JP7352756B2 - Internal combustion engine control device and internal combustion engine control method - Google Patents

Description

The present invention relates to an internal combustion engine control device and an internal combustion engine control method.

Due to recent tightening of exhaust regulations and fuel economy regulations, lower exhaust emissions and higher efficiency of gasoline engines are required. Under such circumstances, combustion control techniques are known that estimate the state inside the combustion chamber of an engine (also referred to as an internal combustion engine) and control the engine based on the estimation result. By appropriately controlling ignition timing, injection timing, etc. according to the estimated combustion state, it is possible to improve the thermal efficiency of the engine or reduce harmful gas emissions. An example of such a combustion state estimation technique is disclosed in Patent Document 1, for example.

Patent Document 1 describes "a means for calculating rotational acceleration of an engine, and a means for estimating a combustion state in a combustion chamber based on the rotational acceleration." Specifically, it is described that the combustion phase is estimated from the rotational position where the rotational acceleration detected by the rotational angle sensor is the extreme value, by using the correlation between the rotational position where the rotational acceleration is the extreme value and the combustion phase. ing.

An example of an actual engine phenomenon related to the technology disclosed in Patent Document 1 will be described.
FIG. 1 is a diagram showing the relationship between the cylinder pressure and the engine rotation speed with respect to the crank angle. In the example shown in FIG. 1, the rotation speed will be used as a parameter instead of the rotational acceleration disclosed in Patent Document 1.

In the upper part of FIG. 1, an example of a curve showing the relationship between the crank angle and the cylinder pressure is shown. On this curve, the ignition timing and the timing of MFB50 are shown. After the air-fuel mixture is ignited according to the ignition timing, combustion begins and the cylinder pressure rises, resulting in a combustion phase in which the mass fraction of the air-fuel mixture becomes 50% (hereinafter referred to as "MFB (Mass Fraction Burned) 50"). combustion ends. This combustion phase affects the rotational position (hereinafter referred to as "θω_MAX") at which the rotational speed reaches an extreme value (maximum value) through the crankshaft. In the following explanation, the combustion phase at which the mass combustion ratio is 50% is also referred to as the "combustion center of gravity." The curve shown in the upper part of FIG. 1 is used as an example of a second approximate curve that approximates the ignition timing from the combustion gravity.

At the bottom of FIG. 1, an example of a curve showing the relationship between the crank angle and the rotational speed is shown. On this curve, the timing of θω_MAX at which the rotational speed reaches its maximum value is shown. The curve shown at the bottom of FIG. 1 is used as an example of a first approximation curve for approximating the rotation speed to the crank angle.

FIG. 2 is a graph showing the relationship between θω_MAX and MFB50.
With the physical phenomenon represented by the curve shown in FIG. 1 as a background, FIG. 2 shows an example of a high correlation between θω_MAX and MFB50. Therefore, by creating a calibration curve based on the relationship between θω_MAX and MFB50 shown in FIG. 2, the internal combustion engine control device can estimate MFB50 from θω_MAX.

In mobile objects such as automobiles, the combustion phase may change over a wide range depending on the driving conditions. The inventors' study revealed that when the combustion phase is greatly advanced, the correlation between the rotational position where the rotational speed or rotational acceleration reaches an extreme value and the combustion phase, compared to the case where the combustion phase is not greatly advanced. It became clear that the characteristics changed.
FIG. 3 is a diagram showing how the relationship between θω_MAX and MFB50 changes as the ignition timing advances.

In the region labeled "normal region" in the figure, as the ignition timing advances, MFB50 decreases according to the correlation shown in FIG. 2. The relationship between θω_MAX and MFB50 at this time is expressed as a calibration curve (1). On the other hand, the region labeled "advanced angle region" in the figure represents a situation where the ignition timing is more advanced than the normal region. The relationship between θω_MAX and MFB50 at this time is expressed as a calibration curve (2).

