Engine state estimation device

Abstract

To suppress continuation of combustion failure of an engine.SOLUTION: An engine state estimation device is mounted on an engine device together with an engine that has a throttle valve arranged in an intake pipe, and estimates an intake air quantity of the engine from the pressure of the intake pipe. The engine state estimation device estimates a cylinder flow-in air quantity passing through a throttle valve from the opening thereof, sets an upper limit value of the intake air quantity by using an upper limit coefficient based on the estimated cylinder flow-in air quantity and an engine revolution speed, and estimates the intake air quantity to be the smaller of a provisional intake air quantity based on the pressure of the intake pipe and the set upper limit value.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to an engine state estimating device, and more particularly to an engine state estimating device that is mounted in an engine device together with an engine having a throttle valve. [Background technology]

[0002] Conventionally, as this type of engine state estimation device, one that is mounted on an engine device together with an engine having a throttle valve arranged in an intake pipe has been proposed (for example, see Patent Document 1). In this device, until a first predetermined time has elapsed since the engine is started, the amount of intake air of the engine is estimated (calculated) from the pressure in the intake pipe (intake manifold pressure), and after a second predetermined time has elapsed since the engine is started, the amount of intake air is estimated by Kalman filter calculation from the amount of intake air detected by the intake air amount sensor. Since the amount of intake air of the engine is estimated (calculated) from the pressure in the intake pipe (intake manifold pressure) until the first predetermined time has elapsed since the engine is started, which is a period during which it is difficult to estimate the amount of intake air by Kalman filter calculation, it is said that the amount of intake air can be estimated more accurately. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-173067 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned engine state estimation device, when poor combustion such as a temporary misfire occurs in the engine, the injected fuel does not explode or the explosion is insufficient, so the pressure in the cylinder is lower than when proper combustion is occurring. When the exhaust valve opens in this state, air flows into the cylinder from the exhaust pipe side, and the pressure in the cylinder increases. After that, when the intake valve opens, air flows from the cylinder to the intake pipe, and the amount of air taken into the cylinder is reduced. Therefore, when poor combustion occurs, if the intake air amount is estimated using the same method as when poor combustion does not occur, the estimated intake air amount will be more than the actual intake air amount, and excess fuel will be injected by the fuel injection control, resulting in a rich state, and the poor combustion in the engine may continue.

[0005] The main object of the engine state estimating device of the present invention is to suppress the continuation of poor combustion in the engine. [Means for solving the problem]

[0006] The engine state estimating device of the present invention employs the following means to achieve the above-mentioned main object.

[0007] The engine state estimating device of the present invention comprises: 1. An engine state estimating device that is mounted on an engine device together with an engine having a throttle valve disposed in an intake pipe, and estimates an intake air amount of the engine from a pressure in the intake pipe, comprising: an amount of air flowing into the cylinder from an opening degree of the throttle valve, and an upper limit value of the amount of intake air is set using the estimated amount of air flowing into the cylinder and an upper limit coefficient based on a rotation speed of the engine; The intake air amount is estimated to be the smaller value of the provisional intake air amount based on the pressure of the intake pipe and the set upper limit value. The gist of the present invention is as follows.

[0008] In the engine state estimation device of the present invention, the amount of air flowing into the cylinder through the throttle valve is estimated from the opening degree, and the upper limit of the intake air amount is set using the estimated amount of air flowing into the cylinder and an upper limit coefficient based on the engine speed, and the intake air amount is estimated to be the smaller of the provisional intake air amount based on the pressure of the intake pipe and the set upper limit. When poor combustion occurs, the amount of air flowing from the cylinder into the intake pipe in the next intake stroke differs depending on the engine speed. Therefore, by setting the upper limit of the intake air amount using the estimated amount of air passing through the throttle valve and an upper limit coefficient based on the engine speed, and estimating the intake air amount to be the smaller of the provisional intake air amount based on the pressure of the intake pipe and the set upper limit, when poor combustion occurs, it is possible to prevent the intake air amount from being overestimated, and to prevent the poor combustion in the engine from continuing.

[0009] In the engine state estimation device of the present invention, the upper limit value may be the estimated amount of air flowing into the cylinder multiplied by the upper limit coefficient greater than 1. In this case, the upper limit coefficient may be set higher when the engine speed is equal to or greater than a predetermined speed than when the engine speed is less than the predetermined speed. When poor combustion occurs, the amount of air flowing from the cylinder into the intake pipe in the next intake stroke is greater when the engine speed is high than when the engine speed is low. Therefore, by setting the upper limit value higher when the engine speed is equal to or greater than a predetermined speed than when the engine speed is less than the predetermined speed, the upper limit value can be set more appropriately.

