JPS6161971A - Ignition device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve firing performance of an ignition plug in no relation to its stain by carbon, by monitoring the waveform of a high voltage pulse supplied to the ignition plug and supplying again the high voltage pulse to the ignition plug when abnormality of the waveform caused by a decrease of insulation resistance due to a stain by a carbon is discriminated. CONSTITUTION:A high voltage pulse Pi, generated in the secondary side of an ignition coil 23 in a high voltage pulse generating means 21, is both distributively supplied to an ignition plug 25 through a distributor 24 and input to a discriminating means 27 through an attenuator 26. The discriminating means 27 while inputs a comparison signal Sc from a comparison signal generating means 28 and an ignition timing signal Si. And this discriminating means 27, detecting a waveform of high voltage pulse Pi, obtains a number of peak pulses whose peak value increases to a predetermined reference value or more. And the discriminating means 27, outputting a redischarge signal when said number of peak pulses is smaller than the number of compared pulses in the comparison signal, causes the high voltage pulse generating means 21 by this redischarge signal to generate again the high voltage pulse in the ignition timing.

Description

[Detailed description of the invention] (Technical field) The present invention relates to an ignition device for an internal combustion engine.

(Prior Art) In a spark ignition type internal combustion engine, it is desirable to reliably ignite the air-fuel mixture with a small number of ignition engines. Therefore, attempts have been made to satisfy the conflicting demands of improving ignition performance and reducing the amount of electrode consumption of the spark plug by changing the energy distribution of the ignition device depending on the operating conditions.

As a conventional ignition device for this type of internal combustion engine, there is one described in, for example, Japanese Unexamined Patent Publication No. 14075/1983.
It is shown as in FIG.

In FIG. 5, 1 is an engine condition discrimination circuit, and the engine condition discrimination circuit 1 selects the next A to C based on each signal from the starter switch 2, water temperature switch 3, rotation speed switch 4, and intake pressure switch 5. The operating condition shown in FIG.

A: At engine start B: At high speed, light load with poor ignitability and at low water temperature C: At low speed, high load and high water temperature with good ignitability The ignition control circuit 6 further receives an ignition timing signal from the ignition signal generation circuit 7. Si is input, and when the ignition timing signal Si is input, the ignition control circuit 6 calculates the frequency of occurrence under these conditions A to C according to the conditions A to C as shown in Table 1 below. The primary current of the ignition coil 8 is controlled to solve the high problem of high voltage pulse Pi generated by the ignition coil 8.

Table 1 High voltage pulses Pi from the ignition coil 8 are distributed and supplied to the ignition plugs 10 disposed in each cylinder via the distributor 9.

Therefore, the ignition energy is changed according to the operating conditions. Under condition A, the ignition plug 10 is prevented from being contaminated by smoldering, under condition B, the ignition ability is improved, and under condition C, the amount of electrode consumption of the ignition plug 10 is reduced. This will be reduced.

However, in such conventional ignition devices,
The configuration was such that the operating conditions were simply determined as either one of A-C, and the high-pressure pulse was controlled to solve the most frequently occurring problem D-F under these conditions A-C. Even if the frequency of occurrence is low, it is not always possible to adequately answer questions such as D to F for situations that are determined based on discrimination contents other than A to C.

For example, the reduction in ignition ability occurs not only when the water temperature is low as in condition B, but also due to carbon contamination in which carbon is deposited on the surface of the insulator of the spark plug. Therefore, it is difficult to judge the decrease in ignition ability due to such carbon contamination based on condition B, a so-called external factor other than the ignition device. For this reason, especially when accelerating the engine at low water temperatures where the promotion of atomization of the air-fuel mixture is reduced, only measures corresponding to condition B are implemented, even though carbon contamination is likely to occur. The measure of condition A to solve the stain is not executed. As a result, the ignition ability is reduced and engine drivability is deteriorated.

