DE102022124956B3 - Central clutch release, hydraulic actuation device, transmission device and electrically operated axle drive train - Google Patents

Abstract

The invention relates to a central releaser (1), in particular for a hydraulic release system of a motor vehicle (4), comprising a central releaser housing (5) with an annular central releaser piston chamber (6) in which a central releaser piston ( 8) is accommodated in an axially movable manner, the central release piston (1) having at least one central release piston seal (9) which seals the central release piston (8) against the central release piston chamber (6), the central release piston (8) being designed in a stepped manner and a first cylindrical ring-shaped piston section ( 10) with a first outer diameter (11) and a second cylindrical ring-shaped piston section (12) with a second outer diameter (13), which is larger than the first outer diameter (11), and the second piston section (12) in the disengagement direction in front of the first piston section (10) is formed, wherein the central release piston chamber (6) is designed such that in a first operating position (28) of the central release piston (8) in the central release piston chamber (6) only the first piston section (10) is acted upon by the hydraulic fluid (7). and in a second operating position (14), which follows the first operating position (28) in the disengaging direction, the first piston section (10) and the second piston section (12) are acted upon by hydraulic fluid (7).

Description

The present invention relates to a central release mechanism, in particular for a hydraulic release system of a motor vehicle, comprising a central release housing with an annular central release piston space in which a central release piston is axially movably received by a hydraulic fluid which can be supplied to the central release piston space, the central release mechanism having at least one central release piston seal which holds the central release piston against the Central release piston chamber seals. The invention further relates to a hydraulic actuation device, a transmission device and an electrically operable axle drive train.

A clutch system for motor vehicles with conventional combustion drives has the function of coupling or uncoupling the driving engine side in a drive train of a vehicle in a switchable manner from the transmission side and thus enabling the transmission to change gears while driving and thereby keeping the driving engine at a preferred speed. / torque range.

With the increasing electrification of motor vehicles, clutch systems in fully electric or hybrid drive trains have also become known.

A drive train of a hybrid vehicle includes a combination of an internal combustion engine and an electric motor and enables - for example in metropolitan areas - purely electric operation with sufficient range and availability, especially for cross-country journeys. There is also the possibility of being driven simultaneously by the internal combustion engine and the electric motor in certain operating situations.

For the hybridization of conventional drive trains, so-called hybrid modules are known, which structurally combine the assemblies necessary for electrifying the drive train in one module. In addition to an electric machine, these assemblies also regularly include hydraulic clutch systems for engaging or disengaging the electrical machine in or out of the drive train.

Such clutch systems of hybrid vehicles, which are usually fully hydraulically operated, can be equipped with a central slave cylinder, which is often also referred to as a concentric slave cylinder (CSC). This can in particular consist of an annular hydraulic central release cylinder with an integrated release bearing, which is arranged centrally to the clutch shaft.

These central release units for a clutch system of a motor vehicle generally have a central release housing with an annular central release piston chamber, in which a central release piston is accommodated in an axially movable manner by means of a hydraulic fluid that can be supplied to the central release piston chamber. To seal the central release piston from the central release housing, such a central release mechanism has at least one central release piston seal, which must be fixed in the central release housing.

As a rule, the central release piston is subjected to force against its release direction by the actuated clutch system, so that when the hydraulic pressure within the central release piston chamber drops, the central release piston is moved into its engaged position by the clutch system and the corresponding clutch opens.

Torque vectoring modules have also become known in connection with the electrically operable axle drive trains in motor vehicles mentioned at the beginning. With the help of the “Torque Vectoring” function, it is possible to distribute the torque of a drive axle wheel-selective. Such torque vectoring modules usually include a mechanical differential that distributes the input torque equally to the two wheels of an axle. The speed of the wheels changes with the curve radius. The wheel on the inside of the curve turns slower than the wheel on the outside of the curve, which has to travel a greater distance. The wheel on the outside of the curve is braked slightly by the internal friction in the differential compared to the differential housing and the wheel on the inside of the curve is accelerated accordingly. As a result, there is a slightly higher torque on the wheel on the inside of the curve. This effect is also used by torque vectoring systems, which specifically accelerate or decelerate at least one of the two wheels.

