JP2917198B2 - Device for detecting combustion state of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a combustion state of an internal combustion engine, and more particularly to an apparatus for detecting a combustion state based on an integral value of an in-cylinder pressure.

[0002]

2. Description of the Related Art Conventionally, the in-cylinder pressure of an internal combustion engine has been detected,
Based on the integral value of the in-cylinder pressure within a predetermined integral section,
Detection of the occurrence of misfire has been performed (see Japanese Utility Model Laid-Open No. 64-15937). By using the integrated value of the in-cylinder pressure as described above, accurate misfire detection can be performed even when noise is superimposed on the pressure detection signal, as compared to the case where misfire is detected using the instantaneous value of the in-cylinder pressure. .

[0003]

However, even if the combustion state is detected on the basis of the integrated value of the in-cylinder pressure, the integral at the time of misfiring in a low-speed low-load region where the absolute value of pressure generation due to combustion is small. Since there is no large deviation between the value and the integral value during normal combustion, there is a problem that it is difficult to detect misfire with high accuracy.

The present invention has been made in view of the above-mentioned problems, and a clear deviation occurs in the integrated value of the in-cylinder pressure between misfire and normal combustion even in a low-speed low-load region where the pressure generated by combustion is small. Thus, an object of the present invention is to improve the misfire detection accuracy in a low rotation and low load range.

[0005]

Therefore, a combustion state detecting apparatus for an internal combustion engine according to the present invention is configured as shown in FIG. In FIG. 1, the in-cylinder pressure detecting means detects the in-cylinder pressure of the internal combustion engine, and the in-cylinder pressure integrating means detects the in-cylinder pressure detecting means for each of a plurality of integral sections dividing a predetermined crank angle range. The cylinder pressure.

The weight setting means is means for setting the weight of the in-cylinder pressure integrated value for each of the plurality of integration sections.
Therefore, the weight is set to be larger in the latter half of the combustion . The integral value weighting means weights each of the in-cylinder pressure integrated values obtained for each of the plurality of integration sections by the in-cylinder pressure integrating means by weighting for each of the integration sections set by the weight setting means. To obtain an integral value of the in-cylinder pressure in the predetermined crank angle range.

Here, the combustion state detecting means detects the combustion state of the engine based on the integral value of the in-cylinder pressure in the predetermined crank angle range obtained by the integral value weighting means.

[0008]

With this configuration, the predetermined crank angle range is divided into a plurality of integral sections, and the in-cylinder pressure is integrated for each of the plurality of integral sections. Then, when obtaining the in-cylinder pressure integrated value in the predetermined crank angle range, weighting is performed for each integration section and the integrated values are summed.

That is, the integration result in the integration section in which the change in the combustion state (presence or absence of misfire) greatly appears as the change in the in-cylinder pressure integrated value greatly affects the final total value. the total value of the integration result in the integration interval state, and are not to exhibit a change in definite value by a change in the combustion state, the absolute value of the pressure caused by the combustion
In the low-rotation low-load range where it becomes smaller, it burns after a long period of time,
The change in in-cylinder pressure due to the presence or absence of a misfire indicates the maximum combustion pressure.
After burning, because it becomes more clear later than the rank angle position
The weight is set to be larger halfway.

[0010]

Embodiments of the present invention will be described below. In FIG. 2 showing one embodiment, air is sucked into an internal combustion engine 1 through an air cleaner 2, a throttle chamber 3, and an intake manifold 4. The combustion exhaust from the engine 1 is supplied to an exhaust manifold 5, an exhaust duct 6, a three-way catalyst 7,
It is discharged to the atmosphere via the muffler 8.

The throttle chamber 3 is provided with a throttle valve 9 which opens and closes in conjunction with an accelerator pedal (not shown). The throttle valve 9 adjusts the intake air amount of the engine 1. In addition, ignition plugs (not shown) are attached to the combustion chambers of the cylinders (# 1 to # 4), respectively. The ignition plugs are paired with the ignition plugs and serve as in-cylinder pressure detection means for each cylinder. In-cylinder pressure sensors 10a to 10d are provided.

The in-cylinder pressure sensors 10a to 10d are
In addition to the type mounted as a washer for an ignition plug as disclosed in Japanese Patent Application Laid-Open No. 3-17432, the sensor section as disclosed in Japanese Patent Application Laid-Open No. 4-81557 is directly exposed to the combustion chamber to make the in-cylinder pressure absolute. It may be of a type that detects pressure. The camshaft (not shown) of the engine 1 is provided with a crank angle sensor 11 for detecting a crank angle through rotation of the camshaft.

[0013] The crank angle sensor 11 is used in the present embodiment.
In the cylinder engine 1, the sensor outputs a reference angle signal REF for each crank angle 180 ° corresponding to a stroke phase difference between cylinders and a unit angle signal POS for each unit crank angle. The reference angle signal REF is such that a detection signal corresponding to at least one specific cylinder can be distinguished from other detection signals by a pulse width or the like so that cylinder determination can be performed.

The outputs of the in-cylinder pressure sensors 10a to 10d and the crank angle sensor 11 are output to a control unit 12 provided for controlling the engine. The control unit 12 having a built-in microcomputer controls the fuel injection amount and ignition timing by a fuel injection valve (not shown), and controls each cylinder based on the outputs of the in-cylinder pressure sensors 10a to 10d as shown in the flowchart of FIG. The combustion state (misfire state) is detected.

