JPH04136455A - Detection of knocking and controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To detect the generation of knocking with high precision by detecting the combustion gas temperature on the basis of flame light, obtaining the appearance frequency pattern at each combustion gas temperature from the result of the above- described detection and judging knocking through the comparison with a prescribed standard pattern. CONSTITUTION:A lighting window 6 consisting of a quartz rod is installed at the top part of a combustion chamber 1 faced to the combustion chamber, and the flame light in the combustion chamber 1 is taken by an optical fiber 61 installed on the lighting window 6. The optical fiber 61 is led to transmission parts 62 at four positions, branched to each quarter clad by a branched pipe 7 midway, and optical filters 81-84 for the transmission of the light having a specific wave length are installed in the branched light passages. The light which is spectro-analyzed by optical filters 81-84 is inputted into a control unit 10 through the light-electricity conversion element 91-94, and the combustion gas temperature is detected on the basis of the taken-out flame light, and the appearance frequency pattern at each combustion gas temperature is obtained from the result of the above-described detection, and at least one between the generation of knocking and sign is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a knocking detection method and control device for internal combustion engines such as gasoline engines, and particularly to a knocking detection method and control device suitable for automobile gasoline engines. Regarding.

[Conventional technology]

Traditionally, in order to maintain internal combustion engines in optimal combustion conditions,
Various technologies are known that use various sensors such as intake flow rate sensors, ○ sensors, and combustion pressure sensors to detect various parameters that represent the actual operating state of the engine and perform closed-loop control. Various techniques have been proposed for detecting flame light in a room and using it as data representing the operating state of an engine. .

For example, as is well known, internal combustion engines have knocking, which is a unique abnormal combustion. When this knocking occurs, it not only increases the temperature of the cylinder side wall and piston end surface, damaging the engine, but also causing engine output. decreases. Therefore, in order to maintain high efficiency during operation, it is ideal to control fM to a state immediately before knocking occurs, but for this purpose, it is necessary to accurately detect the occurrence of knocking.

Therefore, Japanese Patent Laid-Open No. 57-73646 discloses a knocking detection method using flame light in a combustion chamber.

In this technique, knocking is detected using a high-frequency optical signal generated by a shock wave generated when knocking occurs.

Furthermore, in Japanese Patent Application Laid-Open No. 59-87249, flame light is captured in the combustion chamber of the engine, an optimal combustion state pattern signal is stored from the flame emission intensity, and this is compared with the combustion state pattern during operation. , to achieve optimal combustion conditions.
A combustion control device is shown that controls the air ratio (an air-fuel ratio expressed using a different definition), ignition timing, and the like.

Furthermore, we also know of a technology that collects the flame light from the combustion chamber, branches this light into multiple parts using optical fibers, separates them into different wavelengths, and measures the air ratio and temperature of the combustion gas from the separated lights. However, in this conventional technology, the air ratio is determined from the emission intensity ratio of the center wavelengths of 431 nm and 517 nm, which are generated when CH and C□ radicals in the flame are generated.On the other hand, the temperature of the combustion gas is It was determined from the visible light emitted from the surface of soot, which is a solid particle present in a flame, or from the emission intensity ratio of two different wavelengths in the near-infrared region.

[Problem to be solved by the invention]

Among the above-mentioned conventional techniques, the conventional technique disclosed in Japanese Patent Application Laid-Open No. 59-87249 uses the entire wavelength range of combustion flame light, and information on the air ratio and temperature inside the combustion chamber cannot be obtained. When abnormal combustion occurs, the cause cannot be known.

Also, Japanese Patent Publication No. 57. In the knocking detection method disclosed in Japanese Patent No. 73646, a signal when knocking occurs can be obtained, but the state immediately before knocking cannot be known. That is, when knocking occurs, it gives a shock to the engine, so as mentioned above, ideally the engine should be operated just before knocking occurs, but there is a problem in that the information necessary for this cannot be obtained.

On the other hand, in the conventional method of measuring the air ratio and temperature from the emission intensity ratio of two specific wavelengths of flame light, the measurement method is clearly specified, but it prevents optimal combustion conditions from being achieved. Combustion control methods based on elucidation of the cause have not been proposed.