Such differential gears with torque vectoring functionality can be controlled, for example, via brakes or clutches, which lock or brake gear stages of the differential gear in such a way that a continuous allocation of wheel speed and torque is possible, whereby yaw moments around the vertical axis can be generated in a targeted manner. Improvements in traction can also be achieved in general.

Since the installation space for electrically operated axle drive trains with a torque vectoring module in a vehicle is regularly limited, there is a continuing need for such axle drive trains to be as compact and as possible Adaptable to given installation space situations.

With such torque distribution devices, which were also initially referred to as torque vectoring modules, much higher axial forces are required to distribute the drive torque to the respective vehicle wheels to actuate the necessary brakes than, for example, with the conventional arrangement and actuation of a separating clutch in the drive train of a motor vehicle. This is due to the fact that the torque distribution device in the drive train is usually arranged after the transmission and not as in the conventional arrangement of a clutch between the engine and transmission. The higher axial forces result in comparatively large piston areas of the hydraulic slave cylinders (central release pistons), which are synonymous with large volume flows required. A central release mechanism according to the preamble of claim 1 is from the JP S55-72 924 A known. Further state of the art is in the DE 10 2021 111 772 A1 described.

It is the object of the invention to provide a central release mechanism which, with a compact structure, can provide the greatest possible axial force for actuating, for example, a multi-disc brake. It is also the object of the invention to realize an improved hydraulic actuation device, as well as an optimized transmission device and an electrically operable axle drive train.

This object is achieved by a central releaser, in particular for a hydraulic release system of a motor vehicle, comprising a central releaser housing with an annular central releaser piston space in which a central releaser piston is axially movably received by a hydraulic fluid that can be supplied to the central releaser piston space, the central releaser having at least one central releaser piston seal which counteracts the central releaser piston seals the central release piston chamber, wherein the central release piston is designed in a stepped manner and has a first cylindrical ring-shaped piston section with a first outer diameter and a second cylindrical ring-shaped piston section with a second outer diameter that is larger than the first outer diameter, and the second piston section is formed in front of the first piston section in the disengagement direction , wherein the central release piston chamber is designed such that in a first operating position of the central release piston in the central release piston chamber only the first piston section is acted upon by the hydraulic fluid and in a second operating position, which follows the first operating position in the release direction, the first piston section and the second piston section are acted upon by hydraulic fluid are applied.

This achieves the advantage that a compact central release mechanism with a high release force in the axial direction can be provided.

This is realized according to the invention by a concentric hydraulic slave cylinder in the form of a central releaser with two annular piston surfaces, which are hydraulically connected to one another, for example via overflow grooves arranged in the housing of the central releaser.

In a preferred embodiment of the invention, this connection can be closed and opened by means of a sliding band arranged in the central release piston. In this preferred embodiment, the invention takes advantage of the fact that a sliding band only slows down the volume flow of a hydraulic fluid and does not completely seal it.

First, the individual elements of the claimed subject matter of the invention are explained in the order in which they are mentioned in the claim sentence and particularly preferred embodiments of the subject matter of the invention are described below.

Central releaser

The central release mechanism according to the invention is preferably intended for use in a hydraulic release system. A hydraulic release system usually has a master cylinder that transmits the pressure generated on the master cylinder via a hydraulic pressure line to the slave cylinder, in this case a central slave cylinder. The hydraulic pressure can also be achieved in particular by means of a so-called Power packs are provided, which consist of a hydraulic pump and a hydraulic pressure accumulator that can be acted upon by the hydraulic pump. In this case, a pressure chamber of the slave cylinder can then also be pressurized hydraulically, for example by a master cylinder, which is controlled by a control unit by means of an electric motor, or by a hydraulic pump, possibly with the cooperation of a pressure accumulator. A so-called power pack can advantageously be used, which switches several pressure circuits via a particularly central hydraulic pump and corresponding valves.

In the present case, the slave cylinder is designed in particular as a central slave cylinder In the hydraulic release system, preferably by means of an axially displaceable piston and particularly preferably with the interposition of a clutch release bearing, transmits the hydraulic pressure to a lever system, which can be formed, for example, by a plate spring. The plate spring acts on a clutch pressure plate which is connected to a clutch housing in a rotationally fixed and axially displaceable manner and is clamped against a pressure plate which is firmly connected to the clutch housing. A clutch disc with a clutch lining is arranged between the pressure plate and the clutch pressure plate, which, depending on the tension between the pressure plate and the clutch pressure plate, form a frictional connection and close the friction clutch or open it when the frictional connection is removed.

