JPH03124970A - Combustion control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the judging time and precision of knocking and improve combustion precision with a simple structure by correcting a basic control value based on the output of a knock judging means, and calculating the control value controlling the combustion state of an engine. CONSTITUTION:An operation state detecting means (a) detecting the operation state of an engine, a light detecting means (b) detecting the light generated in the combustion chamber of the engine, a knocking judging means (c) calculating the time from the build-up of the combustion light to the maximum combustion light based on the output of the light detecting means (b) and judging knocking based on the calculated result, and a basic value setting means (d) setting the basic control value controlling the combustion state based on the operation state of the engine are provided. The basic control value is corrected based on the output of the knocking judging means (c), the control value controlling the combustion state of the engine is calculated by a control means (e), and parameters related to the combustion state of the engine are operated by a combustion operating means (f) based on the output of the control means (e).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion control device for an internal combustion engine, and more particularly to a combustion control device that improves drivability while suppressing knocking in an internal combustion engine such as an automobile.

(Prior Art) The ignition timing of an internal combustion engine is one of the most important factors in controlling the combustion state, and particularly needs to be determined depending on the state of the engine so that the engine can be operated optimally. Generally speaking, when considering engine efficiency and fuel consumption, the minimum advance angle at maximum torque, so-called MBT (Minimum advance
It is known that it is best to ignite near MBT (for Be5t Torque), and it is necessary to change the ignition timing to MBT depending on the engine condition.

However, in certain engine conditions, advancing the ignition timing causes knocking, making it impossible to operate the engine stably. For example, knocking is likely to occur during transient operation.

Therefore, as a control device designed to avoid knocking, there is known a control device as described in, for example, Japanese Patent Application Laid-Open No. 135365/1983. In this device, a knock sensor is attached to the cylinder block of the engine, and the knock sensor detects high-frequency vibrations of the cylinder block, processes this vibration as a signal, determines the presence or absence of knocking, and determines the knock intensity. Based on the determination results, The ignition timing is controlled to avoid knocking.

(Problem to be Solved by the Invention) However, in such conventional combustion control devices for internal combustion engines, the presence or absence of knocking and the knocking intensity are determined based on high-frequency vibrations from the cylinder block due to knocking, and the ignition timing is determined. In other words, the knocking phenomenon was converted into cylinder block vibration, and the ignition timing was determined through controls such as delaying the ignition timing. Therefore, the knocking intensity judgment may differ depending on the position of the knocking detection sensor. Otherwise, there is a problem that the knocking detection timing is delayed, resulting in inappropriate ignition timing and a decrease in control accuracy.

The above are the problems when controlling the ignition timing as a combustion state, but the problem is not limited to this, but when detecting knock information and controlling the combustion state (for example, control of swirl and air-fuel ratio)
has a similar problem.

On the other hand, apart from the type that detects knocking by vibration of the cylinder block, there is also a physical quantity (
A device that detects the presence or absence of knock based on ions, light, temperature, etc. has also been proposed (see Japanese Patent Laid-Open No. 61-250366). This system individually detects the combustion status of different spaces within the cylinder using 'f3i number sensors, and by processing this detection signal, it is possible to detect the maximum pressure corresponding angle and abnormal combustion such as knocking. . Therefore, it is also conceivable to control the ignition timing using such a technique.

However, this device only uses multiple sensors to compare multiple physical quantities generated during combustion and detects the direction of travel and passing time to determine abnormal combustion within the cylinder, and is different from the conventional example described above. Similarly, the installation of the sensor has disadvantages in that the knocking intensity determination may differ depending on the position, the timing of knocking detection may be delayed, and the configuration for detection becomes complicated.

(Objective of the Invention) Therefore, the present invention aims to improve the accuracy of combustion control by increasing the knocking determination time and accuracy with a simple configuration by determining knocking based on temporal changes in light intensity within the combustion chamber. .

