JP7635700B2 - Engine state estimation device - Google Patents

Description

The present invention relates to an engine state estimation device, and more specifically, to an engine state estimation device that is mounted in an engine device together with an engine equipped with a throttle valve.

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 the intake pipe has been proposed (see, for example, Patent Document 1). In this device, until a first predetermined time has elapsed since the engine is started, the engine intake air volume 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 intake air volume is estimated by Kalman filter calculation from the intake air volume detected by the intake air volume sensor. Since the engine intake air volume 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 intake air volume by Kalman filter calculation, it is said that the intake air volume can be estimated more accurately.

JP 2018-173067 A

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, and the pressure inside the cylinder becomes lower than when proper combustion is occurring. When the exhaust valve opens in this state, air flows into the cylinder from the exhaust pipe, and the pressure inside the cylinder increases. When the intake valve opens, air flows from the cylinder to the intake pipe, and the amount of air taken into the cylinder becomes small. Therefore, if the intake air amount is estimated using the same method as when poor combustion does not occur when poor combustion occurs, 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.

The main purpose of the engine state estimation device of the present invention is to prevent the continuation of poor combustion in the engine.

The engine state estimation device of the present invention employs the following means to achieve the above-mentioned main objective.

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 intake air amount 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 gist of the present invention is that the intake air amount is estimated to be the smaller value between a tentative intake air amount based on the pressure in the intake pipe and the set upper limit value.

In the engine state estimation device of the present invention, the amount of air flowing into the cylinder through the throttle valve opening is estimated, 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 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 engine from continuing to suffer from poor combustion.

In such an 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 it 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, a more appropriate upper limit value can be set.

In the engine state estimation device of the present invention, the engine is equipped with a supercharger having a compressor arranged upstream of the throttle valve in the intake pipe, and a first estimation process is performed to estimate the intake air amount from the opening of the throttle valve, and a second estimation process is performed to estimate the intake air amount from the pressure in the intake pipe when supercharging by the supercharger is being performed and the throttle valve is closed due to deceleration. 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 is 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. In this way, a sudden change in the intake air amount can be suppressed.

1 is a configuration diagram showing an outline of the configuration of an engine system 10 including a state estimation device according to an embodiment of the present invention. 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. FIG. 2 is an explanatory diagram illustrating an example of an air model. FIG. 4 is an explanatory diagram showing an example of a map for estimating a flow coefficient; FIG. 11 is an explanatory diagram showing an example of an opening cross-sectional area estimation map; FIG. 13 is an explanatory diagram showing a function Φ(Pm/Pa). FIG. 2 is an explanatory diagram of a throttle model M10. FIG. 2 is an explanatory diagram of an intake pipe model M20. FIG. 2 is an explanatory diagram of an intake valve model M30. 4 is an explanatory diagram of the amount of air flowing into the cylinder (mci) and the amount of air charged into the cylinder (mcf). FIG. FIG. 13 is a block diagram showing an example of an upper limit load rate setting process. FIG. 2 is an explanatory diagram showing an example of a map.

Next, we will explain how to implement the present invention using examples.

Figure 1 is a schematic diagram showing the configuration of an engine device 10 equipped with an engine state estimation device as one embodiment of the present invention, and Figure 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. As shown in Figures 1 and 2, the engine device 10 of the embodiment includes an engine 12 and an electronic control unit 70. This engine device 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 estimation device of the embodiment.

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, which passes through a throttle valve 26 and a surge tank 27 in that 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 upstream of the throttle valve 26 of the intake pipe 23 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, this 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. The exhaust gas discharged from the combustion chamber 30 to the exhaust pipe 35 through the exhaust valve 33 is discharged to the outside air through the purification devices 37, 38 and is also supplied (recirculated) to the surge tank 27 of the intake pipe 23 through the exhaust gas recirculation device (hereinafter referred to as the "EGR (Exhaust Gas Recirculation) device") 40.

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

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.

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 the 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.

In this turbocharger 50, the opening of the wastegate valve 54 is adjusted to adjust the ratio of the exhaust gas flowing through the bypass pipe 36 to the 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 without the turbocharger 50.

