Valve device

A valve device configured to regulate a flow rate of a liquid, which is a water-based coolant, at a vehicle, the valve device comprising:

• a first valve element that is placed in a first flow passage which is configured to conduct the liquid;
• and
• a second valve element that is placed in the first flow passage, wherein:
• a surface of the first valve element has a first sliding surface which is opposed to the second valve element;
• a surface of the second valve element has a second sliding surface which is opposed to the first valve element;
• the first sliding surface and the second sliding surface are configured to slide relative to each other to change an opening degree of an opening between the first flow passage and a second flow passage;
• an edge portion of at least one sliding surface among the first sliding surface and the second sliding surface is joined to a sloped surface which is sloped by an acute angle relative to a mating sliding surface which is another sliding surface among the first sliding surface and the second sliding surface and mates with the at least one sliding surface;
• an auxiliary surface is joined to an edge portion of the sloped surface which is opposite to the at least one sliding surface;
• and
• a slope angle of the auxiliary surface relative to the mating sliding surface is smaller than a slope angle of the sloped surface relative to the mating sliding surface.