JP6916760B2 - Internal combustion engine air-fuel ratio estimation device and internal combustion engine air-fuel ratio estimation method - Google Patents

Description

The present disclosure relates to an air-fuel ratio estimation device for an internal combustion engine for estimating an air-fuel ratio in a combustion chamber of an internal combustion engine, and a method for estimating the air-fuel ratio of the internal combustion engine.

Internal combustion engines such as gas engines that can output power by burning an air-fuel mixture generated by mixing fuel gas with intake air are known. As one method of this type of internal combustion engine, a mixture is generated by premixing the fuel gas supplied from the fuel supply valve on the upstream side of the combustion chamber and the intake air taken in from the outside to obtain a predetermined length. There is a so-called premixing method in which the air-fuel mixture is taken into the combustion chamber through the intake pipe.

The internal combustion engine is used, for example, as a power source for a generator in a power plant, and mainly performs combustion control and air-fuel ratio control. In combustion control, feedback control is performed in which the output rotation speed or load is used as the control amount and the fuel gas supply amount is used as the operation amount in order to keep the output rotation speed and load constant. In the air-fuel ratio control, in order to keep the air-fuel ratio constant in the combustion chamber, the opening degree of the throttle valve arranged in front of the intake manifold is adjusted by performing feedback control using the air-fuel ratio as a control amount.

By the way, in this type of internal combustion engine, it is required to reduce the influence on the frequency of the power generation end by suppressing the fluctuation of the output rotation speed when the load fluctuates such as when the load is applied or when the load is cut off. Be done. In order to suppress the fluctuation of the output rotation speed when the load fluctuates in this way, the estimation accuracy of the air-fuel ratio, which is the control amount in the above-mentioned air-fuel ratio control, is important.

In a premixed internal combustion engine, the volume of piping from the fuel gas supplied from the fuel supply valve to the combustion chamber is large, so the fuel gas supplied from the fuel supply valve takes time to reach the combustion chamber. It takes. Therefore, in order to ensure good estimation accuracy of the air-fuel ratio, it is necessary to consider such a time delay. For example, Patent Document 1 describes that the air-fuel ratio is estimated in consideration of the time delay by introducing a fuel gas transportation delay model in the intake pipe.

Japanese Unexamined Patent Publication No. 2000-282948

However, in Patent Document 1, since it is necessary to set the time constant in the fuel gas transport delay model as a parameter, it is difficult to obtain an appropriate time constant according to the operating state, and the validity of the result is guaranteed. Is difficult. Further, in Patent Document 1, since the system is identified in the control unit (ECU) of the internal combustion engine, complicated arithmetic processing is required.

At least one embodiment of the present invention has been made in view of the above circumstances, and the air-fuel ratio can be estimated accurately by considering the transportation delay of the fuel gas in the intake pipe without performing complicated calculation processing. It is an object of the present invention to provide an air-fuel ratio estimation device for an internal combustion engine and a method for estimating an air-fuel ratio of an internal combustion engine.

(1) The air-fuel ratio estimation device for an internal combustion engine according to at least one embodiment of the present invention is used to solve the above problems.
In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a device,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. A storage unit that stores the air-fuel ratio estimation model of the intake pipe,
A state parameter acquisition unit that acquires the state parameters,
Using the air-fuel ratio estimation model stored in the storage unit, an air-fuel ratio estimation unit that estimates the air-fuel ratio corresponding to the state parameter acquired by the state parameter acquisition unit, and an air-fuel ratio estimation unit.
To be equipped.

According to the configuration of (1) above, the air-fuel ratio corresponding to the state parameter is estimated by inputting the state parameter regarding at least one of the fuel gas or the air-fuel mixture in the intake pipe into the air-fuel ratio estimation model. Such an air-fuel ratio estimation model uses a calculation formula that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe, so that the fuel that passes through the intake pipe having a predetermined capacity without performing complicated calculation processing. It is possible to estimate the air-fuel ratio in consideration of the gas transportation delay.

(2) In some embodiments, in the configuration of (1) above,
The air-fuel ratio estimation model can evaluate the fuel gas concentration by integrating the difference between the supply flow rate of the fuel gas to the intake pipe and the discharge flow rate of the fuel gas to the intake pipe. It is a physical model of piping.

According to the configuration of (2) above, the fuel gas concentration passing through the intake pipe is compared by integrating the difference between the fuel gas supply flow rate to the intake pipe and the fuel gas discharge flow rate to the intake pipe. It can be accurately obtained by simple arithmetic processing.

(3) In some embodiments, in the configuration of (1) or (2) above,
It is provided with a time constant calculation unit that calculates a time constant by converting the air-fuel ratio estimation model into a transfer function.

According to the configuration of (3) above, by converting the air-fuel ratio estimation model into a transfer function, the time constant regarding the transportation delay of the fuel gas in the intake pipe can be obtained as an appropriate value. The time constant thus obtained can also be used as a reliable value (that is, a value whose validity is guaranteed) when the time constant is obtained as a parameter as in Patent Document 1, for example.

(4) In some embodiments, in any one of the above (1) to (3),
The intake pipe includes a first intake pipe and a second intake pipe arranged in series with each other with respect to the flow of the air-fuel mixture.
The air-fuel ratio estimation model is
-Includes a first physical model corresponding to the first intake pipe and a second physical model corresponding to the second intake pipe.
-The state parameter on the output side of the first intake pipe calculated by the first physical model and the state parameter on the inlet side of the second intake pipe of the second physical model are configured to be common. NS.

