DE102017215582A1 - Pneumatic actuator with wear compensation - Google Patents

Abstract

Actuation device (10) for a friction clutch, comprising a relative to a housing (12) movable working piston (14) having a main piston (24) and an actuating piston (26) which are movable to each other, wherein between the main piston (24) and the adjusting piston (26) a clamping device (28) is formed, which prevents movement between the main piston (24) and actuating piston (26) during an actuating operation by clamping, wherein the clamping device (28) comprises a clamping body (40), which with a web (58) a first clamping surface (38) and with a second clamping surface (42) for providing the clamping effect can come into abutting contact.

Description

The invention relates to an actuating device for a friction clutch.

It is known a pneumatic actuator with a wear compensation. This has a multi-part piston which is axially displaceable relative to a housing for actuating a friction clutch. The working piston comprises a main piston and an actuating piston, which can be fixed by a clamping device. An effective length of the working piston follows a wear of the friction clutch by axial relative movement of the main piston and the actuating piston. The clamping device fixes the effective length for the respective actuating operation. For this, the clamping device comprises two clamping surfaces, between which a clamping body is clamped for fixing the effective length. The clamping body is usually designed as a ball, which comes into contact with a cylindrical surface. As a result, comparatively high surface pressure occurs.

It is therefore an object to provide an actuating device which has a wear compensation with clamping device, which provides a reliable function with a long service life.

This object is achieved by an actuating device according to claim 1. Advantageous embodiments of the actuating device are explained in the dependent claims.

The actuator is advantageously designed as a pneumatic actuator for motor vehicles, especially for commercial vehicles. On the actuating device, a one- or multi-part housing is formed, which limits a pressure chamber with a movable, in particular axially movable, working piston. The housing may for example be formed by a working cylinder which is fixedly connected to a guide tube. The working piston is displaced in the direction of a friction clutch at a pressure rise within the pressure chamber. Their spring element, in particular diaphragm spring, is in abutting contact with a release bearing of the working piston, so that the friction clutch is actuated, opened or closed during an axial displacement.

The working piston is designed in several parts and comprises a main piston and an actuating piston, which are movable, in particular axially movable, formed opposite each other. Main piston and actuator piston of the working piston are also referred to as part piston of the working piston. In an exemplary embodiment, the actuating piston slides on the guide tube, whereas the main piston slides on the actuating piston. In an alternative variant, the main piston slides on the guide tube and the adjusting piston on the main piston.

Furthermore, a clamping device is formed on the working piston, which prevents a relative movement of the main piston and the adjusting piston during an actuating operation. The clamping device thus fixes an effective length of the working piston during an actuating operation. This fixation occurs at the beginning of the actuation process and is resolved with its end.

For this purpose, an adjusting piston-side clamping surface, a main piston-side clamping surface and a clamping body are formed on the working piston. These clamping surfaces are also referred to as a first clamping surface and as a second clamping surface and can be formed directly or indirectly on the respective sub-piston. For an indirect arrangement, for example, an adjusting element on the adjusting piston and / or a clamping element may be arranged on the main piston, which are preferably fixedly connected to the respective separating piston.

One of the clamping surfaces preferably extends along the direction of movement, in particular in the axial direction, wherein the other clamping surface is conical, so that in a relative movement between the main piston and actuating piston of the clamping body comes to rest with the conical clamping surface and the clamping body is clamped between the clamping surfaces. The clamping surfaces are at least one dimension, preferably in the axial direction, formed by a straight line, these lines, including the clamping surfaces an adjustment angle α to each other. This angle α is not equal to 0 °, preferably between 5 ° - 20 °.

On the working piston, a cage element is further formed for the clamping device, which limits the clamping body in its free mobility such that they are always arranged between the clamping surfaces. In addition, the clamping body provides a first stop, which enables the conical clamping surface to approach the clamping body at the beginning of an actuating operation, whereby the fixing is provided. As a result, the clamping body can not be pushed away from the conical clamping surface without function. In addition, the clamping element has a second stop for the clamping body. This is with the end of the actuation process a stop of the cage member on the housing via the second stop on the clamp body on, so that the clamp body is held and the conical clamping surface moves away from the clamp body.

In addition, a web is formed on the first clamping surface, which can come into abutting contact with the clamping body. This track is exemplified by a groove, a groove or a flat plane on which the clamp body can roll with. This rolling takes place, inter alia, in the course of the life of a progressive relative movement between the main piston and actuator piston or the clamping surfaces and in the initiation and discharge of the actuation process. The clamping body has a corresponding rolling surface, which is assigned to the clamping surface and the web and which serves the contact system.

