JP2922027B2 - Device for detecting combustion state of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion state of an internal combustion engine,
In particular, the present invention relates to a device that detects a misfire state from the state of ion current in a cylinder, and particularly relates to a gasoline engine for an automobile.
The present invention relates to a combustion state detection device for an internal combustion engine suitable for an engine whose operating state changes over a wide range.

[0002]

2. Description of the Related Art Conventionally, an ignition plug provided in a cylinder of an engine and a probe dedicated to detection have been used to detect an ion current appearing in the cylinder during a combustion stroke of an internal combustion engine to detect a combustion state of the engine. Various engine combustion state detection devices based on the so-called ion current detection method have been proposed, examples of which are disclosed in Japanese Patent Application Laid-Open Nos.
No. 0-40751 and JP-A-2-104978. And among these publications, in particular, in the publication of JP-A-2-104978,
It is mentioned that engine misfire should be detected by ionic current.

[0003]

In the above-mentioned prior art, the combustion state is determined from the level of the detected ion current. At this time, if the detected ion current level is only the combustion state of the engine, No consideration has been given to the fact that it is also affected by the operating conditions, so when applied to an engine whose operating conditions vary widely, high-precision detection performance is always achieved over the entire operating range. There was a problem that it was difficult to secure them.

The present invention has been made in view of such a problem, and it is possible to always reliably determine the combustion state of an engine irrespective of a change in the operation state of the engine and to detect that the engine is in a normal combustion state. It is another object of the present invention to provide a combustion state detection device for an internal combustion engine using an ion current detection method, which can reliably determine and detect even the occurrence of a misfire of an engine or a smoldering state of a spark plug.

[0005]

The above object is achieved by providing means for optimizing a comparison judgment value for judging a level of an ion current in accordance with an operating state of an engine. Specifically, a means for deriving an optimum comparison determination value by calculation from the detected values of ion currents over a plurality of times in the past is provided. On the other hand, a comparison determination value corresponding to the operating state of the engine is mapped in advance. In addition, means for deriving a comparison determination value by searching this map is provided.

[0006]

The above-mentioned means works so as to give an optimum comparison value of the ion current level each time according to the operating state of the engine. Thus, good detection performance can be realized without being affected by fluctuations in the operating state of the engine.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a combustion state detecting apparatus for an internal combustion engine according to the present invention. FIG. 3 shows an embodiment in which the present invention is applied to an engine of a one-plug one-coil type electronic power distribution system (DIS) having one ignition coil for each ignition plug of each cylinder. 1, a control unit, 2
Is the crank angle sensor output, 3 is the intake flow sensor output, 4
Is the throttle sensor output, 5 is the battery voltage value for the power supply,
6 is a coolant temperature sensor output, 7 is an ignition signal amplifier, 8 is a power transistor, 9 is an ignition coil, 10 is an ion current detection circuit, 11 is an ignition timing signal (IGN), 12 is a spark plug, and 13 is an ion current output value. , 14 is an ion current processing circuit, 15 is a fuel injection signal (INJ), 16 is an injection signal amplifier, 17 is a power transistor, and 18 is an injector.

The control unit 1 includes a ROM as a storage element for storing fixed data necessary for ignition timing control and the like, a RAM capable of reading and writing data, and various data.
It has a CPU that performs digital calculation processing of the crank angle sensor output 2, intake air flow sensor processing output
(Qa) 3, a throttle sensor output (Θth) 4, a battery voltage value (Vb) 5, a water temperature sensor output (Tw) 6, and the like. Timing signal (IGN) 11 and fuel injection signal (I
NJ) 15 to perform ignition timing control and fuel supply control.

The ignition timing signal (IGN) 11
Is amplified by a signal amplifier 7 and supplied to a power transistor 8 for ignition. As an actual ignition mechanism at this time, according to the ignition timing signal (IGN) 11, when the power transistor 8 is cut off, a high voltage corresponding to the cutoff current is generated on the secondary side of the ignition coil 9, The spark plug 12 enables sparking. The fuel injection signal (INJ) 15 is amplified by the signal amplifier 16 and supplied to the power transistor 17 to drive the injector 18.

