relief valve

Abstract

A spool valve body (18) has an axial one side provided with a pressure receiving part (18A), one side of which opens and the other side of which closes, for receiving pressures in said supply passage (13A), and a radial hole (18B) that radially communicates an inside and an outside of the pressure receiving part (18A). An annular gap (22) for the hydraulic oil to flow therein at the opening of the spool valve body (18) is formed between an inner peripheral surface of one side of the spool sliding bore (14A) adjacent to the displacement regulating part (14B) and an outer periphery of the peripheral wall of the pressure receiving part (18A). At the opening of the spool valve body (18), a first oil passage (24) in which the hydraulic oil flows to the tank port (17) from the supply passage (13A) through the pressure receiving part (18A) and the radial hole (18B) and a second oil passage (25) in which the hydraulic oil flows to the tank port (17) through the axial gap (23) and the annular gap (22) between the displacement regulating part (14B) and the spool valve body (18), are formed.

Description

technical field [0001] The present invention relates to a relief valve suitable for use in hydraulic equipment such as construction machinery. Background technique [0002] Generally, a construction machine represented by a hydraulic excavator is equipped with a relief valve in order to suppress the occurrence of excess pressure in a hydraulic circuit due to breakage or damage of hydraulic equipment. Such a conventional relief valve is configured to open the valve when excess pressure is generated to release the excess pressure to the tank side. In addition, as such a relief valve, there is known a structure in which a spool sliding hole is provided in the valve case, and a spool valve element fitted in the spool sliding hole is slid and displaced in the axial direction to thereby displace the spool valve. The above-mentioned residual pressure is released to the tank side (for example, refer to Patent Documents 1 and 2). [0003] prior art literature [0004] patent docum...

AI Technical Summary

Problems solved by technology

[0008] If a foreign matter is bitten between the above-mentioned displacement restricting part and the spool valve core, the spool valve core cannot be completely closed.

Therefore, the pressurized oil in the hydraulic circuit leaks to the tank port side of the relief valve, and the pressure of the pressurized oil cannot be stably controlled.

In addition, the foreign matter bitten once will not be discharged by the flow of oil, but will remain in a state of adhering between the above-mentioned displacement restricting part and the spool valve element, and may damage the pressure setting function of the relief valve. sex

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