According to the configuration (4) above, the air-fuel ratio is estimated using the first physical model and the second physical model corresponding to each of the first intake pipe and the second intake pipe constituting the intake pipe. By dividing the intake pipe into the first intake pipe and the second intake pipe in this way and using the corresponding physical models, it is possible to more accurately simulate how the fuel gas passes through the intake pipe with a time delay. Can be inhaled.

(5) In some embodiments, in the configuration of (4) above,
The first intake pipe is provided between the fuel gas supply location for the intake pipe and the compressor installed on the intake pipe.
The second intake pipe is provided between the compressor and the combustion chamber.

According to the configuration of (5) above, the intake pipe is divided into a first intake pipe and a second intake pipe with the compressor as a boundary. The pressure / temperature state changes greatly with the compressor, and the pressure / temperature on the downstream side of the compressor can be measured. In addition, the pressure and temperature on the upstream side of the compressor are close to the conditions of the outside air, so it is easy to estimate. Therefore, it is possible to make an estimation using the measured values of the existing sensors while avoiding the cost increase of the installation of the additional sensor and the complexity of the system.

(6) The air-fuel ratio estimation method for an internal combustion engine according to at least one embodiment of the present invention is to solve the above problems.
In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a method,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. The process of preparing the air-fuel ratio estimation model of the intake pipe and
The process of acquiring the state parameters and
A step of estimating the air-fuel ratio corresponding to the state parameter using the air-fuel ratio estimation model, and
To be equipped.

According to the method (6) above, the air-fuel ratio corresponding to the state parameter is estimated by inputting the state parameter regarding at least one of the fuel gas or the air-fuel mixture in the intake pipe into the air-fuel ratio estimation model. Such an air-fuel ratio estimation model uses a calculation formula that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe, so that the fuel that passes through the intake pipe having a predetermined capacity without performing complicated calculation processing. It is possible to estimate the air-fuel ratio in consideration of the gas transportation delay.

According to at least one embodiment of the present invention, an air-fuel ratio estimation device for an internal combustion engine capable of accurately estimating an air-fuel ratio by considering a transportation delay of fuel gas in an intake pipe without performing complicated arithmetic processing. Also, a method for estimating the air-fuel ratio of an internal combustion engine can be provided.

It is an overall block diagram of the internal combustion engine which concerns on at least one Embodiment of this invention. It is a block diagram which functionally shows the internal structure of the air-fuel ratio estimation apparatus which concerns on 1st Embodiment. It is a flowchart which shows the air-fuel ratio estimation method performed by the air-fuel ratio estimation apparatus of FIG. 2 for each process. It is a schematic diagram which conceptually shows the air-fuel ratio estimation model in 1st Embodiment. It is a graph which shows the transition of the air-fuel ratio when the load of the internal combustion engine 1 changes stepwise, together with the transition of the fuel gas supply amount. It is a block diagram which functionally shows the internal structure of the air-fuel ratio estimation apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the air-fuel ratio estimation method performed by the air-fuel ratio estimation apparatus of FIG. 6 for each process. It is a schematic diagram which conceptually shows the air-fuel ratio estimation model in 2nd Embodiment. It is a simulation result which shows the transition of the estimated value of the air-fuel ratio estimated by the air-fuel ratio estimation method of FIG. 7 together with a state parameter. It is a schematic diagram which shows the state which divided the intake pipe into a plurality of areas in 3rd Embodiment. It is a schematic diagram which conceptually shows the air-fuel ratio estimation model in 3rd Embodiment. It is a simulation result based on the air-fuel ratio estimation model which concerns on 3rd Embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, and are merely explanatory examples. do not have.

FIG. 1 is an overall configuration diagram of an internal combustion engine 1 according to at least one embodiment of the present invention. The internal combustion engine 1 is a gas engine that uses fuel gas as fuel, and is, for example, a power generation engine that outputs power to a generator (not shown) for generating power in a power generation plant or the like.

The internal combustion engine 1 has at least one cylinder 2. In the present embodiment, the internal combustion engine 1 has a plurality of cylinders 2, but only one cylinder 2 is typically shown in FIG. 1 for easy understanding.

The cylinder 2 includes a cylinder 6 integrally formed with a cylinder block 4 and a piston 8 configured to reciprocate in the cylinder. The cylinder 6 and the piston 8 form a main combustion chamber 10. Further, each cylinder 2 is provided with an intake port 12 for taking in an air-fuel mixture of fuel gas and intake air, and an exhaust port 14 for discharging the exhaust gas generated in the main combustion chamber 10.

The intake port 12 has an intake valve 16 that can be opened and closed in response to a control signal from an ECU (engine control unit: Engine Control Unit). Further, the intake ports 12 of each cylinder 2 are connected to each other via an intake manifold 20 for connecting to an intake pipe 18 provided on the upstream side.

