JP2023144256A - Maximum filling efficiency estimation method and apparatus for internal combustion engine - Google Patents

Abstract

To accurately estimate a maximum filling efficiency obtainable under a present engine revolution speed, considering an intake air density influencing a turbocharger.SOLUTION: An internal combustion engine has a turbocharger. A maximum filling efficiency obtainable under a present engine revolution speed for engine torque control is calculated on the basis of the engine revolution speed and a maximum intake air density. The maximum intake air density is obtained from a table defining a relationship between the engine revolution speed and maximum filling efficiency for every intake air density. In a characteristic L1 of a standard intake air density, an increase rate of the maximum filling efficiency increases at a point P1 corresponding to a turbo intercept revolution speed N1. In a low intake air density, the turbo intercept revolution speed changes to a high revolution speed side, that is, toward N2, hence, in a maximum filling efficiency characteristic L2, an increase rate increasingly changes at a point P2. Therefore, an estimation accuracy is better than a characteristic L3 that does not take a change in the intercept revolution speed into consideration.SELECTED DRAWING: Figure 6

Description

In an internal combustion engine equipped with a turbocharger, the present invention provides maximum charging efficiency estimation for estimating the maximum charging efficiency that can be obtained under the engine speed based on the engine speed, for example, for torque control of the internal combustion engine. METHODS AND APPARATUS.

At high altitudes or when the intake air temperature is high, the intake air density changes. The maximum filling efficiency that can be obtained under a certain engine speed is then influenced by the intake air density. Patent Document 1 describes calculating the maximum basic torque of the engine based on the engine rotation speed and atmospheric pressure.

Japanese Patent Application Publication No. 2011-137435

In an internal combustion engine equipped with a turbocharger, for example, in the process where the engine speed gradually increases and the maximum charging efficiency increases accordingly, the maximum charging efficiency increases relatively rapidly at a certain point. It shows a tendency to start. In other words, the engine speed at which the rate of increase in maximum charging efficiency changes corresponds to the engine speed at which supercharging by the turbocharger can be achieved.

According to the new findings of the present inventors, the engine speed at which the rate of increase in maximum charging efficiency changes in connection with such supercharging changes depending on the intake air density. For example, if the intake air density is lower than the standard state under the assumption that the throttle valve is fully open, the rotational speed of the turbocharger driven by exhaust energy tends to decrease. Therefore, the engine speed at which the turbocharger can provide supercharging becomes relatively high.

It is generally known that if the intake air density is different, the charging efficiency will be different even if the volumetric efficiency is the same, but the engine speed at which the turbocharger can obtain the supercharging effect as described above is the intake air density. Until now, it has not been taken into account that this changes depending on the Therefore, the accuracy of estimating the maximum charging efficiency based on the engine speed becomes low. Patent Document 1 does not include any description regarding such matters.

This invention provides a method for estimating the maximum charging efficiency of an internal combustion engine that estimates the maximum charging efficiency that can be obtained at an engine speed based on the engine speed in an internal combustion engine equipped with a turbocharger. , the maximum filling efficiency is determined according to predetermined characteristics using engine speed and intake air density as parameters. Here, the above-mentioned characteristics are set such that the engine speed at which the rate of increase in maximum charging efficiency increases with respect to the increase in engine speed becomes higher as the intake air density becomes lower.

According to this invention, the estimation of the maximum charging efficiency based on the engine speed of an internal combustion engine equipped with a turbocharger becomes more accurate when the intake air density differs from the standard value, such as in high altitudes, extremely cold regions, or tropical regions. can do well.