In order to estimate MFB50 from θω_MAX using a calibration curve in a situation where the combustion phase changes over a wide range, it is necessary to switch the calibration curve according to the combustion phase. A possible method is to use, for example, ignition timing as an index at the time of switching the configuration curve. Specifically, the threshold value of the ignition timing at the inflection point where the slope of the calibration curve changes is set as the switching ignition timing. Then, the calibration curve is switched when the ignition timing reaches the switching ignition timing. For example, when the ignition timing advances and reaches the switching ignition timing, control is performed to switch the calibration curve (1) to the calibration curve (2). However, as shown by the broken line in the vertical direction with respect to a point θω_MAX in the figure, the value of MFB50 may differ between the normal range and the advanced angle range even at θω_MAX. Therefore, it was necessary to correctly determine whether the ignition timing exists in the normal range or the advance range.

A technique related to such configuration curve switching control is disclosed in Patent Document 2. In Patent Document 2, in a region where the ignition timing is retarded, as the ignition timing advances, the MFB50 also advances, whereas if the ignition timing is advanced as it is, a certain ignition timing is On the other hand, it is described that as the ignition timing advances, the MFB50 retards, exhibiting the opposite characteristics. Furthermore, as a countermeasure, a technique has been disclosed that switches the relational expression between ignition timing and MFB50 at a specific ignition timing.

JP 2017-150393 Publication Japanese Patent Application Publication No. 2010-229928

However, as a result of further investigation by the present inventors, we found that the ignition timing at the point where the characteristics of the calibration curve shown in Figure 3 change is not constant, and depends on external environmental conditions such as temperature and humidity outside the moving object. It was found that the ignition timing changes. Therefore, if the calibration curve cannot be appropriately switched when the external environment changes and an incorrect MFB50 is calculated, there is a risk that optimal ignition timing control cannot be performed.

Furthermore, the technique disclosed in Patent Document 2 does not take into account any specific changes in ignition timing due to changes in the external environment. For this reason, even if the technique disclosed in Patent Document 2 is used, the problem that an incorrect MFB50 is still calculated and optimal ignition timing control cannot be performed cannot be solved.

The present invention has been made in view of this situation, and it is an object of the present invention to implement optimal ignition timing control regardless of changes in the external environment.

The internal combustion engine control device according to the present invention includes a rotation speed converter that converts a measured crank angle into the rotation speed of the internal combustion engine, a maximum rotation speed detection section that detects the maximum value of the rotation speed, and an ignition timing advance angle. Accordingly, the ignition timing at which the maximum rotational speed reaches a specified threshold is set as the switching ignition timing, and the switching ignition timing changes according to the external environment of the mobile body in which the internal combustion engine is mounted, When the ignition timing is retarded than the switching ignition timing, the combustion center of gravity is estimated from the maximum rotation speed using the first calibration curve, and when the ignition timing is advanced from the switching ignition timing, the second calibration curve is estimated. A combustion center estimator that estimates the combustion center of gravity from the maximum rotation speed using and an ignition timing correction section that outputs the corrected ignition timing. Further, the first calibration curve is used when the external environment is in a standard state, the second calibration curve is used when the external environment is in a state other than the standard state, and the combustion center of gravity estimation section , a comparison section that compares the corrected ignition timing output to the ignition output circuit and outputs the comparison result, and calculates the combustion center of gravity by selecting the first calibration curve or the second calibration curve based on the comparison result. and a selection calculation unit.

According to the present invention, when the ignition timing is advanced or retarded from the switching ignition timing that changes depending on the external environment, the optimal combustion center of gravity is estimated using an appropriate calibration curve. ignition timing control can be carried out.
Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

FIG. 3 is a diagram showing the relationship between cylinder pressure and engine rotation speed with respect to a conventional crank angle. It is a graph showing the relationship between θω_MAX and MFB50 in the related art. FIG. 7 is a diagram showing how the relationship between θω_MAX and MFB50 changes as the conventional ignition timing advances. 1 is a diagram showing an example of the overall configuration of an internal combustion engine according to a first embodiment of the present invention. 1 is a block diagram illustrating a hardware configuration of a control device according to a first embodiment of the present invention. FIG. FIG. 2 is a block diagram showing a configuration example of a combustion detection section according to the first embodiment of the present invention. FIG. 3 is a diagram for explaining a method for estimating MFB50 by a conventional control device. It is a figure which shows the example of the change of the conventional switching ignition timing in a standard state and a high temperature, high humidity state. It is a figure which shows the example of ignition timing (ADV), the mode of a calibration curve, and estimated conventional MFB50 in a standard state and a high temperature, high humidity state. FIG. 3 is a diagram for explaining a method for estimating MFB50 by the control device according to the first embodiment of the present invention. An example of the ignition timing for each state according to the first embodiment of the present invention and the MFB50 estimated by the control device according to the first embodiment is shown. 3 is a flowchart illustrating an example of a control procedure performed by the control device according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining a method for estimating MFB50 by a control device according to a second embodiment of the present invention. It is a flowchart which shows the example of the control procedure performed by the control apparatus based on the 2nd Embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions or configurations are designated by the same reference numerals and redundant explanations will be omitted.

