DE19823772A1 - Operating system for temperature-controlled automatic automotive clutch - Google Patents

Abstract

The clutch is incorporated in the vehicle transmission system, the master-cylinder piston being moved by an actuator with the movement transmitted hydraulically by pipe to a slave-cylinder piston. The latter disengages the clutch in opposition to a return spring, while the master cylinder piston contains a non-return valve allowing fluid transfer from a compensating chamber to the master-cylinder working chamber. The actuator is so controlled that even at low temperatures movement of the master cylinder piston in the direction increasing the volume of the master-cylinder working chamber (27) the pressure generated by the return spring in this chamber is maintained. During this movement no flow of fluid takes place from the working chamber to the compensating one. Fluid temperature can be measured or computed, and at low temperatures the speed of movement of the master-cylinder piston can be reduced.

Description

The invention relates to a method for operating an automated Coupling in the drive train of a motor vehicle according to the preamble of Claim 1. The invention further relates to a method for checking a Temperature sensor within an actuator, especially one Temperature sensor within an actuator, especially for an automated one Clutch.

The automation of previously foot-operated clutches in motor vehicles takes place increasing spread. On the one hand, such couplings lead to a considerable improvement in comfort. On the other hand, they are particularly at automated, previously manual gearboxes unavoidable and lead to the convenience of a conventional automatic transmission equipped vehicle, but without showing its additional consumption.

In the actuation transmission from a clutch actuator, for example one Electric motor, there is usually a master cylinder for the clutch itself Master piston is actuated by the actuator, and a via a hydraulic line  slave cylinder connected to the master cylinder, the slave piston immediately actuated the clutch. At low temperatures, the kinematic viscosity of the hydraulic fluid increases sharply. When opening the clutch this led to increased line pressures, resulting in very high performance of the actuator or actuator is associated with the risk that the hydraulic Components are destroyed by impermissibly high line pressures. However, since the performance of the actuator is limited, decreases with decreasing Temperature the adjustment speed, causing possible pressure increases do not overload components.

When closing the clutch, the force of the clutch return spring must be Pressure loss in the line between master cylinder and slave cylinder compensate. At low temperatures there is a risk that the Pressure losses can no longer be compensated for by the restoring force, which in the Working space of the master cylinder a negative pressure occurs, which leads to that consisting of the two work rooms and the management Hydraulic system inflates, which can lead to serious malfunctions.

The invention has for its object a method for operating a to specify the automated coupling with which the described Have problems at low temperatures safely avoided.

The invention is further based on the object of a method for checking a temperature sensor within an actuator, in particular for a  automated clutch, specify which one in a simple way It can be determined whether the temperature sensor is in perfect working order Functional state.

The part of the object of the invention relating to the coupling working method becomes solved with the features of the main claim. By controlling the Actuator such that the overpressure in the working space of the master cylinder among all Under certain circumstances, it is ensured that the system is not inflated takes place. This can be done by the return spring of the clutch is increased by additional measures.

It is advantageous according to claim 2 if the temperature of the hydraulic fluid is measured. It is also appropriate according to claim 3 if the Temperature of the hydraulic fluid is calculated, the temperature of the Hydraulic fluids is calculated from, for example, the outside air temperature or this is set equal.

It is particularly advantageous, however, according to claim 4 Speed of movement of the master piston at low temperatures Reduce. It can be particularly useful if the Speed of movement of the master piston when reaching or falling below a limit of the temperature is reduced unidirectionally. It is advantageous It is particularly important if the master piston is at low temperatures  Direction of a reduction in the size of the working space of the master cylinder is moved faster than in the opposite direction.

With the feature of claim 5 is achieved that despite the reduced Speed of the master piston in the closing direction of the clutch Clutch actuation cycle remains as short as possible overall.

The claim 7 characterizes a second solution to the object of the invention. Every time the master piston moves beyond the sniffer hole is, the system is depressurized, so that when moving the Master piston in the opening direction of the clutch via the sniffer bore defined initial states can be established.

