JPS633557B2 - - 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. In general, as much as possible without the agency noticing.
MBT (Minimum advance for Best Torque)
It is desirable to set the ignition timing so that it approaches . However, most of the ignition timing control devices that have been installed in the past are mechanical, and the ignition advance characteristics are not stable due to product variations or changes over time. Therefore, in order to prevent knocking, the actual ignition timing is set much later than the above-mentioned desired ignition advance characteristic. This worsens the efficiency of the institution. In addition, even if an ignition timing control device that does not change over time is used, the knocking phenomenon will depend on the engine's intake air temperature and humidity, as well as the air-fuel ratio, so knocking will not occur under certain conditions. Even if the ignition timing is set, knocking may occur under different operating conditions.

Therefore, knocking is detected using a vibration acceleration sensor installed in the engine and a knocking discrimination means.
If knocking occurs, the ignition timing will be delayed by controlling the ignition timing so that knocking will hardly occur even if there are errors in the ignition advance characteristics due to mechanical variations or differences in operating conditions as described above. Can be matched. However, if the sensor or electric circuit that detects engine vibration breaks down or malfunctions during engine operation, the knocking detection force will not be generated even though knocking is occurring.
Therefore, the ignition timing is not retarded and there is a risk of premature ignition.

This invention detects a knock signal from the output of a vibration sensor of an engine and controls the ignition timing according to the knock signal, and detects a failure of the knock detection device from the noise signal level of the output of the vibration sensor. By retarding the ignition timing using this detection force, the purpose is to prevent premature ignition due to the inability to retard even in the event of a failure of the knock detection device, and to enable safe engine operation. .

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an acceleration sensor that is attached to the engine and detects vibration acceleration of the engine, and 2 is an acceleration sensor 1.
The filter suppresses noise components other than the knock signal from the output signal, and includes a frequency filter that allows only a predetermined frequency signal to pass, and a timing filter that blocks the passage of a signal at a predetermined angular position. 3 is a noise level detector that detects the mechanical vibration noise level of the engine other than when knocking; 4
is the output voltage of filter 2 and noise level detector 3
5 is an integrator that integrates the output pulse of the comparator 4 and generates an integrated voltage according to the knocking intensity. A phase shifter 8 retards the phase of the reference ignition signal in accordance with the output voltage of the integrator 5, which is applied to the phase shifter 6 when the output voltage of the noise level detector 3 is lower than the set voltage Vr. The phase shifter 6 is controlled via the synthesis circuit 7 by a comparator that generates a retard control voltage output for providing a predetermined amount of retard. 9 is a rotation signal generator that generates an ignition signal according to a preset ignition advance characteristic; 10 is a waveform shaper that shapes the output of the rotation signal generator 9 and at the same time controls the closing angle of energization of the ignition coil 12; A circuit 11 is a switching circuit that cuts off and on the power supply to the ignition coil 12 based on the output signal of the phase shifter 6.

Figures 2 and 3 show the operating waveforms of each part in Figure 1. Figure 2 shows a mode in which engine knocking does not occur, and Figure 3 shows a mode in which engine knocking occurs. ing.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

The rotation signal generated by the rotation signal generator 9 in accordance with the ignition timing characteristics set in advance by the rotation of the engine is waveform-shaped by the waveform shaping circuit 10 into opening/closing pulses having a desired closing angle. The switching circuit 11 is driven through the ignition coil 12.
The engine is ignited and operated by the ignition voltage of the ignition coil 12 that is generated when the power supply is interrupted. Engine vibrations occurring during operation of the engine are detected by an acceleration sensor 1.

Now, if engine knocking does not occur, engine vibration due to knocking will not occur, but
Due to other mechanical vibrations, the output signal of the acceleration sensor 1 generates mechanical noise and ignition noise on the signal transmission path at the ignition timing F, as shown in FIG. 2a. These noises are suppressed by the frequency characteristics of the filter 2, and the output signal of the filter 2 becomes as shown in FIG. 2b. On the other hand, the noise level detector 3 responds to changes in the peak value of the output signal of the filter 2, and in this case, has the characteristic of being able to respond to relatively gradual changes due to the peak value of normal mechanical noise. (See Figure 2b, b).

Therefore, as shown in A and B of Fig. 2b, the output of the noise level detector 3 is larger than the average peak value of the output signal of the filter 2, so the output of the comparator 4 that compares them is As shown in Fig. 2c, nothing is output, and eventually all noise signals are removed. Therefore, the output voltage of the integrator 7 remains zero as shown in FIG. 2d, and the phase shift angle (phase difference between input and output) by the phase shifter 6 also becomes zero. This output is switching circuit 1
Drive 1. Therefore, the intermittent phase of energization of the ignition coil 12 is in the same phase as the reference ignition timing signal output from the waveform shaping circuit 10, and the ignition timing becomes the reference ignition position.

In addition, when knocking occurs, the output of the acceleration sensor 1 includes a knock signal at a certain time later than the ignition timing F as shown in Fig. 3a, and the signal after passing through the filter 2 is shown in Fig. 3b. As shown in (a), the knock signal is largely superimposed on the mechanical noise. Among the signals passed through this filter, the rise of the knock signal is steep, so that the response of the output voltage level of the noise level detector 3 to the knock signal is delayed. As a result, the inputs of comparator 4 are
As shown in FIG. 3B, a pulse is generated at the output of the comparator 4 as shown in FIG. 3C. An integrator 5 integrates the pulses and produces an integrated voltage as shown in FIG. 3d. Then, the phase shifter 6 outputs a signal from the waveform shaping circuit 10 according to the output voltage of the integrator 5 (Fig. 3e).
In order to shift the phase of the output of the phase shifter 6 to the delay side, the phase of the output of the phase shifter 6 lags behind the phase of the reference ignition timing signal of the waveform shaping circuit 10, and as shown in FIG.
Drive 1. As a result, the ignition timing is delayed, the occurrence of knocking stops, and a knocking-free state is achieved.

In this way, the control system becomes a closed loop control in the order of engine → engine knock detection → ignition timing control → engine. Then, the control point settles at an advanced point where the charging/discharging voltage of the integrator 5 is balanced, which is determined by the output pulse of the comparator 4 caused by the occurrence of knocking. Since this control point is the limit point at which knocking occurs, it is the maximum output point within a range where knocking hardly occurs, and it can be said that the ignition timing has been set to provide good engine efficiency.

By the way, in such a control system, if the input to the circuit section that selects the knock signal from the output of the acceleration sensor 1 is cut off due to a failure of the acceleration sensor 1 or a disconnection of its output lead wire, etc. The output voltage (knock signal output) that should be generated from the integrator 5 in order to control the amount of retardation of the phase shifter 6 is zero (zero).
Therefore, the retard control using the knock signal as described above becomes completely impossible, but at this time, the noise level detector 3 also does not receive the engine vibration output of the acceleration sensor 1, so the output voltage of the noise level detector 3 is below the set voltage Vr (always under normal conditions)
Vr or higher), therefore, the comparator 8 generates a control voltage output of a predetermined magnitude, and outputs the control voltage to the phase shifter 6 via the synthesis circuit 7.
control. Therefore, the phase shifter 6 is controlled by the waveform shaping circuit 10 by a predetermined retard amount θ ₀ by the control voltage of the comparator 8.
Therefore, the ignition timing of the engine is retarded by the predetermined retard amount θ ₀ from the generation timing of the reference ignition timing signal generated in accordance with the reference ignition advance characteristic. Control.

Therefore, even in a state where ignition timing control using the knock signal becomes impossible due to a failure of the sensor unit, the ignition timing is not directly determined by the advance characteristic of the reference ignition timing signal, and the ignition timing is controlled to be delayed. Therefore, it is possible to prevent malfunctions and adverse effects on the engine due to over-advanced ignition, and to enable safe engine operation.

On the other hand, engine vibrations that occur during engine operation become larger as the engine speed increases, but especially at low speeds, the output level of the acceleration sensor 1 decreases and the output voltage of the noise level detector 3 decreases. Because the voltage may drop below the set voltage Vr,
Even though the acceleration sensor 1 and the like are operating normally, there is a possibility that the comparator 8 will generate an output because it is determined to be malfunctioning, thereby retarding the ignition timing. In such a case, as shown by the dotted line block in FIG.
3, and this output prevents the generation of the control output of the comparator 8 below a predetermined rotation speed, and performs retard control by the comparator 8 only at a predetermined rotation speed or above, then proper ignition timing can be achieved. can be obtained.

In the above embodiment, the output level of the noise level detector 3 is detected in order to detect an abnormality in the acceleration sensor 1, but the output level of the noise level detector 3 is detected.
It is also possible to detect based on a signal containing a noise vibration component of the input and output parts, and in short, it is sufficient to detect whether it is normal or abnormal using at least the noise signal of the output of the vibration sensor.

As described above, the present invention retards the ignition timing using an engine knocking signal, and detects an abnormality in the sensor based on the output signal of the vibration sensor, and in the event of an abnormality, retards the ignition timing forcibly using the phase shift means. This makes it possible to prevent premature ignition due to the reference ignition timing signal even if a sensor malfunction occurs, and also prevents the above-mentioned retardation due to an abnormality in the sensor etc. when the engine speed is low below a predetermined value. Since the operation is disabled and ignition is performed using the reference ignition timing signal, unnecessary retardation of the ignition timing can be prevented, and more appropriate ignition timing control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are waveform diagrams for explaining the operation of FIG. 1. In the figure, 1 is an acceleration sensor, 2 is a filter, 3 is a noise level detector, 4 is a comparator, 5 is an integrator,
6 is a phase shifter, 7 is a combining circuit, 8 is a comparator, 9 is a rotation signal generator, 10 is a waveform shaping circuit, 11 is a switching circuit, 12 is an ignition coil, and 13 is a rotation speed detection circuit.

Claims (1)

[Claims] 1. A vibration sensor that detects vibrations of the engine, a noise level detector that detects the vibration noise level of the engine from the output signal of this vibration sensor and outputs a DC voltage according to the noise level, and an output of this noise level detector. and an output of the vibration sensor to discriminate a knocking signal component from the output signal of the vibration sensor; Based on the outputs of the first and second comparing means, A phase shifting means for retarding the reference ignition timing signal by shifting the phase of the output signal of the reference ignition timing signal generating means, and a switching circuit that is controlled to open and close by the output signal of the phase shifting means and intermittent the power supply to the ignition coil. , comprising a rotation speed detection means for detecting that the rotation speed of the engine is below a predetermined value, and when the engine rotation speed is below the predetermined value, the retardation is performed by the second comparison means based on the output of the rotation speed detection means. An ignition timing control device for an internal combustion engine, characterized in that the ignition timing control device is configured to disable the control.