阅读说明：本技术 用于离合器致动的中央释放单元 (Central release unit for clutch actuation ) 是由 D.拜尔斯多弗 H-J.乔治 于 2019-06-28 设计创作，主要内容包括：一种中央释放单元(10)具有缸壳体(12),该缸壳体(12)围绕中心轴线(M)限定环形压力室(14),其中,环形活塞(18)在所述压力室中可移动地被引导。释放轴承(16)通过支撑环(20、20’)保持在环形活塞上,其中,所述支撑环的套筒部分(24)围绕环形活塞的端部(22)。套筒部分具有多个弹簧片(26),所述弹簧片以弹簧方式接合在环形活塞的指定凹陷(30)中,并且将支撑环的接触面(32)拉向环形活塞的端面(34)。在支撑环和环形活塞之间存在限定的径向游隙(s),允许支撑环的接触面在环形活塞的端面上的翻滚运动。为了弹簧片的接合,环形活塞的凹陷包括具有梯度(斜坡角α)的斜坡区域(36),使得在所述翻滚运动期间,弹簧片可以沿着中心轴线在斜坡区域上滑动而没有自抑制,且因此向支撑环施加回复力,抵抗翻滚运动。(A central relief unit (10) has a cylinder housing (12), which cylinder housing (12) defines an annular pressure chamber (14) around a central axis (M), wherein an annular piston (18) is movably guided in the pressure chamber. The release bearing (16) is held on the annular piston by a support ring (20, 20'), wherein a sleeve portion (24) of the support ring surrounds an end (22) of the annular piston. The sleeve part has a plurality of spring tabs (26) which engage in spring fashion in designated recesses (30) of the annular piston and pull the contact surface (32) of the support ring towards an end face (34) of the annular piston. There is a defined radial play(s) between the support ring and the annular piston, allowing a rolling movement of the contact surface of the support ring on the end face of the annular piston. For the engagement of the spring plate, the recess of the annular piston comprises a ramp region (36) with a gradient (ramp angle α) such that during said tumbling movement the spring plate can slide along the central axis on the ramp region without self-damping and thus apply a restoring force to the support ring, counteracting the tumbling movement.)

1. A central release unit (10) for clutch actuation has a cylinder housing (12), which cylinder housing (12) delimits an annular pressure chamber (14) around a central axis (M); wherein an annular piston (18) can be actively connected to the clutch by means of a release bearing (16), which annular piston (18) is movably guided in the pressure chamber (14) along a centre axis (M); wherein the release bearing (16) is connected to the annular piston (18) by a support ring (20, 20'), a sleeve portion (24, 24') of the support ring (20, 20') having a plurality of spring blades (26, 26'), the sleeve portion (24, 24') surrounding an end (22) of the annular piston (18); wherein a free end (28, 28') of each of said spring blades is configured to engage in a spring manner in a designated recess (30) in the end (22) of the annular piston (18) and said blades are adapted to abut a contact surface (32, 32') of the support ring (20, 20') against an end surface (34) on the end (22) of the annular piston (18); characterized in that the outer diameter (D) of the end portion (22) is smaller than the inner diameter (D) of the sleeve portion (24, 24'), so that there is a defined radial play(s) between the support ring (20, 20') and the annular piston (18), allowing a tumbling motion of the contact surface (32, 32') on the end face (34) of the annular piston (34) about the central axis (M); wherein, for spring engagement of the spring leaf (26, 26'), the recess (30) of the annular piston (18) comprises a ramp region (36) having a gradient relative to the central axis (M) such that during the tumbling motion, the spring leaf (26, 26') can slide along the central axis (M) on the ramp region (36) without self-damping and thus exert a restoring force on the support ring (20, 20') against the tumbling motion.

2. The central release unit (10) according to claim 1, characterized in that the gradient of the ramp region (36) on the annular piston (18) is constant with a ramp angle (a) relative to the central axis (M).

3. The central release unit (10) according to claim 2, characterized in that the gradient of the ramp region (36) satisfies the following formula:

tanα>μ_R

wherein, mu_RIs the coefficient of friction between the spring blades (26, 26') of the support rings (20, 20') and the ramp region (36) of the annular piston (18).

4. The central release unit (10) according to claim 2 or 3, characterized in that the ramp angle (a) of the ramp region (36) on the annular piston (18) relative to the central axis (M) is greater than or equal to 10 ° and less than or equal to 15 °.

5. The central release unit (10) according to any one of the preceding claims, characterized in that the radial play(s) between the support ring (20, 20') and the annular piston (18) and the axial length (L) of the sleeve portion (24, 24') of the support ring (20, 20') are matched to one another such that during the tumbling movement the support ring (20, 20') mounted on the annular piston (18) can be tilted with respect to the central axis (M) by a tilting angle (β) of at most 2 °.

6. The central release unit (10) according to any one of the preceding claims, characterized in that the support ring (20, 20') has at least three and at most nine leaf springs (26, 26').

7. The central release unit (10) according to claim 6, characterized in that the support ring (20, 20') has six spring blades (26, 26').

8. Central release unit (10) according to any of the preceding claims, wherein the spring tabs (26, 26') are evenly distributed on the periphery of the support rings (20, 20').

9. Central release unit (10) according to any of the preceding claims, wherein the end (22) of the annular piston (18) has a collar (104) protruding radially outwards, which collar (104) forms a stop for the spring tabs (26, 26') of the support rings (20, 20').

10. The central release unit (10) according to any one of the preceding claims, characterized in that the sleeve portions (24, 24') of the support rings (20, 20') are circular on the inner periphery at their ends facing the pressure chamber (14).

11. The central release unit (10) according to any one of the preceding claims, wherein the ramp region (36) is formed by a peripheral conical surface (92) of the annular piston (18).

