Hydraulic system for an automatic transmission of a motor vehicle

Patent metadata

Field	Value
Publication number	US-10508666-B2
Application number	US-201716322181-A
Country	US
Kind code	B2
Filing date	Aug 1, 2017
Priority date	Aug 3, 2016
Publication date	Dec 17, 2019
Grant date	Dec 17, 2019

Abstract

A hydraulic system for an automatic transmission, in particular a dual-clutch transmission, of a motor vehicle. A high-pressure circuit, in which a pressure accumulator, at least one clutch, and gear selectors are connected, and a low-pressure circuit for cooling the clutch. The high-pressure circuit and the low-pressure circuit have at least one hydraulic pump, which can be driven by an electric motor. The hydraulic system also has a control unit, which activates the electric motor of the hydraulic pump when a requirement to charge the pressure accumulator is identified. The high-pressure and low-pressure circuits are connected via a bypass line to an integrated accumulator charging valve, which in a non-charging position fluidically connects the hydraulic pump to the low-pressure circuit and in a charging position fluidically connects the hydraulic pump to the high-pressure circuit.

First claim

The invention claimed is:

1. A hydraulic system for an automatic transmission of a motor vehicle, comprising: a high-pressure circuit, in which a pressure accumulator, at least one clutch, and gear selectors are connected, and comprising: a low-pressure circuit for cooling the at least one clutch, wherein the high-pressure circuit and the low-pressure circuit have at least one hydraulic pump, which can be driven by an electric motor, said hydraulic system also having a control unit, which activates the electric motor of the hydraulic pump when a requirement to charge the pressure accumulator is identified, wherein the high-pressure and low-pressure circuits are connected via a bypass line to an integrated accumulator charging valve, which in a non-charging position fluidically connects the hydraulic pump to the low-pressure circuit and in a charging position fluidically connects the hydraulic pump to the high-pressure circuit, wherein the accumulator charging valve switches automatically from the charging position to the non-charging position at a first switchover time if the accumulator pressure in the high-pressure circuit exceeds an upper pressure threshold value (p.sub.max), and switches automatically from the non-charging position to the charging position at a second switchover time if the accumulator pressure drops below a lower pressure threshold value, wherein the control unit has a diagnostic module, by which a valve spread diagnosis is performed, in which an actual valve spread between the lower and upper pressure threshold values can be determined, and the diagnostic module has an analysis unit, which compares the actual valve spread with a target valve spread and, if a significant deviation is found, diagnoses a fault, which can be stored in a valve spread fault memory.

2. The hydraulic system according to claim 1 , wherein to determine the actual valve spread, the analysis unit specifies a diagnosis time interval, which begins at the first switchover time and ends at the second switchover time, and during the diagnosis time interval, an accumulator pressure decrease that corresponds to the actual valve spread occurs, both as a result of actuation of a reference hydraulic cylinder and as a result of hydraulic system leakage.

3. The hydraulic system according to claim 2 , wherein for determining the accumulator pressure decrease during the diagnosis time interval, the reference hydraulic cylinder has a position sensor, which detects the piston travel distances occurring with gear selector actuations, and during the diagnosis time interval the diagnostic module integrates the piston travel distances to obtain a total travel distance, from which the diagnostic module calculates the pressure decrease associated with the gear selector actuations, and from the sum of the pressure decrease associated with the gear selector actuations and the leakage-induced pressure decrease, the analysis unit determines the accumulator pressure decrease.

4. The hydraulic system according to claim 1 , wherein when the accumulator charging valve is in the charging position, the hydraulic pump operates at a high pump load and a high current consumption, and when the accumulator charging valve is in the non-charging position, the hydraulic pump operates at a low pump load and a low current consumption.

5. The hydraulic system according to claim 4 , wherein the control unit is assigned a current measuring device which can detect the actual current consumption of the electric motor, and the control unit identifies the time of the change from the high current consumption to the low current consumption as the first switchover time and identifies the time of the change from the low current consumption to the high current consumption as the second switchover time.

6. The hydraulic system according to claim 2 , wherein the reference hydraulic cylinder is a gear selector hydraulic cylinder, and in a reference gear selector path leading from the pressure accumulator to the reference hydraulic cylinder, a gear selector valve is arranged, which can be controlled by the control unit and with which the rate of flow through the reference hydraulic cylinder can be adjusted.

7. The hydraulic system according to claim 1 , wherein the valve spread diagnosis is performed as a follow-on diagnosis following a switchover timing diagnosis, in which it is determined whether at the first switchover time, the actual accumulator pressure is within range of the upper pressure threshold value, wherein a fault can be stored in a switchover time fault memory.

8. The hydraulic system according to claim 7 , wherein in at least one clutch path leading from the pressure accumulator to a clutch hydraulic cylinder, a clutch valve is arranged, which can be controlled by the control unit and with which the hydraulic pressure applied to the clutch hydraulic cylinder can be adjusted, and the electronic control unit is assigned a pressure sensor, with which the hydraulic pressure applied to the clutch hydraulic cylinder can be detected.

9. The hydraulic system according to claim 8 , wherein the clutch path pressure sensor is used to detect the actual accumulator pressure during the switchover timing diagnosis.

10. The hydraulic system according to claim 9 , wherein a measuring range of the pressure sensor lies outside of the upper pressure threshold value, and on the basis of measured pressure values that lie within the pressure sensor measuring range, an analysis unit estimates a time frame within which the first switchover time will lie if the valve is functioning properly, that if the first switchover time lies outside of this time frame, a fault is diagnosed, which can be stored in a fault memory.

11. The hydraulic system according to claim 2 , wherein in the components that are pressurized with the accumulator pressure during the diagnosis time interval, a leakage-induced pressure decrease occurs.

12. The hydraulic system according to claim 11 , wherein the leakage-induced pressure decrease occurs based upon previous diagnoses or leakage measurements.

13. The hydraulic system according to claim 1 , wherein the switchover timing diagnosis is performed as a follow-on diagnosis following an accumulator volume diagnosis and a gear selector path diagnosis.

14. The hydraulic system according to claim 13 , wherein the diagnostic module can perform an accumulator volume diagnosis, in which an analysis unit of the diagnostic module compares the actual accumulator volume of the pressure accumulator with a reference accumulator volume of the pressure accumulator and if a significant deviation is found, diagnoses a fault, which can be stored in an accumulator volume fault memory.

Assignees

• Audi Ag

Inventors

• Weinhardt Mathias

Classifications

• F16H2061/0034

  Accumulators for fluid pressure supply; Control thereof · CPC title

• F15B2201/50

  Monitoring, detection and testing means for accumulators · CPC title

• F15B19/005 Primary

  Fault detection or monitoring · CPC title

• F15B1/033

  with electrical control means · CPC title

• F16H2061/1208

  with diagnostic check cycles; Monitoring of failures · CPC title