JP2009185793A - Air excessive ratio management method and device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an exhaust gas property even in an excessive response of easily deteriorating the exhaust gas property, by highly accurately performing λ control, by successively calculating a gas constant used for calculating an air supply quantity, from a measuring result of the air excessive ratio λ and various parameters of a pre-cycle. <P>SOLUTION: This method is provided for controlling the air excessive ratio λ of an engine 1 constituted so as to recirculate a part of exhaust gas to the intake side of a cylinder, and calculates the air excessive ratio λ of the pre-cycle from a specification, an operation condition, the suction air volume and a fuel flow rate Gf of the engine 1, and calculates the gas constant R of mixed gas (a+e<SB>1</SB>) including recirculation gas e<SB>1</SB>sucked in the cylinder 2 from the air excessive ratio, and calculates the air excessive ratio λ of a present cycle by using the gas constant R, and makes a control so as to approach the air excessive ratio λ of the present cycle to the target air excessive ratio introduced from a preset target air excessive ratio map M. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the EGR type engine in which a part of the exhaust gas discharged from the engine is recirculated to the intake side of the cylinder, the amount of recirculated gas is particularly improved by increasing the accuracy of excess air ratio control. The present invention relates to a method and an apparatus for managing an excess air ratio that can maintain a low emission amount of smoke, PM, NOx, etc. even during an excessive response in which operating conditions such as a sudden change occur, and that do not deteriorate the environment.

With the recent trend of tightening exhaust gas regulations for engines, increasing the accuracy of excess air ratio control has become an important development issue. In an EGR engine, the amount of harmful components emitted increases during an excessive response in which the amount of recirculated exhaust gas changes suddenly.
To control the excess air ratio of the engine (lambda), it is necessary to monitor the air excess ratio in real time, in the method, the excess air ratio mainly measure the O ₂ in the exhaust gas at the O ₂ sensor And a method of estimating the excess air ratio based on the operating condition on the supply side of the cylinder.

In diesel engines and lean gas engines, the method of estimating the excess air ratio based on the latter air supply condition is the mainstream due to the reliability problem of the O ₂ sensor and the like.
Japanese Patent Laid-Open No. 10-318047 discloses the latter method.
The method disclosed in Patent Document 1 calculates an actual excess air rate based on the intake air amount, the fuel injection amount, and the recirculated exhaust gas amount, and sets a target excess air rate according to the operating state. The opening degree of the recirculation gas control valve is controlled so that the target excess air ratio and the actual excess air ratio coincide with each other.

  Conventionally, when estimating the excess air ratio, first, calculate from engine specifications (cylinder stroke volume, deposition efficiency), operating conditions (mainly rotational speed), gas constant, supply air temperature, and supply air pressure. The amount of air supplied to the cylinder is calculated from the air supply density at that time, the air excess rate is estimated from the air supply amount and the fuel injection amount, and the air excess rate is calculated based on the estimated air excess rate. To control. Here, the value of air is generally used as the gas constant used to calculate the supply air density.

Japanese Patent Laid-Open No. 10-318047

  However, in an engine to which an exhaust gas recirculation system is applied or a pre-supercharger premixing type gas engine, the supply air is a mixture of air, recirculation gas and fuel gas, and the gas constant is determined by these component gases. Varies depending on the mixing ratio.

  For this reason, when the air supply amount and the excess air ratio are calculated using the gas constant of air, there is a divergence between the actual supply air amount and the excess air ratio and the calculated supply air amount and the excess air ratio. As a result, the excess air ratio may not be appropriate and harmful components contained in the exhaust gas may not be reduced. The higher the engine load, the greater the amount of recirculated gas. Therefore, the difference between the actual air supply amount and excess air ratio and the calculated air supply amount and excess air ratio increases.

  In view of the problems of the prior art, the present invention sequentially controls the excess air ratio by calculating the gas constant used for calculating the supply air amount from the excess air ratio calculated in the previous cycle and the measurement results of various parameters. The purpose is to improve the accuracy in accordance with the actual situation, thereby preventing the deterioration of the exhaust gas property even at the time of an excessive response in which the exhaust gas property is likely to deteriorate.

In order to achieve the above object, the engine excess air ratio management method of the present invention comprises:
In a method for controlling an excess air ratio of an engine configured to recirculate a part of exhaust gas to an intake side of a cylinder,
The excess air ratio of the previous cycle is calculated from the engine specifications, operating conditions, intake air amount, and fuel flow rate, and the gas constant of the intake gas mixture including recirculation gas sucked into the cylinder is calculated from the excess air ratio. ,
The excess air ratio of the current cycle is calculated using the gas constant, and the excess air ratio of the current cycle is controlled to approach the target excess air ratio derived from a preset target excess air ratio map. is there.

