CN115492876A - Center release device for pneumatically actuated friction clutch - Google Patents

Abstract

The invention relates to a central decoupling device (10.

Description

Center release device for pneumatically actuated friction clutch

Technical Field

The invention relates to a center release device for pneumatically actuating a friction clutch.

Background

Different kinds of central disconnection devices are known in the prior art. These central uncoupling devices have a cylinder and a working piston which are designed in such a way that they can move axially relative to one another. In order to shield the sealing and guiding elements of the central disconnection device against dirt, a dirt shield is provided for this purpose. In the same way, different inner chambers are formed on the central decoupling device by means of components, the volume of which chambers changes during the axial relative movement of the working piston and the cylinder. Ambient air is sucked in by this change in volume of the interior space and the sucked-in air is likewise blown out again. Since such a central decoupling device is arranged inside the drive train, in particular inside the transmission bell, the environment has a high concentration of dirt particles which are also floating in the ambient air. The intake of ambient air containing dirt particles can lead to a reduction in the service life of such central disconnection devices.

Disclosure of Invention

The object of the invention is therefore to provide a central disconnection device in which contamination is prevented or reduced as significantly as possible during operation.

This object is achieved by a central disconnection device according to claim 1. Advantageous design variants are set forth in the dependent claims.

Such a central disconnection device is used for pneumatically actuating the friction clutch. Friction clutches of this type are usually designed in motor vehicles, in particular in freight vehicles, within the drive train.

The central decoupling device comprises a cylinder, a working piston, a decoupling bearing and a preload spring, wherein the cylinder and the working piston are configured in an axially movable manner relative to one another and together define a variable pressure chamber. The release bearing provides for the axial actuating movement of the central release device to be transmitted to the rotating friction clutch. The preload spring provides an axial prestress between the cylinder and the working piston, so that the working piston is left in a defined position at any time and in particular provides an abutting contact between the decoupling bearing and the friction clutch at any time.

Furthermore, a first compensation chamber and a second compensation chamber, the respective volumes of which change during the relative movement between the cylinder and the working piston, are formed on the central decoupling device, wherein the first compensation chamber and the second compensation chamber are connected to one another by a compensation channel. The first compensation chamber and the second compensation chamber have inner chambers separated from each other. These inner chambers are produced by the different components of the central decoupling device and their structure. The volumes of these chambers change during the axial relative movement between the working piston and the cylinder, i.e. during disconnection. The compensation chambers are connected to one another by compensation channels, so that the air present in the inner chamber of the central disconnection device can flow back and forth between the compensation chambers. Advantageously, two or more compensation chambers are provided with a corresponding number of compensation channels in order to connect the two or more inner chambers. Preferably, the compensation chambers are connected to one another in pairs. The compensation chambers are configured in a complementary manner to one another with respect to their volume change in the relative movement of the working piston and the cylinder. This means that upon axial relative movement of the working piston and the cylinder, one compensation chamber obtains a volume enlargement and the other compensation chamber obtains a volume reduction. One of the compensation chambers thus receives the displaced air of the other compensation chamber. Thereby, the overpressure and underpressure inside the compensation chamber are reduced or at least significantly reduced with respect to the environment. The intake of dirty ambient air is thereby prevented or at least strongly reduced. The service life of such a central disconnection device is considerably increased.

The ambient or ambient air is the air surrounding the central decoupling device outside the components of the central decoupling device. Preferably, the compensation channel extends in the radial direction and/or in the axial direction. It is advantageous if a single compensation channel or a plurality of compensation channels are formed. Such a compensation channel can be formed, for example, by a perforation or a cut in one of the components. Such compensation channels are advantageously drilled by drilling. Alternatively, such compensation channels are already drawn out during production by casting or diecasting. A multi-part piston construction can be envisaged, the parts of which are fixedly connected to one another, wherein the compensation channel is provided at the connection region. Other possibilities for providing one or more compensation channels can also be envisaged. The compensation chambers are preferably arranged axially or radially with respect to each other.

In the following, advantageous embodiments of the central disconnection device are explained.