The intake pipe 18 is provided so as to connect between the mixer 26 arranged at the confluence of the outside air supply line 22 and the main fuel gas supply line 24 and the intake port 12. In the mixer 26, an air-fuel mixture is generated by mixing the intake air (outside air) taken in from the outside via the outside air supply line 22 and the fuel gas supplied from the main fuel gas supply line 24. The air-fuel mixture generated by the mixer 26 is supplied to the intake port 12 via the intake pipe 18.
The intake pipe 18 is provided with a throttle valve 17 for controlling the flow rate of the air-fuel mixture supplied to the intake port 12.

An air filter 28 for removing foreign matter contained in the intake air taken in from the outside is arranged in the outside air supply line 22. Further, the main fuel gas supply line 24 is provided with an adjusting valve 30 for adjusting the amount of fuel gas supplied to the mixer 26. As a result, the air-fuel mixture generated by mixing the fuel gas and the intake air in advance in the mixer 26 is supplied to the intake port 12 via the intake pipe 18.

A compressor 32 for supercharging the air-fuel mixture generated by the mixer 26 to the main combustion chamber 10 is arranged on the upstream side of the throttle valve 17 in the intake pipe 18. The compressor 32 is connected to an exhaust turbine 36 provided in the exhaust passage 34, and is driven in conjunction with the exhaust turbine 36 driven by the exhaust gas flowing through the exhaust passage 34.
The air-fuel mixture boosted by the compressor 32 is cooled by the intercooler 19 arranged on the downstream side of the throttle valve 17 and then supplied to the intake port 12.

An exhaust passage 34 for discharging the exhaust gas generated in the main combustion chamber 10 to the outside is connected to the exhaust port 14. An exhaust turbine 36 that can be driven by exhaust gas is arranged in the exhaust passage 34. The exhaust turbine 36 constitutes the turbocharger 40 together with the compressor 32 described above. The exhaust gas that has passed through the exhaust turbine 36 is discharged to the outside after a predetermined exhaust gas treatment is performed by an exhaust gas treatment device (not shown).

The exhaust passage 34 of the present embodiment has a bypass passage 42 configured to bypass the exhaust turbine 36. A waist gate valve 44 that can be opened and closed according to a control signal is installed in the bypass passage 42.

Further, the cylinder block 4 is provided with a sub chamber mouthpiece 48 having a sub combustion chamber 46. A plurality of nozzles (not shown) for injecting a flame into the main combustion chamber 10 are formed around the tip of the auxiliary chamber cap 48. Fuel gas is supplied to the sub-combustion chamber 46 via the sub-fuel gas supply line 52, and a flame is formed by an ignition plug (not shown) provided in the sub-combustion chamber 46. The flame formed in the sub-combustion chamber 46 is blown out from the injection port into the main combustion chamber 10 in a torch shape, so that efficient combustion can be performed in a wide range of the main combustion chamber 10.

The auxiliary fuel gas supply line 52 is provided with an adjusting valve 54 for adjusting the amount of fuel gas supplied to the auxiliary combustion chamber 46. The sub fuel gas supply line 52 merges with the main fuel gas supply line 24 on the upstream side, but may be independent of each other.

The main fuel gas supply line 24 is provided with a first flow rate sensor 56 for detecting the flow rate of the fuel gas supplied to the mixer 26. A second flow sensor 58 for detecting the flow rate of the air-fuel mixture supplied from the intake pipe 18 to the intake port 12 is provided at the outlet of the intake pipe 18 (that is, in the vicinity of the intake port 12). Further, the intake pipe 18 is provided with a pressure sensor 60 and a temperature sensor 62 for detecting the pressure and temperature of the air-fuel mixture flowing in the intake pipe 18, respectively. The detected values of these various sensors are input to the air-fuel ratio estimation device 100, which will be described later, as electrical signals.

<First Embodiment>
Subsequently, the air-fuel ratio estimation device 100 of the internal combustion engine 1 having the above configuration will be described. FIG. 2 is a block diagram functionally showing the internal configuration of the air-fuel ratio estimation device 100 according to the first embodiment, and FIG. 3 shows the air-fuel ratio estimation method implemented by the air-fuel ratio estimation device 100 of FIG. 2 for each process. It is a flowchart which shows.

The air-fuel ratio estimation device 100 is configured by installing a program for implementing the air-fuel ratio estimation method according to at least one embodiment of the present invention on an arithmetic processing unit such as a computer. In this case, the program may be recorded in advance on a computer-readable recording medium, and the program may be installed by reading the recording medium with an arithmetic processing unit.

Further, in FIG. 2, the components of the air-fuel ratio estimation device 100 are shown as functional blocks divided for each function, but these functional blocks may be integrated with each other or may be further subdivided. Further, the air-fuel ratio estimation device 100 may be configured by a single arithmetic processing unit, or may be configured by a plurality of arithmetic processing units (including, for example, a cloud server) capable of communicating with each other.

The air-fuel ratio estimation device 100 includes a storage unit 102 that stores the air-fuel ratio estimation model 110, a state parameter acquisition unit 104, and an air-fuel ratio estimation unit 106.

The air-fuel ratio estimation model 110 used for estimating the air-fuel ratio is stored in advance in the storage unit 102, which is a storage device (step S10). The air-fuel ratio estimation model 110 stored in the storage unit 102 is an arithmetic model capable of calculating the air-fuel ratio by using an arithmetic expression in which a state parameter relating to at least one of the fuel gas or the air-fuel mixture in the intake pipe 18 is used as a variable. By including the fuel gas concentration of the air-fuel mixture existing in the intake pipe 18, the air-fuel ratio estimation model 110 delays the transportation of the fuel gas passing through the intake pipe having a predetermined capacity without performing complicated calculation processing. It is possible to estimate the air-fuel ratio in consideration.

