Damper valve for hydraulic power steering device

摘要

A damper valve (30) for a hydraulic power steering device (1) is disposed in a hydraulic oil circuit connecting an oil passage changing-over valve (6) in a gear box (2) and left and right oil chambers of a power cylinder (10). It is provided with a piston valve (46) which is opened by through-flow of hydraulic oil returned back to the oil passage changing-over valve (6) from either one of the left and right chambers of the power cylinder, and a check valve which is disposed in a valve body (36) of the piston valve and which allows only hydraulic oil supplied from the oil passage changing-over valve to either one of the left and right chambers of the power cylinder to flow through the check valve. The piston valve is structured such that a throttle oil passage is formed by through flow of the returned hydraulic oil having an oil pressure of a predetermined value or less, and a fully opened oil passage is formed by through flow of the returned hydraulic oil having an oil pressure of more than the predetermined value. Oil passages for the returned-back hydraulic oil are formed in the valve body of the piston valve.