On the other hand, in order to avoid such problems, for example, if the discrimination between conditions A and C is made gentler, there is a risk that the ignition energy will be increased to the point where carbon contamination countermeasures are not required, and the amount of electrode wear will increase. This causes a new problem.

(Objective of the Invention) Therefore, the present invention monitors the waveform of the high-voltage pulse supplied to the ignition plug, instead of determining the external factors mentioned above, and ignites when an abnormality in the waveform due to a decrease in insulation resistance due to carbon contamination is determined. By supplying high-pressure pulses to the plug again, the discharge energy during the same ignition timing is increased, improving ignition performance despite carbon contamination, reducing electrode wear and improving engine drivability. The purpose is to

(Structure of the Invention) The ignition device for an internal combustion engine according to the present invention, as shown in the overall configuration diagram in FIG. Comparison signal generation means 2 that outputs a comparison signal having a comparison pulse number
Detecting the waveform of the high-voltage pulses supplied to the spark plug 25 and determining the peak pulse number whose peak value is equal to or higher than a predetermined reference value, and when the peak pulse number is less than the comparison pulse number, a re-discharge signal is generated. and a high-voltage pulse generating means 21 that generates the high-voltage pulse at each predetermined ignition timing and generates the high-voltage pulse again during the ignition timing when a re-discharge signal is input.
．． 51, which increases the discharge energy during the same ignition timing when carbon contamination occurs.

(Example) The present invention will be explained below based on the drawings.

2 to 4 are diagrams showing a first embodiment of the present invention, and show an example in which the present invention is applied to a 4-stroke, 4-cylinder engine.

First, the configuration will be explained. In FIG. 2, 21 is a high voltage pulse generating means, and the high voltage pulse generating means 21 is composed of a monostable multivib break 22, an ignition coil 23, a transistor Q1, and a distributor 24. An ignition timing signal Si is input to the monostable multi-high break 22 at a predetermined ignition timing corresponding to the operating state, for example, from a control unit (not shown), and
When the waveform of a high voltage pulse P1 supplied to the spark plug, which will be described later, is abnormal, a re-discharge signal Sr is input. When the monostable multi-bibreak 22 receives these signals Si and Sr, it outputs a rectangular ignition primary signal S1 having a predetermined pulse width to the transistor Q1 in synchronization with the rising edges thereof. Transistor Ql is the ignition primary signal S□
It turns off at the falling edge of , cutting off the primary current of the ignition coil 23 and generating a high voltage pulse Pi on the secondary side of the ignition coil 23. The distributor 24 sends high-pressure pulses P to four spark plugs 25 in synchronization with engine rotation.
Distribute and supply i sequentially.

The high voltage pulse Pi is inputted to the discrimination means 27 via an attenuator 26 consisting of resistors R1 and R2, and the discrimination means 27 is further supplied with a comparison signal Sc from a comparison signal generation means 28.
is input, and at the same time, the ignition timing signal Si is input.

Comparison signal generation means 2nd is signal disk plate 29
The signal disk plate 29 is attached to the crank pulley and has four protrusions 31 made of a magnetic material every 90 degrees on its outer circumference. The pickup 3° is disposed facing the signal disk plate 1, 29 at a predetermined distance, and generates a predetermined magnetic field on the side facing the signal disk plate 29. Comparison signal generation means 2
8, the pickup 3o is activated by the protrusion 31 cutting this magnetic field by the rotation of the signal disk plate 29.
A pulse-like comparison signal Sc is generated. I wanted to,
The comparison signal Sc has four pulses (
Hereinafter, the number of comparison pulses (hereinafter referred to as comparison pulses will be expressed as ph) is included, and the number of comparison pulses ph is twice the number of ignitions.

Note that the signal disc plate 29 is not limited to crank pulleys, ring gears, etc., but can also be used, for example, with the distributor 2.
It may be attached to the rotor shaft or camshaft of No. 4. In that case, the number of protrusions should be twice that of the above example, that is, 8.
Similarly, it is sufficient to obtain a comparison signal Sc having a comparison pulse number Ph that is twice the number of ignitions.