The formation of a web that interacts with a clamping body, allows significantly lower surface pressures. In particular, the path and its contour can be adapted to the contour of the clamping body, for example. Plane cylinder, circular sphere or ellipse ellipsoid. The web extends in the circumferential direction only over a partial circumference or a partial section of the clamping surface. At the clamping surface advantageously a plurality of webs are formed, which are conveniently adjacent to each other in the circumferential direction and advantageously form the entire clamping surface. The web, in particular the channel or the groove, advantageously extends in the direction of relative movement of the separating pistons, in particular in the axial direction. This allows the sprag to roll on the web ideally.

Such a clamping surface is exemplified as a polygon.

The clamping surfaces are advantageously formed on substantially rotationally symmetrical components and formed closed with advantage in the circumferential direction. The clamping surfaces are advantageously formed radially outside and radially within the clamping body, said clamping surfaces are conveniently described by the shape of a lateral surface of cylinder or cone.

The web is preferably formed on the radially inner clamping surface. In the known design variants hitherto meet a convex clamping surface on a convex rolling surface, such as a ball on a cylindrical surface, whereby high surface pressures occur. Due to the formation of the web, a concave clamping surface passes through the web, onto a convex rolling surface, through the ball. Alternatively, a flat clamping surface on a flat rolling surface, by cylinders, be paired with each other.

In an advantageous variant, webs are also formed on the radially outer clamping surface, in particular when using cylindrical rolling bodies. Basically, the radially outer surface pairing in the prior art is already convex-concave. The use of webs is accordingly particularly advantageous on the radially inner clamping surface.

The clamping body is favorably rotationally symmetrical about an axis of rotation, wherein the axis of rotation is at the same time also a roll axis, which extends on the actuating device conveniently transverse to the axial direction. The clamping body accordingly rolls off about the axis of rotation. The rolling surface of the clamping body is also rotationally symmetrical.

In addition, advantageous embodiments of the actuator will be explained.

Conveniently, the path of the respective clamping surface has a complementary shape to a rolling surface of the clamping body.

Due to the complementary shape design a large-area contact contact is achieved, whereby the surface pressure is kept low. For example, a web formed as a flat surface and a lateral surface of a cylinder form a complementary shape. The rolling surface may alternatively also be convex, wherein the clamping surface is concave, so that they provide a large-area contact.

It is proposed that the contour of the rolling surface, which points to the web, is rectilinear or convex.

In a cross-sectional view through the clamp body and its roll axis, one looks at the contour of the rolling surface. When using a convex contour, this can already be adapted to a clamping surface that extends radially outward. This radially outer clamping surface may in particular have a circular contour, so that no tracks have to be formed. Here are only on a radially inner clamping surface webs form, which is adapted to the contour of the rolling body. It is still possible to form webs on all clamping surfaces. This is particularly advantageous for cylindrical clamping bodies.

Advantageously, the clamping body is formed by a ball, a cylinder, an ellipsoid of revolution or a barrel with a convexly curved rolling surface.

This represents a selection of usable clamping bodies, wherein the tracks or a corresponding clamping surface without tracks have a complementary shape to allow a low surface pressure. A cylinder has a substantially rectilinear contour on its lateral surface. A ton is essentially one Cylinder, wherein the lateral surface is not rectilinear, but convexly curved.

It is particularly favorable to form the clamping surface or the path of the clamping surface concave.

Accordingly, the entire clamping surface is concave or each of the tracks of the clamping surface is concave in itself. The first is at a radially outside of the clamp body arranged and circular clamping surface of the case. The radially inner clamping surface is divided into tracks, wherein the web surfaces have a rectilinear or concave contour, depending on the clamp body used. As already explained, the formation of webs on a clamping surface radially inward and radially outward is possible. Concave always refers to the surface that is assigned to the clamp body. In particular, the tracks of the clamping surface are formed as flat planes, as a groove, as a groove or as a groove, which extend along the actuating direction or the axial direction.

In a further embodiment variant, the path of the clamping surface is formed by a flat surface.

In an alternative embodiment, the clamping surface, the web surface and / or the rolling surface on a circular contour.

The clamping surface provides a separate surface or is formed by the sum of the web surfaces of the individual webs. The circular contour results, for example, when using balls.

It is proposed that the radius of the contour of the clamping surface or the web surface is greater than or equal to a radius of the contour of the rolling surface.