(Means for Solving the Problems) In order to achieve the above object, the combustion control device for an internal combustion engine according to the present invention has an operating state detection means a for detecting the operating state of the engine, as a basic conceptual diagram thereof is shown in FIG. Then, the light detection means detects the light generated in the combustion chamber of the engine, and the time from the rise of the combustion light to the maximum combustion light is calculated based on the output of the light detection means, and the knocking is detected based on the calculation result. a basic value setting means d for setting a basic control value for controlling the combustion state based on the operating state of the engine; and a basic value setting means d for correcting the basic control value based on the output of the knock judgment means C. The engine includes a control means e that calculates a control value for controlling the combustion state of the engine, and a combustion moderation means f that operates parameters related to the combustion state of the engine based on the output of the control means e.

(Function) In the present invention, light generated within the combustion chamber of the engine is detected.1. The time from the rise of this combustion light to the maximum combustion light is calculated, knocking is determined based on the result of the calculation, and the combustion state is controlled based on the result of the determination.

Therefore, the combustion state is determined based on the signal from the knocking phenomenon itself, and with a simple configuration, the knocking determination time and accuracy are increased, and the accuracy of combustion control (2) is improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

Figures 2 to 6 show combustion control i'ill of an internal combustion engine according to the present invention.
FIG. 2 is a diagram showing a first embodiment of the device, and is an example in which ignition timing is controlled as the combustion state of the engine.

First, the configuration will be explained. In Fig. 2, ■ is the engine, intake air is supplied to each cylinder via the intake valve 2 of the intake port, and fuel is supplied to the injector (
(path shown).

Each cylinder is equipped with a spark plug 3, and the air-fuel mixture in the cylinder is ignited and exploded by the discharge action of the spark plug 3.
It becomes exhaust and is discharged to the outside.

Incidentally, the spark plug 3 is discharged by a signal from the ignition unit 4 which generates a high voltage pulse, and the ignition plug 3 including the ignition unit 4 corresponds to the combustion operation means 5. Also, in the figure,
6 is the cylinder head, 7 is the cylinder block, 8 is the piston, 9 is the combustion chamber, 10 is the cylinder head gasket I.
It is.

An optical fiber 11 is sandwiched between the cylinder head gasket 10, and one end face of the optical fiber 11 faces the combustion chamber 9, and the other end face is connected to a photo-electrical converter 12. The combustion light in the combustion chamber 9 is guided to the photo-electric converter 12 through the optical fiber 11, and is converted into an electrical signal by the photo-electric converter 12. Note that if a bandpass filter is used before the photo-electrical converter 12 in order to improve the detection accuracy of the optical signal, it can be used even in a state where combustion is deteriorated at low temperatures. The optical fiber 11 and the photoelectric converter 12 constitute a photodetecting means 13.

The rotation speed N of the engine 1 is detected by the rotation speed sensor 14, and the intake air ff1Qa is detected by the air flow meter 15. In addition, the water temperature Tw of the cooling water is determined by the water temperature sensor 16.
The combustion light in the combustion chamber 9 is detected by the light detection means 13. The rotation speed sensor 14, air flow meter 15 and water temperature sensor 16 are connected to the operating state detection means 17.
The signals from the operating state detection means 17 and the light detection means 13 are input to the control unit 18. The control unit 8 has the functions of a knock determination means, a basic value setting means, and a control means, and is mainly constituted by a microcomputer. The control unit 18 calculates processing values necessary for knock determination and engine combustion control based on each input signal, and outputs an ignition signal to the ignition unit 4 as necessary.

Next, the effect will be explained.

FIG. 3 is a flowchart showing an ignition timing control program, and this program is executed once every predetermined time. First, the cooling water temperature Tw, engine speed N, and intake air amount Qa are read at P, and the basic ignition timing is determined based on these values. Look amp and load this. Next, at P2, the reference value CN of the combustion period corresponding to the operating conditions at that time is read by look-up from the map shown in FIG.

