Hydraulic system for an automatic transmission of a motor vehicle

Patent metadata

Field	Value
Publication number	US-11293545-B2
Application number	US-201716322688-A
Country	US
Kind code	B2
Filing date	Aug 1, 2017
Priority date	Aug 3, 2016
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

A hydraulic system for an automatic transmission of a motor vehicle, with which hydraulic cylinders of at least one clutch, and of gear selectors can be actuated, which hydraulic system includes a pressure accumulator for providing an accumulator pressure in the hydraulic system. In at least one clutch path leading from the pressure accumulator to the clutch hydraulic cylinder, a clutch valve, which can be operated by an electronic control unit, and with which a hydraulic pressure applied to the clutch hydraulic cylinder can be adjusted, and a pressure sensor, with which the hydraulic pressure applied to the clutch hydraulic cylinder can be detected, are arranged, and having a charging hydraulic pump, which delivers hydraulic fluid into the hydraulic system in a charging process to increase the actual accumulator pressure.

First claim

The invention claimed is:

1. A hydraulic system for an automatic transmission, of a motor vehicle, comprising:
hydraulic cylinders of at least one clutch, and gear selectors is actuated, which hydraulic system includes a pressure accumulator for providing an accumulator pressure in the hydraulic system, wherein, in at least one clutch path leading from the pressure accumulator to the clutch hydraulic cylinder, a clutch valve, which is operated by an electronic control unit, and with which a hydraulic pressure applied to the clutch hydraulic cylinder is adjusted, and a pressure sensor, with which the hydraulic pressure applied to the clutch hydraulic cylinder can be detected, are arranged, and having a charging hydraulic pump, which delivers hydraulic fluid into the hydraulic system in a charging process to increase the actual accumulator pressure, wherein the electronic control unit includes a diagnostic module, with which a preload pressure diagnosis is carried out, in which the diagnostic module checks a preload pressure of the pressure accumulator, using the pressure sensor arranged in the clutch path and diagnoses a fault which is stored in a preload pressure fault memory.

2. The hydraulic system according to claim 1 , wherein a clutch path diagnosis is carried out with the diagnostic module, which is performed as a follow-on diagnosis following the preload pressure diagnosis, and during the clutch path diagnosis, the diagnostic module checks a leakage behavior of the clutch path using the pressure sensor arranged in the clutch path and diagnoses a fault, which is stored in a clutch path fault memory.

3. The hydraulic system according to claim 1 , wherein a gear selector path diagnosis is carried out, in which the diagnostic module checks a leakage behavior in a gear selector path, in which a gear selector valve that is operated by the electronic control unit is arranged, leading from the pressure accumulator to a gear selector hydraulic cylinder, using the pressure sensor arranged in the clutch path, and a fault, which is stored in a gear selector path fault memory, is diagnosed with the diagnostic module.

4. The hydraulic system according to claim 3 , wherein the gear selector valve that is operated by the electronic control unit is arranged in the gear selector path leading from the pressure accumulator to the gear selector hydraulic cylinder, with which valve the hydraulic pressure applied to the gear selector hydraulic cylinder is adjusted, wherein the pressure accumulator includes an oil chamber connected to the gear selector path, to which a preloaded pressure piston is applied and which is filled in the charging process with adjustment of the pressure piston, wherein an accumulator volume diagnosis is carried out with the diagnostic module, in which an analysis unit of the diagnostic module compares an actual accumulator volume of the pressure accumulator to a reference accumulator volume of the pressure accumulator and, if a significant deviation is found, diagnoses a fault which is stored in an accumulator volume fault memory.

5. The hydraulic system according to claim 1 , further comprising:
a low-pressure circuit for cooling the clutch, wherein a high-pressure circuit and the low-pressure circuit have at least the hydraulic pump, which is driven by an electric motor, and wherein the electronic control unit operates 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, 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 a valve spread diagnosis is performed by means of the diagnostic module, in which an actual valve spread between the lower and upper pressure threshold values is determined, and in 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 is stored in a valve spread fault memory.

6. The hydraulic system according to claim 5 , 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 is stored in a switchover time fault memory.

7. The hydraulic system according to claim 1 , wherein a safety valve that is operated by the electronic control unit is arranged upstream of the clutch valve, which safety valve decouples the clutch path from the pressure accumulator with respect to pressure and applies the accumulator pressure to the clutch path in a flow-through position, wherein a safety valve diagnosis is carried out by the diagnostic module, in which the safety valve is switched at a diagnosis start time from the flow-through position into a closed position, namely with actual pressure decrease downstream of the safety valve, and an analysis unit is provided, which compares the actual pressure decrease to a target pressure decrease and, if a significant deviation is present, detects a fault which is read out in a safety valve fault memory.

8. The hydraulic system according to claim 1 , wherein the pressure accumulator is connected via at least one hydraulic path to a hydraulic positioning cylinder, from which a control valve that is operated by the electronic control unit is connected upstream, with which control valve a hydraulic pressure applied to the hydraulic positioning cylinder is adjusted, which control valve is adjusted between two flow-through positions in order to displace a piston in opposing piston strokes via opposing piston positioning distances and piston speeds in the hydraulic positioning cylinder, wherein each piston stroke is linked to a hydraulic fluid removal from the hydraulic system, wherein the electronic control unit includes the diagnostic module, using which a delivery volume flow diagnosis is performed, during which an analysis unit determines an actual delivery volume flow and compares it to a target delivery volume flow and, if there is a significant deviation, detects a fault which is stored in a delivery volume flow fault memory.

9. The hydraulic system according to claim 1 , wherein at least two, fault memories have a signal connection to an analysis unit, in which the fault signals are read out, and an evaluation matrix is stored in the analysis unit, in which the fault signals from the fault memories, are merged, and the analysis unit evaluates all fault signals in combination for a comprehensive hydraulic system diagnosis.

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

• F16H2061/0034

  Accumulators for fluid pressure supply; Control thereof · CPC title

• F16H61/0021

  Generation or control of line pressure · CPC title

• F16H2061/1208

  with diagnostic check cycles; Monitoring of failures · CPC title