JP2942351B2 - Engine misfire detection method and apparatus by ion current method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention detects an ionic current that reflects the combustion state of an engine and misfires the engine (here, misfire and a kind of intermittent fire such as smoldering). And methods for detecting the same.

[Conventional technology]

During combustion of the engine, the gas in the cylinder is ionized by a thermal dissociation phenomenon caused by the combustion. When the pressure of the ionized gas is increased by the piston, the ion density increases. When an electric field is applied between the plug electrodes (plug gap) of the engine in the ionized atmosphere, a current (generally referred to as an ion current) flows.

A system for detecting engine misfire from the presence or absence of the ion current is known. For example, in U.S. Pat. No. 4,643,867, premature ignition of the engine is prevented by the ionic current.

Recently, a technique for detecting an engine misfire from the presence or absence of an ion current from the viewpoint of preventing air pollution has been proposed.

[Problem to solve the invention]

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

(A) Although the ion current is detected when the engine is normally burned, the ion current may fluctuate greatly up and down as shown in FIG. 7, for example, because the ionization atmosphere is not uniform. At this time, the level may be lower than the set level P (point 'in FIG. 7), and if this coincides with the sampling point of the detected value, it is erroneously determined that there is a misfire.

(B) Further, as an aspect of engine misfire, there is smoldering due to spark plug contamination that changes with time. In this case, the insulation between the plug electrodes is reduced, causing a leakage current, and the detection reference level, for example, the GND (ground) level rises. The GND fluctuation level is taken as the ion current value, and the engine operates normally. In some cases, it was erroneously determined to be combustion.

An object of the present invention is to solve the above problem and improve the performance of engine misfire detection using an ion flow method.

[Means for solving the problem]

The present invention basically proposes the following problem solving means.

The first means for solving the problem is to solve the above-mentioned problem (a) by detecting a misfiring by this type of ion current method in a time zone in which ion current is expected to flow normally assuming normal combustion (this time period). The time zone changes depending on the engine speed, so it is usually replaced by the crank angle.) Each time, the ion current detection operation is performed at multiple points in the time zone (for example, at different crank angle positions). If any of the detected values at the plurality of times is equal to or less than the reference value, the engine misfire is determined.

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

That is, as a second problem solving means, in the method of detecting misfire by the ionic current method, first, for each time zone in which the ionic current is expected to flow normally in normal combustion, the ionic current detection is performed in that time zone. Perform the operation, and determine the presence or absence of engine misfire based on the detected value, and perform the ion current detection operation even at the time outside the time zone,
If the detected value in the deviated time zone is equal to or higher than the reference level, the engine misfire (smoldering misfire) is determined prior to the determination based on the detected value in the time zone.

Further, the third problem solving means executes an ion current detection operation in each time zone in which the ion current is expected to flow normally, assuming normal combustion, and further removes the time zone. The detection operation of the ion current is performed, and the difference between the detected values inside and outside these time zones is compared with a set value to determine the presence or absence of engine misfire.

In the second and third means for solving the above problems, the ion detection operation performed in the time zone in which the ion current is expected to flow normally assuming normal combustion is performed in the same manner as the first means for solving the problems. The detection may be performed at a plurality of points in the time zone, and these detected values may be used as misfire determination data.

Further, the following is proposed as an apparatus used for the misfire detection method in the first problem solving means.

That is, there is provided a means for applying an electric field to the gas ionized by the combustion of the engine using an electrode of a spark plug, and based on a detection value of a current (ion current) flowing between the spark plug gaps after the electric field is applied. In the apparatus for determining the presence or absence of engine ignition, a plurality of different predetermined crank angles (here, the crank angles are assumed to be normal when the ionic current flows assuming normal combustion of the engine) as the engine misfire determination data every time. Means for capturing an ion current detection value at that time in a crank angle range corresponding to a predicted time zone), and any of the ion current detection values captured at the plurality of different crank angles. Means for determining that an engine misfire has occurred when is less than or equal to a set value.

Further, as an apparatus used in the misfire detection method according to the second problem solving means, an ion current type engine misfire detection apparatus includes a plurality of different predetermined crank angles (crank here) as judgment data of engine misfire each time. At least one of the angles is set from a crank angle range corresponding to a time period in which the ion current is expected to flow normally assuming normal combustion of the engine.) Means for taking in, and means for preferentially judging engine misfire (smoldering misfire) when the detected ion current value taken at a crank angle outside the time zone is equal to or higher than a reference level (including a ground level), Assuming that a misfire has not been determined by the priority determination, an ion current detected at a crank angle within the time period is detected. The compared with set values comprising a means for determining the presence or absence of engine misfires.