The discrimination means 27 is composed of a comparison pulse shaping circuit 32, a high voltage pulse detection circuit 33, a comparator 34, a monostable multi-bi break 35, and an AND gate 36. The comparison signal SC is input to the comparison pulse shaping circuit 32, and the comparison pulse shaping circuit 32 is connected to the waveform shaping circuit 37 and F.
/V converter 38. The waveform shaping circuit 37 is, for example, a C-MOS.
The comparison signal SC, which is in the analog domain and has a lot of waveform distortion, is shaped into a logic level in the digital domain with a steep transition, and is output to the F/V converter 38. F/V converter 38
performs F/V conversion on the output from the waveform shaping circuit 37 and outputs it as an analog voltage V. The voltage V1 is an analog value corresponding to the number of comparison pulses ph, which is four per revolution of the crankshaft, and has a magnitude corresponding to the number of comparison pulses ph, which is two per one ignition number (1/2 revolution of the crankshaft). . On the other hand, the high voltage pulse Pi attenuated by the attenuator 26 is input to the high voltage pulse detection circuit 33, and the high voltage pulse detection circuit 33 is constituted by a waveform shaping circuit 39, an inverter 4o, and an F/V converter 41. Waveform shaping circuit 3
9, the high voltage pulse Pt is attenuated by an attenuator 26 and inputted, and the output Pia of the attenuator 26
(hereinafter referred to as attenuator output) is the high voltage pulse Pi
Although the peak value is small (attenuated) compared to , the waveform is similar to a high-voltage pulse. The waveform shaping circuit 39 shapes the waveform of the attenuator output Pia, and compares its negative peak value with a predetermined reference value vp (Vp<O) (see FIG. (However, in absolute value, when 1Pia l>IVpl) (I-), and when Pia≧Vp (in absolute value, IP
When ia1≦1Vpl), the signal sb which becomes (H) is inverted via the inverter 40 and output to the F/V converter 41. The F/V converter 41 performs F/V conversion on the output from the inverter 40 and outputs it as an analog voltage V2. Voltage V
As will be described later, when the spark plug is normal, 2 corresponds to the magnitude obtained by converting the signal sb, which has at least two pulses per one ignition, into F/V.

These voltages V, , V2 are input to a comparator 34, and the comparator 34 becomes (H) when V, >V2;
2, a signal Sa that becomes (L) is output. When the signal Sa is (H), it indicates that the insulation resistance of the spark plug 25 has decreased and the discharge voltage is abnormal, and when it is (L), it indicates that it is normal. The signal Sa is input to the AND gate 36, and the output 3i2 from the monostable multi-by-break 35 is further input to the AND gate 36. The monostable multi-bi break 35 outputs a rectangular ignition possible timing signal Si2 having a predetermined pulse width τ in synchronization with the rising edge of the ignition timing signal Si, and the pulse width τ is a value within the range shown by the following formula (■). is set to

(T, +'p2)X2≦τ≦T,...--1-■However,
T1: Primary current energization period of the ignition coil 23 T2: Discharge period of the high-pressure pulse Pi T3: Period during which the distributor 24 can distribute power, that is, the pulse width τ is such that the high-pressure pulse Pi can be supplied to the corresponding cylinder during one combustion cycle This corresponds to the ignition period (hereinafter referred to as ignition possible period). The AND gate 36 sends the re-discharge signal Sr to the monostable multi-by-break 22 when it is determined that the insulation resistance of the spark plug 25 is abnormal when the signals 3a and Si2 are both [I], that is, during the ignition possible period. Output.

Next, the effect will be explained.

In addition, in a spark ignition type engine, it is necessary to consider the ignition conditions for the air-fuel mixture that is ignited by spark discharge, and the discharge conditions for the spark plug that causes spark discharge. Ignition conditions vary depending on operating conditions, and spark plugs are not always required to have a uniform discharge capacity.

