JPH04203271A - Method and apparatus for sensing fire loss in engine with ion current system - Google Patents

Abstract

PURPOSE:To improve a fire loss sensing performance with an ion current system by a method wherein an operation for sensing ion current is carried out for every time band when a normal combustion is assumed and an ion current is expected as a normal current flow and a judgement of the fire loss in the engine is carried out if any of these detected values is less than a reference value. CONSTITUTION:A control device 1 generates an ignition time signal 11 in response to each of outputs of a crank angle sensor 2, an air flow rate sensor 3, a throttle sensor 4, a power supply voltage sensor 5 and a water temperature sensor 6. In turn, each of ion current sensing circuits 10 is disposed between a spark plug 12 of each of cylinders and a low voltage side of a secondary coil, respectively, and the ion current sensing circuit 10 is comprised of a capacitor 13, a resistor 14 and a diode 15 or the like. In this case, a normal combustion is assumed and an ion current sensing operation is carried out at plural times in a time range for every expected time band where the ion current is normally flowed. If the detected values at plural times are less than their set values, it is judged that the engine has a fire loss in it.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention detects an ion current that reflects the combustion state of an engine and detects engine misfires (here, misfires include a type of intermittent misfires such as smoldering). (including).

[Conventional technology]

During combustion in an engine, gas within the cylinder is ionized due to thermal dissociation caused by combustion. When the pressure of this ionized gas is increased by the piston, the ion density increases. If an electric field is applied between the plug electrodes (plug gap) of an engine in this ionized atmosphere, a current (-
・This is generally called an ionic current) flows.

A method for detecting engine misfire based on the presence or absence of ion current is known. For example, U.S. Pat.
．． No. 8, No. 367 attempts to prevent over-pressure ignition of an engine by using ionic current.

Furthermore, recently, from the viewpoint of preventing air pollution, a technique has been proposed for detecting engine misfire based on the presence or absence of ion current.

[Problem to be solved by the invention]

By the way, in the case of an engine misfire caused by the conventional ion current method, sufficient consideration has not been given to the following points.

(b) Ion current is detected when the engine burns normally, but since the ionization atmosphere is not -.
For example, in Figure 7, there may be large vertical fluctuations. At this time, the value may be lower than the set level P (point ■' in FIG. 7), and if this coincides with the sampling time of the detected value, it will be erroneously determined that there is a misfire.

(b) Another aspect of engine misfire is smoldering due to fouling of the spark plug over time. In this case, the insulation between the plug electrodes deteriorates and leakage current occurs, raising the detection reference level, for example, the GND (ground) level. This GND fluctuation level is taken as the ion current value, and the engine operates normally. In some cases, it was mistakenly determined to be combustion.

The present invention solves the above problems and improves the performance of engine misfire detection using the ion current method.

[Means to solve the problem]

The present invention basically proposes the following problem-solving means.

In order to solve the problem (a), the first means of solving the problem is to detect a misfire using this type of ion current method. The ion current detection operation is performed at multiple points in the time period (for example, at different crank angle positions) for each time period (usually replaced by the crank angle because it changes depending on the engine rotation speed). However, if any of the detected values at multiple points in time is less than the reference value, it is determined that the engine has misfired.

The second problem-solving means and the third problem-solving means are mainly for solving the problem (b) above.

In other words, as a second means of solving the problem, in the misfire detection method using the ion current method, first, ion current detection is performed within each time period in which the ion current is expected to normally flow in the case of normal combustion. In addition to determining whether or not there is an engine misfire based on the detected value, the ion current detection operation is also performed even when the above-mentioned time period is outside, and if the detected value during this outside time period is above the reference level. Ba,
Engine misfire (smoldering misfire) is determined with priority over determination based on the detected value in the time period.

Further, the third problem-solving means is to perform an ion current detection operation within each time period in which the ion current is expected to normally flow assuming normal combustion, and further to remove the above-mentioned time period. ion current detection operation is performed, and the difference between detected values inside and outside these time periods is compared with a set value to determine whether or not an engine misfire has occurred.

Please note that the above 2. In the third problem solving method,
Assuming normal combustion, the ion detection operation is performed during a time period when the ion current is expected to normally flow, and as in the first problem solving method, the ion detection operation is performed at multiple points in the time period, and these detected values are It may also be used as misfire determination data.

In addition, we propose the following J: as a device used in the misfire detection method in the first problem solving means.

