JPS6017239A - Control device of combustion in internal-combustion engine - Google Patents

Abstract

PURPOSE:To sufficiently suppress the generation of NOx, by calculating the combustion temperature on the basis of light emitted at an explosion stroke in a cylinder and feedback controlling the combustion of an engine in accordance with said combustion temperature. CONSTITUTION:Light emitted from the inside of a cylinder in an engine 1 is detected by a light detecting means 11 and converted into a signal of combustion temperature by a light-temperature converting means 13. A combustion control arithmetic means outputs a control signal of combustion on the basis of the output of a crank angle detecting means 27. A combustion control means 32 controls the combustion temperature of the engine 1 on the basis of the control signal of combustion. In such way, the generation of NOx is suppressed, while drivability of the engine and its fuel comsumption can be improved.

Description

Detailed Description of the Invention (Technical Field) This description relates to a combustion control device for an internal combustion engine, and more specifically, to a combustion control device for an internal combustion engine. The present invention relates to a combustion control device for an internal combustion engine that reduces NOx by feedback controlling the combustion of the engine accordingly.

(Prior art) In general, NOx (nitrogen oxides), which are harmful components in exhaust gas, tend to be generated in large quantities as the combustion temperature of the air-fuel mixture increases. It is known that relatively lowering the combustion temperature by refluxing the fuel is effective in reducing NOx.

By the way, when performing such control, it is difficult to actually measure the temperature inside the combustion chamber and accurately grasp the conditions in which NOx is likely to be generated. The fuel ratio, exhaust gas recirculation (EGR) amount, etc. are controlled to optimal values set in advance, thereby suppressing the generation of NOx.

Examples of such conventional combustion control devices for internal combustion engines include the rECC3L engine 1979 technical manual.
(June 1978 Published by Nissan Motor Co., Ltd. 69-7
(page 6). This device suppresses the generation of NOx by recirculating a portion of the exhaust gas to the intake passage and lowering the combustion temperature. That is, an EGR passage leading from the exhaust passage to the intake passage is provided, and the EGR
The amount of EGR is controlled each time the amount of exhaust gas flowing through the passage is changed by an EGR control valve. The negative pressure that operates this EGR control valve is created by a VCM valve, and the VCM valve operates at -120, for example, based on a control signal from the control unit.
Creates a negative pressure of +nmHg to -15mm11g, applies this negative pressure to the EGR control valve to open and close the EGR passage, and controls the EGR control valve so that the EGR amount becomes the optimal amount stored in the control unit in advance. .

This allows combustion temperature to be appropriately controlled according to engine operating conditions, and in particular reduces NOx by lowering the maximum temperature during combustion.
This suppresses the occurrence of

However, in such a conventional combustion control device for an internal combustion engine, the VCM pulp and EGR control valves, which have slight variations in their individual operating characteristics, operate sequentially based on control signals from the control unit. Since the configuration was to control the amount of EGR, even if the control unit outputs a highly accurate control signal according to the operating state, the control accuracy of the amount of EGR is affected by variations in the operating characteristics of each of the valves mentioned above, and the EGR amount is
Variations occur in the amount. This variation in EGR amount is
This is especially noticeable near the beginning of the opening of the EGR control valve, and if the ignition timing is not appropriate at this time, the combustion condition of the engine will deteriorate and NOx in the exhaust will increase.
Fuel efficiency worsens. Furthermore, in controlling the EGR amount, the EGR amount is corrected for changes in intake air temperature, atmospheric pressure, humidity, etc., as well as changes in deposits and nodules attached to the combustion chamber, fuel composition, etc. However, due to these changes, exhaust emissions (exhaust harmful components) increase and fuel efficiency deteriorates.

(Purpose of the Invention) Therefore, the present invention detects the light emitted in the cylinder due to combustion, calculates the combustion temperature based on this light, and sets a target in advance according to the operating conditions based on the combustion temperature. The aim is to suppress the generation of NOx and improve drivability and fuel efficiency by controlling the engine in feedback to maintain the combustion temperature.

