JPS6122141B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ignition timing control device for an internal combustion engine, and more particularly to a knock control device that detects and controls knocking in an internal combustion engine.

[Background of the invention]

Knocking in an engine is a dangerous phenomenon that can cause damage to pistons and exhaust valves, and in extreme cases, even destroy the engine, so in conventional ignition systems, a certain amount of margin is set aside from the ignition timing at which knocking occurs. The ignition timing control method, which sets the ignition timing on the delayed side, avoids serious problems caused by knocking.

This kind of knocking occurs frequently,
Moreover, the region where severe knocking is likely to occur continuously is during sudden acceleration from an idling state. However, in the conventional knock control device as disclosed in, for example, Japanese Unexamined Patent Publication No. 54-25334, when knocking occurs, the knocking is removed by delaying the ignition timing of the engine by a certain amount regardless of the engine speed. In addition, conventional knock control devices delay the engine ignition timing by a certain amount when knocking occurs, regardless of the engine speed, so the engine ignition timing is set to a delay amount that can cope with knocking at low speeds. In this case, the ignition timing performance at medium and high speed rotations is impaired, and the engine performance cannot be sufficiently exhibited.In general, however, the delay amount is such that the ignition timing performance at medium and high speed rotations can be achieved satisfactorily.

When knocking occurs in this way, the ignition timing is retarded by a certain amount to control the ignition timing so that knocking does not occur. That is, the ignition timing is retarded by a fixed amount every time one knocking occurs, and the ignition timing is retarded until the knocking disappears. Since the ignition timing at the time when the knocking disappears is not necessarily the optimum ignition position, the electronic advance action works again and the ignition timing is advanced.
That is, the return advance angle is performed. As a method of returning the advance angle, a conventional knock control device as disclosed in, for example, Japanese Unexamined Patent Publication No. 55-148966 controls the amount of advance according to the engine speed. That is, as the engine speed increases, the advance angle amount also increases.

[Problem that the invention seeks to solve]

However, in the case of the return advance method of such a conventional knock control device, for example, 6000 RPM
On the other hand, at an idle speed of 600 RPM, the advance angle is 1/10 of 6000 RPM, and at low speeds, the advance angle is so small that it does not actually advance. For this reason, there is a drawback that the ignition timing cannot be controlled to the optimum ignition timing in a substantially low speed rotation range.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a knock control device that can return to the optimum ignition timing in a short time after knocking is eliminated by knock control.

[Means for solving problems]

The present invention provides a method for eliminating knocking through knock control by advancing the return advance angle by a fixed amount per unit time and increasing the advance angle by a predetermined amount in proportion to the rotational speed. The idea is to return to the optimal ignition timing over time.

That is, the present invention includes a first means for detecting knocking in an internal combustion engine and outputting a knock signal, and a second means for delaying the ignition timing of the engine by a fixed amount for each knock signal output from the first means. and a third means for advancing the ignition timing by a certain amount per unit time and returning the ignition angle when knocking no longer occurs due to the retardation of the ignition timing by the second means. , further comprising a fourth means for adding an advance amount determined in proportion to the engine speed to the constant advance amount per unit time by the third means and outputting the result as the ignition timing of the engine. It is something to do.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 1 shows a block diagram of a knock control system comprising a knock control device and a non-contact ignition device.

In the figure, the knock control device includes a constant current circuit,
A fail-safe circuit consisting of a sensor short detection circuit, a sensor open detection circuit, and an abnormal signal detection circuit, an AC coupling circuit, an ignition noise cut circuit consisting of gates 1 and 2, a bandpass filter, a variable gain amplifier, a half-wave rectifier, and a knock voltage Consists of a mask circuit, integrators 1 and 2, and amplifier 2
AGC circuit, a background level output circuit that uses the output of the integrating circuit 1 as a background level, and a retard signal (pulse train) proportional to knocking by comparing the above background level (hereinafter abbreviated as BGL) voltage and signal. a comparator 1 that generates a signal, a comparator and an integrator 3 that similarly generate a retard signal (pulse train) by comparing the signal with a preset detection voltage, a retard signal generation circuit, and the retard signal Integrating circuit 2 that generates a DC voltage proportional to The lead angle signal output circuit includes means for decreasing the output voltage of the integrating circuit 2 at a rate of (constant voltage/period) during the output pulse of the circuit, and means for decreasing the output voltage for a constant period of time.