With the features of claim 8 is a particularly high Operational reliability of the clutch achieved. Claim 9 indicates a advantageous method for determining the temperature of the hydraulic fluid, for that no additional sensors are required, the temperature of the Hydraulic fluids are used to control the clutch.

The claim 10 characterizes the method for solving the second part of the Invention task. With this method, the functionality of a Temperature sensor within an actuator, for example the clutch actuator, determine what is important for the operational reliability of the clutch because too  high temperatures within the actuator for faults within the clutch interpret and can lead to destruction of the actuator.

With the features of claim 11, the reliability of the method further improved according to claim 10.

Claim 12 characterizes a moment tracking as a function of Temperature, that is, the torque that can be transmitted by the clutch determined with respect to the upcoming engine torque as a function of temperature becomes. Thus, for example, at high temperatures this is from the clutch Transmittable torque 1.05 times the engine torque and at low Temperatures twice the engine torque.

The sub-claims 13 to 19 indicate advantageous designs. The Claim 20 relates to a method for controlling or regulating a above device.

The invention is described below with the aid of schematic drawings for example and explained in more detail. They represent:

Fig. 1 a drive train of a motor vehicle, with a block diagram of the clutch control device;

FIG. 2 shows a detailed view of the arrangement according to FIG. 1; and

Fig. 3 to 5 curves for explaining the operations of the method according to the invention.

Referring to FIG. 1, a motor vehicle has a motor, such as an internal combustion engine 2, which is connected via a clutch 4 to a transmission, such as transmission, 6, 10, the rear wheels to drive through a propeller shaft 8, and a differential 12th To brake the motor vehicle, a brake system 14 is used with a braking device 16 which is actuated via a brake pedal 18 . Only the connection from the brake device 16 to the left front wheel is shown. It is understood that the braking device 16 interacts with all wheels of the motor vehicle.

An accelerator pedal 19 , which controls a throttle valve 21, is used to control the load of the internal combustion engine 2 . The transmission 6 is shifted by means of a shift lever 23 . The clutch 4 is automated and is actuated by an actuation unit, such as an actuator, 25 via a master cylinder 27 and a slave cylinder 29 . The actuator 25 is controlled by a control unit, such as an electronic control unit 31 , which contains a microprocessor with associated memories and whose inputs are connected to various sensors of the drive train, for example a sensor 32 for the speed of the internal combustion engine, a sensor 34 for detection the wheel speed of the vehicle, a sensor 36 for detecting a shift request by actuating the gear lever 23 , a sensor 38 for detecting the position of the clutch 4 , a sensor 40 for the position of the actuator 25 , a sensor 42 for detecting the cooling water temperature, a sensor 44 for recording the temperature of the intake air and, if necessary, other sensors. The device has a determination unit for determining a temperature. The temperature can be an outside air temperature, cooling water temperature, intake air temperature or another temperature. A temperature can also be obtained from data of another temperature with the aid of a mathematical model of the vehicle or the thermal route between the areas whose temperature is linked.

The slave cylinder 29 interacts directly with the clutch lever 48 , which is pushed into its rest position by a clutch return spring, not shown, in which the clutch 4 is completely closed, ie can transmit its maximum torque.

Fig. 2 shows the components of the clutch actuation in more detail. In the slave cylinder 29, a slave piston 50 operates which demarcates a working space 52 in the interior of the slave cylinder 29th The slave piston 50 directly actuates the clutch lever 48 by means of its piston rod 54 ( FIG. 1).

A line 56 leads from the working space 52 into the working space 58 of the master cylinder 27 , in which a master piston 60 works, which divides the master cylinder 27 into the working space 58 and an equalizing space 62 . A so-called sniffer bore 64 is formed in the cylinder wall of the master cylinder 27 and is connected via a line 66 to a hydraulic fluid container 68 which is vented to the outside.

The master piston 60 has a valve member which, together with it, forms a check valve 70 which opens when the pressure in the compensation chamber 62 exceeds that in the working chamber 58 . A crank mechanism 74 , which is driven by the actuator 25 designed as an electric motor, is used to actuate the piston rod 72 of the master piston 60 .