(Configuration of the Invention) FIG. 1 is an overall configuration diagram for clearly explaining the present invention. Light emitted from within the cylinder of the engine 1 is detected by the light detection means 11 and converted by the light temperature conversion means 13 into a temperature signal corresponding to the combustion temperature within the cylinder. The combustion control calculation means determines whether the crank angle is within a predetermined range based on the output of the crank angle detection means 27 that detects the crank angle of the engine 1,
At this time, a temperature signal is taken in and, based on the temperature signal, a combustion control signal is outputted to control the combustion temperature of the engine to a target combustion temperature that is preset according to the operating conditions. The combustion control means 32 controls the combustion temperature of the engine 1 by changing at least one of the exhaust gas recirculation amount, air-fuel ratio, and ignition timing of the engine 1 based on the combustion control signal.

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

2 to 6 are diagrams showing one embodiment of the present invention, and show an example in which the exhaust gas recirculation amount of the engine is controlled based on the combustion temperature.

In FIG. 2, ■ is the internal combustion engine main body, and the intake air passes through an air cleaner (not shown), an intake passage 3 in which a throttle valve 2 is disposed, and a drive circuit 5, which is provided in the intake passage 3 near the cylinder 4 on the way. The mixture is mixed with fuel injected from the fuel injector 6 driven by the fuel injector 6, and is supplied to the cylinder 4 as an air-fuel mixture. The air-fuel mixture in the cylinder 4 is ignited and combusted by a spark plug 9 connected to an ignition circuit 8 via a distributor 7, and then becomes exhaust gas and is discharged to the outside through an exhaust passage 10. The light emitted within the cylinder 4 due to combustion is detected by an optical fiber (light detection means) 11 (for example, one used in a pyrometer that detects light inside a blast furnace) provided on the upper side wall of the cylinder 4. The light is input to a light temperature converter (light temperature conversion means) 13 via an optical fiber cable 12. Note that the optical fiber 11 is protected by a heat-resistant protection tube 11a. The light temperature converter 13, as shown in detail in FIG.
It is composed of and. The color identification element 15 identifies the color of light transmitted from the optical fiber 11 through the optical fiber cable 12, and includes an infrared filter 17, a three primary color filter 18 consisting of a blue filter 18B, a green filter 18G, a red filter 18R, and 3nO219. , S i 0
It has a photoelectric conversion section 22 formed by a heterojunction photodiode made of 220.5i21. Then, the infrared component of the light incident through the color discrimination element 15, 5' red perforated wire film 17 is filtered, and the incident red light + # spring component is cut by the 3 primary color filter 18 and the photoelectric conversion unit 22. The three primary color components of light, red, blue, and green, are detected and a current signal having a current value corresponding to each of these components is sent to an electrode.
The power and the light temperature are output to the light temperature calculation section 16. Light temperature calculation group 1
No. 6, calculate the combustion temperature in the cylinder 4 based on the above current signal, and sample the temperature signal corresponding to the combustion temperature.
Output to the D conversion section. In FIG. 2 again, the crank angle (piston position) of the internal combustion engine 1 is measured by the crank angle sensor (
The crank angle is detected by the exhaust means) 27,
This crank angle sensor 27 is built into the distributor 7 and is used to determine the reference point of each cylinder for normal ignition timing control.
In addition to subdivision points such as every degree, cycle reference points that allow cylinder discrimination are detected, and a crank angle signal is output. On the other hand, the exhaust passage 10 and the intake passage 3 downstream of the throttle valve 2 are connected to the EGR
(, exhaust gas recirculation) is communicated with by a passage 28, and this EG
An EGR valve 29 is provided in the middle of the R passage 28 to control the passage area of the EGR passage 4 using the operating negative pressure near the throttle valve 2 and atmospheric pressure as operating pressure sources. EGR valve 2
The working negative pressure introduced into the negative pressure control valve 9 is controlled according to the valve opening time ratio (duty) of the negative pressure control valve 30, and the EGR valve 29 is controlled according to the valve opening time ratio (duty) of the negative pressure control valve 30. The smaller the valve opening time ratio, the larger the passage area of the EGR passage 28. The crank angle signal from the crank angle sensor 27 and the temperature signal from the optical temperature converter 13 are input to the microcomputer 31, and the microcomputer 31 determines the opening time of the negative pressure control valve 30 based on these signals. The passage area of the EGR passage 28 by the EGR pulp 29 is controlled by controlling the duty. The EGR passage 28, EGR valve 29, and negative pressure control valve 30 change at least one of the EGR amount, air-fuel ratio, and ignition timing of the internal combustion engine 1 based on signals from the microcomputer 31. It constitutes a combustion control means 32 that controls the combustion temperature, and in this embodiment, the combustion control means 32 changes only the EGR amount.

