JPH0526506Y2 - - Google Patents

Description

[Detailed description of the invention] Purpose of the invention [Field of industrial application] The present invention relates to a knocking detection device, and more specifically, a knocking detection device configured to use a non-resonant knock sensor as a detection means and amplify a knocking signal by a filter amplifier. The present invention relates to a knocking detection device that removes the influence of excitation caused to a filter amplifier by noise in a device.

[Prior Art] Conventionally, engine control systems have been proposed that control the ignition timing, etc., to near the knocking limit in order to bring out the maximum performance of the internal combustion engine. Accurate detection is a problem. For this reason, various knocking detection devices have been proposed (for example, ``knocking detection device for internal combustion engine'' disclosed in Japanese Utility Model Application Laid-Open No. 56-149927). Knocking detection means used in such a knocking detection device include a resonance type knock sensor and a non-resonance type knock sensor as types that detect vibrations of an internal combustion engine.

For resonance type knock sensors, the natural frequency of the sensor itself is within the knock characteristic frequency of the internal combustion engine (e.g. 6~
8KHz) and has excellent knocking detection ability, but it also has the disadvantage that its natural frequency must be tuned to match the knocking characteristic frequency of the internal combustion engine to which it is applied.

On the other hand, non-resonant knock sensors have selectivity (sharpness of resonance curve) at the knock characteristic frequency.
If a high Q filter amplifier is used in the latter stage to amplify the output signal of a non-resonant knock sensor, output characteristics comparable to those of a resonant knock sensor can be obtained, and only one type of knock sensor is required regardless of the type of internal combustion engine. It has a number of advantages, such as being easily adapted to each individual internal combustion engine, and furthermore, if the selectivity Q is chosen to be a relatively low value, it can easily respond to fluctuations in the knock characteristic frequency. .

[Problems to be Solved by the Invention] However, the knocking detection device using such a non-resonant knock sensor has the following problems. That is, since a filter amplifier with a high selectivity Q is used, the filter amplifier may be excited by disturbances such as noise and output an erroneous signal. A more detailed explanation will be given below.

Normally, a knocking detection device using a non-resonant knock sensor uses the knock characteristic frequency of the internal combustion engine in processing the signal from the non-resonant knock sensor.
An amplifying section (hereinafter referred to as a filter amplifier together with the band pass filter) having a band pass filter with a frequency o substantially matching e is provided. This filter amplifier has a selectivity Q set to, for example, about 20 dB in order to detect the component of the knock characteristic frequency e from the output signal of the non-resonant knock sensor when knocking occurs. Here, the selectivity Q is defined as the width Δ of the frequency that is 3 dB lower than the amplification degree at the center frequency o, and is defined as Q=20×log(fo/Δf) (1).

In a filter amplifier having such a high selectivity Q, a phenomenon is observed in which the filter amplifier itself causes excitation at its own center frequency o due to disturbances such as electrical noise. Figure 4 shows this situation, where a noise voltage signal Vn is applied to the ground line of a filter amplifier with a selectivity Q of 20 dB.
The excitation waveform of the output voltage Vout when this is coupled with a tone burst waveform and weighted is shown.

This problem, that is, sensitivity to noise, is the same even when a knocking detection device is installed in a vehicle. The filter amplifier may be excited by high-frequency noise added to lines, signal lines, etc.

On the other hand, if the selectivity Q of the filter amplifier is lowered or the knocking detection level is lowered to deal with this problem, the performance of the knocking detection device using a non-resonant knock sensor will be lowered.
A problem arises in that it becomes difficult to accurately detect notching, and the controllability of notching control may be sacrificed.

Therefore, it is an object of the present invention to solve the above-mentioned problems and provide a knocking detection device which is not affected by excitation in a configuration where the output of a non-resonant knock sensor is amplified by a highly selective filter amplifier.

Structure of the invention [Means for solving the problem] The means taken to solve the problem are: a non-resonant knock sensor that is attached to an internal combustion engine and detects vibrations of the internal combustion engine; a knocking amplification filter amplifier that inputs an output signal from a knock sensor and selects and amplifies a signal near the frequency of knocking occurring in the internal combustion engine from among the output signals; and a knocking amplification filter amplifier, a power supply line, and ground. For noise detection, which shares a line and is configured similarly to the knocking amplification filter amplifier, and generates the same excitation as that generated in the knocking amplification filter amplifier due to noise input from the power supply line and the ground line. The gist is a configuration of a knocking detection device including: a filter amplifier; and a subtracter that subtracts the output of the noise detection filter amplifier from the output of the knocking amplification filter amplifier and outputs the result as a knocking detection signal.