Accordingly, the radius of the contour of the clamping surface is greater than or equal to the radius of the contour of the rolling surface. Alternatively, the radius of the contour of the web surface is greater than or equal to the radius of the contour of the rolling surface. This applies on the one hand for spherical clamping body and for all clamping body, which have a spherical contour, so for example, barrel-shaped clamping bodies. As a result, the surface pressure is significantly reduced. On the one hand, the clamping body optimally adapts to the web and can run along it, whereby in a clamping operation the force is distributed over a large area and thus a low surface pressure is achieved.

In a further variant, the clamping surface, the web surface and / or the rolling surface has an elliptical contour.

The elliptical contour is a variation of the circular shape, but provides substantially the same advantages.

The clamping surface may advantageously be formed on the main piston, on the adjusting piston, on an adjusting element or on a clamping element.

The clamping surface is accordingly formed indirectly or directly on the partial piston of the working piston. The arrangement on the main piston represents a direct arrangement, as well as the training on the actuator piston. Alternatively, the clamping surface may be formed on an adjusting element or on a clamping element, it being understood that at least one clamping surface is on the actuating piston side and the other clamping surface is formed on the main piston side on the working piston. The adjusting element and the clamping element are respectively secured to the main piston or the adjusting piston and perform with them a common movement. The indirect arrangement of the clamping surfaces of corresponding elements has the advantage that this manufacturing technology is easier to manufacture. In particular, an introduction of the webs into an element, which is then subsequently connected to the sub-piston, easier to accomplish, as the direct introduction into the sub-piston. In addition, this can only be the element further manufacturing processes, such as curing or a coating process, subjected, thereby saving costs.

• 1 Betätigungseinrichtung im Querschnitt, Neuzustand, Grundposition;
• 2 Betätigungseinrichtung aus 1 im Querschnitt, Neuzustand, ausgerückt;
• 3 Betätigungseinrichtung aus 1 im Querschnitt, Verschlissen, Grundposition;
• 4 Betätigungseinrichtung im Querschnitt, Frontansicht;
• 5 Vergrößerte Darstellung von 4;
• 6 Darstellung von Klemmkörper und Klemmflächen;
• 7 Stellelement;
• 8 Weitere Variante von Klemmkörper und Klemmflächen.

In the following, the actuating device will be explained in greater detail by way of example with reference to several figures. Show it:

• 1 Actuator in cross-section, new condition, basic position;
• 2 Actuator off 1 in cross-section, new condition, disengaged;
• 3 Actuator off 1 in cross-section, worn, basic position;
• 4 Actuating device in cross-section, front view;
• 5 Enlarged view of 4 ;
• 6 Presentation of clamping body and clamping surfaces;
• 7 Actuator;
• 8th Further variant of clamping body and clamping surfaces.

The 1 shows a pneumatic actuator 10 , The pneumatic actuator 10 includes a housing 12 in which a multipart working piston 14 is guided axially movable. The housing 12 and the working piston 14 form a pressure chamber 16 , which can be filled with a pressure medium, in particular air, to an axial movement of the working piston 14 to provide against the housing to actuate a friction clutch, not shown. The working piston 14 stands for this via a release bearing 18 with diaphragm springs in abutting contact. The housing 12 is by a working cylinder 20 formed, the firm and airtight with a guide tube 22 connected is.

The pneumatic actuator 10 and their components are substantially rotationally symmetric about a central axis M arranged around.

The multipart working piston 14 includes a main piston 24 and an actuator piston 26 , which are also referred to as partial pistons. The main piston 24 and the actuator piston 26 are axially movable with each other.

In addition, the working piston has 14 a clamping device 28 on, which is the effective length of the working piston 14 fixed during an actuation process by clamping. As long as the power piston 14 remains in its basic position, the sub-piston can move freely against each other and thus compensate for wear of the friction clutch. As a result, a particularly small dead space within the pressure chamber for the entire life of the friction clutch 16 provided, whereby a quick and comfortable operation of the friction clutch is made possible.

At the contact surfaces between the housing 12 and the partial piston 24 . 26 seals are designed to complete the pressure chamber airtight.

The main piston 24 is integrally formed in this embodiment by the actuating piston 26 and the case 12 guided. The adjusting piston 26 In contrast, it is designed in several parts, in particular by a flange 30 that is fixed with a slider 32 connected is. The adjusting piston 26 is about the slider 32 on the guide tube 22 guided. In addition, the slider provides 32 a sliding surface for the main piston 24 ready. The flange 30 takes next to the release bearing 18 also a position transmitter 36 for a position sensor 34 on. In addition, a spring element ensures 37 for a permanent contact with the release bearing 18 on the diaphragm spring.