FIG. 1 is a configuration explanatory diagram showing an example of an internal combustion engine to which the present invention is applied. Functional block diagram of engine torque control. A more detailed functional block diagram of the maximum engine torque calculation section. 5 is a flowchart showing the flow of processing for calculating maximum filling efficiency. A characteristic diagram showing characteristics of intercept rotation speed. FIG. 3 is a characteristic diagram showing the characteristics of maximum filling efficiency with respect to engine speed and intake air density.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows the system configuration of an automobile internal combustion engine 1 to which the present invention is applied. This internal combustion engine 1 is a four-stroke cycle spark-ignition internal combustion engine equipped with a turbocharger 2, and includes a pair of intake valves 4 and a pair of exhaust valves 5 arranged on the ceiling wall surface of each cylinder 3. A spark plug 6 is disposed in the center surrounded by the intake valve 4 and the exhaust valve 5. A fuel injection valve 7 that supplies fuel into the cylinder 3 is provided below the intake valve 4 . The ignition timing of the spark plug 6 and the injection timing and injection amount of fuel by the fuel injection valve 7 are controlled by an engine controller 9. Note that the type of fuel injection device is not limited to the in-cylinder direct injection type, but may be of a port injection type.

The intake valve 4 and the exhaust valve 5 are equipped with variable valve timing mechanisms 18 and 19 that can change the opening timing and closing timing of each. The variable valve timing mechanisms 18 and 19 may be of any type, but for example, a mechanism that retards the phase of the camshaft relative to the phase of the crankshaft may be used. Note that the variable valve timing mechanisms 18 and 19 are not essential components in the present invention.

The intake passage 11 connected to the combustion chamber 10 via the intake valve 4 has an intake collector 11a, and an electronic valve whose opening degree is controlled by a control signal from the engine controller 9 is provided upstream of the intake collector 11a. A controlled throttle valve 12 is provided. A compressor 2a of the turbocharger 2 is located upstream of the throttle valve 12, and an air flow meter 14 for detecting the amount of intake air and an air cleaner 15 are provided upstream of the compressor 2a. For example, a water-cooled intercooler 16 is provided between the compressor 2a and the throttle valve 12. Further, a recirculation valve 17 is provided to communicate the discharge side and suction side of the compressor 2a. This recirculation valve 17 is opened during deceleration when the throttle valve 12 is closed.

A turbine 2b of the turbocharger 2 is installed in an exhaust passage 20 connected to the combustion chamber 10 via an exhaust valve 5, and a pre-catalyst device 21 consisting of a three-way catalyst and a three-way catalyst are installed downstream of the turbine 2b. A coated exhaust particulate filter (GPF) 22 is provided, respectively. An air-fuel ratio sensor 23 for detecting an air-fuel ratio is arranged in the exhaust passage 20 upstream of the turbine 2b. The turbine 2b includes a wastegate valve 24 that bypasses part of the exhaust gas depending on the boost pressure to control the boost pressure. The wastegate valve 24 is of an electric type whose opening degree is controlled by the engine controller 9.

Further, as an exhaust gas recirculation device, an exhaust gas recirculation passage 25 is provided which recirculates part of the exhaust gas from the exhaust passage 20 to the intake passage 11. For example, one end of the exhaust gas recirculation passage 25 is connected between the pre-catalyst device 21 and the exhaust particulate filter 22 in the exhaust passage 20, and the other end of the exhaust gas recirculation passage 25 is connected to a position upstream of the compressor 2a in the intake passage 11. ing. The exhaust gas recirculation passage 25 includes, for example, a water-cooled EGR gas cooler 27 that cools the recirculated exhaust gas, and an EGR valve 28 that controls the amount of exhaust gas recirculation. The opening degree of the EGR valve 28 is controlled by the engine controller 9.

In addition to the air flow meter 14 and air-fuel ratio sensor 23, the engine controller 9 includes a crank angle sensor 31 for detecting engine speed, a water temperature sensor 32 for detecting cooling water temperature, and an accelerator pedal operated by the driver. an accelerator opening sensor 33 that detects the amount of depression; a vehicle speed sensor 34 that directly or indirectly detects vehicle speed; an atmospheric pressure sensor 35 that detects atmospheric pressure; and an intake air temperature that detects intake air temperature (in other words, outside temperature). Detection signals from sensors such as a sensor 36 and a boost pressure sensor 37 that detects boost pressure are input. Based on these detection signals, the engine controller 9 controls the fuel injection amount and injection timing, the ignition timing, the opening degree of the throttle valve 12, the opening degree of the waste gate valve 24, the vibration timing by the variable valve timing mechanisms 18 and 19, and the EGR valve. The opening degree of 28, etc. are optimally controlled.