12. The central release unit (10) according to any of the preceding claims, wherein the free ends (28) of the spring tabs (26) face away from the pressure chamber (14).

13. Central release unit (10) according to any of the claims 1 to 11, wherein the free end (28') of the spring plate (26') faces the pressure chamber (14).

14. The central release unit (10) according to any of the preceding claims, wherein the free ends (28, 28') of the spring tabs (26, 26') are bent away from the annular piston (18) over a bending region (94, 94'), and the bending region (94, 94') abuts against a ramp region (36) of the annular piston (18).

15. The central release unit (10) according to any one of the preceding claims, characterized in that the cylinder housing (12) and/or the annular piston (18) are made of plastic.

Technical Field

The present invention relates to a central release unit for clutch actuation according to the preamble of claim 1. In particular, the invention relates to a hydraulic clutch actuated central release unit for a friction clutch of a motor vehicle, as is used in large numbers in the automotive industry.

Background

Hydraulic clutch actuation for motor vehicles generally has a master cylinder which is connected to an expansion reservoir filled with hydraulic fluid and can be actuated, for example manually by means of a clutch pedal or automatically by means of an actuator unit. The master cylinder is hydraulically connected to the slave cylinder by a pressure line, so that the pressure generated by depressing the clutch pedal or the actuating movement of the actuator unit in the master cylinder can be transmitted to the slave cylinder by a fluid column in the pressure line. As a result, the release bearing on the friction clutch is acted upon with an actuating force by the slave cylinder to disengage the clutch pressure plate from the clutch driving plate via the release mechanism, thereby disengaging the engine from the transmission of the motor vehicle.

In order to guarantee the actuation of the friction clutch with the least possible space requirement for the slave cylinder as possible, it has long been known to form the slave cylinder as an annular cylinder which is arranged around the clutch or the transmission shaft and is preferably attached to the gearbox housing. An annular piston (also called sliding sleeve) is arranged in the annular cylinder so as to be movable in the axial direction of the clutch or the drive shaft and carries or is actively connected with a release bearing of the friction clutch. When the annular cylinder is hydraulically loaded via a pressure line, the annular piston acts via a release bearing on a clutch spring device (usually comprising a diaphragm or cup spring) of the friction clutch in order to release it. Such slave cylinders are also referred to as central release units because they have a concentric arrangement with respect to the clutch or the drive shaft.

Modern central release units have a cylinder housing which is mainly made of plastic or light metal alloy for cost and weight reasons and have at least one outer cylinder wall which delimits an annular pressure chamber radially outwards; the chamber may be pressurized by a pressure port and house a movable annular piston that is actively connected to the clutch by a release bearing. In some cases, the integrally designed cylinder housing made of plastic also has an inner cylinder wall which delimits the pressure chamber radially inwards and guides the annular piston; in other cases, a guide sleeve, usually deep drawn from steel plate, is concentrically arranged within the outer cylinder wall and attached to the cylinder housing in order to delimit the pressure chamber radially inwards and guide the annular piston.

In previously known designs for central release units (see for example publication EP1464862a2), the release bearing is rigidly coupled by a sheet metal support ring to an annular piston which is guided on a guide surface formed by an inner cylinder wall or a guide sleeve. In the assembled state of the central release unit, the release bearing is supported on the diaphragm or cup spring of the clutch under spring preload. In operation, the release bearing may be loaded with an axial run-out that attempts to force the release bearing into a tumbling motion, for example due to production related clearances of the clutch spring or an eccentric arrangement relative to the clutch spring. Since the rigid connection of the bearing to the annular piston is released, the latter is loaded with a tilting moment circulating at the rotational speed on the clutch, which must be borne by the guide surfaces on the inner cylinder wall or guide sleeve. The radially inner edge of the annular piston facing the clutch can thus be pressed so strongly against the guide surface that the edge of the annular piston cuts into this region of the guide surface, i.e. wear occurs here on the guide surface, which is visible in the form of a peripheral contact track. Such wear should be avoided.

In this case, the publication DE19912432a1 discloses a release bearing for a clutch, with a bearing ring which is arranged rotatably fixed on a sliding sleeve, a bearing ring which rotates relative to it and bears against a cup spring of the clutch, and rolling bodies which are arranged between the bearing rings, wherein the rotating bearing ring has two regions which have complementary spherical segments which can slide over one another and pivot relative to one another. By dividing the rotary bearing ring in two in this way, the previously known release bearing is able to compensate for the axial parallel offset of the force transmission shaft and the play of the cup-shaped spring tongues, so that such forces are not transmitted to the sliding-sleeve-side bearing ring.

In addition to the relatively complex structure of the previously known release bearing, this prior art has the disadvantage that the individual parts of the rotary bearing ring in the axial force transmission region, when in contact with one another, undergo a sliding movement relative to one another, which means that a relatively high wear is to be expected at this time.

The same applies to the concept for self-adjusting clutch release bearings known from the publications DE10114844a1 and DE102013203016a1, in which the dome-shaped contact surface between the inner ring and the supporting ring or the circular or spherical contour between the supporting ring and the annular piston in the release bearing can slide over one another in the axial force transmission region.

Publication DE102009018794a1, which forms the preamble of claim 1, finally discloses a central release unit for clutch actuation, in which a release bearing is connected to a sliding sleeve by means of a bearing connection around one end of the sliding sleeve. The bearing connection has at least one spring tab which engages in a recess formed on the sliding sleeve and serves to connect the bearing connection to the sliding sleeve without play. In particular, this ensures a play-free final mounting position in the axial direction between the sliding sleeve and the bearing connection, which also compensates for manufacturing tolerances and ensures that the annular region receiving the bearing connection releasing the bearing is always firmly supported on the end face of the sliding sleeve. This reduces, but does not completely avoid, wear between the bearing connection and the sliding sleeve, which in the prior art results from permanent relative movement between the bearing connection and the sliding sleeve.

