DE102016223037B4 - Method for actuating a clutch, in particular a hybrid clutch of a hybrid vehicle - Google Patents

Abstract

Method for actuating a clutch, in particular a hybrid disconnect clutch of a hybrid vehicle, in which the clutch (12) is moved by a hydrostatic clutch actuator (4), in that a piston (6) mounted so as to be axially movable in a master cylinder (7) of the hydrostatic clutch actuator (4) actuates a slave cylinder (11) that actuates the clutch (12) via a hydrostatic path (9) containing a pressure medium (8), the piston (6) of the master cylinder (7) having a connection opening (15 ) of the master cylinder (7) to an unpressurized expansion tank (14) to equalize the volume of the pressure medium (8), depending on a period of time which, upon detection of an invalid temperature calculation by a temperature model of the hydrostatic path after the end of the release of the connection opening (15) of the master cylinder (7) is started, a signal requesting re-release of the connection opening (14) of the master cylinder (7), the duration being determined by a counter, a count of the counter being incremented each time an invalid temperature calculation is detected, the count of the counter being compared to a threshold value and when the threshold value is exceeded the signal for requesting the renewed release of the connection opening (15) of the master cylinder (7) is generated, characterized in that the count value of the counter remains unchanged when a valid temperature calculation occurs and is incremented at the next invalid temperature signal.

Description

The invention relates to a method for actuating a clutch, in particular a hybrid separating clutch of a hybrid vehicle, in which the clutch is moved by a hydrostatic clutch actuator in that a piston which is mounted in an axially movable manner in a master cylinder of the hydrostatic clutch actuator actuates the clutch via a hydrostatic path containing a pressure medium actuated slave cylinder actuated, wherein the piston of the master cylinder in the unactuated state releases a connection opening of the master cylinder to an unpressurized expansion tank for volume compensation of the pressure medium.

Automated clutches that use a hydrostatic clutch actuator are increasingly being used in modern motor vehicles, in particular passenger cars. Such a hydrostatic clutch actuator has a master cylinder in which a master piston is mounted so that it can move axially. The master piston of the master cylinder, driven by an electric motor, pressurizes a hydraulic fluid, which is arranged in a hydrostatic path, whereby a slave piston of a slave cylinder is moved, the movement of which is transmitted to the clutch, causing it to open. The hydrostatic fluid is subject to changes in volume due to external influences. A change in volume due to changes in the liquid temperature is primarily considered. With the master cylinder in the same position, these volume changes as a result of temperature changes lead to shifts in the slave cylinder. In order to transmit the required clutch torque to the slave cylinder and thus to the clutch, the position of the slave cylinder must be known with sufficient accuracy. To compensate for changes in volume in the hydrostatic line, the master cylinder is moved in such a way that the hydrostatic line is connected to an unpressurized after-flow tank via an opening in the master cylinder. As a result, a volume equalization can take place between the follow-up tank and the hydrostatic path. There is then again a known relationship between the position of the master cylinder and the slave cylinder.

Opening the connection between the after-run tank and the hydrostatic section and waiting in this position until the volume has been equalized is referred to as sniffing. Every sniffing process has a not inconsiderable influence on the driving behavior of the vehicle. On the one hand, frequent sniffing processes reduce driving comfort considerably, and on the other hand, requested switching processes can be delayed by a sniffing process. In order to at least reduce the temperature influence of the pressure medium on a clutch actuated by the hydrostatic actuator in a drive train of the motor vehicle, according to DE 10 2011 103 750 A1 a temperature-dependent change in the pressure medium volume is determined and a travel difference of the slave cylinder piston caused by the change is compensated for by a drive acting on the master cylinder piston. In this way, extended sniffing cycles can be operated without sacrificing driving comfort.

DE 10 2014 219 029 A1 discloses a method for controlling a clutch actuator for actuating an unactuated closed clutch for a motor vehicle.

• • Temperaturbestimmung im Bereich des Aktuators,
• • Ansteuern des Aktuators in Abhängigkeit eines ersten abgespeicherten Parameters, falls die Temperatur einen vorbestimmten Schwellenwert übersteigt, und
• • Ansteuern des Aktuators in Abhängigkeit eines zweiten abgespeicherten Parameters, sonst.

DE 10 2014 215 753 A1 discloses a method for controlling a clutch actuator for actuating a clutch for a motor vehicle, the method comprising the following steps:

• • temperature determination in the area of the actuator,
• • Controlling the actuator as a function of a first stored parameter if the temperature exceeds a predetermined threshold value, and
• • Control of the actuator depending on a second saved parameter, otherwise.

