JPS5914631B2 - Internal combustion engine ignition timing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition timing control device for an internal combustion engine.

The ignition timing of an internal combustion engine is set in such a way as to provide the best efficiency for the operating conditions of the engine.

Generally, the engine should be as much as possible without knocking.
MBT (Minimum advance for Best
It is desirable to set the ignition timing so that it approaches the torque. However, most conventional ignition timing control devices are mechanical, and the ignition advance characteristics are not stable due to product variations or changes over time. Therefore, the actual ignition timing is set far behind the desired ignition advance characteristics described above to prevent knocking. This worsens the efficiency of the institution. Furthermore, even if an ignition timing control device that does not vary or change over time is used, knocking will occur under certain conditions because the knocking phenomenon is affected by the engine's intake air temperature, humidity, and air-fuel ratio. Even if the ignition timing is set to 1, knocking may occur under different operating conditions. Then, it detected knocking, and there was knocking! 0 If knocking occurs, if the ignition timing is controlled to be delayed, the ignition timing will be adjusted so that knocking will hardly occur even if there is an error in the ignition advance characteristics due to mechanical variations or differences in operating conditions as described above. be able to.

There are several ways to detect knocking, such as measuring combustion chamber pressure, engine vibration acceleration, and engine noise. Considering the above, the most practical method is to measure the vibration acceleration of the engine. However, in this method, mechanical vibration noise unrelated to knocking generated by the engine is simultaneously received along with the 90 knocking signal, so it is necessary to distinguish the knocking signal from the mechanical vibration noise. A known method for distinguishing a knocking signal from this mechanical vibration noise is to distinguish the vibration noise component from the knocking signal component based on the peak value. That is, by comparing a mixed signal of a noise component and a knocking signal component with a reference level that is higher than the noise component and lower than the knocking signal component, it is possible to extract only the knocking signal component. Here, if the above reference level is found from the peak value of the noise component, the condition of the reference level is that even if the peak value of the noise component changes due to a change in the engine speed, it is larger than the noise component and smaller than the knocking signal component. can be satisfied.

However, in the output signal of the vibration acceleration sensor, the knocking signal component is superimposed on the noise component when knocking occurs, so if the reference level is simply determined from the output signal component of the vibration acceleration sensor, the knocking signal component with a large peak value will also be added. Therefore, there has been a drawback that it is not possible to obtain an accurate reference level that corresponds only to noise components. This invention was developed in consideration of the above points, and when knocking occurs, a gate circuit prevents the knocking signal component from passing through the noise level detector ＼, thereby preventing the knocking signal component from contributing to the reference level. It is an object of the present invention to provide an ignition timing control device for an internal combustion engine that can accurately detect signal components.

Hereinafter, a detailed description will be given based on one embodiment shown in FIG. 3 is an analog gate, 4 is a noise level detector which is a level detector that detects the mechanical vibration noise level unrelated to engine knocking, and 5 is a frequency filter that passes frequency components that are sensitive to the above frequency. Output voltage of filter 2 and noise level detector 4
This is a comparator that compares the output voltages of and generates a knocking detection pulse, and its output is connected to be input to the analog gate 3 so that the analog gate 3 is closed during the generation period of the knocking detection pulse. 6 is an integrator that integrates the output pulse of this comparator 5 and generates an integrated voltage according to the knocking intensity of the engine, and 7 is a shifter that shifts the phase of the reference ignition signal according to the output voltage of the integrator 6. A phaser 8 has a preset ignition advance characteristic (this is set at least within a knocking region where the engine exhibits knocking).

) This is a reference ignition timing signal generator that generates a reference ignition signal according to the ignition timing signal generator, and is usually built into a power distributor, and by operating it, the above-mentioned ignition advance characteristics can be obtained. 9 is a waveform shaping circuit that shapes the output waveform of the reference ignition timing signal generator 8 and at the same time controls the closing angle of energization of the ignition coil H;
Reference numeral 0 designates a switching circuit that cuts off and on the power supply to the ignition coil 11 based on the output signal of the phase shifter 7.

The frequency filter 2, analog gate 3, noise level detector 4, and comparator 5 constitute a discrimination means. FIG. 2 shows the frequency characteristics of the output signal of the acceleration sensor 1.

