JPS60174918A - Knocking detection apparatus of internal combustion engine - Google Patents

Abstract

PURPOSE:To attain to enhance fuel consumption and power capacity by calculating an optimum ignition period with good accuracy, by enhancing knocking detection accuracy. CONSTITUTION:The output of a knocking sensor 10 is directly inputted to a digital filter 32 where multiplexing processing is applied to the output of said knocking sensor 10 and the signal obtained by delaying said output by a predetermined time T to perform the detection of a higher harmonic component. Then, the fundamental wave of the resonance frequency of knocking extracted by a first stage digital filter 32 and the higher harmonic component are further passed through second and third stage digital filters 34, 36 to be amplified and extracted at an extremely high S/N ratio. The output of a final stage digital filter 36 is inputted to a knocking discrimination circuit 38 and the presence or absence of knocking is judged. As mentioned above, by employing the digital filters 32, 34, 36, even a small knocking signal can be extracted in a state separated from noise.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a knocking detection device for an internal combustion engine, and is particularly suitable for use in ignition timing control of a gasoline engine. The present invention relates to an improvement in a knocking detection device for an internal combustion engine that detects the presence or absence of.

[Prior art]

Generally installed in internal combustion engines, especially in vehicles such as automobiles,
In a spark-ignition internal combustion engine such as a gasoline engine, controlling the ignition timing to an appropriate value depending on the operating state of the engine, such as MBT, is an effective way to improve the output performance and fuel efficiency of the engine. This is extremely important. Various types of ignition timing control devices have been put into practical use for such internal combustion engines, but in recent years,
A knock sensor that detects the vibration of the cylinder block wall and converts it into an electrical signal is installed in the cylinder block of the engine, and the basic ignition timing determined according to the operating state of the engine is determined from the output of the knock sensor. Ignition timing control devices have been put into practical use that perform ignition timing control according to the knocking state of the engine by making corrections depending on the determined presence or absence of knocking. When determining the presence or absence of knocking in such an ignition timing control device, conventionally, as shown in FIG. A band pass filter (hereinafter referred to as BPF) 12 including an amplifier, a level shifter 14 that levels-shifts the fundamental wave component of the output of the BPF 12 to obtain a signal to be determined Vi, and half-wave rectifies and integrates the output of the BPF 12, Amplify and compare level Vr
a rectifier 16, an integrator 18, and an amplifier 20, and a comparator 22 that generates a retard signal when the determined signal Vi output from the level shifter 14 becomes larger than the comparison level Vr and it is determined that there is knocking. For example, there is a system proposed in Japanese Patent Laid-Open No. 57-178114, in which a retard signal output from the comparator 22 is input to an ignition timing control device @24 to control a predetermined amount of retard. . According to the knocking detection device using PFI 2, an example of the cylinder pressure spectrum when knocking occurs is shown in Fig. 2 by solid line A (with knocking) and broken line B (with no knocking). The knock sensor 1
It is possible to cut off the low frequency component of the electric signal from 0 caused by drift, etc., and the high frequency component generated by electromagnetic noise, etc., and perform highly accurate knocking detection for relatively large knocking. It is something that can be done. However, for small knocks such as trace knocks, there is a possibility of erroneous detection due to ignition noise, etc. On the other hand, instead of using the analog configuration as shown in FIG. 1, as shown in FIG.
In the microcomputer 28, for example, the peak hold value ■p of the output of the knock sensor 10 is determined for each ignition, and then the determination level Vr is obtained by setting it to a predetermined value. Peak hold of the judgment level Vr and knock sensor 10 output (
ii Compare Vu and the peak hold l! Since Vp has become equal to or higher than the above-mentioned determination level V,r, knocking can be detected, for example, as disclosed in Japanese Patent Application Laid-open No. 58-28597 and No. 58-28597.
8-28645. However, even in such a knocking detection device with a digital configuration, only the resonant frequency component of knocking is extracted from the output of the knock sensor 10 using the analog BPFI 2, so the analog configuration shown in FIG. It had the same problems as the knocking detection device.

[Purpose of the invention] The present invention has been made to solve the above-mentioned conventional problems, and can improve the accuracy of knocking detection, and therefore performs high-level ignition timing control to improve fuel efficiency and power performance. An object of the present invention is to provide a knocking detection device for an internal combustion engine that is capable of detecting knocking of an internal combustion engine. [Structure of the invention]