Next, engine torque control, which is a main part of the present invention, and maximum charging efficiency estimation, which is the basis thereof, will be explained.

FIG. 2 is a functional block diagram showing the engine torque control function realized by the engine controller 9. As shown in FIG. The engine torque control function is configured to include a maximum engine torque calculation section 41, a target engine torque calculation section 42, and an engine torque control section 43, as shown in the figure.

The maximum engine torque calculation unit 41 estimates the maximum engine torque that can be output by the internal combustion engine 1 under the current environment, and as described later, calculates the maximum engine torque that can be obtained under the current engine speed. After estimating the efficiency, the maximum engine torque that the internal combustion engine 1 can output is calculated based on this maximum charging efficiency.

The target engine torque calculation unit 42 calculates the driver's requested torque based on the amount of accelerator pedal depression by the driver, the requested torque requested from other controllers of the vehicle, and the automatic driving function (for example, cruise control that follows the vehicle in front). The target engine torque is determined by arbitrating various demands such as the required torque required by the control system, etc.). The target engine torque output here is limited to the maximum engine torque that the internal combustion engine 1 can output at that time, which is estimated or calculated by the maximum engine torque calculation section 41.

In order to realize the target engine torque determined by the target engine torque calculation unit 42, the engine torque control unit 43 uses engine torque control devices (for example, the throttle valve 12, the wastegate valve 24, the fuel injection device, determining and operating target values for the ignition system, variable valve timing mechanisms 18, 19, EGR valve 28, etc.);

In other words, the output of the internal combustion engine 1 is controlled on a torque basis, and at this time, by determining in advance the maximum engine torque that can be output at that time, it is possible to perform appropriate torque control without causing any discomfort. .

FIG. 3 shows a more detailed functional block diagram of the maximum engine torque calculation section 41. The maximum engine torque calculation section 41 includes a maximum charging efficiency calculation section 51, an indicated torque calculation section 52, an engine friction correction section 53, and further includes an intake air density calculation section 54.

The intake air density calculation unit 54 receives the intake air temperature and atmospheric pressure as input and calculates the intake air density at that time. Altitude obtained from map information of a car navigation system may be used instead of atmospheric pressure. The intake air density may be simply determined by regarding either the intake air temperature or the atmospheric pressure as a fixed value.

The maximum filling efficiency calculation unit 51 receives the engine rotational speed and intake air density at that time and estimates or calculates the maximum filling efficiency that can be obtained under the engine rotational speed. Additionally, in the illustrated example, the maximum charging efficiency is corrected based on the engine system operating state. The engine system operating state refers to various engine system states that affect charging efficiency; for example, in the illustrated example, the operating state of the variable valve timing mechanisms 18 and 19, the particulate accumulation state of the exhaust particulate filter 22, etc. can be mentioned.

The indicated torque calculation unit 52 calculates the maximum indicated engine torque from the maximum charging efficiency estimated by the maximum charging efficiency calculation unit 51 and the ignition efficiency. Further, an engine protection required torque provided to protect the internal combustion engine 1 is input to the indicated torque calculation unit 52, and the maximum indicated engine torque is limited by this engine protection required torque.

The engine friction correction unit 53 applies correction to the maximum indicated engine torque based on engine friction. By subtracting the torque due to friction from the maximum indicated engine torque, the maximum engine torque that the internal combustion engine 1 can output is obtained.