  When calculating the density of the supply air from the gas constant, temperature and pressure of the intake air sucked into the cylinder, the gas constant used for the calculation of the supply air density is a gas constant different from air in the case of an EGR engine, If the gas constant of air is used, it is expected to affect the calculation of the air supply amount. Therefore, in the method of the present invention, the gas constant is calculated from the excess air ratio calculated in the previous cycle, and the excess air ratio in the current cycle is calculated using this gas constant.

In this way, by using the gas constant calculated in the previous cycle for calculating the supply amount of the next cycle, the estimation accuracy of the excess air ratio is improved, and even when the EGR method is applied, harmful substances in the exhaust gas are removed. Can be reduced.
For this reason, even when the engine operating conditions change suddenly, such as when the load fluctuates, the air excess rate can be estimated in real time with high accuracy, and harmful components contained in the exhaust gas can be reduced during an excessive response.

  In the method of the present invention, as a specific operation for controlling the excess air ratio, the opening degree of the throttle valve provided in the intake air passage or the flow rate adjusting valve provided in the recirculation gas passage may be controlled.

  In the method of the present invention, as a method for calculating the excess air ratio in the previous cycle, the flow rate of the mixed gas is determined from the engine specifications and operating conditions, and the gas constant, temperature and pressure of the mixed gas sucked into the cylinder. And calculating a recirculation gas amount from the intake mixed gas flow rate and the intake air amount sucked from the intake air passage, and calculating the intake air amount and the air amount in the recirculation gas calculated from the fuel supply amount. From the above, it is preferable to calculate the excess air ratio of the previous cycle.

  Thereby, the gas constant of the recirculation gas of the previous cycle can be calculated from the excess air ratio of the previous cycle, and the gas constant of the mixed gas sucked into the cylinder can be calculated from the gas constant. Thus, by using the gas constant of the mixed gas calculated by sequential calculation from the excess air ratio of the previous cycle, the cylinder air supply amount in the current cycle that matches the actual operating state can be calculated.

In addition, the engine excess air ratio management device of the present invention for carrying out the method of the present invention comprises:
In the apparatus for controlling the excess air ratio of the engine configured to recirculate a part of the exhaust gas discharged from the engine to the intake side of the cylinder,
A means for calculating the excess air ratio of the previous cycle from the engine specifications, operating conditions, intake air amount, fuel flow rate, and calculating the gas constant of the intake gas mixture including the recirculation gas sucked into the cylinder from the excess air ratio Means for calculating the excess air ratio of the current cycle using the gas constant,
The excess air ratio of the current cycle is controlled to approach the target excess air ratio derived from a preset target excess air ratio map.

  In the device of the present invention, as a specific means for controlling the excess air ratio, a throttle valve provided in the intake air passage or a flow rate adjustment provided in a recirculation gas passage for returning a part of the exhaust gas to the cylinder A valve may be provided, and the air-fuel ratio may be controlled by controlling the opening of the throttle valve or the flow rate adjusting valve.

  According to the method of the present invention, in a method for controlling the excess air ratio of an engine configured to recirculate a part of exhaust gas to the intake side of a cylinder, the engine specifications, operating conditions, intake air amount, and fuel flow rate are used. Calculate the excess air ratio of the previous cycle, calculate the gas constant of the intake gas mixture including the recirculation gas sucked into the cylinder from the excess air ratio, and calculate the excess air ratio of the current cycle using the gas constant At the same time, the excess air ratio of the current cycle is controlled to approach the target excess air ratio derived from the preset target excess air ratio map, and the gas constant calculated in the previous cycle is used to calculate the supply amount of the next cycle. By using it, the estimation accuracy of the excess air ratio is improved, and even when the EGR method is applied, harmful substances in the exhaust gas can be reduced.

  For this reason, even when the engine operating conditions change suddenly, it is possible to estimate the excess air ratio with high accuracy in real time, and to improve the exhaust gas properties at the time of excessive response.