The hydraulic clutch release system therefore particularly preferably actuates a friction clutch of a clutch system hydraulically by acting on the master cylinder. As explained, this can be done either by means of an actuator that is controlled by a control unit or by manual operation by the driver using a clutch pedal.

The central release mechanism can particularly preferably be used in a clutch system for motor vehicles. The clutch system can have the function of coupling or uncoupling the driving engine side in a drive train of a vehicle in a switchable manner from the transmission side and thus, for example, enabling the transmission to change gears while driving and thereby keeping the driving engine in a preferred speed/torque range to be able to operate, or to couple an electric motor or an internal combustion engine from or into a drive train.

For the purposes of this application, motor vehicles are land vehicles that are moved by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (passenger cars), trucks (lorries), mopeds, light vehicles, motorcycles, motor buses (KOM) or tractors. The central release mechanism is particularly preferably intended for use in a hybrid electric vehicle. A hybrid electric vehicle, also known as a hybrid electric vehicle (HEV), is an electric vehicle that is powered by at least one electric motor and another energy converter and draws energy from both its electrical storage (battery) and additional fuel.

A central release mechanism according to the invention has a central release mechanism housing. The function of the central release housing is to accommodate components of the central release unit, such as in particular the movable central release piston, and to protect them from external mechanical or chemical influences. Furthermore, the central clutch release housing has the function of allowing easy assembly and fixation of the central clutch release within the drive train. The central release housing can be designed in one piece or in several pieces. The central release housing can preferably be made of a plastic, a metallic material and/or a ceramic material. The central release piston chamber formed in the central release housing serves to accommodate and guide the central release piston, which is mounted in the central release housing for linear movement.

The central release mechanism according to the invention also has a central release piston. The central release piston has the function of converting hydraulic pressurization into a linear displacement of the central release piston, whereby this causes the clutch system to be able to be transferred from an engaged operating state to a disengaged operating state. The central releaser can have an annular central release piston or several central release pistons (multi-piston releaser).

Furthermore, the central release mechanism according to the invention has at least one central release piston seal. The central release piston seal seals the linearly movable central release piston from the central release housing housing the central release piston. The central release piston seal can in particular be designed as a sealing ring. It is particularly preferred that the central release piston seal is formed from an elastic, particularly preferably rubber-elastic material. The elastic material can preferably consist entirely or partially of an elastomer, the elastomers again preferably being selected from the group of vulcanizates of natural rubber and silicone rubber.

In a hydraulic release system of a motor vehicle, the hydraulic fluid has the function of transmitting energy in the form of pressure with as little loss as possible, for example within a clutch system of a vehicle. In addition to this main task, the hydraulic fluid can also provide lubrication and corrosion protection for the moving parts and the metal surfaces of the hydraulic release system. In addition, she can in particular also remove contamination (e.g. from abrasion), water and air as well as heat loss.

According to a further particularly preferred embodiment of the invention, it can be provided that the central release piston and/or the central release housing are/is formed from a plastic. This makes it possible, in particular, to achieve the effect that the central release mechanism can be manufactured cost-effectively and designed to be particularly weight-optimized.

Disc brake

A multi-disc brake has the function of creating a detachable, non-positive connection between an input shaft and an output shaft to support torque. For this purpose, the alternately arranged inner disks and outer disks of the disk pack can be brought into non-positive or frictional contact via axial displacement and compression via their respective friction linings by a coupling process, so that the inner disks move relative to the outer disks in a frictional manner around the common axis of rotation of the corresponding one Rotate the disk pack or are arranged in a rotationally fixed manner with a complete frictional connection to one another.

If, on the other hand, the inner disks and outer disks are pushed axially away from one another by a disengagement process, there is no longer any frictional contact between the inner disks and the outer disks, so that they can rotate freely against each other and consequently no torque or braking torque is transmitted between the inner disks and the outer disks.

