WO2008009546A1

WO2008009546A1 - Clutch actuator for automatically actuating a friction clutch

Info

Publication number: WO2008009546A1
Application number: PCT/EP2007/056548
Authority: WO
Inventors: Martin Miller; Kai BORNTRÄGER; Karl-Hermann Ketteler
Original assignee: Zf Friedrichshafen Ag
Priority date: 2006-07-15
Filing date: 2007-06-29
Publication date: 2008-01-24
Also published as: DE102006032915A1

Abstract

The invention relates to a clutch actuator (1) for the automatic actuation of a vehicle friction clutch (2) and to a method for operating the same, said actuator consisting of a controllable pneumatic cylinder (3) with a piston (5) that can be displaced in a cylinder housing (4) and that divides the pneumatic cylinder (3) into a master chamber (6) and a working pressure chamber (7). The working pressure chamber (7) can be connected to a compressed air source (14) or a ventilation device by means of a switchable valve assembly (13). The aim of the invention is to prevent uncontrolled engagement operations of the clutch actuator, for example when an engaged position or a continuous slip operation position of the vehicle friction clutch (2) is set, and to permit an exact and comparatively quiet actuation of the clutch actuator (1). To achieve this, according to the invention, the piston (5) of the pneumatic cylinder (3) has a piston rod (17) on the pressure chamber side, said rod being axially driven by an electric drive motor (M) using a worm gear (18).

Description

Clutch actuator for the automatic actuation of a friction clutch

The invention relates to a coupling divider according to the preamble of patent claim 1 and a method for controlling a clutch actuator according to the preamble of patent claim 9.

In automated transmissions with pneumatically or hydraulically actuated clutch, so-called stick-slip effects can occur in the clutch actuation device for various reasons, for example due to wear, jamming, contamination in bearings or due to other influences. As is known, the stick-slip effect is understood to mean the jerking of solids moved against one another. The surface parts of the clutch actuating device, which are in frictional relationship with each other, exert a rapid sequence of movements of adhesion, distortion, separation and slipping.

In an automated manual transmission, it may happen, for example when the vehicle is stationary, that teeth of a synchronization device of the transmission are in a tooth-on-tooth position. In order to enable this dissolution and to enable a mechanical coupling of a toothed wheel to a gear shaft, it is known to close the starting clutch, which until then has been open against the force of a return spring, until it can transmit a certain torque in the so-called driving state or slip mode. As a result, the teeth located in the tooth-on-tooth position are rotated against each other, so that, for example, a sliding sleeve can engage in a toothing of a toothed wheel. When closing the starting clutch from the open state toward the eyes lupf position may occur as a result of the aforementioned influences on the size of the hysteresis in the transmission of the actuating force to an uncontrollable engagement in the clutch from overcome hysteresis, in which the clutch more than desired as well is closed suddenly, which will be discussed in more detail below.

In order to move from the open state to the slip position or clutch state of the clutch, an operating force applied by a pressure-driven clutch actuator against the restoring force of the clutch return spring (Belleville spring) has to be reduced, such as in a pneumatic clutch actuator such as commercial vehicles finds, characterized in that the actuating cylinder is vented by the file.

If the current difference in force between the force of the clutch return spring and the opposing force of the pneumatic clutch actuator is insufficient to cause an actuator of the clutch actuator to move in the closing direction by overcoming static friction, the effective closing force must be increased by further venting the actuating cylinder of the pneumatic clutch actuator , When Los breaking from the static friction, the counter-force of the pneumatic clutch actuator is then no longer sufficient to prevent engagement of the clutch on the slip or driving point. If the time from breakaway to reaching the pickup point is no longer sufficient for counteracting by venting the actuating cylinder, the driving point is exceeded and an undesirably wide and jerky closing of the clutch occurs. The unpublished patent application DE 10 2004 039 271 already deals with the problem of stick-slip effects in hydrostatic transmissions and proposes a method for determining such parameters on a hydrostatic transmission which is simple for the accurate positioning of a force-loaded piston acting plunger-cylinder unit of the transmission are necessary. These parameters include according to this document, the cylinder-Snnendruck, any stick-slip effects of the plunger-cylinder unit and / or a hysteresis possibly influencing the hydrostatic transmission.

