Method for detecting a safe state of a valve of a hydraulic system

A device for detecting a safe state of a switchable valve of a hydraulic system of an actuator in a motor vehicle comprising:

• a first switchable valve which is actuated by being energized;
• a pump;
• a controller which controls at least the first switchable valve and the pump, wherein the pump delivers fluid to a first consumer in a first rotational direction and delivers fluid to at least one second consumer in a second rotational direction;
• a line system through which the pump is configured to be connected to the at least one second consumer with the first switchable valve being interposed, wherein the line system has a hydraulic pressure line connected to the pump, a first pressure line branch actuating a parking lock, and a second pressure line branch actuating a friction clutch, wherein the first pressure line branch and the second pressure line branch are configured to be alternately connected to the hydraulic pressure line by the first switchable valve;
• a pressure sensor connected to the controller and mounted in the second pressure line branch, wherein energization of the first switchable valve is deactivated by the controller and the pump is activated with an increasing speed ramp in the second rotational direction, wherein the safe state of the first switchable valve is detected when a pressure difference at the pressure sensor since a start of the increasing speed ramp reaches a predetermined limit value within a predetermined time period since the start of the increasing speed ramp;
• and
• a second switchable valve controlled by the controller and actuated by being energized is introduced into the second pressure line branch, wherein introducing the second switchable valve into the second pressure line branch causes the second pressure line branch to be alternately connected to a reservoir via a discharge line.

A hydraulic system comprising:

• a first switchable valve which is actuated by being energized;
• a pump;
• a first consumer;
• at least one second consumer comprising a parking lock and a friction clutch;
• a controller which controls at least the first switchable valve and the pump, wherein the pump delivers fluid to the first consumer in a first rotational direction and delivers fluid to the at least one second consumer in a second rotational direction;
• a line system through which the pump is configured to be connected to the at least one second consumer with the first switchable valve being interposed, wherein the line system has a hydraulic pressure line connected to the pump, a first pressure line branch actuating the parking lock, and a second pressure line branch actuating the friction clutch, wherein the first pressure line branch and the second pressure line branch are configured to be alternately connected to the hydraulic pressure line by the first switchable valve;
• a pressure sensor connected to the controller and mounted in the second pressure line branch, wherein energization of the first switchable valve is deactivated by the controller and the pump is activated with an increasing speed ramp in the second rotational direction, wherein a safe state of the first switchable valve is detected when a pressure difference at the pressure sensor since a start of the increasing speed ramp reaches a predetermined limit value within a predetermined time period since the start of the increasing speed ramp;
• and
• a second switchable valve controlled by the controller and actuated by being energized is introduced into the second pressure line branch, wherein introducing the second switchable valve into the second pressure line branch causes the second pressure line branch to be alternately connected to a reservoir via a discharge line.