In a possible embodiment of such a multi-disc brake, the clutch input shaft can be connected in a torsionally rigid manner to the outer disc carrier of the multi-disc clutch. By means of internal teeth on the outer disk carrier, all of the outer disks are then guided in an axially freely movable manner. The inner disks, which are also axially freely movable due to the teeth of the inner disk carrier, are then arranged alternately between the outer disks. This means that all inner plates are connected to the clutch output shaft in a torsion-resistant manner. When the multi-plate clutch is closed by operating the central clutch release, friction occurs between the outer and inner plates. The resulting frictional forces result in a flow of force from the outer disk carrier to the inner disk carrier, which enables torque transmission from the clutch input shaft to the clutch output shaft. When the central clutch release is not actuated, the inner disks and the outer disks separate, depending on the design, either by the action of a spring or - in the case of wet disk brakes - by the oil flow between the disks.

A multi-disc brake usually consists of at least two inner and/or two outer discs. The inner disks are preferably arranged in a rotationally fixed manner on an inner disk carrier and the outer disks are preferably arranged in a rotationally fixed manner on an outer disk carrier. The inner disk carrier is connected in particular to a clutch output shaft and the outer disk carrier is connected in particular to a clutch input shaft or vice versa.

The inner disks and outer disks form the disk pack of the disk brake. In the disk pack, a plurality of inner disks and outer disks are preferably arranged alternately with one another in the axial direction. The torque or braking torque that can be transmitted by the multi-disc brake between the inner discs and outer discs can be adjusted by the number and design of the inner discs and outer discs.

The inner disks have the function of transmitting a torque, in particular non-positively or frictionally, from the outer disks to the inner disk carrier. The inner slats can in particular be designed as circular disks. The inner disks can be non-rotatably connected to the inner disk carrier of the disk brake. It can also be provided that the inner disks can be displaced in the axial direction relative to the inner disk carrier, for example via a corresponding toothing, in order to establish the frictional connection with the outer disks.

The outer disks have the function of transmitting a torque, in particular non-positively or frictionally, from the inner disks to the outer disk carrier. The outer slats can in particular be designed as circular disks. The outer plates can be connected in a rotationally fixed manner to the outer plate carrier of the multi-plate clutch. It can also be provided that the outer disks can be displaced in the axial direction relative to the outer disk carrier, for example via a corresponding toothing, in order to establish the frictional connection with the inner disks. The outer disk carrier can be designed, for example, as an outer disk clutch basket.

The multi-disc brake can preferably comprise a spring. The spring has the task of moving the inner slats and the outer slats into a predefined position relative to one another using spring force move. This predefined position usually corresponds to a “normally open” or “normally closed” operating state of the multi-disc brake, which means that when the central release is not actuated, the inner discs and the outer discs are either pressed against each other or released by the spring.

The multi-disc brake is actuated by the central clutch release. The function of the central clutch release is to cause the multi-disc brake to brake. This braking process can in particular be the engagement and/or disengagement of the multi-disc brake. Since high forces can sometimes be necessary to engage or disengage the multi-disc brake, it can be provided in particular that the central release mechanism can be actuated by means of hydraulic auxiliary power support.

Furthermore, the multi-disc brake can also have a switching piston. The switching piston has the function of converting the engagement and disengagement processes specified by the central clutch into an axial displacement of the inner disks and/or the outer disks for the purpose of producing a frictional connection when engaging or releasing a frictional connection when disengaging the multi-disc brake.

According to an advantageous embodiment of the invention, it can be provided that the inner slats and/or the outer slats are designed as steel slats. According to a further preferred development of the invention, it can also be provided that the inner slats and/or the outer slats have a plug-in toothing.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the inner disks are accommodated in an inner disk carrier and/or the outer disks are accommodated in an outer disk carrier.

Drivetrain

An electric axle drive train of a motor vehicle includes an electric machine and a transmission arrangement, the electric machine and the transmission arrangement forming a structural unit.

In particular, it can be provided that the electric machine and the transmission arrangement are arranged in a common drive train housing. Alternatively, it would of course also be possible for the electric machine to have a motor housing and the gearbox to have a gearbox housing, with the structural unit then being able to be achieved by fixing the gearbox arrangement relative to the electric machine. This structural unit is sometimes also referred to as an e-axle.

The electric machine and the transmission arrangement can also be accommodated in a drive train housing. The drive train housing is at least intended to accommodate the electric machine and the transmission arrangement.

The drive train housing is preferably formed from a metallic material, particularly preferably from aluminum, gray cast iron or cast steel, in particular by means of a primary molding process such as casting or die casting. In principle, however, it would also be possible to form the drive train housing from a plastic.