According to a third aspect of the present invention, there is provided an apparatus for detecting a misfire of an ion fuel flow system, wherein a plurality of different predetermined crank angles (crank here) are used as determination data of engine misfire. At least one of the angles is set from a crank angle range corresponding to a time zone in which the ion current is expected to flow normally, assuming normal combustion of the engine, and the other is a crank angle outside the time zone. Means for capturing the ion current detection value at that point in time, and comparing the difference between the ion current detection values captured at crank angles inside and outside the time zone with a set value to determine whether engine misfire has occurred. Determining means.

[Action]

Operation of the first problem-solving means: In the ion current time zone predicted to flow normally assuming normal combustion, if the ion current detection operation at a plurality of time points (for example, different crank positions) is performed, Even if one captures the detected value at a point like 'in FIG. 7, the other is extremely likely to accurately detect the state of the ion current as shown by the phantom line (dashed line) in FIG. .

Therefore, when an ion current is flowing, it is not overlooked, so that it is possible to determine the presence or absence of engine misfire by accurate current detection. In this case,
If any one of the plurality of ion current detection values used for one misfire determination is equal to or greater than the set value P, normal combustion is determined.

Conversely, if any of the ion current detection values falls below the set value,
The engine misfire will be determined.

Second Problem-Solving Means: In this problem-solving means also, basically, the presence or absence of engine misfire is determined based on an ion current detection value in a time zone in which normal flow is predicted assuming normal combustion. However, the ion detection operation is also performed at a point outside (for example, after a delay) of the normal ion current time zone.

In other words, as pointed out in the problem (b) described above, when smoldering occurs in the ignition plug, the level of the detected value increases due to the leakage current. If this is apparently taken as an ion current detection value even outside the above-mentioned time zone, it is determined that there is an ion current detection value at a time when it should not actually occur. By doing so, erroneous determination of engine misfire can be prevented.

Third problem-solving means ... In this problem-solving device, the ion current is detected in the time zone in which the ion current is expected to flow normally, assuming normal combustion. The current detection operation is performed, and the difference between the detected values inside and outside these time zones is compared with a set value.

The difference between the detected values inside and outside this time zone is
The difference can be large enough to exceed the set value.

Further, in the case of engine misfire without smoldering, there is almost no difference between the detection values inside and outside the time zone, and the difference is equal to or less than the set value.

Furthermore, when smoldering has occurred, the level of the detected value outside the above-mentioned time zone rises, while the level of the ion current detection value within the above-mentioned time zone has also reached a certain level. The difference is smaller than the set value.

If the following conditions are detected, the presence or absence of engine misfire can be accurately determined regardless of smoldering.

In other words, the third problem solving means serves as a correction value when the difference between the ion current detection value outside the time zone and the ion current detection value within the time zone is determined.

The operation of the apparatus used for the first, second, and third problem solving means is described in detail in the section of the embodiment, and the description is omitted here.

〔Example〕

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

FIG. 1 is a configuration diagram showing an apparatus according to an embodiment relating to a misfire detection technique of the present invention. An example is shown in which the present invention is applied to a one-plug / one-coil type electronic ignition control system having one ignition coil per ignition plug corresponding to each cylinder.

In FIG. 1, reference numeral 1 denotes a control unit (C / U) having a built-in program for performing ignition timing control and misfire detection according to the present invention, which is constituted by a microcomputer.

That is, the control unit 1 has
It has a ROM for storing fixed data necessary for ignition timing control, misfire determination, etc., a RAM for reading and writing data, and a central processing unit (CPU) for digitally processing various data.

In actual ignition timing control, in addition to the crank angle sensor output 2, the output Q _A of the air flow sensor 3, the output θ _H of the throttle sensor 4, the output V _B of the power supply voltage sensor 5, the water temperature sensor 6
Based on the output T _W of the engine, the optimum ignition timing suitable for the engine condition is calculated and the ignition timing signal (including the ignition energizing time)
“IGN” 11 is generated.