[First embodiment]
<Example of configuration of internal combustion engine>
First, a configuration example of an internal combustion engine 100 according to a first embodiment of the present invention will be described.
FIG. 4 is a diagram showing an example of the overall configuration of internal combustion engine 100 according to the first embodiment.

The internal combustion engine 100 includes an air flow sensor 1 that measures the intake amount of air newly taken in from the outside, a compressor 2 that performs supercharging to intake more intake gas, and a compressor 2 that cools the supercharged intake gas. A throttle valve 4 is provided to adjust the amount of intake gas sucked into the cylinder 5.

A throttle sensor 17 is provided near the throttle valve 4 to detect the throttle opening of the throttle valve 4 . The intake port is provided with a fuel injection device 9 that injects fuel into the cylinder 5 of each cylinder, and an intake valve 7 that adjusts the amount of mixed gas flowing into the cylinder 5.

The cylinder 5 of each cylinder is provided with a spark plug 6 that ignites the mixed gas in the cylinder 5, and a piston 10 that compresses the mixed gas of fuel and air that has flowed into the cylinder 5. The exhaust port is provided with an exhaust valve 8 for discharging exhaust gas after combustion. The piston 10 is moved up and down by a crankshaft. A signal rotor 13 is attached to the crankshaft, and a crank angle sensor 11 detects a signal from the signal rotor 13. Further, the water temperature sensor 12 measures the temperature of the cooling water of the internal combustion engine 100 .

Further, the internal combustion engine 100 is provided with a turbine 14 that transmits kinetic energy of exhaust gas to the compressor 2 via a shaft, and a three-way catalyst 15 that purifies harmful substances in the exhaust gas. An A/F (Air-Fuel) sensor 16 is provided near the three-way catalyst 15 to detect the oxygen concentration contained in the exhaust gas.

Output signals from various sensors such as the aforementioned throttle sensor 17, air flow sensor 1, crank angle sensor 11, water temperature sensor 12, A/F sensor 16, and accelerator sensor 18 (see FIG. 5) are input to the control device 200. .

<Example of configuration of control device>
Next, an example of the hardware configuration of the control device 200 will be described.
FIG. 5 is a block diagram illustrating the hardware configuration of the control device 200. Control device 200 is used as an example of an internal combustion engine control device that controls the operation of internal combustion engine 100.

The control device 200 includes an input circuit 201, an input/output port 202, a RAM (Random Access Memory) 203, a ROM (Read Only Memory) 204, a CPU (Central Processing Unit) 205, a throttle valve drive circuit 206, and a fuel injection device drive circuit 207. , and an ignition output circuit 208.

The input circuit 201 of the control device 200 receives output signals from various sensors. FIG. 5 shows an example in which output signals are input to the input circuit 201 using various sensors such as the throttle sensor 17, air flow sensor 1, crank angle sensor 11, water temperature sensor 12, A/F sensor 16, and accelerator sensor 18. The input circuit 201 performs signal processing such as noise removal from output signals from various sensors. The input circuit 201 then transmits the processed signal to the input/output port 202.

The signal sent to the input/output port 202 is stored in the RAM 203. The signals stored in the RAM 203 are processed by the CPU 205. A control program that describes the contents of arithmetic processing is written in the ROM 204 in advance, and each function is implemented by the CPU 205 executing the control program written in the ROM 204, and each of the implemented functions executes a predetermined arithmetic processing. will be held.