The positioning of the arrangement is as follows:
When the clutch is fully closed, the slave piston 50 is located at the left stop, the working space 52 being minimal and the master piston 60 being located directly in front of the sniffer bore 64 . If the master piston 60 is then moved further to the left by means of the actuator 25 , the check valve 70 opens, so that hydraulic fluid flows from the compensation chamber 62 into the working chamber 58 . If the master piston 60 is moved further to the left via the sniffer bore 64 , the working space 58 is connected directly to the hydraulic fluid container 68 and the system is reliably depressurized. If the master piston 60 is now moved to the right to open the clutch, the pressure build-up begins exactly in the position in which the master piston 60 passes over the sniffer bore 64 , so that a defined starting position or assignment between master piston 60 and thus the position of the actuator 25 and the fully closed position of the clutch 4 is present. The master piston 60 is then moved to the right by the actuator 25 until the clutch opens completely. To close the clutch, the master piston 60 does not necessarily have to be moved back over the sniffer bore 64 if, for example, the clutch is not intended to transmit its full torque, which is advantageous for many operating states. The slave piston 50 then does not move into its stop position, rather the working spaces 58 and 52 remain under pressure even when the clutch is in the closed position.

When the hydraulic fluid is very cold, the condition may occur that when the clutch is closed (movement of the master piston 60 to the left by means of the actuator 25 ), the then viscous hydraulic fluid does not flow through the line 56 quickly enough, so that a negative pressure builds up in the working chamber 58 leads to an opening of the check valve 70 . The system volume (volume of the working spaces 52 and 58 plus the volume of the line 56 ) then increases, so that the spatial assignment between the master piston 60 and slave piston 50 changes, which is undesirable for reasons of actuation accuracy. So that this inflation does not occur, the speed of movement of the master piston 60 is changed in the closing direction of the clutch at low temperatures, as shown in FIG. 3. S means the distance by which the master piston 60 is moved. t means time. An actuation cycle is shown which, starting from the closed clutch, first opens the clutch (position O). At high temperatures, the subsequent closing movement (dash-dotted straight line 1) takes place at the same speed as the opening movement. With increasingly lower temperatures, the closing movement (straight lines 2 and 3) takes place at an increasingly slower speed. This slower speed means that the hydraulic fluid can flow through the line 56 quickly enough so that no negative pressure builds up in the working space 58 .

Another solution to the problem occurring at low temperatures is shown in FIG. 4. T represents the temperature; h is the stroke by which the master piston 60 is moved starting from the position of the fully opened clutch. SB indicates the position of the sniffer bore 64 . As can be seen, the stroke at low temperatures is always such that the sniffer bore is run over, so that defined starting conditions prevail again during the next actuation cycle. At higher temperatures you can drive with a smaller stroke, which makes it possible to control the torque that the closed clutch transmits according to the operating conditions. Depending on the prevailing temperatures or on the evaluation of the signals from the sensors 38 and 40 ( FIG. 1), a so-called sniffing cycle can be carried out between operating cycles of the clutch, in which the master piston 60 is specifically moved beyond the sniffing bore 64 so that the defined ones Initial conditions for the clutch are restored. As the temperature decreases and the stroke increases (small torque adjustment), the need to install targeted sniffing cycles or to move the master piston 60 beyond the sniffing bore when the clutch is closed increases. This is particularly advantageous when using a device for controlling the torque that can be transmitted by an automated clutch in the drive train of a motor vehicle with an engine and a transmission with a switching element for selecting the transmission ratio and a sensor for detecting the transmission ratio; the engine provides a controllable pending engine torque on the output side available, with an actuation unit that can be controlled by a control unit, such as an actuator, for controlling the torque that can be transmitted by the clutch, the control unit controlling the torque that can be transmitted by the clutch as a function of the engine torque, with a device for determining a temperature, the Coupling torque is controlled within a predefined tolerance band around the existing engine torque and the tolerance band is dependent on a temperature.