From the DE 10 2013 220 324 A1 a method for the automated actuation of a friction clutch in a drive train of a motor vehicle by means of a hydrostatic system is known. In order to carry out the sniffing processes at an efficient frequency, it is disclosed that a sniffing process is carried out as a function of a multi-stage scale continuously formed from a number of operating variables of the motor vehicle. At the same time, this scale represents a measure of confidence in the position of the slave cylinder and thus of the current clutch torque transmitted via the friction clutch and can range, for example, from "high confidence", according to which no sniffing process is requested and carried out, through levels in between to a " no trust”, after which the activation of the clutch is restricted or deactivated. The levels in between result in a prioritized need for sniffing, with a sniffing process taking place immediately if there is a high priority, with other processes such as switching processes being reset, or if there is a level with a lower priority, after other processes. A considered operating variable is a temperature or a temperature change, which is determined using a temperature model of the hydraulic system. Are the results of the temperature model though impermissible and therefore invalid, the actuator travel cannot be adjusted based on the temperature calculated by this temperature model.

The invention is therefore based on the object of specifying a method for actuating a clutch in which a point in time for requesting a sniffing process is reliably determined by the temperature model despite an inaccurately calculated temperature of the hydrostatic path.

According to the invention, the object is achieved in that, depending on a period of time, which is started when an invalid temperature calculation is detected by a temperature model of the hydrostatic path after the release of the connection opening of the master cylinder has ended, a signal to request renewed release of the connection opening of the master cylinder is generated . Thus, due to the existing operating conditions, despite the imprecise temperature calculation by the temperature model, the need for a sniffing process can be identified. This can be promptly requested to prevent damage to the clutch due to excessive pressure within the hydrostatic path. Since it is possible to dispense with using the results of the temperature model of the hydrostatic path and thus without mathematically determining the position of the actuator path, a very simple but reliable method for triggering a request for the sniffing process is provided.

According to the invention, the period of time is determined by a counter, a counter value being increased each time an invalid temperature calculation is detected, the count value of the counter being compared to a threshold value and, if the threshold value is exceeded, the signal to request renewed release of the connection opening of the master cylinder is generated becomes. Since the results of the temperature calculation by the temperature model can sometimes be valid and sometimes invalid during an operating process of the clutch, a number of invalid temperature calculations is added up using the counter, in order to then determine, by comparison with the threshold value, whether a signal requesting release of the connection opening of the master cylinder is to be generated. This represents a very simple and inexpensive method for determining the need for a sniffing process. The sniffing process can thus be delayed as long as possible and is only carried out if the other electronic means cannot be used to compensate for the actuator travel.

In accordance with the invention, the count of the counter remains unchanged upon the occurrence of a valid temperature calculation and is incremented upon detection of the next invalid temperature calculation. In an alternative, according to the invention, the count value of the counter is reduced when a valid temperature calculation occurs and increased when the next invalid temperature calculation occurs. Depending on the underlying strategy, these two variants are to be used to determine the point in time at which the sniffing process is requested.

In a further development, the count value of the counter is decremented at a predetermined, preferably calibratable, rate during the time periods in which there is a valid temperature calculation. The longer these periods of time, in which a valid temperature calculation is available, last, it can be assumed that the actuator position is being controlled reliably and that a sniffing process is therefore not necessary within a reasonable period of time.

In one embodiment, the count value of the counter can be decremented to zero so that a completely new counting process can be started the first time an invalid temperature calculation occurs after a completed sniffing process.

In a particularly precise variant, the threshold value is calibrated. The threshold value can be adapted to the current conditions of the clutch actuator and the hydrostatic path by means of such a calibration.

The threshold value is advantageously calibrated as a function of a compensation for a travel of the clutch actuator that has already taken place since the last release of the connection opening of the master cylinder. The compensation of the actuator position since the last sniffing process is taken into account in order to determine an exact point in time for the next request for a sniffing process.

In an alternative, the threshold value is calibrated as a function of a temperature change in the hydrostatic path that has already been determined and corrected since the last release of the connection opening of the master cylinder. Here, too, a more precise calculation of the time at which the next sniffing process is requested can be ensured by taking into account the already corrected temperature change in the hydrostatic path.

In a variant, the signal requesting the re-enabling of the master cylinder connection opening as a function of the via step threshold value with a corresponding urgency, the urgency being set higher the lower the threshold value is. As a result, the urgency increases with the time that the temperature model outputs an invalid temperature signal.

The validity or invalidity of the temperature calculation provided by the temperature model is advantageously determined using a plausibility check of input signals of the temperature model. A temperature calculation of the temperature model is considered invalid if the input signals are implausible.

The invention permits numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

• 1 eine Prinzipdarstellung eines Kupplungsbetätigungssystems in einem Fahrzeug,
• 2 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic diagram of a clutch actuation system in a vehicle,
• 2 an embodiment of the method according to the invention.