Values representing the operation amount of each actuator calculated by the CPU 205 according to the control program are stored in the RAM 203 and then transmitted to the input/output port 202. For example, a drive signal for realizing the target opening degree of the throttle valve 4 is outputted to a motor (not shown) that drives the throttle valve 4 via the throttle valve drive circuit 206.

Further, as a drive signal for the fuel injection device 9, an ON/OFF signal is set which is ON when the valve is opened and OFF when the valve is closed. This drive signal is amplified to enough energy to drive the fuel injector 9 by the fuel injector drive circuit 207 and is supplied to the fuel injector 9.

Further, as an operating signal output to the spark plug 6, an ON/OFF signal is turned ON when current is flowing to the primary coil (not shown) provided in the ignition output circuit 208, and is OFF when current is not flowing. is set. Note that the ignition timing of the spark plug 6 is the point in time when the current changes from ON to OFF. A signal supplied to the ignition plug 6 set in the input/output port 202 is amplified by the ignition output circuit 208 to the energy necessary for ignition, and then supplied to the ignition plug 6.

Further, the control device 200 uses the output value of the A/F sensor 16 to perform feedback control to sequentially correct the fuel injection amount or the intake air amount so that the purification efficiency of the three-way catalyst 15 becomes optimal.

<Example of configuration of combustion detection section>
FIG. 6 is a block diagram showing a configuration example of the combustion detection section 300. The combustion detection unit 300 is one of the functional units installed in the CPU 205, and has a function of estimating MFB50. Therefore, the combustion detection section 300 is a function of the internal combustion engine control device.

The combustion detection section 300 includes a rotation speed conversion section 301, a θω_MAX detection section 302, an MFB50 estimation section 303, an ignition timing correction section 304, and a learning section 305.

The rotation speed conversion unit (rotation speed conversion unit 301) converts the measured crank angle into the rotation speed of the internal combustion engine (internal combustion engine 100). For example, the rotation speed conversion unit 301 converts the number of pulse signals of the crank angle sensor 11 inputted from the RAM 203 into a rotation speed signal indicating a rotation speed value (referred to as "rotation speed"). Then, the rotation speed conversion section 301 outputs the rotation speed to the θω_MAX detection section 302. Here, the rotation speed conversion section (rotation speed conversion section 301) converts the crank angle into the rotation speed using a first approximation curve (see FIG. 1) that approximates the rotation speed to the crank angle.

The maximum rotational speed detection unit (θω_MAX detection unit 302) detects the maximum value of the rotational speed (hereinafter referred to as “θω_MAX”) based on the input rotational speed signal. Then, the θω_MAX detection unit 302 outputs the detected θω_MAX to the MFB50 estimation unit 303.

The MFB50 estimation section 303 includes a comparison section 311 and a selection calculation section 312.
The calibration curves (1) and (2) are input to the MFB50 estimation unit 303 from the θω_MAX detection unit 302. Furthermore, the MFB50 estimation unit 303 reads out the switching ignition timing and the current ignition timing from the RAM 203.

The combustion center of gravity estimating unit (MFB50 estimating unit 303) sets the ignition timing at the time when the maximum value (θω_MAX) of the rotation speed reaches a prescribed threshold value (θω_ch) as the ignition timing advances as the switching ignition timing. . Then, when the switching ignition timing changes depending on the external environment of the mobile body in which the internal combustion engine (internal combustion engine 100) is mounted, and the current ignition timing is retarded than the switching ignition timing, the first calibration curve ( The combustion center of gravity (MFB50) is estimated from the maximum value (θω_MAX) of the rotation speed using the calibration curve (1)). On the other hand, when the current ignition timing is advanced from the switching ignition timing, the combustion center of gravity (MFB50) is estimated from the maximum value (θω_MAX) of the rotation speed using the second calibration curve (calibration curve (2)). Note that after starting the internal combustion engine (internal combustion engine 100), the switching ignition timing is undetermined, and the first calibration curve (calibration curve (1)) is used when the external environment is in the standard condition. The second calibration curve (calibration curve (2)) is used when the condition is other than the above. Further, the external world information representing the external environment includes at least one value of temperature and humidity of the external environment. The above-mentioned switching ignition timing changes based on external world information representing the external environment.

