Abstract: A lock valve including a poppet valve element which is disposed within a spring chamber, a spring which biases the poppet valve element leftward, and a valve seat which comes into contact with the poppet valve element is disposed in a cavity formed in a valve body to mount a relief valve therein and is positioned further inward than the sleeve of the relief valve. The outer peripheral portion of the poppet valve element has hole portions formed therein at regular intervals. The outer peripheral portion of the valve seat, too, has hole portions formed therein at regular intervals. The valve portion of a solenoid valve is disposed between a passage which is in communication with the spring chamber and a passage which is in communication with a second flow passage open to a low-pressure region such as a hydraulic tank.

Abstract: A lock valve including a poppet valve element which is disposed within a spring chamber, a spring which biases the poppet valve element leftward, and a valve seat which comes into contact with the poppet valve element is disposed in a cavity formed in a valve body to mount a relief valve therein and is positioned further inward than the sleeve of the relief valve. The outer peripheral portion of the poppet valve element has hole portions formed therein at regular intervals. The outer peripheral portion of the valve seat, too, has hole portions formed therein at regular intervals. The valve portion of a solenoid valve is disposed between a passage which is in communication with the spring chamber and a passage which is in communication with a second flow passage open to a low-pressure region such as a hydraulic tank.

Abstract: A pressure control valve includes a main valve unit provided with a main valve element and a valve housing body having a main valve seat capable of seating the main valve element and having a pilot chamber for slidably housing the main valve element. A pilot valve unit is provided with a pilot valve element and a pilot valve seat member has a pilot valve seat capable of seating the pilot valve element and separating the pilot valve element from the pilot valve seat and opening when a pressure in the pilot chamber exceeds a predetermined pressure. The pressure control valve is configured with recessed (concaved) parts that form hydraulic fluid channels between the pilot valve seat member and the pilot valve element when the pilot valve unit is in an open-valve-state at three or more locations so as to be separated by equal angles. Each recess has the same shape.

Abstract: A pressure control valve includes a main valve unit provided with a main valve element and a valve housing body having a main valve seat capable of seating the main valve element and having a pilot chamber for slidably housing the main valve element. A pilot valve unit is provided with a pilot valve element and a pilot valve seat member has a pilot valve seat capable of seating the pilot valve element and separating the pilot valve element from the pilot valve seat and opening when a pressure in the pilot chamber exceeds a predetermined pressure. The pressure control valve is configured with recessed (concaved) parts that form hydraulic fluid channels between the pilot valve seat member and the pilot valve element when the pilot valve unit is in an open-valve-state at three or more locations so as to be separated by equal angles. Each recess has the same shape.