Overpressure of the clutch can thus be increased at low temperatures compared to high temperatures. Torque tracking as a function of temperature, that is to say that the torque which can be transmitted by the clutch with respect to the engine torque as a function of temperature is particularly advantageous. It is expedient, for example, at high temperatures if the torque which can be transmitted by the clutch is, for example, 1.05 times the engine torque and at low temperatures is, for example, 2 times the engine torque. These numerical values are examples, a range from 1.02 to 1.5 being advantageous at high temperatures and a range from 1.5 to 2.5 being advantageous at low temperatures. The value of the overpressure k, with M = kM _{clutch motor} may increase as a function of temperature. M _clutch and M _motor are the torque that can be transmitted by the clutch and the pending engine torque.

In another embodiment, it can be useful if the torque tracking is switched off below a limit temperature and the torque that can be transmitted by the clutch to the maximum value is set, the clutch is thus fully engaged.

The temperatures from which the actuation cycles of the clutch according to FIGS. 3 and / or 4 are necessary depend on the hydraulic fluid and the geometric conditions in the cylinders and the connecting line as well as the restoring force of the clutch and can be determined experimentally.

No special sensors are required to determine the temperature of the hydraulic fluid if the temperature is determined according to the following algorithm:

T _{Fl, i + 1} = k _Mot × Dt × T _Mot + k _Air Dt T _Air + (1-k _Mot × Dt + k _Air × Dt) T _{Fl, i} ,

where Dt is a time interval i, k _Mot and k _{air are} empirically determined constants and T _air and T _mot are the mean temperature values of the intake air temperature and the engine temperature (approximated by the cooling water temperature) during the respective time interval i, T _{Fl, i + 1} the fluid temperature at the end of the time interval i and T _{Fl, i is} the fluid temperature at the beginning of the time interval i.

For the operational safety of the automated clutch actuation, it is advantageous to know the temperature of the actuator 25 , which is usually designed as an electric motor. For this purpose, the actuator 25 is equipped with a temperature sensor 76 ( FIG. 2), the output signal of which is also evaluated by the control unit 31 . To check the functionality of the temperature sensor 76 , it is advantageous, in the respective possible operating states, for example in zero gear, to apply a signal sequence according to FIG. 5a to the actuator from the control unit 31 , in which the signal during a certain period of time, for example for 1 s each Piston rod 72 is to be moved by a distance of 15 mm, which is determined by sensor 40 . The control device regulates the current supplied to the actuator 25 in such a way that the desired path shown is obtained, the travel time being approximately 150 ms each. The actuation of the actuator 25 according to FIG. 5a leads to an increase in the actuator or actuator temperatures according to FIG. 5b. The temperature increase during the cycle according to FIG. 5a is recorded and evaluated in control unit 31 . If it lies outside the plausibility limits dotted in FIG. 5b, an error is displayed. It goes without saying that the change in setpoint temperature (straight line as shown in FIG. 5b) is determined empirically if it is ensured that the clutch is in overall good working condition. In order to increase the reliability of the information, the current that must be supplied to the actuator 25 can also be detected so that the operating cycle according to FIG. 5a is established. If the current consumption deviates from the current consumption determined when the coupling is in perfect condition, this indicates a fault in the coupling system or in the actuator.

The invention relates to a method for operating an automated Clutch in the driveline of a motor vehicle and stands out for example, by controlling the actuator in such a way that even at low temperatures when the master piston moves in the direction of a Enlargement of the working space in the master cylinder by the return spring the clutch mediated overpressure is maintained in the work area, so that at this movement, no hydraulic fluid from the work space into the compensation space overflows. In another method, the master piston is at deep Temperatures over one after each clutch actuation cycle Sniffer bore also moves the working area of the master cylinder connects a liquid supply.

The invention further relates to a device for performing the above Procedure.

