JPS6368774A - Spark plug preignition detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To make whether there is preignition or not detectable, by making normal ignition timing detectable with an ignition voltage signal to be impressed on a spark plug itself, while eliminating any ignition noise of an ion current on the basis of the detected ignition timing. CONSTITUTION:An ignition timing detector 13a takes its input signal from a connecting point between a high tension diode 8 and an ion current detecting resistor 9 just like an ion current detector 14 instead of taking it from an ignition coil 6 for ignition use, whereby flying spark timing at a spark plug 11 is detected. On the other hand, the ion current detector 14 converts an ion current flowing between both electrodes of the spark plug 11 into a voltage signal and detects it. And, an ignition noise getting on the detected ion current is dropped to an earth level and eliminated by an ignition noise eliminator circuit 15. In addition, only the ion current flowing before the normal ignition timing at the sparkplug 11 is detected by a preignition discriminator 17, whereby whether there is preignition or not is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pre-ignition detection device for detecting premature firing of a spark plug for internal combustion.

[Prior art 1] When an internal combustion engine overheats during operation, the temperature of the spark plug rises and the tip of the insulator becomes hot, causing pre-ignition of the air-fuel mixture before the spark plug's normal ignition timing. ) and start to burn, and if this progresses further, the operation will become unstable/it will cause the piston to melt, seize, etc. −
As a pre-ignition detection device for detecting such premature ignition of a spark plug, one having a circuit configuration shown in 2 in FIG. 4 is known.

In addition, 1 is the ignition power supply circuit, battery 3, capacitor 4
, a point 5, and an ignition coil 6 for ignition, and the current in the primary winding of the ignition coil 6 is intermittent by opening and closing of the point 5. The pre-ignition detection circuit 2 detects pre-ignition using the ionic current flowing between the two electrodes of the spark plug. When a flame occurs, the ions in the flame cause a current to flow, so this ion current is detected to determine the presence of a flame, and if this is detected before the official ignition timing, it is determined to be pre-ignition. be. Therefore, a DC voltage is applied from the DC high voltage power supply 10 between the two electrodes of the spark plug 11 via the ion current detection resistor 9 and the high voltage diode 8, and ions are generated between the two electrodes of the spark plug 11 due to combustion of the air-fuel mixture. It measures the concentration-dependent ionic current (flowing along the loop-shaped path 12). The ignition timing detection circuit 13 detects ignition timing by detecting intermittent current in the primary winding of the ignition coil 6.

In addition, an ignition noise removal circuit 15 is added that removes ignition noise during ignition and improves the detection accuracy of pre-ignition. During the crank angle,
The structure is designed to eliminate ignition noise. However, the ignition system for recent small gasoline internal combustion engines, especially for general-purpose engines and small motorcycles, has become smaller and lighter.
The structure shown in the figure is often used for ignition coils,
(Primary winding 19, secondary winding 20) Iron core 24 and electronic control circuit 22 that determines ignition timing, etc. are 4-plus case 23
It is integrated with an insulating filler 25 inside, making it impossible to extract a signal for detecting the idle flame IF period from the first wire 19 following the ignition coil for ignition. 21 is a high voltage cord. Therefore, since the ignition noise removal circuit cannot be activated, there is a problem that premature ignition of the spark plug cannot be accurately detected.

1-Problems to be Solved by the Invention] The present invention provides an ignition signal from the primary winding of the ignition coil for ignition, such as an integrated ignition coil and electronic control circuit. To provide a pre-ignition detection device capable of detecting ignition timing even in an ignition device in which P cannot be removed, operating an ignition noise removal circuit based on this ignition timing, and accurately detecting over-ignition at a spark plug. With the goal.

[Means for solving the problem] An ion current detection circuit that detects the ion current flowing between both electrodes of a spark plug, an ignition timing detection circuit that detects the regular ignition timing of the spark plug, and a detected ion current an ignition noise removal circuit that removes ignition noise from the
In the pre-ignition detection device, the ignition timing detection circuit includes a circuit that determines the presence or absence of pre-ignition based on whether an ion current is detected before the normal ignition timing. The normal ignition timing is detected based on the applied ignition voltage signal, and the ignition noise removal circuit is activated based on the detected ignition timing. Further, the ignition voltage signal applied to the spark plug is detected using an ionic current flowing between both electrodes of the spark plug, or by directly inputting it from a spark plug terminal.

