JP4233340B2 - Combustion control system and combustion control method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention controls state-related value detection means for detecting a state-related value related to the operating state of the internal combustion engine, and controls the amount of fuel supplied to the internal combustion engine based on the state-related value detected by the state-related value detection means. The present invention relates to a combustion control system and a combustion control method including control means.
[0002]
[Prior art]
A conventional combustion control system for an internal combustion engine includes various sensors (state related value detection means) for detecting, for example, the temperature, pressure, humidity and the like of air flowing through the intake passage as state related values relating to the operating state of the internal combustion engine, and the intake passage. Control means for controlling the fuel supply amount to the internal combustion engine based on the state-related values detected by the respective sensors by operating a fuel control valve capable of adjusting the fuel supply amount supplied to the air flowing through The combustion control system of the internal combustion engine maintains the optimal air / fuel ratio of the air-fuel mixture that is sucked into the combustion chamber and combusted to obtain a stable and highly efficient combustion state. can do.
[0003]
Many of the commonly used internal combustion engines have various conditions such as an optimal air-fuel ratio set on the assumption that the amount of heat generated by the fuel supplied to the internal combustion engine is constant.
In other words, in an internal combustion engine equipped with the conventional combustion control system as described above, if fuel with a non-constant heat generation is supplied, there is a risk of a decrease in efficiency due to knocking or misfire, deterioration of exhaust gas properties, and the like.
[0004]
In view of this, a conventional combustion control system for an internal combustion engine has been proposed in which the air-fuel ratio is feedforward controlled based on the changing tendency of the combustion chemical equivalent value of the fuel (see, for example, Patent Document 1). Such a combustion control system is assumed to supply fuel such as biogas or off-gas in an internal combustion engine, and even if the combustion chemical equivalent value of the fuel changes, based on the change tendency of the combustion chemical equivalent value. In order to maintain a preferable combustion state, the amount of fuel supplied to the air flowing through the intake passage is controlled and the air-fuel ratio is adjusted to the optimum air-fuel ratio suitable for the fuel.
The combustion control system disclosed in Patent Document 1 takes out a part of the fuel supplied to the internal combustion engine, mixes the taken-out fuel with a predetermined amount of air, and actually burns it. By detecting the oxygen concentration of the exhaust gas generated, the combustion chemical equivalent value of the fuel is calculated from the oxygen concentration, and based on the calculated combustion chemical equivalent value, the direct fuel supply amount and the like are predicted above. It is configured to feed-forward control to those suitable for.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-221099
[Problems to be solved by the invention]
However, in the combustion control system disclosed in Patent Document 1, in order to recognize the combustion chemical equivalent value of the fuel itself, a combustion device for combusting the extracted fuel is necessary, and the combustion control system is complicated and expensive. Become.
In addition, the combustion control system derives the optimum fuel supply amount from the recognized combustion chemical equivalent value by using the correlation between the combustion chemical equivalent value stored in advance and the optimum fuel supply amount, and supplies fuel. It specializes in internal combustion engines that control the amount of fuel and the properties of the fuel are not stable. Therefore, when remodeling an internal combustion engine based on the assumption that the properties of the conventional fuel are stable so that the properties of the fuel are unstable, the control unit itself as a combustion control system must be installed. Significant changes such as replacement are required.
[0007]
Accordingly, in the present invention, in view of the above circumstances, the fuel property is unstable only by making a relatively small change to the internal combustion engine on the premise that the fuel property is stable. In addition, an object of the present invention is to realize a combustion control system capable of maintaining a stable combustion state.
[0008]
[Means for Solving the Problems]
In order to achieve this object, a first characteristic configuration of a combustion control system for an internal combustion engine according to the present invention includes state-related value detection means for detecting a state-related value related to the operating state of the internal combustion engine,
A combustion control system comprising: control means for controlling a fuel supply amount to the internal combustion engine based on the state related value detected by the state related value detection means;
A calorific value related value detecting means for detecting a calorific value related value related to the calorific value of the fuel supplied to the internal combustion engine;
A correction unit that corrects the state-related value detected by the state-related value detection unit based on the calorific value-related value detected by the calorific value-related value detection unit, and inputs the correction value to the control unit ;
As one of the state related value detection means, an air specific heat related value detection means for detecting an air specific heat related value related to a specific heat of air supplied to the internal combustion engine as the state related value,
The correction means corrects the air specific heat related value detected by the air specific heat related value detection means based on the heat generation related value detected by the heat generation related value detection means, and inputs the correction to the control means. And
The control means is based on the specific heat of air recognized from the air specific heat related value corrected by the correction means, and the density of air recognized from a plurality of the state related values other than the air specific heat related value, This is a means for controlling the amount of fuel supplied to the internal combustion engine.
