DE112018001003B4 - Method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system - Google Patents

Abstract

Method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, wherein a compensation value for an actuator travel of a clutch actuator (4) present in the clutch actuation system (1) is determined using the temperature (T_C) of the hydraulic fluid (8), wherein the temperature (T_C) the hydraulic fluid (8) is calculated by a fluid temperature model (16), to which two different temperatures (T_A, T_B) are supplied as input signals, with each supplied temperature (T_A, T_B) being assigned validity information and if there are no valid supplied temperatures (T_A , T_B), the calculation of the temperature (T_C) of the hydraulic fluid (8) by the fluid temperature model (16) is suspended until a first valid supplied temperature (T_A) of one of the two supplied temperatures (T_A, T_B) occurs, which replaces the calculated one Temperature (T_C) of the hydraulic fluid (8) is used, characterized in that after a first valid supplied temperature (T_B) of the other of the two supplied temperatures (T_A, T_B) occurs, the temperature (T_C) of the hydraulic fluid (8) from the two first valid supplied temperatures (T_A, T_B) of the two supplied temperatures (T_A, T_B) are calculated by the liquid temperature model (16).

Description

The invention relates to a method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, wherein the temperature of the hydraulic fluid is used to determine a compensation value for an actuator travel of a clutch actuator present in the clutch actuation system, the temperature of the hydraulic fluid being calculated by a fluid temperature model, which is used as input signals two different temperatures are supplied.

The hydraulic fluid used in hydraulic clutch actuation systems in vehicles is subject to volume changes due to external influences, in particular primarily due to changes in fluid temperature. With the same master cylinder position, these volume changes lead to different displacements of the slave cylinder. In order to transmit the requested clutch torque, the position of the slave cylinder must be known with sufficient accuracy. In order to compensate for volume changes that occur in the hydrostatic connecting line, the master cylinder is moved in such a way that the connecting line is connected to an unpressurized follow-up container via an opening in the master cylinder. This results in a volume equalization between the follow-up container and the connecting line. There is then again a known connection between the position of the master cylinder and that of the slave cylinder. Opening the connection between the follow-up container and the connecting line and waiting in this position until the volume has equalized is referred to as sniffing. However, such a sniffing process has a non-negligible influence on the driving behavior of the vehicle. On the other hand, frequent sniffing significantly reduces driving comfort. Requested switching processes can be delayed by a sniffing process.

DE 10 2011 103 750 A1 discloses a hydrostatic actuator and a method for controlling it.

DE 10 2015 213 297 A1 discloses a method for controlling a clutch actuator, preferably for controlling an unactuated, closed clutch.

DE 10 2008 041 353 A1 discloses a method for compensating volume changes of a hydraulic fluid in a hydraulic actuator of a clutch.
From the DE 10 2014 219 029 A1 a method and a device for controlling a clutch actuator for actuating a clutch, preferably an unactuated closed clutch, for a vehicle are known. The clutch actuator can cover a maximum distance to actuate a master cylinder in order to move the slave cylinder via a hydrostatic transmission path that includes a hydraulic fluid and to completely open the clutch. The release path of the slave piston on the slave cylinder is limited. It is known that the maximum travel of the clutch actuator is reduced so that the slave cylinder does not move further than permitted when the temperature increases. This protects the slave cylinder from destruction. It can therefore be assumed that when the temperature of the hydraulic fluid in the hydrostatic transmission path increases, at which the hydraulic fluid expands, the actuator path is moved by compensation in such a way that the expansion is counteracted. The situation is analogous when the liquid contracts during a cooling process.

In the older, not previously published, own German patent application with the official file number DE 10 2017 102 583 A1 A fluid temperature model is presented, by means of which a temperature of the hydraulic fluid is calculated to determine a compensation value of the actuator travel of the clutch actuator. Such a liquid temperature model has two different temperature input signals. It may happen that the quality of the temperature input signals of the fluid temperature model is not sufficient to calculate the temperature of the hydraulic fluid, which leads to an incorrect compensation value of the actuator path.

The invention is based on the object of specifying a method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, which also works if the temperature input signals of the fluid temperature model do not have sufficient quality.