It is proposed that at least one of the compensation chambers is closed off from the environment.

The compensation chamber is advantageously sealed or hermetically closed with respect to the environment. Advantageously, one, two or more of these compensation chambers can be respectively closed or sealed off from the environment. In this embodiment, however, it may occur that, despite the volume compensation, a certain degree of overpressure or underpressure occurs inside the compensation chamber. This can be compensated, for example, by elastic shielding elements which compensate to some extent for such overpressure and underpressure.

It is further proposed that at least one of the compensation chambers is connected to the environment.

This can be achieved, for example, by means of an external air duct. Such an external air duct is formed, for example, by an opening having a small cross section. Such openings allow compensation for the applied overpressure and underpressure, but are designed such that no or only a negligible exchange of air takes place with the environment in addition to the overpressure or underpressure. It is advantageous to design such an external air channel such that the overpressure or underpressure inside the compensation chamber is compensated with respect to the environment not abruptly, but over a longer period of time, for example over a time range of a few seconds or a few minutes. Preferably, a filter element is arranged at the opening to the environment, which filter out dirt particles from the overflowing air. This can be provided, for example, by a felt. The compensation chamber is preferably formed with a plurality of external space channels. One or more external air channels are advantageously provided for each compensation chamber. By means of these external air channels, the overpressure or underpressure can be reduced with respect to the environment. By means of the volume compensation of the compensation chamber inside the central decoupling device, the amount of ambient air sucked in is already significantly reduced compared to the embodiments of the prior art. It is particularly advantageous if at least one of the compensation chambers is closed off from the environment by a shielding element, in particular a roller-folded airbag, a bellows-folded airbag or a protective covering.

It is particularly advantageous if both or all compensation chambers have corresponding shielding elements.

Such a shielding element closes or shields the compensation chamber from the environment. Finally, the closure provides an air-tight closure or a substantially air-tight closure, while the shielding provides a pressure compensation of the compensation chamber with respect to the environment, for example via an external air channel. It is particularly advantageous if the radially inner compensation chamber is provided with a roller-folded airbag or a bellows-folded airbag. A protective cap is advantageously formed on the radially outer compensation chamber. Such a protective cover is advantageously made in the form of a sleeve. In particular, a scraper element is formed on the protective hood. Such a scraper element can be realized, for example, by a felt. On the one hand, this felt is air-permeable, but prevents the penetration of dirt particles. Correspondingly, a scraping element in the form of a felt can provide an external air channel.

In a preferred embodiment, the shielding element is fixed between the release bearing and the piston or between the release bearing and the cylinder.

The shading elements are particularly advantageously designed in the form of bellows-type folding airbags (Faltenbalg) or roller-type folding airbags (Rollbalg). It is particularly advantageous if the shielding element is a radially inner shielding element. The screening element is advantageously clamped between the decoupling bearing and the piston or between the decoupling bearing and the cylinder. Advantageously, an axial end or an axial end region of such a shielding element engages in a corresponding retaining groove of the piston or cylinder. The central decoupling device can be distinguished between a first type and a second type, wherein for the first type the cylinder is of fixed design and the working piston is of movable design; and for the second type the working piston is of fixed position and the cylinder is of movable design. Depending on the type of central disconnection device present, the fastening of the shielding element is preferably carried out on the movable components in the working piston and the cylinder. It is particularly advantageous if the respective shielding element is fastened to the guide tube on the other hand. Another screening element is constructed in the form of a protective cover. Such a protective cap is preferably arranged radially on the outside on the central disconnection device.

The screening element is advantageously engaged on said piston.

The shielding element is advantageously a shielding element in the form of a protective cap. It is particularly advantageous if such a shielding element is arranged radially outside on the central disconnection device. By means of the latching device, on the one hand a simple assembly and on the other hand a secure fastening is provided.

It is particularly advantageous if the compensation channel is formed on the piston or on a guide element.

The guide element is a component which is fixed to the piston or cylinder and provides a guide in the interior of the central disconnection device. Generally, the guidance of the guide element is performed by a guide strip providing a sliding movement relative to the guide tube. Advantageously, the movable cylinder, which is designed in relation to the stationary working piston, has a guide element.