For this reason, the ignition conditions are estimated from the operating conditions and the discharge capacity is appropriately changed accordingly to achieve both the contradictory demands of improving the ignition capacity and reducing the amount of electrode consumption. In this case, it is assumed that the ignition energy given to the ignition plug and the discharge energy generated at the discharge electrode of the ignition plug are accurately correlated, and conventionally, the effects of such control have been expected based on this premise. are doing.

However, spark plugs are subject to a phenomenon called carbon contamination, which can be called fate, and when carbon contamination occurs, ignition energy and discharge energy no longer correlate accurately. That is, even if a predetermined ignition energy is applied, the expected discharge energy is not generated due to a decrease in insulation resistance due to carbon contamination, and the above premise cannot be established. Conventionally, this carbon contamination has been judged as smoldering contamination based on a single operating condition such as the time of startup, and furthermore, this judgment is only an indirect estimation method based on the frequency of occurrence. Therefore, carbon contamination cannot be detected accurately, and ignition control is performed while accepting the possibility that the above-mentioned premise may not be met, so that its effects are not necessarily fully exhibited.

Therefore, in this embodiment, we monitor the secondary voltage waveform of the ignition coil by focusing on the causal relationship that when carbon contamination occurs, much of the discharge energy leaks through parts with low insulation resistance and the waveform of the high voltage pulse changes. This allows carbon contamination to be accurately detected, and when such contamination is detected, the ignition energy is changed to improve the ignition ability.

This will be explained below by dividing it into normal and abnormal insulation resistance conditions, with reference to the timing chart shown in FIG.

(I) Normally, when no carbon contamination occurs, the spark plug 25
The insulation resistance of is extremely high and has an almost infinite value. Now, as shown in FIG. 3 (al), when the ignition timing signal Si is input to the monostable multi-by-break 22 at timing t,
The monostable multi-bi break 22 outputs the ignition primary signal S1 shown in FIG. 2 of the ignition coil 23 as shown in Figure 3 (el).
A predetermined high voltage is generated on the next side. Then, timing t
When the primary ignition signal Si falls at , the primary current of the ignition coil 23 is abruptly cut off and a high voltage (high voltage pulse Pi) in the opposite direction is generated on the secondary side of the ignition coil 23, as shown in FIG.
), the secondary current begins to flow. At this time, this high voltage pulse Pi is monitored by the discrimination means 27 as the attenuator output Pia, and its waveform is shown in FIG.
It changes as shown in l. That is, the high voltage pulse waveform is generated at timing t because the insulation resistance of the spark plug 25 is high.
After rapidly breaking down at timing t3 and exhibiting a peak value greater than or equal to the predetermined reference value Vp, the discharge sustaining voltage corresponding to the pressure and gas flow within the combustion chamber is maintained, and a peak value greater than Vp is exhibited again at timing t3. Further, when the gas flow is strong, a peak value of Vp or more is shown even during discharge.

In this way, under normal conditions, the high-voltage pulse waveform has at least two or more peak pulses. For this reason,
The output signal sb of the waveform shaping circuit 39 is as shown in FIG. 3+11, which is inverted via the inverter 40 as shown in FIG. taken out.

On the other hand, at this time, a comparison signal Sc having a comparison pulse number ph of two per number of ignitions is inputted from the comparison signal generation means 28 to the discrimination means 27, and this is taken out as a voltage (2). Therefore, at this time, V2>V, and the signal sa becomes (L), so the re-discharge signal Sr is not output. However, at this time, the spark plug 25
Since there is no carbon contamination, the air-fuel mixture is reliably ignited.

(TI) When carbon contamination occurs during an abnormality, the value of the insulation resistance of the spark plug 25 decreases. Therefore, even if the primary current of the ignition coil 23 is cut off at time 7'l't2, a high voltage pulse passes through the carbon attached to the insulator surface before reaching the breakdown voltage of the discharge gap of the spark plug 25. Pi leaks. Therefore, the high voltage pulse waveform is several hundred V at timing t2, as shown in Fig. 3 fh).
It only shows a low peak value and does not reach Vp.

