Method and control device for detecting leakage in a pneumatic actuator system

Abstract

Method for detecting leakage in a pneumatic actuating system (7) of a motor vehicle, wherein the pneumatic actuating system (7) comprises an actuating cylinder (9) and an actuating valve (11), where, when the actuating cylinder (9) of the pneumatic actuating system (7) is supplied with air via the actuating valve (11) of the same in order to move an element such as a coupling (4) between two positions or to hold it in a position, the following steps are carried out: A target air mass to be delivered to the actuating cylinder (9) of the actuating system (7) is calculated on the basis of a gas equation, The actual air mass delivered to the actuator cylinder (9) of the actuator system (7) is calculated based on a valve equation. A difference is calculated between the target air mass and the actual air mass. Depending on the difference between the target air mass and the actual air mass, it is determined whether there is a leak in the pneumatic actuating system (7). where, if the difference between the target air mass and the actual air mass is greater than a limit value and the current temperature is less than a limit value, the leakage determination is repeated after a warm-up phase of the vehicle.

Description

[0001] The invention relates to a method and a control device for detecting leakage in a pneumatic actuator system of a motor vehicle.

[0002] From DE 10 2011 075 168 A1, a method for detecting leakage in the actuator of a hydraulically actuated clutch of a motor vehicle is known. The stroke of a piston of an actuator cylinder is determined over time with the clutch open and the venting valves closed, in order to determine the degree of leakage of the actuator cylinder over time. The degree of leakage is taken into account during further operation of the actuator cylinder.

[0003] From DE 10 2015 215 293 A1, a method and a control unit for determining a system pressure in a pneumatic actuating system are known. To determine the system pressure, with the starting clutch closed, at least one switching valve used to control the starting clutch is actuated for a defined actuation period in the opening direction of the starting clutch. During this process, the position of an actuating piston of the pneumatic actuating system is detected. Depending on the length of the actuation period, as well as the position of the actuating piston before and at the beginning of the actuation period, and after or at the end of the actuation period, the system pressure is determined.

[0004] From DE 101 38 777 A1 a method for monitoring the function of supply lines for units operated with a pressurized medium and an associated function monitoring device are known.

[0005] From DE 103 55 250 A1 a method and a device for leak detection are known.

[0006] There is a need to determine leakage in a pneumatic actuator system of a motor vehicle simply and accurately. Based on this need, the invention aims to provide a novel method for determining leakage in a pneumatic actuator system of a motor vehicle and a control device for carrying out the method.

[0007] This problem is solved by a method for determining leakage in a pneumatic positioning system according to claim 1.

[0008] When the actuator cylinder of the pneumatic positioning system is supplied with air via its control valve, particularly to move a coupling between two positions or to hold it in a position, the following steps are performed: A target air mass to be delivered to the actuator cylinder of the pneumatic positioning system is calculated based on the ideal gas law. The actual air mass delivered to the actuator cylinder of the pneumatic positioning system is calculated based on the valve equation. The difference between the target air mass and the actual air mass is calculated. Depending on this difference, it is determined whether a leak exists in the pneumatic positioning system. The leakage determination is based on an air mass calculation. On the one hand, a target air mass is calculated based on the ideal gas law, and on the other hand, an actual air mass is calculated based on the valve equation.The leakage at the pneumatic actuator is determined based on the difference between the target air mass and the actual air mass. This allows for simple and accurate leakage detection.

[0009] According to an advantageous further development, if the difference between the target air mass and the actual air mass exceeds a certain threshold, a leak in the pneumatic control system is inferred. Preferably, if the difference between the target air mass and the actual air mass is negative, a leak in the actuator cylinder of the pneumatic control system is inferred. If the difference between the target air mass and the actual air mass is positive, a leak in the control valve of the pneumatic control system is inferred. This makes it possible to easily and accurately detect the presence of a leak in the pneumatic control system. Furthermore, it can be determined whether the leak is attributable to the actuator cylinder or the control valve.

[0010] If the difference between the target air mass and the actual air mass exceeds a limit value and the current temperature is below a limit value, the leakage test is repeated after the vehicle has warmed up. This allows verification of whether the leak is only temporary at low temperatures or whether it is a permanent leak.

[0011] According to an advantageous further development of the invention, the amount of leakage is compensated for by means of a feedforward control for the control valve. By compensating for the detected leakage, the pneumatic positioning system can be controlled more precisely and effectively.

[0012] The control device according to the invention is defined in claim 8.