1 shows a structure of a hydrostatic clutch actuation system 1 for use in a vehicle, in particular in a hybrid vehicle, which has a hybrid disconnect clutch which transmits the torque applied by the internal combustion engine and the torque applied by the electric motor together or alternatively to a drive train of the hybrid vehicle. The hydrostatic clutch actuation system 1 includes an actuator control unit 3 on the transmitter side 2 which controls a hydrostatic clutch actuator 4 . The clutch actuator 4 is kinematically connected to a piston 6 of a master cylinder 7 via a transmission 5 . When the position of the clutch actuator 4 and thus the piston 6 in the master cylinder 7 changes to the right along the actuator travel, the volume of the master cylinder 7 is changed, as a result of which a pressure builds up in the master cylinder 7, which is transmitted via a hydraulic fluid 8 via a hydraulic line 9 to the slave side 10 of the hydrostatic clutch actuation system 1 is transmitted. On the slave side 10, the pressure p of the hydraulic fluid 8 causes a displacement change in a slave cylinder 11, which is transmitted to a clutch 12 in order to actuate it. The clutch 12 is a clutch that is open in the non-actuated state, as is used, for example, in the hybrid disconnect clutch in hybrid vehicles.

The distance covered by the piston 6 of the master cylinder 7 along the actuator travel is determined by a travel sensor 13 . The master cylinder 7 is connected to an unpressurized expansion tank 14, with a connection opening 15 of the master cylinder 7 being released by the piston 6 of the master cylinder 7 when the piston 6 is in a predetermined position. The release of the connection opening 15 until a volume equalization of the hydraulic fluid 8 has taken place is referred to as a sniffing process.

In order to prevent the clutch actuation system 1 from being destroyed, the liquid temperature of the hydraulic liquid 8 is determined as a function of an actuator temperature, which is calculated using a temperature model stored in the actuator control unit 3 . A compensation value for the disengagement path of the clutch actuator 4 is determined with the aid of the fluid temperature of the hydraulic fluid 8 . A circuit board temperature of the clutch actuator 4, an angle sensor temperature and a pressure sensor temperature serve as input signals of the temperature model for calculating the liquid temperature of the hydraulic liquid 8, all of which are installed in the hydrostatic clutch actuator 4 and thus allow a corresponding measurement. These input temperatures are checked against each other for plausibility. If the inlet temperatures are plausible, the liquid temperature determined by the temperature model is considered valid.

In order to now precisely determine the time of a request for the sniffing process, after a sniffing process S1, which 2 is shown, the temperature calculation FluidMdl output by the temperature model is recorded with regard to its validity based on the plausibility check of the input temperature signals. In 2a this FluidMdl temperature calculation is shown over time. If the FluidMdl temperature calculation is close to 0, it is assumed to be valid, while if it is >0 it is invalid.

The FluidMdl temperature calculation jumps back and forth between valid and invalid several times during the time observations. After completion of the sniffing process S1, a counter Z arranged in the actuator control device 3 is started. If the temperature calculation FluidMdl of the temperature model changes from 0 to 1 at time t1, this is considered invalid and the counter Z1 is increased by a predetermined value. The count value of the counter Z1 ( 2 B) is lowered at time t2, where the temperature calculation FluidMdl of the temperature model jumps from invalid to valid, while it is increased at time t3, when an invalid temperature calculation FluidMdl is present again. The count value of the counter Z1 is compared with different threshold values e and f. So e represents a lower threshold dar and f a larger one. If one of the threshold values is exceeded, the actuator control device 3 outputs a signal to request the sniffing process S1.

In an alternative that in 2c is shown, the count value of the counter Z2 is increased by the specified value from the point in time t1 when an invalid FluidMdl temperature calculation is detected. However, from the point in time t2, when the invalid temperature calculation FluidMdl is considered valid again, the count value of the counter Z2 is not reduced but remains at its set value. From time t3, when there is again an invalid FluidMdl temperature calculation, the count of counter Z2 is further increased by the specified value. In this case, too, the count of the counter Z2 can be compared with different threshold values d and c in order to output the corresponding signal for requesting a sniffing process S1 if one of the two threshold values c, d is exceeded.

In order to set a threshold value that corresponds to the current requirements in clutch actuator 4, threshold values c, d, e, f can be calibrated. By means of this calibratability, an urgency of the sniffing process S1 is taken into account. The urgency of the sniffing process S1 depends on the period of time in which the temperature model continuously outputs an invalid temperature calculation FluidMdl. The longer the period, the higher the urgency, resulting in the threshold against which the count is compared being lowered.