That is, it has a means of applying an electric field to the gas ionized by combustion in the engine using the electrode of the spark plug,
In a device that determines the presence or absence of an engine misfire based on the detected value of the current (ion current) flowing between the spark plug gaps when this electric field is applied, multiple different predetermined crank angles are used as the determination data for each engine misfire. (The crank angle here is set within the crank angle range that corresponds to the time period in which the ion current is expected to normally flow, assuming normal engine combustion.) and means for determining that the engine has misfired when all of the detected ion current values taken at the plurality of different crank angles are equal to or less than a set value.

Further, as a device used in the misfire detection method of the second problem solving means, in an ion current type engine misfire detection device, a plurality of different predetermined crank angles (here crank At least one of the angles is set within a crank angle range that corresponds to a period of time during which ion current is expected to normally flow assuming normal combustion in the engine, and the other is set within a crank angle range that corresponds to the time period during which the ion current is expected to normally flow. A means for capturing the detected ion current value at that point in time (set from among the above), and a means for capturing the detected ion current value at a crank angle outside the above-mentioned time period is equal to or higher than the reference level (including the ground level). , a means for preferentially determining engine misfire (smoldering misfire), and an ionic current taken in at a crank angle within the above time period on the premise that a misfire has not been determined by the preferential determination. and means for comparing the detected value with a set value to determine whether or not there is an engine misfire.

The device used in the misfire detection method in the third problem solving means is an ion current type engine misfire detection method that uses a plurality of different predetermined crank angles (here crank angle At least one of these is set within a crank angle range that corresponds to a time period in which ion current is expected to normally flow assuming normal combustion in the engine, and the other is set within a crank angle range that corresponds to a time period in which ion current is expected to normally flow, assuming normal combustion in the engine, and the other is set within a crank angle range that corresponds to a time period in which ion current is expected to normally flow assuming normal engine combustion. The difference between the ion current detection value taken at the crank angle inside and outside the above time period is compared with the set value to determine whether or not there is an engine misfire. and means for determining.

[Effect]

Effect of the first problem-solving means: If the ion current detection operation is performed at multiple points in time (for example, at multiple different crank positions) within the ion current time period that is predicted to normally flow assuming normal combustion, One of these is the probability of accurately detecting the state of the sea urchin ion current: J, which is indicated by the virtual line (dashed line) in Figure 7, even if the detected value is detected at a point like ■' in Figure 7. becomes extremely high.

Therefore, if an ion current is flowing, it will not be overlooked, making it possible to determine whether or not an engine misfire has occurred based on accurate current detection.

In this case, if any one of the plurality of detected ion current values used for determining each misfire is equal to or higher than the set value 11, normal combustion is determined.

Conversely, if any of the detected ion current values is less than the set value, it is determined that the engine has misfired.

Second problem-solving means: This problem-solving means also basically determines whether or not an engine misfire has occurred based on the detected value of the ion current during a time period when normal combustion is expected to occur. However, the ion detection operation is performed even at a time point outside of the normal ion current time period (for example, after a delay).

In other words, as pointed out in the problem (b) above,
If the spark plug smolders, the leakage current will cause the level of the detected value to drop. If this is taken as an ion current detection value even outside the above time period, and the ion current detection value is taken at a time when it should not actually occur, we will know that the engine is misfiring (smoldering) and can judge this as a misfire. By prioritizing this, it is possible to prevent misjudgments of engine misfires.

Third problem-solving means/This problem-solving means executes the ion current detection operation during a time period in which the ion current is expected to normally flow assuming normal combustion, and then performs the ion current detection operation outside the above time period. A current detection operation is performed, and the difference between detected values inside and outside these time periods is compared with a set value.

In the case of normal combustion, the difference between the detected values inside and outside this time period is sufficiently large and can exceed the set value.

Furthermore, in the case of an engine misfire without smoldering, there is almost no difference between the detected values within and outside the time period, and the detected values are below the set value.

Furthermore, when smoldering occurs, the level of the detected value outside the above time period remains constant, and on the other hand, the level of the detected ion current value within the time period has also reached a certain level. The difference between the values is reduced and the difference becomes the set value common code.

If these set values are equal to or less than -1, it is possible to accurately determine the presence or absence of engine misfire, regardless of whether the engine is smoldering or not.

In other words, in the third problem solving means, the detected ion current value outside the time period serves as a correction value when calculating the difference between the detected ion current value within the time period.

In addition, 1. Second. The operation of the device used in the third problem-solving means has been described in detail in the Examples section, so the explanation here will be omitted.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of a device related to the misfire detection technology of the present invention. An example of application to an L-plug/I-coil type electronic ignition control system having one ignition coil per spark plug corresponding to each cylinder is illustrated.

