Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-04-24
2001-12-18
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S486000, C123S406580, C073S114220, C701S107000
Reexamination Certificate
active
06330877
ABSTRACT:
BACKGROUND TO THE INVENTION, AND STATE OF THE ART
The invention relates to an apparatus and a method for enabling the calibration and/or monitoring of a combustion process in a combustion engine involving detecting noise from the engine related to the combustion process.
The manufacture of a vehicle which is driven by a combustion engine usually involves calibration of the engine's fuel injection system. Such calibration is usually carried out by manual methods which may be complicated and time-consuming, particularly the calibration of a combustion process in a diesel engine which incorporates so-called unit injectors, i.e. a high-pressure pump in combination with an injection nozzle. Such unit injectors are arranged on each of the engine cylinders and each incorporates an individual electrical control. Each of these unit injectors has therefore to be individually calibrated so that it injects fuel into the respective combustion chamber at exactly the time when the engine crankshaft is in an optimum position for the combustion process.
During subsequent operation of the vehicle, usually there is no monitoring of the combustion process to check that combustion takes place correctly and at the right time. Any checks are usually carried out only on certain predetermined servicing occasions or when an observant driver of the vehicle discovers that some fault has occurred in the combustion process, e.g. by the engine noise having changed. The probability of someone substantially immediately discovering a fault in the combustion process is slight and continuing operation without correcting the fault may lead to serious damage which may entail large repair costs or may cause the vehicle to be stationary at an inappropriate time or at an inaccessible location.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an arrangement and a method which make it easy and quick to calibrate a combustion process in a combustion engine so that an injection device injects fuel into the engine combustion chamber at a correct time. Another object is to enable subsequent monitoring of the combustion process so that any defects in the combustion process can be detected almost immediately and remedied in time before they lead to major damage.
These objects are achieved by the arrangement and the method according to the invention. There is at least one sensor at the engine which detects noise of the combustion process. The sensor may be a so-called knock sensor. The sensor detects a parameter which derives from the noise generated during the combustion process so that the time when the noise occurs can be determined in the control unit. The noise to be detected is not the mechanical noise of the injector, as in U.S. Pat. No. 4,102,181, but instead is the noise of the combustion process. The control unit also detects the rotation position of the crankshaft. It is therefore possible to determine the crankshaft position at which fuel is injected into the combustion chamber. The fuel is of course injected somewhat prior to combustion, but the difference in time is negligible. An injection device can therefore be calibrated so that it injects fuel into the combustion chamber when the crankshaft is in a position which is correct in this respect. The detection of the parameter enables monitoring of combustion process so that it is possible to immediately detect a fault occurring with respect to any of the components involved in the combustion process. The value of the parameter may make it possible to determine the type of fault and which component caused the fault.
According to a preferred embodiment of the invention, the parameter may consist of either the frequency or the amplitude of the noise generated during the combustion process. Preferably both of these parameters are registered in the control unit. Because the noise generated during the combustion process usually has a specific amplitude and frequency, this makes it easy for the control unit to recognize that noise and hence register the time at which it occurs. For the control unit to receive a signal that is as free as possible from interference, the arrangement may incorporate at least one filter which is arranged between the sensor and the control unit and which is designed to filter out signal values which are not due to the combustion process. Such a filter may incorporate at least a first filter device, e.g. in the form of an inverted bandpass filter, which is designed to allow only signal values at a specific frequency to pass through. The filter device may be designed to let through only signal values for noise at a known frequency which occurs during the combustion process. This means that such a filter device passes a signal to the control unit when the combustion process is taking place in the combustion chamber, but transmits no signal when no combustion is taking place in the combustion chamber. The control unit can thus register the time when a signal occurs after a pause and can therefore determine the time when the fuel is injected into the combustion chamber. This makes it possible to check that an injection device is injecting fuel into the combustion chamber at a correct time. The filter may also incorporate a second filter device, e.g. in the form of a bandpass filter, which is designed to allow signal values within at least one frequency range to pass through. Such a second filter may be connected in parallel with the first filter and let through signal values which derive from noise within a frequency range which is relevant to the combustion process. Interfering signals due to noise at a frequency outside that range are thus filtered out.
According to another preferred embodiment of the invention, the control unit may be designed to store signal values representing the parameter from a combustion process which incorporates a calibrated injection device. Such signal values relating to the noise which is generated during the combustion process may thus include information on the amplitude and frequency of the noise and the time at which the signal value occurs. The control unit may further be designed to monitor that the relevant signal values received representing the parameter correspond to the stored signal values. The control unit may be in communication with an indicating device which is designed to be activated if the relevant signal values received do not correspond to the stored signal values. Such differences between signal values may derive from the amplitude or frequency of the noise or the time at which the noise occurs. The indicating device may incorporate a lamp on an instrument panel of a vehicle, which lights up when a difference in signal value occurs, in order to make the driver immediately aware that a fault has occurred in the combustion process. Based on the nature of the faulty signal value, such an indicating device may possibly also indicate possible causes of the fault.
It is particularly advantageous to apply the present invention to a combustion engine which has a multiplicity of combustion chambers, each having an injection device. It may for example be a diesel engine with a unit injector arranged on each cylinder. In such cases, each injector has to be calibrated individually, which is complicated, but with the present invention that calibration of the fuel injection is considerably simplified.
The present invention also concerns a method for calibrating and/or monitoring the combustion process in a combustion chamber of an engine wherein the chamber is supplied with fuel by a fuel injection device. At least one parameter derived from the noise generated during combustion is detected. It is combined with information about the rotation position of the crankshaft for calibrating injection of fuel into the combustion chamber. Determining the position of the crankshaft at the time of combustion makes it possible to calibrate, for example, an injection pump so that it injects fuel exactly at the time when the crankshaft is in an optimum position for the combustion process.
A
Ostrolenk Faber Gerb & Soffen, LLP
Scania CV Aktiebolag
Vo Hieu T.
Yuen Henry C.
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