JPS6082931A - Knocking detecting device of engine - Google Patents

Abstract

PURPOSE:To detect with high accuracy knocking without being influenced by a mechanical noise, etc. by using two filters, and eliminating a signal component caused by the mechanical noise, etc., from an output signal of a knocking sensor. CONSTITUTION:A titled device is provided with the first filter 23 for making only a signal of a knocking frequency band pass through among output signals of a knocking sensor 20 set on an engine body, and the second filter 24 for making a signal of other frequency band than the knocking frequency band pass through among the output signals of the knocking sensor 20. Also, it is provided with a deviation quantity operating means consisting of an adding circuit 26 for calculating a deviation of output signals of the first filter 23 and the second filter 24, etc., and a knocking discriminating means for comparing the deviation and a set value and discriminating whether a knocking exists or not. In this way, a signal component caused by a mechanical noise, etc. is eliminated from the output signal of the knocking sensor, therefore, a knocking can be detected with a high accuracy without being influenced by a mechanical noise, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine knocking detection device.

(Prior Art) Conventionally, in engines, especially automobile engines, Japanese Patent Application Publication No. -, 36r2 As shown in Otsu No. 2, there is a known engine which detects knocking and controls the ignition timing based on the detected value. In other words, by retarding the engine's ignition timing when knocking occurs and suppressing knocking, the optimal ignition timing as required by the engine is obtained within a range where knocking does not occur, and It is designed to improve fuel efficiency.

However, in such devices, the engine vibration signal output from the knocking sensor is passed through a filter, only the vibration signal of a specific frequency caused by knocking is extracted, and this vibration signal is compared with a certain level (slice level). However, if the vibration signal exceeds a certain level, it was determined to be knocking, but since the vibration signal detected in this way also has a signal component of the above-mentioned specific frequency, the vibration signal is considered to be mechanical noise. There is a problem in that the vibration signal exceeds a certain level and is determined to be knocking, resulting in a malfunction, even though knocking is not actually occurring.

(Object of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to provide an engine knocking detection device that can accurately detect knocking without being affected by mechanical noise, etc. It is something.

(Structure of the Invention) In order to achieve the above-mentioned object, the present invention includes a knocking sensor disposed in an engine body, a first filter that passes only a signal in the knocking frequency band among the output signals of the knocking sensor, and a knocking sensor provided in the engine body. Pass signals in frequency bands other than the knocking frequency band among the sensor output signals @! It is characterized by comprising a filter, a deviation amount calculation means for calculating the deviation of the output signals of the first filter and the second filter, and a knocking determination means for comparing the deviation with a set value and determining the presence or absence of knocking. That is.

That is, the present invention uses two filters, that is, the first and second filters, since the knocking frequency band is narrow, while the frequency band of mechanical noise is wide. Only signals in the knocking frequency band are passed through one filter, and signals in frequency bands other than the knocking frequency band, that is, noise signals such as mechanical noise, are passed through the second filter. , □ is used to cancel out the noise output and detect only the signal caused by knocking, thereby determining the presence or absence of knocking.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 showing a turbocharged engine, reference numeral 1 denotes an engine body, in which a cylinder head 4 is attached to a cylinder block 2 via a gasket 6, and a combustion chamber S is formed.

5 is an intake passage, from the upstream side, an air cleaner 6, an air flow meter 7% exhaust turbo supercharger 8 compressor 9,
Throttle valve 10. A surge tank 11 is provided in order, and is connected to the combustion chamber Sl of the engine via an intake port 13 which is opened and closed by an intake valve 12.

Reference numeral 14 denotes an exhaust passage, in which a turbine 15 of an exhaust turbo supercharger 8 and a catalyst device 16 for purifying exhaust gas are provided in this order from the upstream side, and an exhaust port 18 at the upstream end is opened and closed by an exhaust valve 17. The downstream end is open to the atmosphere, while the downstream end is open to the atmosphere.

Compressor 9 and turbine 1 of the exhaust turbo supercharger 8
A turbine 15, which is integrally connected to the compressor 5 by a shaft 19 and driven to rotate by exhaust gas, rotates the compressor 9, and supercharging is performed under predetermined conditions.