It is also proposed that the compensation channel is formed by a cut or a perforation.

The perforations can be configured, for example, by drilling. Alternatively, such a perforation is already cut into the component during production by casting or die casting. The perforations depict openings that extend completely through the member. For example, a cutout (einkerrbung) can be formed in the component radially on the outside or radially on the inside. The cut-out is constituted, for example, by a groove. The cutouts are formed, for example, on the guide element, so that a corresponding compensating channel is provided between the guide element and the cylinder.

In an advantageous embodiment, at least one of the compensation chambers is connected to the environment via an external air duct.

Such an external air channel provides a connection between the compensation chamber and the environment. This makes it possible to reduce possible overpressures or underpressure which occur during the axial relative movement but which cannot be compensated completely by the volume compensation inside the compensation chamber. In particular, a reduction in the sucked-in ambient air can thereby be achieved.

Drawings

The center clutch is explained below by way of example with reference to two figures. The figures show:

figure 1 is a first embodiment variant of a central uncoupling device;

fig. 2 is a second embodiment variant of the central disconnection device.

Detailed Description

In fig. 1, a pneumatic central disconnection device 10 is shown. The center disconnect 10 includes a cylinder 12, a working piston 14, a disconnect bearing 16, and a preload spring 18. The cylinder 12 and the working piston 14 are designed to be axially movable relative to one another and together define a variable pressure chamber 20. The cylinder 12 and the working piston 14 are sealed with respect to each other by sealing elements. Furthermore, the working piston 14 is guided relative to the cylinder 12 by a guide belt. The cylinder 12 includes a cylinder tube 12a and a guide tube 12b. In this center release device 10, the cylinder 12 is formed in a stationary manner. This means that the cylinder 12 is arranged fixedly in the interior of the drive train, in particular on the transmission housing, wherein the working piston 14 executes a relative movement with respect to the cylinder 12. The fastening within the drive train is effected by a fastening plate 22, which is screwed, for example, to the gear housing. The cylinder 12 is fixed to a fixing plate 22.

The release bearing 16 is fixed to the working piston 14 by means of a pretensioning element 24. The pretensioning element 24 is designed here as a hooked wave spring. The release bearing 16 is thereby axially preloaded against the working piston 14, but is radially centered relative to the diaphragm spring of the friction clutch, not shown here. The axial relative movement of the working piston 14 for actuating the friction clutch, not shown, is transmitted to the friction clutch. The preload spring 18 is arranged inside the pressure chamber 20 and provides an axial prestress of the working piston 14 in the direction of the diaphragm spring of the friction clutch.

Furthermore, the central coupling device 10 has a sensor device 26, which detects the axial relative movement of the working piston 14 with respect to the cylinder 12. To this end, the sensing mechanism includes a position transmitter 28 and a position sensor 30. The position encoder 28 is designed, for example, as a magnet, which executes a common movement with the working piston 14. In order to ensure that the position encoder is detected by the position sensor, a rotation stop 32 is provided. The rotation-blocking device comprises a first guide element 34 arranged on the position sensor side and a second guide element 36 arranged on the position transmitter side. The guide elements 34 and 36 provide circumferential contact surfaces corresponding to one another, which cooperate in order to prevent a relative rotation of the working piston 14 relative to the cylinder 12. The first guide element 34 is fixed to the fastening plate 22. The second guide element 36 is fixed to the working piston 14. The position transmitter 28 is accommodated in the recess of the second guide element 36.

Furthermore, a first shielding element 38 and a second shielding element 40 are formed on the central coupling device 10. These shielding elements 38 and 40 shield the pressure chamber 20 and the associated sealing elements and guide elements from dirt. This prevents the ingress of dirt which could significantly reduce the service life of the central disconnection device.

