Engine state estimation device

Abstract

To suppress continuation of combustion failure in an engine.SOLUTION: An intake air amount estimation device of an engine loaded on an engine device together with an engine including a throttle valve disposed on an intake pipe and estimating an intake air amount of the engine on the basis of a pressure of the intake pipe, estimates an amount of cylinder inflow air passing from an opening of the throttle valve, sets an upper limit value of the intake air amount by using the estimated cylinder inflow air amount and an upper limit coefficient based on a rotation frequency of the engine, and estimates a smaller value of a temporal intake air amount based on the pressure of the intake pipe and the set upper limit value, as the intake air amount.SELECTED DRAWING: Figure 1

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 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] However, in the above-mentioned engine state estimation device, when fuel injection to the engine is stopped, the pressure inside the cylinder drops significantly when the piston descends during the expansion stroke. In this state, when the exhaust valve opens during the exhaust stroke, air flows into the cylinder from the exhaust pipe, and the pressure inside the cylinder rises and becomes higher than the pressure inside the intake pipe. Then, when the intake valve opens during the subsequent intake stroke, air flows from the cylinder into the intake pipe, and the pressure inside the intake pipe rises. Therefore, if the intake air amount is estimated using the same method as when fuel is injected into the engine, the deviation between the estimated intake air amount and the actual intake air amount becomes large.

[0005] The main object of the engine state estimating device of the present invention is to accurately estimate the intake air amount when fuel injection into the engine is stopped. [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 in an intake pipe, and estimates an intake air amount of the engine based on a pressure in the intake pipe, comprising: When a command to stop fuel injection to the engine is issued, a base intake air amount as the intake air amount estimated based on the pressure in the intake pipe is corrected by the correction amount based on a map showing the relationship between the rotation speed of the engine, the pressure in the intake pipe, and the correction amount, and the intake air amount is estimated as the intake air amount. The gist of the present invention is as follows.

[0008] In the engine state estimation device of the present invention, the intake air amount is estimated by correcting a base intake air amount as the intake air amount estimated based on the intake pipe pressure with a correction amount based on a map showing the relationship between the engine speed, the intake pipe pressure, and the correction amount. The inventors have found that the intake air amount in the cylinder when fuel injection to the engine is stopped varies depending on the engine speed and the intake pipe pressure. Therefore, when a command to stop fuel injection to the engine is issued, the intake air amount when fuel injection to the engine is stopped can be accurately estimated by correcting a base intake air amount as the intake air amount estimated based on the intake pipe pressure with a correction amount based on a map showing the relationship between the engine speed, the intake pipe pressure, and the correction amount.

[0009] In the engine state estimating device of the present invention, the base intake air amount may be estimated as the intake air amount until a predetermined time has elapsed since the instruction to stop fuel injection to the engine, and a value obtained by correcting the base intake air amount with the correction amount may be estimated as the intake air amount after the predetermined time has elapsed since the instruction to stop fuel injection to the engine. It takes a certain amount of time from when fuel injection to the engine is stopped until the pressure in the intake pipe increases due to the stop of fuel injection. Therefore, the intake air amount can be estimated more accurately by estimating the base intake air amount as the intake air amount until a predetermined time has elapsed since the instruction to stop fuel injection to the engine, and estimating the value obtained by correcting the base intake air amount with the correction amount as the intake air amount after the predetermined time has elapsed since the instruction to stop fuel injection to the engine. Here, the "predetermined time" may be, for example, the time required for the crankshaft of the engine to rotate 720 degrees after the instruction to stop fuel injection to the engine.

[0010] In this case, the engine may have multiple cylinders, and when the predetermined time has elapsed since a command to stop fuel injection to the engine was given, the correction amount may be increased from a value of 0 by an amount of change calculated by multiplying a base correction amount based on the map by the reciprocal of the number of cylinders of the engine, and then, when the predetermined time has elapsed, the base correction amount may be set as the correction amount. In this way, the intake air amount can be estimated with higher accuracy.