In the prior art, the bearing connection comprises an annular region with a U-shaped cross section, which is open towards the radial outside, and in which the inner ring of the release bearing is held by a spring (radial displacement force spring) to ensure contact of the inner ring with the bearing connection, allowing movement in the radial direction. Thus, since the bearing connection is a play-free connection with the sliding sleeve, any rolling movement of the release bearing is transmitted to the sliding sleeve, and there is therefore also the problem outlined initially here, in which the edge of the sliding sleeve can cut into the guide surface of the sliding sleeve.

Disclosure of Invention

The object of the present invention is to provide a central release unit for clutch actuation which is as simple as possible, avoids the above-mentioned disadvantages and is optimized with respect to the outlined prior art, in particular in connection with operation with minimal wear.

This object is achieved by a central release unit for clutch actuation having the features of claim 1. Advantageous embodiments of the invention are the subject matter of the dependent claims.

A central release unit for clutch actuation includes a cylinder housing defining an annular pressure chamber about a central axis; wherein an annular piston, which is movably guided in the pressure chamber along a central axis, can be actively connected to the clutch by means of a release bearing;

wherein the release bearing is connected to the annular piston by a support ring, a sleeve portion of the support ring having a plurality of spring tabs, the sleeve portion surrounding an end of the annular piston; wherein the free end of each spring plate is configured to engage in a spring manner in a designated recess in the end of the annular piston, and the plate is adapted to abut the contact face of the support ring against an end face on the end of the annular piston; wherein, according to the invention, the outer diameter of the end portion is smaller than the inner diameter of the sleeve portion, so that there is a defined radial play between the support ring and the annular piston, allowing a rolling movement of the contact surface of the support ring on the end face of the annular piston around the central axis; wherein for spring engagement of the spring leaf, the recess of the annular piston comprises a ramp region having a gradient relative to the central axis, such that during the tumbling motion the spring leaf may slide along the central axis on the ramp region without self-damping and thus exert a restoring force on the support ring, resisting the tumbling motion.

The spring leaf has a specific preload against the ramp region of the annular piston with a defined gradient, always producing a resultant force on the support ring with an axial force component oriented parallel to the central axis. This force component is intended to pull the contact surface of the support ring towards the end surface of the annular piston. Without external force by releasing the bearing, cooperating with the ramp region, the gradient of which prevents self-damping in the region of contact with the spring plate, allowing the spring plate to slide on the ramp region in some cases, the spring plate achieves surface contact between the contact surface of the support ring and the end face of the annular piston. Since the axial contact between the annular piston and the support ring can thus be achieved in the rest position and in operation, i.e. without axial play in the connection, idle strokes are advantageously avoided during actuation of the clutch by the central release unit, i.e. during the actual release and engagement.

However, it is clearly undesirable to have no play at all in the connection between the annular piston and the support ring. In contrast, according to the invention, a defined radial play is provided between the support ring and the annular piston, which allows the support ring to tilt relative to the annular piston. This inclinability of the support ring relative to the central axis, in combination with a restoring force on the support ring, which acts along the central axis and is generated by the elastic engagement of the spring plate on the ramp region of the annular piston, results in the release bearing, which is held on the annular piston by the support ring, being able to perform a relatively free tumbling movement relative to the annular piston. If a tumbling movement is applied to the release bearing in operation of the central release unit, as initially described, the support ring follows this tumbling movement relative to the annular piston, which results in a permanent relative movement between the support ring and the annular piston, in contrast to the common prior art.

The release bearing, which is held in a specific manner on the annular piston by means of the support ring, can thus roll relatively freely relative to the annular piston without transmitting a cyclic tilting moment to the annular piston. Wear between the annular piston and its guide surface in the cylinder housing, which was originally described in the prior art as a peripheral contact rail and which was visible, is therefore reliably avoided.

Due to the connection of the support ring according to the invention with the annular piston, no excessive wear occurs between the support ring and the annular piston, although a permanent relative movement is permitted here. This is because no axial forces are transmitted in the sliding contact region between the spring plate of the support ring and the ramp region of the annular piston. The axial force transmission between the support ring and the annular piston occurs conversely in the contact area between the contact surface of the support ring and the end face of the annular piston. During the tumbling movement of the support ring with the release bearing, this contact area between the support ring and the annular piston however circulates substantially only between the faces, i.e. the contact faces of the support ring tumble over the end faces of the annular piston, without wear-related sliding relative movements occurring between the faces in this circulating contact area.

In other words, the basic concept of the invention is to realize the connection of the release bearing to the annular piston by means of the support ring such that the tumbling movement of the release bearing can be allowed with as little hindrance as possible and, however, the sliding relative movement that necessarily occurs between the support ring and the annular piston occurs in an area where no axial force is transmitted. This separation of the axial force transmission positions and the sliding relative movement between the support ring and the annular piston greatly reduces wear.

In principle, the ramp region on the annular piston may have a gradient that varies along the central axis, as long as it is ensured that the spring plate can slide on the ramp region without self-damping during a possible tumbling movement, and that a force is generated due to the elastic contact of the spring plate on the ramp region, which force is intended to pull the support ring towards the annular piston. The changing gradient in the ramp region can, for example, exert an influence on the restoring force, so that a greater deflection of the support ring relative to the annular piston results in a preferentially even greater restoring force. In particular in view of the clearly defined and substantially linear rise of the restoring force upon deflection of the support ring relative to the annular piston, a preferred embodiment is one in which the gradient of the ramp region over the annular piston is fixed, with a fixed ramp angle α relative to the central axis.