Here, the combustion period is from the start of combustion (corresponding to the crank angle C3 at which the optical signal rises) to the maximum combustion light (corresponding to the crank angle CK of the maximum value of the optical signal), as shown in Fig. 5.
This corresponds to the period until . In other words, when combustion is normal, the fifth
As shown by the broken line in the figure, the combustion light intensity shows a gradual rise, but in the case of abnormal combustion such as knocking, the light intensity rises rapidly as shown by the solid line in FIG. 5, which is a peculiar characteristic. In other words, the time from the rise of combustion light to the maximum combustion light has a strong correlation with knocking. Knocking is a phenomenon in which unburned gas burns instantly, so
This is because the amount of combustion light also increases instantaneously. Moreover, among the various properties of combustion light generated by knocking, this signal (combustion light, which corresponds to an optical signal) is the one that allows the quickest determination of the presence or absence of knocking. This is because, as shown in Figure 6(a), the light intensity oscillation due to knock pressure appears after the peak of the combustion waveform, but the rise of the combustion light appears before this.For the above reasons, the combustion light The amount of light is a very important factor in determining the presence or absence of knocking.

On the other hand, a problem when using combustion time for knocking control is the fact that there are several output change signals due to combustion light, and their modes are different, as shown in FIG. 6(b). For example, it is extremely difficult to determine the presence or absence of knock by simply determining the combustion time at one slice level. Therefore, as in the present invention, the time from the rise to the maximum combustion light is calculated and compared, thereby making the determination of knock accurate. Note that the rise crank angle C5 of the optical signal is assumed to be when it exceeds a certain slice level, but the optical fiber 1
Since the ground level of the amount of light may change depending on the installation of the light source 1, it is also preferable to make a judgment based on the slope of the rise.

Therefore, based on the above theory, in this embodiment, the presence or absence of knock can be determined based on the magnitude of the rotation angle of the crank from the crank angle at which the optical signal rises to the crank angle at which the light intensity peaks. For this purpose, the crank angle at which the optical signal rises is C5, and the crank angle at which the maximum value of the optical signal is actually measured is C5, and the presence or absence of knock is determined by comparing it with the reference value CH of the combustion period described above. Although the operating conditions are shown in FIG. 4 using the engine speed and torque, they are essentially mapped using the engine speed and the intake air amount from the air flow meter 15.

Based on the above principle, P3 reads the rising crank angle C3 of the optical signal and the maximum crank angle CK, and
In step 4, it is determined whether CK-C, 50M...■ holds true. When formula 0 is established, it is determined from the relationship shown in Figure 5 that the rise of the combustion light is sudden and knocking is occurring, and the retard lI□ is set at P5 to control the ignition timing to the retard side. is calculated according to the following function.

1,, =f (C, -C,, N, Qa, Tw)...
...■ In other words, the retard N I Rl is the knock strength (CKC
8) as well as the operating conditions at that time (N, Qa,
Tw). Next, in P6, the final ignition timing I is calculated according to the following equation, and the air-fuel mixture is ignited at the corresponding timing.

19=1. . -1111...■Meanwhile, N at P4
When it is o, the advance angle amount ■□ is calculated using P according to the following equation.

In+=f (CK C5, N, Qa, Tw)...
...■ Next, at P, the final ignition MIq is calculated according to the following formula, and the current routine is ended.

1,=1. . +IAI ・・・・・・■However, I9≦
l HIT Note that I9 does not exceed IMIT (MBT advance value) and advances the ignition timing while suppressing knock, but M
Maintain the principle of BT control.

In this way, in this embodiment, knocking is determined based on the temporal change in the light intensity within the combustion chamber 9, so that knocking can be determined quickly with a simple configuration (shortening the determination time), and The accuracy can be increased, and the accuracy of ignition timing control can be improved. It also has the effect of eliminating the need for a vibration knocking sensor.