The non-contact ignition system consists of a pick-up coil (hereinafter abbreviated as PU coil) that detects the basic ignition timing, and a PU coil that detects the basic ignition timing.
It consists of an amplifier that shapes and amplifies the coil's output signal, a retard circuit that changes the ignition timing according to the output voltage of the knock control device, and a power transistor that generates a high voltage on the secondary side of the ignition coil. .

FIG. 2 shows a detailed circuit of the fail-safe circuit shown in FIG. 1.

In the figure, the knock sensor 1 is represented by an inductance 26 of about 1H, a resistor 21 of about 840Ω, resistors 2, 3, 4, 20, and a PNP transistor 2.
7. Connected to a constant current circuit consisting of Zener diodes 30 and 32. The Zener voltage of the Zener diode 32 is set to 6V, the output voltage (point voltage) of the operational amplifier 33 is set to 3V, and the collector current of the PNP transistor 27 is approximately
It is set to 1.7mA. Therefore, the point DC bias voltage is set to about 1.4 (V), and the knock sensor output signal has a waveform superimposed on the bias voltage as shown in FIG. 4C.

In addition, the output impedance Z of the knock sensor 1
is determined by the resistance 21 and the inductance 26, and the value at the knocking frequency (approximately 7KHz) is Z≒2πf ₀ L+R _Z1 =2π×7000×1+840≒45(KΩ) (1).

Therefore, if the input impedance of the connection part of the knock sensor 1 of the knock control device is low, the knock sensor 1
The input impedance needs to be high because the output signal from the device is greatly attenuated. Here, since the DC bias circuit has a constant current configuration, the impedance of the DC bias circuit section has a value close to infinity.

On the other hand, disturbance maze that increases the input impedance of the knock control device is likely to be superimposed, and as shown in FIG. 4C, ignition noise (hereinafter abbreviated as Ig noise) is superimposed in synchronization with the ignition timing.

In order to output a good knocking signal from the output signal from the knock sensor 1, it is necessary to cut off this Ig noise for a certain period of time after the ignition timing. The bias level of the output signal from 1 is converted to OV, and the monostable circuit as shown in FIG. 4B turns on the transistor 28 according to the output signal to remove Ig noise as shown in D.

Note that the resistors 5, 6, 14 and capacitors 22, 23 can be considered as the load impedance of the knock sensor 1, but by setting the resistor 14 to about 1MΩ, the resistors 5, 14 and the capacitor 23 can be ignored.
Therefore, the load on the knock sensor 1 is the capacitor 2.
2. Only counter 6 is considered.

By the way, here, capacitor 22 is
By setting 470PF and resistor 6 to 20KΩ, the vibration isolation frequency with inductance 26 is set to about 7KHz (it becomes a bandpass filter with low Q).

Through the above operations, the voltage waveform at the points in Figure 2 becomes as shown in Figure 4D.
110, capacitors 24, 25, operational amplifier 34
The waveforms of the bandpass filter (hereinafter abbreviated as BPF) and the output power (point voltage) are shown in Figure 4E.
It becomes as shown in . However, as will be described later, some noise is superimposed on BPE due to Ig noise, so an Ig noise mask is also required after BPF. In addition, the non-inverting terminal of the operational amplifier 34 is connected to the point (3V reference voltage)
The point DC bias voltage is
It is set to 3V.

Next, the retard signal output circuit will be explained using FIG. 3.

