Hydraulic valve

A two-port hydraulic valve comprising:

• a housing including first and second ports, a first hydraulic chamber and a second hydraulic chamber, wherein the first and second hydraulic chambers are communicated with the first and second ports, respectively;
• a valve seat located in the first hydraulic chamber, wherein the valve seat has a tubular shape including a central passage and an open end, wherein the open end includes a flat valve seat contact surface;
• a valve member located in the second hydraulic chamber and including a valve member contact surface;
• and
• a biasing member that generates a biasing force to press the valve seat and the valve member so that the valve member contact surface comes in planar contact with the flat valve seat contact surface,
• wherein, when hydraulic pressure of the first hydraulic chamber is higher than that of the second hydraulic chamber, the hydraulic pressure of the first hydraulic chamber acts on the valve member through the central passage of the valve seat to separate the valve member from the valve seat against the biasing force of the biasing member so that the first hydraulic chamber and the second hydraulic chamber come into fluidal communication,
• wherein, when hydraulic pressure of the second hydraulic chamber is higher than that of the first hydraulic chamber, a hydraulic pressure difference between the first hydraulic chamber and the second hydraulic chamber acts on the valve seat to separate the valve seat from the valve member against the biasing force of the biasing member so that the first hydraulic chamber and the second hydraulic chamber come into fluidal communication,
• wherein the open end of the valve seat includes the flat valve seat contact surface that includes at least one flat and annular surface for the planar contact with the valve member contact surface, and an annular recess located adjacent to the flat valve seat contact surface and incapable of contacting the valve member contact surface, and
• wherein the open end of the valve seat includes a communication channel, which fluidically communicates the second hydraulic chamber with the recess, and when the valve seat contact surface is in contact with the valve member contact surface, a gap formed by the communication channel and the valve member has a smaller volume than a gap formed by the recess and the valve member.