Next, FIG. 7 is a diagram showing a second embodiment of the present invention, in which the optical fiber for detecting combustion light is built into a spark plug, and the intensity of the optical signal is also controlled as a control method.
This is in addition to the factors.

In other words, the knocking phenomenon is caused by unburned air-fuel mixture becoming C-
The light signal at that time (crank angle) becomes extremely strong. Therefore, by comparing the optical signal peak value IPN (preset as a map value) during normal combustion and the measured value IPK from the optical fiber either before or after determining the rise time of the peak of combustion light, it is possible to Fine-grained control becomes possible.

Therefore, in this embodiment, after P, the above peak value IPN is read in addition to CN at P (see Figure 5), and the above measured value IP is read in addition to C3 and CK at P+z.
Load K (see Figure 5). Next, in P4, the same determination as in the first embodiment is made, and if YES, Pl, T, ≧, medium I PH,8,'', ■ However, Ko
: Determine whether the constant is established. If not, it is determined that the degree of knock is small and the process returns to Pl; if it is, the retard amount IN□ is calculated in accordance with the following equation in Pl4.

riz=f (Cx Cs, Ipx, N, Qa,
Tw)...■ Next, the PI5 calculates the final ignition timing according to the following formula.

I, -1,. -IRZ... ■On the other hand, when P4 is NO, the advance angle value IA2 is calculated in P16 according to the following formula.

Lz-f (Cx Cs, N, Qa, Tw)・
・・・・・・■ Next, 3U111 at the final ignition according to the following formula in pat
Calculate q.

! ,=I,. +IAz ・・・・・・[phase] However, 1
．． ≦IMBT Therefore, in this embodiment, since IPK and IPN are added to the determination request, it is possible to perform more fine-grained ignition timing control than in the first embodiment.

Note that the IPK output can also be used to determine whether there is an abnormality in the optical fiber.

Further, in each of the above embodiments, the ignition timing is manipulated as a parameter for controlling the combustion state, but the present invention is not limited to this, and other parameters such as the air-fuel ratio, intake swirl, etc. may be manipulated.

(Effects) According to the present invention, the knocking determination time and accuracy can be improved with a simple configuration, and the accuracy of engine combustion control can be improved.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 6 are diagrams showing a first embodiment of a combustion control device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. 4 is a flowchart showing the ignition timing control program, FIG. 4 is a map of the basic value CH during the combustion period, FIG. 5 is a diagram showing changes in the combustion light, and FIGS. ) is a diagram illustrating a state of change in combustion light due to knocking, and FIG. 7 is a flow chart showing an ignition timing control program showing a second embodiment of the combustion control device for an internal combustion engine according to the present invention. ■...Engine, 2...Intake valve, 3...Spark plug, 4...Ignition unit, 5...Combustion operation means, 6... Cylinder head, 7... Cylinder block, 8... Piston, 9... Combustion chamber, 10... Cylinder head gasket, 11・・・
... Optical fiber, 12 ... Photo-electric converter, 13 ... Light detection means, 14 ... Rotation speed sensor, 15 ... Air flow Meter, 16... Water temperature sensor, 17... Operating state detection means, 18... Control unit (knock determination means, basic value setting means, control means). Figure 1

Claims (1)

[Scope of Claims] a) operating state detection means for detecting the operating state of the engine; b) light detection means for detecting light generated within the combustion chamber of the engine; and c) combustion based on the output of the light detection means. a knock determination means that calculates the time from the rise of the light to the maximum combustion light and determines knocking based on the calculation result; and d) a basic unit that sets basic control values for controlling the combustion state based on the operating state of the engine. a value setting means; e) a control means for correcting the basic control value based on the output of the knock determination means to calculate a control value for controlling the combustion state of the engine; and f) a control value for controlling the combustion state of the engine based on the output of the control means. A combustion control device for an internal combustion engine, comprising: combustion operation means for operating parameters related to a state.