A control valve or system of control valves governs fluid flow by digitally comparing a feedback signal from a fluid control loop with a command signal corresponding to a desired flow rate in a high pressure operating fluid flow line In the preferred embodiment, a control valve system, such as a pressure relief valve, is operated under the control of a digital computer The pressure relief valve is operated at a control pressure to regulate flow in an operating hydraulic system The control pressure chamber is coupled to a relief line through a control pressure reduction valve and to a control pressure enhancement valve which is in communication with the operating line of fluid flow A feedback signal indicating actual control pressure, flow rate or load position is compared with a command control pressure, flow rate or position Preferably, the results of several comparisons are averaged together to provide an error correction signal The error correction signal selectively actuates the pressure enhancement and pressure reduction valves to maintain the desired control pressure, flow rate or load position The system preferably includes a deactuating means which limits actuation of the control pressure enhancement and reduction valves to the duration of pulses of a width related to the magnitude of the error correction signal

Digital fluid pressure flow rate and position control system

An electro/pneumatic proportional valve having a housing defining an upper and lower chamber separated by an annular web. An inlet port and exhaust port concentric with the annular web are provided in said lower chamber while an outlet port is provided in the upper chamber. An exhaust cylinder is resiliently disposed through the exhaust port and has a radial flange engaging said annular web to occlude the annular web's central opening. The exhaust cylinder also has an axial bore passing therethrough and exiting through the exhaust port. A piston disposed in the upper chamber has a pintle which is operative to engage the exhaust cylinder with the displacement of the piston and occlude the exhaust cylinder's axial bore. Pilot valves are provided to pressurize the upper chamber in response to a pulse train signal displacing the piston towards the web. The displacement of the piston causes the pintle to engage the exhaust cylinder and unseat it from the annular web.

An electro/pneumatic proportional valve

1. Brake pressure regulator for pneumatic brakes of vehicles, particularly of rolling stock, with at least one electrically operable solenoid (4), valve (2, 3), a compressive stress transformer (4), whixh produces an actual-value signal proportionnal to the brake pressure to be regulated, a desired pressure value transmitter (S ; 16), a comparator (5) for producing a deviation signal between the actual-value signal and a desired-value signal, a regulator (6) connected to the comparator and an arrangement (7, 8) for producing an adjusting signal for the solenoid valve, characterized in that the arrangement (7, 8) for producing the adjusting signal controls the solenoid valve (2, 3) in such a way that its valve tappet adopts intermediate positions between the completely open and completely closed states of the solenoid valve within a certain area, which positions are continuously ajustable over as long a time as desired.

Pressure control system for pneumatic vehicle brakes, in particular of rail vehicles

A hydraulic control method which includes a step of changing the time rate of introduction per a predetermined unit time of pressurized oil into an oil passage connected to a hydraulically-operated load device, such as a clutch of an automatic transmission, from a first time rate to a second time rate, thereby changing the time-based average oil pressure inside the oil passage from a first oil pressure value to a second oil pressure value. The time rate of introduction of the pressurized oil into the oil passage is changed from the first time rate to the second time rate via a third pressurized oil introduction time rate corresponding to a third oil pressure value different from the first and second oil pressure values. If the second oil pressure value is greater than the first oil pressure value, the third pressurized oil introduction time rate is substantially 100%. If the second pressure value is smaller than the first, the third time rate is substantially 0%. Preferably, the step of pressurized oil introduction into the oil pressure at the third pressurized oil introduction time rate is followed by at least one step of introducing the pressurized oil into the oil passage at a pressurized oil introduction time rate corresponding to an oil pressure value different from the third oil pressure value. Preferably, the pressurized oil introduction time rates are temperature-corrected in accordance with the pressurized oil temperature.

Method of duty-ratio control for hydraulically actuated slip control lock-up clutch and transmission

Apparatus for continuously controlling an electrically-actuated solenoid valve which regulates the fluid pressure conveyed to a brake cylinder. The solenoid valve is designed for intermittent operation. A pressure transducer senses and generates an actual value signal, which is proportional to the pressure to be regulated. A set value generator produces a select set value signal. A comparator device generates a pulse-type control signal having a variable width repetition rate within a certain pressure range for the solenoid valve in accordance with the difference between the actual value signal and the set value signal. In order to regulate the pressure more precisely and more quickly, without dependence on outer influences, the comparator device generates the control signal for controlling the solenoid valve within a predetermined initial pressure range, in accordance with the actual value pressure sensed by the pressure transducer in such a way that the solenoid valve is slightly opened by being pulsed from a closed-valve position.

Apparatus for the continuous control of solenoid valves which are normally designed for intermittent operation

The precise control of pressure within a container is achieved by continuous pulsing of inlet and outlet solenoid valves operating about average value levels. A comparator (1) operates upon a preset reference level signal (Vc) and a feedback signal from a pressure transducer (2). A signal generator (3) produces a triangular wave output of constant frequency that is amplified (4) before transmission to an adder circuit (5). The adder circuit output is of variable d.c. level with the triangular wave from superimposed and is used to drive inlet solenoid valves (EVA, EVA') and outlet valves (EVE, EVE') coupled to the pressure container (C). In operation two valves (EVA, EVE) are set to respond to a higher level than the other valves to operate when large erras exist.

Lavenu Raymond

Papers

Inlet and outlet valve control arrangement - uses DC error signal with superimposed triangular waveform to minimise operating error (BE020676)

Verfahren und einrichtung zur steuerung von einlass- und auslassventilen