Flow control valve

Claim 2

In a control system for fluid operated equipment having an error signal generator for providing an error signal by comparing a command signal representing a desirable value signal with an actual value signal of a controllable variable, and having a controller for adjusting and amplifying said error signal to provide an amplified error signal; a flow control valve for controlling fluid flow therethrough in accordance with said amplified error signal, said fluid-operated equipment being operated by fluid discharged from said flow control valve at a controlled flow rate, a detecting device for detecting the actual value of said controllable variable and transmitting said actual value signal back to said comparator, said flow control valve comprising means for controlling fluid flow by adjusting a valve opening in accordance with said amplified error signal and means for controlling a pressure difference between the upstream and downstream sides of said flow control valve in accordance with said command signal, said means for controlling fluid flow including an inlet conduit for receiving pressurized fluid flow therein and an outlet conduit connnected to said inlet conduit for discharging fluid at a controlled flow rate to said fluidoperated equipment, and said means for controlling the pressure difference between the upstream and downstream sides of said flow control valve in response to said command signal including a cylinder communicating at one end thereof with said inlet conduit and at the other end thereof with said outlet conduit, and having A drain opening provided in a wall of said cylinder, a return conduit connected to said drain opening, a spool slidably inserted in said cylinder to adjust the effective area of said drain opening, a spring disposed in said cylinder for urging said spool in one direction, and a spool actuating device operatively connected to said spool and adapted to receive said command signal to apply force on said spool in accordance with said command signal, whereby said spool controls the effective area of said drain opening at a position where a force caused by said pressure difference, a force of said spring and a force caused by said command signal are balanced.

Claim 3

A flow control valve as claimed in claim 1, wherein said means for controlling fluid flow further includes a valve device disposed between said inlet conduit and outlet conduit, and a valve actuating device operatively connected to said valve device and adapted to receive said amplified error signal to adjust said valve opening in accordance with said amplified error signal.

Claim 4

In a control system for fluid operated equipment having an error signal generator for providing an error signal by comparing a command signal representing a desirable value signal with an actual value signal of a controllable variable, and having a controller for adjusting and amplifying said error signal to provide an amplified error signal; a flow control valve for controlling fluid flow therethrough in accordance with said amplified error signal, said fluid-operated equipment being operated by fluid discharged from said flow control valve at a controlled flow rate, a detecting device for detecting the actual value of said controllable variable and transmitting said actual signal back to said comparator, said flow control valve comprising means for controlling fluid flow by adjusting a valve opening in accordance with said amplified error signal and means for controlling a pressure difference between the upstream and downstream sides of said flow control valve in accordance with said command signal, and further comprising an inlet conduit for receiving pressurized fluid flow therein, an outlet conduit connected to said inlet conduit for discharging fluid at a controlled flow rate to said fluid-operated equipment, a valve device disposed between said inlet conduit and outlet conduit, a valve actuating device operatively connected to said valve device and adapted to receive said amplified error signal to adjust valve opening in accordance with said amplified error signal, a cylinder communicating at one end thereof with said inlet conduit and at the other end thereof with said outlet conduit, and having a drain opening provided in a wall of said cylinder, a return conduit connected to said drain opening, a spool slidably inserted in said cylinder to adjust the effective area of said drain opening, a spring disposed in said cylinder for urging said spool in one direction, a spool actuating device operatively connected to said spool and adapted to receive said command signal to apply force on said spool urging it in the same one direction in accordance with said command signal, whereby said spool controls the effective area of said drain opening at a position where a force caused by said pressure difference in another direction, a force of said spring and a force caused by said command signal are balanced.

Claim 5

In a control system for fluid operated equipment having an error signal generator for providing an error signal by comparing a command signal representing a desirable value signal with an actual value signal of a controllable variable, and having a controller for adjusting and amplifying said error signal to provide an amplified error signal; a flow control valve for controlling fluid flow therethrough in accordance with said amplified error signal, said fluid-operated equipment being operated by fluid discharged from said flow control valve at a controlled flow rate, a detecting device for detecting the actual value of said controllable variable and transmitting said actual signal back to said comparator, said flow control valve comprising means for controlling fluid flow by adjusting a valve opening in accordance with said amplified error signal and means for controlling a pressure difference between the upstream and downstream sides of said flow control valve in accordance with said command signal, and further comprising an inlet conduit for receiving pressurized fluid flow therein, an outlet conduit connected to said inlet conduit for discharging fluid at a controlled flow rate to said fluid-operated equipment, a valve device disposed between said inlet conduit and outlet conduit, a valve actuating device operatively connected to said valve device and adapted to receive said amplified error signal to adjust valve opening in accordance with said amplified error signal, a cylinder communicating at one end thereof with said inlet conduit and at the other end thereof with said outlet conduit, and having a drain opening provided in a wall of said cylinder, a return conduit connected to said drain opening, a spool slidably inserted in said cylinder to adjust the effective area of said drain opening, a spring disposed in said cylinder for urging said spool in one direction, a spool actuating device operatively connected to said spool and adapted to receive said command signal to apply force on said spool urging it in the same one direction in accordance with said command signal, whereby said spool controls the effective area of said drain opening at a position where a force caused by said pressure difference in another direction, a force of said spring and a force caused by said command signal are balanced.

Claim 6

A flow control valve as claimed in claim 1, wherein said valve opening is proportional to the value of said amplified error signal and said pressure difference is proportional to the square of said command signal.