In order to reliably ensure here an automatic sliding movement of the spring plate of the support ring in the direction of the pressure chamber on the ramp region of the annular piston without further measures, the embodiment is suitably designed such that the gradient α of the ramp region satisfies the following formula:

tanα>μ_R

wherein, mu_RIs the coefficient of friction between the spring plate of the support ring and the ramp region of the annular piston.

In experiments carried out by the inventors, it has proved to be particularly suitable for the ramp region to have a ramp angle α on the annular piston which is greater than or equal to 10 ° and less than or equal to 15 ° relative to the central axis. However, flatter or steeper ramp angles are also conceivable, depending on the respective material pairing and/or lubrication conditions. Furthermore, a spring rate of between 75 and 90N/mm per leaf spring has proven to be feasible. In a practical embodiment, the preload stroke of the respective spring plate on the ramp region can be, for example, 0.5mm when the support ring is in its centered "rest position" relative to the central axis, i.e. its contact surface bears on the surface on the end face of the annular piston. In one configuration of the support ring made of spring steel, each leaf spring has a wall thickness of 0.5mm and a rod length of about 4 to 5mm, which corresponds for example to the maximum force of each leaf spring 45N.

With regard to the further dimensioning of the relevant components required for the interaction of the support ring and the annular piston according to the invention, it can be provided that the radial play between the support ring and the annular piston and the axial length of the sleeve portion of the support ring around the end of the annular piston are matched to one another such that during the tumbling movement the support ring mounted on the annular piston can be inclined with respect to the central axis by an inclination angle β of at most 2 °. Experiments conducted by the inventors have shown here that with such dimensions, the tumbling motion exerted on the release bearing-either due to a clearance caused by the production of the clutch spring or an eccentric arrangement with respect to the clutch spring-does not allow the end of the support ring facing the pressure chamber to be supported on the annular piston in the radial direction. Any wear or abrasion on the annular piston associated with such contact is advantageously avoided. Furthermore, in a simple manner, this ensures that during the tumbling movement of the release bearing, the contact surfaces of the support ring remain in the above-described cyclic axial contact with the end face of the annular piston and cannot lift off from the end face of the annular piston, due to the radial "leverage" of the support ring.

The number of spring blades on the support ring depends in particular on the restoring force to be applied in order to automatically pull the contact surface of the support ring against the end face on the end of the annular piston in the stationary system. For relatively large sizes of the central release unit, this number may be significantly higher than ten. For common motor vehicle applications it is considered suitable if the support ring has at least three and at most nine leaf springs. The provision of at least three spring blades is advantageous, in particular with regard to the inherently stable connection of the support ring to the annular piston. For example, in the case of nine leaf springs, the production complexity of manufacturing the support ring is relatively high; moreover, each leaf spring is not absolutely necessary for function, and can also lead to undesirable weakening of the support ring structure. In a particularly preferred embodiment, the support ring therefore has six spring blades.

Furthermore, in particular with regard to the self-centering orientation of the support ring on the annular piston, it is advantageous in a preferred embodiment of the central release unit for the spring tabs to be distributed uniformly over the circumference of the support ring. Here, the individual spring blades may be angularly spaced evenly from each other, for example, about the central axis. However, it is also conceivable that several groups of spring blades, which are closely adjacent to one another on the circumference of the support ring, are evenly distributed over the circumference of the support ring, wherein these groups have a greater angular distance between them.

In order to provide additional protection against loss of the release bearing, in particular during transport and/or installation of the central release unit in the final installation position, in a preferred embodiment of the central release unit, furthermore, the end of the annular piston may have a radially outwardly projecting collar which forms a stop for the spring leaf of the support ring. However, instead of this optional collar, at the end of the annular piston, a peripheral groove may also be provided, which can catch a spring leaf of the support ring when the release bearing is withdrawn, or a locking ring, such as a circlip, a retaining ring or the like, which is held in the peripheral groove on the end of the annular piston and projects beyond this in the radial direction in order to form a stop surface for the spring leaf.

Furthermore, it is preferred that the sleeve portion of the support ring is circular on the inner periphery at its end facing the pressure chamber. This optional measure also serves to minimize wear or avoid damage to the annular piston, in particular during transport or installation of the central release unit in the final installation position, since the sharp edge of the support ring cannot bear on the annular piston even at the maximum inclination of the release bearing relative to the annular piston.

There are also several possibilities for forming a ramp area on the annular piston to engage the spring plate of the support ring. Thus, the ramp region may comprise a plurality of ramp portions in a corresponding number of recessed portions in the annular piston, each recessed portion being assigned a spring plate. It is also conceivable to provide the end of the annular piston with a peripheral recess having a plurality of flat individual faces which are arranged at a ramp angle relative to the central axis for engaging the spring plate and together form a ramp region of the annular piston, having, for example, a polygonal shape, seen in cross section. In particular to simplify production to the maximum and to avoid additional forces in operation, a preferred embodiment is however one in which the ramp region is formed by a peripheral conical surface of the annular piston. With such an embodiment of the ramp region, advantageously neither mounting means are required which prevent the individual components from twisting relative to one another, nor are they required to be mounted in a particular direction or oriented by a rotational angle.

In principle, there are two alternatives for the orientation of the spring blades of the support ring which extend substantially along the central axis: in a first alternative, the free end of the spring plate faces away from the pressure chamber, or in a second alternative, the free end of the spring plate faces towards the pressure chamber. A particular advantage of the first alternative is that a support ring constructed in this way is easier to mount on the annular piston, since the spring blades form an almost stepless axial connection chamfer during mounting. The second alternative is advantageous, however, because the support rings constructed in this way can be produced more easily, because their connection to the rest of the support ring is located in the region close to the contact face of the support ring during production or bending of the spring plate, wherein the support ring is more stable or rigid.

