Hydraulic system of an automatic gearbox

An automatic transmission, of a motor vehicle, comprising:

• a hydraulic system having a hydraulic pump powered by a drive engine for supplying pressure to the hydraulic system,
• a hydraulic reservoir by which, when the drive engine is at rest, a pressure drop in a main pressure circuit of the hydraulic system is at least delayed,
• the hydraulic reservoir being connected to the main pressure circuit by way of either an orifice or a throttle;
• wherein a valve is arranged between the hydraulic pump and a connection line of the main pressure circuit for supplying shifting elements of the automatic transmission,
• the valve at least reduces leakage through the static hydraulic pump when the drive engine is switched off, and
• the valve is integrated in housing of the hydraulic pump.

A method of operating a hydraulic system and an automatic transmission of a motor vehicle, the hydraulic system having a hydraulic pump powered by a drive engine for supplying pressure to the hydraulic system, and a hydraulic reservoir by which, when the drive engine is at rest, a pressure drop in a main pressure circuit of the hydraulic system is at least delayed, the hydraulic reservoir is connected to the main pressure circuit by way of either an orifice or a throttle, the method comprising:

• arranging a valve between the hydraulic pump and a connection line of the main pressure circuit for supplying shifting elements of the automatic transmission,
• at least reducing leakage through the static hydraulic pump, via the valve, when the drive engine is switched off,
• integrating the valve in a housing of the hydraulic pump, and
• acting upon shifting elements of a starting gear, when the drive engine is at rest, by pressure provided from the hydraulic reservoir as long as the pressure provided from the hydraulic reservoir is sufficient to compensate for leakage occurring the main pressure circuit.