Fuel system

Details Fuel system Fuel system

1999-10-08

2001-05-29

Moulis, Thomas N. (Department: 3747)

Internal-combustion engines

Charge forming device

Fuel injection system

Reexamination Certificate

active

06237568

ABSTRACT:

This invention relates to a fuel system for use in supplying a fuel of the type which is viscous at relatively low temperatures to a combustion space of an associated internal combustion engine of the compression ignition type. The invention is particularly applicable to a fuel system of the common rail type.
A typical common rail system for use with a viscous fuel is illustrated in FIG.
1
and comprises a fixed displacement fuel pump
5
arranged to charge a common rail
6
to a desired high pressure. A plurality of individually actuable fuel injectors
7
are connected to the common rail
6
to permit delivery of fuel from the common rail
6
to the combustion spaces of a compression ignition internal combustion engine. In order to control the fuel pressure within the common rail
6
, the quantity of fuel supplied to the fuel pump
5
is controlled using a throttle to limit the rate at which fuel can flow to the pump
5
. If desired, appropriate non-return valves may be used to prevent fuel flow through the pump
5
in the reverse direction.
The throttle illustrated in
FIG. 1
comprises a throttle member
1
which is linearly displaceable within a housing
2
to vary the effective dimensions of an annular orifice
3
, thus restricting the rate at which fuel can flow along a supply passage
4
towards the fuel pump
5
. Movement of the throttle member
1
is conveniently controlled by an appropriate linear travel proportional solenoid. A seal member
8
forms a substantially fluid tight seal between the throttle member
1
and the housing
2
.
In use, viscous fuel flows through the supply passage
4
around the exposed part of the throttle member
1
. If it is desired to adjust the fuel flow rate to adjust the rate at which fuel is supplied by the pump
5
to the common rail
6
to which the fuel injectors
7
are connected, then the axial position of the throttle member
1
is adjusted. If the throttle member
1
is retracted by a small distance, a small quantity of fuel may be drawn with the throttle member
1
past eh seal member
8
. These traces of fuel may dry out leaving deposits on the throttle member
1
which may cause wear, impair movement of the throttle member
1
and may cause further leakage to occur.
It is an object of the invention to provide a fuel system for use with viscous fuels in which the effects of this disadvantage are reduced.
According to the present invention there is provided a fuel system for use with viscous fuels comprising a housing defining a supply passage through which fuel can flow, in use, from a source of viscous fuel towards a fuel pump, and a throttle member located within the housing and arranged to control the rate of fuel flow along the supply passage, wherein the throttle member is angularly adjustable within the housing to adjust the permitted fuel flow rate.
The throttle member is conveniently arranged to be driven by a rotary travel type solenoid arrangement.
In such an arrangement, as the throttle member does not move in an axial direction, the risk of fuel being drawn past a seal member as a result of adjustment of the throttle is reduced, hence the risk of wear, impaired performance and additional leakage is reduced.


REFERENCES:
patent: 3896194 (1975-07-01), Martin
patent: 4554946 (1985-11-01), Poole

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