  According to the device of the present invention, in the device for controlling the excess air ratio of the engine configured to recirculate a part of the exhaust gas discharged from the engine to the intake side of the cylinder, Means for calculating the excess air ratio of the previous cycle from the intake air amount and the fuel flow rate; means for calculating the gas constant of the intake gas mixture including recirculation gas sucked into the cylinder from the excess air ratio; and the gas constant Means for calculating the excess air ratio of the current cycle using the control, and by controlling the excess air ratio of the current cycle to approach the target excess air ratio derived from the preset target excess air ratio map, The same effect as the effect by the method of the present invention can be obtained.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the present invention to that only, unless otherwise specified.

  An embodiment according to the present invention will be described with reference to FIGS. FIG. 1 is a system diagram of an excess air ratio management device for a gas engine according to the present embodiment. In FIG. 1, an intake air passage 3 and an exhaust passage 4 are connected to the top of a cylinder 2 constituting the gas engine 1. By the piston 5 sliding in the cylinder 2, the intake air a passes through the intake air passage 3 and is sucked into the cylinder 2 through the intake valve 15, and the exhaust gas e is discharged from the cylinder 2 through the exhaust valve 16. It is discharged and discharged to the outside through the exhaust passage 4.

  The piston 5 is connected to the drive motor 8 via the piston rod 6 and the crankshaft 7 and is driven by the drive force of the drive motor 8. A supercharger 11 is disposed across the intake air passage 3 and the exhaust passage 4. One compressor blade 11a constituting the supercharger 11 is provided in the air suction passage 3, the other turbine blade 11b is provided in the exhaust passage 4, and the compressor blade 11a and the turbine blade 11b are connected by a shaft 11c. . The turbine 11b is rotated by the exhaust gas e flowing through the exhaust passage 4, and supercharges the intake air a into the cylinder 2 by the compressor blade 11b interlocked with the turbine blade 11b.

The intake air passage 3 is provided with an air supply throttle valve 12, and the intake air passage 3 and the exhaust passage 4 are connected by an EGR gas passage 13. An EGR valve 14 is interposed in the EGR gas passage 13. By returning a part of the exhaust gas e to the intake air passage 3 via the EGR gas passage 13, the combustion temperature and pressure can be lowered, and the amount of NOx discharged in the exhaust gas can be reduced. In this way, the cylinder 2 sucks the mixed gas (a + e ₁ ) composed of the intake air a and the EGR gas (recirculation gas) e ₁ .

  An airflow sensor 21 for detecting the intake air amount is attached to the intake air passage 3 upstream of the supercharger 11, and the temperature of the intake air a is detected in the intake air passage 3 downstream of the supercharger 11. A temperature sensor 22 for detecting the pressure and a pressure sensor 23 for detecting the pressure of the intake air a are attached. Detection signals of these sensors 21 to 23 are transmitted to the λ estimation means 30. The drive motor 8 is provided with a detector 24 that detects the rotational speed of the drive motor 8, and the detection signal is transmitted to the λ estimation means 30.

  In addition to these detection signals, the λ estimation means 30 includes a separately measured fuel gas flow rate Gf, a volumetric efficiency value under the current operating condition derived from the volumetric efficiency map V, and an air gas constant as an initial value. R is entered.

In the past, the value of air was used as the gas constant R of the supply air. However, as shown in FIG. 2, the gas constant R of the mixed gas (a + e ₁ ) actually varies depending on the EGR rate and the EGR rate. It rises with increasing. Therefore, in the region of the high EGR rate, the estimation accuracy of the excess air ratio λ decreases, and appropriate excess air ratio control cannot be performed.

  FIG. 3 shows the configuration of the λ estimation means 30. Based on FIG. 3, the configuration of the λ estimation means 30 will be described. 3, first, the specifications of the gas engine 1 (the process volume of the cylinder 2, the volumetric efficiency value under the current operating conditions derived from the volumetric efficiency map V, etc.), the gas constant of air as the initial value of the gas constant R, and Operating conditions (such as the number of revolutions) are input to the intake air-fuel mixture calculating means 31. From these input parameters, the intake air amount calculating means 31 calculates the mixed intake air amount sucked into the cylinder 2.

Next, the mixed intake air amount calculated by the intake air mixture amount calculating unit 31 and the intake air amount detected by the air flow sensor 21 are input to the EGR amount calculating unit 32, and the EGR amount calculating unit is calculated from these input values. At 32, the amount of EGR gas is calculated. The EGR gas amount calculated by the EGR amount calculating means 32 is input to the air amount calculating means 33 in the EGR gas, where the air amount in the EGR gas is calculated. The amount of air in the EGR gas calculated here, the amount of intake air detected by the air flow sensor 21, and the separately measured fuel flow rate G _f are input to the λ calculating unit 34, and the air calculated by the λ calculating unit 34 The excess rate λ is calculated.