[0011] Furthermore, in the engine state estimating device of the present invention, the engine is equipped with a turbocharger having a compressor arranged upstream of the throttle valve in the intake manifold, and a first estimation process is performed to estimate the intake air amount from an opening degree of the throttle valve, and a second estimation process is performed to estimate the intake air amount from the pressure in the intake manifold when supercharging by the turbocharger is being performed and the throttle valve is closed due to deceleration, and when an instruction to stop fuel injection to the engine is given while the second estimation process is being performed, a value obtained by correcting the base intake air amount by the correction amount may be estimated as the intake air amount. [Brief description of the drawings]

[0012] [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 a block diagram showing an example of a load factor estimation process. [Figure 4] FIG. 4 is an explanatory diagram for explaining the change over time of the FC timing and the intake pressure Pa for each cylinder. [Diagram 5] FIG. 4 is an explanatory diagram showing an example of a correction amount setting map MAP1 when the intake pressure Pa is set to a predetermined pressure Pref. [Figure 6] FIG. 11 is an explanatory diagram showing an example of a correction amount setting map MAP2 when the intake pressure Pa is set to a predetermined pressure Pref. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, a mode for carrying out the present invention will be described using examples. EXAMPLES

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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 timings VTi, VTo of the intake valve 29 and the exhaust valve 33, respectively, while maintaining the operating angle, by changing the phase of the intake cam relative to the intake camshaft and the phase of the exhaust cam relative to the exhaust camshaft.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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).

[0022] As shown in Fig. 2, the electronic control unit 70 is configured as 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Next, the intake air amount control in the engine system 10 equipped with the engine state estimation device of the embodiment will be described. In the intake air amount control, a load factor (the ratio of the volume of air actually taken in one cycle to the stroke volume per cycle of the engine 12) KL is estimated, and the opening of the throttle valve 26 is adjusted so that the estimated load factor KL becomes the required load factor KL*. The load factor KL is basically estimated 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 detection accuracy of the intake air amount Qa by the air flow meter 23a deteriorates due to the influence of the residual pressure due to supercharging, and the load factor KL cannot be estimated accurately. Therefore, when the throttle opening θt becomes 0 due to deceleration while the turbocharger 50 is performing supercharging, the load factor KL is estimated 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 factor setting map. The load factor setting map is a map determined in advance through experiments, analysis, etc. as a relationship between the intake pressure Pa of the engine 12 and the load factor KL when fuel injection to the engine 12 is continued (when fuel injection to the engine 12 is not stopped) when the throttle opening θt becomes 0 due to deceleration while the turbocharger 50 is performing supercharging. In the embodiment, the intake air amount control using the load factor KL estimated 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 estimated from a load rate setting map is sometimes referred to as "DJ control."

[0027] Next, the operation of the engine device 10 equipped with the engine state estimation device of the embodiment, in particular the operation of estimating the load factor KL when an instruction to stop fuel injection to the engine 12 is given during DJ control, will be described. Fig. 3 is a block diagram showing an example of a load factor estimation process executed by the electronic control unit 70. The load factor estimation process is repeatedly executed when an instruction to stop fuel injection to the engine 12 is given during DJ control. The load factor estimation process includes a conversion process S10, a correction amount calculation process S12, a cylinder number correction process S14, and an addition process S16.

[0028] The intake pressure Pa is input to the conversion process S10. The intake pressure Pa is a value detected by the intake pressure sensor 23b. The conversion process S10 estimates a base load factor KLb from the intake pressure (pressure inside the intake pipe 23) Pa from the intake pressure sensor 23b and a load factor setting map, and outputs the base load factor KLb to the addition process S16.

[0029] The correction amount calculation process S12 receives a fuel cut flag Ffc, a rotation speed Ne, an opening / closing timing VTi of the intake valve 29, an opening / closing timing VTo of the exhaust valve 33, and an intake pressure Pa. The fuel cut flag Ffc is set to a value of 1 when fuel supply to the engine 12 is stopped, and is set to a value of 0 when fuel supply to the engine 12 is being executed. The rotation speed Ne is input with a value calculated based on the crank angle θcr of the crankshaft 14 from the crank position sensor 14a. The opening / closing timing VTi of the intake valve 29 is input with a value calculated based on the angle (θci-θcr) of the cam angle θci of the intake camshaft from the cam position sensor 16 relative to the crank angle θcr of the crankshaft 14 from the crank position sensor 14a. The opening / closing timing VTo of the exhaust valve 33 is input with a value calculated based on the angle (θco-θcr) of the cam angle θco of 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. As the intake pressure Pa, a value detected by the intake pressure sensor 23b is input.

