Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Reexamination Certificate
2000-06-05
2002-07-30
Doerrler, William C. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
C239S533400, C239S584000, C239S585100
Reexamination Certificate
active
06425539
ABSTRACT:
The current invention relates to a control unit for controlling a pressure buildup by a pump unit in a system, wherein the control unit has a control valve and a valve actuation unit connected to the control unit and the control valve is embodied as an inlet that opens in the inlet flow direction, which has a valve body that is supported so that the valve body can move axially in a housing of the control unit and rests against a valve seat of the control valve from the inside when the control valve is closed.
The current invention also relates to an injection system for fuel delivery into a combustion chamber of direct injection internal combustion engines, with a pump unit for building up an injection pressure and then for injecting the fuel into the combustion chamber via a fuel injector.
Finally, the current invention also relates to a process for controlling the pressure buildup by means of a control unit with a control valve and a valve actuation unit connected to the control unit, wherein the control valve is embodied as an inlet valve which opens in the inlet flow direction and has a valve body that is supported so that the valve body can move axially in a housing and rests against a valve seat of the control valve when the control valve is closed.
PRIOR ART
Control units of this kind for controlling the pressure buildup of arbitrary pump units have been disclosed by the prior art. For example, they are used to control the fuel delivery into a combustion chamber of direct injection internal combustion engines. The internal combustion engines have a pump unit for building up an injection pressure and then for injecting the fuel into the combustion chamber via a fuel injector. For example, the injection system of the internal combustion engine can be embodied as a unit injector system (UIS) or as a unit pump system (UPS).
These known control units are usually embodied as solenoid valves. In this connection, the valve actuation unit is embodied as an electromagnet that actuates the control valve. The solenoid valve is open when the valve is not excited. As a result, there is a free through flow from the pump unit to the low-pressure region of the injection system and it is consequently possible for there to be a filling of the pump chamber with fuel during the intake stroke of the pump piston and a return flow of the fuel during the delivery stroke. A triggering of the solenoid valve during the delivery stroke of the pump piston closes this bypass. This leads to a pressure increase in the high-pressure region of the system. Consequently, the pressure buildup in the pump unit can be controlled by means of the control unit.
The control valve is embodied as an inlet valve that opens in the inlet flow direction. Inlet valves usually have a very steep through flow curve with small strokes. In a through flow curve, the course of the through flow through a valve is plotted as a function of the stroke of the valve. Due to the steep course of the through flow curve that inlet valves have with small strokes, even slight fluctuations of the valve stroke lead to relatively large fluctuations in the through flow quantity. Fundamentally, a fluctuation of the through flow quantity with small strokes would have hardly any effect on the total quantity of the medium supplied. However, there are applications in which the through flow quantity through the valve with small valve strokes should be kept as independent of the valve stroke as possible and which must have as flat as possible a course of the through flow curve with small strokes.
For example, an application of this kind is the control of the fuel supply in direct injection internal combustion engines. In these engines, a so-called preinjection is frequently carried out, i.e. a small quantity of fuel is injected into the combustion chamber before the actual main injection. The noise behavior and exhaust behavior of the internal combustion engine can be positively influenced with the aid of the preinjection. One must be able to precisely determine the quantity of the preinjected fuel in order to be able to control the behavior of the internal combustion engine in a deliberate manner. The preinjection takes place with small strokes of the control valve. With the control unit according to the prior art, even slight fluctuations of the valve stroke have large effects on the quantity of the preinjected fuel. In order to be able to determine the preinjection quantity as precisely as possible, it would therefore be advantageous if the through flow curve had a flat course with small strokes.
In order to embody the course of the through flow curve with small strokes so that the flow curve is as flat as possible, the prior art has disclosed controlling the through flow quantity electronically. However, an electronic control is complex and expensive.
The above-mentioned disadvantages of the prior art give rise to an object of the current invention, which is to improve a control unit of the type mentioned at the beginning in such a way that the through flow curve has as flat a course as possible with small strokes of the control valve.
In order to attain this object, based on a control unit of the type mentioned at the beginning, a control unit which is characterized by means of a throttle device which throttles the through flow through the control valve when the control valve is open by a small stroke.
When the control valve of the control unit according to the invention is open by a large stroke, there is a free through flow from the pump unit, through the valve seat of the control valve, to a low-pressure region of a system in which the pressure buildup is intended to be controlled. Consequently, it is possible for there to be a filling of the pump chamber with the supplied medium during the intake stroke of the pump piston and a return flow of the medium during the delivery stroke. Therefore, no pressure is built up in the system.
By triggering the valve actuation unit, the valve piston is moved in the direction of the closed position of the control valve. In this manner, the control valve can be brought into a valve position that is open by a small stroke. When the control valve is open by a small stroke, there is still a through flow, but only a throttled through flow, from the pump unit, through the valve seat of the control valve and the throttle device, to the low-pressure region of the system. Consequently, it is possible for there to be a partial filling of the pump chamber with the supplied medium during the intake stroke of the pump piston and a return flow of the medium during the delivery stroke. A slight pressure is built up in the high-pressure region of the system.
Another triggering of the valve actuation unit during the delivery stroke of the pump piston closes the control valve completely, as a result of which the bypass from the pump unit to the low-pressure region of the system is shut off. This leads to the buildup of a high pressure in the high-pressure region of the system.
During the closing process from a maximal value when the control valve is completely open to the value zero when the control valve is completely closed, the through flow quantity of the medium flowing through the control valve does not decrease sharply. On the contrary, when a small stroke is achieved, a virtually constant small quantity of the supplied medium flows through the control valve until the control valve is completely closed. The course of the through flow curve of the control valve is advantageously very flat with small strokes. This achieves the fact that fluctuations of the valve stroke cause hardly any fluctuations of the through flow quantity. With small strokes, the through flow quantity is virtually independent of the valve stroke.
The throttle device is advantageously integrated into the valve body. This has the advantage that the throttle device does not have to be triggered separately, but, together with the valve body, can be brought from an inactive position when the control valve is completely open into an active position whe
Doerrler William C.
Greigg Ronald E.
Kim Christopher
Robert & Bosch GmbH
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