In the period in which the temperature calculation of the temperature model is valid, the threshold value can alternatively, instead of being kept at a value, be decremented down to the value 0 at a rate that can be calibrated. The calibration of the threshold value with which the count of the counter Z is compared can also depend on the compensation that has already taken place for the actuator position dL since the last sniffing process S1, as is shown in 2d is shown. In cases where the actuator position dL has already been compensated for by high values (curve b), the threshold value is reduced, ie lowered from threshold f to threshold e or from threshold d to threshold c, faster to request a snoop. This reduces the time period in which the actuator position cannot be compensated precisely enough due to the invalid status of the temperature calculation FluidMdl of the temperature model. However, if little actuator position has been compensated for the case shown in curve a, the threshold value is set higher, for example than threshold f or d. This delays a sniffing request for as long as possible.

In an alternative, the threshold value can also be defined as a function of a change in the temperature dT of the hydrostatic path (master cylinder 7, hydraulic line 9, slave cylinder 11) that has already been determined since the last sniffing process. These changes may resemble those of actuator position compensation as described in 2d are shown correspond. Also in these cases, where a high temperature change has already been corrected since the last sniffing process, the threshold value is reduced in order to reduce the period in which the actuator position cannot be compensated accurately enough due to the invalid status of the temperature calculation of the temperature model.

The solution presented determines a time when a sniffing process is necessary in the event that the temperature model of the hydrostatic path does not calculate the temperature of the liquid with sufficient accuracy, which is why the actuator position cannot be compensated with sufficient accuracy.

reference list

1

hydrostatic clutch actuation unit

2

donor side

3

actuator control unit

4

clutch actuator

5

transmission

6

Pistons

7

master cylinder

8th

hydraulic fluid

9

hydraulic line

10

receiving side

11

slave cylinder

12

coupling

13

displacement sensor

14

surge tank

15

connection opening

Claims (8)

Method for actuating a clutch, in particular a hybrid clutch of a hybrid vehicle, in which the clutch (12) is moved by a hydrostatic clutch actuator (4) by an axially movable in a master cylinder the (7) mounted piston (6) of the hydrostatic clutch actuator (4) actuates a slave cylinder (11) that actuates the clutch (12) via a hydrostatic path (9) containing a pressure medium (8), the piston (6) of the master cylinder (7) in the non-actuated state of the clutch (12), a connection opening (15) of the master cylinder (7) to an unpressurized expansion tank (14) for volume compensation of the pressure medium (8) releases, depending on a period of time which is determined when an invalid temperature calculation is started by a temperature model of the hydrostatic path after the release of the connection opening (15) of the master cylinder (7) has ended, a signal is generated to request renewed release of the connection opening (14) of the master cylinder (7), the time period being determined by a counter is incremented, a count of the counter being incremented each time an invalid temperature calculation is detected, the count of the counter first is compared with a threshold value and if the threshold value is exceeded, the signal for requesting renewed release of the connection opening (15) of the master cylinder (7) is generated, characterized in that the counter value of the counter remains unchanged when a valid temperature calculation occurs and when the next invalid one occurs Temperature signal is increased. Method for actuating a clutch, in particular a hybrid disconnect clutch of a hybrid vehicle, in which the clutch (12) is moved by a hydrostatic clutch actuator (4), in that a piston (6) mounted so as to be axially movable in a master cylinder (7) of the hydrostatic clutch actuator (4) actuates a slave cylinder (11) that actuates the clutch (12) via a hydrostatic path (9) containing a pressure medium (8), the piston (6) of the master cylinder (7) having a connection opening (15 ) of the master cylinder (7) to an unpressurized expansion tank (14) to equalize the volume of the pressure medium (8), depending on a period of time which, upon detection of an invalid temperature calculation by a temperature model of the hydrostatic path after the end of the release of the connection opening (15) of the master cylinder (7) is started, a signal requesting re-release of the connection opening (14) of the master cylinder (7), the duration being determined by a counter, a count of the counter being incremented each time an invalid temperature calculation is detected, the count of the counter being compared to a threshold value and when the threshold value is exceeded the signal for requesting the renewed release of the connection opening (15) of the master cylinder (7) is generated, characterized in that the count value of the counter is reduced when a valid temperature calculation occurs and is increased at the next invalid temperature signal. procedure after claim 1 or 2 , characterized in that the count value is decremented at a predetermined, preferably calibratable, rate during periods in which there is a valid temperature calculation. procedure after claim 3 , characterized in that the count value of the counter is decremented to zero. Method according to at least one of the preceding claims, characterized in that the threshold value is calibrated. procedure after claim 5 , characterized in that the threshold value is calibrated as a function of a compensation for a travel of the clutch actuator (4) that has already taken place since the connection opening (15) of the master cylinder (7) was last released. procedure after claim 5 or 6 , characterized in that the threshold value is calibrated as a function of a temperature change in the hydrostatic path that has already been corrected since the connection opening (15) of the master cylinder (7) was last released. Method according to at least one of the preceding claims, characterized in that the signal for requesting the renewed release of the connection opening (14) of the master cylinder (7) is provided with a corresponding urgency depending on the exceeded threshold value, the urgency being set the higher the lower the threshold is.

Images