Patent ID: 9574624
Date: 2017-02-21
CPC Classifications: F16D,F16H

Claim:
1. A hydraulic system for an automatic transmission, in particular a dual-clutch transmission, of a motor vehicle comprising: a high-pressure circuit comprising a pressure accumulator, at least one clutch, and actuators; a low-pressure circuit for cooling the at least one clutch, a cooling hydraulic pump connected to the low pressure circuit; a charging hydraulic pump connectable to the pressure accumulator and to the low pressure circuit, said cooling hydraulic pump and said charging hydraulic pump being drivable via a shared electric motor; a control device having a pressure model unit, said control device being configured to control the electric motor to run at a charging setpoint speed when recognizing a requirement for charging the pressure accumulator to control the electric motor to run at a cooling setpoint speed or other setpoint speed when recognizing a requirement for cooling or other requirement, to lower the speed of the electric motor to zero for a predetermined period of time when neither a requirement for charging the pressure accumulator nor a requirement for cooling nor another requirement exists, and to control the electric motor to run at least at a test speed after expiration of the predetermined period of time, said pressure model unit during an entire operating time of the hydraulic system detecting actuations of the actuators or other events that influence a pressure of the pressure accumulator, and determining partial pressure differences as a function of the detected actuations of the actuators or other events, said pressure modeling unit modeling a pressure decrease in the pressure accumulator over time during the predetermined period of time as a function of the determined partial pressure differences, and as a function of basic leakage pressure losses of the hydraulic system, wherein when the modeling of the pressure modeling unit indicates a minimal pressure of the pressure accumulator, the control device controls the electric motor to run at the test speed.