[0009]
Further, a characteristic configuration of a combustion control method for an internal combustion engine according to the present invention for achieving this object is to detect a state related value related to an operating state of the internal combustion engine, and based on the detected state related value, the internal combustion engine A combustion control method for an internal combustion engine for controlling a fuel supply amount to
A heat value related value related to the heat value of the fuel supplied to the internal combustion engine is detected, and an air specific heat related value related to the specific heat of the air supplied to the internal combustion engine as one of the detected state related values, Air corrected based on the detected value related to heat generation, and air recognized from a plurality of state related values other than the specific heat of air recognized from the corrected air specific heat related value and the air specific heat related value The fuel supply amount is controlled based on the density of the fuel.
[0010]
That is, according to the combustion control system and combustion control method for an internal combustion engine having the first characteristic configuration, the state-related value output from the state-related value detection means is once taken into the correction means and the taken-in The state related value is corrected based on the heat generation amount related value of the fuel detected by the heat generation amount related value detection means, and the corrected state related value is input to the control means. Since the fuel supply amount is controlled based on the input state-related value after correction, even when the heat generation amount of the fuel is unstable, the fuel supply amount indicates the heat generation of the fuel indicated by the heat generation amount related value. By controlling the amount suitable for the amount, it is possible to maintain a stable combustion state and to prevent a decrease in efficiency, deterioration of exhaust gas properties, and the like.
[0011]
And this combustion control system of an internal combustion engine has the said calorific value related value detection means with respect to the combustion control system which performs combustion control by the said at least 1 state related value detection means and the said control means which consists of a control unit. An arithmetic processing device or the like that functions as a correction unit connected to the control unit can be realized only by being interposed between a certain state-related value detection unit and the control unit.
In an internal combustion engine, since the specific heat of the air taken into the combustion chamber affects the temperature rise state in the combustion chamber, that is, the combustion state, preferably a humidity sensor that detects the humidity of the air as the value related to the air specific heat It is preferable that the air specific heat related value detecting means such as the above is provided, and the control means controls the fuel supply amount based on the air specific heat related value to stabilize the combustion state in the combustion chamber.
Further, in the internal combustion engine that controls the fuel supply amount based on the air specific heat related value as described above, the heat value related value of the fuel that affects the combustion state in the combustion chamber as well as the air specific heat related value is expressed as the air specific heat related value. By controlling the fuel supply amount based on the air specific heat related value corrected by the converted calorific value related value, the specific heat of the air is unstable and can be easily converted into a specific heat related value. Even when the calorific value of the fuel is unstable, the combustion state in the combustion chamber can be stabilized.
[0012]
According to a second characteristic configuration of the combustion control system for an internal combustion engine according to the present invention, in addition to the first characteristic configuration, the calorific value related value detection means uses the sonic velocity or heat conduction in the fuel as the calorific value related value. It is a means for detecting the degree.
[0013]
That is, according to the combustion control system of the internal combustion engine of the second characteristic configuration, the heat generation amount related value detection means measures the speed of sound or the thermal conductivity in the fuel having a correlation with the heat generation amount of the fuel. As a simple and inexpensive configuration, the measured sound speed or thermal conductivity can be detected as the calorific value related value.
[0017]
Furthermore, according to the combustion control system for an internal combustion engine according to the present invention, it is not a fuel with a stable calorific value such as ordinary gasoline, and the calorific value is unstable because the composition is not strictly adjusted. Natural gas-based city gas, or liquefied petroleum gas (LPG) in which the ratio of propane and butane supplied from a cylinder changes due to the difference in specific gravity and the calorific value may become unstable For example, even if a gaseous fuel that consists of a plurality of hydrocarbons and the ratio of which may change the calorific value is used, the fuel supply amount is corrected based on the value related to the calorific value of the fuel and is supplied by the state value. Can be controlled to keep the fuel state stable.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a combustion control system for an internal combustion engine according to the present invention will be described with reference to the drawings.