Here, the specific contents of the air-fuel ratio estimation model 110 will be described. FIG. 4 is a schematic diagram conceptually showing the air-fuel ratio estimation model 110 of the first embodiment.

In this air-fuel ratio estimation model 110, as shown in FIG. 4, a volume 112 that models an intake pipe 18 having a predetermined volume is set. In the volume 112, a state parameter relating to at least one of the fuel gas and the air-fuel mixture in the intake pipe 18 is set as a variable. In the present embodiment, as such state parameters, the inlet fuel gas flow rate Wg _in of the intake pipe 18, the outlet air- _{fuel mixture flow rate Wmix out} , the outlet fuel gas flow rate Wg _out , the fuel gas concentration C in the volume 112, the pressure P, and the temperature T , Volume V, mass m are set.

In the air-fuel ratio estimation model 110, the detection value of the first flow rate sensor 56 is inputted as an inlet fuel gas flow _{Wg in} the intake pipe 18, the detection value of the second flow rate sensor 58 is inputted as an outlet-air mixture flow _{wmix out} , The detection value of the pressure sensor 60 is input as the pressure P, and the detection value of the temperature sensor 62 is input as the temperature T. Further, a known value set as a specification of the intake pipe 18 is input to the volume V.

The outlet fuel gas flow rate Wg _out of the intake pipe 18 can be obtained by the following equation using _{the outlet air-fuel mixture flow rate Wmix out} of the intake pipe 18 assuming that the fuel gas concentration C in the intake pipe 18 is constant.

（２）式の分子成分は、吸気配管１８に対する燃料ガスの供給流量である入口燃料ガス流量Ｗｇ_ｉｎ、及び、吸気配管１８からの燃料ガスの排出流量である出口燃料ガス流量Ｗｇ_ｏｕｔの差分を積分したものである。吸気配管１８は所定容積を有するため、燃料ガスが吸気配管１８を通過する際に要する時間（時間遅れ）に対応して、ある瞬間における燃料ガスの供給流量と排出流量との間には少なからず差分が生じる。（２）式では、当該積分値を吸気配管１８内に存在する混合気の質量ｍで割算することにより、所定容量を有する吸気配管１８における燃料ガス濃度Ｃをシンプルな演算式で精度よく算出することができる。 Here, the fuel gas concentration C used in the equation (1) is obtained by the following equation.

The molecular component of the formula (2) is the difference between the inlet fuel gas flow rate Wg _{in , which is the supply flow rate of fuel gas to the intake pipe 18, and the outlet fuel gas flow rate Wg out} , which is the discharge flow rate of fuel gas from the intake pipe 18. It is an integral. Since the intake pipe 18 has a predetermined volume, there is not a little between the supply flow rate and the discharge flow rate of the fuel gas at a certain moment, corresponding to the time (time delay) required for the fuel gas to pass through the intake pipe 18. There is a difference. In the equation (2), the fuel gas concentration C in the intake pipe 18 having a predetermined capacity is calculated accurately by a simple calculation formula by dividing the integrated value by the mass m of the air-fuel mixture existing in the intake pipe 18. can do.

The mass m of the air-fuel mixture included in the equation (2) is the pressure P and the temperature T which are the detection values of the pressure sensor 60 and the temperature sensor 62 provided in the intake pipe 18, and the volume which is the specification value of the intake pipe 18. It can be calculated from the gas state equation shown by the following equation using V and the gas constant R.

尚、定数Ｌｔｈは理論空燃比である。 Then, by solving the equations (1) to (3) simultaneously, the outlet fuel gas flow rate Wg _out can be obtained. In the air-fuel ratio estimation model 110, the air-fuel ratio λ is estimated by inputting _{the outlet fuel gas flow rate Wg out thus obtained into the following equation.}

The constant Lth is the stoichiometric air-fuel ratio.

Subsequently, the state parameter acquisition unit 104 acquires the state parameters required for the air-fuel ratio estimation calculation by the air-fuel ratio estimation model 110 (step S11). That is, each state parameter to be input from the outside in Eqs. (1) to (4) is acquired. Specifically, the state parameter acquisition unit 104 acquires the detection value of the first flow rate sensor 56 as an inlet fuel gas flow _{Wg in,} and acquires the detection value of the second flow rate sensor 58 as an outlet-air mixture flow _{wmix out,} The detected value of the pressure sensor 60 is acquired as the pressure P, and the detected value of the temperature sensor 62 is acquired as the temperature T.

Subsequently, the air-fuel ratio estimation unit 106 estimates the air-fuel ratio corresponding to the state parameter acquired by the state parameter acquisition unit 104 using the air-fuel ratio estimation model 110 stored in the storage unit 102 (step S12). That is, the air-fuel ratio estimation unit 106 calculates the estimated value of the air-fuel ratio λ by substituting each state parameter acquired in step S11 into the equations (1) to (4).

