WO2004074704A1 - Method for controlling the operation of a clutch of a motor vehicle - Google Patents

Abstract

The invention relates to a method for controlling the operation of a clutch (1) of a motor vehicle comprising an automatic gearbox, especially a twin clutch of an automatic twin-clutch gearbox, whereby the clutch elements are cooled during the operation of the clutch by means of a coolant (2), and the thermal load on the clutch (1) is determined during the operation of the same. The aim of the invention is to improve and economically optimise one such method. To this end, the current temperature of the coolant (2) leaving the clutch (1) is measured, a defined driving characteristic (3, 4 or 5) is selected from a plurality of stored driving characteristics (3, 4, 5) on the basis of the temperature measured, and the operation of the clutch (1) and/or the speed of the engine of the motor vehicle are controlled according to the selected driving characteristic (3, 4 or 5).

Description

 Method for controlling the operation of a clutch

motor vehicle

The invention relates to a method for controlling the operation of a clutch of a motor vehicle with an automatic transmission, in particular a double clutch of an automatic double clutch transmission, the clutch elements being cooled with the aid of a coolant during operation of the clutch and the thermal load on the clutch being determined during operation.

Different methods for controlling the operation of a clutch of a motor vehicle are known in the prior art. In the methods known in the prior art, for example in the case of a stepped automatic transmission, the thermal load on a wet-running clutch is calculated in advance with the aid of a clutch temperature model (DE 41 24 722 A1). The temperature of the clutch is determined in particular from the friction power. Depending on this then determined - theoretical - temperature of the clutch, the clutch is controlled accordingly, i.e. the corresponding control unit then issues the corresponding control commands to the actuator for engaging and disengaging the clutch elements, and thus controls the corresponding hydraulic pressure.

With wet clutches, so vzw. In the case of friction clutches, in particular also in the case of a double clutch, it is problematic that the heating of the coolant, in particular the cooling oil, has a major influence on the service life of all components of the clutch, in particular on the components of the corresponding clutch elements, namely the friction elements. In particular during a full load start, a high friction energy, i.e. heat, is generated as a result of the slippage, which is generated by the coolant, i.e. vzw. must be removed from the cooling oil accordingly. So far - in the prior art - especially when starting a motor vehicle with an automatic transmission, the corresponding clutch - as explained above - is then controlled depending on the theoretical temperature of the clutch determined there, in particular to damage the components of the clutch to avoid. However, since the state of the art is a theoretically determined temperature of the coupling elements, the known method described above is not yet optimal for this reason alone.

The invention is therefore based on the object of designing and developing the aforementioned method in such a way that the service life of a clutch or the components of a clutch are increased accordingly, in particular damage due to thermal effects is avoided.

The above-mentioned object is now achieved in that the current temperature of the coolant leaving the clutch is measured, that on this basis a specific driving characteristic is selected from a plurality of stored driving characteristics and that the operation of the clutch and / or the speed of the engine of the engine Motor vehicle can be controlled depending on the selected driving characteristic. The method according to the invention offers decisive advantages. First, the actual - current - temperature of the coolant leaving the clutch is measured. From this one can immediately draw conclusions about the actual temperature in the clutch elements or on the friction surfaces. The temperature is therefore no longer determined “theoretically” as in the prior art, but actually. A control unit, in particular in a transmission control unit, also stores or stores a plurality of driving characteristics. Depending on the measured actual current temperature of the A specific driving characteristic is now selected from the coolant leaving the clutch and the operation of the clutch is controlled as a function of this selected driving characteristic, so that the actually existing slip can be controlled precisely, or by realizing the corresponding hydraulic pressures, and - in addition - also the As a result, the method according to the invention has decisive advantages, since with the aid of this method, which can be implemented very inexpensively, the s no essential new components have to be additionally installed in an already existing control system, the coupling can be operated optimally in a simple manner. As a result, the disadvantages described at the outset are therefore avoided and corresponding advantages are achieved, in particular increasing the service life of the clutch.