The comparison unit (comparison unit 311) compares the switching ignition timing with the corrected ignition timing output to the ignition output circuit (ignition output circuit 208), and outputs the comparison result. For example, the comparison unit 311 compares the switching ignition timing read from the RAM 203 and the current ignition timing, and checks whether the current ignition timing exceeds the switching ignition timing. The comparison unit 311 then outputs the comparison result to the selection calculation unit 312.

The selection calculation unit (selection calculation unit 312) selects the first calibration curve (calibration curve (1)) or the second calibration curve (calibration curve (2)) based on the comparison result to determine the combustion center of gravity (MFB50). calculate. Then, the selection calculation section 312 outputs the estimated MFB50 to the ignition timing correction section 304.

The ignition timing correction unit (ignition timing correction unit 304) corrects the ignition timing based on the estimated combustion center of gravity (MFB50), and outputs an activation signal to the spark plug that ignites the air-fuel mixture. 208), the corrected ignition timing is output. For example, the ignition timing correction unit 304 calculates an ignition timing correction value (referred to as "ignition correction value") based on the input estimated value of MFB50 so as to obtain an optimal MFB50. At this time, the ignition timing correction section (ignition timing correction section 304) corrects the ignition timing using a second approximate curve (see FIG. 1) that approximates the ignition timing from the combustion center of gravity (MFB50). The ignition correction value is output to the ignition output circuit 208. Further, the ignition timing correction unit 304 writes the corrected ignition timing into the RAM 203. The corrected ignition timing written in the RAM 203 is inputted again to the MFB50 estimation unit 303 as the current ignition timing.

The learning unit (learning unit 305) sets the ignition timing output to the ignition output circuit (ignition output circuit 208) as the switching ignition timing when the maximum value (θω_MAX) of the rotation speed reaches the threshold value (θω_ch). learn. For example, the learning unit 305 learns the switching ignition timing based on the corrected ignition timing written in the RAM 203. The learning unit 305 then writes the switching ignition timing into the RAM 203. In addition, after learning the switching ignition timing, the learning unit (learning unit 305) outputs the signal to the ignition output circuit (ignition output circuit 208) when the maximum value (θω_MAX) of the rotation speed reaches the threshold value (θω_ch). The ignition timing for switching is learned again as the ignition timing for switching, and the previously learned ignition timing for switching is updated with the ignition timing for switching learned again. For example, if there is already a switching ignition timing written in the RAM 203, the learning unit 305 updates the previously written switching ignition timing to the currently learned switching ignition timing. This updated switching ignition timing is read out by the comparator 311.

<Example of conventional calibration curve switching control>
Next, before explaining the basic content of the present invention in detail, the control operation in the conventional control device will be explained again.
FIG. 7 is a diagram for explaining a method for estimating MFB50 by a conventional control device. The asterisk shown in the figure represents the current operating point of the internal combustion engine 100.

As shown in explanatory diagram (1) of FIG. 7, the conventional control device estimates MFB50 from θω_MAX using the linear calibration curve shown in FIG. As described above, in FIG. 2, the ignition timing is plotted on the calibration curve, and as the ignition timing advances, the ignition timing moves toward the lower left of the calibration curve.

Furthermore, when the ignition timing is advanced, an inflection point appears where the slope of the calibration curve changes as shown in FIG. 3, and a calibration curve with a different slope appears. Here, if the area where the ignition timing is retarded than the ignition timing at the inflection point is defined as the normal area, and the area where the ignition timing is more advanced than that is defined as the advanced angle area, then the calibration curve for the normal area is the calibration curve (1), Let the calibration curve in the advance angle region be the calibration curve (2).

Therefore, a binary problem occurs in which one θω_MAX has two MFB50 values.
Therefore, conventionally, as shown in explanatory diagram (2) of FIG. 7, an ignition timing (fixed value) for switching the calibration curve has been provided. Then, when the ignition timing is advanced and the current ignition timing becomes equal to the switching ignition timing (fixed value), the control device compares the switching ignition timing (fixed value) with the current ignition timing.

