Fuel injector

Details Fuel injector Fuel injector

1998-12-02

2001-10-09

Scherbel, David A. (Department: 3752)

Fluid sprinkling, spraying, and diffusing

With means to vibrate or jiggle discharge

By electric transducer

C239S533300, C239S533800, C239S533900, C239S585100

Reexamination Certificate

active

06299074

ABSTRACT:

This invention relates to a fuel injector for use in supplying fuel under pressure to a cylinder of an associated compression ignition internal combustion engine. In particular, the invention relates to an injector suitable for use in a fuel system of the type in which an accumulator or common rail is charged with fuel by a high pressure fuel pump, a plurality of individually actuable injectors being arranged to receive fuel from the accumulator or common rail.
EP-A-0767304 describes an injector suitable for use in such a fuel system. The injector comprises a valve needle which is engageable with the seating. Part of the valve needle is exposed to the fuel pressure within a control chamber, the pressure of fuel within the control chamber controlling movement of the needle. An electromagnetically actuated valve is provided to control the fuel pressure within the control chamber.
It is desirable, for example where the injector is to be used with a four valve cylinder head, to use an injector of relatively small diameter. Injectors including electromagnetically actuated control valves are generally of relatively large diameter as the electromagnetic actuators are relatively large.
According to a first aspect of the invention there is provided an injector comprising a valve needle slidable in a bore and moveable under the influence of the fuel pressure within a control chamber defined, in part, by a surface associated with the needle, and a piezoelectrically actuated valve controlling the fuel pressure within the control chamber.
The use of a piezoelectrically actuated valve rather than an electromagnetically actuated valve permits the diameter of the injector to be reduced as piezoelectric actuators of small dimensions are available.
One disadvantage of using a piezoelectric actuator is that the length of the piezoelectric element can vary, in use, due to temperature, wear and drift by an amount of the same order as is achieved when an electric field is applied to the material, in use. In order to compensate for such changes, the piezoelectrically actuated valve conveniently comprises a valve member and a piezoelectric actuator, the piezoelectric actuator including a piezoelectric element spring biased towards the valve member, and a damping arrangement damping movement of the piezoelectric element under the action of the spring.
In such an arrangement, the spring causes movement of the piezoelectric element to compensate for changes in the length of the piezoelectric element, the damping arrangement limiting the rate at which the spring moves the piezoelectric element so that the rapid changes in length caused by applying an electric field to the piezoelectric element to allow movement of the valve member are not compensated for by the action of the spring.
According to another aspect of the invention there is provided a fuel injector comprising a valve needle slidable in a bore and moveable under the influence of the fuel pressure within a control chamber defined, in part, by a surface associated with the needle, and a control valve arranged to control the fuel pressure within the control chamber, wherein the control chamber is supplied with fuel through a passage provided in the valve needle.
By supplying fuel to the control chamber through a passage provided in the valve needle rather than a passage provided in a housing within which the needle is slidable, the diameter of the housing, and hence the injector, can be reduced.


REFERENCES:
patent: 4327688 (1982-05-01), Lowther
patent: 4584980 (1986-04-01), Weiger et al.
patent: 4725002 (1988-02-01), Trachte
patent: 4826080 (1989-05-01), Ganser
patent: 5011082 (1991-04-01), Ausiello et al.
patent: 5419492 (1995-05-01), Gant et al.
patent: 5673669 (1997-10-01), Maley et al.
patent: 5810255 (1998-09-01), Itoh et al.
patent: 5860597 (1999-01-01), Tarr
patent: 195 19 192 (1996-06-01), None
patent: 0 767 304 (1997-04-01), None

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