In addition, in the turbocharger 50, when the pressure downstream of the compressor 52 in the intake pipe 23 is somewhat higher than the pressure upstream, the blow-off valve 55 opens to release the excess pressure downstream of the compressor 52. Note that instead of a valve controlled by the electronic control unit 70, 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.

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

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 through the input ports. Examples of signals input to the electronic control unit 70 include the crank angle θcr from the crank position sensor 14a that detects the rotational position of the crankshaft 14 of the engine 12, the cooling water temperature Tw from the water temperature sensor 15 that detects the temperature of the cooling water of the engine 12, and the throttle opening θt from the throttle position sensor 26a that detects the position (opening) of the throttle valve 26. Cam angles θci and θco from the cam position sensor 16 that detects the rotational position of the intake camshaft that opens and closes the intake valve 29 and the rotational position of the exhaust camshaft that opens and closes the exhaust valve 33 can also be mentioned. 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 installed between the compressor 52 of the intake pipe 23 and the intercooler 25.

Various control signals are output from the electronic control unit 70 via the output port. 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 injection valve 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 signals include a control signal to the wastegate valve 54 and a control signal to the blow-off valve 55.

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 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) 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 and VTo of the intake valve 29 and the exhaust valve 33 based on the angles (θci-θcr) and (θco-θcr) of the cam angles θci and 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.

In the engine device 10 equipped with the engine state estimation device of the embodiment configured in this way, the CPU 71 of the 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 variable valve timing device 34 controls the opening and closing timing of the intake valve 29 and the exhaust valve 33. 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.

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 rate 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 to the upper limit load rate KLmax as the control load rate KLexe (the smaller value of the load rate KL and the upper limit load rate KLmax is set to 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*. The load rate 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 deteriorates due to the influence of the residual pressure due to supercharging, and the accuracy of the load rate KL deteriorates. Therefore, when the throttle opening θt is set to 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". In addition, 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 KL derived from the load rate setting map may be referred to as "DJ control".

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 in 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 in 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 (the average value of 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, the second downstream pressure Pm, the downstream temperature Tm, the cylinder inflow air amount mci, the downstream volume Vm, and the cylinder air charge amount mcf, the cylinder air charge amount mcf is used to control the intake air amount of the engine 12.

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, intake air temperature Ta, intake pressure Pa, and second downstream pressure Pm. The throttle opening θt is input as a value detected by the throttle position sensor 26a. The intake air temperature Ta is input as a value detected by the intake air temperature sensor 23t. The intake pressure Pa is input as a value detected by the intake pressure sensor 23b. The second downstream pressure Pm is input as a value calculated by the intake pipe model M20. The throttle model M10 calculates the throttle passing air volume mt by substituting the throttle opening θt, intake air temperature Ta, intake pressure Pa, and second downstream pressure Pm into the model formula of the throttle model M10, and outputs the calculated throttle passing air volume mt to the intake pipe model M20.

The intake pipe model M20 receives as input the intake temperature Ta, the throttle air flow rate mt, the cylinder inflow air flow rate mci, and the downstream volume Vm. The intake temperature Ta is input as a value detected by the intake temperature sensor 23t. The throttle air flow rate mt is input as a value calculated by the throttle model M10. The cylinder inflow air flow rate mci is input as a value calculated by the intake valve model M30. The downstream volume Vm is input as the downstream volume base value Vm0. The downstream volume base value Vm0 is a value that is predetermined as a base value for the volume of the throttle downstream section 23d (for example, the 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 air flow rate mt, the cylinder inflow air flow rate mci, and the downstream volume Vm into the model formula 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.

The intake valve model M30 receives the intake air temperature Ta, the rotation speed Ne, the opening and closing timings VTi and 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 rotation 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 and VTo of the intake valve 29 and the exhaust valve 33 are inputted with values calculated based on the cam angles θci and θco of the intake camshaft and the exhaust camshaft from the cam position sensor 16 (θci-θcr), (θco-θcr) 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 temperature Ta, the rotation speed Ne, the opening and closing timing 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 formula of the intake valve model M30 to calculate the amount of air flowing into the cylinder mci, converts this to the amount of air filled in the cylinder mcf, and outputs it to the intake pipe model M20.