[0010] In the engine state estimating device of the present invention, the engine may include a supercharger having a compressor disposed upstream of the throttle valve in the intake pipe, and may execute a first estimation process for estimating the intake air amount from an opening of the throttle valve and a second estimation process for estimating the intake air amount from a pressure in the intake pipe when supercharging by the supercharger is being performed and the throttle valve is closed due to deceleration, and when transitioning from the first estimation process to the second estimation process, if the upper limit value is smaller than the intake air amount estimated from the opening of the throttle valve, the upper limit value may be gradually changed from the intake air amount estimated from the opening of the throttle valve, and when transitioning from the second estimation process to the first estimation process, if the upper limit value is smaller than the intake air amount estimated from the opening of the throttle valve, the upper limit value may be gradually changed toward the intake air amount estimated from the opening of the throttle valve. This can suppress a sudden change in the intake air amount. [Brief description of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing an outline of the configuration of an engine system 10 equipped with a state estimation device as an embodiment of the present invention. [Diagram 2] 2 is an explanatory diagram showing an example of signals input to and output from an electronic control unit 70 of the engine device 10. FIG. [Diagram 3] FIG. 2 is an explanatory diagram illustrating an example of an air model. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a map for estimating a flow coefficient; [Diagram 5] FIG. 11 is an explanatory diagram showing an example of an opening cross-sectional area estimation map; [Figure 6] FIG. 1 is an explanatory diagram showing a function Φ(Pm / Pa). [Figure 7] FIG. 2 is an explanatory diagram of a throttle model M10. [Figure 8] FIG. 2 is an explanatory diagram of an intake pipe model M20. [Figure 9] FIG. 2 is an explanatory diagram of an intake valve model M30. [Figure 10]4 is an explanatory diagram of the cylinder inflow air amount mci and the cylinder filling air amount mcf. FIG. [Figure 11] FIG. 13 is a block diagram showing an example of an upper limit load rate setting process. [Figure 12] FIG. 2 is an explanatory diagram showing an example of a map. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. EXAMPLES

[0013] Fig. 1 is a schematic diagram showing the configuration of an engine system 10 equipped with an engine state estimating device according to an embodiment of the present invention, and Fig. 2 is an explanatory diagram showing an example of signals input to and output from an electronic control unit 70 of the engine system 10. As shown in Figs. 1 and 2, the engine system 10 of the embodiment includes an engine 12 and an electronic control unit 70. This engine system 10 is mounted on a general vehicle that runs using power from the engine 12, or on various hybrid vehicles that include a motor in addition to the engine 12. The electronic control unit 70 corresponds to the state estimating device of the embodiment.

[0014] The engine 12 is configured as a four-cylinder internal combustion engine that uses fuel such as gasoline or diesel to output power through four strokes: intake, compression, expansion, and exhaust. In this engine 12, air cleaned by an air cleaner 22 is drawn into an intake pipe 23, and the air passes through a throttle valve 26 and a surge tank 27 in this order, and fuel is injected from a fuel injection valve 28 downstream of the surge tank 27 of the intake pipe 23 to mix the air and fuel. Hereinafter, the portion of the intake pipe 23 upstream of the throttle valve 26 is referred to as the "throttle upstream portion 23u," and the portion downstream of the throttle valve 26 is referred to as the "throttle downstream portion 23d." Then, the mixture is drawn into a combustion chamber 30 via an intake valve 29, where it is explosively combusted by an electric spark from an ignition plug 31, and the reciprocating motion of a piston 32 pushed down by the energy of the explosive combustion is converted into the rotational motion of a crankshaft 14. Exhaust gas discharged from the combustion chamber 30 into the exhaust pipe 35 through the exhaust valve 33 is discharged into the outside air through purification devices 37, 38 and is also supplied (recirculated) to the surge tank 27 of the intake pipe 23 through an exhaust gas recirculation device (hereinafter referred to as the "EGR (Exhaust Gas Recirculation) device") 40.

[0015] The purification devices 37, 38 have catalysts (three-way catalysts) 37a, 38a that purify harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), respectively. The EGR device 40 includes an EGR pipe 42 and an EGR valve 44. The EGR pipe 42 connects the purification devices 37 and 38 in the exhaust pipe 35 with the surge tank 27 in the intake pipe 23. The EGR valve 44 is provided in the EGR pipe 42 and is controlled by an electronic control unit 70. In the EGR device 40, the amount of exhaust gas recirculated from the exhaust pipe 35 is adjusted by adjusting the opening degree of the EGR valve 44, and the exhaust gas is recirculated to the intake pipe 23. In this manner, the engine 12 can draw a mixture of air, exhaust, and fuel into the combustion chamber 30.

[0016] The engine 12 further includes a variable valve timing device 34. The variable valve timing device 34 is configured to be able to continuously change the opening and closing timing of the intake valve 29 and the exhaust valve 33, respectively.

[0017] The supercharger 50 is configured as a turbocharger, and includes a turbine 51, a compressor 52, a wastegate valve 54, and a blow-off valve 55. The turbine 51 is disposed upstream of the purification device 37 in the exhaust pipe 35. The compressor 52 is disposed upstream of the throttle valve 26 in the intake pipe 23, and is connected to the turbine 51 via a rotating shaft 53. The wastegate valve 54 is provided in the bypass pipe 36 that connects the upstream side and downstream side of the turbine 51 in the exhaust pipe 35, and is controlled by an electronic control unit 70. The blow-off valve 55 is provided in the bypass pipe 24 that connects the upstream side and downstream side of the compressor 52 in the intake pipe 23, and is controlled by the electronic control unit 70.

[0018] In this turbocharger 50, the opening degree of the wastegate valve 54 is adjusted to adjust the distribution ratio between the amount of exhaust gas flowing through the bypass pipe 36 and the amount of exhaust gas flowing through the turbine 51, thereby adjusting the rotational driving force of the turbine 51, adjusting the amount of air compressed by the compressor 52, and adjusting the supercharging pressure (intake pressure) of the engine 12. When the wastegate valve 54 is fully open, the engine 12 can operate in the same way as a naturally aspirated engine that does not have the turbocharger 50.

