Vehicle heating system

1. A vehicle heating system comprising:

a coolant circuit that circulates coolant between an engine and a heater core;

a heating device that heats coolant, which is interposed in the coolant circuit;

a pump for coolant circulation, which is interposed in the coolant circuit; and

a switching valve that switches the coolant flowing through the coolant circuit between a heater-core-side circuit that circulates the coolant among the heater core, the pump and the heating device and an engine-side circuit that circulates the coolant into the engine, wherein

the switching valve has a first inlet to which the coolant from the engine-side circuit flows, a second inlet to which the coolant from the heater-core side circuit flows, a first outlet from which the coolant to the heater-core side circuit flows, a second outlet from which the coolant to the engine-side circuit flows, a bypass that connects the second inlet to the first outlet, a valve port that connects the first inlet to the second outlet, an upper space and a lower space that connects the first inlet to the first outlet and the second inlet, and a thermo valve having a first valve element and a second valve element, such that when the thermo valve is in a first position, the first valve element disconnects the upper space from the lower space and the second valve element opens the valve port, and when the thermo valve is in a second position, the first valve element connects the upper and lower spaces and the second valve element closes the valve port;

wherein, when the switching valve is in the first position, the coolant from the engine-side circuit enters the engine-side circuit only through the valve port, the first valve element blocks the coolant from the engine-side circuit, from entering the heater-core-side circuit through the upper and lower spaces, and the coolant from the heater-core-side circuit is returned to the engine-side circuit and the heater-core-side circuit through the bypass, and

wherein, when the switching valve is in the second position, the coolant from the engine-side circuit enters the heater-core-side circuit and the engine-side circuit through the upper and lower spaces, the coolant from the heater-core-side circuit enters the engine-side circuit, and the coolant from the engine-side circuit is prohibited from entering the engine side circuit through the valve port.

2. The vehicle heating system according to claim 1 , wherein:

the switching valve has a lead-in path that connects the second inlet to the second outlet, such that coolant from the heater-core side circuit is introduced to the engine-side circuit regardless of the position of the thermo valve.

3. The vehicle heating system according to claim 2 , wherein:

the bypass diverges from the lead-in path; and

if the thermo valve is switched to the second position, the coolant from the engine-side circuit enters the heater-core-side circuit through the upper and lower spaces, and the coolant from the engine-side circuit is returned to the engine-side circuit through upper and lower spaces, the bypass and the lead-in path.

4. The vehicle heating system according to claim 1 , wherein:

the thermo valve has a shaft that includes a built-in temperature sensor.