The ignition timing signal 11 is amplified by the signal amplifier 7 and supplied to the base of the power transistor 8 for controlling the ignition coil. That is, the primary coil current flows for the time determined by the calculation, and thereafter, the power transistor 8 is turned off, and the high voltage corresponding to the cutoff current is applied to the ignition coil 9.
To generate spark for ignition in the spark plug 12.

An ion current detection circuit 10 is provided between the ignition plug 12 of each cylinder and the low voltage side (ground GND) of the secondary coil.
Are provided respectively.

The ion current detection circuit 10 includes a capacitor 13, a resistor 14, a diode 15, and the like.

 The mechanism of ion current detection is as follows.

While the spark plug 12 is sparking, current flows in the direction of arrow a, and the capacitor 13 in the detection circuit 10 is charged. By the way, as already described in the related art section, the gas in the cylinder is dissociated and ionized by the heat after the combustion of the engine.

Due to the ionized atmosphere, an ion current flows when the charging voltage of the capacitor 14 serves as a power source and applies an electric field to the gap of the ignition plug 12 after sparking. This ion current is detected via the resistor 15.

This will be described with reference to FIG. 2. The output 1 of the crank angle sensor shown in FIG. 2A is a cylinder discrimination pulse until the ignition timing (crank angle) set in advance based on this pulse is reached. Counting up using the crank angle sensor output (constant angle repetition pulse) of (b), when the set time comes, the primary current is cut, a primary voltage corresponding to this is generated, and the ignition plug 12 Spark.

The capacitor 13 of the detection circuit 10 is charged while the spark is occurring, that is,. After the engine starts explosion and combustion and the spark ends, an ionic current is generated as shown by a broken arrow in FIG. 1 (a portion indicated by t in FIG. It is a time zone that is assumed to flow normally).

The ion current detection data is taken into the control unit 1, and an analysis calculation process regarding engine misfire is executed based on the detection data.

As an arithmetic processing function relating to engine misfire of the control unit 1, the following one can be considered.

As a first embodiment, the engine misfire calculation mechanism is configured to capture a time period t in which ion current is expected to flow normally in a normal combustion state from cranking as shown in FIG. 2D. Sampling means for fetching ion current detection data (outputs A and B) at different crank angles θα and θα 'within the range of the crank angles;
means for comparing each ion current detection value (voltage value) at α 'with the set voltage P to determine whether engine misfire has occurred.

FIG. 3 shows a flowchart of the engine misfire determination process in this case. That is, in FIG.
In the process from S1 to S4, the ion current detection values at the crank angles θα and θα ′ as shown in FIG. 2 are fetched by analog / digital conversion (A / D conversion), and the detection values A, If at least one of A and B is equal to or greater than P, it is determined that the combustion is normal (S7).
If both A and B are P or less, it is determined that a misfire has occurred.

According to this aspect, in the time zone t when the ion current normally flows, a situation in which the detected value of the ion current is unlikely to be taken as in the related art is eliminated, and the reliable detection of the ion current is ensured. Improve performance.

As a second mode, as shown in FIG. 2, at least one of the engine misfire determination data corresponds to the crank angle θα or θα ′ from the normally predicted ion current time zone t as shown in FIG. At the time when the ion current detection value is taken, and the other is the crank angle θα that is outside the time zone t.
Means for taking in the ion current detection value at the point of time. Further, if the ion current detection value C taken in at the crank angle θβ outside the time period t is equal to or higher than the reference level (including the ground level), the smoldering misfire occurs preferentially. And the crank angle θα within the time zone t on the assumption that the misfire has not been determined by this priority determination.
Means for determining the presence or absence of engine misfire by comparing the difference between the ion current detection value A (B) taken in at (θα ') and the output c taken outside the time zone t with the set value P.

The engine misfire determination process in this case is executed according to the flowchart of FIG. That is, in FIG. 4, in the course of steps S1 to S4, the crank angles θα and θβ
A / D-converts and captures the ion current detection value at.

Then, first, the ion current detection value C at θβ is compared with a reference value (here, the ground level) (S5). If the output C is equal to or higher than the reference value, the ion current detection at an impossible position is impossible. It is determined that this is caused by smoldering misfire (S9).

That is, the smoldering misfire caused by the fouling of the spark plug over time is caused by a decrease in insulation between the electrodes of the spark plug. The leakage current is stored in the capacitor 13, and the voltage value of the resistor 14 of the ion current detection circuit 10 should be at the ground level except during the time period t, and rises to the position indicated by the broken line in FIG. 2 (d). This lifting level is taken as a reference level (eg, the original ground level) from the detection value C.
If C> reference value, it is determined that smoldering has occurred (S9).