In FIG. 1, reference numeral 1 includes a control unit coater having a built-in program for controlling ignition timing and detecting misfire according to the present invention.

In other words, the control unit includes ROM that stores fixed data necessary for ignition timing control, misfire determination, etc., RAM that can read and write data, and a central processing unit that performs digital calculation processing of various data. 1 to (CPU), etc.

In actual ignition timing control, in addition to the crank angle sensor output 2, the engine The optimum ignition timing suitable for the situation is calculated and the ignition timing signal (including the ignition energization time) is "'TGN".

11 is generated.

The ignition timing signal 11 is amplified by a signal amplifier 7 and supplied to the base of a power transistor 8 for controlling an ignition coil. That is, the primary coil current is caused to flow for the time determined by the calculation, and then the power transistor 8 is turned off, and a high voltage corresponding to the cut-off current is applied to the ignition coil 9.
The spark is generated in the secondary coil of the spark plug 12 and generates a spark for ignition in the spark plug 12.

An ion current detection circuit 1 is connected between the spark plug 12 of each cylinder and the low voltage side [ground GNI)] of the secondary coil.
0 is the default.

The ion current detection circuit 10 includes a capacitor]3° resistor 14
．． It is composed of a diode 15 and the like.

The mechanism of ion current detection is as follows.

While the spark plug] 2 is sparking, current flows in the direction of arrow a, and capacitor B in detection circuit 10 is charged. By the way, as already mentioned in the section of the prior art, after combustion in the engine, the gas in the cylinder is dissociated and ionized by the heat.

Because of this ionized atmosphere, if the charged voltage of the capacitor 14 becomes a power source after sparking and an electric field is applied to the gap of the spark plug 12, an ionic current will flow. This ion current is detected via a resistor 15.

To explain this with reference to FIG. 2, the crank angle sensor output 1 shown in FIG. 2 (a) is a cylinder discrimination pulse. Based on this pulse, the crank angle sensor output shown in Figure (b) is counted up until the preset ignition timing (crank angle) is reached, and when the set timing is reached, the primary Cut the current, it's worth it 1
The next voltage ■ is generated to spark the ignition plug 12.

The capacitor B of the detection circuit 10 is charged while a spark is generated, that is, between (1) and (2). After the engine explodes and combustion begins, and the spark ends, an ion current is generated as shown by the broken line arrow in Figure 1 (the area shown by the arrow in Figure 2 (d) shows the ion current generated during normal combustion. (This is the time when current normally flows.)

The ionic current detection data is used to perform analytical calculation processing regarding control unit misfire.

=19- As a calculation processing function regarding engine misfire of the roll unit 1 to the controller 1, the following aspects can be considered.

In the first aspect, the engine misfire calculation mechanism is
J: not shown in (d) of the figure J: Taking the time period t in which the ion current is expected to normally flow under normal combustion conditions from the crank angle, different crank angles 0α, Oα within the crank angle range a sampling means for taking in the ion current detection data (outputs A, B) at the position Oα,
Each ion current detection value (voltage value) at 0α′
and a set voltage P to determine whether or not an engine misfire has occurred.

Flowchart 1 to engine misfire determination processing in this case is shown in FIG. That is, in FIG. 3, in the process from steps S1 to 84, the detected ion current values at rank angles θα and Oα′ as shown in FIG. , the detected value A in step S6.

Compare each of B with the set value P, and find that A and B are small = 20
- If at least one is greater than or equal to P, it is determined that combustion is normal (S
7). If both A and B are below P, it is determined that a misfire has occurred.

In this manner, it is possible to eliminate the conventional situation where the ion current detection value is missed during the time period when the ion current normally flows, and ensure reliable ion current detection, resulting in an engine misfire. improve detection performance.

As a second aspect, as shown in FIG. 2, as the judgment data for each engine misfire, at least one is selected from the normally predicted ion current time period t at a crank angle of 0.
The ion current detection value is taken in at a time corresponding to α or θα′, and the other is provided with a means to take in the ion current detection value at the time of crank angle 0α, which is outside the time period t. The ion current detection value C taken in is the reference level (including ground level)
In the above case, a crank angle of 0α(
The difference between the ion current detection value A (B) taken in at 0α') and the output C taken outside the time period is compared with a set value P to determine whether or not there is an engine misfire.

The engine misfire determination process in this case is executed according to flowchart 1 in FIG. That is, in FIG. 4, in the process from steps S1 to 84, the detected ion current values at crank angles Oα and Oβ are A/D converted and taken in.