Here, FIG. 5 is a graph showing the transition of the air-fuel ratio λ when the load of the internal combustion engine 1 changes stepwise, together with the transition of the fuel gas supply amount. In FIG. 5, a simulation result using an MVM (Mean Value Model) in which the intake pipe 18 is represented by a zero-dimensional volume element and an estimated value based on a conventional model are shown as comparison targets for the estimated value of the air-fuel ratio λ. Has been done.
In FIG. 5, as an example of the conventional model, the following equation Wgout = 1 / (T · s + 1) · Wgin, which is a first-order lag equation of 1 / (T · s + 1) using the time constant T (parameter) [Ssec].
Wgout is sought from.

In FIG. 5A, in order to keep the output rotation speed of the internal combustion engine 1 constant when the load of the internal combustion engine gradually increases to 0%, 25%, 50%, 75%, and 100%, It is shown that the fuel gas supply is controlled to increase in stages. At this time, as shown in FIG. 5B, the estimated value of the air-fuel ratio λ is closer to the simulation result using MVM than the estimated value of the conventional model. 5 (c) to 5 (f) show the transition of the air-fuel ratio λ in the vicinity of the times t1, t2, t3, and t4 of FIG. 5 (b) in an enlarged manner, and each time t1, t2, t3 where the load fluctuation occurs. It is shown that the amount of deviation from the simulation result of MVM when the air-fuel ratio λ fluctuates abruptly at t4 is small. This indicates that the air-fuel ratio can be estimated more accurately than the conventional model.

<Second Embodiment>
FIG. 6 is a block diagram functionally showing the internal configuration of the air-fuel ratio estimation device 100'according to the second embodiment, and FIG. 7 is a process of the air-fuel ratio estimation method implemented by the air-fuel ratio estimation device 100'of FIG. It is a flowchart shown for each.
In the following description, common reference numerals will be given to the configurations corresponding to the above-described embodiments, and duplicate description will be omitted as appropriate.

As shown in FIG. 6, the air-fuel ratio estimation device 100'has a time constant calculation unit 113 that calculates the time constant L based on the physical model of the intake pipe 18 as compared with the air-fuel ratio estimation device 100 described above, and the time constant. Further includes an air-fuel ratio estimation model creation unit 114 that creates an air-fuel ratio estimation model based on a constant.

が得られる。このように得られた（５）式を（１）式に代入することにより、次式

が得られる。そして（６）式に（３）式を代入すると次式

が得られる。（７）式によれば、出口燃料ガス流量Ｗｇ_ｏｕｔは、入口燃料ガス流量Ｗｇ_ｉｎの一次遅れで表されており、時定数τが求められる。尚、むだ時間Ｌは次式

により得られる。ここでρは混合気の密度である。 First, the time constant calculation unit 113 calculates the time constant τ by converting the equations (1) to (3), which are the physical models of the intake pipe 18, into the transfer function F (step S20). Specifically, the following equation is obtained by Laplace transforming equation (2).

Is obtained. By substituting Eq. (5) obtained in this way into Eq. (1), the following equation

Is obtained. Then, substituting equation (3) into equation (6), the following equation

Is obtained. According to the equation (7), the outlet fuel gas flow rate Wg _out is represented by the first-order lag of the inlet fuel gas flow rate Wg _in , and the time constant τ can be obtained. The waste time L is given by the following equation.

Obtained by Where ρ is the density of the air-fuel mixture.

Subsequently, the air-fuel ratio estimation model creation unit 114 creates the air-fuel ratio estimation model 120 using the time constant τ calculated by the time constant calculation unit 113 (step S21). Here, FIG. 8 is a schematic diagram conceptually showing the air-fuel ratio estimation model 120 in the second embodiment.

に入力されることで、空燃比の推定値λが算出される。尚、Ｌｔｈは理論空燃比である。 Air-fuel ratio estimation model 120 has an inlet fuel gas flow _{Wg in} and outlet air flow Wa as an input parameter. The inlet fuel gas flow rate Wg _in is input to the transfer function in (7) above, and the corresponding outlet fuel gas flow rate Wg _out is calculated. _{Outlet fuel gas flow rate Wg out} outlet intake flow rate Wa output from the transfer function and the following equation

By inputting to, the estimated value λ of the air-fuel ratio is calculated. Lth is the stoichiometric air-fuel ratio.

The air-fuel ratio estimation model 120 created by the air-fuel ratio estimation model creation unit 114 in this way is readable and stored in the storage unit.

Subsequently, the state parameter acquisition unit 104 acquires the state parameters required for the air-fuel ratio estimation calculation by the air-fuel ratio estimation model 120 (step S22). Acquired as an input parameter of the air-fuel ratio estimation model 120 acquires the detection value of the first flow rate sensor 56 as an inlet fuel gas flow Wg _in, the outlet air flow Wa obtained by calculation using detected values of the pressure sensor 60 (Actually, the air-fuel mixture flow rate Wmix _out is calculated using the value detected by the pressure sensor 60, and the outlet intake flow rate Wa is calculated by the equation (Wa = Wmix _{out −} Wg _in )).

Subsequently, the air-fuel ratio estimation unit 106 estimates the air-fuel ratio corresponding to the state parameter acquired by the state parameter acquisition unit 104 using the air-fuel ratio estimation model 120 stored in the storage unit 102 (step S23). That is, the air-fuel ratio estimation unit 106 calculates the estimated value of the air-fuel ratio λ by inputting each state parameter acquired in step S22 into the air-fuel ratio estimation model 120.