The clamping device 28 is between the main piston 24 and the actuator piston 26 formed and includes a plurality of clamping body 40 , which is between two clamping surfaces 38 and 42 can be trapped. The clamp body 40 are arranged on a pitch circle and evenly distributed in the circumferential direction.

The first clamping surface 38 is here radially within the clamp body 40 arranged and Stellkolbenseitig on an actuator 44 educated. The second clamping surface is radially outside of the clamping body 40 arranged and main piston side on a clamping element 46 educated. The actuator 44 is fixed to the actuator piston 26 connected as well as the clamping element 46 firmly with the main piston 24 connected is. In an alternative embodiment, the clamping surfaces 38 . 42 also directly on the respective piston part 24 . 26 be attached.

The first clamping surface and the second clamping surface have at least one rectilinear direction of the surface. In 1 is in the axial direction or in a projection on the axial direction and the direction of actuation of the working piston 14 , The clamping surfaces 38 . 42 have an adjustment angle to each other α on.

This adjustment angle acts with a first stop 50 a cage element 48 together. The clamp body 40 are through the clamping surfaces 38 . 42 limited in the radial direction in which free mobility. In addition to this, the cage element provides 48 a first stop 50 and a second stop 52 ready, the free movement of the clamp body 40 restrict in the axial direction.

At the beginning of an actuation process, the main piston leads 24 an axial movement in the direction of actuating piston 26 out, so that the second clamping surface 42 on the clamp body 40 too moved. The clamping elements are at the latest of the first stop 50 stopped so that the conical second clamping surface 42 the clamp body 40 opposite the first clamping surface 32 can get stuck. The effective length of the working piston 14 is now fixed for the entire actuation process.

At the end of the actuation process, the working piston moves in the axial direction of the housing 12 to, with the cage element 48 first with a stop 54 of the housing 12 comes into contact. The cage element 48 remains opposite the further axial movement of the main piston 24 stand and pose with his second stop 52 a lock on the clamp body 40 ready. The clamp body 40 are released from the clamp and the main piston 24 and the second clamping surface 42 move in the axial direction to the basic position. Of the attack 54 represents a type of sensor that detects the end of the actuation process and this stop 54 over the second stop 52 to the clamp body 40 passes to effect a release of the clamping.

The free mobility between the sub-piston is now restored and a wear occurred can be compensated. The cage element 48 is via a spring element 56 biased towards the main piston, so that the cage element 48 the clamp body 40 are always positioned correctly to initiate a fixation.

In the 1 shows the pneumatic actuator 10 in new condition as well as in basic position. The 2 shows the same pneumatic actuator in the new state and in the disengaged position. In addition, the shows 3 the pneumatic actuator in the worn state in basic position. The partial pistons 24 . 26 are completely retracted into each other here. Worn refers to the state of wear of the friction clutch.

In the following figures, the clamping device and in particular the formation of clamping surface and clamping body are shown in more detail again. 4 shows a front view in cross section.

The clamp body 40 are between the clamping surfaces 38 and 42 arranged. Here are the clamp body 40 arranged on a pitch circle and evenly distributed over the circumference.

5 shows an enlarged view of 4 , The clamp body 40 are barrel-shaped and have a rolling surface 40a with a circular contour 40b on. The contour 40b of the clamp body 40 is complementary to the contour 42b the second clamping surface 42 educated. The contour of the second clamping surface is also circular. Due to the complementary design of the contour 40b to the contour 42b a large contact surface is achieved, whereby the surface pressure during a clamping operation is lower.

The first clamping surface 38 is through a variety of paths 58 formed, which are formed adjacent to each other in the circumferential direction. These tracks 58 are also in 7 to see, which shows the position element in perspective detail view. The railways 58 are formed by grooves or grooves, which extend in the axial direction and in cross-section a contour 58 exhibit. The railways 58 extend in the circumferential direction over part of the first clamping surface 38 ,

Every track 58 is a clamping element 40 assigned, with the rolling surface 40a and the track area 58a are formed complementary to each other. In particular, the contour is 58b the railway area 58a Also circular in shape, Advantageously, the radius of the web surface 38 and second clamping surface 42 same size.

The 6 shows a single barrel-shaped clamping element 40 as well as the associated first clamping surface 38 and second clamping surface 42 or the corresponding web surface 58a , The clamp body 40 convex and engages in the concave web surface 58a and the concave clamping surface 42 one. The convex-concave surface pairing causes a large contact surface and thus a low surface pressure.

The clamping element 40 is also rotationally symmetric about a rotation axis S educated. The rolling surface 40a is therefore also rotationally symmetrical. The clamp body 40 accordingly rolls with increasing wear over the rolling surface opposite the web surface 58a from.

In addition, the radius r the contour 40b of Klemmköpers 40 less than or equal to the radius R1 the contour 58a the train 58 as well as less than or equal to the radius R2 the contour 42b the second clamping surface 42 , As a result, a large-area contact surface is provided which provides an optimal distribution of the acting forces over the entire surface.

In the 7 is the actuator 44 with the tracks 58 shown. This is inexpensive to manufacture and subject as a single part in a simple and cost-effective manner further treatment methods, such as curing. The actuator 44 is accordingly fixed with the adjusting piston 26 connected. In particular, the web structure can be in a separate component in the form of an actuating element 44 or clamping elements 46 provide a simpler and cheaper, thereby an Elaborate manufacturing process for a servo piston 26 or main piston 24 with tracks 58 is avoided.

The 8th shows a further variant of sprag clamping surface pairings. Here, only a section is shown, wherein the clamping body 40 is designed as a cylinder, which has a rectilinear contour 40b having. The contour 58b the tracks 58 is accordingly also formed by a straight line. In particular, the web is formed by a flat surface. Instead of a convex-concave pairing, a straight-line surface pairing is used.

In addition to this are also on the second clamping surface 42 traces 60 formed, the web surface 60a also a straight contour 60b exhibit. As a result, a further embodiment variant is provided with a low surface pressure.

As already mentioned in the general description part, the contours can also be formed by other shapes, for example elliptical, as long as this provides a sufficiently large contact surface.

LIST OF REFERENCE NUMBERS

10

pneumatic actuator

12

casing

14

working piston

16

pressure chamber

18

release bearing

20

working cylinder

22

guide tube

24

main piston

26

actuating piston

28

clamper

30

flange

32

sliding

34

position sensors

36

locator

37

spring element

38

first clamping surface

40

clamping bodies

40a

rolling surface

40b

contour

42

second clamping surface

42b

contour

44

actuator

46

clamping element

48

cage element

50

first stop

52

second stop

54

Stop (housing)

56

spring element

58

train

58a

track surface

58b

contour

60

train

60a

track surface

60b

contour

α

setting angle

M

central axis

r

radius

R1

radius

R2

radius

S

axis of rotation

Claims (10)

Actuating device (10) for a friction clutch, comprising - A relative to a housing (12) movable working piston (14), - Which has a main piston (24) and an actuating piston (26) which are movable relative to each other, wherein - Between the main piston (24) and the adjusting piston (26) a clamping device (28) is formed, which prevents movement between the main piston (24) and actuating piston (26) during an actuating operation by clamping, wherein - The clamping device (28) comprises a clamping body (40) which can come into abutting contact with a web (58) of a first clamping surface (38) and with a second clamping surface (42) for providing the clamping action. Actuating device (10) according to one of the preceding claims, characterized in that the web (58), in particular its web surface (58a), of the respective clamping surface has a shape complementary to a rolling surface (40a) of the clamping body (40). Actuating device (10) according to one of the preceding claims, characterized in that the contour (40b) of the rolling surface (40a) facing the web (58) is rectilinear or convex. Actuating device (10) according to one of the preceding claims, characterized in that the clamping body (40) by a ball, a cylinder, an ellipsoid of revolution or a barrel with convex curved rolling surface (40a) is formed. Actuating device (10) according to one of the preceding claims, characterized in that the clamping surface (38, 42) or the web (58, 60) of the clamping surface (38, 42) is concave Actuating device (10) according to one of the preceding claims, characterized in that the webs (58, 60) of the clamping surface (38, 42) are formed by a flat surface. Actuating device (10) according to one of the preceding claims, characterized in that the clamping surface (38, 42), the web surface (58a) and / or the rolling surface (48a) have a circular contour. Actuating device (10) according to one of the preceding claims, characterized in that a radius (R1, R2) of the contour (38b, 42b) of the clamping surface (38, 42) or the web surface (58) is greater than or equal to a radius (r) of Contour (40b) of the rolling surface (40a) is. Actuating device (10) according to any one of the preceding claims, characterized in that a surface pairing of clamping surface (38, 42) and rolling surface (40a) or web surface (58a, 60a) and rolling surface (40a) is concave-convex or rectilinear rectilinear , Actuating device (10) according to any one of the preceding claims, characterized in that the clamping surface (38, 42) on the main piston (24), on the actuating piston (26), on an actuating element (44) or on a clamping element (46) is formed ,

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