Not according to the invention, the object is achieved in that each supplied temperature is assigned validity information, with the liquid temperature model calculating the temperature of the hydraulic fluid from a previous valid supplied temperature if there is at least one invalid supplied temperature. This has the advantage that the calculation of the temperature of the hydraulic fluid can continue to be carried out with the temperatures once supplied to the fluid temperature model, the quality of which was considered sufficient. This means that incorrect determinations of the compensation value of the actuator path are due to a incorrectly determined temperature of the hydraulic fluid.

Not according to the invention, but advantageously, the last valid supplied temperature of the two supplied temperatures is used as the previous valid supplied temperature. The use of the last valid temperatures supplied for the calculation of the temperature of the hydraulic fluid allows, when the fluid temperature model is in a steady state, that the temperature of the hydraulic fluid and the compensation value of the actuator position dependent on it can be kept in the previously calculated range.

Not according to the invention, in a non-steady liquid temperature model, the temperature of the hydraulic fluid settles to a state dependent on the last valid two temperatures supplied. This also leads to a reliable determination of the temperature of the hydraulic fluid and thus the compensation value of the actuator path.

The invention relates to a method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, wherein the temperature of the hydraulic fluid is used to determine a compensation value for an actuator travel of a clutch actuator present in the clutch actuation system, the temperature of the hydraulic fluid being calculated by a fluid temperature model, which is used as an input signal two different temperatures are supplied. In order to determine a reliable temperature of the hydraulic fluid even if the quality of the supplied temperatures is not sufficient, each supplied temperature is assigned validity information and if there are no valid temperatures supplied yet, the calculation of the temperature of the hydraulic fluid by the fluid temperature model is suspended until one first valid temperature of one of the two temperatures occurs, which is used instead of the calculated temperature of the hydraulic fluid. This has the advantage that when the first valid temperature of one of the two supplied temperatures occurs, it is used as the temperature of the hydraulic fluid in order to quickly determine a compensation value for the actuator path.

According to the invention, after a first valid supplied temperature of the other of the two supplied temperatures occurs, the temperature of the hydraulic fluid is calculated from the first two valid supplied temperatures of the two supplied temperatures by the fluid temperature model. Thus, after a transition period where the temperature of the hydraulic fluid is replaced by a first valid temperature of one of the two supplied temperatures, the normal calculation by the fluid temperature model can be used again to determine the temperature of the hydraulic fluid.

In one embodiment, the fluid temperature model is initialized prior to calculating the temperature of the hydraulic fluid. Initialization ensures that a starting point for all subsequent hydraulic fluid temperature calculations is established in the fluid temperature model.

Advantageously, when calculating the temperature of the hydraulic fluid, temperature jumps that occur when the first valid of the two supplied temperatures begin to be used are ignored. This ensures that discontinuities caused by the switchover in the calculation of the temperature of the hydraulic fluid are prevented and the compensation value of the actuator path is therefore determined directly depending on the change in the temperature of the hydraulic fluid.

In one embodiment, the temperature of the hydraulic fluid is calculated using the fluid temperature model between two successive sniffing processes of the clutch actuator. This is particularly advantageous when there is a long period of time between successive sniffing processes. The method described makes it possible to react reliably to a change in the temperature of the hydraulic fluid and thus to a change in the volume of the hydraulic fluid.

In one embodiment, a period of time between two successive sniffing processes is up to several hours. By preventing sniffing processes for such a long time, driving comfort is improved by the absence of sniffing processes and the influence of sniffing processes on driving behavior is prevented.

In one variant, the method is carried out with an actuator path compensation for an unactuated, closed clutch with a hydrostatically operated clutch actuator with a hydraulic system.

The invention allows numerous embodiments. Two of them will be explained in more detail using the figures shown in the drawing.