The known method works by using a position measuring system and an adjustable ventilation valve or a throttle and an adjustable vent valve or a throttle, in addition, this method is based on a specific applied supply pressure or input pressure at the throttle and a defined outlet pressure of the throttle, wherein by opening both or one of the two throttles, the piston is displaced from a first to a second position, and wherein for the latter position, the said parameters are determined.

In a further method step according to DE 10 2004 039 271, in the selected second position of the piston at defined open throttles or during defined further open one of the two already open throttles or at defined open one of the two previously closed throttles by a measuring means at least one state value of the transmission detected, and calculated from this at least one detected Zusfandswert the searched parameters or closed on this. The clutch actuation takes place there by particularly finely metered closing and opening of the two hydraulic throttles or hydraulic valves and by particularly accurate detection of hydraulic pressures and the piston position. From DE 30 28 251 A1 also a generic clutch actuator is known, the pneumatic actuating cylinder is connected on the pressure side via a switchable valve arrangement either with a compressed air source or with a venting device, wherein in the switched on when engaging the clutch compressed air path, a throttle arrangement with depending on the Position of the actuator and / or the engine speed controllable air flow is switched. By means of the valve arrangement, which includes primarily two 2/2-way valves, the piston of the Kupplungsstel- lers and an associated with him actuator can move pneumatically, so that the clutch can be opened or closed. Suggestions for solving the problem of the stick-slip effect can not be found in this document.

(DE 697 28 009 12 ^"EP 0834669 81} is finally a couplings lung controller for an automated vehicle clutch is known which is pneumatically and hydraulically or electromotively operable by located in an actuator cylinder of the clutch actuator, a first piston, which on This first piston is axially displaced in one direction by the supply of compressed air to the actuating cylinder for opening the clutch, and spring-loaded in venting the actuating cylinder for closing the clutch moves in the opposite direction Further adjusting means, which is axially movable there independently of the first piston and can be brought to the front side with the first piston for abutment The position of this further actuating means is adjustable by a hydraulic pressure in the same actuating cylinder, which by an electric motor with egg A ball screw drive is generated in a hydraulic master cylinder. According to an alternative embodiment, the further actuating means of the electric motor ball screw combination is directly mechanically driven. The advantage of this rather complex clutch actuation device is the rapid, virtually sudden opening of the clutch when the working pressure chamber of the actuation cylinder is pressurized with compressed air. In addition, the clutch actuation position at which the clutch engagement begins can be set quite accurately by the hydraulic or electromotive positioning of said further actuating means. Subsequently or at the same time, the actuating cylinder is vented by compressed air, so that the first piston moves in the direction of the further actuating means until they touch the front side.

A disadvantage of the known from DE 697 28 009 72 Kupplungsstel- ler is that the first piston can be subject to the initially described stick-slip effect in its movement in the clutch closing direction, in which the actuation ungsaktuatorik clamps due to wear, so to speak. When breakage of this actuator, the first piston then bounced abruptly on the already displaced hydraulically or electromotively actuated actuating means in the actuating cylinder, which is adversely associated with a Aufschlaggeräusch and at least in hydraulic actuation of this actuating means leads to undesirable pressure oscillations in the actuation system

Against this background, the invention has the object to improve a clutch plate of the last-mentioned type so that with this uncontrollable engagement of a clutch, for example, caused by the said stick-slip effect, do not occur. In addition, the coupling divider should be constructed comparatively simple and inexpensive. The invention is also intended to specify a method for operating such a clutch actuator, with the stick-slip effect avoidable bar and a comparatively quiet operation of the clutch actuator is possible. The solution to this problem arises for a clutch actuator from the features of the main claim and in terms of a method for operating the clutch actuator from the independent method claim. Advantageous embodiments and further developments of the invention are the respective associated subclaims removed.