Further, at timing t3, no peak occurs at the end of discharge, and this has been confirmed through experiments. Zunawachi,
In the event of an abnormality, the peak pulse number during one ignition timing becomes zero. Note that sometimes a peak pulse exceeding Vp appears only at the beginning of discharge, but in any case, the number of peak pulses is within the range of 1.

Therefore, the output signal sb of the waveform shaping circuit 39 is
11, this is inverted as shown in FIG. H), the re-discharge signal Sr is output.In other words, by monitoring the waveform of the high-voltage pulse PL, it is possible to accurately detect the occurrence of carbon contamination.In this case, during the ignition possible period, The high-voltage pulse Pi is supplied to the spark plug 25 again, increasing the discharge energy during the same ignition timing.As a result, deposits (carbon, etc.) attached to the insulator surface are burnt out and re-distributed between the discharge gap. A discharge spark is generated and the air-fuel mixture is reliably ignited.In other words, the ignition performance can be improved regardless of the occurrence of carbon fouling.Also, by re-discharging, the progress of carbon fouling can be prevented or carbon fouling can be eliminated. The normal discharge function can be restored. By changing the ignition energy as necessary in this way, the ignition ability can be increased while reducing the amount of electrode consumption.

FIG. 4 is a diagram showing a second embodiment of the present invention, in which the discharge voltage during re-discharge is increased.

In FIG. 4, reference numeral 51 denotes high-voltage pulse generating means, and the high-voltage pulse generating means 51 is constructed by adding a monostable multivib break 52 and a transistor Q2 compared to the first embodiment. When the monostable multi-bi break 52 receives the re-discharge signal Sr, it generates a second ignition primary signal S12 having a pulse width longer than the pulse width of the ignition primary signal S output from the monostable multi-bi break 22. Output to transistor Q2. The rest is the same as the first embodiment, and the same numbers are assigned.

Therefore, in this embodiment, the high-voltage pulse Pi having a longer primary current conduction time in the ignition coil 23 is supplied to the ignition plug 25 again in the event of an abnormality (IT) than in the first embodiment. As a result, the discharge voltage becomes higher and the effect against carbon contamination can be enhanced more than in the first embodiment.

In each of the above embodiments, the term carbon contamination is used as an abnormality, but this term is not limited to carbon, but also refers to unnecessary deposits that reduce the insulation resistance of the insulator, such as lead contamination or fuel fogging. Of course, it can be considered broadly.

(Effects) According to the present invention, when carbon fouling occurs, the discharge energy during the same ignition timing can be increased,
Despite carbon contamination, it is possible to improve ignition performance, reduce electrode consumption, and improve engine drivability.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2.3 is a diagram showing the first embodiment of the invention, Fig. 2 is a circuit configuration diagram thereof, and Fig. 3 (al to (Jl is the effect) FIG. 4 is a circuit configuration diagram showing a second embodiment of the present invention, and FIG. 5 is a schematic configuration diagram of a conventional ignition system for an internal combustion engine. 21.51. -1 high voltage pulse generating means, 25---
---Spark plug, 27---Discrimination means, 28--Comparison signal generation means.

Claims (1)

[Scope of Claims] A spark plug that discharges a high-pressure pulse to ignite an air-fuel mixture, a comparison signal generating means that outputs a comparison signal having a comparison pulse number that is a predetermined number of times the number of ignitions, and a comparison signal generator that is supplied to the spark plug. A determining means for detecting the waveform of the high-voltage pulse and determining the number of peak pulses whose peak value is equal to or higher than a predetermined reference value, and outputting a re-discharge signal when the peak pulse number is less than the comparison pulse number; An ignition device for an internal combustion engine, comprising: high-pressure pulse generating means that generates the high-pressure pulse at each timing and generates the high-pressure pulse again during the ignition timing when a re-discharge signal is input.