Here, as the filter amplifier for knocking amplification, an amplifier constructed of an operational amplifier or the like which also functions as a bandpass filter having high selectivity with the center frequency approximately at the knocking characteristic frequency can be used. In addition, the filter amplifier for noise detection is
It is easiest to use the same configuration as the above-mentioned filter amplifier for knocking amplification, but it does not necessarily have to be the same, and it is possible to use a configuration in which the excitation of the filter amplifier for knocking amplification due to noise is shimmy-rate with respect to the same noise. It doesn't matter what it is. Furthermore, as the subtracter, a subtracter circuit built into a discrete unit can be used.In addition, the output of the filter amplifier for noise detection can be inverted and inputted, and the output can be added to the output of the filter amplifier for knocking amplification. , or it can be configured to be subtracted by a differential amplifier.

[Function] In the knocking detection device configured as described above, when the knocking amplification filter amplifier causes excitation due to electrical disturbance such as noise, the noise detection filter amplifier also generates almost the same excitation.
Therefore, even if excitation occurs due to noise etc. as a result of the high selectivity of the filter amplifier, the excitation will be subtracted by the subtracter, so the effect of excitation will not be on the knocking signal that is output. Almost never appears.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing the configuration of a knocking detection device as an embodiment of the present invention, and FIG. 2 is a circuit diagram showing its detailed circuit. In the figure, 1 is a non-resonant knock sensor as a means for detecting knocking, 3 is a battery as a power source, 4 is a voltage follower for buffering the output of the non-resonant knock sensor 1, 5 is a filter amplifier for knocking amplification, and 7 9 represents a filter amplifier for noise detection, 9 represents an inverting amplifier that inverts the output of the filter amplifier for noise detection, and 11 represents an adder circuit that functions as a subtracter as a whole by using the inverting amplifier 9.

Next, each of the above circuits will be explained. Voltage follower 4 is an operational amplifier as shown in Figure 2.
It is configured based on OP1. Since the voltage follower circuit can make the input impedance extremely high, it was adopted for the purpose of buffering the high impedance output of the non-resonant knock sensor 1. The input impedance of this circuit is determined mostly by the value of resistor r2 (for example, around 100KΩ). Furthermore, the resistors r1 and r3 and the capacitors C1 and C2 are configured to have characteristics as a broadband bandpass filter so that the signal of the non-resonant knock sensor 1 does not exceed its dynamic range at the input terminal of the operational amplifier OP1. ing. The wide band referred to here is a band of several kHz centered on 6 to 8 kHz, which is closely related to knocking, among the vibrations of the internal combustion engine detected by the non-resonant knock sensor 1. D1 and D2 indicate protection diodes. In addition, a non-resonant knock sensor 1
The connection from the voltage follower 4 to the voltage follower 4 is made through a shielded wire 13 whose shielded line is grounded at one point, and consideration is given to preventing noise from being superimposed.

The knocking amplification filter amplifier 5 is configured as an amplifier that also functions as a bandpass filter with a high selectivity Q by using an operational amplifier OP2 as a center, resistors r4 to r7, and capacitors C3 to C5. The characteristics of the filter amplifier 5 for knocking amplification, that is, selectivity Q, center frequency fo, and amplification degree G are calculated by the following equations (2), (3), and (4) when both capacitors C3 and C4 are designed with capacitance C. expressed.

Q=20・log(√6・(15+14)/2)…
(2) fo=√(14+15)・² 6/2π …(3) G=0.5・r6/r5 …(4) Therefore, the center frequency fo of the filter amplifier 5 for knocking amplification is determined by this knocking detection device. It is easy to adjust to the knocking characteristic frequency fe of knocking that occurs in internal combustion engines. Similarly, the selectivity Q and the amplification degree G can be adjusted.

Next is the noise detection filter amplifier 7.
This amplifier 7 is designed and constructed with exactly the same circuit constants as the knocking amplification filter amplifier 5. That is, for that resistor, r14=r
4, r15=r5, r16=r6, r17=r7
And in the capacitor as well, C13=C3,C
14=C4 (C13=C14=C.)
And furthermore, operational amplifier OP3 is also operational amplifier OP2
The same thing is used. Then, operational amplifier OP3 is connected via capacitor C13 and resistor r14.
The input is short-circuited to the ground line. Therefore, this filter amplifier for noise detection has almost the same selectivity Q, center frequency fo, and amplification degree G as the filter amplifier 5 for knocking amplification, and is a knocking amplifier that inputs the low output impedance of the voltage follower 4. filter amplifier 5
It behaves in almost the same way with respect to noise superimposed on the power supply line or ground line. At this time, it is particularly preferable to use operational amplifiers OP2 and OP3 housed in the same package because the conditions will be the same.

The output of this noise detection filter amplifier 7 is input to an inverting amplifier 9. Here, the inverting amplifier includes resistors r20 to r23, capacitor C2
0 and an operational amplifier OP4, and its amplification degree is 1.

On the other hand, the adder circuit 11 is basically configured as an inverting amplifier, and the output signal V1 of the knocking amplification filter amplifier 5 is passed through the resistor r30.
, and a signal -V2 obtained by inverting the output signal V2 of the noise detection filter amplifier 7 by an inverting amplifier 9 via a resistor r31 and inputting the resultant signal. r32 and r34 are external resistors r3 that determine the amplification degree, output level, etc. of operational amplifier OP5.
5, r36 is a resistor for forming a virtual ground line, and C25 is a smoothing capacitor inserted between the virtual ground line and the earth line to lower the power source impedance.