First, the detected ion current value C at 0β is set to the reference value (
Here, compared to the ground level), if the output C is at the reference value -1-, the ion current is detected at a position that is normally impossible, and this is determined to be caused by a misfire due to smoldering. (S9).

In other words, smoldering misfires caused by fouling of the spark plug over time are caused by a decrease in the insulation between the electrodes of the spark plug. The leakage current is accumulated in the capacitor B, and the voltage value of the resistor 14 of the ion current detection circuit 10, which should be at ground level except during certain times, reaches the position shown by the broken line in Fig. 2(d). . The second detects the relevel from the detected value C and compares it with a reference level (for example, the original ground level), and if C>the reference value, it is determined that there is smoke (S9).

In addition, if this smoldering judgment occurs, the J of S 1.0
: When fuel injection to a smoldering cylinder is temporarily interrupted, only the air in the cylinder is sucked and compressed.

This is effective because the exhaust removes dirt and wetness from the plug and restores its integrity.

(If the smoldering judgment is NO, compare the difference between output A and output C with the set value Q, and if (A, -C)≧Q, judge normal combustion. S9), (A -C)≦Q, it is assumed that no ion current is generated during time period t, and it is determined that the engine has misfired (S7).

In this aspect, in addition to normal engine misfires, smoldering misfires are also accurately detected, and this is determined without being mistaken for a normal combustion state, so the performance of engine misfire detection is improved. Since countermeasures have also been taken, there is an advantage that the reliability of engine ignition control is also improved.

As a third aspect, the ion current detection value A (B) at a crank angle of 0α (or Oα') within the above-mentioned time period and the crank angle outside the above-mentioned time period are used as the judgment data for each engine misfire. It is composed of means for taking in the detected ion current value C at Oβ, and means for comparing the difference between the detected value A (B) and the detected value C with a set value Q to determine whether or not there is an engine misfire.

The engine misfire determination process in this case is executed according to the flowchart shown in FIG.

Flowchart 1. of FIG. 5 corresponds to step 85. of FIG.
Although 89 is omitted, even in this manner, not only normal engine misfire but also smoldering misfire can be determined. This is because when the detected current value C of Oβ rises by 2 due to smoldering, the difference between the detected current value A of 0α and the detected value C of Oβ becomes small, and the difference becomes 85, which is less than the set value Q, so it is considered as a misfire. A determination is made (S7).

Therefore, in this aspect as well, in addition to normal engine misfires, smoldering misfires can also be accurately detected and this can be determined without error as being in a normal combustion state, thereby improving engine misfire performance.

Note that the engine misfire determination element of the first aspect and the second or third engine misfire determination element may be combined as appropriate. The flowchart 1 is shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, when detecting engine misfire, it is possible to prevent the detected ion current value from being overlooked, or to prevent misjudgment of smoldering misfire as normal combustion, or to achieve both of the effects described in 4.2. This makes it possible to simultaneously achieve this, improving the performance and reliability of engine misfire detection.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a device used in the ion current type engine misfire detection method of the present invention, FIG. 2 is an explanatory diagram showing its operating state, and FIGS. 3 and 4. FIGS. 5 and 6 are flowcharts 1 and 7 respectively illustrating various aspects of engine misfire detection according to the present invention, and FIG. 7 is an explanatory diagram pointing out the problems of the conventional method. I...control unit ion current sampling means, engine misfire determination means)
, 2... Crank angle sensor, 8... Power transistor for ignition, 9... Ignition coil, 10. Ion current detection circuit, 12... Spark plug, B... Capacitor, 14
...Resistance, 15...Diode.

Claims (1)