An object of the present invention is to be able to detect the occurrence of knocking and its precursors from physical information contained in flame light in the combustion chamber of an internal combustion engine, and to easily determine control parameters necessary to obtain an optimal combustion state. An object of the present invention is to provide a knocking detection method and a control device for an internal combustion engine, which enable optimum combustion control to be obtained.

[Means for solving rag] In order to achieve the above purpose, the combustion gas temperature is detected based on flame light, the appearance frequency pattern for each temperature value of the combustion gas temperature is determined from the detection result, and the appearance frequency pattern is calculated for each temperature value of the combustion gas temperature. Knocking is determined by comparing the pattern with a predetermined reference pattern.Furthermore, the air ratio value is detected based on spectrum analysis of flame light, and from this detection result, each air ratio value is determined. The combustion state of the internal combustion engine is determined by determining an appearance frequency pattern and comparing this appearance frequency pattern with a predetermined reference pattern.

C effect] The appearance frequency pattern of combustion gas temperature shows a specific change when knocking or its precursor appears.

Therefore, the occurrence of knocking and its precursors can be detected with high accuracy by storing in advance the pattern at the time of occurrence of knocking or the occurrence of its precursor, and comparing it with this pattern.

Similarly, the frequency pattern of each air ratio value reflects the control parameters that are causing the air ratio fluctuations. Therefore, by storing a pattern for each control parameter in advance and comparing it with this pattern, the control parameter causing the air ratio fluctuation can be identified, and accurate combustion control becomes possible.

[Example] Hereinafter, the knocking detection method and control device for an internal combustion engine according to the present invention will be explained in detail with reference to the illustrated example.

FIG. 1 shows an embodiment in which the present invention is applied to a gasoline engine. In the figure, 1 is a combustion chamber of an internal combustion engine, 2 is a cylinder, 3 is a piston, 4 is a spark plug, and 5 is a fuel injection H#.

A lighting window 6 made of a quartz rod is provided at the top of the combustion chamber facing the combustion chamber l, and an optical fiber 61 attached to the lighting window 6 allows the flame light inside the combustion chamber 1 to be illuminated. Make it. The optical fiber 61 has a cladding diameter of 20 mm, for example.
It is made of quartz glass with a diameter of 0 μm and is made of multiple pieces bundled together. On the way, the collected light is split into four equally divided claddings by a branch tube 7, and the light is emitted from four emitting sections 6.
2, and each is emitted from there.

In the optical path of the four-branched optical fiber output section 62, there are optical filters 81, 82, 83, and 8 that transmit a specific wavelength.
4 are provided respectively.

These optical filters 81 to 84 are optical filters,
First, the optical filter 81 is a filter that selectively transmits light emitted from OH radicals, and its center wavelength is 431 nm.
m, and the optical filter 82 is C.

A filter that selectively transmits light emitted from radicals and has a center wavelength of 517 nm is used. In addition, the optical filters 83 and 84 selectively transmit a certain wavelength of thermal radiation that does not contain light emitted from radicals,
For example, the optical filter 83 has a center wavelength of 500 nm, and the optical filter 84 has a center wavelength of 800 nm.

The wavelength selection for this thermal radiation light is 500 nm.
and 800 nm, preferably 5
Any wavelength from 00 nm to around 11000 nm may be selected as long as it does not contain light emission from radicals.

In addition, when the center wavelength of an optical filter is used to separate light, a small amount of nearby wavelengths are also taken in due to the manufacturing process of the optical filter. Therefore, the required wavelength is called the center wavelength.

Next, the reason why the center wavelength of the optical filter was selected in this way is as follows. That is, it is known that in the combustion flame of hydrocarbons, such as gasoline or light oil used in internal combustion engines, light emission occurs from radicals generated during the combustion process. These radical species include OH radicals, OH radicals, and C, radicals, which exhibit strong emission intensity.

It is also known that the light emission caused by these radicals is affected by the air ratio. Among these, as a result of experiments, OH radicals have a weak dependence on the air ratio, so an optical filter was selected that selectively transmits CH, C, and radicals, which have a strong dependence.