[0019]
An engine 1 as an internal combustion engine shown in FIG. 1 includes fuel from an intake passage 3 into a combustion chamber 2 defined by an inner surface of a cylinder 4 and a top surface of a piston 5 accommodated in the cylinder 4 so as to be movable backward. An air-fuel mixture with air is sucked, and the sucked air-fuel mixture is combusted and expanded in the combustion chamber 2 to push down the piston to obtain shaft power.
[0020]
In addition, the intake passage 3 of the engine 1 is provided with a mixer 6 that supplies a fuel that is a natural gas city gas to the air flowing through the intake passage 3 to form an air-fuel mixture.
[0021]
The fuel is first made low pressure by the governor 10 and supplied to the fuel supply path 7, and then supplied to the mixer 6 via the fuel supply path 8 communicating with the fuel supply path 7.
The fuel supply path 8 is provided with a fuel control valve 11 that can adjust the flow rate of fuel supplied to the mixer 6 through the fuel supply path 8.
[0022]
Further, on the upstream side of the mixer 6 in the intake passage 3 of the engine 1, as state-related value detection means for detecting a state-related value related to the operating state of the engine 1, the temperature of air is detected and temperature data T related to that temperature is output. A temperature sensor 23 that detects the pressure of the air and outputs pressure data P relating to the pressure, and a humidity sensor 32 that detects the humidity of the air and outputs humidity data Hu relating to the humidity.
[0023]
A main control unit 20 (hereinafter abbreviated as MCU 20) provided as a combustion control system of the engine 1 performs various arithmetic processes based on a predetermined input signal and outputs a predetermined output signal based on the calculation result. Various controls such as combustion control of the engine 1 are performed by a control means 21 or the like that is configured by a computer and functions by the MCU 20 executing a predetermined program. Therefore, various data T, P, and Hu related to the temperature, pressure, and humidity of the air as the state-related values detected by the sensors 23, 24, and 32 are directly or indirectly input to the MCU 20, and are controlled by the control means 21. Then, based on these input data, the control amount data relating to the valve opening degree of the fuel control valve 11 so that the fuel supply amount supplied to the mixer 6 is optimal with respect to the state-related value of the engine 1. G is derived by arithmetic processing. Then, the MCU 20 outputs the control amount data G derived by arithmetic processing by the control means 21 to the fuel control valve 11 side, so that the valve opening degree of the fuel control valve 11 is set based on the control amount data G. Then, the amount of fuel supplied to the air, that is, the air-fuel ratio of the air-fuel mixture taken into the combustion chamber 2 is controlled. That is, if the control amount data G increases, the fuel supply amount to the mixer 6 increases. Conversely, if the control amount data G decreases, the fuel control amount to the mixer 6 decreases.
[0024]
On the downstream side of the governor 10 of the fuel supply passage 7 of the engine 1, a calorific value related value related to the calorific value of the fuel supplied to the mixer 6 is detected, and calorific value data Cal indicating the calorific value related value is output. A total 33 (an example of a calorific value related value detecting means) is provided.
[0025]
Specifically, the calorimeter 33 is configured to detect a sound speed or thermal conductivity in the fuel having a correlation with the calorific value of the fuel as the calorific value related value.
[0026]
The SCU 30 provided in the engine 1 receives the calorific value data Cal output from the calorimeter 33 and the humidity data Hu output from the humidity sensor 32, and performs various arithmetic processes based on the input data. The computer is configured to output a predetermined output signal related to the calculation result to the MCU 20 side.
[0027]
Specifically, in the correction means 31 that functions when the SCU 30 executes a predetermined program, the humidity data Hu relating to the humidity of the air detected by the humidity sensor 32 is based on the calorific value data Cal output from the heat quantity system 33. The corrected humidity data Hu ′ is output to the MCU 20 side.
[0028]
That is, the combustion control system of the engine 1 has a calorimeter 33 for the engine 1 having the MCU 20 that directly inputs the humidity data Hu, the temperature data T, and the pressure data P to the MCU 20 to control the fuel control amount. While being installed, it is configured by a simple modification such as interposing the SCU 30 between the humidity sensor 30 and the MCU 20.