The microcomputer 31 includes an MPU (central processing unit) 33, a ROM (read-only memory) 34, and ■
10 (input/output signal processing device) 35, the crank angle sensor 27 and the light temperature converter 13
The signals are inputted to each signal power cylinder 1035 from. l103
Reference numeral 5 denotes an area for converting various input/output signals into signals that can be processed by the MPU 33, as well as the sample AD converter 26 (incorporating an AD converter and multiplexer) into which a temperature signal is input, and a crank angle signal. a sample command unit 36 into which is input, a control pulse generator 37 which outputs operation signals to operate various actuators (for example, negative pressure control valve 30, drive circuit 5, and ignition circuit 8) based on commands from MPU 33; have. The sample AD converter 26 AD converts the temperature signal only at a predetermined timing.
When the crank angle is in a predetermined range where the crank angle is set in advance based on the crank angle signal, for example, when the crank angle is in the range of 15° to 60° after top dead center,
The sample AD conversion unit 26 is commanded to perform AD conversion. That is, the microcomputer 31 receives the temperature signal only when the crank angle is within a predetermined range. In addition to the terminal to which the temperature signal is input, the sample AD converter 26 has terminals 38 to 41 to which various signals such as intake air amount, cooling water temperature, throttle valve opening, and exhaust temperature are input. Each of these signals is also subjected to AD conversion as necessary.

The ROM 34 has a program for controlling the MP'U 33 and optimal control values according to various operating conditions written therein, and the MP LJ 33 has a built-in RAM (read/write memory) that can be used to write various data.
Temporarily stores external data. The MPU33 executes l1 according to the program written in the ROM34.
Based on each signal input to 035, the combustion temperature in the cylinder 4 in a predetermined range of crank angles (in this case, the maximum combustion temperature is also determined) is calculated, and the combustion control signal corresponding to the combustion temperature is It is output to the control means 32. In this embodiment, the fuel injection timing, injection amount, ignition timing, etc. are also controlled by the microcomputer 31 according to the operating conditions, but these are all controlled by the combustion engine in order to satisfy the operating conditions required by the engine. The combustion state is controlled to reduce NOx, and the control of the combustion state is limited to the control of the EGR amount.

Next, the control program for the EGR 3i written in the ROM 34 can be shown in the flowchart of FIG. 4, where P, -P, in FIG. shows each step of the flowchart.

When the program starts, the crank angle θ is first set at P.
is read, and it is determined at P2 whether the crank angle θ is within a predetermined range, for example, 15°<θ<6o° after top dead center. If the crank angle θ is outside the predetermined range, the program step returns to Pl again. On the other hand, when the crank angle θ is within the above predetermined range, P calculates the combustion temperature T in the cylinder 4 within this range from several points to several tens of points based on the temperature signal, and P4 calculates the combustion temperature T calculated from these points. Determine the maximum combustion temperature T max from T. Note 1. Practically the fifth
As shown in the figure, the combustion temperature T shows a peak within the above predetermined range. Therefore, by appropriately sampling the combustion temperature T within this range, it is possible to easily and accurately obtain the maximum combustion temperature Tmaχ. can. Also,
The light temperature converter 13 converts the light inside the cylinder 4 into a color discrimination element 15.
This color identification element 15 has red, blue,
Because light is identified using the so-called three-color separation method of green,
Accurate color identification is possible and combustion temperature T is highly reliable.

Furthermore, the photoelectric conversion unit 22 that converts the three primary color components identified by the color identification element 15 into current signals has a wide response wavelength range, that is, a response range to the wavelength of light (corresponding to color).
For example, 350-1200 mμ), and the response speed is also fast.

Therefore, the combustion temperature T for short-time combustion within the cylinder 4 can be accurately measured.

Now, in the flow again, the amount of NOx generated, which is the amount of harmful components emitted by the internal combustion engine l, is calculated in P5 based on the maximum combustion temperature Tma obtained in P'4. in this case,
There is a correlation between the amount of NOx generated and the maximum combustion temperature T max as shown in FIG. 6, and the amount of NOx generated is calculated based on this correlation. Then, at P, the current NOx generation amount is set to a predetermined amount N (target component amount) according to the engine operating conditions (that is, the current operating conditions).
Determine whether the number is greater than or not.

