Relief valve

A relief valve, comprising:

• a housing including a pilot chamber and an oil chamber therein;
• a valve body configured to allow or block communication between an inflow passage into which a hydraulic oil flows and an outflow passage through which the hydraulic oil flows out, the valve body including a first surface facing the inflow passage, a second surface facing the oil chamber, and a through passage connecting the first surface to the second surface;
• an urging member configured to urge the valve body toward the inflow passage;
• and
• a piston including a first piston member configured to press the urging member using a pressure of a pilot oil in the pilot chamber to change an amount of deflection of the urging member;
• wherein
• the first piston member is at least partially located within the oil chamber, and is operable to divide the oil chamber into a first oil chamber and a second oil chamber;
• the first piston member includes a first pressure receiving surface configured to receive a pressure in a first axial direction of an axial direction from the hydraulic oil in the first oil chamber, and a second pressure receiving surface configured to receive a pressure in a second axial direction of the axial direction from the hydraulic oil in the second oil chamber;
• the housing further includes, therein, an urging member chamber connected to the outflow passage and a back pressure chamber connected to the outflow passage;
• and
• the first piston member includes:
• a third pressure receiving surface configured to receive a pressure in the first axial direction from the hydraulic oil in the back pressure chamber;
• and
• a fourth pressure receiving surface configured to receive a pressure in the second axial direction from the hydraulic oil in the urging member chamber.

A relief valve, comprising:

• a housing including a pilot chamber and an oil chamber therein;
• a valve body configured to allow or block communication between an inflow passage into which a hydraulic oil flows and an outflow passage through which the hydraulic oil flows out, the valve body including a first surface facing the inflow passage, a second surface facing the oil chamber, and a through passage connecting the first surface to the second surface;
• an urging member configured to urge the valve body toward the inflow passage;
• and
• a piston including a first piston member configured to press the urging member using a pressure of a pilot oil in the pilot chamber to change an amount of deflection of the urging member;
• wherein
• the first piston member is at least partially located within the oil chamber, and is operable to divide the oil chamber into a first oil chamber and a second oil chamber;
• the first piston member includes a first pressure receiving surface configured to receive a pressure in a first axial direction of an axial direction from the hydraulic oil in the first oil chamber, and a second pressure receiving surface configured to receive a pressure in a second axial direction of the axial direction from the hydraulic oil in the second oil chamber;
• the housing further includes, therein, an atmospheric open chamber that is open to an atmosphere;
• the piston further includes a second piston member arranged in the second axial direction with respect to the first piston member and configured to press and move the first piston member in the first axial direction;
• and
• the second piston member includes an atmospheric open surface facing the atmospheric open chamber in the first axial direction, and a pilot pressure receiving surface facing the pilot chamber in the second axial direction.

A relief valve comprising:

• a housing including a pilot chamber, an oil chamber, and an atmospheric open chamber therein;
• a valve body configured to allow or block communication between an inflow passage into which a hydraulic oil flows and an outflow passage through which the hydraulic oil flows out, the valve body including a first surface facing the inflow passage, a second surface facing the oil chamber, and a through passage connecting the first surface to the second surface;
• an urging member configured to urge the valve body toward the inflow passage;
• and
• a piston including a first pilot piston member configured to change an amount of deflection of the urging member using a pressure of a pilot oil in the pilot chamber;
• wherein
• a surface of the first pilot piston member in a second axial direction of an axial direction faces the pilot chamber;
• a surface of the first pilot piston member in a first axial direction of the axial direction faces the atmospheric open chamber;
• the piston further includes a second pilot piston member arranged in the first axial direction with respect to the first pilot piston member;
• the housing further includes, therein, a back pressure chamber facing a surface of the second pilot piston member in the first axial direction and connected to the outflow passage;
• and
• an area of the surface of the second pilot piston member in the first axial direction is smaller than an area of the first pilot piston member in the second axial direction.