As regards the free ends of the spring blades of the support ring, they may, for example, be straight and have a chamfered surface at their end to come into contact with the ramp region of the annular piston. In contrast, in particular in order to keep the contact surface as small as possible and to achieve maximum mobility between the spring plate of the support ring and the ramp region of the annular piston and low wear on the ramp region, a preferred configuration is, however, one in which the free end of the spring plate is bent away from the annular piston on a bending region and the bending region bears against the ramp region of the annular piston.

In principle, the last cylinder housing and/or the annular piston can be made of a light metal alloy. In particular, in view of the low weight and the cheapest possible mass production, in particular avoiding material removal, it is however preferred that the cylinder housing and/or the annular piston are made of plastic, so that advantageously it can be produced by injection molding. Such an embodiment made of plastic is particularly advantageous for minimizing wear according to the invention.

Drawings

The invention will now be explained in more detail with reference to preferred exemplary embodiments and with reference to the accompanying partial schematic drawings. The figures show:

fig. 1 is a plan view of a central relief unit in a non-assembled state, which is cut away in a pressure port connection area provided on a cylinder housing of the central relief unit, according to a first exemplary embodiment of the present invention;

FIG. 2 is a cross-sectional view of the central release unit of FIG. 1, taken along section line II-II in FIG. 1;

fig. 3 is a sectional view, cut away along the section line II-II in fig. 1, at the top and bottom of the central release unit according to fig. 1 and enlarged in comparison with fig. 2, in particular for explaining how, for tumbling, the release bearing of the central release unit is attached by means of a support ring on an annular piston accommodated in a cylinder housing so as to be movable along a central axis;

FIG. 4 is an illustration of detail IV in FIG. 2 further enlarged compared to FIG. 3 to show further details of the tumble connection of the release bearing to the annular piston of the central release unit of FIG. 1, with the support ring having a spring tab thereon that is spring-loaded on a designated ramp area of the annular piston;

FIG. 5 is a cut-away cross-sectional view, corresponding to the scale, illustration and section lines of FIG. 3, of the central release unit of FIG. 1 in an assembled but unactuated state, shown in phantom and cut away, on the left side of FIG. 5 being the spring tongue of a diaphragm spring to be actuated by the central release unit on a friction coupling, and on the right side of FIG. 5 being a fixing flange on a gearbox housing to illustrate the installation of the central release unit;

FIG. 6 is a cross-sectional view of the central release unit of FIG. 1, which is not cut away and corresponds to the scale, illustration and section lines of FIG. 5 to illustrate how the release bearing may tumble relative to the annular piston due to the tumble connection of the release bearing through the support ring;

fig. 7 is an illustration of detail VII of fig. 6, enlarged again compared to fig. 6, showing that in the central release unit of fig. 1, the support ring may be in cyclic contact with the annular piston during the tumbling movement of the release bearing and at the maximum inclination of the release bearing relative to the central axis;

fig. 8 is an illustration of the detail VIII of fig. 6, which is enlarged again compared with fig. 6, which shows, compared with fig. 7, that in the central release unit of fig. 1 the support ring can be lifted off the annular piston circumferentially during the tumbling movement of the release bearing and at the maximum inclination of the release bearing relative to the central axis;

fig. 9 is a perspective view of only the support ring of the central releasing unit of fig. 1 from obliquely above/rear left;

fig. 10 is a perspective view of only the support ring of the central release unit of fig. 1 from obliquely above/front left;

FIG. 11 is a longitudinal cross-sectional view of only the support ring of the central release unit of FIG. 1 enlarged compared to FIGS. 9 and 10;

fig. 12 is a perspective view from obliquely above/left rear of only the annular piston of the central release unit of fig. 1 without the sealing sleeve;

FIG. 13 is a perspective view of only the annular piston of the central release unit of FIG. 1 from obliquely above/front left without the sealing sleeve;

FIG. 14 is a side view of only the annular piston of the central release unit of FIG. 1 enlarged as compared to FIGS. 12 and 13 without the sealing sleeve;

FIG. 15 is a longitudinal cross-sectional view of only the annular piston of the central release unit of FIG. 1 to the scale of FIG. 14, without the sealing sleeve;

fig. 16 is a plan view of the central relief unit according to the second exemplary embodiment of the present invention in a non-assembled state, which is again cut away in the pressure port connection area provided on the cylinder housing of the central relief unit;

FIG. 17 is a cross-sectional view of the central release unit of FIG. 16 taken along section lines XVII-XVII in FIG. 16;

FIG. 18 is a cross-sectional view of the central discharge unit of FIG. 16, enlarged as compared to FIG. 17 and cut away at the top and bottom, taken along section lines XVII-XVII in FIG. 16, particularly for explaining how the discharge bearings of the central discharge unit are arranged on an annular piston movably received in the cylinder housing by means of a differently configured support ring for tumble;

FIG. 19 is an illustration of detail XIX of FIG. 17, again enlarged compared to FIG. 18, to show further details of the tumble-solid connection of the release bearing to the annular piston of the central release unit of FIG. 16, wherein the spring tabs on the support ring are oriented differently and spring-loaded on designated ramp regions of the annular piston;

FIG. 20 is a cut-away cross-sectional view of the central release unit of FIG. 16 in an assembled but unactuated state corresponding to the scale, illustration and section lines of FIG. 18, with the spring tongue of the diaphragm spring of the friction clutch and the fixed flange of the gearbox housing again indicated in phantom and cut away, corresponding to FIGS. 5 and 6 showing the first exemplary embodiment;

fig. 21 is a perspective view of only the support ring of the central releasing unit of fig. 16 from obliquely above/rear left;

fig. 22 is a perspective view of only the support ring of the central release unit of fig. 16 from obliquely above/front left; and

fig. 23 is a longitudinal sectional view of only the support ring of the central release unit of fig. 16 enlarged compared to fig. 21 and 22.