The drive train housing can particularly preferably have a pot-like basic shape, so that the electric machine and the transmission can be inserted into the drive train housing via the open end face thereof.

An electrical machine is used to convert electrical energy into mechanical energy and/or vice versa, and usually comprises a stationary part called a stator, stand or armature and a part called a rotor or rotor and arranged to be movable relative to the stationary part.

In the case of electrical machines designed as rotary machines, a distinction is made in particular between radial flux machines and axial flux machines. A radial flux machine is characterized in that the magnetic field lines in the air gap formed between the rotor and stator extend in the radial direction, while in the case of an axial flux machine the magnetic field lines in the air gap formed between the rotor and stator extend in the axial direction.

In connection with the invention, the electrical machine can be designed as a radial or axial flux machine. In order to create an axially particularly compact axle drive train, axial flux machines are to be preferred.

The electric machine is intended in particular for use within an electrically operable drive train of a motor vehicle.

In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km/h, preferably greater than 80 km/h and in particular greater than 100 km/h can be achieved. Particularly preferred is the Electric motor has a power greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is further preferred that the electric machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, most preferably greater than 12,500 rpm

The transmission arrangement of the electric axle drive train can in particular be coupled to the electric machine, which is designed to generate a drive torque for the motor vehicle. The drive torque is particularly preferably a main drive torque, so that the motor vehicle is driven exclusively by the drive torque.

The gear arrangement can have a differential gear. A differential gear is a planetary gear with one input and two outputs. It usually has the function of driving two vehicle wheels of a motor vehicle so that they can turn at different speeds in curves, but with the same propulsive force.

The electrically operable axle drive train also has a torque vectoring module, whereby the torque of an electrically operable axle drive train can be distributed wheel-selective. This can be achieved, for example, by using an electromechanically driven, three-stage planetary gear, the so-called superposition gear. For the purposes of this application, a torque vectoring module is also understood to mean a torque distribution device.

One or both of the clutch arrangements can also be configured as a brake, in which case the inner disks or the outer disks of the disk pack of the respective clutch arrangement are mounted in a rotationally fixed manner relative to the rotor, for example on a housing component.

Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically sensible manner and can define further embodiments of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, with further preferred embodiments of the invention being presented.

According to an advantageous embodiment of the invention, it can be provided that the central release piston chamber has a first annular space and a second annular space adjacent in the release direction of the central release piston, the first piston section being guided in the first annular space and the second piston section being guided in the second annular space. According to a further preferred development of the invention, it can also be provided that the second piston section carries the central release piston seal.

Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that a cylindrical ring-shaped overflow groove is formed in the disengagement direction of the central release piston between the first annular space and the second annular space, which hydraulically connects the first annular space with the second annular space in the second operating position of the central release piston.

According to a further particularly preferred embodiment of the invention, it can be provided that a circumferential groove is formed on the first piston section, into which a sliding band is accommodated, which in the first operating position of the central release piston rests against the inner lateral surface of the first annular space, in particular with play, and in which second operating position is detached from this.

The object of the invention can also be achieved by a hydraulic actuation device comprising a central release mechanism according to one of claims 1 to 3, wherein the central release piston is coupled to a multi-disc brake with the interposition of a release bearing. In a likewise preferred embodiment variant of the invention, it can also be provided that the central release piston has an axial offset path S1 between the fully engaged operating position and the second operating position, which is selected so that it corresponds to the maximum clearance in the wear state of the multi-disc brake. It can also be advantageous to further develop the invention in such a way that the central release piston is subjected to spring force against its release direction by a preload spring.

The object of the invention is further achieved by a transmission device comprising a torque vectoring unit with a hydraulic actuation device according to one of claims 4 to 6 for locking and releasing at least one transmission element within the torque vectoring unit.

Finally, the object of the invention can also be achieved by an electrically operable axle drive train of a motor vehicle comprising an electric machine and a transmission device according to claim 9 coupled to the electric machine.

The invention will be explained in more detail below using figures without restricting the general idea of the invention.

