DE102017103815A1 - A method of determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system - Google Patents

Abstract

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 (T_C) is used to determine a compensation value for an actuator travel of a clutch actuator (4) present in the clutch actuation system (1), the temperature (T_C ) of the hydraulic fluid (8) is calculated by a liquid temperature model (16) to which two different temperatures (T_A, T_B) are supplied as input signals.
In a method in which correct temperatures of the hydraulic fluid are determined even if the quality of the temperature signals is inadequate, validity information is assigned to each temperature (T_A, T_B), the fluid temperature model (16) indicating the at least one invalid supplied temperature (T_A, T_B) Temperature (T_C) of the hydraulic fluid (8) calculated from a previous valid supplied temperature (T_A, T_B).

Description

The invention relates to a 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 present in the clutch actuation clutch actuator is determined with the temperature of the hydraulic fluid, wherein the temperature of the hydraulic fluid is calculated by a liquid temperature model, the 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 by changing the 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 occurring volume changes in the hydrostatic connecting line, the master cylinder is moved so that the connecting line is connected via an existing opening in the master cylinder with a non-pressurized return tank. As a result, a volume compensation between the supply reservoir and the connecting line is performed. Thereafter, there is again a known relationship between the position of the master cylinder and the slave cylinder. Opening the connection between the back-up tank and the connection pipe and waiting in this position until the volume compensation has taken place is known as sniffing. However, such a snooping process has a not negligible influence on the driving behavior of the vehicle. On the other hand, frequent snooping operations significantly reduce ride comfort. Requested switching operations can be delayed by a snooping process.

From the DE 10 2014 219 029 A1 For example, 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 travel a maximum distance to actuate a master cylinder to move over a hydrostatic transmission path, which includes a hydraulic fluid, the slave cylinder and fully open the clutch. The release travel of the slave piston on the slave cylinder is limited. It is known that the maximum distance of the clutch actuator is reduced in order not to move the slave cylinder at a temperature increase further than allowed. As a result, the slave cylinder is protected from destruction. It is therefore to be assumed that, when the temperature of the hydraulic fluid in the hydrostatic transmission path increases, at which the hydraulic fluid expands, the actuator travel is compensated so that the expansion is counteracted. It is analogous to a contraction of the liquid during a cooling process.

In the older, not previously published, own German patent application with the official file number DE 10 2017 102 583.9 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 liquid temperature model is insufficient for a calculation of the temperature of the hydraulic fluid, which leads to a faulty compensating value of the actuator travel.

The invention has for its object to provide a method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, which also works when the temperature input signals of the liquid temperature model do not have sufficient quality.

According to the invention, this object is achieved in that a validity information is assigned to each supplied temperature, wherein the liquid temperature model calculates the temperature of the hydraulic fluid from a previous valid supplied temperature in the case of at least one invalid supplied temperature. This has the advantage that the calculation of the temperature of the hydraulic fluid can continue to be performed with the temperatures once supplied to the fluid temperature model, the quality of which was considered sufficient. Thus, erroneous determinations of the compensation value of the Aktorweges be prevented due to an incorrectly determined temperature of the hydraulic fluid.

Advantageously, the last valid supplied of the respective two supplied temperatures is used as the previous valid supplied temperature. The use of the respectively last valid temperatures supplied for the calculation of the temperature of the hydraulic fluid allows, in a steady state of the liquid temperature model, that the temperature of the hydraulic fluid and the dependent thereon compensation value of the actuator position can be maintained in the previously calculated range.

In one embodiment, when the liquid temperature model is not steady, the temperature of the hydraulic fluid oscillates to a state dependent on the last two valid temperatures supplied. This also leads to a reliable determination of the temperature of the hydraulic fluid and thus the compensation value of Aktorweges.

A development of the invention relates to a 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 present in the clutch actuation clutch actuator is determined with the temperature of the hydraulic fluid, wherein the temperature of the hydraulic fluid is calculated by a liquid temperature model, the two different temperatures are supplied as input signal. In order to determine a reliable temperature of the hydraulic fluid even if the quality of the supplied temperatures is insufficient, each supplied temperature is assigned a validity information and if there are no supplied valid temperatures, the calculation of the temperature of the hydraulic fluid by the liquid temperature model is suspended until a first valid temperature of one of the two temperatures occurs, which is used in place 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 determine a compensation value of the actuator travel accordingly quickly therefrom.

In one variant, after the occurrence of a first valid supplied temperature of the other of the two supplied temperatures, the temperature of the hydraulic fluid is calculated from the two first valid supplied temperatures of the two supplied temperatures by the liquid 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 again be used to determine the temperature of the hydraulic fluid.

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

Advantageously, in the calculation of the temperature of the hydraulic fluid temperature jumps are hidden, which occur at the beginning of the use of the first valid of the two supplied temperatures. This ensures that discontinuities are prevented by the switching in the calculation of the temperature of the hydraulic fluid and thus takes place the determination of the compensation value of Aktorweges directly in response to the change in the temperature of the hydraulic fluid.