As described in detail above, if the knocking amplification filter amplifier 5 is excited in response to noise that comes on the power supply line or the ground line due to disturbance, then the noise detection filter amplifier 7, which uses the same configuration, will also do the same. This produces an excitation of Therefore, the output signal V2 of the filter amplifier 7 for noise detection is inverted by the inverting amplifier 9, and this output -V2 is added to the output signal V1 of the filter amplifier 5 for knocking amplification by the adder circuit 11. circuit 1
The output signal Vout of 1 will be output as if no excitation had occurred.

Fig. 3 is a graph showing the relationship between the output signals V1, V2, and Vout, where a indicates the area affected by external noise on the ground line, and b indicates the area affected by the noise. The sections in which outputs are produced in each of the filter amplifiers 5 and 7 due to the excitation at the frequency o are shown. As a result of subtracting the output signal V2 from the output signal V1, almost no effect of excitation appears on the output signal Vout of the knocking detection device of this embodiment. Furthermore, the output signal
The reason why the effect of excitation remains on Vout is that noise on the ground line is observed when the potential difference with the ground line is measured, regardless of whether subtraction is performed or not.

Therefore, according to this embodiment, even if the selectivity Q of the knocking amplification filter amplifier that amplifies the output signal of the non-resonant knocking detection device 1 is increased by about 20 dB, the knocking amplification filter amplifier 5 that is generated due to this increase is The knocking vibration can be selectively detected without being affected by the excitation of the knocking. As a result, the characteristics of the non-knocking detection device, such as being able to easily respond to fluctuations in the knocking characteristic frequency and not requiring special tuning for each internal combustion engine, are maximized, and the selectivity is also improved. Therefore, it is possible to realize a knocking detection device that can detect knocking with high accuracy. Further, as mentioned above, since no special tuning or the like is required, the knocking detection device can be easily adjusted and installed when applied to each internal combustion engine, and manufacturing costs can be kept low.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way.
It goes without saying that the invention can be implemented in various ways without departing from the gist of the invention.

Effects of the Invention As detailed above, in the knocking detection device of the present invention, the noise detection filter amplifier shares the power supply line and the ground line with the knocking amplification filter amplifier, and is configured similarly to the knocking amplification filter amplifier. is used to detect the noise component generated by the excitation of the knocking amplification filter amplifier, and this detection signal is subtracted from the output signal of the knocking amplification filter amplifier.

Therefore, according to the knocking detection device of the present invention, the knocking detection characteristics can be easily adapted to each individual internal combustion engine, and the cost of the knocking detection device itself can be reduced, compared to the case where a resonance type knock sensor is used as the knock sensor. In addition to maximizing the characteristics of the non-resonant knock sensor, even if excitation occurs in the knocking amplification filter amplifier, the noise component due to the excitation contained in the output signal can be removed, and the subtracter Knocking in the internal combustion engine can always be accurately detected by the knocking detection signal output from the knocking detection signal.

Further, even if the knocking amplification filter amplifier is excited, knocking can be detected accurately, so the selectivity of the knocking amplification filter amplifier can be increased, and thereby also the knocking detection accuracy can be improved.

Furthermore, only one resonant type knock sensor can be used as the knock sensor, and the same configuration can be used for the knocking amplification filter amplifier and the noise detection filter amplifier, so the assembly process of the device can be simplified. , mass production can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a detailed circuit diagram thereof, and FIG. 3 is a graph showing the state of the output signal in the embodiment.
FIG. 4 is a graph illustrating excitation observed in a filter amplifier of a knocking detection device using a non-resonant knock sensor. 1...Non-resonance type knock sensor, 3...Battery, 4
... Voltage follower, 5... Filter amplifier for knocking amplification, 7... Filter amplifier for noise detection,
9... Inverting amplifier, 11... Adding circuit.

Claims (1)

[Claims for Utility Model Registration] A non-resonant knock sensor that is attached to an internal combustion engine and detects vibrations of the internal combustion engine; an output signal from the non-resonant knock sensor is input, and the output signal is sent to the internal combustion engine from among the output signals. a knocking amplification filter amplifier that selects and amplifies a signal near the knocking frequency that occurs; a knocking amplification filter amplifier that shares a power supply line and a ground line with the knocking amplification filter amplifier and is configured similarly to the knocking amplification filter amplifier; a noise detection filter amplifier that generates an excitation similar to the excitation that occurs in the knocking amplification filter amplifier due to noise input from a power supply line and a ground line; and a noise detection filter amplifier that uses the output of the knocking amplification filter amplifier. A knocking detection device comprising: a subtracter that subtracts the output of and outputs it as a knocking detection signal.