The ion current detection circuit 10 includes an ignition coil 9
, A Zener diode 10a connected between the secondary coil ground terminal and the ground, a capacitor 10b, a resistor 10c,
When the spark plug 12 sparks and an ignition current flows, a voltage specified by the Zener diode 10a is stored in the capacitor 10b, and the heat generated by the combustion causes the spark plug in the cylinder to be opened. 12
The ion current generated by ionization of the gas in the vicinity of is detected as a potential difference between both ends of the resistor 10c,
It functions to generate an ion current output value (Ion) 13.

An ionic current processing circuit 14 receives an ionic current output value (Ion) 13 and multiplies it by an integration window, and performs integration processing or peak hold of the maximum, minimum and average values. The processing result is fed back to the control unit 1 and the combustion state there is determined. In the case of the integration processing, as shown in the lower right of FIG. First, the ion current output value (Ion) 13 shown below is multiplied by the integration window shown below, and this is integrated as shown in FIG.

The output of the ion current processing circuit 14 is input to the control unit 1, where it is subjected to A / D conversion and then subjected to data processing as described below as an ion current detection value to determine the combustion state. Is detected.

First, FIG. 1 shows a first embodiment of a comparison judgment value calculation process for detecting a combustion state. In this embodiment, a comparison judgment value is calculated by a moving average of ion current detection values. This is an example of calculating. In step 210,
This time (n times) ion current detection value (A / D) n and comparison level
(BGL) is compared with a comparison judgment value f (BGL), and the ion current detection value (A / D) n is compared with the comparison judgment value f.
(BGL), it is determined that the combustion state is normal.
In step 230, a new comparison level (BGL) is calculated by a moving average calculation process of the ion current detection value, and in step 240, it is classified into normal combustion. On the other hand, in step 210, the ion current detection value (A /
D) When n is equal to or smaller than the comparison determination value f (BGL),
The combustion state is determined to be abnormal, and in step 250, it is classified as an abnormal combustion state.

Next, FIG. 2 shows a second embodiment of the comparison judgment value calculation processing for detecting the combustion state. The comparison judgment value of the ion current detection value is obtained by a table search. In one embodiment of the present invention, the operation state of the internal combustion engine is determined in step 260, and a comparison level corresponding to the operation state of the internal combustion engine is recorded in step 270.
In step 280, the search value (THL) and the ion current detection value are compared. If it is determined that the combustion is normal, in step 290, the combustion is classified as normal, otherwise, in step 300, the combustion is classified as abnormal.

Here, as the ion current detection value (A / D) n, the average value of the detection values of all the cylinders of the engine may be used, or the detection value from a specific cylinder may be used as it is. good.

FIG. 4 shows a third embodiment of the present invention, in which a combustion state is determined as a normal combustion, smoldering state,
As shown in FIG. 4A, in one embodiment of the present invention, which is classified into three types of misfire states, first in step 310, the comparison level BGL is obtained by the method described in the embodiment of FIG.
Is calculated. In the next step 320, the ion current detection value (A / D) n is first compared with a first comparison determination value (K ₁ (BGL) + Voffset) based on the comparison level (BGL). If the detected value exceeds the comparison determination value, it is determined that the engine is in a normal combustion state. In this case, in step 350, the combustion is classified as normal combustion.

If it is determined in step 320 that the combustion is abnormal, then in the next step 330, a second comparison determination value (K ₂ (BGL) + Voffset) based on the comparison level (BGL) is set. ), And if the detected value exceeds the comparison determination value, it is determined that the vehicle is in a smoldering state. In this case, in step 360, the combustion is classified as smoldering combustion. Then this step 33
If the detected value is 0 or less, and if the detected value is equal to or smaller than the comparison determination value, it is determined that a misfire has occurred.

[0018] FIG. 4 (b), shows the calculation processing of the coefficient K ₂ of the second comparison determination value used in the coefficient K ₁ and step 330 in the first comparison determination value used in step 320, In this embodiment, these coefficients are tabulated in advance with respect to the engine speed (N), and are selected according to the engine speed (N). As a result, the combustion state determination region is always set appropriately, and accurate detection can be obtained.