The excess air ratio λ _n calculated by the λ calculating means 34 is compared with the target air / fuel ratio λ ₀ optimum for the current operating condition derived from the target air / fuel ratio map M created in advance by the comparing means 35, and the difference Δλ is sent to the λ controller 25. The λ control device 25 controls the air supply throttle valve 12 and the EGR valve 14 so that the difference Δλ becomes zero, that is, the excess air ratio λ _n approaches the target excess air ratio λ ₀ .

The excess air ratio λn calculated by the λ calculating unit 34 is fed back to the air amount calculating unit 33 in the EGR gas and used for calculating the air amount in the EGR gas in the next cycle (that is, the current cycle). Further, the air-fuel ratio λn is input to the gas constant calculating means 36 for EGR gas. Here, the gas constant R of the EGR gas of the previous cycle is calculated. The gas constant R of the EGR gas calculated here is input to the gas constant calculating means 37 for the supply air, and the gas constant R of the mixed gas (a + e ₁ ) sucked into the cylinder 2 in the previous cycle is calculated.

The gas constant R of the mixed gas (a + e ₁ ) calculated by the supply gas constant calculating means 37 is input to the intake air mixture amount calculating means 31 and replaces the previously input air gas constant R. In the current cycle, the excess air ratio λ _n is calculated from the replaced gas constant R, and the calculated excess air ratio λ _n is controlled so as to approach the target excess air ratio λ _{0 under the} current operating conditions. Thus, in each cycle of the engine 1, the excess air ratio lambda _n of the present cycle of the gas constant on the basis of the successively calculated mixture gas from the excess air ratio lambda _n of the previous cycle (a + e ₁₎ is calculated.

Next, a method for calculating the gas constant R of the mixed gas (a + e ₁ ) will be described. In this case, the following conditions were imposed to simplify the calculation method. That is,
・ The fuel is HC compound (that is, it does not include 0 and S).
-Complete combustion in the engine 1 That is, no unburned components (CO, HC) are generated.
・ No trace amount of NOx etc. shall be generated.

The supply air sucked into the cylinder 2 is a mixed gas (a + e ₁ ) in which the air a and the EGR gas e ₁ are mixed at a certain ratio. FIG. 4A shows a schematic diagram thereof. In FIG. 4A, Ga represents the amount of contained air (kg / s), and Gegr represents the amount of contained exhaust gas (kg / s). Among these, since the EGR gas e ₁ is the exhaust gas e of the previous cycle, the breakdown is equal to the exhaust gas in the steady state. The breakdown of the exhaust gas e is as follows.

・ Unburned air; Ga-Lth · Gf (kg / s)
(Lth is the theoretical combustion air quantity kg / kg of fuel.)
Combustion gas (CO ₂ + H ₂ O + N ₂ ); (Lth + 1) Gf (kg / s)
-EGR gas in previous cycle; Gegr (kg / s)
Total: Ga + Gf + Gegr (kg / s)
This breakdown is schematically shown in FIG.

ここで、Ｒｉ；各気体成分の気体定数（ｋＪ／ｋｇＫ）
ｇｉ；各気体成分の質量比（ｋｇ／ｋｇ） Here, the gas constant R of the mixed gas (a + e ₁ ) is calculated by the following equation.

Where Ri: gas constant of each gas component (kJ / kgK)
gi: Mass ratio of each gas component (kg / kg)

ここで、Ｒａ；空気の気体定数（ｋＪ／ｋｇＫ）
Ｒegr；排気ガスの気体定数（ｋＪ／ｋｇＫ）
Ｒburnt；排気ガス中の完全燃焼したガスの気体定数（ｋＪ／ｋｇＫ）
但し、符号「_n」は現サイクルの値であり、符号「_n−1」は前サイクルの値を表す。 From the equation (1), the gas constant Rmix of the air supply (mixed gas (a + e1)) of the cylinder 2 is obtained by the sequential calculation of the following equation.

Here, Ra: gas constant of air (kJ / kgK)
Regr: Gas constant of exhaust gas (kJ / kgK)
Rburnt: Gas constant of the completely burned gas in the exhaust gas (kJ / kgK)
However, the symbol “_n” represents the value of the current cycle, and the symbol “_n−1” represents the value of the previous cycle.