[0019] Furthermore, in the turbocharger 50, when the pressure downstream of the compressor 52 in the intake pipe 23 is somewhat higher than the pressure upstream of the intake pipe 23, the blow-off valve 55 opens to release the excess pressure downstream of the compressor 52. Note that the blow-off valve 55 may be a check valve that opens when the pressure downstream of the compressor 52 in the intake pipe 23 becomes somewhat higher than the pressure upstream of the intake pipe 23, instead of a valve controlled by the electronic control unit 70.

[0020] The intercooler 25 is disposed between the compressor 52 of the intake pipe 23 and the throttle valve 26. The intercooler 25 exchanges heat between the air compressed by the compressor 52 and cooling water of a cooling device (not shown).

[0021] As shown in Fig. 2, the electronic control unit 70 includes a microcomputer having a CPU 71, a ROM 72, a RAM 73, a flash memory 74, and input / output ports. Signals from various sensors are input to the electronic control unit 70 via the input ports. Examples of signals input to the electronic control unit 70 include a crank angle θcr from a crank position sensor 14a that detects the rotational position of the crankshaft 14 of the engine 12, a coolant temperature Tw from a water temperature sensor 15 that detects the temperature of the coolant of the engine 12, and a throttle opening θt from a throttle position sensor 26a that detects the position (opening) of the throttle valve 26. Other examples of signals input to the electronic control unit 70 include cam angles θci and θco from a cam position sensor 16 that detects the rotational position of an intake camshaft that opens and closes the intake valve 29 and the rotational position of an exhaust camshaft that opens and closes the exhaust valve 33. Other examples include the intake air amount Qa from the air flow meter 23a attached upstream of the throttle valve 26 of the intake pipe 23, the intake air temperature Ta from the intake air temperature sensor 23t attached upstream of the throttle valve 26 of the intake pipe 23, and the intake air pressure Pa from the intake air pressure sensor 23b attached upstream of the throttle valve 26 of the intake pipe 23. Other examples include the first downstream pressure Ps, which is the pressure of the gas at the throttle downstream portion 23d of the intake pipe 23, from the pressure sensor 27a attached to the surge tank 27, and the downstream temperature Ts, which is the temperature of the air at the throttle downstream portion 23d of the intake pipe 23, from the temperature sensor 27t attached to the surge tank 27. Other examples include the front air-fuel ratio AF1 from the front air-fuel ratio sensor 39a attached upstream of the purification device 37 of the exhaust pipe 35, and the rear air-fuel ratio AF2 from the rear air-fuel ratio sensor 39b attached between the purification device 37 and the purification device 38 of the exhaust pipe 35. Another example is the opening degree θegr of the EGR valve 44 from the opening degree sensor 45 that detects the opening degree of the EGR valve 44. Another example is the boost pressure Pc from the boost pressure sensor 23c attached between the compressor 52 of the intake pipe 23 and the intercooler 25.

[0022] Various control signals are output from the electronic control unit 70 via output ports. Examples of signals output from the electronic control unit 70 include a control signal to the throttle valve 26 of the engine 12, a control signal to the fuel injector 28, a control signal to the spark plug 31, and a control signal to the variable valve timing device 34. A control signal to the EGR valve 44 is also included. Examples of the signals output from the electronic control unit 70 include a control signal to the wastegate valve 54 and a control signal to the blow-off valve 55.

[0023] The electronic control unit 70 calculates the rotation speed Ne of the engine 12 based on the crank angle θcr of the crankshaft 14 from the crank position sensor 14a. The electronic control unit 70 also calculates a load factor KL (the ratio of the volume of air actually taken in one cycle to the stroke volume per cycle of the engine 12) based on the intake air amount Qa from the air flow meter 23a and the rotation speed Ne of the engine 12. Furthermore, the electronic control unit 70 calculates the opening and closing timings VTi, VTo of the intake valve 29 and the exhaust valve 33 based on the angles (θci-θcr), (θco-θcr) of the cam angles θci, θco of the intake camshaft and the exhaust camshaft from the cam position sensor 16 relative to the crank angle θcr of the crankshaft 14 from the crank position sensor 14a.

[0024] In an engine system 10 equipped with the engine state estimation device of the embodiment configured as described above, a CPU 71 of an electronic control unit 70 performs operation control of the engine 12 (intake air amount control, fuel injection control, ignition control, variable valve timing control), EGR control, and supercharging control based on the required load rate KL* of the engine 12. The intake air amount control will be described later. In the fuel injection control, the amount of fuel injected from the fuel injection valve 28 is controlled. In the ignition control, the ignition timing of the spark plug 31 is controlled. In the variable valve timing control, the opening and closing timing of the intake valve 29 and the exhaust valve 33 is controlled by the variable valve timing device 34. In the EGR control, the opening degree of the EGR valve 44 is controlled. In the supercharging control, the opening degree of the wastegate valve 54 is controlled.