The invention is based on the finding that the stated object can be achieved in a surprisingly simple manner by the fact that said stick-slip effect can be prevented by a decoupling of Wegpositionsvorgabe and force control of the clutch actuator. This particular fact that the only piston in the working pressure chamber of the associated pneumatic cylinder is not only operated pressure medium controlled, but is also positively and driven connected via a worm gear with a drive motor. This allows exact positioning of the piston of the pneumatic cylinder. In particular, pressure and force peaks, which are characteristic of the occurrence of stick-slip effects, are absorbed by the advantageously self-locking worm gear, the drive motor is designed to be electrically operable

This results in surprising effects and advantages. The coupling divider can be controlled by the combination of pressure and path control finer than usual devices and can thereby better adapt to different states of the clutch. By using only an axially movable adjusting element in the actuating cylinder unfavorable impact noise and force peaks in the operating system deviating from the clutch plate of DE 697 28 009 12 avoided. In addition, the clutch actuator is comparatively simple and inexpensive

According to the features of the main claim, the invention is based on a clutch plate for the automatic actuation of a motor vehicle clutch, consisting of a controllable pneumatic cylinder with a piston displaceable in a cylinder housing, softer subdivided the pneumatic cylinder into a sender chamber and a working pressure chamber, wherein the working pressure chamber by means of a switchable valve assembly with a compressed air source or with a Entluftungseinrichtung is connectable. To achieve the object is provided that the piston of the pneumatic cylinder pressure chamber side has a piston rod which is axially driven via a worm gear by an electric drive motor.

Due to the combination of the pressure medium actuation of the single piston of the clutch actuator and the travel control by the electric motor with the worm gear can advantageously be approached exactly, quickly and comparatively noiseless, for example, that clutch actuation position, in which the clutch for dissolving an existing in a drive technically downstream transmission tooth-up To set the tooth position. This is especially advantageous for the safety of vehicle operation if this tooth-on-tooth position of shiftable transmission toothing is to be eliminated when the starting clutch is initially open, the starting gear engaged and the vehicle stationary.

In this coupling divider, the worm gear is preferably designed to be self-locking in a manner known per se, so that no separate braking or locking means are provided with which otherwise the drive motor of the device driving forces of the diaphragm spring or disc spring of the clutch would have to be kept away from this , In particular, unintentional movements of the piston rod driven by the electric drive motor can thus be prevented.

With regard to the valve assembly is provided that this one connected to a compressed air source valve and one with an exhaust chamber or with Having the ambient air connected valve. At least one of these valves is designed as a 2/2 way valve.

For controlling the components of the valve arrangement and the electric drive motor, an electronic firing device is provided which is designed, for example, as a gearbox control device. The components of the valve arrangement mentioned are connected to the control device via control lines.

In this coupling divider, it is also preferable for the piston rod to be in operative connection with a displacement measuring sensor, and for this displacement measuring sensor to be connected to the electronic control device via a sensor line,

In addition, it can be provided that a speed sensor is arranged on the drive motor or on the worm gear, which can forward speed signals to the electronic control device, in this is determined from the speed signals with knowledge of the translation of the worm gear of the travel covered by the piston travel.

The invention also relates to a method for controlling a clutch actuator with at least some of the mentioned features, in which the single piston is acted upon by compressed air for opening the motor vehicle friction clutch and a corresponding working pressure chamber is vented to close the motor vehicle friction clutch. According to the method, it is provided that in a first method step for adjusting a clutch actuation position compressed air is passed into the working pressure chamber or vented from this, and that at the latest after filling or venting the Arbeifsdruckraumes in a second process step, the electric drive motor is operated until the piston the desired as long is _operated: until the piston has reached the desired clutch actuation position,

According to the method can also be provided that the achievement of the desired clutch actuation position by means of said Wegmesssensors or by determining the actuation time of the drive motor and / or by detecting rotational speed signals of a speed sensor on the drive motor or on the worm gear is determined.

Preferably, the method is used according to the invention for the exact control of a driving position or a slip operating position of the motor vehicle friction clutch, so that it does not come to unwanted torque peaks in the drive train of a motor vehicle in the elimination of a Zahnauf-tooth position of gears in an automated transmission.