If the current ignition timing is retarded than the switching ignition timing (fixed value), the control device maintains the use of the calibration curve (1) and performs the calibration, as shown in explanatory diagram (3) in Fig. 7. MFB50 is estimated using curve (1).
On the other hand, if the current ignition timing is advanced from the switching ignition timing (fixed value), the control device switches to the calibration curve (2) and sets the MFB50 as shown in the explanatory diagram (4) in FIG. presume.

Next, problems with the conventional method of switching between calibration curves (1) and (2) will be explained.
FIG. 8 is a diagram showing an example of a change in the conventional switching ignition timing between a standard state and a high temperature and high humidity state. Here, the standard state is assumed to be, for example, an external temperature of 25° C. and a humidity of 40%.

In the standard state shown in explanatory diagram (1) of FIG. 8, the switching ignition timing is 40°. The switching ignition timing was fixed. Then, when the ignition timing was advanced and exceeded the switching ignition timing of 40°, the calibration curve was switched to the appropriate calibration curve (2). In this way, in the standard state, an appropriate calibration curve (1) or (2) could be selected before and after the switching ignition timing. However, it has been found that the value of the switching ignition timing changes due to changes in environmental conditions.

In the high temperature and high humidity state shown in explanatory diagram (2) of FIG. 8, the switching ignition timing changes to 45°. Therefore, when the ignition timing is advanced and exceeds 45°, which is the switching ignition timing, it is necessary to switch to the calibration curve (2). However, as shown in the standard state, if the switching ignition timing remains fixed at 40 degrees, the conventional control device may select an inappropriate calibration curve and estimate an incorrect MFB50.

FIG. 9 is a diagram showing an example of the ignition timing (ADV), the mode of the calibration curve, and the estimated conventional MFB50 in a standard state and a high temperature and high humidity state. The horizontal axis in FIG. 9 represents time.

The ignition timing (ADV) shown in the upper part of FIG. 9 repeatedly advances and retards in the standard state and in the high temperature and high humidity state.
In the middle part of FIG. 9, an example of the mode of the calibration curve is shown. The calibration curve mode indicates that the conventional control device has set either calibration curve (1) or (2). The broken line in the figure represents the mode of the calibration curve that is appropriately set, and the solid line represents the mode of the calibration curve that is actually set.

In the standard state, the calibration curve (1) is switched to the calibration curve (2) at the timing when the ignition timing is advanced to the switching ignition timing (fixed value). Further, the calibration curve (2) is switched to the calibration curve (1) at the timing when the ignition timing is retarded to the switching ignition timing (fixed value).

However, in a high temperature and high humidity state, the mode of the calibration curve is set with the fixed ignition timing for switching even though the ignition timing for switching is advanced. Therefore, when the ignition timing is advanced, the mode of the actual calibration curve is switched later than the mode of the appropriate calibration curve. Conversely, when the ignition timing is retarded, the mode of the actual calibration curve is progressively switched to the mode of the appropriate calibration curve.

The lower part of FIG. 9 shows changes in MFB50 estimated by a conventional control device using a calibration curve. The broken line in the figure represents the measured value of MFB50, and the solid line represents the estimated value of MFB50.

In the standard state, the MFB50 is estimated by an appropriately set mode of the calibration curve, so the actual value of the MFB50 matches the estimated value.
However, in a high temperature and high humidity state, the timing at which the mode of the actual calibration curve changes is different from the mode of the appropriate calibration curve, so the actual value of MFB50 does not match the estimated value.

<Example of calibration curve switching control according to the first embodiment of the present invention>
Therefore, in the control device 200 according to the first embodiment of the present invention, the ignition timing for switching is not set to a fixed value, but the ignition timing for switching is learned when the value of θω_MAX reaches a certain threshold value (θω_ch). Note that the threshold value (θω_ch) is a preset fixed value.
FIG. 10 is a diagram for explaining a method for estimating MFB50 by control device 200 according to the first embodiment. The asterisk shown in the figure represents the current operating point of the internal combustion engine 100.

As shown in explanatory diagram (1) of FIG. 10, the control device 200 according to the first embodiment also estimates MFB50 from θω_MAX using a linear calibration curve. As described above, in FIG. 10, the ignition timing is plotted on the calibration curve (1). However, when starting the internal combustion engine 100, the initial value of the switching ignition timing is undetermined. Then, the control device 200 estimates MFB50 using the calibration curve (1).