[0019] Here, the ion-current detection value (A / D) n,
The relation between the first comparison judgment value (K ₁ (BGL) + Voffset) and the second comparison judgment value (K ₂ (BGL) + Voffset) and Voffset.
The relation is as shown in FIG.

Next, FIG. 5 shows a fourth embodiment of the present invention.
Comparison level based on moving average of detected ion current
According to an embodiment of the present invention, the combustion state is classified into four types of a knocking occurrence state, a normal combustion state, a smoldering state, and a misfire state by a method of obtaining (BGL). First, in step 400, FIG. The comparison level BGL is calculated by the method shown in the embodiment. Then, thereafter, first in step 410, the ion current detection value (A / D) n is changed to a third comparison determination value (K ₃ (B ₃ ) based on the comparison level (BGL).
GL) + Voffset). If the detected value exceeds the comparison determination value, it is determined that knocking has occurred. In this case, in step 450, the combustion is classified as knocking combustion.

If it is determined in step 410 that there is no knocking, the process proceeds to step 420,
The first comparison determination value (K ₁ ) based on the comparison level (BGL)
(BGL) + Voffset). If the detected value exceeds the comparison determination value, it is determined that the combustion state is normal,
In this case, in step 460, it is classified as normal combustion.

If it is determined in step 420 that the combustion is abnormal, in the next step 430, the second comparison determination value (K ₂ (BGL) + Voffset) based on the comparison level (BGL) is set. Is determined, and if the detected value exceeds the comparison determination value, it is determined that the vehicle is smoldering. In this case, in step 470, the smoldering combustion is classified. Then, step 43
If the detected value is 0 or less and the detected value is equal to or smaller than the comparison determination value, it is determined that a misfire state has occurred.

FIG. 5B shows a third example used in step 410.
First coefficient K ₁ in the comparison determination value, it shows the calculation processing of the coefficient K ₂ of the second comparison determination value used in step 430 for use by a factor K ₃ and step 420 of, in this embodiment These coefficients are tabulated in advance with respect to the engine speed (N), and are selected based on the engine speed (N).
Therefore, the combustion state determination region is always appropriately set according to the operation state of the engine, and accurate detection can be obtained.

[0024] Here, the ion-current detection value (A / D) n,
The first comparison determination value _{(K 1 (BGL) + Voffset} ) and the second comparison determination value _{(K 2 (BGL) + Voffset} ), it the relationship between the third comparative determination value _{(K 3 (BGL) + Voffset} ), Fig. 5 (b)
Shown in

In the above embodiment, the constant Kn (n is 1 to 3) is set to the engine speed N in FIGS. 4 (b) and 5 (b).
, But may be obtained as a function of various parameters representing the operating state of the engine, such as the engine load, air-fuel ratio, cylinder pressure, and battery voltage. Further, in the above embodiment, the moving average method and the table search method are referred to as the means for calculating the comparison determination value. However, as a function of the ion current detection value in the state where an actual misfire has occurred. , A comparison level may be obtained.

That is, in this embodiment, a control means for forcibly causing a misfire is provided in the engine, whereby the detected ion current value corresponding to the forcibly caused misfire state is set to the basic amount BGLMIS, and the comparison level is set. (BGL) is calculated by the following equation (1) or (2) to obtain a comparison determination value. BGL = K ₄ · (BGLMIS) (1) BGL = K ₅ + (BGLMIS) (2) where K ₄ and K ₅ are coefficients.

In this embodiment, any method can be adopted as a control means for forcibly causing a misfire in the engine. However, in consideration of deterioration of exhaust gas, fuel cut control is an appropriate method. is there.

Returning to FIG. 3, the control unit 1
As described above, the combustion state of the engine is monitored, and it is detected whether the engine is in a knocking occurrence state, a normal combustion state, a smoldering state, or a misfire state, and an ignition timing signal (IGN) 11 is determined in accordance with the detection result. And fuel injection signal (INJ) 15
If a knocking state is detected, the ignition timing signal (IGN) 11 is controlled by a retard control. If a misfire state or a smoldering state is determined, the fuel injection signal (IN
J) Limiting the pulse width of 15 or performing fuel cut by setting it to zero, along with the ignition timing signal
(IGN) 11 is controlled.