Here, FIG. 9 is a simulation result showing the transition of the estimated value of the air-fuel ratio estimated by the air-fuel ratio estimation method of FIG. 7 together with the state parameters. FIG. 9 (a) shows the transition of the flow rate of the fuel gas at the inlet and the outlet of the intake pipe 18, FIG. 9 (b) shows the transition of the estimated value λ of the air-fuel ratio, and FIG. 9 (c) shows the transition. The transition of the flow rate of the air-fuel mixture at the inlet and the outlet of the intake pipe 18 is shown, and FIG. 9 (d) shows the transition of the pressure (detected value of the pressure sensor 60) which is a state parameter, and FIG. 9 (e) shows the transition. Shows the transition of the temperature (detected value of the temperature sensor 62), which is a state parameter, and FIG. 9 (f) shows the transition of the fuel gas concentration C calculated by the equation (2).

As shown in FIGS. 9 (a) and 9 (b), in this simulation, when the flow rate of the fuel gas at the inlet of the intake pipe 18 is changed stepwise, the estimated value λ of the air-fuel ratio in the present embodiment is MVM. Results consistent with those were obtained. This indicates that the estimated value λ of the air-fuel ratio in the second embodiment is reliable.

<Third Embodiment>
Subsequently, the third embodiment will be described. In the first and second embodiments described above, the air-fuel ratio was estimated by modeling the entire intake pipe 18 with one air-fuel ratio estimation model, but in the third embodiment, the intake pipe 18 is divided into a plurality of areas. , The air-fuel ratio is estimated by modeling each of the divided areas.

FIG. 10 is a schematic view showing a state in which the intake pipe 18 is divided into a plurality of areas in the third embodiment. In FIG. 10, the intake pipe 18 in FIG. 1 is shown briefly together with the peripheral configuration. In this example, the compressor 32 arranged in the intake pipe 18 is divided into a first intake pipe 18a on the upstream side and a second intake pipe 18b on the downstream side as a boundary.

In the following description, a plurality of areas divided into each other are referred to as a first intake pipe 18a and a second intake pipe 18b, which conceptually indicates that the intake pipe 18 can be divided into a plurality of areas. , The first intake pipe 18a and the second intake pipe 18b may be structurally integrally configured.

In this case, the above-mentioned air-fuel ratio estimation models 110 and 120 used for estimating the air-fuel ratio may be constructed by applying the above equations to each of the regions (first intake pipe 18a and second intake pipe 18b). good. FIG. 11 is a schematic diagram conceptually showing the air-fuel ratio estimation model 130 in the third embodiment.

The air-fuel ratio estimation model 130 has a first volume 112a corresponding to the first intake pipe and a second volume 112b corresponding to the second intake pipe. In the above-mentioned air-fuel ratio estimation model 110, the entire intake pipe 18 is modeled by one volume 112, but in the air-fuel ratio estimation model 130 according to the present embodiment, the intake pipes 18 are in series with each other with respect to the flow of the air-fuel mixture. It is divided into a first volume 112a corresponding to the first intake pipe and a second volume 112b corresponding to the second intake pipe, and the same modeling is performed for each of the first volume 112a and the second volume 112b. Is done.

Specifically, as shown in FIG. 11, in the air-fuel ratio estimation model 130, the first volume 112a corresponding to the volume V1 of the first intake pipe 18a and the volume V2 of the second intake pipe 18b are supported. The second volume 112b and the like are set. In the first volume 112a and the second volume 112b, state parameters relating to at least one of the fuel gas or the air-fuel mixture in each of the first intake pipe 18a and the second intake pipe 18b are set as variables.

により算出される。また第１吸気配管１８ａはコンプレッサ３２の上流側に位置するため、圧力Ｐ１、温度Ｔ１はそれぞれ大気圧及び大気温度に対応する一定値として設定される。尚、圧力Ｐ１、温度Ｔ１は大気圧及び大気温度を検出するためのセンサを設置して、それらの検出値を用いるようにしてもよい。質量ｍ１は次式

により算出される。また出口燃料ガス流量Ｑｇａｓ_ｏｕｔ１は、上述の（１）式の類似式である次式

により算出される。 Here, the state parameters set in the first volume 112a and the second volume 112b are as follows.
First, as state parameters set for the first volume 112a, the air- _{fuel mixture flow rate Qmix act} for the first intake pipe 18a, the fuel gas flow rate Qgas _in , the fuel gas concentration C1, the pressure P1, the temperature T1, the volume V1, the mass m1 and so on. There is an outlet fuel gas flow rate Qgas _out1 . The air-fuel mixture flow rate Qmix _act can be calculated based on the detected value of the pressure sensor 60. The fuel gas flow rate Qgas _in can be acquired as a detected value of the first flow rate sensor 56. The fuel gas concentration C1 is given by the following equation.

Is calculated by. Further, since the first intake pipe 18a is located on the upstream side of the compressor 32, the pressure P1 and the temperature T1 are set as constant values corresponding to the atmospheric pressure and the atmospheric temperature, respectively. For the pressure P1 and the temperature T1, sensors for detecting the atmospheric pressure and the atmospheric temperature may be installed and the detected values thereof may be used. The mass m1 is the following equation

Is calculated by. Further, the outlet fuel gas flow rate Qgas _out1 is the following equation, which is a similar equation to the above equation (1).