A is a case where there is no knocking, and B is a case where knocking occurs. The output signal of the acceleration sensor 1 includes a knocking signal, a mechanical noise signal unrelated to engine knocking, and various noise components on the signal transmission path.
Comparing A (5B) in FIG. 2, it can be seen that the knocking signal has a unique frequency characteristic.

Although there are differences in this characteristic distribution due to differences in the engine itself or differences in the mounting position of the acceleration sensor 1, there is a clear difference in the distribution depending on the presence or absence of knocking. Therefore, by passing the frequency component of this knocking signal, the noise of other frequency components can be suppressed, and the knocking signal can be efficiently discriminated. Figures 3 and 4 show the operating waveforms of each part in Figure 1. Figure 3 shows a mode in which engine knocking does not occur, and Figure 4 shows a mode in which engine knocking occurs. It shows.

Next, the operation of this embodiment will be explained.

The reference ignition timing signal generated by the reference ignition timing signal generator 8 in accordance with the ignition timing characteristics preset by the rotation of the engine is waveformed into a pulse having a desired closing angle by the waveform shaping circuit 9, and then phase-shifted. switching circuit 10 via device 7
The engine is ignited and operated by the ignition voltage generated in the ignition coil 11 when the energization current is cut off.

Engine vibrations occurring during operation of the engine are detected by an acceleration sensor 1. Now, if knocking does not occur in the engine, engine vibration due to knocking will not occur, but
Due to other mechanical vibrations, mechanical vibration noise is generated in the output signal of the acceleration sensor 1, as shown in FIG. 3a. When this noise signal passes through the frequency filter 2, the mechanical noise component is considerably suppressed as shown in FIG. 3(b-a), and the level of the remaining noise component is lowered. On the other hand, since no knocking is occurring, no knocking detection pulse is generated in the comparator 5 and the analog gate 3 is open, and the noise level detector 4 detects the knocking signal from the output signal of the analog gate 3. The output signal of the analog gate 3 (Fig. 3c) is half-wave rectified, amplified, and smoothed so that it can respond to hidden changes such as mechanical vibration noise. generates a DC voltage slightly higher than the peak value of the vibration noise. (Fig. 3 b) Therefore, since the output voltage of the noise level detector 4 is higher than the output signal voltage of the frequency filter 2, the output of the comparator 5 that compares these is as shown in Fig. 3 d. Nothing is output, and all noise signals are eventually removed. Therefore, since the output voltage of the integrator 6 is zero as shown in FIG. 3e, the phase difference caused by the phase shifter 7 is also zero. Therefore, ignition coil 1
The intermittent phase of energization 1 is in phase with the output of the waveform shaping circuit 9, and the ignition timing of the engine is determined by the reference ignition timing signal generator 8.
The reference ignition timing is based on the reference ignition timing signal from
Ignition timing is not retarded. Next, when knocking occurs, the output of the acceleration sensor 1 includes a knocking signal at a certain time later than the ignition timing (a-F in FIG. 4) as shown in FIG. The signal after passing is a knocking signal largely superimposed on mechanical vibration noise unrelated to knocking, as shown in FIG. 4b-a.

Here, among the output signals of the frequency filter 2 that have passed through the analog gate 3, the rising of the knocking signal is steep, so the response of the noise level detector 4 is delayed, and the level of the output voltage is as shown in FIG. 4b. As shown, the output voltage is approximately constant and does not rise instantaneously. As a result, each input of the comparator 5 receives the output voltages shown in FIG. A pulse is generated, ie, only the knocking signal is discriminated.

The integrator 6 then integrates the pulse and generates an integrated voltage as shown in FIG. 4e. Then, the phase shifter 7 outputs a signal from the waveform shaping circuit 9 (FIG. 4(f)) according to the output voltage of the integrator 6.
) to the delayed side, the phase of the output voltage pulse of the phase shifter 7 lags the phase of the output voltage pulse of the waveform shaping circuit 10 by a predetermined angle, resulting in the phase shown in FIG. 4g. With this, the switching circuit 10 is driven. As a result, the ignition timing is delayed from the preset ignition timing, and the occurrence of knocking is suppressed. Here, when the comparator 5 detects the first knocking signal and generates the first output pulse, this first output pulse is given to the analog gate 3, so the analog gate 3 closes the gate. Then, the output signal in which the knocking signal is largely superimposed on the mechanical vibration noise from the frequency filter 2 that is output thereafter is prevented from being input to the noise level detector 4. Therefore, during the knocking detection pulse generation period of the comparator 5 due to knocking detection, the output signal of the frequency filter 2 on which the knocking signal is superimposed,
The output voltage level of the noise level detector 4, i.e. the comparator 5
Since the comparison voltage level never rises, there is no possibility that the knocking signal cannot be discriminated due to the comparison level rising due to a large output signal from the frequency filter 2, and the knocking signal can be reliably discriminated.
As described above, according to this embodiment, the output signal from the acceleration sensor 1 that detects the vibration acceleration of the engine is passed through the frequency filter 2 that passes the frequency components that are highly sensitive to knocking, and the comparator 5 outputs the output signal from the acceleration sensor 1. The output voltage of the frequency filter 2 and the output voltage of the filter 2 are rectified, amplified, and smoothed to produce a voltage that is a certain times the average DC voltage level of mechanical vibration noise that is unrelated to engine knocking. The knocking detection pulse can be discriminated by comparing the knocking detection pulse with the output of the noise level detector 4 which obtains the noise level. By closing the analog gate 3 provided between the detectors 4, the output voltage level of the noise level detector 4 is prevented from increasing due to the knocking signal, so that knocking can be detected accurately.

In addition, since the output voltage of the noise level detector 4, which detects the mechanical vibration noise level unrelated to engine knocking, is used as the comparison voltage of the comparator for generating knocking detection pulses, the comparison of the comparator 5 There is no need to set the voltage level in advance depending on the operating state of the engine, and the output signal level of the acceleration sensor 1 may vary slightly due to variations in the output signal level of the acceleration sensor 1 or due to aging etc. Even if the level changes slightly, there is no problem in detecting knocking, which is an excellent point. Furthermore, by changing the amplification degree of the amplifier circuit and the time constant of the smoothing circuit of the noise level detector 4, there is an advantage that there is a high degree of freedom in setting the comparison voltage level for knocking detection by the comparator.

In this way, optimal ignition timing can be obtained by accurately distinguishing the knocking signal from the output signal of the acceleration sensor 1 attached to the engine and controlling the ignition timing in accordance with the knocking signal. As described above, according to the present invention, the noise component is removed from the output of the acceleration sensor that detects engine vibration, and the ignition timing is delayed by the output of the discriminator that discriminates the knocking signal component, thereby suppressing the occurrence of knocking. By doing so, it is possible to control the ignition timing with good engine efficiency. Furthermore, the discriminating means for discriminating the knocking signal component includes a level detector that receives the output of the acceleration sensor and generates a comparison signal level necessary for discriminating the knocking signal component, and a level detector that receives the output of the acceleration sensor and generates a comparison signal level necessary for discriminating the knocking signal component, and a level detector that receives the output of the acceleration sensor and generates a comparison signal level necessary for discriminating the knocking signal component. By configuring the level detector to include a gate circuit that blocks the passage of the signal, the level detector can prevent problems such as variations in the comparison signal level due to the knocking signal component, and always generate a constant signal level. Therefore, the knocking signal component can be accurately discriminated, and suitable ignition timing control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention, and FIG.
The figure shows the frequency characteristics of the output signal a of the acceleration sensor 1, and FIGS. 3 and 4 show the operating waveforms of each part in FIG. 1. In the figure, 1 is an acceleration sensor, 2 is a frequency filter, and 3 is an acceleration sensor.
is an analog gate, 4 is a noise level detector, 5 is a comparator, 6 is an integrator, 7 is a phase shifter, 8 is a reference ignition timing signal generator, 9 is a waveform shaping circuit, 10 is a switching circuit, 1
1 is an ignition coil.

Claims (1)

[Claims] 1. An acceleration sensor that detects the vibrational acceleration of an internal combustion engine, a discriminator that removes noise components from the output of this acceleration sensor and discriminates knocking signal components, a reference ignition timing signal generator that generates a reference ignition timing signal, and the discriminator described above. phase means for displacing the phase of the reference ignition signal according to the output of the
and switching means for energizing the ignition coil on and off in synchronization with the output of the phase means, and the discrimination means generates a comparison signal level necessary for discriminating the knocking signal component in response to the output of the acceleration sensor. 1. An ignition timing control device for an internal combustion engine, comprising: a level detector for controlling the knocking signal; and a gate circuit for blocking the output of the acceleration sensor from passing through the level detector when the knocking signal component occurs.