At low temperatures, the kinematic viscosity and thus the Fluid friction of the fluid medium, such as a brake fluid, which as Hydraulic medium or fluid is used, too. With decreasing  Depending on the GZ speed, this leads to a temperature Increase in pressure loss.

Opening the clutch

When the clutch is opened, pressure drops lead to increased line pressures. If the performance of the actuator were great, line pressures of Over 100 bar destroy the actuator and the hydraulic components. There but the performance of the actuator is lower, the falls Actuator speed and thus the pressure loss. This will make the maximum line pressure occurring is limited to 40 bar, for example. The line pressures rising at low temperatures do not lead to a Overloading the actuator.

Closing the clutch

When the clutch is closed, the restoring force of the clutch must Compensate for pressure drop in the line. Below a fluid temperature of for example -15 ° C there is a risk that at maximum Actuator speed the pressure drops no longer depend on the restoring force can be compensated. Negative pressure is established on the master cylinder and the suction valve opens. If there is no sniffing, it pumps System on.

It is for precise temperature dependent clutch control useful if the fluid temperature is known. An easy Calculation model allows a calculation of the fluid temperature on the basis  existing temperature signals enabled. At low fluid temperatures takes the kinematic viscosity of the brake fluid and thus the Fluid friction increases too. This leads depending on the master cylinder Ge speed to an increase in pressure loss. It is with some Embodiments a temperature-dependent clutch control expedient because a water absorption of the brake fluid from one Fluid temperature of -15 ° C can lead to suction problems.

The following questions are dealt with: How large are the pressure drops in the Line and in the ZA depending on temperature, actuator speed and Water absorption? There is a risk that when opening the clutch the Actuator and the hydraulic components are overloaded? From which Temperature occurs when the clutch is closed? Which Measures must be taken to inflate the hydraulic route to prevent? How can the fluid temperature depend on known Measurement signals are determined?

1. Pressure drop in the hydraulic line

Since the Reynolds number in the hydraulic section is small, there is a purely laminar flow. In the case of a laminar flow, the pressure drop Δp is a linear function of the mean flow velocity v:

The following applies to the flow resistance:

where: ν kinematic viscosity of the brake fluid, ρ density of the Brake fluid, l line length, d line diameter.

For example, the hydraulic route is divided into two areas:
Track outside the bell housing consisting of two rubber hoses and a line. The flow resistance occurring here is designated c _Lei .

Section within the bell housing consisting of line and central release. The flow resistance occurring here is designated c _ZA .

The flow resistances (ie Δp = cv _GZ ) are listed in the following table:

There is essentially the following relationship between the kinematic viscosity of the brake fluid and the fluid temperature T _Fl [° C]:

With A, B and n as specifiable values.  

If the brake fluid has absorbed q _w weight percent water, the factor (1 + q _W / C) is added. 1 / C is a predeterminable factor.

The fluid that is inside the part of the gearbox located in the bell housing hydraulic route is heated more than the fluid outside.

2. Opening the clutch at low temperatures

When opening the clutch, the load at low temperature due to increasing fluid friction increasing pressure increase the actuator. Because of the limited actuator performance decreases the disengagement speed from (power output actuator ∼ master cylinder pressure. Master cylinder speed). This is partly counteracted by the fact that low temperatures increases the performance of the actuator.

It was observed on the test bench that the actuator runs slower but does not switch off. Although the flow resistance increases with falling temperature, the pressure losses due to the decrease in the master cylinder speed are therefore limited (Δp = cv _GZ ).

3. Closing the clutch at low temperatures

Refill occurs, for example, with a vacuum at the GZ of p _NS = -0.025 bar when the refill valve opens. This pressure falls below the master cylinder pressure when the absolute restoring force of the clutch is no longer able to overcome the pressure losses Δp that occur.

When the clutch is closed, the absolute restoring force F _{Rück is} made up of the disengaging force of the clutch F _Kup , the spring force of the spring in the ZA F _{F, ZA} and the friction of the ZA F _{Reib as} follows:

F _Rück = F _Kup -F _{F, ZA} -F _Reib .

