Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-03-10
2001-10-30
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
Reexamination Certificate
active
06308689
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority based on German Application No. 19910589.8, filed on Mar. 10, 1999, which is incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
The invention relates to an injection valve. It is known to supply internal combustion engines with fuel using fuel injection systems that operate with a very high injection pressure. Such injection systems are commonly referred to known as common rail systems (for Diesel engines) and PDI injection systems (for Otto cycle engines). In conventional injection systems, fuel is pumped with a high-pressure pump into a pressure reservoir common to all cylinders of the engine. Injection valves supply fuel from the reservoir to individual cylinders. The opening and closing of the injection valves, also known as injectors, is conventionally performed electrically or electromagnetically.
The injection valves in conventional systems are generally provided with servo valves that hydraulically operate the opening and closing of the needle of the actual injection valve, i.e., the servo valves determine the beginning and the end of the injection period. The servo valve, in connection with other features of these systems, mainly influences the speed at which the injection valve opens and closes.
For reasons relating to combustion technology, the speed that the injection valve opens is chosen to be different from the speed that the injection valve closes. The injection valve must, in common rail systems for Diesel engines, open slowly under control at the start of the injection period for better mixing of the fuel with the air. On the other hand, the injection valve must close rapidly at the end of the injection so as to prevent carbon deposit formation. Also, the period of the injection must be controllable. In order to optimize the combustion process, it is desirable to minimize pilot injection, i.e., the amount of fuel that is injected before the actual injection.
Uncontrolled opening of the injection valve can lead to violent pressure fluctuations, which are difficult to overcome, in the high-pressure range of the injection nozzle. By appropriate measures such as control throttling in the fuel delivery, the injection can be controlled at the beginning. Control throttling also has the advantage that the requirements regarding valve timing are substantially less stringent.
A disadvantage of these conventional systems and their known manner of operation is that fuel delivery is not controlled only in the initial phase of the injection, but also when a transition is made from the initial phase to the main phase of the injection, which is to take place as rapidly as possible.
SUMMARY OF THE INVENTION
The present invention is directed to providing an injection valve with a control valve such that the initial phase of the injection period can be started with throttling, and eliminating the undesirable effects of throttling later in the injection period.
A servo valve according to the present invention is characterized in that, during the initial phase of the injection period, the servo valve includes a constricted connection to the injection nozzle of the injection system. As the injection continues, when the servo valve opens further, the initially active constriction is bypassed, and a direct connection to the injection nozzle is established.
The present invention is achieved by providing an injection valve for controlling fuel flow from an inlet passage to an injection nozzle. The injection valve comprises a valve body including a valve seat and a bore; a valve element displaceable with respect to the valve body, the valve element sealingly engaging the valve seat and preventing the fuel flow at a closed position of the valve element with respect to the valve body, the valve element including a piston sealingly engaging a wall of the bore in the closed position, a groove confronting the valve body, and a passage having a constriction providing fluid communication between an upstream side of the piston and the groove, the bore having a radially flared portion located at a predetermined length from the groove in the closed position; a control chamber regulating displacement of the valve element with respect to the valve body, displacement less than the predetermined length from the closed position establishing fluid communication between the inlet passage and the injection nozzle through the passage, and displacement in excess of the predetermined length establishing a direct connection between the inlet passage and the injection nozzle; and an actuator controlling pressure in the control chamber.
The present invention is also achieved by providing a valve for controlling fluid flow between a fluid inlet and a fluid outlet. The valve comprises a valve body including a first valve seat and a second valve seat; and a valve element displaceable with respect to the valve body between a first configuration and a second configuration. The valve element includes a first valve portion sealingly engaging the first valve seat in the first configuration to prevent fluid flow, and being sufficiently separated from the first valve seat in the second configuration to permit fluid flow at an unrestricted rate between the fluid inlet and the fluid outlet; a second valve portion sealingly engaging the second valve seat in the first configuration and separating from the second valve seat at a third configuration of the valve element with respect to the valve seat, the third configuration occurring at an intermediate displacement between the first and second configurations; and a passage extending through the second valve portion and permitting fluid flow at a restricted rate between the fluid inlet and the fluid outlet during displacement between the first and third configurations.
The present invention is further achieved by providing a method of controlling fuel flow from an inlet passage to an injection nozzle. The method comprises providing a valve interposed in the fluid flow between the inlet passage and the injection nozzle; actuating the valve to initially provide a first rate of the fuel flow through the valve; and further actuating the valve to subsequently provide a second rate of the fuel flow through the valve, the second rate being greater than the first rate.
REFERENCES:
patent: 6029632 (2000-02-01), Augustin
patent: 6112721 (2000-09-01), Kouketsu et al.
Ali Hyder
Argenbright Tony M.
Siemens Aktiengesellschaft
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