[0013] Preferred embodiments are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1 a block diagram of a pneumatic actuator system of a motor vehicle; Fig. 2 a pressure-displacement diagram of an actuator cylinder of a pneumatic clutch actuator of the pneumatic actuating system.

[0014] The invention presented here relates to a method for detecting leakage in a pneumatic actuating system, in particular a pneumatic clutch actuator, and a control device for carrying out the method.

[0015] Fig. Figure 1 shows a highly schematic diagram of a motor vehicle comprising a drive unit 1, an output 2, and a transmission 3 connected between the drive unit 1 and the output 2. The motor vehicle also includes a starting clutch 4 connected between the drive unit 1 and the transmission 3. The operation of the drive unit 1 is controlled and / or regulated by an engine control unit 5. The operation of the transmission 3 and the starting clutch 4 is controlled and / or regulated by a transmission control unit 6. Fig. For this purpose, the engine control unit 5 exchanges data with the drive unit 1, and the transmission control unit 6 exchanges data with the transmission 3. Furthermore, the engine control unit 5 and the transmission control unit 6 exchange data with each other.

[0016] Fig. Figure 1 shows a highly schematic representation of the components of a pneumatic actuating system 7 of the motor vehicle. The actuating system 7 includes an air reservoir 8, which can be filled with compressed air via a pump 13. From the air reservoir 8, various pneumatic actuating elements, namely pneumatic actuating cylinders 9, 10, can be supplied with compressed air, depending on the switching position of control valves 11, 12.

[0017] This shows Fig. 1. By way of example, an actuating cylinder 9 with an actuating piston 9a for the pneumatic actuation of the starting clutch 4 and a pneumatic actuating cylinder 10 with an actuating piston 10a for the pneumatic actuation of the transmission 3, wherein an actuating valve 11 interacts with the actuating cylinder 9 and an actuating valve 12 interacts with the actuating cylinder 10. According to Fig. 1. A position sensor 9b is assigned to the actuator cylinder 9, which serves to control the starting clutch 4, with the aid of which the positions of the actuating piston 9a of the actuator cylinder 9 can be measured. The assemblies 9, 9a, 9b and 11 of the pneumatic actuating system 7 are also referred to as the pneumatic clutch actuator for the starting clutch 4.

[0018] The invention relates to a method for detecting leakage, in particular at the pneumatic clutch actuator of the starting clutch 4, which comprises the actuating cylinder 9 and the actuating valve 11.

[0019] When the actuator cylinder 9 of the pneumatic clutch actuator of the starting clutch 4 is supplied with air via the control valve 11 to move the starting clutch 4 between two positions or to hold it in a defined position, the following steps are performed to detect leakage: A target air mass to be delivered to the actuator cylinder 9 of the pneumatic clutch actuator is calculated based on a gas law. Furthermore, an actual air mass delivered to the actuator cylinder 9 of the pneumatic clutch actuator is calculated based on a valve law. A difference between the target air mass and the actual air mass is calculated. Depending on this difference, it is determined whether a leak exists at the pneumatic clutch actuator of the pneumatic actuating system 7.

[0020] If the difference between the target air mass and the actual air mass exceeds a certain threshold, a leak is suspected at the pneumatic clutch actuator. If this difference is negative, a leak is suspected at actuator cylinder 9. If this difference is positive, a leak is suspected at control valve 11.

[0021] As already explained, the inventive method for determining leakage on a pneumatic clutch actuator of a motor vehicle is based on an air mass calculation and air mass balance.

[0022] Then, when the actuator cylinder 9 is supplied with air via the control valve 11 to move the clutch 4 between two positions or to hold it in a defined position, a target mass of air to be delivered to the actuator cylinder of the pneumatic clutch actuator is first calculated on the basis of a gas equation.

[0023] Preferably, the target air mass to be delivered to the actuator cylinder of the pneumatic clutch actuator is calculated on the basis of the following gas equation: mSOLL=A(p2s2−p1s1)nRT where m SOLL the target air mass is, where A is the cylinder piston area of ​​the actuating cylinder 9, where n is a first constant, namely a polytropic coefficient, where R is a second constant, namely a gas constant, where T is the current temperature, where p1 and p2 are cylinder pressures of the actuator in two cylinder positions, where s1 and s2 are the cylinder positions of the actuator.

[0024] Then, if the coupling 4 is to be held in a defined position, p1=p2 and s1=s2, so that Δm SOLL =0.