Is calculated by.

In the air-fuel ratio estimation model 130, it is assumed that the air-fuel mixture flow rate Qmix _act supplied to the intake pipe 18 is constant before and after the first volume 112a and the second volume 112b.

により算出される。また圧力Ｐ２、温度Ｔ２はそれぞれ圧力センサ６０及び温度センサ６２の検出値として取得される。また質量ｍ２は次式

により算出される。また出口燃料ガス流量Ｑｇａｓ_ｏｕｔ２は、上述の（１）式の類似式である次式

により算出される。 Subsequently, as the state parameters set for the second volume 112b, there are the fuel gas concentration C2, the pressure P2, the temperature T2, the volume V2, the mass m2, and the outlet fuel gas flow rate Qgas _out2 in the second intake pipe 18b. The fuel gas concentration C2 is given by the following equation.

Is calculated by. Further, the pressure P2 and the temperature T2 are acquired as detected values of the pressure sensor 60 and the temperature sensor 62, respectively. The mass m2 is given by the following equation.

Is calculated by. Further, the outlet fuel gas flow rate Qgas _out2 is the following equation, which is a similar equation to the above equation (1).

Is calculated by.

As shown in FIG. 11, since the first volume 112a and the second volume 112b are connected in series with each other, the air- _{fuel mixture flow rate Qmix act} and the outlet fuel gas, which are the state parameters on the outlet side of the first volume 112a, are connected. The flow rate Qgas _out1 is common to the state parameter on the inlet side of the second volume 112b.

The air-fuel ratio estimation unit 106 estimates the air-fuel ratio based on the air-fuel ratio estimation model 130 having such a configuration. As described above with reference to FIG. 11, the air-fuel ratio estimation unit 106 inputs each state parameter acquired by the state parameter acquisition unit 104 into the air-fuel ratio estimation model 130 prepared in the storage unit. , Estimate the air-fuel ratio.

The air-fuel ratio estimation calculation by the air-fuel ratio estimation model 130 is performed by setting the precondition that the state parameter on the outlet side of the first volume 112a and the state parameter on the inlet side of the second volume 112b are common. The estimated value of the air-fuel ratio is calculated based on the same idea as the form. In particular, in the present embodiment, the intake pipe 18 having a predetermined capacity is divided into the first volume 112a and the second volume 112b and modeled, so that the behavior of the fuel gas flowing from the upstream side to the downstream side with a time delay. It is possible to estimate the air-fuel ratio in consideration of. That is, the estimation of the air-fuel ratio in consideration of the secondary delay is the estimation. Therefore, it is possible to estimate the air-fuel ratio with high accuracy as compared with the case where one modeling is applied to the entire intake pipe 18 as in the above-mentioned air-fuel ratio estimation model 110.

FIG. 12 is a simulation result based on the air-fuel ratio estimation model 130 according to the third embodiment. Also in this result, the estimated value of the air-fuel ratio obtained by the air-fuel ratio estimation model 130 was close to the simulation result obtained by MVM, and the high estimation accuracy could be verified.

In the air-fuel ratio estimation model 130, the air-fuel ratio estimation is performed in consideration of the secondary delay by modeling the intake pipe 18 by dividing it into two parts. It is also possible to estimate the air-fuel ratio in consideration of higher-order lag. Further, the finer the division of the intake pipe 18, the higher the estimation accuracy of the air-fuel ratio can be improved, but sufficient estimation accuracy can be obtained even with a relatively small number of divisions. In addition, since the calculation load when the modeling is subdivided increases, it is preferable to determine the number of divisions according to the required estimation accuracy.

As described above, according to the above-described embodiment, the state parameters relating to at least one of the fuel gas or the air-fuel mixture in the intake pipe 18 are input to the air-fuel ratio estimation models 110, 120, 130 to correspond to the state parameters. The air-fuel ratio is estimated. Such air-fuel ratio estimation models 110, 120, and 130 use an arithmetic expression including the fuel gas concentrations C, C1, and C2 of the air-fuel mixture existing in the intake pipe 18 without performing complicated arithmetic processing. It is possible to estimate the air-fuel ratio in consideration of the delay in transporting the fuel gas passing through the intake pipe 18 having a predetermined capacity.

At least one embodiment of the present invention can be used in an air-fuel ratio estimation device for an internal combustion engine for estimating an air-fuel ratio in a combustion chamber of an internal combustion engine, and an air-fuel ratio estimation method for an internal combustion engine.

