Balanced pressure fuel valve

Abstract

Abstract A hydraulic fuel valve assembly which equalizes the pressure of fluid at the hydraulic cylinder during the closed-valve condition with the pressure of fuel at the nozzle region, to thereby assure that the hydraulic cylinder is always full and to minimize variations in the force that must be applied by the hydraulic piston when fuel pressure varies. The valve assembly includes a passageway connecting the fuel supply line to the nozzle region of the valve, and a channel leading to the hydraulic cylinder to supply pressurized fuel to it. A check valve is located along the channel to prevent the flow of fluid out of the hydraulic cylinder when it is highly pressurized during valve opening. In a valve wherein a fluid other than fuel is employed in the hydraulic cylinder, a bellows or sealed piston is installed in the channel between the check valve and the fuel line to prevent mixing of the hydraulic fluid and the fuel. The valve assembly includes a valve body that forms the hydraulic cylinder, and a separate valve insert that contains a valve plunger and an insert housing that defines the valve seat and that limits plunger movement away from the seat, to thereby enable testing and adjustment prior to complete valve assembly. eBACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to valves and, more particularly, to hydraulically actuated valves. 2. Description of the prior Art One type of fuel valve employs an actuator such as a piezoelectric type whose limited motion is amplified by a hydraulic piston. The hydraulic piston has a large diameter so it can pump substantial amounts of fluid along a hydraulic cylinder. The hydraulic fluid moves a plunger of small diameter by a substantial distance to open the valve. The piezoelectric or other actuator generally must supply a pumping force sufficient to overcome a spring preload that assures that the valve will normally be closed, plus any differential pressure between the pressure of fuel at the lower end of the valve plunger and the pressure of fluid in the hydraulic cylinder prior to energization of the activator. In order to minimize the force that must be supplied by the actuator, it is desirable that the fluid pressure in the hydraulic cylinder during the valve closed condition always be approximately equal to the pressure of fuel acting on the lower end of the plunger. This balancing or equalization of pressures is particularly desirable in the case of engines which supply fuel at a widely variable pressure to permit a wide range of fuel injection rates. Such balancing is also desirable where the fuel pressure may remain stable, but where hydraulic fluid pressure may vary. For example, hydraulic pressure may fall if a temperature increase expands the hydraulic cylinder so that the hydraulic fluid cannot completely fill it, or vice versa depending upon the relative coefficients of expansion of fluid and housing. Hydraulically actuated valves are often constructed with a main housing member that forms the hydraulic cylinder in which the hydraulic piston moves, and which also forms the slider bearing hole along which the plunger slides. Additional housing members fastened to the main housing member form the valve seat and a stop that limits plunger movement during opening of the valve. This distance which the plunger moves between its open and closed states must be precisely controlled. It would be desirable to be able to test plunger operation to check for pRoper valve seating, proper opening distance and/or through flow of fuel, and smooth valve sliding, and to make appropriate adjustments, prior to assembling the complete valve.

Inventors

• 👤 M Lilley

Bibliographic Details