[0025] Fig. Figure 2 visualizes a release force of the actuating cylinder 9 in a pressure-displacement diagram, where a pressure p and thus the release force is plotted against the distance or position s of the actuating cylinder 9. Fig. Figure 2 illustrates the release force in the actuating cylinder 9 depending on the position s of the actuating cylinder 9, where in Fig. 2. It is assumed that the actuator cylinder is to be moved from a first, completely emptied position s1, in which the pressure p1 prevails in the actuator cylinder, to position s2, in which the pressure p2 then prevails in the actuator cylinder. The target air mass to be introduced into actuator cylinder 9 during the move from position s1 to position s2 can be calculated using the equation above.

[0026] Furthermore, the actual air mass delivered to the actuator cylinder 9 of the pneumatic clutch actuator is calculated based on a valve equation. The actual air mass delivered to the actuator cylinder 9 is preferably calculated based on the following valve equation: mIST=∑k([cpkρTT25°C(1−(Kkritt−b1−b)2)]Δt) where m IST the actual air mass is, where k are discrete-time summation steps, where c is a conductance of the control valve, where p k the pressure in the actuator cylinder at the summation step k is, where ρ is the air density, where T is the current temperature, where T 25°C a standard temperature where K kritt a constant, namely a critical air ratio of the control valve, where b is a current pressure ratio of the control valve, and where Δt is the actuation time of the control valve.

[0027] The calculation of the actual air mass based on the above valve equation is carried out by summation in several time-discrete summation steps k.

[0028] The difference between the target air mass and the actual air mass is then calculated. Depending on this difference, it is determined whether a leak exists at the pneumatic clutch actuator.

[0029] Preferably, the following difference between the target air mass and the actual air mass is determined: Δm=mSOLL=mACT

[0030] If the magnitude of this difference Δm exceeds a certain limit, a leak is present at the pneumatic clutch actuator. The difference between the target air mass and the actual air mass corresponds to a leakage mass flow rate.

[0031] If the above difference between the target air mass and the actual air mass is negative, a leak at actuator cylinder 9 is assumed.

[0032] If, however, the above difference between the target air mass and the actual air mass is positive, a leak at the control valve 11 is assumed.

[0033] When the vehicle's clutch, actuated by the pneumatic clutch actuator, is to be held in a defined position (i.e., when p1 = p2), the target air mass is zero. If, nevertheless, air mass is supplied to the actuator cylinder 9 via the control valve 11 to hold the clutch in the defined position, then a leak exists at the clutch actuator, specifically at the actuator cylinder 9.

[0034] Leakage detection can be linked to the prevailing ambient temperature. If the difference between the target air mass and the actual air mass exceeds a limit value, and the current temperature is below a limit value (i.e., if a leak is present at low temperatures), the leakage detection can be repeated after the vehicle has warmed up.

[0035] If no leakage is detected after the warm-up phase, it is concluded that the leakage is only temporary and temperature-related. However, if a leakage is still present after the warm-up phase, it is assumed to be permanent and not temperature-related. In the case of a permanent leakage, the amount of leakage can be compensated for by means of a feedforward control signal for the control valve 11. If the permanent leakage becomes too large, a visit to the workshop for the vehicle may be necessary, for example, by generating a corresponding warning message or, in extreme cases, by immobilizing the vehicle.

[0036] The detected leakage can be subjected to statistical analysis. Based on this statistical analysis, the probability of component failure can then be calculated.

[0037] The invention was granted with reference to Fig. 1 and Fig.2 describes the preferred application of a leakage test on the pneumatic clutch actuator of the pneumatic actuating system 7 for the starting clutch 4. A leakage test can also be performed analogously on the pneumatic actuator of the transmission 3, which comprises the control valve 12 and the actuating cylinder 10.

[0038] The invention further relates to a control device of a motor vehicle for carrying out the method. The control device is preferably the transmission control unit 6, which exchanges data with the assemblies involved in the implementation of the method according to the invention, namely with the respective actuator cylinder 9, 10, specifically with the position sensor 9b, 10b thereof, and the control valve 11, 12.

[0039] Then, when the control device appropriately actuates the control valve 11, 12 to supply the actuator cylinder 9, 10 with air in order to move the clutch 4 or an element of the transmission 3 between two positions or to hold it in a position, the control device 6 calculates a target mass of air to be introduced into the actuator cylinder 9, 10 based on the above gas equation.

[0040] Furthermore, the control device 6 calculates an actual air mass delivered to the actuating cylinders 9, 10 on the basis of the above valve equation for the actuating valve 11, 12.

[0041] Furthermore, the control unit 6 calculates a difference between the target air mass and the actual air mass. Depending on this difference, the control unit 6 determines whether a leak is present at the pneumatic clutch actuator, specifically at the actuating cylinder 9, 10 or at the actuating valve 11, 12.