In the figures, for the sake of simplicity of description, the elastic or elastomeric parts, i.e. the leaf spring of the support ring and the sealing sleeve on the annular piston, are shown in a non-deformed state; in practice, these deformable members bear on the abutment surfaces of adjacent members.

Detailed Description

In fig. 1 to 8, reference numeral 10 generally designates a central release unit for hydraulic clutch actuation. The central relief unit 10 has a cylinder housing 12, the cylinder housing 12 defining an annular pressure chamber 14 about a central axis M. An annular piston 18, which can be actively connected to the friction clutch via a release bearing 16, is guided in the pressure chamber 14 so as to be movable along the central axis M. The release bearing 16 is connected to the annular piston 18 by means of a support ring 20, a sleeve portion 24 of the support ring 20 surrounding the end 22 of the annular piston 18. The sleeve portion 24 of the support ring 20 has a plurality of spring tabs 26, as shown in particular in fig. 4, 7 and 8, the free end 28 of each spring tab 26 being spring-engaged in a designated recess 30 in the end 22 of the annular piston 18. The spring tabs 26 are adapted to urge the contact surfaces 32 of the support ring 20 against end surfaces 34 on the end 22 of the annular piston 18.

As will be described in more detail below, the support ring 20 forms a tumble connection of the release bearing 16 with the annular piston 18 of the central release unit 10. In particular according to fig. 4, the outer diameter D of the end portion 22 of the annular piston 18 is smaller than the inner diameter D of the sleeve portion 24 of the support ring 20, so that there is a defined radial play s between the support ring 20 and the annular piston 18. This radial play s allows a tumbling movement of the contact surface 32 of the support ring 20 about the central axis M on the end face 34 of the annular piston 18. The recess 30 of the annular piston 18 also comprises a ramp region 36 for spring engagement of the spring strips 26 of the support ring 20, which region has a gradient with respect to the central axis M, so that during said tumbling movement the spring strips 26 can slide along the central axis M on the ramp region 36 without self-damping, thus applying a restoring force to the support ring 20, counteracting the tumbling movement.

In the exemplary embodiment shown, the central release unit 10 has a cylinder housing 12, which is injection molded from a suitable plastic, such as, for example, glass fiber filled polyphthalamide (PPA), having two concentrically arranged cylinder walls, an inner cylinder wall 38 and an outer cylinder wall 40, which radially define an annular pressure chamber 14. The annular piston 18, which is axially movably accommodated in the pressure chamber 14 and which in the exemplary embodiment shown is also made of a suitable plastic, such as polyphthalamide (PPA) having a predetermined glass fibre content, for example 50%, is optionally loaded with a pressure medium via a pressure port connection 42 (fig. 1) of the cylinder housing 12 in order to actuate the friction clutch by axial displacement of the annular piston 18, for which purpose the pressure port connection 42 is connected to the pressure chamber 14 via a channel 44 molded into the cylinder housing 12 (not shown in detail in the figures), so that pressure medium, i.e. hydraulic fluid, can be supplied to the pressure chamber 14 via the channel 44.

The cylinder walls 38 and 40, which are arranged concentrically with respect to the center axis M and with each other, are connected together at their ends shown on the right side of fig. 2, 3, 5 and 6 via a flange portion 46. The outer periphery of the flange portion 46 is provided with fixing holes 48 which are angularly spaced apart and reinforced with metal in the exemplary embodiment shown and which in the motor vehicle serve in a known manner for fixing the central release unit 10 to the gearbox wall (indicated by dashed lines 50 in fig. 5 and 6) or to the gearbox cover by means of, for example, bolts (not shown) which pass through the fixing holes 48 and pull the central release unit 10 with the end side 52 of the cylinder housing 12 towards the gearbox wall 50 or the gearbox cover. In the exemplary embodiment shown, the cylinder housing 12 is integrally injection molded from plastic with the pressure port connection 42 adjoining the flange portion 46, its cylinder walls 38 and 40, and the flange portion 46 connecting them and containing the securing hole 48.

Outer cylinder wall 40 is surrounded by a preload spring 54, preload spring 54 being a cylindrical coil compression spring in the exemplary embodiment shown. At the right end of fig. 2, 3, 5 and 6, a preload spring 54 is seated in an axial groove 56 formed in the flange portion 46 of the cylinder housing 12. At the left end of fig. 2, 3, 5 and 6, the preload spring 54 exerts a defined preload force on the release bearing 16 through an annular spring plate 58. As mentioned above, the release bearing 16 is held on the end 22 of the annular piston 18 (which faces away from the pressure chamber 14 and is shown on the left in fig. 2, 3, 5 and 6) by means of a support ring 20, so that upon pressurisation of the annular pressure chamber 14, the release bearing 16 can be moved in the axial direction, i.e. horizontally in the above-mentioned figures, in order to release or engage the friction clutch in a known manner.

At the right end of the annular piston 18 shown in fig. 2, 3, 5 and 6, which annular piston 18 in the basic position of the central release unit 10 shown in fig. 2 and 3 still overlaps in the axial direction with the outer cylinder wall 40 of the cylinder housing 12, a dynamic seal in the form of an elastomer sealing sleeve 60 is suitably arranged, here in engagement with a sealing sleeve foot 62 in an axial groove 64, with a circumferential undercut on the end face of the annular piston 18. A sealing seat 60 (shown in an undeformed state for simplicity of illustration) bears tightly against the inner cylinder wall 38 of the cylinder housing 12 and the outer cylinder wall 40 of the cylinder housing 12 in order to seal the pressure chamber 14 to the left in fig. 2, 3, 5 and 6.