In one embodiment, the maximum filling efficiency calculation unit 51 calculates the maximum filling efficiency using a three-dimensional map in which the corresponding maximum filling efficiency is assigned using the engine rotation speed and the intake air density as parameters. More specifically, we have a large number of tables for each intake air density in which the maximum filling efficiency corresponding to the engine speed is assigned to each intake air density, and by appropriate interpolation calculations, we can calculate the engine speed and intake air density at that time. Calculate the maximum filling efficiency corresponding to .

FIG. 4 is a flowchart showing the processing in the maximum filling efficiency calculation section 51 and the intake air density calculation section 54. In step 1, the engine speed at that time is read, and in step 2, engine system operating conditions that affect charging efficiency, such as the operating conditions of the variable valve timing mechanisms 18 and 19 and the particulate accumulation state of the exhaust particulate filter 22, are read. . Next, in step 3, the atmospheric pressure and intake air temperature detected by the atmospheric pressure sensor 35 and the intake air temperature 36 are read, and in step 4, the intake air density is calculated based on the atmospheric pressure and intake air temperature. Next, in step 5, a table corresponding to the intake air density is selected, and in step 6, the maximum filling efficiency value corresponding to the engine rotational speed is determined based on this table. Then, in step 7, a correction or correction is made in accordance with the operating state of the engine system, and the corrected value is output as the maximum charging efficiency that can be obtained under the engine speed at that time.

Here, the relationship between the engine speed and the maximum charging efficiency in each table for each intake air density is determined, for example, by simulation, but in addition to the fact that the mass of the same volume of air in the cylinder 3 changes depending on the intake air density. , consider the effect that the engine rotational speed at which the turbocharger 2 can obtain the supercharging effect (in other words, the engine rotational speed at which the supercharging effect begins assuming that the throttle valve 12 is fully open) changes depending on the intake air density. It is determined by the characteristics.

FIG. 5 is a characteristic diagram showing the relationship between the engine speed at which the turbocharger 2 can obtain a supercharging effect (hereinafter referred to as the turbo intercept speed for convenience) and the intake air density. As shown in the figure, the lower the intake air density, the higher the turbo intercept rotation speed (rpm), which changes linearly. For example, if the intake air density is lower than the standard state under the assumption that the throttle valve is fully open, the rotational speed of the turbocharger 2 driven by exhaust energy tends to decrease, so that the turbocharger 2 cannot obtain a supercharging effect. The engine speed at which this can be done becomes relatively high.

Figure 6 shows the characteristics of a three-dimensional map using engine speed, intake air density, and maximum filling efficiency as parameters. It shows the relationship with efficiency. Line L1 shows the characteristic of maximum filling efficiency at standard intake air density (for example, intake air density at a temperature of 15° C. and an altitude of 0 m). As shown in the figure, the overall trend is that the maximum charging efficiency increases as the engine speed increases from a low engine speed equivalent to the idle speed, and the maximum charging efficiency peaks at a certain engine speed. After that, the maximum charging efficiency decreases as the engine speed increases.

Here, if we pay attention to the first half of the characteristic that shows an increasing tendency, the rate of increase in the maximum filling efficiency increases and changes at a certain point P1. That is, the characteristic line L1 showing an increasing tendency has a point P1 which is a singular point, and the slope of the line L1 corresponding to the amount of change in maximum filling efficiency becomes relatively sharp at the point P1. This point P1 corresponds to the turbo intercept rotation speed mentioned above. In other words, since it is possible to obtain a supercharging effect by the turbocharger 2 on the higher rotation side than the turbo intercept rotation speed, the maximum charging efficiency increases relatively rapidly with the turbo intercept rotation speed as a boundary.

