Fluid sprinkling – spraying – and diffusing – Processes – Of fuel injection
Reexamination Certificate
1998-12-11
2001-08-21
Kashnikow, Andres (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
Of fuel injection
C239S088000, C239S091000, C417S505000
Reexamination Certificate
active
06276610
ABSTRACT:
TECHNICAL FIELD
This invention relates to a control valve for use in a diesel fuel injection system.
BACKGROUND ART
Engine exhaust emission regulations are becoming increasingly restrictive. One way to meet emission standards is to rate shape the quantity and timing of the fuel injected into the combustion chamber to match the engine cycle. Effective rate shaping may result in reduced levels of particulate and oxides of nitrogen in the engine exhaust. Further, effective rate shaping that injects fuel slower during the early phase of the combustion process results in less engine noise.
Existing rate shaping techniques attempt to control injection rates by making various modifications to the injector nozzle assembly. Although these existing rate shaping techniques have been employed in many applications that have been commercially successful, there is a need for a rate shaping technique that allows more precise rate shaping than the existing modified injector nozzle assemblies.
DISCLOSURE OF INVENTION
It is, therefore, an object of the present invention to provide pumps and injectors having a control valve capable of shaping the injection rate.
It is another object of the present invention to provide a method for operating a control valve with a stepped spring force for rate shaping.
In carrying out at least one of the above objects, a pump for a fuel injection system is provided. The pump comprises a pump body having a pumping chamber, a fuel inlet for supplying fuel to the pumping chamber, an outlet port, and a control valve chamber between the pumping chamber and the outlet port. The pump further comprises a plunger disposed in the pumping chamber, and an actuatable control valve disposed in the control valve chamber for controlling fuel. The control valve is moveable over a stroke between an open position and a closed position. The stroke range includes a rate shape position between the open position and the closed position.
A valve stop is adjacent to the control valve chamber. A control valve spring arrangement biases the control valve toward the open position. An armature is located at the control valve. A stator near the armature includes an actuator operable to urge the control toward the closed position against the bias of the control valve spring arrangement.
The control valve spring arrangement is configured to provide a first spring force when the control valve is between the closed position and the rate shape position. Further, the control valve spring arrangement is configured to provide a second spring force, which is less than the first spring force, when the control valve is between the rate shape position and the open position. Further, a stroke portion from the closed position to the rate shape position is sufficiently small such that controlled injection rate shaping is provided when the control valve is at the rate shape position.
In a preferred embodiment, the stroke portion between the closed position and the rate shape position is at most about 0.03 millimeters. Further, in a preferred embodiment, the stroke range is at least about 0.1 millimeters, or approximately three times the rate shape stroke portion.
In one embodiment, the control valve spring arrangement comprises a primary spring and a secondary spring. The primary spring biases the control valve toward the open position over a limited portion of the stroke range between the closed position and the rate shape position. The secondary spring biases the control valve toward the open position throughout the stroke range. The secondary spring cooperates with the primary spring to produce the first spring force. The secondary spring acts unassisted to produce the second spring force.
In another embodiment, the primary spring biases the control valve toward the open position throughout the stroke range; and, the secondary spring biases the control valve toward the closed position over a limited portion of the stroke range between the rate shape position and the open position. Accordingly, the primary spring acts unassisted to produce the first spring force, while the primary spring opposes the secondary spring to produce the second spring force. The secondary spring may be located within a main body of the valve stop and bias a stop member of the valve stop toward the control valve such that the control valve contacts the stop member when the control valve is between the rate shape position and the open position. Preferably, the stop member has an abutment surface for contacting the control valve; and a vent orifice extends from the abutment surface through the stop member to allow fluid flow therethrough.
In yet another embodiment, a single spring biases the control valve toward the open position over a limited portion of the stroke range between the closed position and the rate shape position. The single spring produces the first spring force, and the second spring force is substantially equal to zero.
Further, in carrying out at least one of the above objects, a fuel injector is provided. The fuel injector comprises an injector body having a pumping chamber and a control valve chamber, a plunger disposed in the pumping chamber, and an actuatable control valve disposed in the control valve chamber for controlling fuel. The control valve is moveable over a stroke range between an open position and a closed position. The stroke range includes a rate shape position between the open position and the closed position. A valve stop is adjacent to the control valve chamber. A control valve spring arrangement biases the control valve toward the open position. An armature is at the control valve. A stator near the armature includes an actuator operable to urge the control valve toward the closed position against the bias of the control valve spring arrangement.
The control valve spring arrangement is configured to provide a first spring force when the control valve is between the closed position and the rate shape position. Further, the control valve spring arrangement is configured to provide a second spring force that is less than the first spring force when the control valve is between the rate shape position and the open position. A stroke portion between the closed position and the rate shape position is sufficiently small such that controlled injection rate shaping is provided when the control valve is at the rate shape position.
Both pumps and injectors of the present invention are preferably of the outwardly opening type in which the control valve contacts the valve stop when the control valve is in the open position.
Still further, in carrying out at least one of the above objects, a method for operating a control valve with a variable spring force for rate shaping is provided. The method comprises fully closing the control valve to allow initial injection pressure to build up in the pumping chamber. The control valve is fully closed by supplying a first current to the actuator to cause the control valve to overcome a first spring force in the opening direction. The method further comprises partially opening the control valve to a rate shape position by supplying a second current to the actuator. The second current is less than the first current and causes the control valve to overcome a second spring force. The second spring force is less than the first spring force. Thereafter, the control valve is fully closed to allow main injection pressure to build up in the pumping chamber. At the end of injection, the control valve is fully opened.
The advantages associated with embodiments of the present invention are numerous. For example, control valves made in accordance with the present invention for pumps or injectors allow effective rate shaping by controlling the pressure supplied to the pump outlet or injector nozzle assembly of a unit injector. Rate shaping at the control valve advantageously allows more precise rate shaping than some existing rate shaping techniques that attempt to rate shape with a modified injector nozzle assembly. Injection pressure control is used instead of throttling at the n
Brooks & Kushman P.C.
Diesel Technology Company
Kashnikow Andres
Kim Christopher S.
LandOfFree
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