Since the gas constant Ra of air is known and the gas constant Regr of the exhaust gas can be calculated by sequential calculation according to the above formula, if Rburnt is known, the gas constant Rmix of the mixed gas (a + e ₁ ) can be calculated. Next, a method for calculating the gas constant Rburnt will be described.

When the weight ratio of C and H atoms in the fuel oil is gc and gH, respectively, the theoretical combustion air amount Lth can be obtained by the following equation.

The amount of generated exhaust gas when 1 kg of fuel is completely burned at the stoichiometric air-fuel ratio is obtained by the following equation.
CO ₂ production amount; G _CO2 = 3.664 · g _C (kg) (5)
H ₂ O production amount; G _H2O = 8.937 · g _H (kg) (6)
N ₂ ; G _N2 = 0.768 · Lth (kg) (7)

以上の（２）式、（３）式及び（８）式の逐次計算により、混合気体（ａ＋ｅ_１）のＲmixが算出される。 At this time, the gas constant Rburnt of the fuel gas in the exhaust gas is obtained by the following equation.

The Rmix of the mixed gas (a + e ₁ ) is calculated by the sequential calculation of the above equations (2), (3), and (8).

According to the present embodiment, the gas constant Rmix of the mixed gas (a + e ₁ ) is calculated from the excess air ratio calculated in the previous cycle, and this is used for calculating the excess air ratio in the current cycle. Can be improved. Therefore, even when the EGR method is applied, harmful substances in the exhaust gas can be reduced.
In particular, even when the operating conditions of the gas engine 1 change suddenly (when the load fluctuates, etc.), it is possible to estimate the excess air ratio with high accuracy in real time and to improve the exhaust gas properties at the time of excessive response.

  In the exhaust gas of the engine, the main problems are NOx (nitrogen oxide) and HC (hydrocarbon). As shown in FIG. 5, in general, NOx becomes maximum near the stoichiometric air-fuel ratio, and the emission amount decreases even if it is leaner or richer than that. On the other hand, HC becomes minimum near the stoichiometric air-fuel ratio, and HC emission tends to increase regardless of whether it is rich or lean. For this reason, an optimal excess air ratio λ is determined from the balance of NOx and HC in operation, and control is performed so as to match it. For example, the optimum λ is 2.4 to 3.2 for a diesel engine and about 1.8 to 2.3 for a gas engine.

  At this time, if the estimation accuracy of the excess air ratio λ is low, the operating point deviates from the optimum point, and the exhaust gas properties deteriorate. That is, NOx increases if it is excessive, and HC increases if it is lean.

  Next, FIG. 6 shows an example of a method of operating the air supply throttle valve 12 and the EGR valve 14 for controlling the excess air ratio λ in the present embodiment. In FIG. 6, this operating method is a method that facilitates control of the excess air ratio λ by operating only one of the air supply throttle valve 12 and the EGR valve 14 at a time. That is, when the excess air ratio λ is controlled from small to large, first, the EGR valve 14 is fully opened, and the opening degree of the air supply throttle valve 12 is gradually increased.

  When the air supply throttle valve 12 is fully opened, the excess air ratio λ is controlled from small to large by gradually decreasing the opening degree of the EGR valve 14. With this operation, the excess air ratio λ can be easily controlled from small to large. When the excess air ratio λ is changed from large to small, the order of the operations may be reversed.

Next, the result of verifying the difference in the estimated λ accuracy caused by the presence or absence of correction of the gas constant between the present invention and the conventional method by numerical simulation will be described.
FIG. 7 shows a state at the time of transient response in which the output of the gas engine fluctuates stepwise, the vertical axis shows the load (specifically, the fuel flow rate (kg / sec)), and the horizontal axis shows the time (seconds). Show. In such an excessive response, when the gas constant of the supply air is sequentially corrected according to the present invention and when the air gas constant is used in the conventional method, the estimated amount of air supply to the cylinder or the estimated λ value The deviation is shown in FIG. 8 or FIG.

  FIG. 8 shows the deviation state of the estimated air supply amount, and the vertical axis indicates the ratio between the case where the gas constant R is corrected according to the present invention and the case where the conventional method is not corrected (with R correction / without R correction). The horizontal axis indicates time (seconds). FIG. 8 shows the divergence state of the excess air ratio λ, and the vertical axis shows the ratio (with R correction / without R correction) when the gas constant is corrected according to the present invention and when the conventional method is not corrected. The horizontal axis indicates time (seconds).

