WO2009026879A1

WO2009026879A1 - Clutch disengagement system

Info

Publication number: WO2009026879A1
Application number: PCT/DE2008/001317
Authority: WO
Inventors: Berthold Altmeppen; Andrej Kubicek
Original assignee: Luk Lamellen Und Kupplungsbau Beteiligungs Kg
Priority date: 2007-08-30
Filing date: 2008-08-11
Publication date: 2009-03-05
Also published as: BRPI0816120A2; DE102008037328A1; EP2188542A1; DE112008002153A5

Abstract

The invention relates to a clutch disengagement system, wherein at least one cylinder has a sealing groove for a dynamic seal, the contact area of said groove being reduced in relation to a smooth surface.

Description

Kupplunqsausrücksystem

The invention relates to a clutch release system having at least one cylinder for actuating a friction clutch by means of a release system.

Such Kupplungsausrücksysteme are known in hydraulic or pneumatic design. In this case, an axial force transmitted by the driver via the clutch pedal, an auxiliary power actuator such as servo unit or by an automated clutch actuator to a piston axially displaceable in a master cylinder housing which exerts pressure in the master cylinder on the fluid used for pressure transmission, the pressure built up via a pressure line transmits a slave cylinder, the piston is then axially displaced and transmits, for example, on plate spring tongues of the friction clutch, depending on the design - forcibly closed or forcibly opened - is opened or closed. Alternatively, the function of the master cylinder can be taken over by a hydraulic pump or a pressure accumulator and the slave cylinder can be selectively supplied with pressure by an intermediate control valve.

In order to effectively seal the master and slave cylinders, a dynamic seal is placed on the piston or in the housing wall or a corresponding component which is moved in sliding contact with the surface on which it seals. To increase the sealing properties as smooth as possible surfaces and seals provided with sealing lips are used. Due to the ever higher system pressures, the friction between seals and surfaces increases, so that the wear of the seals due to the higher contact pressure and / or the actuating forces can increase.

It is therefore the object to propose clutch release systems, in which the wear properties and / or the friction between the seal and the surface are improved.

The object is achieved by a clutch release system having at least one cylinder containing a fluid, whereby a disengagement unit of a friction clutch is displaced axially in dependence on a pressure of the fluid built up in the at least one cylinder and the friction clutch is actuated therewith, consisting of a housing axially displaceably guided in a housing Piston with a seal that is relative to the displacement of the piston is guided to a surface, solved, wherein the surface has a relation to a smooth surface reduced support portion for the piston.

The cylinder can be a master cylinder, a slave cylinder concentrically arranged around a transmission input shaft with an annular piston (central release) or a slave cylinder designated as a slave cylinder in a simple design with a piston with a fully cylindrical pressure surface, the piston by means of an actuating lever on an off or Engagement bearing the friction clutch acts. Furthermore, the seal may be provided on the piston, for example as a U-ring seal on an annular piston in a Zentralausrücker, wherein at least one of the surfaces, namely belonging to the housing outer surface or to a guide sleeve, which may also be part of the housing, associated inner surface. Furthermore, the seal may be arranged in the housing, for example in a master cylinder or a semi-cylinder. It will be appreciated that in addition to these preferred embodiments, other arrangements incorporating one or more dynamic seals sliding on a surface are also encompassed by the invention. For example, this may be a so-called secondary seal contained in the master cylinder for sealing the inner space relative to the outer space, which also seals between the piston and the housing, wherein between the pressure chamber sealing primary seal and the secondary seal may be an inlet for a fluid expansion tank.

The solution of the problem is suitable for hydraulic and pneumatic Kupplungsausrücksysteme, so that the fluid may be a liquid pressure medium, such as polyglycols or other liquids or oils with lubricating properties and high boiling point, or a gas such as air.

Under the support portion is the ratio of the area that can come into contact with the seal to understand the total geometric area of the sealing surface. In the further course, the percentages of the percentage of load on the total geometric area of the surface are given for details of the carrying percentage. A reduction of the carrying component is achieved in the sense of the invention in that evenly distributed over the surface depressions or elevations are present, which are tuned in their lateral extent so that the elasticity of the seal is not sufficient to penetrate into the recesses formed by the depressions or elevations and to follow the surface forms formed there. On the contrary, at least microscopically, a passage through the sealing path covered by the seal is created at these depressions. The use of a surface whose Tragige portion for the seal is lowered, therefore, for the sake of tightness first seems outlandish. It is expected that the sealing contact will be inadequate and the seal / surface sealing system will leak, especially as the pressure increases. Surprisingly, it has been found that when the support portion is lowered, the wear and the actuation forces, that is, the friction of the seal on the surface at an applied pressure, can be reduced. It has further been shown that the carrying fraction can advantageously be reduced to values of less than 20%, preferably less than or equal to 10%.