[0030] The correction amount calculation process S12 calculates a correction amount dKL for correcting the base load ratio KLb when fuel injection is stopped for all cylinders of the engine 12. The correction amount dKL is set to a value of 0 until the elapsed time tfc from when the fuel cut flag Ffc changes from a value of 0 to a value of 1 elapses a predetermined time tfcref. Here, the predetermined time tfcref is the time (720 CA time) required for the crankshaft 14 of the engine 12 to rotate 720 degrees from when the fuel cut flag Ffc changes from a value of 0 to a value of 1, that is, from when an instruction to stop fuel injection to the engine 12 is given. FIG. 4 is a schematic diagram showing the time change of the fuel cut timing (FC timing) and the intake pressure Pa for each cylinder. In the figure, #1 to #4 indicate the ignition order numbers of the four cylinders of the engine 12. When an instruction to stop fuel injection is given (time t0), the fuel injection of each cylinder is stopped in the ignition order. Therefore, the intake pressure Pa does not rise immediately after the fuel injection stop command is issued, but starts to rise from time t1, which is 720 CA hours (predetermined time tfcref) after time t0. Taking into consideration such a change in the intake pressure Pa, the correction amount dKL is set to a value of 0 until the elapsed time tfc after the fuel cut flag Ffc changes from value 0 to value 1 has passed the predetermined time tfcref.

[0031] After the elapsed time tfc has passed the predetermined time tfcref, the correction amount dKL is set using the correction amount setting maps MAP1 and MAP2, the rotation speed Ne, the opening / closing timing VTi of the intake valve 29, the opening / closing timing VTo of the exhaust valve 33, and the intake pressure Pa. FIG. 5 is an explanatory diagram showing an example of the correction amount setting map MAP1 when the intake pressure Pa is set to the predetermined pressure Pref. FIG. 6 is an explanatory diagram showing an example of the correction amount setting map MAP2 when the intake pressure Pa is set to the predetermined pressure Pref. The correction amount dKL is calculated as the sum of the intake side correction amount dKLvti set from the correction amount setting map MAP1, the rotation speed Ne, the intake pressure Pa, and the opening / closing timing VTi, and the exhaust side correction amount dKLvto set from the correction amount setting map MAP2, the rotation speed Ne, the intake pressure Pa, and the opening / closing timing VTo. The correction amount setting map MAP1 is prepared for each intake pressure Pa by obtaining, through experiments, analysis, etc., the difference between the load factor when fuel injection is continued under constant intake pressure Pa and the load factor when fuel injection is stopped when the opening / closing timing VTo is a predetermined angle VToref. The correction amount setting map MAP2 is prepared for each intake pressure Pa by obtaining, through experiments, analysis, etc., the difference between the load factor when fuel injection is continued under constant intake pressure Pa and the load factor when fuel injection is stopped when the opening / closing timing VTi is a predetermined angle VTiref. The predetermined angles VTiref and VToref are values ​​previously set through experiments, analysis, etc. as the opening / closing timing VTi of the intake valve 29 and the opening / closing timing VTo of the exhaust valve 33 that allow the engine 12 to be operated efficiently.

[0032] The intake side correction amount dKLvti is set to 0 when the rotation speed Ne is equal to or lower than the rotation speed Ne1, and is set to be larger when the rotation speed Ne is high compared to when it is low (the higher the rotation speed Ne, the larger the correction amount). This is because the amount of air flowing from the exhaust side due to inertia is larger when the rotation speed Ne is high compared to when it is low (the higher the rotation speed Ne, the larger the correction amount). Also, the intake side correction amount dKLvti is set to be larger when the advance amount from the predetermined angle VTiref of the opening / closing timing VTi of the intake valve 29 is large compared to when it is small (the larger the advance amount from the predetermined angle VTiref of the opening / closing timing VTi, the larger the correction amount). This is because the interference of the exhaust stroke during the intake stroke is larger when the advance amount from the predetermined angle VTiref of the opening / closing timing VTi of the intake valve 29 is large compared to when it is small (the larger the advance amount from the predetermined angle VTiref of the opening / closing timing VTi, the larger the correction amount). Furthermore, the intake side correction amount dKLvti is set to be smaller when the intake pressure Pa is high (as the intake pressure Pa becomes higher) compared to when it is low. This is because when the intake pressure Pa is high (as the intake pressure Pa becomes higher), the difference with the pressure inside the cylinder becomes smaller compared to when it is low (as the intake pressure Pa becomes higher), and the amount of air flowing from inside the cylinder to the intake pipe 23 becomes smaller.