When the smoldering determination is made, the fuel injection to the smoldering cylinder is temporarily interrupted as in S10, and the dirt and leakage of the plug are eliminated by suction, compression and exhaust of only the air of the cylinder, It is effective because it restores soundness to the plug.

When the smoldering determination is NO, the difference between the output A and the output C is compared with the set value Q. When (AC) ≧ Q, it is determined that the combustion is normal combustion (S9), (AC) If ≦≦ Q, it is determined that no ion current has occurred in the time zone t, and it is determined that the engine is misfired (S7).

In this embodiment, in addition to the normal engine misfire, the smoldering misfire is accurately detected, and the normal combustion state is determined without error.Therefore, the performance of the engine misfire detection is improved, and the countermeasure for the smoldering misfire is also provided. Since we are taking
There is an advantage that the reliability of engine ignition control is also improved.

As a third mode, the ion current detection value A (B) of the crank angle θα (or θα ′) within the time zone t and the crank angle outside the time zone t are used as the engine misfire determination data each time. Means for taking in the ion current detection value C at θβ, and means for comparing the difference between the detection value A (B) and the detection value C with a set value Q to determine the presence or absence of engine misfire.

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

The flowchart of FIG. 5 corresponds to steps S5 and S9 of FIG.
Is omitted, but even in this case, not only a normal engine misfire but also a smoldering misfire can be determined. Because, when the current detection value C of θβ increases due to smoldering, the difference between the current detection value A of θα and the detection value C of θβ becomes small, and the difference becomes equal to or less than the set value Q in S5, so that the misfire is determined. (S7).

Thus, also in this embodiment, in addition to the normal engine misfire, the smoldering misfire can be accurately detected, and the normal combustion state can be determined without error, thereby improving the engine misfire performance.

Note that the engine misfire determination element of the first aspect and the second
Alternatively, the third engine misfire determination element may be appropriately combined. The flowchart is shown in FIG.

[Effects of the Invention] As described above, according to the present invention, when detecting engine misfire, it is possible to prevent oversight of the ion current detection value, or to prevent smoldering misfire from being erroneously determined as normal combustion, or Both effects can be achieved at the same time, so that the performance of engine misfire detection can be improved and its reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of an apparatus used for an engine current misfire detection method according to the present invention, FIG. 2 is an explanatory diagram showing an operation state thereof, FIG. 3, FIG. 4, FIG. FIG. 6 is a flowchart illustrating various aspects of engine misfire detection according to the present invention, and FIG. 7 is an explanatory diagram showing a conventional problem. 1. Control unit (ignition timing control means, ion current sampling means, engine misfire determination means), 2
... Crank angle sensor, 8 ... Ignition power transistor, 9 ... Ignition coil, 10 ... Ion current detection circuit, 12
…… Spark plug, 13 …… Capacitor, 14 …… Resistance, 15…
…diode.

Continuation of front page (56) References JP-A-3-246347 (JP, A) JP-A-3-237251 (JP, A) JP-A-4-17774 (JP, A) JP-A-3-81544 (JP) , A) JP-A-4-104033 (JP, A) JP-A-57-193767 (JP, A) JP-B-7-111154 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB Name) F02D 43/00-45/00 F02P 1/00-23/04

Claims (10)