The restoring force builds up the following pressure at the ZA:

There is pressure at the GZ:

Suction occurs at the point of the minimum master cylinder pressure p _{GZ, Min} .

As can be seen from (4), p _{GZ, Min} depends on the central release pressure p _ZA and the master cylinder speed v _GZ .

Refill occurs, for example, when: p _{GZ, Min} = p _NS .

With c _NS you get with (2) the fluid temperature after the suction occurs.

The most critical case for re-suctioning is the one in which the vehicle is cold (ie fluid temperature T _Fl = T _Lei = T _ZA ).

The system can inflate below a fluid temperature of, for example, X ° C due to suction. There are basically two ways to avoid inflation:
When the clutch is closed, the master cylinder speed is reduced depending on the temperature so that no further suction can occur.

Torque tracking is switched off, for example, from X ° C. As a result, the clutch closes completely after each shift, whereby the sniffer bore is released and fluid compensation takes place can.

The fluid temperature is inferred or calculated using known temperature signals. The following temperatures relevant for fluid heating are available, for example, via a CAN data bus:

• - Cooling water temperature T _cooling
• - Intake air temperature T _An
• - outside air temperature T _AUSS.

As already mentioned above, the hydraulic route can be divided into two temperature ranges:
Fluid temperature T _Lei outside and fluid temperature T _ZA inside the transmission bell, whereby the following generally applies: T _ZA ≧ T _Lei .

Assuming that T _{Lei is} the only temperature in the system, you are on the safe side when it comes to determining the critical temperatures for inflation. The safety margin is limited, since the pressure losses in the area of T _ZA only make up 15% of the total pressure loss.

If the fluid and the line are heated or cooled, the heat flow between the fluid and the environment is proportional to the temperature gradient between the ambient temperature T _Um and the fluid temperature T _Fl (fluid temperature and temperature of the line is almost the same):

∼ (T _Um -T _Fl ).

The amount of heat emitted or absorbed by the fluid depends on the mass and the specific heat capacity of the fluid and the pipe:

For a sufficiently small time interval Δt = t _{i + 1} -t _i , this equation is simplified:

T _Um = (T _{Um, i + 1} + T _{Um, i} ) / 2 is the mean ambient temperature in the time interval Δt.

Calculation model

From the cooling water, intake air and outside temperature is on the Ambient temperature closed.

It also influences the engine temperature T _Mot as the heating component and the air temperature T _air (temperature of the air entering the engine compartment from the outside) as the cooling component and the fluid temperature.

Engine temperature

In the warm-up phase (ie mean cooling water temperature T _cooling <T _{Mot, i} ), the cooling water temperature rises relatively quickly. It takes a lot more time to heat the engine block. When the engine cools down (ie T _cooling <T _{Mot, i} ), the cooling water cooling rate is approximately the same as that of the engine. For the mean engine temperature T _Mot = (T _{Mot, i + 1} + T _{Mot, i} ) / 2 the following should apply:

T _Cool <T _{Mot, i} : T _{Mot.i + 1} = k _Cool .Δt.T _Cool + (1-k _Cool .Δt) .T _{Mot, i}

T _Cool ≦ T _{Mot, i} : T _{Mot, i + 1} = T _{Mot, i}

Air temperature

Air temperature is the temperature of the air entering the engine compartment from the outside. This temperature is usually but the outside air temperature T _AUSS may be _on, and the intake air temperature T.

The following should apply to the mean air temperature T _air :

T _On <T _Out : T _Air = T _Out = (T _{Out, i + 1} + T _{Out, i} ) / 2

_At T ≦ T _AUSS: T _air = T _{A n} = _{(T, i + 1} + _{T, i)} / 2.

The temperature in the line depends not only on the temperatures that occur, but also on the flow around the line (i.e. vehicle speed, fan on / off):
With low flow: In this case, the measured outside air temperature is slightly influenced by the engine waste heat (the lower the outside air temperature, the greater the influence). Since the intake air temperature is strongly influenced by the engine heat in this case, T _air = T _outside .