[Claims] 1. A method for determining whether or not an engine has misfired by detecting a current (ion current) flowing across the spark plug gap when an electric field is applied to gas ionized by combustion in the engine. For each time period in which ion current is expected to normally flow assuming combustion, ion current detection is performed at multiple points in that time period, and any detected values at these multiple points are equal to the set value (ground A method for detecting an engine misfire using an ion current method, characterized in that if the engine misfire is determined to be the engine misfire if the engine misfire is below (including the level). 2. In the method of determining the presence or absence of engine misfire by detecting the current (ion current) flowing between the spark plug gap when an electric field is applied to the ionized gas due to engine combustion, ionization is detected assuming normal combustion. For each time period when the current is expected to normally flow, an ion current detection operation is performed during that time period, and based on the detected value, the presence or absence of engine misfire is determined. The ion current detection operation is executed, and if the detected value in this out-of-time period is equal to or higher than the reference level, the engine misfire (smoldering misfire) is determined in priority to the determination based on the detected value in the aforementioned time period. Characteristic engine misfire detection method. 3. In the method of determining the presence or absence of engine misfire by detecting the current (ion current) flowing between the spark plug gap when an electric field is applied to gas ionized by engine combustion, ionization is detected assuming normal combustion. For each time period in which current is expected to normally flow, an ion current detection operation is performed within that time period, and an ion current detection operation is performed outside of the above time period, and the detected values inside and outside of these time periods are A method for detecting an engine misfire using an ion current method, characterized in that the difference between the two values is compared with a set value to determine the presence or absence of an engine misfire. 4. In the method of determining the presence or absence of engine misfire by detecting the current (ion current) that flows between the spark plug gap when an electric field is applied to gas ionized by engine combustion, ionization is detected assuming normal combustion. For each time period in which current is expected to normally flow, ion current detection operations are performed at multiple times within that time period, and based on these multiple detected values, the presence or absence of engine misfire is determined. If the detected value in the off-time period is equal to or higher than the standard level, engine misfire (smoldering misfire) will be determined in priority to the determination based on the detected value in the aforementioned time period. A method for detecting engine misfire, characterized in that: 5. In the method of determining the presence or absence of engine misfire by detecting the current (ion current) that flows between the spark plug gap when an electric field is applied to gas ionized by engine combustion, ionization is detected assuming normal combustion. For each time period in which current is expected to normally flow, ion current detection operations were performed at multiple times within that time period (the detected values at this time were designated as A and B), and the above time periods were further removed. Execute the ion current detection operation at this point (the detected value at this time is C), find the difference between each of the detected values A and B and the detected value C, and compare the difference with the set value Q. An engine misfire detection method using an ion current method, characterized in that the presence or absence of an engine misfire is determined by using the ion current method. 6. In any one of claims 1 to 5, the predicted ion current time period is taken as a crank angle range of the engine, and execution is performed within and outside the time period. An engine misfire detection method using an ion current method, characterized in that the ion current detection operation timing is determined by replacing it with a predetermined crank angle. 7. It has a means of applying an electric field to the gas ionized by engine combustion using the electrode of the spark plug, and based on the detected value of the current (ion current) flowing between the spark plug gap when this electric field is applied. In a device that determines the presence or absence of an engine misfire, the engine misfire determination data for each engine misfire is determined using multiple different predetermined crank angles (here, the crank angle is assumed to be a normal flow of ion current, assuming normal combustion in the engine). A means for capturing the detected ion current value at that point in time (set from a crank angle range corresponding to the time period), and a means for capturing the detected ion current value at the plurality of different crank angles. What is claimed is: 1. An ion current type engine misfire detection device comprising means for determining that an engine misfire has occurred when the value is below a set value. 8. It has a means of applying an electric field to the gas ionized by engine combustion using the electrode of the spark plug, and based on the detected value of the current (ion current) flowing between the spark plug gap when this electric field is applied. In a device that determines the presence or absence of an engine misfire, the engine misfire determination data for each engine misfire is set at a plurality of different predetermined crank angles (at least one of the crank angles is determined based on the ionic current assuming normal combustion of the engine). One is set from within the crank angle range that corresponds to the time period in which the flow is expected to normally occur, and the other is set from within the crank angle range outside of the above time period) to capture the detected ion current value at that time. means for preferentially determining engine misfire (smoldering misfire) when a detected ion current value acquired at a crank angle outside the time period is equal to or higher than a reference level (including ground level); means for determining the presence or absence of an engine misfire by comparing a detected ion current value taken at a crank angle within the time period with a set value, on the premise that a misfire has not been determined by a manual determination. An ion current type engine misfire detection device characterized by comprising: 9. It has a means of applying an electric field to the gas ionized by combustion in the engine using the electrode of the spark plug, and based on the detected value of the current (ion current) flowing between the spark plug gap when this electric field is applied. In a device that determines engine misfire, the engine misfire determination data for each engine misfire is set at a plurality of different predetermined crank angles (at least one of the crank angles here assumes that the ion current is high, assuming normal combustion of the engine). One is set within a crank angle range that corresponds to a time period where normal flow is expected to occur, and the other is set within a crank angle range that is outside the above time period). and means for comparing the difference between detected ion current values taken at crank angles within and outside the time period with a set value to determine whether or not there is an engine misfire. Detection device. 10. In any one of claims 7 to 9, when it is determined that there is an engine misfire,
An ion current type engine misfire detection device comprising means for generating a command signal to temporarily interrupt fuel injection to a cylinder to be determined.