[0033] The exhaust side correction amount dKLvto is set to 0 when the rotation speed Ne is equal to or lower than the predetermined rotation speed Nvto, and is set to be larger when the rotation speed Ne is high compared to when it is low (the higher the rotation speed Ne, the larger the correction amount). This is because when the rotation speed Ne is high compared to when it is low (the higher the rotation speed Ne), the amount of air flowing from the exhaust side due to inertia is larger, and when the advance amount from the predetermined angle VToref of the opening and closing timing VTo of the exhaust valve 33 is large compared to when it is small (the larger the advance amount from the predetermined angle VToref of the opening and closing timing VTo, the larger the amount of air flowing from the exhaust side is). The predetermined rotation speed Nvto is set to be larger when the advance amount from the predetermined angle VToref of the opening and closing timing VTo of the exhaust valve 33 is small compared to when it is large (the smaller the advance amount from the predetermined angle VToref of the opening and closing timing VTo, the larger the correction amount). This is because, when the advance amount from the predetermined angle VToref of the opening / closing timing VTo of the exhaust valve 33 is large, the exhaust valve opens under a condition where the pressure inside the cylinder is lower due to the piston's descent, and the amount of air flowing from the exhaust side is larger than when the advance amount from the predetermined angle VToref of the opening / closing timing VTo is small (the greater the advance amount from the predetermined angle VToref of the opening / closing timing VTo is), and the amount of air flowing from the exhaust side is larger. In addition, the exhaust side correction amount dKLvto is set to be larger when the advance amount from the predetermined angle VToref of the opening / closing timing VTo of the exhaust valve 33 is large compared to when it is small (the greater the advance amount from the predetermined angle VToref of the opening / closing timing VTo is small). This is because, when the advance amount from the predetermined angle VToref of the opening / closing timing VTo of the exhaust valve 33 is large, the exhaust valve opens under a condition where the pressure inside the cylinder is lower due to the piston's descent, and the amount of air flowing from the exhaust side is larger than when the advance amount from the predetermined angle VToref of the opening / closing timing VTo is small (the greater the advance amount from the predetermined angle VToref of the opening / closing timing VTo is small). In addition, the exhaust side correction amount dKLvto is set to be smaller when the intake pressure Pa is high compared to when it is low (the higher the intake pressure Pa is). This is because when the intake pressure Pa is high, the difference with the pressure inside the cylinder becomes smaller compared to when it is low (the higher the intake pressure Pa), and the amount of air flowing from inside the cylinder to the intake pipe 23 becomes smaller.

[0034] The correction amount dKL is input to the cylinder number correction process S14. The correction amount dKL is a value input from the correction amount calculation process S12. The cylinder number correction process S14 multiplies the correction amount dKL by the inverse (in the embodiment, 1 / 4) of the number of cylinders (four in the embodiment) of the engine 12 to set a change amount ΔdKLc, and sets the correction amount dKLc so that it increases from a value 0 by the change amount ΔdKLc every 180 CA hours from the time t0 and reaches the correction amount dKL after 720 CA hours from the time t0, and outputs the correction amount dKLc to the addition process S16. The reason for setting the correction amount dKLc in this manner is that, as shown in FIG. 4, the intake pressure Pa increases stepwise every 180 CA hours after the elapsed time tfc has passed a predetermined time tfcref, and the correction amount dKLc is made to correspond to such an increase in the intake pressure Pa.

[0035] The base load factor KLb and the correction amount dKLc are input to the addition process S16. The base load factor KLb is a value estimated by the conversion process S10. The correction amount dKLc is a value set by the number of cylinders correction process S14. The addition process S16 estimates the value obtained by adding the correction amount dKLc to the base load factor KLb as the load factor KL. By performing such processing, the load factor KL when fuel injection to the engine 12 is stopped, i.e., the intake air amount, can be accurately estimated.

