Heating device suitable for motor vehicles

A heating device suitable for use in a motor vehicle to generate frictional heat, comprising:

• a housing that is arranged in a fixed position and includes a working space and a reservoir space which are divided from one another by a partition and are in fluid communication via at least one feed portion having a feed opening into the working space and a return portion having a return opening into the reservoir space, in order to allow circulation of a viscous liquid in a liquid circuit;
• a motor-driven rotor rotatably mounted within the housing and including a centrifugal disk that rotates in the working space;
• a wall member fixed to the housing, wherein the wall member is stationarily fixed to the housing and together with the rotor forms a working gap for generating heat by liquid friction in response to rotation of the rotor;
• a cooling chamber associated with the housing for circulation of a coolant, the cooling chamber being in heat transfer relationship with the wall member;
• and a control valve arranged in the return portion of the liquid circuit, wherein the control valve is arranged in the partition and comprises a hydraulic pressure-relief valve.