[0025] Next, the intake air amount control in the engine device 10 of the embodiment will be described. In the intake air amount control, the load factor KL (the ratio of the volume of air actually taken in one cycle to the stroke volume per cycle of the engine 12) is set as the control load factor KLexe by upper limiting the load factor KL with the upper limit load factor KLmax (the smaller value of the load factor KL and the upper limit load factor KLmax is set as the control load factor KLexe), and the opening of the throttle valve 26 is adjusted so that the control load factor KLexe becomes the required load factor KL*. The load factor KL is basically calculated based on the intake air amount Qa from the air flow meter 23a and the rotation speed Ne of the engine 12. However, when the throttle opening θt becomes 0 due to deceleration while the supercharger 50 is performing supercharging, the accuracy of the detection value by the air flow meter 23a becomes poor due to the influence of the residual pressure due to supercharging, and the accuracy of the load factor KL becomes poor. Therefore, when the throttle opening θt becomes 0 due to deceleration while the turbocharger 50 is performing turbocharging, the load rate KL is derived from the intake pressure (pressure in the intake pipe 23) Pa from the intake pressure sensor 23b attached upstream of the throttle valve 26 of the intake pipe 23 and a load rate setting map. The load rate setting map is a map determined in advance by experiments, analysis, etc. as a relationship between the intake pressure Pa and the load rate KL when the engine 12 is burning properly. The upper limit load rate KLmax is calculated using an air model described later. In the embodiment, the intake air amount control using the load rate KL calculated from the intake air amount Qa from the air flow meter 23a and the rotation speed Ne of the engine 12 may be referred to as "LJ control". Also, the intake air amount control using the intake pressure Pa from the intake pressure sensor 23b attached upstream of the throttle valve 26 of the intake pipe 23 and the load rate setting map may be referred to as "DJ control".

[0026] Here, the air model will be described. In the engine device 10 of the embodiment, the CPU 71 of the electronic control unit 70 uses the air model of FIG. 3 to calculate (estimate) the throttle passing air amount mt, the second downstream pressure Pm, the downstream temperature Tm, the cylinder inflow air amount mci, the downstream volume Vm, and the cylinder filling air amount mcf. Here, the throttle passing air amount mt is the flow rate of air passing through the throttle valve 26 per unit time. The second downstream pressure Pm is the pressure of the gas at the throttle downstream portion 23d of the intake pipe 23 according to the current throttle opening θt. The downstream temperature Tm is the temperature of the air at the throttle downstream portion 23d. The cylinder inflow air amount mci is the flow rate of air flowing into the combustion chamber 30 per unit time (a value obtained by averaging the flow rate of air flowing from the throttle downstream portion 23d into the combustion chamber 30 of all cylinders). The downstream volume Vm is the volume of the throttle downstream portion 23d. The cylinder air charge amount mcf is the amount of air that is charged in the combustion chamber 30 when the intake valve 29 is closed. Of the calculated throttle passing air amount mt, second downstream pressure Pm, downstream temperature Tm, cylinder inflow air amount mci, downstream volume Vm, and cylinder air charge amount mcf, the cylinder air charge amount mcf is used to control the intake air amount of the engine 12.

[0027] The air model in Fig. 3 has a throttle model M10, an intake pipe model M20, and an intake valve model M30. The throttle model M10 receives the throttle opening θt, the intake air temperature Ta, the intake pressure Pa, and the second downstream pressure Pm. The throttle model M10 receives the throttle opening θt as a value detected by the throttle position sensor 26a. The intake air temperature Ta as a value detected by the intake air temperature sensor 23t. The intake pressure Pa as a value detected by the intake pressure sensor 23b. The second downstream pressure Pm as a value calculated by the intake pipe model M20. The throttle model M10 calculates the throttle passing air amount mt by substituting the throttle opening θt, the intake air temperature Ta, the intake pressure Pa, and the second downstream pressure Pm into the model formula of the throttle model M10, and outputs the calculated throttle passing air amount mt to the intake pipe model M20.

[0028] The intake pipe model M20 receives as input the intake air temperature Ta, the throttle air passing amount mt, the cylinder inflow air amount mci, and the downstream volume Vm. For the intake air temperature Ta, a value detected by the intake air temperature sensor 23t is input. For the throttle air passing amount mt, a value calculated by the throttle model M10 is input. For the cylinder inflow air amount mci, a value calculated by the intake valve model M30 is input. For the downstream volume Vm, a downstream volume base value Vm0 is input. The downstream volume base value Vm0 is a value determined in advance as a base value for the volume of the throttle downstream portion 23d (for example, a value at the time of completion of manufacturing the engine device 10). The intake pipe model M20 substitutes the intake air temperature Ta, the throttle passing air volume mt, the cylinder inflow air volume mci, and the downstream volume Vm into the model equation of the intake pipe model M20 to calculate the second downstream pressure Pm and the downstream temperature Tm, and outputs the calculated second downstream pressure Pm to the throttle model M10 and the intake valve model M30, and also outputs the calculated downstream temperature Tm to the intake valve model M30.

[0029] The intake valve model M30 receives the intake air temperature Ta, the engine speed Ne, the opening and closing timings VTi, VTo of the intake valve 29 and the exhaust valve 33, the second downstream pressure Pm, and the downstream temperature Tm. The intake air temperature Ta is inputted with a value detected by the intake air temperature sensor 23t. The engine speed Ne is inputted with a value calculated based on the crank angle θcr of the crankshaft 14 from the crank position sensor 14a. The opening and closing timings VTi, VTo of the intake valve 29 and the exhaust valve 33 are inputted with values ​​calculated based on the angles (θci-θcr), (θco-θcr) of the cam angles θci, θco of the intake camshaft and the exhaust camshaft from the cam position sensor 16 relative to the crank angle θcr of the crankshaft 14 from the crank position sensor 14a. The second downstream pressure Pm and the downstream temperature Tm are inputted with values ​​calculated by the intake pipe model M20. The intake valve model M30 substitutes the intake air temperature Ta, the rotation speed Ne, the opening and closing timings VTi, VTo of the intake valve 29 and the exhaust valve 33, the second downstream pressure Pm, and the downstream temperature Tm into the model equation of the intake valve model M30 to calculate the amount of air flowing into the cylinder mci, converts this into the amount of air filled in the cylinder mcf, and outputs it to the intake pipe model M20.

