The conventional device for flow rate and pressure multiple control is a combination of a flow rate valve and a pressure relief valve. For the pressure control, a hydraulic bridge can also be used instead of using a pressure relief valve. In this paper, a special hydraulic bridge was developed to undertake pressure control in a pressure compensated flow rate valve and thus a new type of P-Q control valve is constructed. The pressure control in this P-Q control valve is a hydraulic bridge formed by the serial connection between a metering orifice and a drain orifice. The contour of the valve port has a significant effect on the linearity of the output pressure. Theoretical analysis shows that the linear pressure output characteristic corresponds to a valve port contour of a hyperbolic. Due to the difficult machining of this hyperbolic contour, a multiple line with two segment lines is used to approximate the valve port contour for linear pressure output. The pressure bridge is constructed in a 2D P-Q control valve and an experimental investigation is carried out. It is demonstrated that linearity of the output pressure is greatly improved by using the multiple segment line contour of the valve port and it is demonstrated that the output pressure is not sensitive to the variation of the temperature. With the introduction of the pressure control bridge, the P-Q valve is indeed greatly simplified.

Keywords: flow rate and pressure multiple control, pressure compensated flow valve, contour of valve port, linearity