The output from the terminal 1b in FIG. 2 is input to the integrating circuit 1 through an amplifier and a half-wave rectifier as shown in FIG. The output value of the integrating circuit 3 is inputted to a comparator 100, which outputs a DC voltage proportional to the ground voltage (BGL voltage shown in FIG. 4E).
The BGL voltages are compared and a pulse that is greater than or equal to the BGL voltage is output to the knocking pulse comparator 100 as shown in FIG. 4F.

The knocking pulse output in this way is transmitted through the diode 107, capacitor 106, and resistor 104.
The signal is input to an integrator 3 consisting of. The waveform of the integrator 3 is as shown in FIG. 4G. Further, resistors 103 and 105 are connected to Vz to create an integrator 3 reference voltage (≈2V). Further, the comparator 101 compares the output of the integrator 3 with the reference voltage of the integrator 3, and outputs a pulse having a pulse width of FIG. 4H, which is proportional to the number of pulses from the knocking pulse. This pulse becomes the input to the 2d terminal in Figure 5,
The output of the integrator 2 increases according to the pulse width. On the other hand, the comparator 200 has its negative input terminal connected to a preset voltage Vco by resistor voltage division of counters 201 and 202. The positive input terminal is connected to the positive input terminal of the comparator 100, and the output of the knock signal amplifier is input thereto. Also, comparators 100 and 200
The output of the same resistor 102 and diode 107
connected to the cathode of Therefore, the connection point constitutes an AND circuit that becomes high level and generates a retard signal (pulse train) only when comparators 100 and 200 become high level at the same time.

In the circuit shown in Figure 3, the auto gain circuit allows
Although the signal amplifier and BGL output are always kept at a constant level, there is a limit to the amplification rate that can be set. Therefore, if BGL does not rise sufficiently due to low speed and the knock sensor output signal is small,
In the output of the comparator 100, even a small signal other than a knock signal is detected as if it were a knock signal. However, comparator 2
If the negative input terminal voltage Vco of 00 is set to the voltage necessary to detect the original knock signal,
If BGL is lower than Vco, due to the effect of AND configuration,
Priority is given to the output of the comparator 200, and a knocking pulse is generated at the connection point only when it is the original knocking signal. Also, the rotation speed increases and the BGL
When the voltage becomes higher than the voltage Vco and reaches a level at which the knock signal can be accurately grasped, the output of the comparator 100 takes priority.

According to the experimental results, good detection was achieved when the voltage Vco was set approximately 0.5V higher than the operating reference voltage of the knock signal amplifier.

FIG. 5 shows a detailed circuit diagram of the integrating circuit 2 shown in FIG. 1, which shows an embodiment of the present invention.

In the figure, the integrating circuit 2 includes capacitors 71 and 7.
2. A Miller integrating circuit consisting of an operational amplifier 85, an integrating circuit maximum voltage clamping circuit consisting of resistors 51, 51, 53, 56, and a diode 83, and an integrating circuit minimum voltage clamping circuit consisting of an operational amplifier 87, a diode 84, and resistors 54, 55. , the integrator circuit output voltage is configured to move between point voltages and point voltages. Further, the non-inverting terminal of the operational amplifier 85 is connected to the 2b terminal, and the 2b terminal is connected to the 1a terminal.
It is connected to the terminal and has 3V.

When the aforementioned knocking pulse is input to the 2d terminal, the transistor 76 is turned on through the resistor 63 in synchronization with the knocking pulse.

Therefore, if the pulse width of the knocking pulse is t _{O (} approximately 560 μsec) as shown in FIG _. flows in the direction shown in the diagram in FIG. 5, so that (voltage rise/pulse) ΔV ₁ of the operational amplifier 85 shown in FIG.
becomes as follows.

i ₁ = 3/R60∴ΔV ₁ = i ₁ /Ct ₀ ...(2) Here, C: parallel value of capacitors 71 and 72 R60: value of resistor 60 As can be seen from equation (2), the number of knocking pulses The output voltage of the operational amplifier 85 increases in proportion to.