In one embodiment, the temperature of the hydraulic fluid is calculated with the liquid temperature model between two consecutive sniffer operations of the clutch actuator. This is particularly advantageous whenever there is a long period between consecutive sniffing operations. By the described method can be reliably responded to a change in the temperature of the hydraulic fluid and thus to a change in volume of the hydraulic fluid.

In one embodiment, a period between two consecutive snoops is up to several hours. By blocking the snooping processes for so long, the driving comfort is improved by the lack of snooping and the influence of the snooping operations on the driving behavior is prevented.

In a variant, the method is carried out at Aktorwegkompensation at a non-actuated closed clutch with a hydrostatically actuated clutch actuator with a hydraulic path.

The invention allows numerous embodiments. Two of these 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 eines Fluidtemperaturmodells,
• 3 ein erstes Ausführungsbeispiel des erfindungsgemäßen Verfahrens,
• 4 ein zweites Ausführungsbeispiel des erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic diagram of a clutch actuation system in a vehicle,
• 2 an embodiment of a fluid temperature model,
• 3 a first 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 on the donor side 2 an actuator control unit 3 that one hydrostatic clutch actuator 4 controls. The clutch actuator 4 is about a gearbox 5 with a piston 6 of a master cylinder 7 kinematically connected. When the position of the clutch actuator changes 4 and at the same time the piston 6 in the master cylinder 7 along the Aktorweges to the right is a volume of the master cylinder 7 changed, creating a pressure p in the master cylinder 7 is built, which has a hydraulic fluid 8th via a hydraulic line 9 to the slave side of the hydrostatic clutch actuation system 1 is transmitted. On the taker side 10 causes the pressure p of the hydraulic fluid 8th in a slave cylinder 11 a path change that is transmitted to a clutch 12 to actuate it. At the clutch 12 it is a closed in the unactuated state clutch, as used for example as a hybrid disconnect clutch in hybrid vehicles.

The of the piston 6 of the master cylinder 7 traveled distance along the Aktorweges is by means of a displacement sensor 13 determined. The master cylinder 7 is with a surge tank 14 connected, wherein a connection opening 15 of the master cylinder 7 through the piston 6 of the master cylinder 7 is released when the piston 6 is in a predetermined position, whereby a volume compensation and thus a cooling of the hydraulic fluid in the hydrostatic route is made possible. This volume compensation is called snooping.

To a destruction of the clutch actuation system 1 between two sniffing operations, the temperature of the hydraulic fluid is reduced 8th determined what, with the aid of a liquid temperature model 16 he follows. By means of the temperature of the hydraulic fluid 8th becomes a compensation value of the disengagement travel of the clutch actuator 4 certainly.

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

In situations where one or both temperatures applied to the liquid temperature model T_A and T_B do not have a sufficient high quality, the temperature must be T_C the hydraulic fluid 8th be determined via a replacement strategy. For this purpose, each supplied temperature T_A and T_B a status information associated with the validity of the respective temperatures T_A and T_B to the liquid temperature model 16 transfers.

Furthermore, a distinction is made between the cases in which prior to the application of supplied invalid temperatures T_A and T_B already valid temperatures T_A and T_B present at the liquid temperature model 18, which is already a temperature T_C the hydraulic fluid 8th could be calculated, and cases where there is still no valid supplied temperature T_A and T_B at the liquid temperature model 16 present.

In the event that already has a temperature T_C the hydraulic fluid 8th due to already existing valid temperatures T_A and T_B could be calculated when temperatures occur T_A and T_B with missing sufficient temperature the temperature T_C the hydraulic fluid 8th according to the in 3 illustrated embodiment of the method according to the invention determined. In 3 the temperature T over the time t is shown, wherein the liquid temperature model 16 supplied temperatures T_A and T_B and at the same time by the liquid temperature model 16 from these temperatures T_A and T_B calculated temperature T_C the hydraulic fluid 16 are shown. In a first period Δt1 it is assumed that both the supplied temperature T_A as well as the supplied temperature T_B are valid and thus have a sufficient quality. By the period Δt2 following the period Δt1, the first supplied temperature is produced T_A invalid signals. These invalid signals can not be used to calculate the temperature T_C the hydraulic fluid 8th be used. For this purpose, in addition to the still supplied valid temperature T_B the last validly applied temperature T_A to calculate the temperature T_C the hydraulic fluid 8th used. After expiry of the period Δt2 and at the beginning of the period Δt3 again a valid temperature T_A at the fluid temperature model 16 on, so will with the current supplied temperature T_A and the current temperature supplied T_B the temperature T_C the hydraulic fluid T_C calculated.