[0042] The invention enables a simple and reliable leakage test on a pneumatic clutch actuator of a motor vehicle clutch. Reference sign 1 drive unit 2 Drive 3 gearboxes 4 Starting clutch 5 Engine control unit 6 Transmission control unit 7 Positioning system 8 air reservoir 9 actuator cylinders 9a Actuating piston 9b Position sensor 10 actuator cylinders 10a Actuating piston 11 Control valve 12 Control valve 13 Pump

Claims

[1] Method for detecting leakage in a pneumatic actuating system (7) of a motor vehicle, wherein the pneumatic actuating system (7) comprises an actuating cylinder (9) and an actuating valve (11), where, when the actuating cylinder (9) of the pneumatic actuating system (7) is supplied with air via the actuating valve (11) of the same in order to move an element such as a coupling (4) between two positions or to hold it in a position, the following steps are carried out: A target air mass to be delivered to the actuating cylinder (9) of the actuating system (7) is calculated on the basis of a gas equation, The actual air mass delivered to the actuator cylinder (9) of the actuator system (7) is calculated based on a valve equation. A difference is calculated between the target air mass and the actual air mass. Depending on the difference between the target air mass and the actual air mass, it is determined whether there is a leak in the pneumatic actuating system (7). where, if the difference between the target air mass and the actual air mass is greater than a limit value and the current temperature is less than a limit value, the leakage determination is repeated after a warm-up phase of the vehicle. [2] Method according to claim 1, characterized by , that if the amount of the difference between the target air mass and the actual air mass is greater than a limit value, a leak in the pneumatic actuating system (7) is concluded. [3] Method according to claim 1 or 2, characterized by , that if the difference between the target air mass and the actual air mass is negative, a leak at the actuator cylinder (9) of the pneumatic actuating system (7) is concluded. [4] Method according to one of claims 1 or 2, characterized by, that if the difference between the target air mass and the actual air mass is positive, a leak at the control valve (11) of the pneumatic control system (7) is concluded. [5] Method according to any one of claims 1 to 4, characterized by , that the target air mass to be delivered to the actuating cylinder (9) of the pneumatic actuating system (7) is calculated on the basis of the following gas equation: mSOLL=A(p2s2−p1s1)nRT where m SOLL the target air mass is, where A is a cylinder piston area of ​​the actuating cylinder, where n is a first constant, where R is a second constant, where T is the current temperature, where p1 and p2 are cylinder pressures of the actuator cylinder, and where s1 and s2 are cylinder positions of the actuator cylinder. [6] Method according to any one of claims 1 to 5, characterized by, that the actual mass of air delivered to the actuating cylinder (9) of the pneumatic actuating system (7) is calculated on the basis of the following valve equation: mIST=∑k([cpkρTT25°C(1−(Kkritt−b1−b)2)]Δt) where m IST the actual air mass is, where k are discrete-time summation steps, where c is a conductance of the control valve, where p k the pressure in the actuator cylinder at the summation step k is, where ρ is the air density, where T is the current temperature, where T 25°C a standard temperature where K kritt a valve constant where b is a current pressure ratio of the control valve, and where Δt is the actuation time of the control valve. [7] Method according to any one of claims 1 to 6, characterized by , that the amount of leakage is compensated for by means of a feedforward control for the control valve. [8] Control device (6) of a motor vehicle for detecting leakage in a pneumatic actuating system (7) of a motor vehicle, wherein the pneumatic positioning system (7) comprises a positioning cylinder (9) and a positioning valve (11), and where, when the control device actuates the control valve (11) of the pneumatic actuating system (7) to supply the actuating cylinder (9) with air in order to move an element such as a coupling (4) between two positions or to hold it in a position the control device (6) calculates a target air mass to be delivered to the actuating cylinder (9) of the pneumatic actuating system (7) on the basis of a gas equation, the control device (6) calculates an actual air mass delivered to the actuating cylinder (9) of the pneumatic actuating system (7) on the basis of a valve equation, the control device (6) calculates a difference between the target air mass and the actual air mass, The control device (6) determines, depending on the difference between the target air mass and the actual air mass, whether there is a leak in the pneumatic actuating system (7), wherein the control device (6) repeats the leakage determination after a warm-up phase of the motor vehicle if the amount of the difference between the target air mass and the actual air mass is greater than a limit value and the current temperature is less than a limit value. [9] Control device (6) according to claim 8, characterized by that it is equipped to carry out the method according to one of claims 2 to 7.

Images