On the other hand, since fine soot exists in the flame and the specific heat of the soot itself is small, the temperature of the soot is approximately equal to the flame temperature. The light emitted from this soot, that is, the thermal radiation, has a strong dependence on temperature. Therefore, using these wavelengths, air ratio and temperature can be measured.

The lights separated by the optical filters 81 to 84 are guided to photoelectric conversion elements 91, 92, 93 and 94, respectively, and converted into electrical signals corresponding to the intensity of the optical signals. Note that for these photoelectric conversion elements 91 to 94, for example, photomultiplier tubes, phototransistors, photodiodes, etc. are used. Moreover, when the electrical signal output from these photoelectric conversion elements is small, it is outputted via an amplifier.

Electrical signal outputs from the photoelectric conversion elements 91 to 94 are input to the control unit 10.

The control unit 1o performs various arithmetic processing necessary for engine control, generates various control signals given as a result, and transmits them to, for example, an ignition timing regulator 11, a fuel flow regulator 12, and an air flow regulator. The fuel is supplied to actuators such as the engine 13, and functions to control the operating state of the engine. The data required at this time, such as the engine rotational speed, is taken in from the crank angle detector 14.

Before explaining the operation of the embodiment shown in FIG. 1, the detection principle according to this embodiment will be explained.

First, FIG. 2 shows an example of the air ratio measurement results.

The mixture of fuel and air supplied into the combustion chamber is sent to the spark plug 4.
The gas is ignited and combustion begins, and as the combustion progresses, the gas expands and provides power to the piston. Figure 2 captures this combustion process, and shows the electrical signal output corresponding to the emission intensity of CH radicals and CI radicals in the -stroke, that is, the emission intensity, and the air ratio calculated from the ratio of the two. , it can be seen that the air ratio changes with combustion time.

Next, this air ratio is shown as the appearance frequency for each value in FIGS. 3 and 4, and the operating conditions at this time were an air ratio of 1.0 on a supply basis.

Comparing these FIGS. 3 and 4, it can be seen that the appearance frequency patterns of the air ratio are different. That is, while FIG. 3 shows a high frequency of appearance near the set air ratio of 1.0, the frequency of appearance in FIG. 4 is widely distributed.

On the other hand, when comparing the amounts of unburned carbon monoxide (GO) and hydrocarbons (HC) in the combustion exhaust gas under these operating conditions, the conditions in Figure 4 are approximately 2 times lower than those in Figure 3.
It was double that. In other words, the pattern shown in FIG. 4 occurs when combustibility is poor.

This is considered to be due to the fuel injection timing. That is, if fuel is injected while the intake valve is not fully open, it is thought that the fuel will adhere to the intake valve and change the air ratio during combustion.

If this is set as the normal injection timing, the frequency pattern of air ratios will appear concentrated around the set air ratio.

Also, looking at the variance value that indicates the variation in the frequency of appearance,
Normally, it is 9.5%, but if the injection timing is earlier or later than the proper timing (defective), it will be 18% or more.
CO and HC emissions will also increase.

Furthermore, when the fuel and air supply ratio changes, the frequency pattern of the air ratio shifts. In other words, if the supply base air ratio changes to, for example, 0.9 for some reason,
The frequency of appearance of the measured air ratio has a characteristic of peaking around 0.9. In this state, unburned gas is discharged and causes air pollution, so it is necessary to control the amount of air or fuel supplied.

Next, temperature measurement results will be explained.

Figures 5, 6, and 7 show measurement examples in which the temperature appearance frequency patterns in the -stroke are different.
Figure 5 shows the frequency of temperature appearance under normal combustion conditions, Figure 6 shows the frequency of temperature appearance when the ignition advance angle changes and knocking occurs, and Figure 7 shows the frequency of temperature appearance just before knocking occurs. Indicates frequency.

Therefore, in this way, the combustion state can be known from the temperature appearance frequency pattern. This phenomenon occurs because when knocking occurs, the temperature boundary layer on the cylinder wall is broken by shock waves.
It is thought that the temperature decreases because the heat of the flame is taken away by the cylinder, and the frequency of temperature occurrence becomes wider.