The first shielding element 38 is arranged radially inside and is fastened on the one hand to the guide tube 12b and on the other hand to the working piston 14. The first screening element 38 is designed as a roller-type folding airbag which can be rolled up and unrolled in each case upon an axial relative movement of the working piston. For this purpose, corresponding recesses are formed on the working piston, into which the roller-fold airbag can be inserted during its movement. Alternatively, the roller-folded airbag can also be configured as a bellows-folded airbag.

The roller-fold airbag is fixed to the working piston 14 between the working piston 14 and the release bearing 16. The roller-fold airbag engages in a corresponding recess of the working piston. At the same time, the roller-folded airbag is clamped between the working piston and the decoupling bearing by means of the decoupling bearing 16 or is prestressed axially in relation to the working piston. This provides a secure attachment of the roller-folded airbag to the working piston 14.

The second screening element 40 is constituted by a protective cover in the form of a sleeve. The protective cover is advantageously made of plastic. The protective cap has a latching lug on the side facing axially toward the working piston 14, which cooperates with the latching lug of the working piston. A secure fixation is provided by such a snap lock device. In particular, the protective cap and the working piston execute a common movement. On the axially opposite side, a scraper element 42 is formed on the second shielding element 40. The scraper element 42 slides on the cylinder pot 12a and prevents the penetration of dirt particles. The scraper element 42 is advantageously configured as a felt (Filz). Such a scraper element 42 also represents a filter element. Furthermore, the scraper element 42 provides an external air passage.

The first shield element 38, the working piston 14 and the guide tube 12b together define a first compensation chamber 44. The second shutter element 38, the working piston 14 and the cylinder pot 12a together define a second compensation chamber 46. The first compensation chamber 44 and the second compensation chamber 46 each have a variable volume. These volume changes occur during the axial relative movement of the working piston 14 with respect to the cylinder 12. The first compensation chamber 44 and the second compensation chamber 46 are connected to each other by an external air passage 48. Through the compensation channel 48, the volume changes occurring, which lead to an overpressure and an underpressure and thus to a restricted air flow between the compensation chambers, are compensated.

If the working piston 14 executes an axial movement which causes an expansion of the pressure chamber 20, the volume of the first compensation chamber is reduced and the volume of the second compensation chamber 46 is expanded. The air which is forced out of the first compensation chamber 44 can flow into the second compensation chamber 46 via a compensation channel 48. If the working piston 14 executes an axial relative movement which reduces the pressure chamber 20, the air which is displaced out of the second compensation chamber 46 flows into the first compensation chamber 44. The compensation chambers 44 and 46 are selected such that the volume changes of the compensation chambers 44 and 46 differ from each other as little as possible. This achieves that no or only a small overpressure or underpressure relative to the environment arises in the interior of the compensation chambers 44 and 46. Thereby preventing or at least strongly reducing the suction or blowing out of air from the compensation chamber into the environment. Thereby preventing the intake of contaminated air from the environment.

The compensation channel 48 is formed on the working piston 14. A plurality of compensating channels 48 is advantageously provided on the piston. These compensating channels are advantageously arranged uniformly distributed in the circumferential direction. Such compensation channels 48 can be established, for example, by drilling. Likewise, such compensating ducts 48 can be integrally cut directly during production, for example, by casting or injection molding.

Furthermore, an external air channel 50 is formed on the working piston 14. These external air passages 50 are optional. In particular, these external air ducts provide a connection to the environment. In the case where the volume changes of the first compensation chamber 44 and the second compensation chamber 46 are different from each other, the difference can be compensated for by the outside air passage 50. Nevertheless, much less air is thereby introduced into the compensation chamber from the environment. These outer space channels 50 are formed here on the working piston 14 in the region of the decoupling bearing. In particular, the external air ducts are arranged uniformly distributed over the circumference.