The calculated fluid temperature thus increases with the actually existing one at.

When there is a strong flow: The measured outside air temperature corresponds to the real one. In the case of strong inflows, the intake air temperature can even drop below the outside air temperature, ie T _air = T _on . The calculated fluid temperature thus drops with the actually existing one.

In order to achieve a sufficiently good result with these temperatures with the least possible computing effort, the following approach can be used:

(T _{Fl, i + 1} -T _{Fl, i} ) = (T _{Fl, Mot, i + 1} -T _{Fl, i} ) + (T _{Fl, Luft, i + 1} -T _{Fl, i} ) (6)

where: T _{Fl.Mot, i + 1} is T _{Fl, i + 1} (see (5)) which results when T _Um = T _Mot where
k = k _mot
T _{Fl, air, i + 1} is T _{Fl, i + 1} (see (5)) which results when T _Um = T _Luft where k = k _Luft

For example, the following can be used for the k values:

It is sufficient to start the calculation model if T _Aus or T _An fall below -10 ° C.

Initial values:

T _On <T _Out : T _{Fl, 1} = T _{Mot, 1} = T _Out

_At T ≦ T _AUSS: T _{Fl, 1} = T _{eng, 1} = T _An.

The calculation model can be canceled, for example, if the Ignition is switched off.  

The present invention further relates to the earlier application DE 195 04 847, the content of which expressly relates to the disclosure content of the belongs to the present application.

The claims submitted with the application are drafted strikes without prejudice for obtaining further patent protection. The The applicant reserves the right to do so, so far only in the description and / or to claim disclosed features.

Relationships used in subclaims point to the others Training the subject of the main claim by the features of respective subclaim; they are not a waiver of attainment an independent, objective protection for the characteristics of the return to understand related subclaims.

However, the subjects of these subclaims also form independent ones Inventions that are one of the items of the previous sub have claims independent design.

The invention is also not based on the exemplary embodiments of the description limited. Rather, numerous changes are within the scope of the invention and modifications possible, in particular such variants, elements and com combinations and / or materials, for example by combination or Modification of individual in connection with that in general  Description and embodiments as well as the claims described and features or elements or method contained in the drawings steps are inventive and can be combined into one new object or new process steps or process step follow consequences, also insofar as they relate to manufacturing, testing and working processes.

Claims (20)