[0029]
Details of each arithmetic processing in the MCU 20 and SCU 30 described so far will be described based on the block diagram of FIG.
[0030]
The humidity data Hu related to the humidity of the air output from the humidity sensor 32 and the calorific value data Cal related to the calorific value of the fuel output from the calorimeter 33 are input to the SCU 30 and used for the correction calculation processing 51 in the correction means 31. Is done.
[0031]
That is, the correction means 51 substitutes the humidity data Hu and the calorific value data Cal into the following equation 1 to obtain corrected humidity data Hu ′.
[0032]
[Expression 1]
Hu '= Hu-P (Cal)
[0033]
In other words, in the equation shown in Equation 1, the term P (Cal) into which the calorific value data Cal is substituted converts the variation from the standard of the calorific data Cal into the variation of the humidity data Hu related to the specific heat of the air. For example, P (Cal) = a (Cal−b) (a and b are constants obtained from engine tests). Therefore, an increase in the calorie data Cal is treated as a decrease in the specific heat of air, and conversely, a decrease in the calorie data Cal is treated as an increase in the specific heat of air.
[0034]
Further, in the correction processing 51, the corrected humidity data Hu ′ is output after being delayed by the time delay in consideration of the time delay until the fuel flowing through the calorimeter 33 reaches the mixer 6. .
[0035]
Next, the corrected humidity data Hu ′ corrected by the correction processing 51 includes temperature data T related to the air temperature output from the temperature sensor 23 and pressure data P related to the air pressure output from the pressure sensor 24. At the same time, it is input to the MCU 20 and used for the control amount calculation processing 52 in the control means 21.
[0036]
That is, the control means 21 substitutes the corrected humidity data Hu ′, the temperature data T, and the pressure data P into the following equation (2) to obtain the valve opening of the fuel control valve 11, that is, Control amount data G relating to the fuel supply amount is obtained.
[0037]
[Expression 2]
G = Q (Hu ′) + R (T, P)
[0038]
In the equation (2), the term Q (Hu ′) into which the corrected humidity data Hu ′ is substituted is the amount of change between the specific heat of the air recognized from the air humidity and the fuel supply to be changed. This is an expression showing a correlation with the control amount data G relating to the amount, and can be, for example, Q (Hu ′) = α · Hu ′ (α is a constant obtained from an engine test). Therefore, the control amount data G related to the fuel supply amount is increased when the humidity data Hu ′ related to the specific heat of the air is increased, and conversely, the control amount data related to the fuel supply amount is decreased when the humidity data Hu ′ is decreased. G is decreased.
[0039]
Further, in the equation shown in the above equation 2, the term R (T, P) into which the temperature data T and the pressure data P are substituted is the amount of change in the air density recognized from the air temperature and pressure, and the change It is an expression showing the correlation with the control amount data G relating to the fuel supply amount to be changed, for example, R (T, P) = β · T + γ · P (β and γ are constants obtained from engine tests). it can. Therefore, for the increase in the temperature data T related to the temperature of the air, the control amount data G related to the fuel supply amount is decreased in consideration of the decrease in the air density due to the temperature increase. Therefore, the control amount data G is increased. Further, for the increase in the pressure data P related to the air pressure, the control amount data G related to the fuel supply amount is increased in consideration of the increase in the air density due to the pressure increase. Therefore, the control amount data G is decreased.
[0040]
Then, the control means 21 outputs the control amount data G obtained by the control amount calculation processing 52 as described above to the fuel control valve 11, and sets the fuel supply amount to the mixer 6 with respect to the humidity, temperature and pressure of the air. Therefore, the air / fuel ratio can be controlled appropriately to maintain the optimum air / fuel ratio.
[0041]
Next, in order to confirm the effect of the combustion control system of the engine 1 according to the present invention, in the case of changing the heating value of the fuel supplied from 10900kcal / Nm ³ about to about 10500kcal / Nm ^3, the present invention and the conventional The power generation efficiency by the shaft power of the engine 1 will be measured and the result will be described.