• 1 ein Kraftfahrzeug mit einem elektrischen Achsantriebsstrang in einer schematischen Blockschaltansicht,
• 2 einen Zentralausrücker in einer vollständig eingerückten Betriebsstellung in einer Axialschnittansicht,
• 3 einen Zentralausrücker in einer ersten Betriebsstellung in einer Axialschnittansicht,
• 4 einen Zentralausrücker in einer zweiten Betriebsstellung in einer Axialschnittansicht,
• 5 eine Aktuierungsvorrichtung mit einem Zentralausrücker, einem Ausrücklager und einer Lamellenbremse in einer Axialschnittansicht,
• 6 ein Kraft-Weg-Diagramm des Zentralausrückers.

It shows:

• 1 a motor vehicle with an electric axle drive train in a schematic block diagram,
• 2 a central clutch release in a fully engaged operating position in an axial section view,
• 3 a central release mechanism in a first operating position in an axial sectional view,
• 4 a central release mechanism in a second operating position in an axial section view,
• 5 an actuation device with a central release, a release bearing and a multi-disc brake in an axial sectional view,
• 6 a force-displacement diagram of the central release mechanism.

The 1 shows a central release mechanism 1 of a hydraulic actuation device 19 of a motor vehicle 4. The motor vehicle 4 is driven on a vehicle axle by an electrically operable axle drive train 26, which has an electric machine 29 and a transmission device 25 coupled to the electric machine 29. The transmission device 25 includes a torque vectoring module 23 with a hydraulic actuation device 19 for locking and releasing at least one transmission element within the torque vectoring module 23.

2 shows the one from the 1 well-known central release mechanism 1 in a detailed representation. It can be seen that the central releaser 1 comprises a central releaser housing 5 with an annular central releaser piston space 6, in which a central releaser piston 8 is accommodated in an axially movable manner by a hydraulic fluid 7 that can be supplied to the central releaser piston space 6. For sealing and building up pressure within the central release piston chamber 6, the central release piston 1 has two central release piston seals 9, which seal the central release piston 8 against the central release piston chamber 6. In the example shown, the central release piston seals 9 are accommodated in grooves provided in the central release piston 8 and are accordingly displaced relative to the central release housing 5 when the central release piston 8 is disengaged. Deviating from the embodiment shown, it would of course also be possible in principle to fix the central release piston seals 9 in the central release housing 5.

In the exemplary embodiment 2-4 The central release piston seals 9 are designed as sealing rings.

How to use the 1-4 can also be clearly seen, the central release piston 8 is designed in a stepped manner and has a first cylindrical ring-shaped piston section 10 with a first outer diameter 11 and a second cylindrical ring-shaped piston section 12 with a second outer diameter 13, which is larger than the first outer diameter 11. The second piston section 12 ( right) is formed in the disengagement direction in front of the first piston section 10 (left). The second piston section 12 carries the central release piston seals 9.

The central release piston chamber 6 is now designed such that in a first operating position 28 of the central release piston 8 in the central release piston chamber 6 only the first piston section 10 is acted upon by the hydraulic fluid 7. This operating position is in the 2 and the 3 shown, where in the 2 the central release piston 8 is shown in its fully engaged operating position.

When disengaging, the central release piston 8 can be moved into a second operating position 14, which follows the first operating position 28 in the disengaging direction, in which the first piston section 10 and the second piston section 12 are acted upon by hydraulic fluid 7, which is in the 4 you can see.

The central release piston chamber 6 has a first annular space 24 and a second annular space 15 adjacent in the release direction of the central release piston 8, the first piston section 10 being guided in the first annular space 24 and the second piston section 12 being guided in the second annular space 15. In other words, the annular spaces 15,24 are geometrically adapted to the stepped central release piston 8.

In the disengagement direction of the central release piston 8, a cylindrical ring-shaped overflow groove 16 is formed between the first annular space 24 and the second annular space 15, which hydraulically connects the first annular space 24 to the second annular space 15 in the second operating position 14 of the central release piston 8, as in the 5 is shown.

A circumferential groove 17 is formed on the first piston section 10, into which a sliding band 18 is accommodated, which rests with play on the inner lateral surface of the first annular space 24 in the first operating position 28 of the central release piston 8 and in the second operating position 14 of this is solved, which is clear from a synopsis of the 3-4 can be understood.