[0036] According to the engine system 10 equipped with the engine state estimating device of the embodiment described above, when a command is given to stop fuel injection to the engine 12, the load rate KL can be estimated with high accuracy by estimating, as the load rate KL, a value obtained by correcting the base load rate KLb as a load rate estimated based on the intake pressure Pa with the correction amount dKLc based on the correction amount setting maps MAP1 and MAP2 which show the relationship between the rotation speed Ne of the engine 12, the intake pressure Pa, the opening / closing timing VTi, VTo, and the correction amount dKL.

[0037] In the engine device 10 equipped with the engine state estimation device of the embodiment, after the elapsed time tfc has passed a predetermined time tfcref, the correction amount dKL is calculated as the sum of an intake side correction amount dKLvti set from a correction amount setting map MAP1, the rotation speed Ne, the intake pressure Pa, and the opening / closing timing VTi, and an exhaust side correction amount dKLvto set from a correction amount setting map MAP2, the rotation speed Ne, the intake pressure Pa, and the opening / closing timing VTo. However, the relationship between the rotation speed Ne, the intake pressure Pa, the opening / closing timing VTi, VTo, and the correction amount dKL may be set as a correction amount setting map MAPv, and the correction amount dKL may be set using the rotation speed Ne, the intake pressure Pa, the opening / closing timing VTi, VTo, and the correction amount setting map MAPv.

[0038] In the engine system 10 equipped with the engine state estimation device of the embodiment, the correction amount dKLc is calculated using correction amount setting maps MAP1 and MAP2 that indicate the relationship between the rotation speed Ne, intake pressure Pa, opening / closing timings VTi and VTo, and the correction amount dKL of the engine 12. However, when the engine 12 does not have the variable valve timing device 34, the correction amount dKLc may be calculated using a correction amount setting map MAP that indicates the relationship between the rotation speed Ne, intake pressure Pa, and the correction amount dKL of the engine 12, instead of the correction amount setting maps MAP1 and MAP2.

[0039] In the engine device 10 equipped with the engine state estimation device of the embodiment, in the correction amount calculation process S12, the correction amount dKL is set to a value of 0 until the elapsed time tfc after the fuel cut flag Ffc changes from a value of 0 to a value of 1 passes a predetermined time tfcref, and after the elapsed time tfc passes the predetermined time tfcref, the correction amount dKL is set using the correction amount setting maps MAP1 and MAP2, the rotation speed Ne, the opening / closing timing VTi of the intake valve 29, the opening / closing timing VTo of the exhaust valve 33, and the intake pressure Pa. However, the correction amount dKL may be set using the correction amount setting maps MAP1 and MAP2, the rotation speed Ne, the opening / closing timing VTi of the intake valve 29, the opening / closing timing VTo of the exhaust valve 33, and the intake pressure Pa immediately after the fuel cut flag Ffc changes from a value of 0 to a value of 1.

[0040] In the engine system 10 equipped with the engine state estimation device of the embodiment, the engine 12 is provided with a supercharger 50. However, the engine system may not be provided with the supercharger 50 and the above-described DJ control may be constantly performed as the intake air amount control.

[0041] In the engine system 10 equipped with the engine state estimation device of the embodiment, the load factor KL is estimated. However, instead of the load factor KL, another parameter indicating the intake air amount may be estimated, or the intake air amount itself may be estimated.

[0042] In the engine device 10 of the embodiment and the modified example equipped with the engine state estimation device, 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 equipped with the EGR device 40, but may not be equipped with the EGR device 40.

[0043] 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."

[0044] 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.

[0045] 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]

[0046] The present invention can be used in the manufacturing industry of engine state estimation devices. [Explanation of symbols]

[0047] 1 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 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 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 in an intake pipe, and estimates an intake air amount of the engine based on a pressure in the intake pipe, comprising: Until a predetermined time has elapsed since a command to stop fuel injection to the engine is issued, a base intake air amount as the intake air amount estimated based on the pressure of the intake pipe is estimated as the intake air amount, and after the predetermined time has elapsed since a command to stop fuel injection to the engine is issued, a value obtained by correcting the base intake air amount by the correction amount based on a map showing the relationship between the engine speed, the pressure of the intake pipe, and the correction amount is estimated as the intake air amount. Engine state estimation device.

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