Infinitely variable hydromechanical timing control

In a fuel supply system for an internal combustion engine of the type wherein a supply pump supplies fuel to fuel injectors at a pressure that is controlled in accordance with engine operating conditions via a common first supply rail and supplies timing fluid to the fuel injectors via a common second supply rail, an infinitely variable hydromechanical timing valve comprising a valve barrel having an axial bore and a timing valve plunger mounted for reciprocation within the axial bore of the valve barrel, at least one timing spring acting on a first end of the timing valve plunger, and an opposite, second end of the timing valve plunger being in communication with the first supply rail;

• wherein an outlet of the supply pump is directly connected to a timing fluid inlet at a first location along the length of the axial bore and said second supply rail is connected to a timing fluid outlet at a second location that is axially spaced along the length of the axial bore relative to said first location;
• wherein said timing valve plunger and said timing fluid outlet coact to form a variable orifice means for varying a flow-through cross section for timing fluid traveling from said timing fluid inlet to said timing fluid outlet as a function of movement of said timing valve plunger toward and away from said first and second locations, whereby the position of the timing valve plunger in the axial bore of the valve barrel, and therefore, the flow-through cross section of the variable orifice means, is a function of rail pressure in said first supply rail, and spring rate and spring preload of said at least one timing spring.