Hydraulic system for an automatic transmission of a motor vehicle

Patent metadata

Field	Value
Publication number	US-11402015-B2
Application number	US-201716322717-A
Country	US
Kind code	B2
Filing date	Aug 1, 2017
Priority date	Aug 3, 2016
Publication date	Aug 2, 2022
Grant date	Aug 2, 2022

Abstract

A hydraulic system for an automatic transmission of a motor vehicle, including a high pressure circuit in which a pressure accumulator, at least one clutch and a gear selector are connected, and comprising a low pressure circuit for cooling the clutch, wherein the high pressure circuit and the low pressure circuit have at least one hydraulic pump that can be driven by an electric motor, and including a control unit that actuates the electric motor of the hydraulic pump when a pressure accumulator charging requirement is detected, wherein the high and low pressure circuits are connected via a bypass line to an integrated accumulator charging valve.

First claim

The invention claimed is:

1. A hydraulic system for an automatic transmission comprising:
a high-pressure circuit, in which a pressure accumulator, at least one clutch, and gear selectors are connected,
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 is driven by an electric motor, and
a control unit, which activates the electric motor of the at least one 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 at least one hydraulic pump to the low-pressure circuit and in a charging position fluidically connects the at least one 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, 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, characterized in that the control unit has a diagnostic module which performs a valve spread diagnosis, in which an actual valve spread between the lower and upper pressure threshold values is determined, and in that the diagnostic module has an analysis unit, which compares the actual valve spread with a target valve spread and, if a deviation is found, diagnoses a fault, which is stored in a valve spread fault memory.

2. The hydraulic system according to claim 1 , wherein a coupling valve, which is actuated by the control unit, is arranged in at least one coupling path extending from the pressure accumulator to the coupling hydraulic cylinder and which sets a hydraulic pressure applied to the coupling hydraulic cylinder, and in that the electronic control unit is assigned a pressure sensor which detects the hydraulic pressure applied to the coupling hydraulic cylinder.

3. The hydraulic system according to claim 2 , wherein the pressure sensor is used to detect the actual accumulator pressure during the switchover timing diagnosis.

4. The hydraulic system according to claim 3 , wherein a measuring range of the pressure sensor lies outside of the upper pressure threshold value, and in that, 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, and in that if the first switchover time lies outside of this time frame, a fault is diagnosed, which is stored in a fault memory.

5. The hydraulic system according to claim 1 , wherein the diagnostic module performs a valve spread diagnosis as a follow-on diagnosis after a fault-free changeover time diagnosis, and in that, with the valve spread diagnosis, an actual valve spread between the lower and upper pressure threshold value is detected, and in that the diagnostic module has an evaluation unit, which compares the actual valve spread with a target valve spread and, in case of the deviation, diagnoses a fault, which is stored in a valve spread fault memory.

6. The hydraulic system according to claim 5 , 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 in that 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.

7. The hydraulic system according to claim 6 , 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 in that during the diagnosis time interval the diagnostic module integrates the piston travel distances to obtain a total travel distance, which the diagnostic module then uses to calculate the pressure decrease associated with the gear selector actuations, and in that 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.

8. The hydraulic system according to claim 5 , wherein when the accumulator charging valve is in the charging position, the at least one hydraulic pump operates at a first pump load and a first current consumption, and when the accumulator charging valve is in the non-charging position, the at least one hydraulic pump operates at a second pump load which is lower than the first pump load, and a second current consumption which is lower than the first current consumption.

9. The hydraulic system according to claim 8 , wherein the control unit is assigned a current measuring device which detects the actual current consumption of the electric motor, and in that the control unit identifies the time of the change from the first current consumption to the second current consumption as the first switchover time and identifies the time of the change from the second current consumption to the second current consumption as the second switchover time.

10. The hydraulic system according to claim 1 , wherein the reference hydraulic cylinder is a gear selector hydraulic cylinder, and in that in a reference gear selector path leading from the pressure accumulator to the reference hydraulic cylinder, a gear selector valve is arranged, which is controlled by the control unit and with which the rate of flow through the reference hydraulic cylinder is adjusted.

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

13. The hydraulic system according to claim 12 , wherein the diagnostic module performs 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 the deviation is found, diagnoses a fault, which is stored in an accumulator volume fault memory.

Assignees

• Audi Ag

Inventors

• Weinhardt Mathias

Classifications

• F16H61/12 Primary

  Detecting malfunction or potential malfunction, e.g. fail safe (in control of hydrostatic gearing F16H61/4192) {; Circumventing or fixing failures} · CPC title

• F15B19/005

  Fault detection or monitoring · CPC title

• F16H61/0021

  Generation or control of line pressure · CPC title

• F16H61/688

  with two inputs, e.g. selection of one of two torque-flow paths by clutches · CPC title

• F16H2061/0034

  Accumulators for fluid pressure supply; Control thereof · CPC title