As a result, in a conventional engine combustion control system, that is, a control system in which the humidity data Hu, temperature data T, and pressure data P are directly input to the MCU 20 to control the fuel control amount, the power generation efficiency is reduced from 37.2%. While the fuel control system of the engine 1 according to the present invention decreased by 2.8 points to 34.4%, it decreased by only 0.2 points from 36.9% to 36.7%. Even if the calorific value of the fuel changes, a stable fuel state can be obtained, and a decrease in efficiency and deterioration of exhaust gas properties can be prevented.
[0042]
[Another embodiment]
Next, another embodiment of the present invention will be described.
<1> In the above embodiment, natural gas-based city gas that is predicted to have a particularly large composition change is used as the fuel. However, as the fuel, hydrocarbon-based gas fuel other than city gas, or gasoline, light oil, heavy oil Fuels such as alcohol and hydrogen can be used.
[0043]
<2> In the above embodiment, the control means 21 is configured to output the operation amount data to the fuel control valve 11 provided in the fuel supply path 8 communicating with the mixer 11 to control the fuel supply amount. Separately, the fuel supply passage 8 is bypassed and opened to the intake passage 3, and normally a fuel control valve 12 provided in the fuel supply passage 9 for additionally supplying fuel when the engine is started or when the load is suddenly increased. In addition, the operation amount data may be output to control the fuel supply amount.
[0044]
<3> In the above embodiment, the MCU 20 functioning as the control unit 21 and the SCU 30 functioning as the correction unit 31 are configured as separate computers, but one computer functions as the control unit 21 and the correction unit 31. It does n’t matter.
[0045]
<4> The present invention is not particularly limited to the combustion mode of the engine, and can be applied to a spark ignition type engine or a compression ignition type engine.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an engine combustion control system. FIG. 2 is a block diagram of combustion control processing.
1: Engine (internal combustion engine)
2: Combustion chamber 3: Intake passages 7, 8, 9: Fuel supply passage 10: Governor 11, 12: Fuel control valve 20: Main control unit (MCU)
21: Control means 23: Temperature sensor (state-related value detection means)
24: Pressure sensor (state-related value detection means)
30: Sub-control unit (SCU)
31: Correction means 32: Humidity sensor (state related value detection means)
33: Calorimeter (heating value related value detection means)

Claims (5)

State-related value detection means for detecting a state-related value related to the operating state of the internal combustion engine;
A combustion control system comprising: control means for controlling a fuel supply amount to the internal combustion engine based on the state related value detected by the state related value detection means;
A calorific value related value detecting means for detecting a calorific value related value related to the calorific value of the fuel supplied to the internal combustion engine;
A correction unit that corrects the state-related value detected by the state-related value detection unit based on the calorific value-related value detected by the calorific value-related value detection unit, and inputs the correction value to the control unit;
As one of the state related value detection means, an air specific heat related value detection means for detecting an air specific heat related value related to a specific heat of air supplied to the internal combustion engine as the state related value,
The correction means corrects the air specific heat related value detected by the air specific heat related value detection means based on the heat generation related value detected by the heat generation related value detection means, and inputs the correction to the control means. And
The control means is based on the specific heat of air recognized from the air specific heat related value corrected by the correction means, and the density of air recognized from a plurality of the state related values other than the air specific heat related value, A combustion control system for an internal combustion engine, which is means for controlling the amount of fuel supplied to the internal combustion engine .   The combustion control system for an internal combustion engine according to claim 1, wherein the heat generation amount related value detection means is means for detecting a sonic speed or thermal conductivity in the fuel as the heat generation amount related value. The combustion control system for an internal combustion engine according to claim 1 or 2, wherein the air specific heat related value detection means is a humidity sensor that detects the humidity of the air as the air specific heat related value. The combustion control system for an internal combustion engine according to any one of claims 1 to 3, wherein the fuel is a hydrocarbon-based gaseous fuel. A combustion control method for an internal combustion engine that detects a state related value related to an operating state of the internal combustion engine and controls a fuel supply amount to the internal combustion engine based on the detected state related value,
A heat value related value related to the heat value of the fuel supplied to the internal combustion engine is detected, and an air specific heat related value related to the specific heat of the air supplied to the internal combustion engine as one of the detected state related values, Air corrected based on the detected value related to heat generation, and air recognized from a plurality of state related values other than the specific heat of air recognized from the corrected air specific heat related value and the air specific heat related value A combustion control method for an internal combustion engine, wherein the fuel supply amount is controlled based on the density of the engine.

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