1. A method for operating an automated clutch in the drive train of a motor vehicle, wherein an actuator actuates a master piston within a master cylinder and the movement of the master piston is hydraulically transmitted via a line to a slave piston working in a slave cylinder, which acts as an actuator of the clutch against the force of a Return spring moved in the opening direction of the clutch, which master piston contains a check valve which allows hydraulic fluid to flow from a compensating chamber into the working chamber of the master cylinder, characterized in that the actuator is controlled in such a way that even at low temperatures when the master piston moves in the direction an enlargement of the working space in the master cylinder an overpressure mediated by the return spring of the clutch is maintained in the working space, so that no hydraulic fluid flows from the working space into the compensation space during this movement. 2. The method according to claim 1, characterized in that the temperature of the hydraulic fluid is measured.   3. The method according to claim 1, characterized in that the temperature of the hydraulic fluid is calculated. 4. The method according to any one of claims 1 to 3, characterized in that the speed of movement of the master piston at low Temperatures is reduced. 5. The method according to claim 4, characterized in that deep Temperatures temperatures below -10 degrees Celsius, preferably below -15 degrees Celsius and particularly advantageously below Are -20 degrees Celsius. 6. The method according to any one of claims 1 to 5, characterized in that that at low temperatures the master piston towards a Reduce the size of the working space of the master cylinder faster is moved as in the opposite direction. 7. Method for operating an automated clutch in the drive train of a motor vehicle, an actuator having a master piston within a Master cylinder actuated and the movement of the master piston over a Hydraulic line on the movement of one in a slave cylinder working slave piston is transmitted, which is an actuator of the Coupling against the force of a return spring in the opening direction of the  Clutch moves, which master piston contains a check valve, which an overflow of hydraulic fluid from a compensation space in enables the working space of the master cylinder, and one minimum volume of the work area of the slave cylinder corresponding stop position of the slave piston completely corresponds to the closed position of the clutch, the master piston below Enlargement of the working space of the master cylinder via one in the wall of the master cylinder, to a hydraulic fluid reservoir connected sniffer bore is also movable, so that the Ar working rooms are depressurized and the coupling is fully closed, and the master piston to control the maximum of the clutch transmissible torque normally not for closing the clutch is moved beyond the sniffer hole, characterized in that that the master piston with decreasing temperature of the hydraulic fluid an increasing number of clutch closings via the Sniffer hole is moved out. 8. The method according to claim 7, characterized in that the Master piston at low temperatures after each Clutch actuation cycle moved beyond the sniffer bore becomes. 9. The method according to claims 1 to 8, characterized in that the engine temperature T _Mot and the outside _air temperature T _{air are} measured, the temperature of the hydraulic fluid T _{Fl is} calculated according to the following algorithm:
T _{Fl, i + 1} = k _Mot × Dt × T _{Mot_mittel} + k _air × Dt × T _{Luft_mittel} + (1-k _Mot × Dt + k _Luft × Dt) T _{fl, i}
where mean:
Dt a time interval i,
k _mot and k _air empirically determined constants,
T _{air_means} and T _{mot_means} each the mean values during the time interval i,
T _{Fl, i + 1} the fluid temperature at the end of the time interval i,
T _{f1, i} the fluid temperature at the beginning of the time interval i, and
the operation of the clutch is controlled as a function of the calculated temperature T _{Fl, i + 1} . 10. Method of checking a temperature sensor within an Ak tors, in particular for an automated clutch, in which Moving the actuator within a test cycle in a predetermined temporal consequence of applying a regulated current is a transfer tion member adjusted by predetermined paths and by the Temperature sensor measured during the test cycle Temperature test curve is compared with a target temperature curve, which in the same test cycle with the temperature in perfect condition temperature sensor was measured, taking a certain amount deviation between the temperature test curve and the  Set temperature curve as to a faulty state of the Temperature sensor is evaluated indicative. 11. The method according to claim 10, characterized in that in addition the current recorded by the actuator is detected and with the Recorded the temperature setpoint compared current consumed becomes. 12. Device for the control of an automated clutch transmissible torque in the drive train of a motor vehicle a motor and a gearbox, the motor adjusts on the output side controllable pending engine torque available, with one of a Control unit controllable actuation unit, such as actuator, for control of the torque transmitted by the clutch, with one device to determine the temperature, characterized in that the Control unit transmits the torque transmitted by the clutch Controls depending on the upcoming engine torque, which Coupling torque within a predetermined tolerance band around the current engine torque is controlled and the tolerance band dependent of the temperature is. 13. The apparatus according to claim 12, characterized in that the width of the tolerance band is temperature-dependent.   14. The apparatus according to claim 12, characterized in that the of the Torque transferable to the engine torque via a clutch Proportionality factor and / or a summand is proportional. 15. The apparatus according to claim 12, characterized in that the of the Coupling transmissible torque larger by a predetermined amount is the pending engine torque. 16. The apparatus according to claim 12, characterized in that the Tolerance band in a higher gear is greater than or equal to one lower gear. 17. The device according to one of claims 14, characterized in that the proportionality factor and / or the summand for higher ones Temperatures is greater than or equal to than at lower temperatures. 18. Device according to one of the preceding claims, characterized characterized in that the transmissible torque at low Temperatures in the range of 1.5 and 2.5 times the upcoming Engine torque is. 19. Device in particular according to one of the preceding claims, characterized in that the maximum increase per unit time of  torque transmitted by the clutch as a function of Temperature is selected. 20. Method for controlling or regulating the automated Coupling transmissible torque, in particular by means of a pre Direction according to one of the preceding claims 12 to 19.