Conventionally, abnormal combustion such as knocking is detected after knocking has occurred, but the method for evaluating temperature appearance frequency patterns according to the present invention can detect combustion conditions close to the occurrence of knocking, that is, about a sign of knocking. I understand.

Therefore, according to the present invention, normal combustion can be easily maintained by detecting this temperature appearance frequency pattern and controlling the ignition timing.

Next, when we compare the variance indicating the variation in the frequency of these occurrences, we find that it is 9.5% in normal combustion and 2% in the case of knocking.
It is now 5%.

Therefore, combustion can be controlled using this dispersion as an index.

As described above, in the present invention, it has been discovered that the air ratio and temperature in the combustion chamber can be detected from flame light, and at the same time, normal combustion and over-normal combustion can be distinguished from the pattern that appears.
Control is performed using this appearance pattern to achieve an optimal combustion state.An embodiment of the present invention in this manner will be described below.

FIG. 8 is a flowchart showing the operation of one embodiment of the present invention shown in FIG. 1, which is executed by a microcomputer provided in the control unit 10. , initial values are set in processing step 801. Initial values differ for each individual engine, and include the desired temperature, air ratio, and their variance for each engine, as well as the temperature, air ratio, and their variance during actual operation, and the desired temperature. , air ratio, and the allowable error between them and their variance values. These values are determined in advance through other experiments and the like.

Next, in processing step 802, optical signals for measuring temperature and air ratio are input. The configuration of these devices, etc.
The details are explained in Figure 1.

In processing step 803, the air ratio λ and temperature T are calculated using the optical signal. Therefore, in this step, a calibration curve for calculating the temperature and air ratio from the optical signal intensity is input in advance.

After completing this step, the process is divided into two processes: one for calculating the variance of temperature and air ratio, and the other for controlling the engine using the air ratio.

First, the flow of controlling the engine using the air ratio will be explained.

First, the process proceeds to processing step 810 in which it is determined to what extent the air ratio of the engine that is actually being operated deviates from the initially set desired air ratio. Here, the degree of deviation, that is, the allowable range is initially set.

When the air ratio of the engine that is actually being operated is within the allowable range, the process moves to step 811 and the current operating process amount is maintained.

The operating process amount referred to here is a process amount that influences the air ratio, and in particular, the amount of air supplied, the amount of fuel supplied, and the like.

If the air ratio of the engine during actual operation falls outside the allowable range, the process proceeds to step 812, where the air supply amount or fuel supply amount is appropriately changed. When changing the process amount,
Since the combustion in the engine changes and therefore the light signal from the flame changes, input the light signal again and calculate the air ratio,
We will repeat the series of comparisons with the initial values. Note that even when the process amount is not changed, the air ratio of the engine during actual operation may deviate from the allowable range due to some factor, so the above-mentioned series of steps is repeated.

Next, after calculating the temperature and air ratio, in the process of calculating the variance of the temperature and air ratio, the variance value is used to determine knocking.
Performs control, etc. Therefore, first, in processing step 804, a variance value is calculated.

After calculating the temperature variance value, the process proceeds to processing step 820 in which it is determined whether the temperature variance value is greater than, 5, smaller than, or equal to the initially set temperature variance value. If they are smaller or equal, it is determined that knocking has not occurred, and the process proceeds to step 821, where operation is performed while maintaining the current operating process amount.

However, if the temperature variance value is larger than the initially set temperature variance value, the process proceeds to step 822 and is comprehensively determined based on the output values of other knock sensors not shown in FIG. Then, if it is determined that knocking is occurring, countermeasures are taken.

Normally, advance angle control is adopted as shown in processing step 823.

When the advance angle is changed, the combustion timing etc. change accordingly, and the temperature inside the engine and its dispersion value also change, so optical measurement, temperature calculation, temperature dispersion value calculation, knocking judgment, etc. The series of steps for advance angle control will be repeated.

On the other hand, after calculating the air ratio variance value in process step 820, the process proceeds to process step 830 in which it is determined whether the air ratio variance value is greater than, smaller than, or equal to the initially set air ratio variance value. If they are smaller or equal, it means that the combustion in each cycle is being operated stably, and therefore the process proceeds to step 831, where operation is performed while maintaining the current operating process amount.