[Operation] The ignition timing detection circuit detects ignition timing using the ignition voltage signal applied to the spark plug itself. Further, the ignition noise removal circuit operates based on the detected ignition timing to remove ignition noise of the ion current, thereby detecting the presence or absence of pre-ignition. In addition, the ignition timing detection circuit is
This ignition voltage signal is detected by detecting the ignition voltage signal superimposed on the ion current or from the ignition voltage signal applied to the spark plug terminal.

[Example] A first example of the pre-ignition detection device according to the present invention is described below.
As will be explained with reference to the drawings, compared to the conventional circuit shown in FIG. Similarly, the difference is that the connection point between the high-voltage diode 8 and the ion current detection resistor 9 is used, and the configuration of the ignition Fj1 period detection circuit 13a is also different due to this.

In FIG. 1, 13a is an ignition timing detection circuit that detects the flying timing of the spark plug 11, that is, the normal ignition timing, more precisely, the point immediately before that, and 14 is the spark plug 1
an ion current detection circuit that converts and detects an ion current flowing through both electrodes m (spark gap) of 1 into a voltage signal;
5 is an ignition noise removal circuit that removes the ignition noise carried by the detected ion current by reducing it to the ground level; 16 is an ignition noise removal circuit r11 (flying sparks) during normal ignition with the spark plug 11;
The oscilloscope 17 detects the ion current that flowed before and the ion current that flowed after sparking, and detects only the ion current that flowed before the regular ignition timing (flying spark) in the spark plug 11. A pre-ignition discrimination circuit that determines the presence or absence of pre-ignition and generates a voltage pulse in the case of pre-ignition; 18 is an alarm device that issues an alarm such as sound or light in response to the output of the pre-ignition discrimination circuit 17; It is.

The ignition timing detection circuit 13a has the configuration of 13a in FIG. A capacitor that detects only the induced voltage of the applied high voltage ignition voltage and the change in the ion current flowing between the two electrodes of the spark plug 11; 31 is a diode that removes only the positive component of the change in the ion current; 32 33 is an amplifier mainly used to lower the output impedance of the induced voltage signal of the ignition voltage, and 33 is an amplifier that converts the voltage obtained from the trigger level setting variable resistor 34 and the voltage obtained from the amplifier 32. A trigger position detector 35 detects the ignition position by comparison, a waveform shaper 36 shapes the signal obtained from the trigger position detector 33, and obtains one square wave per spark. This is an ignition noise removal time setting device that sets the width of the output square wave of the waveform shaper to a constant width and determines the ignition noise removal time.

The operation will be explained with reference to the signal waveform diagram of each part in FIG. 3. In FIG. 2, when spark plug 11 sparks, the spark voltage waveform detected by high voltage diode 7 is as follows.
The signal obtained from the connection point between the high-voltage diode 8 and the ion current detection resistor 9 through only the DC component removal capacitor +J3o is as shown in FIG. 3(b).
It includes the ignition voltage waveform (bl), ignition noise (b2), and ion voltage waveform (b3) at the time of sparking at the spark plug 11. From the waveform in Figure 3(b),
A diode 31 is connected mainly to take out only the ignition voltage waveform (bl), and an amplifier 32 is used to output the ignition voltage waveform (bl) as shown in FIG.
Current amplification and appropriate voltage amplification of the (bl) and (b2) waveforms are performed to obtain the ignition voltage waveform shown in FIG. 3(C). (C') in FIG. 3(C) is the voltage level set by the trigger level setting variable resistor 34, and the voltage level (C') in FIG.
) are compared to generate multiple square waves from one ignition voltage waveform.
Figure (d) is obtained. The first rise of the obtained square wave is several microseconds earlier than the actual ignition position, but since the error in ignition timing is less than 1°, it is acceptable as a practical ignition position. The waveform shaping circuit 35 is shown in FIG.
In order to shape the waveform of d) into one square wave for one ignition voltage waveform, there is a waveform shaping circuit equipped with an integrator and a comparator, and the output square wave is as shown in Fig. 3(e). The rise of the square wave corresponds to the above-mentioned ignition position. The ignition noise removal time setting circuit 36 is
A monostable circuit that receives the output of the waveform shaper 35 and operates at the rising edge of the waveform shaper 35 generates a fixed time width (T in FIG. 3(f)).
) is configured to output a square wave (FIG. 3(f)), and sends a signal to the ignition noise removal circuit 15 in FIG. Eliminates ignition noise. The operations of the oscilloscope 16, the pre-ignition discrimination circuit 17, and the alarm 18 are as described above.

In addition, in the ignition timing detection circuit 13a of FIG. 2, an amplifier 3 is used to reduce the output impedance of the voltage waveform.
2 is used, but it may be omitted if the input impedance of the comparator in the trigger position detection F:33 is high. Furthermore, the waveform shaper 35 may be omitted if the monostable circuit of the ignition noise removal time setting device 36 has a re-trigger prevention function. Further, although the same human signal line as the ion current detection circuit 14 is used as the input of the ignition timing detection circuit 13a, another signal line may be prepared for detecting the spark voltage at the spark plug 11. Terminal section 11
The high voltage for ignition may be directly divided by voltage dividing resistors 12a and 12b from a, and a configuration as shown in FIG. 6 may be adopted. When the ignition voltage waveform is divided, its absolute value is large, so the DC high voltage and ion voltage become relatively small signals that can be ignored.
1 is unnecessary, and the output impedance becomes a signal with a considerably low value, so the amplifier 32 is not necessary.

[Effect of the invention] The ignition timing detection circuit of the pre-ignition detection device detects the normal ignition timing by using the ignition voltage signal itself applied to the spark plug from the ignition power supply circuit when the spark plug is ignited. The ignition timing can be accurately detected even in an ignition device in which the ignition timing signal cannot be extracted from the primary winding of the ignition coil, such as a molded ignition device with an ignition coil and electronic control circuit integrated.

In addition, since the ignition voltage applied to the spark plug itself to be detected is used, even when the ignition voltage is distributed to multiple cylinders with one coil, the ignition timing of cylinders that are not subject to pre-ignition detection is not detected, so other It is possible to accurately detect premature arrival without being affected by the cylinder. In addition, conventionally, a signal line for detecting ignition timing was required from the ignition coil-next winding, but when detecting the ignition voltage signal from the ion current, only the input signal line for the ion current detection circuit needs to be wired. For example, wiring to the ignition timing detection circuit becomes possible, which simplifies the circuit. In addition, when the ignition voltage signal is input as a divided voltage directly from the spark plug terminal, its absolute value is large, so compared to the case where the ignition voltage signal is detected from the ion current, capacitors, diodes, etc. are not required, and the circuit is simpler. becomes.

Further, since ignition noise superimposed on the ion current is removed based on the ignition timing detected in this way, pre-ignition can be accurately detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a pre-ignition detection device 2 according to the present invention together with an ignition power supply circuit, FIG. 2 is a block diagram of the ignition timing detection circuit of FIG. 1, and FIG. 3 is a block diagram of the ignition timing detection circuit of FIG. FIG. 4 is a block diagram showing a conventional pre-ignition detection device together with an ignition power supply circuit; FIG. 5 is a sectional view of a molded ignition device; FIG. FIG. 6 is a block diagram showing another embodiment of the ignition timing detection circuit used in the present invention. In the figure, 1... Ignition power supply circuit, 2a... Preignition detection device 11... Spark plug, 13a... Ignition timing detection circuit, 14... Ion current detection circuit, 15... Ignition Noise removal circuit.

Claims (3)

[Claims] (1) An ion current detection circuit that detects the ion current flowing between both electrodes of a spark plug of an internal combustion engine, an ignition timing detection circuit that detects the regular ignition timing of the spark plug, and ignition noise from the detected ion current. a pre-ignition detection device including an ignition noise removal circuit that removes ignition noise, and a circuit that determines the presence or absence of pre-ignition based on whether or not the ion current detected by the ion current detection circuit is detected before the regular ignition timing. In the ignition timing detection circuit, the ignition timing detection circuit detects the regular ignition timing based on the ignition voltage signal applied from the ignition power supply circuit when the spark plug is ignited, and also controls the ignition noise removal circuit based on the detected ignition timing. A pre-ignition detection device for a spark plug for an internal combustion engine, characterized in that the device operates a spark plug for an internal combustion engine. (2) The pre-ignition detection device according to claim 1, wherein the ignition timing detection circuit inputs the ion current, and when the spark plug is ignited superimposed on the ion current, the ignition timing detection circuit A pre-ignition detection device for a spark plug for an internal combustion engine that detects the regular ignition timing based on an ignition voltage signal applied from a circuit. (3) The pre-ignition detection device according to claim 1, wherein the ignition timing detection circuit receives an ignition voltage signal applied to the spark plug from an ignition power supply circuit at the time of ignition from a terminal of the spark plug. A pre-ignition detection device for a spark plug for an internal combustion engine that detects the regular ignition timing by directly inputting it.