Advance arrangement

Details Advance arrangement Advance arrangement

1999-11-23

2001-06-12

Moulis, Thomas N. (Department: 3747)

Internal-combustion engines

Charge forming device

With fuel pump

Reexamination Certificate

active

06244252

ABSTRACT:

This invention relates to an advance arrangement for use in controlling the timing of fuel delivery by a high pressure fuel pump.
A rotary distributor high pressure fuel pump conveniently includes an advance arrangement for use in controlling the timing of fuel delivery by the pump, and hence for controlling the timing of commencement of fuel injection through injectors associated with the pump. The advance arrangement typically comprises an angularly adjustable cam ring having a cam surface with which one or more plungers cooperate, in use. The position of the cam ring is adjustable by means of an advance piston which cooperates with a peg secured to the cam ring such that axial movement of the piston causes angular movement of the cam ring. The advance piston may be spring biased towards a first position, fuel under pressure being applied to the piston to move the piston against the spring biasing towards a second position. In a more complex arrangement, the advance piston may be of the servo-advance type. The fuel pressure applied to the advance piston is typically associated with engine speed, thus the timing of fuel injection is associated with engine speed.
It is an object of the invention to provide an advance arrangement in which corrections for other factors, for example air temperature or density, altitude or fuel cetane number, can be made to the timing of fuel delivery.
According to the present invention there is provided an advance arrangement comprising an advance piston slidable within a bore under the action of the fuel pressure within a control chamber, a surface associated with the piston being exposed to the fuel pressure within the control chamber, the control chamber communicating, through a restricted flow passage, with a low pressure fuel volume, and a valve operable to vary the restriction to flow formed by the restricted flow passage.
Conveniently, the valve may be a solenoid actuable valve.
The advance piston may simply comprise a piston slidable within a bore, or may comprise a servo-advance piston having a servo piston slidable within the advance piston controlling the position of the advance piston.


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