1 Internal combustion engine 2 Cylinder 4 Cylinder block 6 Cylinder 8 Piston 10 Main combustion chamber 12 Intake port 14 Exhaust port 16 Intake valve 17 Throttle valve 18 Intake pipe 19 Intercooler 20 Intake manifold 22 Outside air supply line 24 Main fuel gas supply line 26 Mixer 28 Air filter 30 Adjustment valve 32 Compressor 34 Exhaust passage 36 Exhaust turbine 40 Turbocharger 42 Bypass passage 44 Westgate valve 46 Sub-combustion chamber 48 Sub-chamber mouthpiece 52 Sub-chamber mouthpiece 52 Sub-fuel gas supply line 54 Adjustment valve 56 First flow sensor 58 Second flow sensor 60 Pressure sensor 62 Temperature sensor 100 Air-fuel ratio estimation device 102 Storage unit 104 State parameter acquisition unit 106 Air-fuel ratio estimation unit 110, 120, 130 Air-fuel ratio estimation model 112 Volume 112a First volume 112b Second volume 113 Time constant calculation unit 114 Empty Fuel ratio estimation model creation department

Claims (8)

In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a device,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. A storage unit that stores the air-fuel ratio estimation model of the intake pipe,
A state parameter acquisition unit that acquires the state parameters,
Using the air-fuel ratio estimation model stored in the storage unit, an air-fuel ratio estimation unit that estimates the air-fuel ratio corresponding to the state parameter acquired by the state parameter acquisition unit, and an air-fuel ratio estimation unit.
With
The air-fuel ratio estimation model can evaluate the fuel gas concentration by integrating the difference between the supply flow rate of the fuel gas to the intake pipe and the discharge flow rate of the fuel gas to the intake pipe. a physical model of the piping, the air-fuel ratio estimator for internal combustion engine. In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a device,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. A storage unit that stores the air-fuel ratio estimation model of the intake pipe,
A state parameter acquisition unit that acquires the state parameters,
Using the air-fuel ratio estimation model stored in the storage unit, an air-fuel ratio estimation unit that estimates the air-fuel ratio corresponding to the state parameter acquired by the state parameter acquisition unit, and an air-fuel ratio estimation unit.
A time constant calculation unit that calculates the time constant by converting the air-fuel ratio estimation model into a transfer function ,
Comprises, an air-fuel ratio estimator for internal combustion engine. In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a device,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. A storage unit that stores the air-fuel ratio estimation model of the intake pipe,
A state parameter acquisition unit that acquires the state parameters,
Using the air-fuel ratio estimation model stored in the storage unit, an air-fuel ratio estimation unit that estimates the air-fuel ratio corresponding to the state parameter acquired by the state parameter acquisition unit, and an air-fuel ratio estimation unit.
With
The intake pipe includes a first intake pipe and a second intake pipe arranged in series with each other with respect to the flow of the air-fuel mixture.
The air-fuel ratio estimation model is
-Includes a first physical model corresponding to the first intake pipe and a second physical model corresponding to the second intake pipe.
-The state parameter on the output side of the first intake pipe calculated by the first physical model and the state parameter on the inlet side of the second intake pipe of the second physical model are configured to be common. that, the air-fuel ratio estimation apparatus of the internal combustion engine. The first intake pipe is provided between the fuel gas supply location for the intake pipe and the compressor installed on the intake pipe.
The air-fuel ratio estimation device for an internal combustion engine according to claim 3 , wherein the second intake pipe is provided between the compressor and the combustion chamber. In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a method,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. The process of preparing the air-fuel ratio estimation model of the intake pipe and
The process of acquiring the state parameters and
A step of estimating the air-fuel ratio corresponding to the state parameter using the air-fuel ratio estimation model, and
Equipped with a,
The air-fuel ratio estimation model can evaluate the fuel gas concentration by integrating the difference between the supply flow rate of the fuel gas to the intake pipe and the discharge flow rate of the fuel gas to the intake pipe. the air-fuel ratio estimation method of Oh Ru, internal combustion engine in the physical model of the piping. In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a method,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. The process of preparing the air-fuel ratio estimation model of the intake pipe and
The process of acquiring the state parameters and
A step of estimating the air-fuel ratio corresponding to the state parameter using the air-fuel ratio estimation model, and
The process of calculating the time constant by converting the air-fuel ratio estimation model into a transfer function, and
A method for estimating the air-fuel ratio of an internal combustion engine. In an internal combustion engine having a combustion chamber in which an air-fuel mixture premixed with intake air and fuel gas is introduced through an intake pipe having a predetermined volume, the air-fuel ratio estimation of the internal combustion engine for estimating the air-fuel ratio in the combustion chamber It ’s a method,
The air-fuel ratio can be calculated using an arithmetic expression that includes the fuel gas concentration of the air-fuel mixture existing in the intake pipe and has a state parameter relating to the fuel gas or at least one of the air-fuel mixture in the intake pipe as a variable. The process of preparing the air-fuel ratio estimation model of the intake pipe and
The process of acquiring the state parameters and
A step of estimating the air-fuel ratio corresponding to the state parameter using the air-fuel ratio estimation model, and
With
The intake pipe includes a first intake pipe and a second intake pipe arranged in series with each other with respect to the flow of the air-fuel mixture.
The air-fuel ratio estimation model is
-Includes a first physical model corresponding to the first intake pipe and a second physical model corresponding to the second intake pipe.
-The state parameter on the output side of the first intake pipe calculated by the first physical model and the state parameter on the inlet side of the second intake pipe of the second physical model are configured to be common. A method for estimating the air-fuel ratio of an internal combustion engine. The first intake pipe is provided between the fuel gas supply location for the intake pipe and the compressor installed on the intake pipe.
The air-fuel ratio estimation method for an internal combustion engine according to claim 7, wherein the second intake pipe is provided between the compressor and the combustion chamber.

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