The outer periphery of the outer cylinder wall 14 is provided with a metal reinforcement sleeve 66 which is attached to the outer cylinder wall 40 by a snap lock connection 68 provided at the end of the reinforcement sleeve 66 facing away from the pressure port connection 42. The reinforcing sleeve 66 is arranged in the region of the outer cylinder wall 40 which has a relatively thin wall thickness and has to be supported against the pressure in the pressure chamber 14 in order to avoid detrimental structural changes of the plastic.

The release bearing 16, which is arranged on the side of the annular piston 18 facing away from the pressure chamber 14, comprises, in a known manner, an inner ring 70, an outer ring 72 and a plurality of roller bodies 74, which are held in a cage 76 between the inner ring 70 and the outer ring 72 and are protected by a sealing disk 78. The inner ring 70 of the release bearing 16 is attached to the support ring 20 by an annular fixing portion 80 of the inner ring 70 extending transversely to the central axis M.

To this end, in particular according to fig. 3, 5 and 6, the support ring 20 has, viewed in cross section, a substantially U-shaped ring portion 82 which is open radially outwards and by means of which a shoulder 84 extending transversely to the central axis M is connected to the larger-diameter sleeve portion 24 of the support ring 20. A shoulder 84 of the support ring 20, the side of which faces the annular piston 18, forms the contact surface 32 for the end face 34 of the annular piston 18.

On the opposite side, in particular according to fig. 4, 7 and 8, the shoulder 84 of the support ring 20 defines a further contact surface 84 for the fixing portion 80 of the inner ring 70. Furthermore, cup springs 84 (or angular spring elements) are accommodated on the ring portion 82 of the support ring 20 and placed in the corner regions of the U-shaped cross section, pressing the fixing portions 80 of the inner ring 70 against the contact faces 86 of the shoulder 84 of the support ring 20, so that the inner ring 70 of the release bearing 16 is fixedly held on the support ring 20 in the axial direction.

Fig. 3 to 8 also clearly show that at the inner ring 70 of the release bearing 16 the inner diameter of the fixing portion 80 is larger than the outer diameter of the ring portion 82 of the support ring 20, so that there is a certain radial play between the release bearing 16 and the support ring 20 to allow radial movement of the release bearing 16 relative to the support ring 20. This serves to compensate for any axial offset between the central release unit 10 attached to the gearbox wall 50 and the diaphragm spring of the friction clutch to be actuated by the central release unit 10, wherein fig. 5 and 6 show the spring tongue with reference numeral 90 in dashed lines and have its spring tongue 90 on the outer ring 72 of the release bearing 16 in the assembled state of the central release unit 10.

Further details of the sleeve portion 24 of the support ring 20 are shown in particular in fig. 9 to 11. In the exemplary embodiment shown, the support ring 20 therefore has a total of six spring tabs 26 in the middle in the region of the sleeve part 24 in the axial direction. The spring tabs 26 are evenly distributed on the periphery of the support ring 20 and are created or bent radially inward from the base material of the support ring 20.

In the exemplary embodiment, the free ends 28 of the spring tabs 26 extending along the central axis M face away from the pressure chamber 14, i.e. in the direction of the shoulder 84 of the support ring 20, when the support ring 20 is mounted on the annular piston 18. The free ends 28 of the spring strips 26 are further bent radially inward so that, when the support ring 20 is mounted on the annular piston 18, they are spring-loaded in the recesses 30 of the annular piston 18 on the ramp region 36, which in the exemplary embodiment shown are formed by a peripheral conical surface 92 of the annular piston 18. More precisely, at their free ends 28, the spring tabs 26 are bent away from the annular piston 18 by the annular piston 18, and wherein the bending regions 94 are slidably supported on the ramp regions 36 of the annular piston 18.

As best shown in fig. 4, 7, 8 and 11, the sleeve portion 24 of the support ring 20 is provided with a circumferential circular area, reference numeral 96, on its inner periphery at its end facing the pressure chamber 14 in the mounted state of the release bearing 16. Thus, even at maximum inclination of the support ring 20 relative to the annular piston 18, the sharp terminating edge of the sleeve portion 24 cannot come into contact with the annular piston 18, as shown in fig. 7.

Further details of the annular piston 18 are shown in particular in fig. 12 to 15. The inner periphery of the annular piston 18 (made by injection molding in the exemplary embodiment shown) is initially provided with a grease pocket 98 extending along the central axis M. Adjacent the end face 34 to be in contact with the support ring 20, the inner periphery of the annular piston 18 also has a shoulder 100, which shoulder 100 forms an annular contact face when the annular piston 18 is mounted on the inner cylinder wall 38 of the cylinder housing 12 as shown in fig. 2 to 4, with which annular contact face the annular piston 18 can follow against a locking ring 102, which locking ring 102 is suitably arranged, for example welded, as a mounting safety means on the free end of the inner cylinder wall 38, and projects in the radial direction on the outer peripheral face of the inner cylinder wall 38.

As shown in particular in fig. 4, 7 and 8, at its end 22 adjacent to the end face 34, the outer periphery of the annular piston 18 initially has a radially outwardly projecting collar 104 provided with a connecting chamfer 106 for supporting the ring 20. The collar 104 serves as an additional safety device against loss of the release bearing 16 and forms a stop for the spring tabs 26 supporting the ring 20. The outer diameter of the collar 104 here is slightly smaller than the inner diameter of the sleeve portion 24 of the support ring 20, so that the tumbling movement of the support ring 20 over the end 22 of the annular piston 18 is not impeded by the collar 104.