Note that the predetermined amount is set in advance to a value that corresponds to various operating conditions of the engine (that is, satisfies the various operating conditions) and makes the amount of NOx generated at least less than the regulated amount determined by exhaust gas regulations. The value varies depending on the operating conditions. When the amount of NOx generated is greater than a predetermined amount, the amount of decrease in the opening time ratio (duty) of the negative pressure control valve 3o is calculated using Pl, and the combustion control signal corresponding to this amount of reduction is sent to the negative pressure control valve 30 using pH. Output. As a result, E
The operating negative pressure introduced into the GR pulp 29 increases,
The passage area of EGR passage 4 increases. As a result, EGR
The amount of NOx increases, the maximum combustion temperature Tma in the cylinder 4 decreases, and the amount of NOx generated becomes a predetermined amount. Therefore, N
The amount of Ox generated is suppressed. On the other hand, if it is determined in P9 that the amount of NOx generated is less than the predetermined amount, then in P9 the amount of increase in the opening time ratio of the negative pressure control valve 30 is calculated, and P. A combustion control signal corresponding to the amount of increase in the lever is output to the negative pressure control valve 30. Therefore, contrary to the case described above, the EGR amount decreases and the maximum combustion temperature Tma in the cylinder 4 increases.

At this time, the maximum combustion temperature Tmax rises to a temperature at which the amount of NOx generated reaches a predetermined amount. Therefore, an unnecessary decrease in the combustion temperature T is suppressed, and, for example, problems caused by an excessively large amount of EGR, such as combustion instability and a decrease in engine output, which are conventional, are prevented, and drivability is improved.

In this way, the maximum combustion temperature T max in the cylinder 4 is feedback-controlled so as to be maintained at a combustion temperature at which the amount of NOx generated is always a predetermined amount.

Therefore, even if there are changes in atmospheric conditions such as intake air temperature, atmospheric pressure, and humidity, or changes in deposits attached to the combustion chamber or the composition of the fuel, combustion conditions will not deteriorate and will always remain in the optimal state. This results in significant improvements in drivability and fuel efficiency. In addition, because the reliability of the calculated combustion temperature T is high, the EGR amount can be optimally controlled. Even if the amount of NOx generated is in a range where the amount of NOx generated is significantly different (for example, near the X section shown in FIG. 6), the generation of NOx can be sufficiently and accurately suppressed.

In addition, in this example, in order to reduce NOx, E
Although the GR amount is controlled, for example, the air-fuel ratio or the ignition timing may be controlled, and it goes without saying that similar effects can be obtained in that case as well.

(Effects) According to the present invention, the combustion temperature is calculated based on the light inside the cylinder emitted by combustion, and the combustion temperature of the engine is fed so that the amount of NOx generated that is determined according to the combustion temperature becomes a predetermined amount. Because it is bank controlled,
The combustion state of the engine can always be maintained appropriately. As a result, while the generation of NOx can be sufficiently suppressed,
It is possible to improve the engine's drivability and fuel efficiency.

Further, in this embodiment, since the reliability of the calculated combustion temperature is high, the exhaust gas recirculation amount of the engine can be appropriately controlled, and the generation of NOx can be sufficiently and accurately suppressed.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of the present invention, FIGS. 2 to 6 are diagrams showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram thereof, and FIG.
Figure 4 is a block diagram of the light temperature conversion means, Figure 4 is a flowchart of the program that controls the combustion control means, Figure 5 is a diagram showing the relationship between the crank angle and combustion temperature, and Figure 6 is the NOx generation. It is a figure showing the relationship between the amount and the maximum temperature of combustion. 1------ Internal combustion engine, 4.-----Cylinder, 11-----. Optical fiber (light detection means), 13--
---1 optical temperature converter (light temperature converting means), 32-1-
-・-Combustion control means. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Agagun Part

Claims (1)

[Claims] A crank angle detection means for detecting the crank angle of the engine, a light detection means for detecting light emitted in the cylinder due to combustion, and a color of the light transmitted from the light detection means is identified to correspond to the combustion temperature in the cylinder. When the crank angle is within a predetermined range based on the output of the optical temperature conversion means that outputs a temperature signal and the crank angle detection means, the temperature signal is taken in and based on the temperature signal, the combustion temperature of the engine is determined in advance according to the operating conditions. Combustion control calculation means that outputs a combustion control signal for controlling to achieve a set target combustion temperature, and combustion control that changes at least one of the exhaust gas recirculation amount, air-fuel ratio, and ignition timing of the engine based on the combustion control signal. A combustion control device for an internal combustion engine, comprising: means.