On the other hand, every period, the output pulse of the monostable circuit (the fourth
The inverted waveform shown in FIG. B) is applied to the 2a terminal, and the transistor 77 is turned off for a certain period of time _t1 .

Therefore, the current i ₂ flows in the direction of the arrow shown in FIG.
flows, and the (voltage drop/period) Δ of the operational amplifier 85
V ₂ becomes:

i ₂ =6-3/R66+R67∴ΔV ₂ =i ₂ /Ct ₁ Also, the current i 3 is always flowing through the capacitors 71 and 72 from the resistors 610, 611, and 612, so that the current i ₃ always flows through the capacitors 71 and 72. is i ₂ +
The current of i ₃ flows, and the (voltage drop/
Period) ΔVc is ΔVc+ΔV ₂ +ΔV ₃ (ΔV ₃ ≒1deg/1sec: Depends on current i _3. ) Incidentally, in this example, the voltage increase Δ
The voltage drop ΔVc with respect to V ₁ is set to about 1/50 of ΔV ₁ .

Therefore, since the characteristics of the retard circuit of the non-contact ignition device are a constant angle slope characteristic with respect to the knock control device output voltage as shown in FIG. The amount by which the rotation proportional advance amount is increased by the constant advance angle amount per hit becomes the advance angle amount.

The Zener diode 81 is an approximately 6V Zener diode, and when the power supply voltage Vi is low (that is, when starting the engine with the starter ON),
Since the midpoint voltage between resistors 68 and 69 cannot turn on Zener diode 81, transistor 73 is turned off and transistors 75 and 78 are turned on. At this time, 75
Since it is ON, transistor 76 is OFF and
780N, a current flows from the power supply through the resistor 57 in the same direction as i ₂ , and the output of the operational amplifier 85 is
It decreases to the same voltage as the point and is clamped.

〔Effect of the invention〕

The ignition timing is retarded by a fixed amount every time one knocking occurs, and the ignition timing is retarded until the knocking disappears. However, the ignition timing at the time when the knocking disappears is not necessarily the optimum ignition position, so the electronic advance action comes into play again and the ignition timing advances. That is, the return advance angle is performed. In the present invention, the advance amount of the return advance angle is set to a constant advance amount per unit time, and is increased by an advance amount proportional to the rotational speed.

Therefore, according to the present invention, the optimum ignition timing can be returned to the optimal ignition timing in a short time after knocking is eliminated regardless of the engine speed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a knock control system to which the present invention is applied, Fig. 2 is a detailed circuit diagram of the fail-safe circuit shown in Fig. 1, Fig. 3 is a detailed circuit diagram of the slow signal output circuit, and Fig. 4 is a detailed circuit diagram of the fail-safe circuit shown in Fig. 1. 1 to 3 are main operating waveform diagrams, FIG. 5 is a detailed circuit diagram of an integral circuit of a knock control device showing an embodiment of the present invention, and FIG. 6 is a characteristic diagram of a retard circuit of a non-contact ignition device. FIG. 7 is a return advance angle characteristic diagram of this embodiment. 77, 78... Transistor, 85... Operational amplifier, 66, 67, 610, 611, 612...
Resistor, 71, 72... capacitor.

Claims (1)

[Claims] 1. A first means for detecting knocking of an internal combustion engine and outputting a knock signal, and a second means for delaying the ignition timing of the engine by a fixed amount for each knock signal output from the first means. In the knot control device, a third means for advancing the ignition timing by a certain amount per unit time and returning the advance when knocking no longer occurs due to the retardation of the ignition timing by the second means; A knock control device characterized in that a fourth means is provided for adding an advance amount determined in proportion to the engine speed to the constant advance amount per unit time by the means and outputting the result as the ignition timing of the engine. .