[0030] The throttle model M10, the intake pipe model M20, and the intake valve model M30 will be described in detail in this order. First, the throttle model M10 will be described in detail. The throttle model M10 calculates the throttle passing air amount mt using the throttle opening θt, the intake air temperature Ta, the intake air pressure Pa, and the second downstream pressure Pm, as shown in equation (1).

[0031]

number

[0032] In formula (1), "μ(θt)" is the flow coefficient in the throttle valve 26. In this embodiment, this flow coefficient μ(θt) is estimated by applying the throttle opening θt to a flow coefficient estimation map. Here, the flow coefficient estimation map is determined in advance by experiment or analysis as the relationship between the throttle opening θt and the flow coefficient μ(θt), and is stored in the flash memory 74. FIG. 4 is an explanatory diagram showing an example of the flow coefficient estimation map. As shown in the figure, the flow coefficient μ(θt) is set to be smaller as the throttle opening θt is larger.

[0033] In the formula (1), "A(θt)" is the opening cross-sectional area of ​​the throttle valve 26. In the embodiment, this opening cross-sectional area A(θt) is estimated by applying the throttle opening θt to a map for estimating the opening cross-sectional area. Here, the map for estimating the opening cross-sectional area is determined in advance by experiment or analysis as a relationship between the throttle opening θt and the opening cross-sectional area A(θt), and is stored in the flash memory 74. FIG. 5 is an explanatory diagram showing an example of the map for estimating the opening cross-sectional area. As shown in the figure, in a region where the throttle opening θt is less than a predetermined value θt1, the opening cross-sectional area A(θt) increases toward a predetermined value A1 as the throttle opening θt increases, and in a region where the throttle opening θt is equal to or greater than the predetermined value θt1, the opening cross-sectional area A(θt) is set to be constant at the predetermined value A1. In addition, the value μ(θt)·A(θt) may be estimated by applying the throttle opening θt to a predetermined relationship between the throttle opening θt and the value μ(θt)·A(θt) which is the product of the flow coefficient μ(θt) and the opening cross-sectional area A(θt).

[0034] In formula (1), "R" is a constant related to the gas constant. This constant R corresponds to the gas constant divided by the mass of gas (air) per mole. In formula (1), "Φ(Pm / Pa)" is a function obtained by formulas (2) and (3). In formulas (2) and (3), "κ" is the specific heat ratio. This specific heat ratio is set to a constant value. This function Φ(Pm / Pa) can be expressed as a map as shown in FIG. 6. Therefore, instead of formulas (2) and (3), the value of the function Φ(Pm / Pa) may be obtained by applying the second downstream pressure Pm and the intake pressure Pa to the map in FIG. 6.

[0035]

number

[0036] FIG. 7 is an explanatory diagram of the throttle model M10. The above-mentioned formulas (1) to (3) are obtained as follows. First, the pressure of the gas at the throttle upstream section 23u is the intake pressure Pa, the temperature of the gas at the throttle upstream section 23u is the intake air temperature Ta, and the pressure of the gas at the throttle downstream section 23d is the second downstream pressure Pm. Then, the law of conservation of mass, the law of conservation of energy, and the law of conservation of momentum are applied to the throttle model M10 in FIG. 7, and further, the gas state equation, the equation of specific heat ratio, and the Mayer's relational equation are used. As a result, formulas (1) to (3) are obtained.

[0037] Next, the details of the intake pipe model M20 will be described. As shown in formulas (4) and (5), the intake pipe model M20 calculates the second downstream pressure Pm and the downstream temperature Tm using the intake air temperature Ta, the throttle passing air amount mt, the cylinder inflow air amount mci, the downstream volume Vm, the constant R, and the specific heat ratio κ.

[0038]

number

[0039] FIG. 8 is an explanatory diagram of the intake pipe model M20. As can be seen from FIG. 8, if the total gas amount (total air amount) in the throttle downstream section 23d is M, the time change amount of the total gas amount M is equal to the difference between the flow rate of the gas flowing into the throttle downstream section 23d, i.e., the throttle passing air amount mt, and the flow rate of the gas flowing out from the throttle downstream section 23d, i.e., the cylinder inflow air amount mci. Therefore, according to the law of conservation of mass, formula (6) is obtained. Then, formula (4) is obtained by formula (6) and the state equation of the gas in the throttle downstream section 23d (Pm·Vm=M·R·Tm).

[0040]

number

[0041] Also, the amount of change over time in the energy M·Cv·Tm of the gas at the throttle downstream section 23d is equal to the difference between the energy of the gas flowing into the throttle downstream section 23d and the energy of the gas flowing out from the throttle downstream section 23d. Therefore, if the temperature of the gas flowing into the throttle downstream section 23d is the intake air temperature Ta, and the temperature of the gas flowing out from the throttle downstream section 23d is the downstream temperature Tm, then equation (7) is obtained according to the law of conservation of energy. Here, in equation (7), "Cp" is the specific heat at constant pressure of air, and "Cv" is the specific heat at constant volume of air. Then, equation (5) is obtained by combining equation (7) with the above-mentioned equation of state of gas.