In this embodiment, in-cylinder pressure integrating means,
As shown in the flowchart of FIG. 3, the control unit 12 has functions as weight setting means, integral value weighting means, and combustion state detecting means as software. The flowchart of FIG. 3 shows a predetermined crank angle range (for example, ATDC 10 ° to BTDC 70 ° or 100 °).
The interrupt is executed with the beginning of the in-cylinder pressure integration section set as (°) as a trigger.

In the flowchart of FIG. 3, first, step 1 (referred to as S1 in the figure; the same applies hereinafter).
Then, based on the detection signal from the crank angle sensor 11, divided integral sections A to E (see FIG. 4) obtained by dividing the predetermined crank angle range into a plurality are detected.
The in-cylinder pressure detected by the in-cylinder pressure sensors 10a to 10d is integrated for each E, and the in-cylinder pressure integrated value IM for each of the divided integration sections A to E is integrated.
EP _{A to} IMEP _E are obtained.

In the present embodiment, the predetermined crank angle range is divided into five equal angles A through E, but it is clear that the set range of the crank angle and the number of divisions are not limited. Alternatively, a different angle range may be set for each of the divided integration sections A to E. In the next step 2, it is determined whether the crank angle position where the in-cylinder pressure is currently integrated falls into any of the divided integration sections A to E, and is set in advance for each of the divided integration sections A to E. Weighting constants K _{A to} K
Search the corresponding weighting constant from _E.

In this embodiment, the weighting constant K_A~
K_ETo K_A= 5%, K_B= 10%, K _C= 25%, K_D= 30
%, K_E= 30%, and is set in the latter half of the divided integration sections A to E.
Weighting is increased according to the This is for burning
In the low rotation and low load range where the absolute value of pressure
Changes in in-cylinder pressure depending on the presence or absence of misfiring after burning for a long time
Is much brighter than the crank angle position that shows the maximum combustion pressure.
This is to be sure.

Therefore, according to the present embodiment, the cylinder pressure integrated value (total of IMEP _{A to} IMEP _E ) within the predetermined crank angle range shows a clearer difference depending on the presence or absence of misfiring, as compared with the case without weighting. As a result, it is possible to detect misfire occurrence with high accuracy even in a low rotation speed and low load range. The weighting constants K _{A to} K _E for each of the divided integration sections A to _E may be changed according to the engine operating conditions.

In step 2, a weighting constant K _x (x = A to E) in the divided integration section is set. In the next step 3, the integral value IME in the divided integration section is set.
P _x (x = A to E) is multiplied by the weighting constant K _x to update and set the integration result. In step 4, it is determined whether or not the integration of the in-cylinder pressure and the update setting with the weighting constant K _x (x = A to E) of the integration result have been completed for all of the divided integration sections A to E, Until the integration and weighting processing in the divided integration section E is completed, step 1
Steps 3 to 3 are repeated.

When the processing has been completed for all of the divided integration sections A to E, the process proceeds to step 5, where the integration is performed for each of the divided integration sections A to E, and the weighting constants K _A to _{D for} each of the divided integration sections A to E are set.
Integrated value has been weighted by K _E IMEP _A ~IMEP
By summing _E , an integral value of the in-cylinder pressure within a predetermined crank angle range is obtained, and the total value is set in TIMEP.

In the next step 6, the in-cylinder pressure integral value T
By comparing IMEP with the reference value, the presence or absence of misfire is detected for each cylinder. The reference value is a value set based on engine operating conditions, or the in-cylinder pressure integrated value TI
A value set based on the weighted average value of the MEP can be used, and the detection of the combustion state (misfire state) performed using the in-cylinder pressure integrated value TIMEP is not limited.

The in-cylinder pressure integrated value TIMEP is calculated so that a clear difference is produced depending on the combustion state by weighting each divided section. High accuracy misfire diagnosis is possible even in the range.

[0024]

As described above, according to the present invention, in an apparatus for detecting a combustion state based on an integral value of an in-cylinder pressure, weighting is performed for each of a plurality of divided integral sections.
At the same time, by setting a larger weight in the latter half of the combustion , even in the low rotation and low load range, the in-cylinder pressure integrated value can clearly show a different value depending on the combustion state. There is an effect that the detection accuracy of the combustion state can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a system schematic diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a state of misfire detection according to the embodiment.

FIG. 4 is a diagram showing a state of division of an integration section in the embodiment.

[Explanation of symbols]

 1 internal combustion engine 10a-10d cylinder pressure sensor 11 crank angle sensor 12 control unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-301946 (JP, A) JP-A-4-81557 (JP, A) JP-A-4-321175 (JP, A) JP-A-4-321 104033 (JP, A) Fully open sho 64-15937 (JP, U) Fully open sho 63-17432 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 45/00 G01M 15 / 00

Claims (1)

(57) [Claims] An in-cylinder pressure detecting means for detecting an in-cylinder pressure of an internal combustion engine, and an in-cylinder pressure detected by the in-cylinder pressure detecting means are integrated for each of a plurality of integration sections dividing a predetermined crank angle range. Cylinder pressure integrating means, and means for setting a weight of the cylinder pressure integrated value for each of the plurality of integration sections, wherein the weight is set to be larger in the latter half of combustion.
A weight setting means for constant, the cylinder internal pressure integral cylinder pressure integrated value obtained for each of the plurality of integral intervals in unit, by performing weighting to each by the weighting for each integration interval for each set by the weight setting means Integral value weighting means for summing and calculating an integrated value of the in-cylinder pressure in the predetermined crank angle range; and combustion of the engine based on the integrated value of the in-cylinder pressure in the predetermined crank angle range obtained by the integrated value weighting means. A combustion state detection device for an internal combustion engine, comprising: combustion state detection means for detecting a state.