Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Reexamination Certificate
1999-09-29
2001-03-06
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
C123S435000, C701S111000, C701S115000, C073S035110
Reexamination Certificate
active
06196184
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a device for detecting a preinjection in an internal combustion engine operating with a direct injection.
Internal combustion engines using a direct fuel injection have a considerable potential for reducing the fuel consumption combined with a relatively low pollutant emission. Unlike with a manifold fuel injection, with a direct fuel injection, fuel is injected directly into the combustion chamber at a high pressure.
Injection systems with a central pressure accumulator (common-rail) are known for this purpose. In such common-rail systems, a high-pressure pump is used to build up in the common rail a fuel pressure, which is controlled by an electronic controller of the internal combustion engine via a pressure sensor and a pressure controller and which is available substantially independently of the engine speed and injection quantity. The fuel is injected into the combustion chamber via an injector having a solenoid valve or a piezoelectric valve. The injector receives its signals from the controller. Owing to the functional separation of pressure production and injection, the injection pressure can be selected substantially independently of a current operating point of the internal combustion engine.
The combustion noise of an internal combustion engine operating with direct injection, in particular the noise of a diesel internal combustion engine, can be substantially reduced when the calculated fuel quantity is not injected at once, but is distributed over two injection processes per cylinder stroke. In this case, a quantity of fuel, which is small compared to the total quantity to be injected and is also known as a pilot quantity, is injected during a preinjection process, and the main quantity is injected after a period which depends, as a rule, on the operating point of the interna combustion engine and is expressed in degrees of crank angle (see for example Published German Patent Application DE 39 35 937 A1). A reduction in the pressure gradient in the combustion chamber is thereby achieved, as a result of which the noise behavior of the combustion and thus of the internal combustion engine is substantially improved.
Without a preinjection, not only the noise behavior of the internal combustion engine is worse, but also the exhaust emissions increase.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a simple and cost-effective method and device for detecting a preinjection process in an internal combustion engine.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for detecting a preinjection in an internal combustion engine operating with a direct injection. The method comprises the steps of:
metering fuel, with at least one injector having a nozzle needle and a needle seat assigned to the nozzle needle, the fuel being split up into a preinjection and a main injection;
detecting within a measuring window, with a sensor for structure-borne noise, a vibration signal generated by the nozzle needle when striking the needle seat; and
deriving a criterion for detecting an occurrence of the preinjection based on an intensity of the detected vibration signal.
In accordance with another mode of the invention, the vibration signal is rectified; an envelope curve is formed for the rectified vibration signal; the area under the envelope curve is determined; the area under the envelope curve is compared with a given threshold value; and, when the given threshold is exceeded in the comparing step, a conclusion is made that the preinjection has occurred.
In accordance with yet another mode of the invention, an entry into a fault memory is made when the given threshold value is not exceeded in the comparing step.
In accordance with a further mode of the invention, a fault information is optically displayed or acoustically communicated to an operator of a vehicle having an internal combustion engine, when the given threshold value is not exceeded in the comparing step.
With the objects of the invention in view there is also provided, a device for detecting a preinjection in an internal combustion engine operating with a direct injection, comprising:
at least one injector having a nozzle needle and a needle seat assigned to the nozzle needle for metering fuel split up into a preinjection and a main injection;
a sensor for structure-borne noise disposed on an internal combustion engine for picking up a vibration signal generated by the nozzle needle on striking the needle seat;
an evaluation circuit for generating an envelope curve of the vibration signal;
a calculating device for calculating an area below the envelope curve;
a comparator for comparing the area with a given threshold value; and
a storage device for storing and indicating a fault when the given threshold value is undershot.
In accordance with another feature of the invention, the evaluation circuit, the calculating device, and the comparator are incorporated in a control device which controls an operation of an internal combustion engine.
In accordance with yet another feature of the invention, the evaluation circuit and the calculating device are incorporated in the sensor for structure-borne noise.
In accordance with a further feature of the invention, the evaluation circuit includes a bandpass filter for filtering the vibration signal, a rectifier for rectifying the filtered vibration signal, and a low-pass filter for generating the envelope curve.
In accordance with yet a further feature of the invention, the calculating device includes an integrator for calculating the area under the envelope curve.
In accordance with an added feature of the invention, the sensor for structure-borne noise is a knock sensor operating in accordance with a piezoelectric principle.
By picking up and evaluating the vibration signal, which occurs when the nozzle needle strikes the needle seat, with a sensor for structure-borne noise in the form of a commercially available knock sensor disposed on the outer wall of a cylinder, it is possible to make a conclusion on the presence or absence of the preinjection in a combustion cycle. In the case where there is no preinjection, the fault is stored, the fault is displayed to the driver, and measures can be initiated to reduce the emissions, which occur to an increased degree when the fault occurs.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for detecting a preinjection in an internal combustion engine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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Böhnig Ralf
Przymusinski Achim
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Wolfe Willis R.
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