Line L2 shows the characteristic of maximum filling efficiency when the intake air density is low, such as at high altitudes. Here, since the mass of the same volume of air decreases according to the intake air density, the overall trend is that the maximum filling efficiency is smaller by the amount corresponding to the intake air density than the maximum filling efficiency characteristic shown by line L1. shows. Further, the present invention has a characteristic that takes into consideration that the above-mentioned turbo intercept rotation speed becomes a relatively high engine rotation speed when the intake air density is low. For example, the turbo intercept rotation speed, which is N1 with a standard intake air density, becomes a relatively high engine rotation speed shown as N2 due to the low intake air density. Therefore, in the characteristic line L2, the maximum charging efficiency increases relatively slowly with respect to the increase in the engine speed up to a point P2 corresponding to the turbo intercept speed N2. Then, at a point P2 where it becomes possible to obtain a supercharging effect by the turbocharger 2, the rate of increase in the maximum charging efficiency increases relatively greatly.

A line L3 shown as a reference is a characteristic (characteristic determined by simulation) of the maximum filling efficiency at a low intake air density when a change in the turbo intercept rotation speed according to the intake air density is not considered. Here, it is assumed that the turbo intercept rotation speed remains at N1 even if the intake air density is low, so the characteristic is such that the rate of increase in the maximum charging efficiency increases at point P3. In other words, the characteristics are set as if the characteristics of the line L1 were translated downward in parallel on the diagram. Therefore, if the maximum charging efficiency is estimated based on the engine speed along such characteristic line L3, the estimation accuracy will be low. In the range of engine rotation speeds in which the line L3 deviates from the line L2, the maximum charging efficiency and the maximum engine torque that can be outputted are expected to be excessively large. Therefore, for example, when the driver depresses the accelerator pedal greatly, the engine torque that the driver expects cannot be obtained, which may cause a sense of discomfort.

In this way, in the above embodiment, the maximum charging efficiency is estimated based on the engine speed by taking into account the change in the turbo intercept speed depending on the intake air density, so the estimation accuracy is increased and the engine torque is adjusted more appropriately. control can be realized.

Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, a table is provided that specifies the relationship between engine speed and maximum charging efficiency for each intake air density. Any type of calculation means that takes into account the change depending on the density and can obtain the maximum filling efficiency as an output by inputting the engine speed and the intake air density may be used. Further, the internal combustion engine targeted by the present invention is not limited to the configuration illustrated in FIG. 1 .

1... Internal combustion engine 2... Turbocharger 9... Engine controller 12... Throttle valve 33... Accelerator opening sensor 35... Atmospheric pressure sensor 36... Intake air temperature sensor 41... Maximum engine torque calculation section 42... Target engine torque calculation section 43... Engine Torque control section 51... Maximum filling efficiency calculation section 52... Indicated torque calculation section 53... Engine friction correction section 54... Intake density calculation section

Claims (4)

In an internal combustion engine maximum charging efficiency estimation method for estimating the maximum charging efficiency that can be obtained under the engine speed based on the engine speed in an internal combustion engine equipped with a turbocharger,
Get the intake air density,
The maximum filling efficiency is determined according to predetermined characteristics using engine speed and intake air density as parameters,
Here, the above characteristics are set such that the engine speed at which the increase rate of maximum charging efficiency increases with respect to the increase in engine speed is higher on the side as the intake air density is lower.
A method for estimating the maximum charging efficiency of internal combustion engines. obtaining intake air density based on at least one of air pressure and intake air temperature;
The maximum charging efficiency estimation method for an internal combustion engine according to claim 1. Obtains information on the system status that affects the intake air amount and corrects the maximum filling efficiency according to this system status,
The maximum charging efficiency estimation method for an internal combustion engine according to claim 1. In an internal combustion engine maximum charging efficiency estimating device for estimating the maximum charging efficiency that can be obtained at an engine speed based on the engine speed in an internal combustion engine equipped with a turbocharger,
an intake air density acquisition unit that obtains intake air density;
a maximum filling efficiency calculation unit that calculates maximum filling efficiency according to predetermined characteristics using engine rotation speed and intake air density as parameters;
Equipped with
The above characteristics are set such that the engine speed at which the rate of increase in maximum charging efficiency increases with respect to the increase in engine speed is higher as the intake air density is lower.
Maximum charging efficiency estimation device for internal combustion engines.

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