To clarify the invention, the description is accompanied by a drawing of an embodiment. In this, the single figure shows a clutch plate 1 according to the invention, which acts on an only indicated motor vehicle friction clutch 2. This motor vehicle friction clutch 2 is arranged in terms of drive technology between a drive motor and a manual transmission, both of which are not shown separately for a better overview.

According to this simplified illustration, the clutch actuator 1 initially consists of an actuator in the form of a pneumatic cylinder 3 which has a housing 4 in which the single piston 5 is arranged to be axially displaceable. The piston 5 divides the pneumatic cylinder 3 in a transmitter chamber 6 and in a working pressure chamber 7. The piston 5 is connected on the side of the transmitter chamber 6 in a conventional manner with an actuator 8, In the figure, the closed position of the motor vehicle friction clutch 2 is shown, in which the plate spring 10 presses friction elements 11 and 12 of the motor vehicle friction clutch 2 against each other.

The pneumatic cylinder 3 is connected with its working pressure chamber 7 to a valve assembly 13. This valve arrangement 13 has a valve 15 connected to a compressed air source 14 and a valve 16 connected to the ambient air or an exhaust air space, wherein both valves 15 and 16 are designed as electromagnetic 2/2-way valves. The valves 15, 16 are connected to an electronic control device E, for example in the form of a transmission control device, This electronic Steuerungseinrichfung E controls the feeding of compressed air via the valve 15 in the working pressure chamber 7 and the discharge of compressed air from the working pressure chamber 7 via the valve sixteenth ,

The piston 5 is on the side of the working pressure chamber 7 with a second piston rod 17 in connection. This piston rod 17 is positively and drivably connected to an only indicated worm gear 18, which in turn is driven by an electric drive motor M. The worm gear 18 is dimensioned so that in motor operation, a motor rotation is converted into a linear movement of the piston rod 17. However, the drive motor M does not provide large Betäfigungskräfte for the axial displacement of the piston 5 and the actuator 8 available. It essentially serves to allow a maximum actuation path of the piston 5. The necessary for the completion of this travel actuating forces are applied mainly by the fed into the working pressure chamber 7 compressed air and in the opposite direction by the plate spring 10 of the clutch 2. The drive motor M is connected to the electronic firing device E. A also connected to the electronic control device E Wegmesssensor W detects the axial position or the axial displacement of the piston rod 17 in a conventional manner.

To disengage the KraftfahrΣeugreibungskupplung 2 of the drive motor E and the valve 15, which is connected to the working pressure chamber 7. energized. At the same time, the piston rod 17 is displaced axially to the left by the drive motor M and the self-locking worm gear 18 against the force of a spring 19 arranged in the working pressure chamber 7 in the FIGURE. If the force in the working pressure chamber 7 of the pneumatic cylinder 3 is greater than the coupling force of the disc spring 10 by the inflowing compressed air, the clutch 2 is opened to an axial position predetermined by the rotational movement of the drive motor M.

The worm gear 18 is dimensioned so that in the case in which the piston rod 5 due to the forces acting on them of the two springs 10 and 19 tries to drive via the worm gear, the drive shaft of the drive motor M, enters a self-locking. This means that an adjusting movement of the piston rod 17 or the piston 5 is only possible if the drive motor M drives the worm gear 18 in one of the two directions of rotation. As mentioned, the pneumatic pressure in the working pressure chamber 7 or the restoring forces of the two springs 10, 19 largely takes over the necessary actuating forces.

The closing of the clutch 2 takes place by energizing the valve 16, which is connected to the ambient air, as well as by energizing the drive motor M to specify the engagement position to be achieved and the input. back speed. The piston rod 17 now moves in the reverse axial direction in the figure to the right, so that the clutch 2 is brought into a favorable for eliminating a tooth-on-tooth position of gear teeth slip position.

If, when closing the clutch 2, stick-slip effects in the actuation actuator system that require an increased engagement force remain, the valve 16 remains open until the sum of the current static friction force and the counterforce of the pneumatic cylinder 3 by reducing the pressure in the working pressure chamber 7 is smaller than the sum of the closing force of the plate spring 10 and the closing force of the worm gear drive motor combination.