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

In equation (1), "μ(θt)" is the flow coefficient at 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. 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 increases.

In 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 the opening cross-sectional area estimation map. Here, the opening cross-sectional area estimation map is determined in advance by experiment or analysis as the 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 opening cross-sectional area estimation map. As shown in the figure, in the region where the throttle opening θt is less than a predetermined value θt1, the opening cross-sectional area A(θt) increases toward the predetermined value A1 as the throttle opening θt increases, and in the 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) as the product of the flow coefficient μ(θt) and the opening cross-sectional area A(θt).

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 mol. 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.

Figure 7 is an explanatory diagram of the throttle model M10. The above equations (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 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 Figure 7, and further, the gas state equation, the equation of specific heat ratio, and the Mayer relational equation are used. In this way, equations (1) to (3) are obtained.

Next, the intake pipe model M20 will be described in detail. As shown in equations (4) and (5), the intake pipe model M20 calculates the second downstream pressure Pm and downstream temperature Tm using the intake air temperature Ta, the throttle air flow rate mt, the inflow air flow rate mci into the cylinder, the downstream volume Vm, the constant R, and the specific heat ratio κ.

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

The amount of change over time in the energy M, Cv, and Tm of the gas in 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 of air at constant pressure, and "Cv" is the specific heat of air at constant volume. Then, equation (5) is obtained by combining equation (7) with the above-mentioned equation of state of the gas.

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 engine 12 rotation speed Ne and the opening and closing timings VTi, VTo of the intake valve 29 and exhaust valve 33.

Figure 9 is an explanatory diagram of the intake valve model M30. In general, the amount of air filled in the cylinder 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 amount of air filled in the cylinder mcf can be approximated as being proportional to the second downstream pressure Pm.

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 inflow air amount mci into the cylinder, then, as described above, since the cylinder air charge amount mcf is proportional to the second downstream pressure Pm, it is considered that the inflow air amount mci into the cylinder 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 720° that the crankshaft 14 rotates in one cycle (four strokes: intake, compression, expansion, and exhaust) divided 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.

Figure 10 is an explanatory diagram of the cylinder inflow air amount mci and the cylinder filling air amount mcf. In Figure 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 into the combustion chamber 30 of each cylinder from the throttle downstream portion 23d 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 into the combustion chamber 30 of each cylinder from the throttle downstream portion 23d according to the opening amount of the intake valve 29 corresponding to each cylinder. For example, the flow rate of air flowing into the combustion chamber 30 of each cylinder from the throttle downstream portion 23d is as shown by the dashed line in Figure 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 charge amount mcf of cylinder 1 is as shown by the hatching in FIG. 10.

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 inflow air amount mci into the cylinder, as shown by the dashed line in FIG. 10. Then, the cylinder inflow air amount mci is multiplied by the time ΔT180° to obtain the cylinder inflow air amount mcf. Therefore, the cylinder inflow air amount mci calculated by the intake valve model M30 can be calculated by multiplying the cylinder inflow air amount mci by the time ΔT180°. More specifically, considering that the cylinder inflow 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 inflow air amount mcf.

Next, the 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.

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 the 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 the value 1 and smaller when the rotation speed Ne is equal to or greater than the 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 factors 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 less when poor combustion occurs in the engine 12 compared to 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 greater 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.

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 that smooths the change in the guard coefficient Cg, taking into account the response delay of the cylinder inflow air amount mci to the change in the throttle opening θt.

The cylinder inflow air amount mci, the transition coefficient Ct, and the guard coefficient Cg are input to the multiplication process S104. 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 performed as the intake air amount control, and is set to a value of 0 when LJ control is being performed 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 the upper guard value mmax2, which is the multiplication of the cylinder inflow air amount mci, 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 formula (9). The upper guard value mmax2 is the multiplication of the cylinder inflow air amount mci and the transition coefficient Ct when DJ control is being performed, and is the value of 0 when LJ control is being performed.

mmax2=mci・Ct・Cg ・・・(9)

