Heating apparatus for a passenger compartment of a motor vehicle

A heating apparatus for a passenger compartment of a motor vehicle, said vehicle having an engine and a liquid cooling circuit system for the engine, said cooling system including a radiator and a pump forming a high pressure portion and a low pressure portion during operation of said pump within the liquid cooling system,

• the heating apparatus comprising:
• means defining a vehicle cabin heating circuit including a liquid flow passage having an upstream end communicating with the high pressure portion of the liquid cooling system and a downstream end communicating with the low pressure portion of the cooling system so as to allow a portion of the liquid within the cooling system to flow through said liquid flow passage;
• a heat exchanger fluidly disposed within said liquid flow passage;
• control means ressponsive to cooling fluid temperature for selectively causing cooling fluid to flow through the liquid flow passage and through the heat exchanger means in a first circulating mode wherein cooling fluid in the liquid flow passage is substantially isolated from the cooling circuit to prevent flow through the engine and the engine cooling system to enable the heater means to rapidly heat the portion of cooling fluid in the liquid flow passage without heating fluid in the cooling system for rapid passenger compartment warm-up, and a second circulating mode wherein cooling fluid from the engine and cooling circuit flows into said liquid flow passage of the heating circuit, said control valve means including a normally closed first valve preventing liquid flow from the cooling circuit into the heating circuit liquid passage in the first circulating mode and being operable to gradually open when liquid temperature in the heating circuit is above a first predetermined level, thereby initiating the second circulating mode wherein fluid in the cooling circuit gradually flows into the heating circuit to prevent a sudden temperature drop in said heating circuit;
• means for defining a bypass passage in the heating circuit having one end communicating with the liquid flow passage at the downstream end thereof and an opposite end communicating with said liquid flow passage at the upstream end thereof, said bypass passage being positioned to allow cooling liquid to circulate through the liquid flow passage and bypassing the engine cooling system;
• pump means within said liquid flow passage for effecting circulation of liquid through said liquid flow passage and said bypass passage;
• and
• heater means for heating the cooling liquid flowing through said liquid passage.