As an alternative to a cylindrical ring-shaped overflow groove 16, the overflow groove 16 can also be designed as a hydraulic channel extending in the axial direction. Several of these overflow grooves 16, designed as axial hydraulic channels, can also be provided in the central release mechanism 1, distributed over the circumference. What is crucial is that the overflow groove 16 enables a hydraulic connection between the first annular space 24 and the second annular space 15 from a predefined operating position of the central release piston 8, so that hydraulic pressure can also be built up in the second annular space 15.

In the 5 a hydraulic actuation device 19 is shown, comprising a central clutch release 1, as shown in the 2-4 is known. The central release piston 8 is coupled to a multi-disc brake 21 with the interposition of a release bearing 20. The release bearing 20 is designed in an angular contact ball bearing design.

The central release piston 8 has an axial offset path S1 between the fully engaged operating position and the second operating position 14, which is selected so that it corresponds to the maximum clearance when the multi-disc brake 21 is worn.

The central release piston 8 is spring-loaded against its release direction by a preload spring 22, so that in the event of a hydraulic pressure drop within the central release piston chamber 6, the central release 8 is moved into its fully engaged operating position by the preload spring 22 under spring force.

The release bearing 20 is connected to the central release piston 8, which in turn is connected to the pressure pot 27. The pressure pot 27 transmits the axial force from the central clutch release 1 to the disk pack of the disk brake 21.

The ones from the 1 known transmission device 25 includes a torque vectoring module 23 with the hydraulic actuation device 19, as shown in the 5 is shown, for locking and releasing at least one gear element within the torque vectoring module 23. In the unpressurized, unactuated state, the central release piston 8 is returned to the fully engaged starting position by means of one or more preload springs 22 in order to open the clearances, so that the Torque vectoring module 23 does not transmit any torque via the multi-disc brake 21.

The torque vectoring module 23 (which can also be referred to as a torque distribution device) transmits, for example, via the wet multi-disc brake 21, depending on the applied axial force, the input torque and input speed to the output torques and output speeds for the left and right wheels of an axle of the motor vehicle 4.

What is characteristic of the characteristic curve of a torque vectoring module 23 based on wet multi-disc brakes 21 is that a relatively large distance must be traveled with a relatively low axial force in order to close the clearance. After closing the clearance in the working area, relatively little distance is traveled with a relatively high axial force. In the 6 the characteristic course of the axial force F_ax over the piston travel s for such a wet multi-disc brake 21 is shown.

In the unactuated state (S = 0), as in the 5 can be seen, is the overflow groove 16 or are the overflow grooves 16 completely closed by a sliding band 18 arranged in the central release piston 8 in the area of the first piston section 12. At the beginning of the actuation, the sliding band 18 generates a dynamic pressure, which ensures that the hydraulic pressure initially only acts on the piston surface of the first piston section 12 and thus generates an axial force and an axial movement of the central release piston 8 in the disengagement direction (here to the right).

The hydraulic translation U1 results from the front piston surface of the first piston section 12 through the piston surface of the central release piston 8. Here, the hydraulic ratio U1 is selected so that the ratio is as low as possible, i.e. that as much piston travel as possible results from the hydraulic volume made available by the central release piston 8 for actuation.

The piston travel S1 is designed so that it corresponds to the maximum clearance when the disk pack of the disk brake 21 is worn. From the moment the piston travel is greater than S1, the sliding band 18 releases the overflow groove(s) 16, which is also the case 4 is shown.

The hydraulic fluid 7 now also acts on the front piston surface of the second piston section 12. The hydraulic translation U2 results from the piston surface of the second piston section 12 through the front piston surface of the central release piston 8. Here, U2 is selected so that the translation makes it possible to use the hydraulic volume made available by the central release piston 8 for actuation and hydraulic pressure to generate the required axial force.

If the axial force is to be reduced, the hydraulic pressure acting on the central release piston 8 is reduced. As a result, the central release piston 8 is then moved in the direction of the starting position by the preload springs 22. During this displacement movement, the hydraulic surface of the second piston section 12 is initially active and the hydraulic fluid 7 can shift in the engagement direction via the overflow groove(s) 16. From the piston position S2, the sliding band 18 closes the overflow groove(s) 16. A hydraulic pressure is now generated by the preload springs 22 via the front piston surface of the second piston section 12, which slowly shifts the hydraulic fluid 7 in the engagement direction. Here, the embodiment shown takes advantage of the fact that the sliding band 18 does not seal the volume flow of the hydraulic fluid 7, but only slows it down and thus also functions as a diaphragm in the hydraulic sense.