It has also proven to be advantageous if components with the desired reduced Traganteilen made of plastic. Particularly advantageous components with the desired reproducible designed plastic surfaces can be produced by injection molding. In this case, the plastic surfaces can be tool traps without further fine machining, if the injection molding tools used for their preparation are vorzuietet according to a reduction of the supporting portion. Thus, for example, the surfaces of the injection molding tool, which are to form a region with a reduced support component, can be prepared accordingly by introducing the desired surface with a reduced support component already as a negative mold. It is understood that corresponding shrinkage effects are already taken into account during production.

However, the reduced support surface may, for example, advantageously include uniformly distributed dimples, crests or similar geometric shapes of different sizes within a given size distribution, rounded in such a way that no shearing action on the seal corresponding to the surface occurs. Accordingly, corresponding depressions formed in the negative are provided in the injection molding tool. In special cases, the injection molding tool itself may have the elevations, whereby in the surface following the negative image depressions are impressed into the surface during the production of the component carrying this surface.

It has been shown that the depressions should be performed advantageously within a given surface quality. The measured roughness depth can be used as the measured variable, in which the mean values of empirically determined roughness depths are evaluated. On the basis of this measure, average roughness depths less than or equal to 4 μm have proved to be advantageous. Furthermore, it has proved to be advantageous if lubricant is introduced into the recesses of the surface. The depressions can serve as a lubricant supply and additionally or alternatively eliminate the interference caused by the reduction of the bearing component disturbances of the sealing section by filling the wells. In this case, due to the low geometric expansion with the occurring pressure components already a lubricant of ordinary viscosity may be suitable to bring about an improvement in the tightness. In terms of fatigue strength and temperature resistance, it may be advantageous to use a temperature-resistant and high-viscosity lubricant. A lubricant which contains particles of fluorohydrocarbons, for example PTFE, has proved particularly advantageous. For the technical background of this lubricant reference is made to the document DE 101 34 999 A1.

Components according to the invention are advantageously produced by means of an injection molding tool with a surface located in the injection chamber, wherein a surface portion at which the surface is formed for a sealing career of the component, an average roughness depth is set equal to 4 microns. By adjusting this surface roughness, a corresponding surface can be impressed on the components provided for the sealing contact with the seals, such as pistons, housing parts and / or guide sleeves, or preferably provided in the injection molding production process.

It has proved to be particularly advantageous if the desired surface structure for reducing the carrying portion in the injection molding tool is provided as a negative die by at least the surface portion which forms the contact surface with the seal being eroded. The degree of erosion is chosen so that a corresponding average roughness depth is achieved. In particular, the shape of the surface which results from the erosion process for a given roughness depth is advantageously suitable for the reduction of the support component. The erosion process produces dome-shaped or knob-like surface structures that are rounded and similar to the lotus effect. Furthermore, other designs of the surface in the form of patterns that can be repeated regularly in lateral E-benes or randomly distributed patterns depending on the application possible. For example, lotus-like patterns may be provided. Advantageous results have been achieved with EDM processes according to VDI Standard 3400, with erosion in stages 13 to 18, preferably step 15, giving particularly advantageous results.

The invention will be explained in more detail with reference to Figures 1 and 2. Showing: Figure 1 is a schematically illustrated embodiment of a clutch release system

and

FIG. 2 is an illustration of an enlarged surface with a reduced bearing component.

Figure 1 shows a schematic representation of a possible embodiment of a clutch release system 1 with a master cylinder 2 and connected by means of a line 3 to the master cylinder slave cylinder 4. Between the line parts 5 and 6 or integrated in master cylinder or slave cylinder, a filter 7, as a pressure relief valve and / or can serve as a so-called Kribbelfilter be installed.