There are now a multitude of options for designing or developing the method according to the invention in an advantageous manner. For this purpose, reference may first be made to the claims subordinate to claim 1. A preferred exemplary embodiment of the invention will now be described in more detail with reference to a preferred exemplary embodiment. In the drawing shows Fig. 1 shows a schematic representation of the flow of a coolant, here a cooling oil through a clutch designed as a double clutch, wherein the temperature of the coolant leaving the clutch is measured, and

Fig. 2 shows a plurality of stored or determined driving characteristics in a schematic representation in a diagram, depicted as a function of the starting speed or the accelerator pedal position.

1 and 2 show - at least in part - the corresponding method for controlling the operation of a clutch 1 of a motor vehicle, not shown here.

The clutch 1 shown here in FIG. 1 is designed as a double clutch and is connected upstream of an automatic, in particular automated, double clutch transmission, i.e. thus provided or arranged accordingly between the motor shaft and the transmission input shafts.

The clutch elements of clutch 1 are not described in detail here, however, clutch 1 shown here is designed as a so-called friction clutch, that is to say it has corresponding friction surfaces that can be pressed against one another, so that the corresponding torques can also be transmitted. For this purpose, the corresponding coupling elements of the coupling 1 with appropriate pressures, vzw. hydraulically loaded so that the corresponding friction surfaces can come into contact with each other.

A coolant is required to cool the coupling elements during operation of the coupling 1. As can be seen from FIG. 1, a cooling oil flow flows through, since here cooling oil is used as the coolant, the coupling 1 shown here, which is designed as a double clutch, from the inside out, i.e. the flow of the coolant 2 is supplied essentially in the center of the coupling 1 and, by means of the corresponding rotational movement of the coupling elements, the coolant is correspondingly pressed radially outward and leaves the coupling 1 radially in the peripheral region, ie it exits here. As the coolant 2 flows through the clutch 1, the temperature of the coolant 2 increases.

The disadvantages described at the outset are now avoided in that the current temperature of the coolant 2 leaving the clutch 1 is measured, and on this basis a certain driving characteristic curve 3, 4 or 5 from a plurality stored driving characteristics 3 to 5 is selected and then the operation of the clutch 1 and / or the speed of the motor of the motor vehicle - not shown here - are controlled as a function of the selected driving characteristics 3, 4 or 5. 2 that several driving characteristics 3, 4 and 5 are shown here. The driving characteristics 3 to 5 shown here are correspondingly shown as a function of the accelerator pedal position of the motor vehicle (X axis) and as a function of the maximum starting speed (Y axis), that is to say as a function of the engine speed in the starting state. In particular, the driving characteristics 3 to 5 shown here are designed or stored as starting characteristics, ie the driving characteristics 3 to 5 shown here are suitable or intended for controlling the starting process of the corresponding motor vehicle.

For this purpose, the driving characteristics 3 to 5 are vzw in a control unit. stored accordingly in a transmission control unit or an engine control unit, which are not explicitly shown here. Control units of this type have corresponding electrical and / or electronic units, in particular microprocessors, and control the switching sequences of the automatic transmission, in particular the double clutch transmission of a motor vehicle, and the corresponding engine speeds, etc. For this purpose, the control unit, vzw. Corresponding data is supplied to the transmission control unit or the engine control unit of the motor vehicle, for example the corresponding speeds, etc., the transmission control unit or the engine control unit then depending in particular on the selected driving strategy, that is to say in dependence on the respective stored and selected driving characteristic controls the switching processes in the automatic manual transmission and the engine speed.