Another center disconnect 110 is shown in fig. 2. The basic operating principle is the same as for the central decoupling device 10. However, the center coupling device 110 is different from it in terms of its structure. The cylinder 112 is designed to be axially movable relative to a stationary working piston 114. The cylinder 112 and the working piston 114 define a pressure chamber 120 which is sealed with respect to the environment by means of a sealing element. The disconnect bearing 116 is disposed on the cylinder 112. Here too, the axial movement of the cylinder 112 provided is transmitted via the decoupling bearing 116 to the diaphragm spring of the friction clutch, not shown. The release bearing 116 is here also arranged on the cylinder 112 via a prestressing element 124 in the form of a hooked wave spring and is prestressed axially with respect thereto. The pretensioning element 124 is supported on a support plate 152, which is in turn fastened to the cylinder 112. The cylinder 112 is guided and supported relative to the guide tube 154 by a guide member 156. The guide tube 154 is connected to the fixing plate 122. The fastening plate is also used here to fasten the central release device in the interior of the drive train and furthermore to provide a base support for fastening all further components.

The guide element 156 is fixedly connected to the cylinder 112, for example, by means of a press connection. Alternatively, the guide member 156 is welded to the cylinder 112. A guide strip is formed on the guide element 156, which comes into contact with the guide tube 154 and provides a sliding support for the axial movement of the cylinder 112.

The preload spring 118 is disposed outside of the pressure chamber 120 in the center disconnect 110. In particular, the preload spring 118 is arranged radially inside the pressure chamber 120, wherein it is supported axially on the one hand on the guide element 156 and axially on the other hand on the fastening plate 122. The working piston 114 is fixed to the fixed plate 122 so that the support of the preload spring 118 on the fixed plate 122 simultaneously provides indirect support on the working piston 114. The working piston 114 is substantially U-shaped in cross section. Within a receiving chamber 158, which is delimited by the working piston 114 and the fastening plate 122, further components of the drive train can be received. The present invention relates to compressed air valves 160, which control the supply of pressure medium, in particular air, into the pressure chambers and the discharge thereof from the pressure chambers. However, the illustration of the compressed air valve 160 is shown in fig. 2 only in simplified form. Furthermore, an opening is formed in the working piston 114, which opening provides a connection between the pressure valve 160 and the pressure chamber 120.

The center disconnect 110 also includes a sensing mechanism 126 having a position transmitter 128 and a position sensor 130. In this case, the position sensor is also designed to be stationary and is connected to the fastening plate 122. Thereby indirectly providing a fixation on said working piston 114. The position transmitter is in turn arranged and fixed on the support plate 152, so that the position transmitter 128 is fixedly connected indirectly to the cylinder 112. The position transmitter, which is preferably designed as a magnet, thus executes a common movement with the cylinder 112.

Likewise, the rotation stop device 132 is configured with a first guide element 134 and a second guide element 136. The first guide element 134 is fixed to or formed by the fastening plate 122. The second guide element arranged on the cylinder side is fixed to the support plate 152. In particular, the second guide element 136 accommodates the position transmitter in the recess. Here, too, the guide elements provide a corresponding circumferential contact surface or contact area, which are designed to support and maintain a defined relative orientation of the cylinder 112 with respect to the working piston 114 in a circumferential manner with respect to one another.

Furthermore, a first shielding element 138 and a second shielding element 140 are provided on the central disconnection device 110.

Said first screening element 138 is arranged radially inside. The first screening element 138 is constructed by a bellows-type folding airbag which is fastened on the one hand to the guide tube 154 and on the other hand to the cylinder 112. The fastening to the guide tube 154 is effected by means of a snap ring, wherein the fastening to the cylinder 112 is effected in a similar manner, as is the case with the embodiment variant shown in fig. 1, in which the roller-fold airbag 38 is fastened to the working piston 14. In particular, the first shielding element 138 is clamped between the cylinder 112 and the decoupling bearing 116. For an axial relative movement of the cylinder 112, the first screening element 138 provides a corresponding folding movement. A sealed covering is substantially provided by the selected fixture.

The second screening element 140 is designed as a protective cover. The protective cover has a sleeve shape. The second shielding member 140 is fixed to the operating cylinder 112. Here, the second screening element 140 also has a scraper element 142, which is accommodated in the recess. In particular, this relates to felts. The scraper element 142 is preferably designed to be circularly circumferential.

