Relief valve

A relief valve comprising:

• a housing including:
• an internal flow passage through which a working fluid flows, and
• a relief port discharging the working fluid from the internal flow passage;
• a valve body including:
• a first pressure-receiving portion receiving pressure of the working fluid flowing in the internal flow passage,
• a second pressure-receiving portion connected to the first pressure-receiving portion to oppose the first pressure-receiving portion and receiving the pressure with a pressure-receiving area that is larger than a pressure-receiving area of the first pressure-receiving portion, and
• a first recessed portion formed at the second pressure-receiving portion at an opposite side relative to a pressure-receiving surface of the second pressure-receiving portion and including a closed-end cylindrical shape;
• the valve body being capable of reciprocating inside the housing;
• and
• a biasing force adjustment mechanism including:
• a spring of which one end is held at the first recessed portion and biasing in a direction opposing the pressure,
• a support portion formed with a second recessed portion retaining the other end of the spring and including a closed-end cylindrical shape, and
• a motor adjusting a rotational angle and causing the support portion to reciprocate.