However, if the dispersion value of the air ratio is larger than the initially set dispersion value of the air ratio, it means that the combustion in each cycle is unstable, and it is necessary to take countermeasures against this. Generally, if the air and fuel are not mixed sufficiently, 1
The fluctuation of the air ratio during the cycle is large, and therefore the dispersion value of the air ratio is also large. Therefore, in order to reduce the dispersion value, that is, to reduce the fluctuation in the air ratio, it is sufficient to mix the fuel and air sufficiently. One method is to change the fuel injection timing, which is the process step 83.
It is shown in 1.

Note that these above-described series of flows are repeated during engine operation.

According to this embodiment, the emission of flame from the combustion chamber of the engine is illuminated, and the air ratio and temperature in the engine, or their dispersion values, are used to determine knocking, variations in the air ratio, etc., and the desired driving performance is determined. The state has a controllable effect.

[Effects of the Invention] According to the present invention, flame light from the combustion chamber of an internal combustion engine is directly illuminated, the air ratio and temperature for each stroke are detected, and these are used as indicators for combustion control, so combustion control can be performed in real time. This not only allows for highly efficient combustion in the internal combustion engine, but also reduces the amount of unburned gas produced, resulting in excellent pollution prevention effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the knocking detection method and control device for an internal combustion engine according to the present invention, FIG. 2 is a characteristic diagram showing the relationship between CH radical and CI radical emission intensity and air ratio, and FIG. Figure 4 is a characteristic diagram showing the appearance frequency distribution of air ratio, Figures 5, 6 and 7 are characteristic diagrams showing the appearance frequency distribution of temperature, and Figure 8 is an example of the operation by the control unit. FIG. 1... Combustion chamber, 2... Cylinder, 3.
...Piston, 4...Spark plug, 5...
...Fuel injection valve, 6...Lighting window, 10...
...Control unit, 11...Ignition timingllll
# device, ]2...Fuel flow rate regulator, 13...
...Air flow rate regulator, 14...Crank angle detector, 61...Optical fiber, 81-84...
- Optical filter, 91-94...Photoelectric conversion element. Fig. 1 61, 7F 1 [18 Fig. Fig. Fig. Air north (-)

Claims (1)

[Scope of Claims] 1. Detect the combustion gas temperature based on flame light taken from the combustion chamber of the internal combustion engine, determine the appearance frequency pattern for each temperature value of the combustion gas temperature from this detection result, and calculate the appearance frequency. A method for detecting knocking in an internal combustion engine, characterized in that the method is configured to determine at least one of the occurrence of knocking and its precursor by comparing the pattern with a predetermined reference pattern. 2. The invention according to claim 1, characterized in that the comparison between the frequency of occurrence pattern and a predetermined reference pattern is a comparison of variance values representing variations in the distribution of frequency of occurrence for each temperature value of combustion gas temperature. Method for detecting knocking in internal combustion engines. 3. means for detecting combustion gas temperature based on flame light taken from a combustion chamber of an internal combustion engine; means for determining an appearance frequency pattern for each temperature value of combustion gas temperature from the detection result by the means; A means for determining at least one of the occurrence of knocking and its precursor by comparing the obtained appearance frequency pattern with a predetermined reference pattern is provided, and the ignition timing is controlled according to the determination result of this means. A control device for an internal combustion engine. 4. means for detecting an air ratio value based on spectrum analysis of flame light taken from a combustion chamber of an internal combustion engine; means for determining an appearance frequency pattern for each air ratio value from the detection results by the means; means for determining the combustion state of the internal combustion engine by comparing the appearance frequency pattern obtained by the means with a predetermined reference pattern, and the operating state of the internal combustion engine is controlled according to the determination result of this means. An internal combustion engine control device characterized by: 5. In the invention of claim 4, the means for controlling the operating state of the internal combustion engine comprises means for controlling at least one of intake flow rate, fuel supply amount, ignition timing, and fuel injection timing. An internal combustion engine control device characterized by: