Injection unit and injection method for an internal combustion engine
First Claim
1. An injection unit for an internal combustion engine, comprisinga pressure reservoir for storing fuel pumped into the pressure reservoir from a fuel tank by means of a high-pressure pump, andan injector arrangement, connected to the pressure reservoir by means of a pressure line arrangement, for injecting the fuel into the internal combustion engine,whereinthe injector arrangement comprises at least one servo injection valve in which both a nozzle chamber and a control chamber are supplied with fuel from the pressure reservoir via a pressure line and in which a nozzle body for opening and closing an injection passage leading from the nozzle chamber to a combustion chamber is displaceably guided, and the nozzle body is exposed at its end facing the injection passage to the pressure of the fuel in the nozzle chamber and at its opposing end to the pressure of the fuel in the control chamber,the servo injection valve is provided with a control valve for the release of fuel from the control chamber into a fuel return line leading to the fuel tank, which control valve may be operated by means of a piezoelectric actuator to cause a displacement of the nozzle body in the direction of an opening of the injection passage, for initiating an injection process by pressure reduction in the control chamber,the fuel return line is provided with a controllable valve which in an actuated state blocks the fuel flow in the fuel return line, and wherein the valve is actuated depending on predefined operating parameters of the internal combustion engine and/or the injection unit and is returned to an idle state only after expiration of a predeterminable time interval.
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Accused Products
Abstract
An injection unit has an injector arrangement connected to a pressure reservoir by a pressure line arrangement The injector arrangement has at least one servo injection valve and a control valve for the release of fuel from a control chamber into a fuel return line leading to the fuel tank The Valve may be operated by a piezoelectric actuator to cause a displacement of a nozzle body in the direction of an injection passage opening for initiating an injection process by pressure reduction in the control chamber. The fuel return line has a controllable valve, which restricts the fuel flow in the fuel return line in the actuated state. It is, thus, possible to reduce the effects of a change of length of the piezoelectric actuator, which exceeds the so-called tolerance gap in the servo injection valve, which are detrimental to the operation of the injection unit.
32 Citations
18 Claims
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1. An injection unit for an internal combustion engine, comprising
a pressure reservoir for storing fuel pumped into the pressure reservoir from a fuel tank by means of a high-pressure pump, and an injector arrangement, connected to the pressure reservoir by means of a pressure line arrangement, for injecting the fuel into the internal combustion engine, wherein the injector arrangement comprises at least one servo injection valve in which both a nozzle chamber and a control chamber are supplied with fuel from the pressure reservoir via a pressure line and in which a nozzle body for opening and closing an injection passage leading from the nozzle chamber to a combustion chamber is displaceably guided, and the nozzle body is exposed at its end facing the injection passage to the pressure of the fuel in the nozzle chamber and at its opposing end to the pressure of the fuel in the control chamber, the servo injection valve is provided with a control valve for the release of fuel from the control chamber into a fuel return line leading to the fuel tank, which control valve may be operated by means of a piezoelectric actuator to cause a displacement of the nozzle body in the direction of an opening of the injection passage, for initiating an injection process by pressure reduction in the control chamber, the fuel return line is provided with a controllable valve which in an actuated state blocks the fuel flow in the fuel return line, and wherein the valve is actuated depending on predefined operating parameters of the internal combustion engine and/or the injection unit and is returned to an idle state only after expiration of a predeterminable time interval.
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7. A method for operating an injection unit for an internal combustion engine, wherein the injection unit comprises:
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a pressure reservoir for storing fuel pumped into the pressure reservoir from a fuel tank by means of a high-pressure pump, and an injector arrangement, connected to the pressure reservoir via a pressure line arrangement, for injecting the fuel into the internal combustion engine, wherein the injector arrangement comprises at least one servo injection valve in which both a nozzle chamber and a control chamber are supplied with fuel from the pressure reservoir via a pressure line and in which a nozzle body for opening and closing an injection passage leading from the nozzle chamber to a combustion chamber is displaceably guided, and the nozzle body is exposed at its end facing the injection passage to the pressure of the fuel in the nozzle chamber and at its opposing end to the pressure of the fuel in the control chamber, wherein the servo injection valve is provided with a control valve for the release of fuel from the control chamber into a fuel return line leading to the fuel tank, the method comprising the steps of; actuating the control valve by means of a piezoelectric actuator, to cause a displacement of the nozzle body in the direction of an opening of the injection passage, for initiating an injection process by pressure reduction in the control chamber, blocking of the fuel flow in the fuel return line by a controllable valve, said blocking being provided depending on predefined operating parameters of the internal combustion engine and/or of the injection unit wherein the blocking is not being lifted until after expiration of a predeterminable time interval. - View Dependent Claims (8, 9)
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10. An injection unit for an internal combustion engine, comprising
a pressure reservoir for storing fuel pumped into the pressure reservoir from a fuel tank by means of a high-pressure pump, and an injector arrangement comprising at least one servo injection valve in which both a nozzle chamber and a control chamber are supplied with fuel from the pressure reservoir via a pressure line and in which a nozzle body for opening and closing an injection passage leading from the nozzle chamber to a combustion chamber is displaceably guided, and the nozzle body is exposed at its end facing the injection passage to the pressure of the fuel in the nozzle chamber and at its opposing end to the pressure of the fuel in the control chamber, the servo injection valve comprising a control valve for the release of fuel from the control chamber into a fuel return line leading to the fuel tank, and a controllable valve which in an actuated state blocks the fuel flow in the fuel return line, and which is actuated depending on predefined operating parameters of the internal combustion engine and/or the injection unit and which is returned to an idle state only after expiration of a predeterminable time interval.
Specification