The case that still no valid temperatures T_A and T_B the fluid temperature model 16 are fed in 4 discussed, which represents a second embodiment of the method according to the invention. Also in these examples, the temperature T is shown over time t. In the are valid temperatures T_A and T_B shown. It can be seen that initially in a period .DELTA.t4 none of the supplied temperatures T_A and T_B is valid. After expiration of the Period Δt4 is the liquid temperature model 16 for the first time a valid temperature T_A fed. The supplied temperature T_B is still invalid. In this case, this becomes the first valid temperature in the period Δt5 T_A as temperature T_C the hydraulic fluid 8th used ( 4b ). At the beginning of the period Δt6 is also the second temperature T_B valid for a first time. Once both supplied temperatures T_A and T_B the liquid temperature model 16 in sufficient quality, the liquid temperature model becomes 16 initialized based on these first temperatures T_A and T_B and the temperature T_C the hydraulic fluid 8th in the period Δt6 on the basis of the liquid temperature model 16 calculated.

However, in the illustration in 4b the temperature thus determined T_C the hydraulic fluid 8th Temperature jumps .DELTA.T1 and .DELTA.T2, which can lead to the fact that the compensation of the maximum actuator position and the determination of the need to perform a snoop are falsified. For this reason, when determining the temperature T_Cdelta of the hydraulic fluid 8th according to 4c the temperature jumps ΔT1 and ΔT2 hidden, which according to 4b at Start using the valid temperature T_A as temperature T_C the hydraulic fluid 8th (ΔT1) and at the start of the calculation of the temperature T_C the hydraulic fluid 8th based on the two valid temperatures T_A and T_B (ΔT2) with the liquid temperature model 16 arise. Thus it is ensured that the calculation of the compensation value of the Aktorweges and also the determination of the need to perform a snooping process, solely by the change in temperature T_C the hydraulic fluid 8th since the last sniffing is considered.

LIST OF REFERENCE NUMBERS

1

Clutch actuation system

2

donor side

3

actuator control

4

clutch actuator

5

transmission

6

piston

7

Master cylinder

8th

hydraulic fluid

9

hydraulic line

10

recipient side

11

slave cylinder

12

clutch

13

displacement sensor

14

surge tank

15

connecting opening

16

Fluid temperature model

T_A

supplied temperature

T_B

supplied temperature

T_C

Temperature of the hydraulic fluid.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014219029 A1 [0003]
• DE 102017102583 [0004]

Claims (10)

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 with the temperature of the hydraulic fluid (T_C), the temperature (T_C) of the hydraulic fluid (T_C) being determined 8) is calculated by a liquid temperature model (16) to which two different temperatures (T_A, T_B) are supplied as input signals, characterized in that a validity information is assigned to each temperature (T_A, T_B), wherein the liquid temperature model (16) is at least one present invalid temperature supplied (T_A, T_B), the temperature (T_C) of the hydraulic fluid (8) calculated from a previous valid supplied temperature (T_A, T_B). Method according to Claim 1 , characterized in that the last valid one of the respective two supplied temperatures (T_A, T_B) is used as the previous valid supplied temperature (T_A, T_B). Method according to Claim 2 , characterized in that in a non-steady liquid temperature model (16) the temperature (T_C) of the hydraulic fluid (8) settles to a state depending on the last valid two supplied temperatures (T_A, T_B). Method for determining a temperature of a hydraulic fluid in a hydraulic clutch actuation system, wherein the temperature (T_C) of the hydraulic fluid (8) determines a compensation value for an actuator travel of a clutch actuator (4) present in the clutch actuation system (1), the temperature (T_C) being the hydraulic fluid (8) is calculated by a liquid temperature model (16) to which two different temperatures (T_A, T_B) are supplied as input signals, characterized in that a validity information is assigned to each supplied temperature (T_A, T_B) and if no valid supplied Temperatures (T_A, T_B) are present, the calculation of the temperature (T_C) of the hydraulic fluid (8) is suspended by the liquid temperature model (16) until a first valid supplied temperature (T_A) of one of the two supplied temperatures (T_A, T_B) occurs, which instead of the calculated temperature (T_C) of the hydraulic fluid (8) is used. Method according to Claim 4 , characterized in that after 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 applied temperatures (T_A, T_B) of the two supplied temperatures (T_A, T_B) by the liquid temperature model (16) is calculated. Method according to Claim 5 , characterized in that the liquid temperature model (16) is initialized prior to the calculation of the temperature (T_C) of the hydraulic fluid (8). Method according to Claim 4 . 5 or 6 , characterized in that in the calculation of the temperature of the hydraulic fluid temperature jumps are hidden, which occur at the beginning of the use of the first valid of the two supplied temperatures. Method according to at least one of the preceding claims, characterized in that the temperature (T_C) of the hydraulic fluid (8) with the liquid temperature model (16) between two consecutive sniffer operations of the clutch actuator (4) is calculated. Method according to Claim 8 , characterized in that a period of time between two consecutive sniffing operations is up to several hours. Method according to at least one of the preceding claims, characterized in that the method is carried out at Aktorwegkompensation at an unactuated closed clutch (12) with a hydrostatically actuated clutch actuator (4) with a hydraulic path.

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