[0042]

number

[0043] Next, the intake valve model M30 will be described in detail. The intake valve model M30 calculates the amount of air flowing into the cylinder mci using the intake air temperature Ta, the second downstream pressure Pm, and the downstream temperature Tm, as shown in equation (8). Here, in equation (8), "a" and "b" are determined based on the rotation speed Ne of the engine 12 and the opening and closing timings VTi, VTo of the intake valve 29 and the exhaust valve 33.

[0044]

number

[0045] 9 is an explanatory diagram of the intake valve model M30. In general, the cylinder air charge amount mcf is determined when the intake valve 29 is closed, and is proportional to the pressure in the combustion chamber 30 at that time. In addition, the pressure in the combustion chamber 30 when the intake valve 29 is closed can be considered to be equal to the pressure of the gas upstream of the intake valve 29, specifically, the second downstream pressure Pm. Therefore, the cylinder air charge amount mcf can be approximated as being proportional to the second downstream pressure Pm.

[0046] Here, if the flow rate of air flowing into the combustion chamber 30 of all cylinders from the throttle downstream portion 23d per predetermined time (for example, 720° of the crank angle θcr) is divided (averaged) by the predetermined time to give the cylinder inflow air amount mci, then since the cylinder filling air amount mcf is proportional to the second downstream pressure Pm as described above, it is considered that the cylinder inflow air amount mci is also proportional to the second downstream pressure Pm. From this, the above-mentioned formula (8) is obtained based on theory and empirical rules. In formula (8), "a" is a proportionality coefficient, and "b" is an adaptation value representing the burnt gas remaining in the combustion chamber 30. This adaptation value is obtained by dividing the amount of burnt gas remaining in the combustion chamber 30 when the exhaust valve 33 is closed by the time ΔT180° required for the crankshaft 14 to rotate 180°. Here, 180° means the angle obtained by dividing 720°, the angle that the crankshaft 14 rotates in one cycle (four strokes: intake, compression, expansion, and exhaust), by the number of cylinders in the engine 12, which is four. Also, during actual operation of the engine 12, the downstream temperature Tm may change significantly. For this reason, in equation (8), "a·Pm-b" is multiplied by "Ta / Tm", which is derived based on theory and empirical rules, as a correction that takes into account changes in the downstream temperature Tm.

[0047] FIG. 10 is an explanatory diagram of the cylinder inflow air amount mci and the cylinder filling air amount mcf. In FIG. 10, the horizontal axis is the crank angle θcr of the crankshaft 14, and the vertical axis is the flow rate of air that actually flows from the throttle downstream portion 23d into the combustion chamber 30 of each cylinder per unit time. In the embodiment, since a four-cylinder engine 12 is used, the intake valves 29 open in the order of, for example, the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. Then, as shown in the figure, air flows from the throttle downstream portion 23d into the combustion chamber 30 of each cylinder according to the opening amount of the intake valve 29 corresponding to each cylinder. For example, the flow rate of air that flows from the throttle downstream portion 23d into the combustion chamber 30 of each cylinder is as shown by the dashed line in FIG. 10. Taking this displacement into account, the flow rate of air flowing from the throttle downstream portion 23d into the combustion chambers 30 of all cylinders is as shown by the solid line in Fig. 10. Furthermore, the cylinder air filling amount mcf of the first cylinder is as shown by the hatching in Fig. 10.

[0048] On the other hand, the average flow rate of air flowing into the combustion chamber 30 of all cylinders from the throttle downstream portion 23d is the cylinder inflow air amount mci, as shown by the dashed line in FIG. 10. The cylinder inflow air amount mci is multiplied by the time ΔT180° to obtain the cylinder charging air amount mcf. Therefore, the cylinder inflow air amount mci calculated by the intake valve model M30 is multiplied by the time ΔT180° to obtain the cylinder charging air amount mcf. More specifically, in consideration of the fact that the cylinder charging air amount mcf is proportional to the pressure when the intake valve 29 is closed, the cylinder inflow air amount mci when the intake valve 29 is closed is multiplied by the time ΔT180° to obtain the cylinder charging air amount mcf.

[0049] Next, an upper limit load rate setting process for setting the upper limit load rate KLmax will be described. Fig. 11 is a block diagram showing an example of the upper limit load rate setting process. The upper limit load rate setting process includes a guard coefficient setting process S100, an smoothing process S102, multiplication processes S104 and S106, an addition process S108, and a conversion process S110.

[0050] The guard coefficient setting process S100 receives the throttle opening θt and the rotation speed Ne. The throttle opening θt is a value detected by the throttle position sensor 26a. The rotation speed Ne is a value calculated based on the crank angle θcr of the crankshaft 14 from the crank position sensor 14a. The guard coefficient setting process S100 sets a guard coefficient (upper limit coefficient) Cg corresponding to the throttle opening θt and the rotation speed Ne from a map Map. FIG. 12 is an explanatory diagram showing an example of the map Map. The guard coefficient Cg is set to be larger than 1 and smaller when the rotation speed Ne is equal to or larger than a predetermined rotation speed Neref compared to when the rotation speed Ne is less than the predetermined rotation speed Neref. When the rotation speed Ne of the engine 12 is low, that is, when the piston 32 is moving slowly, the amount of air taken into the cylinder does not decrease significantly even if poor combustion occurs. Taking these into consideration, the predetermined rotation speed Neref is set to the lower limit of the rotation speed at which the amount of air drawn into the cylinder is smaller when poor combustion occurs in the engine 12 than when proper combustion is occurring. The guard coefficient Cg is set to gradually increase when the throttle opening θt reaches the predetermined opening θtref when the rotation speed Ne is equal to or higher than the predetermined rotation speed Neref. This is based on the fact that the smaller the throttle opening θt (the opening cross-sectional area of ​​the throttle valve 26), the greater the flow sensitivity due to individual variations in the throttle valve 26.