The movement of the piston 5 then takes place to a position which is predetermined by the operation of the drive motor M and the worm gear 18. Exceeding a predetermined closing speed or the predetermined closing path beyond the desired clutch closing position beyond, for example, the slip position, is advantageously prevented by the design of the Kupplungsstel- lers 1.

The detection of the actuating position of the actuator can be effected by means of the illustrated displacement sensor W or by other sensors. Likewise, the rotational speed and direction of rotation of the drive motor M can be used to sense actuation positions and states of the pneumatic cylinder 3 and the clutch 2. Thus, a statement about the axial position of the piston rod 17 can be made by the number of engine revolutions and the ratio of the worm gear. REFERENCE CHARACTERS

1 coupling divider

2 Automotive friction clutch, clutch

3 pneumatic cylinders

4 housing

5 pistons

6 encoder room

7 working pressure room

8 actuator

9 release bearing

10 plate spring

11 friction element

12 friction element

13 valve arrangement

14 compressed air source

15 valve

16 valve

17 piston rod

18 worm gears

19 spring

E electronic control device M electric drive motor W travel sensor

Claims

claims

1. clutch divider (1) for automatically actuating a friction clutch (2), consisting of a controllable Pneumatikzyiinder (3) with a in a cylinder housing (4) displaceable piston (5), which the pneumatic cylinder (3) in a transmitter chamber (6) and a working pressure chamber (7), wherein the working pressure chamber {7} by means of a reversible valve assembly (13) with a compressed air source (14) or with a venting device is connected, characterized in that the piston (5) of the pneumatic cylinder (3) the pressure chamber side, a piston rod (17), which is axially driven by a worm gear (18) by an electric drive motor (M)

2. Clutch actuator according to claim 1, characterized in that the worm gear (18) is self-locking

3. Clutch actuator according to claim 1, characterized in that the worm gear (18) for preventing unwanted movements of the electric drive motor (M) driven piston catcher (17) is self-locking.

4. Clutch actuator according to one of claims 1 to 3, characterized in that the valve arrangement (13) with a compressed air source (14) connected to the valve (15) and connected to an exhaust chamber valve (16).

5. Clutch actuator according to claim 4, characterized in that at least one valve (15, 16) is designed as a 2/2-way valve.

6. clutch actuator at least according to claim 1, characterized in that the components of the valve assembly (13) and the drive motor (M) with an electronic control device (E) are connected.

7. Coupling divider at least according to claim 1, characterized in that the piston rod (17) with a Wegmesssensor (W) is in operative connection, wherein the Wegmesssensor (W) with the electronic control device (E) is connected.

8. Clutch actuator according to at least one of claims 1 to 7, characterized in that on the drive motor (M) or on the worm gear (18) a speed sensor is arranged, which can forward speed signals to the electronic control device (E).

9. A method for controlling a clutch actuator (1) having the features of at least one of the preceding claims, wherein the piston (5) for opening the Kraftfahrzeugreibkupplung (2) acted upon with compressed air and for closing the Kraftfahrzeugreibkupplung (2) a related working pressure space (7 ) is vented, characterized in that in a first process step for setting a Kupplungsbetäti- supply position compressed air in the working pressure chamber (7) passed or vented from this, and that at the latest after filling or venting the working pressure chamber (7) in a second process step of the electric Drive motor (M) is operated until the piston (5) has reached the desired clutch actuation position.

10. The method according to claim 9, characterized in that the achievement of the desired clutch actuation position by means of a displacement sensor (W) is detected.

11. The method according to claim 9, characterized in that the achievement of the desired clutch actuation position by detecting the actuation time of the drive motor (M) and / or by counting the pulses of a speed sensor on the drive motor (M) or on the worm gear (18) is detected.

12. The method according to at least one of claims 9 to 11, characterized in that this is used to control a driving position or, a slip operating position of the motor vehicle friction clutch (2).

13. The method according to claim 12, characterized in that this is used to eliminate a tooth-on-tooth position of gears in an automated manual transmission.