The present invention provides a knocking detection device for an internal combustion engine that detects the presence or absence of knocking when a frequency component related to knocking in the knock sensor output becomes higher than a determination level. The above object is achieved by comprising a digital filter that extracts the fundamental wave and harmonic components of the resonant frequency, and a knock identification circuit that identifies the presence or absence of knocking when the output of the digital filter exceeds a determination level. This is what I did. Further, in an embodiment of the present invention, the digital filter includes a first extraction circuit that extracts odd-order harmonic components including the fundamental wave, a second extraction circuit that extracts even-order harmonic components, and a second extraction circuit that extracts even-order harmonic components. It consists of an addition element that adds the output of the first extraction circuit and the output of the second extraction circuit, so that the fundamental wave and harmonic components of the resonant frequency of knocking are reliably extracted. Furthermore, in another embodiment of the present invention, the digital filters are multiplexed to further improve the accuracy of knocking detection. Structure of the Invention In the present invention, not only the fundamental wave component of the resonant frequency of knocking but also the high m-wave component are extracted from the knock sensor output, so that the accuracy of knocking detection can be improved. In addition, when extracting the fundamental wave and harmonic components of the resonant frequency of the knocking, a digital filter is used, so by using multiplexing technology etc., the required accuracy is much higher than that of an analog filter. In addition, improvements in the manufacturing technology of large-scale integrated circuits (hereinafter referred to as J:1. LSI) provide significant cost benefits.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a knocking detection device for an automobile engine according to the present invention will be described in detail with reference to the drawings. As shown in FIG. 4, this embodiment uses a knock sensor 10 similar to the conventional example, and extracts the fundamental wave and harmonic components of the knocking resonance frequency from the output of the knock sensor 10.
Since the outputs of the triple digital filters 32, 34, and 36 and the final stage digital filter 36 are greater than the determination level, the presence or absence of knocking is identified, and when knocking occurs, the retard signal is used to control the ignition timing. and a knock identification circuit 38 that inputs input to the II device 24. There are various types of the knock sensor 10, and for example, a resonance type that is sensitive to the frequency band of the poem when the engine block knocks can be used. Each of the digital filters 32, 34, 36 includes first and second digital delay elements 32A, 32B for delaying the output of the knock sensor 10 by a predetermined time τ, as also shown in detail in FIG. and the knock sensor 1
By subtracting the output of the first digital delay element 32A from the output of 0, odd-numbered harmonic components including the fundamental wave, that is, 1st, 3rd, 5th, etc., are extracted. By adding the subtraction element 32C and the output of the second digital delay element 32B to the output of the knock sensor 10, the harmonic components of even orders, that is, second order, fourth order, etc., are extracted. Addition element 32D and subtraction element 32
The adder element 32E is configured to add the output of the adder C and the output of the adder element 32D. The action will be explained below. The output of the knock sensor 10 is directly input to the digital filter 32 without going through a PF or the like as used in the conventional example, and here, the output of the knock sensor 10 and the output of the knock sensor 10 are inputted directly to the digital filter 32. Harmonic components are detected by multiplexing signals delayed by a predetermined time. The fundamental wave and harmonic components of the knocking resonance frequency extracted by the first stage digital filter 32 are further passed through the second and third stage digital filters 34 and 36 to achieve a very high S/ Amplified and extracted at N ratio. The output of the final stage digital filter 36 is input to a knock identification circuit 38 similar to the conventional one, and the presence or absence of knocking is determined in the same manner as the conventional one. In this way, by employing the digital filters 32, 34, 36, even a small knock signal as shown in FIG. 2 above can be extracted separately from noise. In this embodiment, three digital filters are provided.
Since the filters are overlapped, sharp filter performance can be obtained, and knocking can be determined with a higher S/N ratio. Note that the number of digital filters is not limited to this.
It is also possible to simplify the configuration by using two, four or more, or one. In the above embodiment, the present invention is applied to ignition timing control of an automobile engine, but the scope of application of the present invention is not limited to this, and can also be applied to ignition timing control of general internal combustion engines and other controls. It is clear that the same applies.

【Effect of the invention】

As explained above, according to the present invention, it is possible to reliably detect the output component of knocking, and the 'SiN ratio for knocking detection can be improved. Therefore, it is possible to accurately aim at the optimal ignition timing, and fuel efficiency and power performance can be improved. Furthermore, since a digital filter is used, there is a large cost advantage due to improvements in LSI manufacturing technology. Furthermore, in the digital filter, frequency matching is possible by simply changing the delay time of the delay element, so it has the advantage of being applicable to other types of knocking frequency determination circuits.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an example of a conventional knocking detection V device, Fig. 2 is a diagram showing an example of a cylinder pressure spectrum when knocking occurs, and Fig. 3 is a diagram showing an example of a conventional knocking detection V device. Block Diagram Showing the Structure of Another Example of the Device FIG. 4 is a block diagram showing the structure of an embodiment of the knocking detection device for an automobile engine according to the present invention. 10... Knock sensor, 24... Ignition timing control device, 32.34.3G... Digital filter J32A, 3
2B... Digital delay element, 32C... Subtraction element, 32D, 32E... Addition element, 38... Knock identification circuit. Agent Takaya Ron (and 1 other person) Fig. 1 Fig. 2 rll M=IT income - Fig. 3 Fig. 4

Claims (3)

[Claims] (1) In a knocking detection device for an internal combustion engine that detects the presence or absence of knocking because the frequency component related to knocking in the knock sensor output has become larger than the determination level, the resonance of knocking is detected from the knock sensor output. An internal combustion engine characterized by comprising: a digital filter that extracts the fundamental wave and harmonic components of a frequency; and a knock identification circuit that identifies the presence or absence of knocking based on the output of the digital filter being greater than a determination level. knocking detection device. (2) The digital filter includes a first extraction circuit that extracts odd-order harmonic components including the fundamental wave, a second extraction circuit that extracts even-order harmonic components, and an output of the first extraction circuit. 2. The knocking detection device for an internal combustion engine according to claim 1, comprising an addition element for adding up the output of the second extraction circuit. (3) The knocking detection device for an internal combustion engine according to claim 1 or 2, wherein the digital filter is multiplexed.