Therefore, according to this embodiment, the optimum judgment value of the ion current level is given each time according to the operating state of the engine, so that it is affected by the fluctuation of the operating state of the engine. Without this, good detection performance is always maintained and the engine can be controlled accurately.

In this embodiment, one ion current detection circuit 10 is provided for each cylinder. For example, one ion current detection circuit 10 is provided for a plurality of cylinders such as two opposed cylinders. A circuit may be provided.

[0031]

According to the present invention, the combustion state of the engine can be determined by the ion current detection method without being affected by the operation state of the engine, and the operation state can always be controlled accurately.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an operation of a combustion state detection device for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the second exemplary embodiment of the present invention.

FIG. 3 is a configuration diagram showing one embodiment of a combustion state detection device for an internal combustion engine according to the present invention.

FIG. 4 is a flowchart illustrating an operation of a third exemplary embodiment of the present invention.

FIG. 5 is a flowchart illustrating the operation of the fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 control unit 2 crank angle sensor output 3 intake flow sensor output 4 throttle sensor output 5 5 power supply battery voltage value 6 cooling water temperature sensor output 7 ignition signal amplifier 8 power transistor 9 ignition coil 10 ion current detection circuit 11 ignition timing signal (IGN 12) Spark plug 13 Ion current output value 14 Ion current processing circuit 15 Fuel injection signal (INJ) 16 Injection signal amplifier 17 Power transistor 18 Injector

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-7536 (JP, A) JP-A-60-40751 (JP, A) JP-A-2-104978 (JP, A)

Claims (6)

(57) [Claims] 1. A means for detecting an ion current detected via a spark plug of an internal combustion engine, and a combustion state detection device for an internal combustion engine for detecting a combustion state of the internal combustion engine from a detection result of the ion current, Ions when the combustion state of the internal combustion engine is normal
A comparison determination value setting unit that sets a comparison determination value based on a moving average calculation of a current component; and a knocking state by comparing the comparison determination value set by the comparison determination value setting unit with the detected ion current value. A combustion state detection device for an internal combustion engine, comprising: a knocking determination unit for determining. 2. A means for detecting an ion current detected via a spark plug of an internal combustion engine, and a combustion state detection device for an internal combustion engine for detecting a combustion state of the internal combustion engine from a detection result of the ion current, A comparison determination value setting means for setting a comparison determination value based on a moving average calculation of an ion current component when an abnormal state is forcibly caused as a combustion state of the internal combustion engine; and An apparatus for detecting a combustion state of an internal combustion engine, comprising: abnormality determination means for comparing a comparison determination value with a detected ion current value to determine an abnormal state of combustion. 3. A means for detecting an ion current detected through a spark plug of an internal combustion engine, and a combustion state detection device for an internal combustion engine for detecting a combustion state of the internal combustion engine from a detection result of the ion current, Ions when the combustion state of the internal combustion engine is normal
Moving average calculation of current component or transfer of ion current component when an abnormal condition such as misfire or knocking is forcibly caused
Comparison judgment value setting means for setting a comparison judgment value based on a moving average calculation, and a plurality of comparison judgment values set by the comparison judgment value setting means, and comparing the detected ion current value, a normal state, A combustion state detection device for an internal combustion engine, comprising: a determination unit configured to determine a misfire or a knocking state. 4. The invention according to claim 1, wherein the comparison determination value setting means is configured to determine a driving state amount of the engine based on a driving state amount detected by a sensor group that detects the operation state amount of the engine.
A combustion state detection device for an internal combustion engine, wherein a search value searched from predetermined data or a data group is provided as the comparison determination value. 5. The combustion state detecting device for an internal combustion engine according to claim 3, wherein the forcible misfire state of the engine is caused by fuel cut control. 6. The invention according to claim 1, wherein the ion current component is at least one of an average value of detection values of all cylinders of the engine and a detection value from a specific cylinder. A combustion state detection device for an internal combustion engine.