The clutch release system 1 actuates the friction clutch 8 hydraulically by acting on the master cylinder 2 by means of an actuator 9, which may be a foot pedal, an actuator, such as an electric actuator, or the like. As a result, 10 pressure in the master cylinder 2 is constructed by means of a mechanical transmission, which builds up a pressure in the slave cylinder 4, which is designed as a central release via the line 3. The slave cylinder 4 brings about an actuating bearing 12, the necessary disengaging force to the friction clutch 8, or at the actuating elements 11, for example, a plate spring or an actuating lever. The nature of the tension of the actuators 11 with the clutch cover 13 determines whether it is an on or pushed clutch. Accordingly, when the actuating bearing 12 is acted upon, the coupling is opened by the annular piston 14 or, in the case of a compressed coupling (not shown), closed by the annular piston. The transmission input shaft 15 transmits the closed friction clutch 8, the torque of - not shown-, with the clutch rotatably connected to an internal combustion engine not shown in detail and then to the drive wheels of a motor vehicle.

The proposed structure of the surface while reducing the supporting portion may be provided on the surface 2b of the piston 2a in the master cylinder 2. The master cylinder 2 contains two - not shown - lip seals, a lip seal seals the pressure chamber 2c as a primary seal by fixedly disposed in the housing of the master cylinder 2 and forms a dynamic sealing contact with its sealing lip upon displacement of the piston. Axially spaced, the second lip seal is arranged as a secondary seal fixed in the housing, the sealing lip also seals on the piston 2a, the master cylinder to the outside. Between the two seals of the inlet for the reservoir 17 is provided. Alternatively or additionally, in the slave cylinder 4, the slave cylinder piston 4a, which is formed as an annular piston 4a and has a U-ring seal 4b, which may be in sealing contact with the outer surface 4c of the housing of the slave cylinder 4 and with the inner surface 4d of the guide sleeve. Advantageously, the guide sleeve is integrated into the slave cylinder in a slave cylinder 4 made of plastic. In other embodiments, the guide sleeve may be formed of metal and connected to the housing of the slave cylinder 4. Depending on the design of the slave cylinder, a surface-outer surface 4d or inner surface 4c-can form a contact with a reduced bearing component with the U-ring seal. In this case, surfaces may be formed from plastic by the injection molding tool used for the preparation of a suitably prepared counter surface, which is eroded in an advantageous manner, or made of metal sealing surfaces, which are themselves eroded. For erosion of metal, the statements made above apply mutatis mutandis.

FIG. 2 shows an exemplary embodiment of an enlarged representation of a plastic surface produced in an injection molding tool which was produced in the relevant surface area according to VDI method 3400, step 14 and has an average roughness depth of 4 μm.

LIST OF REFERENCE NUMBERS

Claims

claims

A clutch release system (1) having at least one cylinder containing a fluid, wherein a disengagement unit of a friction clutch axially displaces depending on a pressure of the fluid built up in the at least one cylinder, and the friction clutch (8) is actuated therewith, consisting of a housing axially displaceably guided piston (2a) with a seal which is guided during the displacement of the piston (2a) relative to a surface (2b), characterized in that the surface (2b) has a relation to a smooth surface reduced support portion for the piston (2a). 2a).

2. Kupplungsausrücksystem (1) according to claim 1, characterized in that the supporting fraction is less than 20%, preferably less than 10%.

3. clutch release system (1) according to claim 1 or 2, that the surface (2b) is formed on a plastic component, which is produced by means of an injection molding process.

4. clutch release system (1) according to one of claims 1 to 3, characterized in that the surface has rounded elevations with an average roughness less than or equal to 4 microns.

5. clutch release system (1) according to one of claims 1 to 4, characterized in that the surface (2b) on a piston (2a) of the at least one cylinder is formed.

6. clutch release system (1) according to one of claims 1 to 5, characterized in that the surface on an inner surface (4d) and / or outer surface (4c) of the at least one cylinder is formed.

7. clutch release system (1) according to one of claims 1 to 6, characterized in that in recesses of the surface (2b) lubricant is introduced.

8. Injection molding tool for producing a component of a coupling cylinder made of plastic with a surface located in the injection chamber for the production, characterized in that a surface portion at which the surface is formed for a sealing career of the component, an average roughness depth is set equal to 4 microns.

9. Injection molding tool according to claim 8, characterized in that the surface portion is eroded.

10. Injection molding tool according to claim 9, characterized in that the surface portion according to VDI 3400 in the range of stages 13 to 18, preferably stage 15 is made.