A knocking sensor 20 is disposed in the cylinder head 4, and the output from the knocking sensor 2o is input to the control unit 21. The control unit 21 controls the distributor 22 according to the output from the knocking safety sensor 20, and adjusts the ignition timing.

As shown in detail, the control unit 21 includes a first filter 23 that passes only signals in the knocking frequency band among the output signals of the knocking sensor 20, and a first filter 23 that passes only signals in the knocking frequency band among the output signals of the knocking sensor 20; A second filter 2 that passes signals in frequency bands other than the
4, an inversion circuit 25 that inverts the output signal of the second filter 24, and an addition circuit 2 as a deviation amount calculation means that adds the output signal of the first filter 26 and the output signal of the inversion circuit 25.
6, and a smoothing circuit 2 that smoothes the output signal of the adder circuit 26.
7, and an amplification circuit 28 that amplifies the output signal of the smoothing circuit 27.
and a comparison circuit 29 as a knocking determination means that compares the output signal of the adder circuit 26 and the output signal of the amplification circuit 28 to determine the presence or absence of knocking, and controls the ignition timing according to the output signal of the comparison circuit 29. It has an ignition timing control circuit 60.

With the above configuration, the output signal (vibration signal) of the knocking sensor 20 is transmitted through the first and second filters 23.2.
4, the output signal MA of the first filter 23 becomes a signal only in the knocking frequency band (for example, ?, J KHz), while the output signal 'ijB of the second filter 24 becomes a signal in a frequency band other than the knocking frequency band, for example. The signal is in a frequency band sufficiently far from the knocking frequency band.

Thus, the output signal B of the second filter 24 is inverted by the inverting circuit 25, and added to the output signal Al of the first filter 23 by the adding circuit 261.

As a result, the output signal B (vibration signal due to mechanical noise, etc.) of the second filter 24 is subtracted from the output signal A (vibration signal due to knocking, mechanical noise, etc.) of the first filter 23. The output signal C of the adder circuit 26 is %
This is the deviation between the output signals of the first filter 26 and the second filter 24, and is a vibration signal due to knocking that does not include vibration signals caused by mechanical noise or the like.

The output signal C of the adder circuit 26 is smoothed by a smoothing circuit 27 and amplified by an amplification circuit 28 to become an output signal of a constant level. This output signal C is then compared with the output signal C in a comparator circuit 29, and it is determined whether or not there is a knocking state. That is, when the output signal C exceeds the level of the output signal C, it is determined that the knocking state is present.

Then, based on the output signal E from the comparison circuit 29, the ignition timing of the engine is controlled by the ignition timing control circuit 60. In other words, if it is determined that knocking is occurring, the ignition timing is retarded, while if it is determined that knocking is not occurring, the ignition timing is advanced, so that the distributor adjusts the ignition timing to the optimum ignition timing within the range where knocking does not occur. 22 is controlled.

Although the embodiments have been described above, the present invention includes a case where control is performed by a digital computer. Further, the knocking detection according to the present invention is not limited to ignition timing control, but can be appropriately used for various purposes such as air-fuel ratio control and supercharging pressure control.

(Effects of the Invention) As described above, the present invention uses two filters to remove signal components due to mechanical noise etc. from the output signal of the knocking sensor. can be detected with good accuracy.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an engine knocking detection device according to an embodiment of the present invention, Fig. 2 is a block diagram showing an example of a control unit, and Fig. 3 (al (bl (C) (d)
1 is a diagram showing waveforms of output signals A, B, C%D, and E in FIG. 2;

Claims (1)

[Claims] (1) A knocking sensor installed in the engine body,
A first filter that passes only signals in a knocking frequency band among the output signals of the knocking sensor, a second filter that passes signals in a frequency band other than the knocking frequency band among the output signals of the knocking sensor, and the first filter. Engine knocking detection characterized by comprising a deviation amount calculation means for calculating the deviation of the output signal from the second filter, and a knocking determination means for comparing the deviation with a set value and determining the presence or absence of knocking. Device.