[0051] The guard coefficient Cg calculated by the guard coefficient setting process S100 is input to the smoothing process S102. The smoothing process S102 is a process for smoothing the change in the guard coefficient Cg in consideration of the response delay of the cylinder inflow air amount mci with respect to the change in the throttle opening θt.

[0052] The multiplication process S104 receives the cylinder inflow air amount mci, the transition coefficient Ct, and the guard coefficient Cg. The cylinder inflow air amount mci is input with a value calculated by the intake valve model M30. The transition coefficient Ct is set to a value of 1 when DJ control is being executed as the intake air amount control, and is set to a value of 0 when LJ control is being executed as the intake air amount control. The guard coefficient Cg is input with a value set by the smoothing process S102. The multiplication process S104 outputs an upper guard value mmax2 obtained by multiplying the cylinder inflow air amount mci by the transition coefficient Ct and the guard coefficient Cg to the addition process S108. Therefore, the upper guard value mmax2 is calculated by the following equation (9). The upper guard value mmax2 is a value obtained by multiplying the cylinder inflow air amount mci by the transition coefficient Ct when DJ control is being executed, and is a value of 0 when LJ control is being executed.

[0053] mmax2=mci·Ct·Cg·(9)

[0054] The multiplication process S106 receives the cylinder inflow air amount mci or a value (1-Ct) obtained by subtracting a transition coefficient Ct from the value 1. The cylinder inflow air amount mci receives a value calculated by the intake valve model M30. The transition coefficient Ct is set to a value of 1 when DJ control is being executed as the intake air amount control, and is set to a value of 0 when LJ control is being executed as the intake air amount control. The multiplication process S104 outputs an upper limit guard value mmax1 obtained by multiplying the cylinder inflow air amount mci by a value obtained by subtracting the transition coefficient Ct from the value 1 to the addition process S108. Therefore, the upper limit guard value mmax1 is calculated by the following formula (10). The upper limit guard value mmax1 becomes the cylinder inflow air amount mci when LJ control is being executed, and becomes a value of 0 when DJ control is being executed.

[0055] mmax1 = mci (1 - Ct) (10)

[0056] The upper limit guard values ​​mmax1 and mmax2 are input to the addition process S108. The upper limit guard value mmax1 is input with the value calculated by the multiplication process S106. The upper limit guard value mmax2 is input with the value calculated by the multiplication process S104. The addition process S108 calculates the upper limit guard value mmax by adding the upper limit guard value mmax2 to the upper limit guard value mmax1, and outputs the calculated upper limit guard value mmax to the conversion process S110. Therefore, the upper limit guard value mmax is calculated by the following formula (11). When the LJ control is being executed, the upper limit guard value mmax2 becomes 0, so the upper limit guard value mmax becomes the upper limit guard value mmax1 (the amount of air flowing into the cylinder mci). When the DJ control is being executed, the upper limit guard value mmax1 becomes 0, so the upper limit guard value mmax becomes the upper limit guard value mmax2.

[0057] mmax = mmax1 + mmax2 (11)

[0058] The upper limit guard value mmax is input to the conversion process S110. The value calculated in the addition process S108 is input as the upper limit guard value mmax. The conversion process S110 calculates an upper limit load rate KLmax by converting the calculated upper limit guard value mmax into a load rate. When LJ control is being performed, the upper limit guard value mmax becomes the upper limit guard value mmax1 (the amount of air inflow into the cylinder mci), and therefore the upper limit load rate KLmax becomes a value obtained by converting the upper limit guard value mmax1 (the amount of air inflow into the cylinder mci) into a load rate. When DJ control is being performed, the upper limit guard value mmax becomes the upper limit guard value mmax2, and therefore the upper limit load rate KLmax becomes a value obtained by converting the upper limit guard value mmax2 into a load rate.

[0059] By calculating the upper limit load rate KLmax in this manner, when LJ control is being performed, the load rate KL calculated using the intake air amount Qa from the airflow meter 23a is upper-guarded by the upper limit load rate KLmax (in-cylinder inflow air amount mci), and set as the control load rate KLexe, and the opening of the throttle valve 26 is adjusted so that the control load rate KLexe becomes the required load rate KL*. In LJ control, since there is a small deviation between the load rate KL calculated using the intake air amount Qa from the airflow meter 23a and the upper limit load rate KLmax which is the in-cylinder inflow air amount mci, a value close to the load rate KL calculated using the intake air amount Qa from the airflow meter 23a is set as the control load rate KLexe, and the opening of the throttle valve 26 is adjusted.

[0060] When the DJ control is being performed, the load rate KL set using the intake pressure Pa from the intake pressure sensor 23b is set as the control load rate KLexe with the upper limit guarded by the upper limit load rate KLmax (upper limit guard value mmax2), and the opening degree of the throttle valve 26 is adjusted so that the control load rate KLexe becomes the required load rate KL*. In the DJ control, as described above, the load rate KL set using the intake pressure Pa from the intake pressure sensor 23b may become excessively larger than the actual load rate. Therefore, when the DJ control is performed while the engine 12 is experiencing poor combustion, if the load rate KL set using the intake pressure Pa from the intake pressure sensor 23b is set as the control load rate KLexe, excessive fuel may be injected, resulting in a rich state, and the poor combustion may continue. In the embodiment, when the DJ control is being performed, the load rate KL is set as the control load rate KLexe with the upper limit guarded by the upper limit load rate KLmax (upper limit guard value mmax2), thereby preventing excessive fuel from being injected and resulting in a rich state. This makes it possible to prevent the poor combustion in the engine 12 from continuing.