• 1 eine Prinzipdarstellung eines Kupplungsbetätigungssystems in einem Fahrzeug,
• 2 ein Ausführungsbeispiel eines Fluidtemperaturmodells,
• 3 ein erstes Ausführungsbeispiel des erfindungsgemäßen Verfahrens,
• 4 ein zweites Ausführungsbeispiel des erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic representation of a clutch actuation system in a vehicle,
• 2 an embodiment of a fluid temperature model,
• 3 a first exemplary embodiment of the method according to the invention,
• 4 a second embodiment of the method according to the invention.

1 shows a structure of a hydrostatic clutch actuation system 1 for use in a vehicle. The hydrostatic clutch actuation system 1 includes an actuator control device 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 gear 5. When the position of the clutch actuator 4 and the piston 6 in the master cylinder 7 changes to the right along the actuator path, a volume of the master cylinder 7 is changed, whereby a pressure p is built up in the master cylinder 7, which is sent via a hydraulic fluid 8 via a hydraulic line 9 to the slave side of the hydrostatic clutch actuation system 1 is transmitted. On the slave side 10, the pressure p of the hydraulic fluid 8 in a slave cylinder 11 causes a change in path, which is transmitted to a clutch 12 in order to actuate it. The clutch 12 is a clutch that is closed in the unactuated state, such as is used, for example, as a hybrid separating clutch in hybrid vehicles.

The distance traveled by the piston 6 of the master cylinder 7 along the actuator path is determined by means of a displacement sensor 13. The master cylinder 7 is connected to an 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, thereby equalizing the volume and thus cooling the hydraulic fluid in the hydrostatic route is made possible. This volume equalization is referred to as the sniffing process.

In order to prevent destruction of the clutch actuation system 1 between two sniffing processes, the temperature of the hydraulic fluid 8 is determined, which is done with the aid of a fluid temperature model 16. A compensation value for the release path of the clutch actuator 4 is determined using the temperature of the hydraulic fluid 8.

2 shows a schematic representation of the liquid temperature model 16, to which a first temperature T_A and a second temperature T_B are supplied. The temperatures T_A and T_B are two temperatures measured close to or in the clutch actuation system 1, such as a measured ambient temperature and a measured actuator temperature. In the liquid temperature model 16, a temperature T_C of the hydraulic fluid 8 is determined according to a predetermined algorithm from the two measured temperatures T_A and T_B supplied.

In situations in which one or both temperatures T_A and T_B supplied to the fluid temperature model do not have a sufficiently high quality, the temperature T_C of the hydraulic fluid 8 must be determined using a replacement strategy. For this purpose, each supplied temperature T_A and T_B is assigned status information, which transmits the validity of the respective temperatures T_A and T_B to the liquid temperature model 16.

A distinction is also made between cases in which, before invalid temperatures T_A and T_B were applied, there were already valid temperatures T_A and T_B on the liquid temperature model 18, from which a temperature T_C of the hydraulic fluid 8 could already be calculated, and cases in which There was still no valid supplied temperature T_A and T_B on the liquid temperature model 16.

In the event that a temperature T_C of the hydraulic fluid 8 could already be calculated based on existing valid temperatures T_A and T_B, if temperatures T_A and T_B occur with insufficient quality, the temperature T_C of the hydraulic fluid 8 is calculated according to in 3 illustrated embodiment of the method according to the invention is determined. In 3 the temperature T is shown over time t, with the temperatures T_A and T_B supplied to the liquid temperature model 16 and at the same time the temperature T_C of the hydraulic fluid 16 calculated by the liquid temperature model 16 from these temperatures T_A and T_B are shown. In a first period Δt1, it is assumed that both the supplied temperature T_A and the supplied temperature T_B are valid and therefore have sufficient quality. In the period Δt2 following the period Δt1, the first supplied temperature T_A supplies invalid signals. These invalid signals cannot be used to calculate the temperature T_C of the hydraulic fluid 8. For this purpose, in addition to the valid temperature T_B that continues to be supplied, the last valid temperature T_A that is still supplied is used to calculate the temperature T_C of the hydraulic fluid 8. Is after the period Δt2 and At the beginning of the period Δt3 a valid temperature T_A is again present at the fluid temperature model 16, the temperature T_C of the hydraulic fluid T_C is calculated with the current supplied temperature T_A and the current supplied temperature T_B.