  As a result of the verification, it is clear that there is a maximum deviation of about 0.55% in the estimated air supply amount between the method of the present invention and the conventional method, and a maximum deviation of about 0.15% in the excess air ratio λ. It was. Therefore, it is expected that the estimation accuracy of the excess air ratio λ is improved by about 0.15% by applying the present invention, and the exhaust gas properties can be improved.

  In the above-described embodiment, the air supply throttle valve 12 and the EGR valve 14 are operated to control the excess air ratio λ. The excess air ratio λ may be controlled by controlling the degree.

  According to the present invention, the gas constant used for the calculation of the supply air amount is sequentially calculated from the air excess rate in the previous cycle and the measurement results of various parameters and updated sequentially, thereby improving the accuracy of the air excess rate control. Thus, even during an excessive response in which the exhaust gas properties tend to deteriorate, harmful components in the exhaust gas can be reduced, which is suitable for use in diesel engines, gas engines, and the like.

1 is a system diagram of an excess air ratio control device for a gas engine according to an embodiment of the present invention. It is a diagram which shows the relationship between the gas constant R and an EGR rate. It is a block diagram of the lambda estimation means 30 of the embodiment. (A) is a schematic diagram which shows the breakdown of engine air supply, (b) is a schematic diagram which shows the breakdown of engine exhaust gas. It is a diagram which shows the relationship between the excess air ratio (lambda) of an engine, and exhaust gas property. It is a diagram which shows the control method of excess air ratio (lambda). It is a diagram which shows an engine load fluctuation time. It is a diagram which shows the deviation state of the air supply amount estimated value of this invention system at the time of engine load fluctuation | variation, and a subordinate system. It is a diagram which shows the deviation state of the excess air ratio (lambda) of this invention system at the time of engine load fluctuation | variation, and a slave system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas engine 2 Cylinder 3 Intake air path 4 Exhaust path 11 Supercharger 12 Supply throttle valve 13 EGR gas path 14 EGR valve 25 (lambda) control apparatus 30 (lambda) estimation means 31 Intake mixture amount calculation means 32 EGR amount calculation means 33 EGR Air amount calculation means in gas 34 λ calculation means 36 Gas constant calculation means for EGR gas 37 Gas constant calculation means for supply air M Target air excess ratio map R Gas constant λ Air excess ratio

Claims (5)

In a method for controlling an excess air ratio of an engine configured to recirculate a part of exhaust gas to an intake side of a cylinder,
The excess air ratio of the previous cycle is calculated from the engine specifications, operating conditions, intake air amount, and fuel flow rate, and the gas constant of the intake gas mixture including recirculation gas sucked into the cylinder is calculated from the excess air ratio. ,
The excess air ratio of the current cycle is calculated using the gas constant, and the excess air ratio of the current cycle is controlled to approach the target excess air ratio derived from a preset target excess air ratio map. Engine excess air management method.   The excess air ratio was controlled by controlling the opening of the throttle valve installed in the intake air path or the flow rate adjusting valve installed in the recirculation gas path that returns part of the exhaust gas to the cylinder. The engine excess air ratio management method according to claim 1. From the engine specifications and operating conditions, and the gas constant, temperature and pressure of the gas mixture sucked into the cylinder, the flow rate of the gas mixture is calculated.
The recirculation gas amount is calculated from the intake mixed gas flow rate and the intake air amount sucked from the intake air passage,
The excess air ratio of the engine according to claim 1, wherein the excess air ratio of the previous cycle is calculated from the intake air amount and the air amount in the recirculation gas calculated from the fuel supply amount. Rate management method. In the apparatus for controlling the excess air ratio of the engine configured to recirculate a part of the exhaust gas discharged from the engine to the intake side of the cylinder,
A means for calculating the excess air ratio of the previous cycle from the engine specifications, operating conditions, intake air amount, fuel flow rate, and calculating the gas constant of the intake gas mixture including the recirculation gas sucked into the cylinder from the excess air ratio Means for calculating the excess air ratio of the current cycle using the gas constant,
An engine excess air ratio management device that controls an excess air ratio in a current cycle to approach a target excess air ratio derived from a preset target excess air ratio map. A throttle valve interposed in the intake air passage and a flow rate adjustment valve interposed in the recirculation gas passage for returning a part of the exhaust gas to the cylinder,
5. The engine excess air ratio management device according to claim 4, wherein the excess air ratio is controlled by controlling an opening degree of the throttle valve or the flow rate adjusting valve.

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