# US 2019/0170169 A1 · Hydraulic system for an automatic transmission of a motor vehicle > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170169 A1 - Document ID: US20190170169A1 - Status: Published application - Kind: A1 - Application number: 16/322,181 - Filed: 2017-08-01 - Published: 2019-06-06 - Earliest claimed: 2016-08-03 - Assignees: Audi AG - Applicants: Audi AG - Inventors: Mathias WEINHARDT - Web page: https://patentgrep.com/patent/US20190170169A1 ## CPC - F15B 19/005: {Fault detection or monitoring} - F15B 1/033: with electrical control means - F16H 57/0446: {the supply forming part of the transmission control unit, e.g. for automatic transmissions} - F16H 61/0031: {using auxiliary pumps, e.g. pump driven by a different power source than the engine} - F16H 61/12: Detecting malfunction or potential malfunction, e.g. fail safe (in control of hydrostatic gearing F16H61/4192) {; Circumventing or fixing failures} - F15B 2201/50: Monitoring, detection and testing means for accumulators - F16D 13/72: Features relating to cooling - F16H 2061/0034: {Accumulators for fluid pressure supply; Control thereof} - F16H 2061/1208: {with diagnostic check cycles; Monitoring of failures} - F16H 2061/1264: {Hydraulic parts of the controller, e.g. a sticking valve or clogged channel} - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - F16H: GEARING - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES ## 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. ## Claims ### Claim at position 1 1-15. (canceled) ### Claim 16 A hydraulic system for an automatic transmission, in particular a dual-clutch 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 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 (pmax), 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. ### Claim 17 (depends on 16) The hydraulic system according to claim 16, 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. ### Claim 18 (depends on 17) The hydraulic system according to claim 17, 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, which it 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. ### Claim 19 (depends on 16) The hydraulic system according to claim 16, 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. ### Claim 20 (depends on 19) The hydraulic system according to claim 19, 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. ### Claim 21 (depends on 17) The hydraulic system according to claim 17, 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. ### Claim 22 (depends on 16) The hydraulic system according to claim 16, 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. ### Claim 23 (depends on 22) The hydraulic system according to claim 22, 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. ### Claim 24 (depends on 23) The hydraulic system according to claim 23, wherein the clutch path pressure sensor is used to detect the actual accumulator pressure during the switchover timing diagnosis. ### Claim 25 (depends on 24) The hydraulic system according to claim 24, 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. ### Claim 26 (depends on 17) The hydraulic system according to claim 17, wherein in the components that are pressurized with the accumulator pressure during the diagnosis time interval, a leakage-induced pressure decrease occurs. ### Claim 27 (depends on 26) The hydraulic system according to claim 26, wherein the leakage-induced pressure decrease occurs based upon previous diagnoses or leakage measurements. ### Claim 28 (depends on 16) The hydraulic system according to claim 16, wherein the switchover timing diagnosis is performed as a follow-on diagnosis following an accumulator volume diagnosis and a gear selector path diagnosis. ### Claim 29 (depends on 28) The hydraulic system according to claim 28, 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. ### Claim 30 (depends on 16) A method for the diagnostic analysis of components in a hydraulic system according to claim 16.