[0061] In the engine system 10 equipped with the engine state estimation device of the embodiment described above, the estimated in-cylinder inflow air amount mci and a guard coefficient (upper limit coefficient) Cg based on the rotation speed Ne of the engine 12 are used to calculate an upper limit guard value mmax2 of the in-cylinder inflow air amount mci, and the smaller of the load rate KL based on the intake pressure Pa and the upper limit load rate KLmax is set (estimated) as the control load rate KLexe, thereby suppressing the continuation of poor combustion in the engine 12.

[0062] In the engine device 10 equipped with the engine state estimation device of the embodiment, the multiplication process S104 calculates the value obtained by multiplying the cylinder inflow air amount mci, the transition coefficient Ct, and the guard coefficient Cg as the upper limit guard value mmax2. However, when the upper limit guard value mmax2 is less than the load rate KL set using the intake pressure Pa in the case of transition from LJ control to DJ control, if the load rate KL is immediately upper-limit guarded with the upper limit load rate KLmax (upper limit guard value mmax2) and set as the control load rate KLexe, the actual load rate may suddenly change. In order to suppress such a sudden change in the load rate, when the upper limit guard value mmax2 is less than the load rate KL in the case of transition from LJ control to DJ control, the transition coefficient Ct may be gradually changed from the value 0 to the value 1. Similarly, when the upper limit guard value mmax2 is less than the load rate KL set using the intake pressure Pa in the case of transition from DJ control to LJ control, the transition coefficient Ct may be gradually changed from the value 1 to the value 0.

[0063] In the engine system 10 equipped with the engine state estimation device of the embodiment, the engine 12 is provided with a turbocharger 50. However, the engine system may not be provided with the turbocharger 50 and the above-described DJ control may be constantly performed as the intake air amount control.

[0064] In the engine system 10 equipped with the engine state estimation device of the embodiment, the smaller of the load factor KL based on the intake pressure Pa and the upper limit load factor KLmax obtained by converting the set upper limit guard value mmax into a load factor is estimated as the control load factor KLexe. However, the smaller of the intake air amount based on the intake pressure Pa and the set upper limit guard value mmax may be estimated as the intake air amount, and the throttle opening θt may be adjusted in the intake air amount control so that the estimated intake air amount becomes the target intake air amount Qa* corresponding to the target torque Te* of the engine 12.

[0065] In the engine device 10 of the embodiment and the modified example, the engine 12 is configured as a four-cylinder engine, but may be configured as a six-cylinder engine, eight-cylinder engine, etc. Also, the engine 12 is provided with the EGR device 40, but may not be provided with the EGR device 40.

[0066] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on solving the problems will be described below. In the embodiment, the electronic control unit 70 corresponds to the "engine state estimating device."

[0067] The correspondence between the main elements of the Examples and the main elements of the invention described in the Summary of the Problem column does not limit the elements of the invention described in the Summary of the Problem column, since the Examples are examples for specifically explaining the mode for implementing the invention described in the Summary of the Problem column. In other words, the interpretation of the invention described in the Summary of the Problem column should be based on the description in that column, and the Examples are merely a specific example of the invention described in the Summary of the Problem column.

[0068] Although the form for carrying out the present invention has been described above using examples, the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms without departing from the scope of the gist of the present invention. [Industrial Applicability]

[0069] The present invention can be used in the manufacturing industry of engine state estimation devices. [Explanation of symbols]

[0070] 10 engine device, 12 engine, 14 crankshaft, 14a crank position sensor, 15 water temperature sensor, 16 cam position sensor, 22 air cleaner, 23 intake pipe, 23a air flow meter, 23b intake pressure sensor, 23c boost pressure sensor, 23d throttle downstream portion, 23t intake temperature sensor, 23u throttle upstream portion, 24 bypass pipe, 25 intercooler, 26 throttle valve, 26a throttle position sensor, 27 surge tank, 27a pressure sensor, 27t temperature sensor, 28 fuel injector, 29 intake valve, 30 combustion chamber, 31 spark plug, 32 piston, 33 exhaust valve, 34 variable valve timing device, 35 exhaust pipe, 36 bypass pipe, 37, 38 purification device, 39a front air-fuel ratio sensor, 39b rear air-fuel ratio sensor, 40 EGR device, 42 EGR pipe, 44 EGR valve, 45 opening sensor, 50 turbocharger, 51 turbine, 52 compressor, 53 rotating shaft, 54 wastegate valve, 55 blow-off valve, 70 electronic control unit, 71 CPU, 72 ROM, 73 RAM, 74 flash memory.

Claims

[Claim 1] 1. An engine state estimating device that is mounted on an engine device together with an engine having a throttle valve disposed in an intake pipe, and estimates an intake air amount of the engine from a pressure in the intake pipe, comprising: an amount of air flowing into the cylinder from an opening degree of the throttle valve, and an upper limit value of the amount of intake air is set using the estimated amount of air flowing into the cylinder and an upper limit coefficient based on a rotation speed of the engine; The intake air amount is estimated to be the smaller value of the provisional intake air amount based on the pressure of the intake pipe and the set upper limit value. Engine state estimation device.

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