During the entire actuation movement of the central release piston 8, the sliding band 18 is constantly in the guide formed by the inner lateral surface of the first annular space 24.

The terms “radial”, “axial”, “tangential” and “circumferential direction” used in this application always refer to the axis of rotational symmetry of the central release piston. The terms “left”, “right”, “top”, “bottom”, “above” and “below” only serve to clarify which areas of the illustrations are currently being described in the text. The later embodiment of the invention can also be arranged differently. Furthermore, the invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be viewed as limiting but rather as illustrative. The following patent claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of other features. If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish two similar features without establishing a ranking.

Reference symbol list

1

Central releaser

4

motor vehicle

5

Central release housing

6

Central release piston chamber

7

Hydraulic fluid

8th

Central release piston

9

Central release piston seal

10

Piston section

11

outer diameter

12

Piston section

13

outer diameter

14

Operating position

15

Annular space

16

overflow groove

17

Nut

18

Sliding tape

19

Actuator device

20

release bearing

21

Disc brake

22

Preload spring

23

Torque vectoring module

24

Annular space

25

Gear device

26

Axle drive train

27

pressure pot

28

Operating position

29

electric machine

Claims (8)

Central releaser (1), in particular for a hydraulic release system of a motor vehicle (4), comprising a central releaser housing (5) with an annular central releaser piston space (6) in which a central releaser piston (8) can be moved axially through a hydraulic fluid (7) which can be supplied to the central releaser piston space (6). is accommodated, wherein the central release piston (1) has at least one central release piston seal (9) which seals the central release piston (8) against the central release piston chamber (6), the central release piston (8) being designed in a stepped manner and a first cylindrical ring-shaped piston section (10) with a first outer diameter (11) and a second cylindrical ring-shaped piston section (12) with a second outer diameter (13) which is larger than the first outer diameter (11), and the second piston section (12) is formed in front of the first piston section (10) in the disengagement direction is, whereby the central release piston chamber (6) looks like this is guided that in a first operating position (28) of the central release piston (8) in the central release piston chamber (6) only the first piston section (10) is acted upon by the hydraulic fluid (7) and in a second operating position (14), that of the first operating position (28) follows in the release direction, the first piston section (10) and the second piston section (12) are acted upon by hydraulic fluid (7), characterized in that the central release piston chamber (6) has a first annular space (24) and one in the release direction of the central release piston ( 8) has adjacent second annular space (15), wherein the first piston section (10) is guided in the first annular space (24) and the second piston section (12) in the second annular space (15) and that in the release direction of the central release piston (8) between a cylindrical ring-shaped overflow groove (16) is formed in the first annular space (24) and the second annular space (15), which hydraulically connects the first annular space (24) to the second annular space (15) in the second operating position (14) of the central release piston (8). . Central slave cylinder (1). Claim 1 , characterized in that the second piston section (12) carries the central release piston seal (9). Central release (1) according to one of the Claims 1 or 2 , characterized in that a circumferential groove (17) is formed on the first piston section (10), into which a sliding band (18) is accommodated, which in the first operating position (28) of the central release piston (8) on the inner lateral surface of the first annular space (24) in particular with play and is released from it in the second operating position (14). Hydraulic actuation device (19) comprising a central clutch release (1) according to one of Claims 1 until 3 , whereby the central release piston (8) is coupled to a multi-disc brake (21) with the interposition of a release bearing (20). Hydraulic actuation device (19) after Claim 4 , characterized in that the central release piston (8) has an axial offset path S1 between the fully engaged operating position and the second operating position (14), which is selected so that it corresponds to the maximum clearance when the multi-disc brake (21) is worn. Hydraulic actuation device (19) after Claim 4 or 5 , characterized in that the central release piston (8) is subjected to spring force against its release direction by a preload spring (22). Transmission device (25) comprising a torque vectoring module (23) with a hydraulic actuation device (19) according to one of Claims 4 until 6 for locking and releasing at least one gear element within the torque vectoring module (23). Electrically operable axle drive train (26) of a motor vehicle (4) comprising an electric machine (29) and a transmission device (25) coupled to the electric machine (29). Claim 7 .

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