The multiplication process S106 receives the cylinder inflow air amount mci or a value (1-Ct) obtained by subtracting the transition coefficient Ct from the value 1. 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 performed as the intake air amount control, and is set to a value of 0 when LJ control is being performed as the intake air amount control. The multiplication process S104 outputs the upper limit guard value mmax1, which is obtained by multiplying the cylinder inflow air amount mci by the 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 is the cylinder inflow air amount mci when LJ control is being performed, and is set to a value of 0 when DJ control is being performed.

mmax1=mci・(1-Ct) ・・・(10)

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 LJ control is being performed, the upper limit guard value mmax2 is set to 0, so the upper limit guard value mmax is set to the upper limit guard value mmax1 (the amount of air flowing into the cylinder mci). When DJ control is being performed, the upper limit guard value mmax1 is set to 0, so the upper limit guard value mmax is set to the upper limit guard value mmax2.

mmax=mmax1+mmax2 ・・・(11)

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 the 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 flowing into the cylinder mci), so the upper limit load rate KLmax becomes the value obtained by converting the upper limit guard value mmax1 (the amount of air flowing 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, so the upper limit load rate KLmax becomes the value obtained by converting the upper limit guard value mmax2 into a load rate.

By calculating the upper limit load rate KLmax in this way, when LJ control is being performed, the load rate KL calculated using the intake air amount Qa from the airflow meter 23a is set to the upper limit load rate KLmax (in-cylinder inflow air amount mci) and the control load rate KLexe is set to the upper limit guarded value, 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 the difference 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, is small, the control load rate KLexe is set to a value close to the load rate KL calculated using the intake air amount Qa from the airflow meter 23a, and the opening of the throttle valve 26 is adjusted.

When DJ control is being performed, the load rate KL set using the intake pressure Pa from the intake pressure sensor 23b is set to the control load rate KLexe by upper limit guarding with the upper limit load rate KLmax (upper limit guard value mmax2), and the opening of the throttle valve 26 is adjusted so that the control load rate KLexe becomes the required load rate KL*. In DJ control, as described above, the load rate KL set using the intake pressure Pa from the intake pressure sensor 23b may be excessively larger than the actual load rate. Therefore, when DJ control is performed while poor combustion is occurring in the engine 12, if the load rate KL set using the intake pressure Pa from the intake pressure sensor 23b is set to the control load rate KLexe, excessive fuel is injected, resulting in a rich state, and the poor combustion may continue. In this embodiment, when DJ control is being performed, the load rate KL is set to the upper limit load rate KLmax (upper limit guard value mmax2) and the control load rate KLexe is set to the upper limit load rate KLmax, which prevents excessive fuel from being injected and creates a rich state. This prevents the continuation of poor combustion in the engine 12.

In the engine device 10 equipped with the engine state estimation device of the embodiment described above, the estimated in-cylinder air inflow amount mci and the guard coefficient (upper limit coefficient) Cg based on the engine 12 rotation speed Ne are used to calculate the upper limit guard value mmax2 of the in-cylinder air inflow 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.

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 amount of air flowing into the cylinder 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 by 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.

In the engine device 10 equipped with the engine state estimation device of the embodiment, the engine 12 is equipped with a turbocharger 50. However, the above-mentioned DJ control may be constantly performed as the intake air amount control without the turbocharger 50.

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

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 or eight-cylinder engine. Also, the engine 12 is equipped with an EGR device 40, but may not be equipped with an EGR device 40.

The following explains the relationship between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem. In the embodiment, the electronic control unit 70 corresponds to the "engine state estimation device."

The correspondence between the main elements of the Examples and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the Examples are examples for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving 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 Means for Solving the Problem column.

The above describes the form for carrying out the present invention using examples, but 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 invention.

The present invention can be used in industries such as the manufacturing of engine state estimation devices.

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 downstream of throttle, 23t intake air temperature sensor, 23u upstream of throttle, 24 bypass pipe, 25 intercooler, 26 throttle valve, 26a throttle position sensor, 27 surge tank, 27a pressure sensor, 27t temperature sensor, 28 fuel injection valve, 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 Supercharger, 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 (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 intake air amount 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;
a provisional intake air amount based on the pressure in the intake pipe and a set upper limit value, whichever is smaller, being estimated as the intake air amount.

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