Operating a clutch in a motor vehicle

A method for operating a clutch of a motor vehicle, the clutch having a plurality of clutch linings and a clutch spring, and being connected to a hydraulic pressure system that has a pump, a clutch cylinder and a clutch piston, the hydraulic pressure system being arranged for delivering a hydraulic fluid into the clutch cylinder via the pump and for moving the clutch piston, so that the clutch linings are brought into contact with one another counter to a force of the clutch spring, an air gap being overcome at the grip point of the clutch and the clutch linings being brought into contact;

• wherein a further increase in a pressure in the pressure system would directly bring about a provision of a torque capacity of the clutch, the method comprising the following steps:
• a) filling the clutch cylinder at a controlled rotational speed of the pump in order to deliver the hydraulic fluid into the clutch cylinder until a grip point of the clutch is reached and exceeded and a motor current of the pump has reached a predefined minimum value;
• b) determining a first volume of the hydraulic fluid that is delivered into the clutch cylinder by way of the pump until the minimum value is reached, on the basis of a profile of the controlled rotational speed;
• c) reducing of the value of the first volume by a predefined magnitude, whereby a second volume is defined;
• and
• d) using the second volume for clutch operations during operation of the motor vehicle, the second volume being delivered into the clutch cylinder at a high rotational speed of the pump, so that the clutch is filled to such an extent that the grip point of the clutch is not quite yet reached.

A motor vehicle having a drive unit, a transmission and at least one clutch, the clutch having a plurality of clutch linings and a clutch spring and being connected to a hydraulic pressure system that has a pump, a clutch cylinder and a clutch piston, the hydraulic pressure system arranged to deliver a hydraulic fluid into the clutch cylinder via the pump and to move the clutch piston so that the clutch linings are brought into contact with one another counter to a force of the clutch spring;

• the motor vehicle having an electronic control unit (ECU) configured to operate the clutch by
• a) filling the clutch cylinder at a controlled rotational speed of the pump in order to deliver the hydraulic fluid into the clutch cylinder until a grip point of the clutch is reached and exceeded and a motor current of the pump has reached a predefined minimum value;
• b) determining a first volume of the hydraulic fluid that is delivered into the clutch cylinder by way of the pump until the minimum value is reached, on the basis of a profile of the controlled rotational speed;
• c) reducing of the value of the first volume by a predefined magnitude, whereby a second volume is defined;
• and
• d) using the second volume for clutch operations during operation of the motor vehicle, the second volume being delivered into the clutch cylinder at a high rotational speed of the pump, so that the clutch is filled to such an extent that the grip point of the clutch is not quite yet reached.