After the short cylindrical transition region of the annular piston 18 on the right in fig. 2 to 8, the collar 104 adjoins the recess 30 in the outer circumferential surface of the annular piston 18. The recess 30, viewed from left to right in the figures, begins with the ramp region 36 or the conical surface 92 and ends after the ramp region 36 with a slightly curved run-out region 108, on which the spring plate 26 cannot bear. The run-out region 108 of the recess 30 is adjacent to an interrupted cylindrical surface 110 of diameter D, in particular according to fig. 12 to 14, which interrupted cylindrical surface 110 is formed by a longitudinal rib 109 of the annular piston 18. Thereafter, the wall thickness of the annular piston 18 is increased in the end region 112 so that the annular piston 18 can be tightly received in the pressure chamber 14 and sufficient material is provided to stably form the axial groove 64 to receive the sealing sleeve 60.

As particularly shown in fig. 4, in the exemplary embodiment shown here, the gradient of the ramp region 36 or the conical surface 92 of the annular piston 18 is constant, with a ramp angle α with respect to the central axis M. The gradient is selected such that in the spring plate 26 and the ramp region36, so that the tangent of the ramp angle alpha is greater than the coefficient of friction mu between the spring plate 26 and the ramp region 36_R. Preferably, the ramp angle α is between 10 ° and 50 ° with respect to the central axis M, and in the example shown, is about 12 ° with respect to the central axis M.

As further shown in fig. 4 and 6 to 8, the radial play s between the support ring 20 and the annular piston 18 and the axial length L of the sleeve portion 24 of the support ring 20 are matched to one another such that during the tumbling movement the support ring 20 mounted on the annular piston 18 can be inclined with respect to the central axis M by an inclination angle β of at most 2 ° (see fig. 6). The backup ring 20 cannot be tilted further with respect to the central axis M because the circular portion 96 of the sleeve portion 24 of the backup ring 20 bears on the interrupted cylindrical surface 110 of the annular piston 18, as shown in the upper right of fig. 7. However, the roll angle of the release bearing 16 relative to the central axis M is typically small, so that during operation of the central release unit 10, such contact typically does not occur between the circular portion 96 of the sleeve portion 24 and the annular piston 18.

Fig. 7 and 8 also clearly show that during the tumbling movement exerted on the support ring 20 by the release bearing 16, only a small area 114 of the contact face 32 of the support ring 20 rests on the end face 34 of the annular piston 18 (see fig. 7), while a major part of the contact face 32 of the support ring 20 is lifted off the end face 34 of the annular piston 18 (see fig. 8). This contact area 114 between the contact face 32 of the support ring 20 and the end face 34 of the annular piston 18 circulates around the central axis M on the end face 34 of the annular piston 18 during the joint tumbling movement of the release bearing 16 and the support ring 20. In this cyclical contact region 114, axial force transmission occurs between the annular piston 18 and the support ring 20/release bearing 16 without any substantial sliding movement between the contact face 32 of the support ring 20 and the end face 34 of the annular piston 18. The restoring force of the spring plate 26, which has the purpose of pulling the support ring 20 towards the annular piston 18 and thus resisting the tumbling movement with a certain (albeit slight) resistance, also serves here to center the support ring 20 relative to the annular piston 18.

The second exemplary embodiment shown in fig. 16 to 23 differs from the first exemplary embodiment described above with reference to fig. 1 to 15 only in the design of the support ring 20'; accordingly, corresponding reference numerals for the support ring and its components have been suffixed with a prime ('). In contrast to the first exemplary embodiment, in the support ring 20' according to the second exemplary embodiment, the free ends 28' of the spring tabs 26' face the pressure chamber 14, i.e. away from the shoulder 84' of the support ring 20 '. In particular, this simplifies the production of the support ring 20', since the production or bending of the spring tabs 26' can be reversed in a more stable manner. Functionally, there is no difference between the two exemplary embodiments.

The central release unit has a cylinder housing which defines an annular pressure chamber around a central axis, in which chamber an annular piston is guided in a movable manner. The release bearing is held on the annular piston by means of a support ring, the sleeve portion of which surrounds the end of the annular piston. The sleeve portion has a plurality of spring pieces which are elastically engaged in designated recesses of the annular piston and pull the contact surface of the support ring toward the end surface of the annular piston. There is a defined radial play between the support ring and the annular piston, allowing a rolling movement of the contact surface of the support ring on the end face of the annular piston. To engage the spring plate, the recess of the annular piston has a ramp region with a gradient (ramp angle) such that during said tumbling motion the spring plate can slide along the central axis on the ramp region without self-damping, thereby applying a restoring force to the support ring against the tumbling motion.

List of reference numerals

10 Central Release Unit

12 cylinder shell

14 pressure chamber

16 release bearing

18 ring piston

20. 20' support ring

22 end of the tube

24. 24' sleeve part

26. 26' spring leaf

28. 28' free end

30 recess

32. 32' contact surface

34 end face

36 ramp region

38 inner cylinder wall

40 outer cylinder wall

42 pressure port connection

44 channel

46 flange portion

48 fixed holes

50 Gear box wall

52 end face

54 preloaded spring

56 axial grooves

58 spring plate

60 sealing sleeve

62 sealing sleeve foot

64 axial grooves

66 reinforcing sleeve

68 latch connection

70 inner ring

72 outer ring

74 roller body

76 holder

78 sealing disk

80 fixed part

82. 82' ring portion

84. 84' shoulder

86. 86' contact surface

88 cup spring

90 spring tongue

92 conical surface

94. 94' bending region

96. 96' circular area

98 grease bag

100 shoulder

102 fixed ring

104 collar

106 connecting chamfer

108 beating area

109 longitudinal rib

110 discontinuous cylindrical surface

112 end region

114 contact area

d inner diameter of support ring

s radial play

Outside diameter of D-ring piston

Length of L support ring

M center axis

Angle of Α slope

Angle of inclination of beta