The case in which no valid temperatures T_A and T_B have yet been supplied to the fluid temperature model 16 is discussed in 4 discussed, which represents a second embodiment of the method according to the invention. The temperature T is also shown over time t in these examples. In the Valid temperatures T_A and T_B are shown. It can be seen that initially in a period Δt4 none of the supplied temperatures T_A and T_B are valid. After the period Δt4 has elapsed, a valid temperature T_A is supplied to the liquid temperature model 16 for the first time. The supplied temperature T_B is still invalid. In this case, this temperature T_A, which is valid for the first time in the period Δt5, is used as the temperature T_C of the hydraulic fluid 8 ( 4b) . At the beginning of the period Δt6, the second temperature T_B is also valid for the first time. As soon as both temperatures T_A and T_B supplied to the liquid temperature model 16 are available in sufficient quality, the liquid temperature model 16 is initialized based on these first temperatures T_A and T_B and the temperature T_C of the hydraulic fluid 8 in the period Δt6 is calculated based on the liquid temperature model 16.

However, the representation in 4b the thus determined temperature T_C of the hydraulic fluid 8 shows temperature jumps ΔT1 and ΔT2, which can lead to the compensation of the maximum actuator position and the determination of the need to carry out sniffing being falsified. For this reason, when determining the temperature T_Cdelta of the hydraulic fluid 8 according to 4c the temperature jumps ΔT1 and ΔT2 are hidden, which according to 4b at the start of using the valid temperature T_A as the temperature T_C of the hydraulic fluid 8 (ΔT1) and at the start of the calculation of the temperature T_C of the hydraulic fluid 8 based on the two valid temperatures T_A and T_B (ΔT2) with the fluid temperature model 16. This ensures that the calculation of the compensation value of the actuator path and also the determination of the need to carry out a sniffing process are taken into account solely by the change in the temperature T_C of the hydraulic fluid 8 since the last sniffing.

Reference symbol list

1

Clutch actuation system

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

Distance sensor

14

surge tank

15

connection opening

16

Fluid temperature model

T_A

supplied temperature

T_B

supplied temperature

T_C

Hydraulic fluid temperature.

Claims (6)

Method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, wherein a compensation value for an actuator travel of a clutch actuator (4) present in the clutch actuation system (1) is determined using the temperature (T_C) of the hydraulic fluid (8), wherein the temperature (T_C) the hydraulic fluid (8) is calculated by a fluid temperature model (16), to which two different temperatures (T_A, T_B) are supplied as input signals, with each supplied temperature (T_A, T_B) being assigned validity information and if there are no valid supplied temperatures (T_A , T_B), the calculation of the temperature (T_C) of the hydraulic fluid (8) by the fluid temperature model (16) is suspended until a first valid supplied temperature (T_A) of one of the two supplied temperatures (T_A, T_B) occurs, which replaces the calculated one Temperature (T_C) of the hydraulic fluid (8) is used, characterized in that after the occurrence of a first valid supplied temperature (T_B) of the other of the two supplied temperatures (T_A, T_B), the temperature (T_C) of the hydraulic fluid (8) from the two first valid supplied temperatures (T_A, T_B) of the two supplied temperatures (T_A, T_B) are calculated by the liquid temperature model (16). Procedure according to Claim 1 , characterized in that the liquid temperature model (16) is initialized before calculating the temperature (T_C) of the hydraulic fluid (8). Procedure according to Claim 1 or 2 , characterized in that when calculating the temperature of the hydraulic fluid, temperature jumps are hidden that occur when the first valid of the two supplied temperatures begins to be used. Method according to at least one of the preceding claims, characterized in that the temperature (T_C) of the hydraulic fluid (8) is calculated using the fluid temperature model (16) between two successive sniffing processes of the clutch actuator (4). Procedure according to Claim 4 , characterized in that a period between two successive sniffing processes is up to several hours. Method according to at least one of the preceding claims, characterized in that the method is carried out with an actuator path compensation in an unactuated, closed clutch (12) with a hydrostatically actuated clutch actuator (4) with a hydraulic system.

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