With the driving characteristics 3 to 5 shown here, in particular the driving characteristics 3 to 5 embodied here as starting characteristics, a particularly advantageous starting strategy for a motor vehicle can now be implemented according to the method according to the invention, with which a starting that is gentle on the clutch and oil, i.e. coolant, is guaranteed. For this purpose, the temperature of the coolant 2 leaving the clutch 1 is first measured using the temperature sensor 6. Each driving characteristic curve 3 to 5 shown in FIG. 2, with further driving characteristic curves not shown here, applies essentially to a specific temperature of the coolant 2 or to a specific temperature range of the coolant 2. Thus, as the temperature of the coolant 2 increases, In order to prevent the thermal load on the coupling elements of the coupling 1, a "flat running" driving characteristic curve may then be selected, according to which the Appropriate starting strategy for the motor vehicle is then implemented. This can be seen well from FIG. 2, the arrow shown here in FIG. 2 shows the selection of the corresponding driving characteristic curve 3 to 5 when the temperature of the coolant 2 increases.

The corresponding method therefore ensures more precise control of the thermal load on a clutch 1, in particular during the starting process of a motor vehicle. Mzw. In addition to the temperature of the coolant 2, the temperature gradient of the coolant 2 is also determined. The development of the temperature gradient in particular suggests a rapid or slow heating of the corresponding coupling elements. In FIG. 2 it can be seen that, taking into account the accelerator pedal position and the maximum starting speed, that is to say the maximum permissible engine speed in the starting process of the motor vehicle, corresponding driving characteristics 3 to 5, that is to say corresponding starting characteristics, are stored here. These are vzw. stored in a corresponding transmission control unit, as already stated.

On the one hand, the speed of the engine can therefore be controlled, in particular also limited, by the characteristic curves 3 to 5 stored here as a function of the current accelerator pedal position. This enables the temperature-friendly operation of the corresponding clutch 1. The corresponding control unit, that is to say the corresponding transmission control unit or engine control unit of the motor vehicle, can then also have a corresponding temperature computing unit, in particular for determining the temperature gradient. The control of the clutch elements, in particular the control of the slip, is optimally possible according to the method described here, without the need to provide additional, additional, cost-intensive components in a motor vehicle with an automatic gearbox and already provided transmission control unit or an provided engine control unit. This is another advantage of the method described here.

Finally, the driving characteristic curve 3 to 5 can be selected as a function of the expected thermal load on the clutch, but as a function of the currently determined temperature of the coolant 2, that is to say with the aid of the temperature sensor 6 or the calculated temperature gradient.

As a result, decisive advantages are achieved with the method described here. REFERENCE LIST

clutch

coolant

1. Driving characteristic

2nd driving characteristic

3. Driving characteristic

temperature sensor

Claims

PATE NTANS PRÜ CH E 1. A method for controlling the operation of a clutch (1) of a motor vehicle with an automatic transmission, in particular a double clutch of an automatic double clutch transmission, the coupling elements being cooled with the aid of a coolant (2) during operation of the clutch and the thermal load on the clutch (1 ) is determined during operation, characterized in that the current temperature of the coolant (2) leaving the clutch (1) is measured, that on this basis a specific driving characteristic (3, 4 or 5) from a plurality of stored driving characteristics (3, 4 or 5) is selected and that the operation of the clutch (1) and / or the speed of the motor of the motor vehicle are then controlled as a function of the selected driving characteristic (3, 4 or 5). 2. The method according to claim 1, characterized in that the temperature gradient of the coolant (2) is additionally determined. 3. The method according to claim 1 or 2, characterized in that a starting characteristic is selected as a driving characteristic (3, 4 or 5) from a plurality of stored starting characteristics. 4. The method according to any one of the preceding claims, characterized in that the driving characteristics (3, 4, 5) and / or the starting characteristics are stored in the transmission control unit. 5. The method according to any one of the preceding claims, characterized in that the clutch (1) is designed as a wet clutch, that cooling oil is used as the coolant (2) and that the cooling oil flows through the clutch (1) substantially radially. 6. The method according to any one of the preceding claims, characterized in that a temperature sensor (6) for measuring the centrifugal oil temperature is provided in the radially adjoining region of the clutch (1). 7. The method according to any one of the preceding claims, characterized in that the speed of the engine is controlled according to the selected driving characteristic (3, 4 or 5) and the current accelerator pedal position. Method according to one of the preceding claims, characterized in that a temperature computing unit is provided with the aid of which the temperature gradient is calculated.