The first compensation chamber 144 is defined by said shielding element 138, guide tube 154 and guide element 156. The second compensation chamber 146 is defined by said guide element 156, the fixed plate 122, the working piston 111 and the cylinder 112. In the axial relative movement of the cylinder 112, both the first compensation chamber and the second compensation chamber acquire a volume change. The pressure inside the compensation chamber is increased or decreased by this volume change. For this purpose, a compensating channel 148 is provided, which enables pressure compensation between the first compensating chamber 144 and the second compensating chamber 146. Advantageously, a plurality of compensation channels 148 are configured.

The compensation channel 148 is provided by a guide member 156. In particular, the guide channel 148 is formed by a corresponding radially outer recess in the guide element 156, so that a small channel is provided between the cylinder 112 and the guide element 156.

For an axial relative movement of the expanding pressure chamber 120, the volume of the first compensation chamber 144 decreases, whereas the volume of the second compensation chamber 146 increases. The air can overflow from the first compensation chamber 144 into the second compensation chamber 146 via the compensation channel 148. If the cylinder 112 performs an axial movement providing a reduction of the volume of the pressure chamber, the volume of the second compensation chamber 146 is also reduced, while the volume of the first compensation chamber 144 is enlarged. The air can now flow from the second compensation chamber 146 into the first compensation chamber 144 via the compensation channel 148. As a result, an overpressure or underpressure with respect to the environment of the pneumatic central decoupling device 110 can be effectively avoided or at least reduced. In this way, the intake of air into the compensation chamber and the blowing out of air from the compensation chamber are reduced or prevented. In particular, less dirty ambient air is sucked in and contamination of the sealing and guide surfaces of the central release device 110 is prevented.

The first screening element 138 is elastically designed such that it can withstand possible overpressures or underpressure caused by the total volume change of the first and second compensation chambers. Thus, no ambient air is sucked or blown through the sealed structure. The same is also possible in the central disconnection device 10 according to fig. 1. In particular in the embodiment variant in the form of a seal, no external air channel is provided. In principle, the volumes of the compensation chambers are matched to one another as good as possible, so that the change in volume of the first compensation chamber is substantially equivalent to the change in volume of the second compensation chamber.

The compensation chambers of the central uncoupling device 110 are arranged axially with respect to each other. The compensation channel accordingly extends in the axial direction. In the embodiment according to fig. 1, the first compensation chamber and the second compensation chamber are arranged radially with respect to each other. The compensation channel extends in the radial direction.

List of reference numerals:

10. center disconnecting device

12. Cylinder

12a cylinder tank

12b guide tube

14. Working piston

16. Disconnecting bearing

18. Preloaded spring

20. Pressure chamber

22. Fixing plate

24. Pretensioning element

26. Sensing mechanism

28. Position transmitter

30. Position sensor

32. Torsion stop device

34. First guide element

36. Second guiding element

38. First shielding element

40. Second shielding element

42. Scraping element

44. First compensation chamber

46. Second compensation chamber

48. Compensation channel

50. External air passage

110. Center disconnecting device

112. Cylinder

114. Working piston

116. Disconnecting bearing

118. Preloaded spring

120. Pressure chamber

122. Fixing plate

124. Pretensioning element

126. Sensing mechanism

128. Position transmitter

130. Position sensor

132. Torsion stop device

134. First guide element

136. Second guiding element

138. First shielding element

140. Second shielding element

142. Scraping element

144. First compensation chamber

146. Second compensation chamber

148. Compensation channel

152. Supporting plate

154. Guide tube

156. Guiding element

158. Accommodation chamber

160. Compressed air valve

Claims (9)

1. A center disconnect (10:

a cylinder (12, 112), a working piston (14, 114), a release bearing (16,

wherein the cylinder (12,

wherein a first compensation chamber (44, 144) and a second compensation chamber (46, 146) are also formed on the central decoupling device (10,

wherein the first compensation chamber (44.

2. The central disconnect device (10.

3. The central disconnect device (10.

4. A center disconnect device (10.

5. A central disconnection device (10.

6. Center disconnect device (10.

7. Center disconnect device (10.

8. The central breakout device (10.

9. Center disconnect device (10.

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