Measuring and testing – Engine detonation – Combustion signal compared to a fixed reference signal or...
Patent
1994-08-04
1995-11-21
Williams, Hezron E.
Measuring and testing
Engine detonation
Combustion signal compared to a fixed reference signal or...
G01L 2322
Patent
active
054676380
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for recognizing the knocking of an internal-combustion engine and to a device for carrying out the method.
It is known that so-called knocking can occur under specific operating conditions of an internal-combustion engine. By this is meant shock waves of a fuel/air mixture which become noticeable as, inter alia, audio-frequency vibrations of the engine. Since the knocking is accompanied, as a rule, by a high thermal load on the piston-cylinder wall located on the combustion-space side, during which erosions of material can occur, the aim is fundamentally to prevent knocking, since, if it occurs for a relatively long period of time, it can lead to a destruction of the internal-combustion engine.
However, since, on the other hand, the aim is to utilize as far as possible the existing working range of the internal-combustion engine, particularly with regard to engines for racing cars, there is a need to recognize the knocking of the internal-combustion engine as early and as reliably as possible. At the same time, there is the measurement problem of reading out the knock signal reliably and in a fault-free manner from the vibrations of the internal-combustion engine recorded by a sensor, so that the internal-combustion engine can be regulated appropriately as a function of the occurrence of the knocking.
It is generally known that, to recognize knocking, a signal assigned to the knocking process is compared with a reference signal. If the reference signal is exceeded by the knock signal, a knock-recognition signal is transmitted. A disadvantage of this is that the reference signal has to be provided in a highly complicated manner.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of detecting knocking of an internal combustion engine which does not have the above-described disadvantages.
According to the invention, the method of detecting knocking of an internal combustion engine includes the steps of: sensor provided with the internal combustion engine; signal; high-frequency signal including oscillations having amplitudes; greater than a first threshold value (P1) to form an amplitude count; integrated signal; the amplitude count is at least one and when the integrated signal is greater than the second threshold value (P2).
In contrast to this, the advantage of the method according to the invention, having the features mentioned above claim, is that the input signal obtained, supplied by a knock sensor, can be fed directly to a knock control known per se and is balanced there with specific actual values of the internal-combustion engine. For this purpose, the signals from the knock sensor are digitized, subsequently high-pass-filtered and then integrated on, and the signal thus obtained is compared with two predetermined limit values, a knocking process being recognized when both limit values are exceeded.
This soon shows that the knock signal to be evaluated can be differentiated from other subsidiary signals with the highest reliability.
In an advantageous embodiment of the invention, provision is made for taking the pressure trend of the cylinder internal pressure of an internal-combustion engine as a basis for generating the signals of the knock sensor, and for comparing this signal with an absolute value, predetermined as a desired value, of the energy content of the pressure vibrations and the number of pressure amplitudes above a pressure limit value.
In an especially advantageous way, the comparative measurement is carried out within a measurement window dependent on the position of the crankshaft.
According to the invention, the device for detecting knocking in an internal combustion engine comprises a knock sensor, advantageously a pressure transducer, for generating a sensor signal characteristic of knocking in the internal combustion engine; an analog/digital converter connected to the knock sensor to receive the sensor signal and to generate a digitized signal; and processor means for high-pass
REFERENCES:
patent: 4356551 (1982-10-01), Iwase
patent: 4512310 (1985-04-01), Haraguchi
patent: 5321973 (1994-06-01), Sogawa
patent: 5347846 (1994-09-01), Kitano
Oda Christine K.
Robert & Bosch GmbH
Striker Michael J.
Williams Hezron E.
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