(57) [Claims] 1. A method for detecting a current (ion current) between spark plug gaps flowing when an electric field is applied to gas ionized by combustion of an engine and determining the presence or absence of misfire in the engine, assuming normal combustion. Then, the detection operation of the ion current is performed at a plurality of time points in the time zone in which the ion current is expected to flow normally, and any of the detection values at the plurality of time points is set to a set value (grand level). If the following, an engine misfire detection method based on the ion current method, which determines that an engine misfire has occurred. 2. A method of detecting a current (ion current) between spark plug gaps flowing when an electric field is applied to gas ionized by combustion of an engine to determine whether or not the engine has misfired, assuming normal combustion. In each time zone in which the ion current is expected to flow normally, an ion current detection operation is performed in that time zone, and based on the detected value, the presence or absence of engine misfire is determined, and the time zone is excluded. The detection operation of the ion current is also performed at the time when the detection is performed. If the detected value in the time zone is equal to or more than the reference level, the determination of the engine misfire (smoldering misfire) is given priority over the determination based on the detected value in the time zone. A method for detecting misfire of an engine. 3. A method of detecting a current (ion current) between spark plug gaps flowing when an electric field is applied to gas ionized by combustion of an engine to determine whether or not a misfire has occurred in the engine, assuming normal combustion. Performing an ion current detection operation in each time zone in which the ion current is expected to flow normally, and further performing an ion current detection operation outside of the time zone, inside and outside these time zones. A method for detecting a misfire of an engine by an ion current method, wherein a difference between the detected values of the two is compared with a set value to determine the presence or absence of an engine misfire. 4. A method for detecting a current (ion current) between spark plug gaps flowing when an electric field is applied to gas ionized by combustion of an engine and determining the presence or absence of misfire in the engine, assuming normal combustion. In each time period in which the ion current is expected to flow normally, the detection operation of the ion current at a plurality of points in time is executed, and the presence or absence of engine misfire is determined based on the plurality of detected values, An ion current detection operation is performed outside the time period, and if the detected value is equal to or greater than the reference level, the engine misfire (smoldering misfire) takes precedence over the determination based on the time period detection value. A) detecting an engine misfire. 5. A method for detecting a current (ion current) between spark plug gaps flowing when an electric field is applied to gas ionized by combustion of an engine to determine the presence or absence of misfire in the engine, assuming normal combustion. Then, for each time zone in which the ion current is expected to flow normally, the operation of detecting the ion current at a plurality of points in time is executed (detected values at this time are A and B), and The detection operation of the ion current out of the band is executed (the detected value at this time is assumed to be C), the respective values of the detected values A and B and the detected value C are obtained, and the difference therebetween is set to the set value Q. An engine misfire detection method based on an ion current method, wherein the presence or absence of engine misfire is determined in comparison with the above. 6. One of the first to fifth claims.
In the section, the predicted ion current time zone is replaced with a range of the crank angle of the engine, and the ion current detection operation timing executed within the time zone and outside the time zone is replaced with a predetermined crank angle. A method for detecting misfire of an engine by an ion current method, wherein the misfire is detected. 7. Means for applying an electric field to the gas ionized by combustion of the engine using an electrode of a spark plug, and detecting a current (ion current) flowing between the spark plug gaps when the gas is applied by the electric field. In the device for determining the presence or absence of engine misfire based on the value, a plurality of different predetermined crank angles (here, the crank angle is assumed to be normal combustion of the engine, Means for capturing an ion current detection value at that time in a crank angle range corresponding to a time zone expected to flow normally), and ion current detection values captured at the plurality of different crank angles Means for judging engine misfire when any of them is equal to or smaller than a set value. 8. Means for applying an electric field to the gas ionized by combustion of the engine using an electrode of a spark plug, and detecting a current (ion current) flowing between the spark plug gaps when the electric field is applied. In the apparatus for determining the presence or absence of engine misfire based on the following, a plurality of different predetermined crank angles (at least one of the crank angles is assumed to be normal combustion of the engine, Means for taking in an ion current detection value at that time in a crank angle range corresponding to a time zone in which an ion current is expected to flow normally), and taking in at a crank angle outside the time zone. Means for preferentially determining engine misfire (smoldering misfire) if the detected ion current value is equal to or higher than a reference level (including a ground level); Means for determining the presence or absence of engine misfire by comparing the detected ion current value taken at the crank angle within the time period with a set value on the assumption that the misfire has not been determined by the objective determination. An ion current type engine misfire detection device, comprising: 9. A means for applying an electric field to the gas ionized by combustion of the engine by using an electrode of a spark plug, and detecting a current (ion current) flowing between the charge plug gaps when the electric field is applied. In the apparatus for determining the engine misfire based on the following, as the engine misfire determination data for each time, a plurality of different predetermined crank angles (at least one of the crank angles is assumed assuming normal engine combustion) The ion current detection value at that point in time is set from the crank angle range corresponding to the time zone in which the ion current is expected to flow normally, and the other is set from the crank angle out of the time zone. Means for determining whether an engine misfire has occurred by comparing a difference between detected ion current values taken at crank angles inside and outside the time zone with a set value. It is Te engine misfire detection apparatus of the ion current method characterized by. 10. In any one of the seventh to ninth aspects, when it is determined that there is an engine misfire, the fuel injection to the cylinder to be determined is temporarily stopped. An ion current type engine misfire detection device characterized by comprising means for generating a signal.