operatively connected to the pressure plate (2) directly or via a gear (23).

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