As shown in explanatory diagram (2) of FIG. 10, the ignition timing is advanced and the current operating point moves toward the lower left of the calibration curve, and when the inflection point is reached, θω_MAX takes θω_ch. For example, the learning unit 305 (see FIG. 6) learns the ignition timing when θω_MAX becomes θω_ch as the switching ignition timing, and stores it in the RAM 203. The comparison unit 311 of the MFB50 estimation unit 303 reads the switching ignition timing and the current ignition timing from the RAM 203.

The comparison unit 311 compares the switching ignition timing with the current ignition timing and outputs the comparison result. As shown in explanatory diagram (3)-A of FIG. 10, when the comparison result that the ignition timing is retarded is inputted by the comparison unit 311, the selection calculation unit 312 selects the calibration curve (1) and adjusts the MFB50. In order to estimate , the calibration curve is not switched.

On the other hand, as shown in explanatory diagram (3)-B in FIG. 2) and estimate MFB50 using the calibration curve (2).

By changing the switching ignition timing instead of setting it as a fixed value in this way, it is possible to select the optimum ignition timing regardless of environmental conditions.
FIG. 11 is a diagram showing an example of the ignition timing for each state according to the first embodiment and the MFB 50 estimated by the control device 200 according to the first embodiment. The broken lines in the middle and lower rows of FIG. 11 represent the true value of MFB50, and the solid lines represent the estimated value of MFB50.

The upper part of FIG. 11 shows how the ignition timing changes. Here, the state of the ignition timing is shown when the ignition timing changes over time in the order of standard state, high temperature and high humidity state, and standard state. The ignition timing in the normal range and advance range changes in accordance with the timing at which the standard state and the high temperature and high humidity state change.

The middle part of FIG. 11 shows how the MFB50 changes estimated by the MFB50 estimation unit 303 before the control according to the first embodiment is applied.
In high temperature and high humidity conditions, the ignition timing enters the advanced range, so it is appropriate to select the calibration curve (2). However, since the calibration curve (1) was selected before the control according to the first embodiment was applied, it is shown that an error occurs between the true value and the actual value.

The lower part of FIG. 11 shows how the MFB50 changes estimated by the MFB50 estimation unit 303 after the control according to the first embodiment is applied.
In high temperature and high humidity conditions, the ignition timing falls into the advanced range, so the selection calculation unit 312 selects the calibration curve (2). Then, the selection calculation unit 312 estimates MFB50 using the calibration curve (2). Note that in the standard state, the selection calculation unit 312 selects the calibration curve (1) and estimates the MFB50 using the calibration curve (1). This figure shows that the estimated value of MFB50 matches the true value of MFB50 with high accuracy.

FIG. 12 is a flowchart illustrating an example of a control procedure performed by the control device 200 according to the first embodiment. The execution contents of each step will be explained with reference to FIG.

When the driver starts driving, the ignition timing is advanced (S1). At this time, the selection calculation unit 312 of the MFB50 estimating unit 303 estimates MFB50 using the calibration curve (1), with the switching ignition timing of the calibration curve being undetermined.

When θω_MAX reaches θω_ch, which is the switching point of the calibration curve, the learning unit 305 learns the current ignition timing as the switching ignition timing (ADV_ch) (S2). The learning unit 305 then stores the switching ignition timing (ADV_ch) in the RAM 203 (S3).

Next, the comparison unit 311 compares the current ignition timing and the switching ignition timing (ADV_ch), determines whether the current ignition timing is advanced from the switching ignition timing, and selects the determination result. It is output to the calculation unit 312 (S4).

If the determination result is that the current ignition timing is further advanced than the switching ignition timing, the selection calculation unit 312 switches from the calibration curve (1) to the calibration curve (2) (S5).
On the other hand, when the selection calculation unit 312 determines that the current ignition timing is retarded than the switching ignition timing, the selection calculation unit 312 maintains the use of the calibration curve (1) (S6).

Next, the selection calculation unit 312 estimates MFB50 using the selected calibration curve (1) or (2) (S7), and outputs the estimated MFB50 to the ignition timing correction unit 304.

The ignition timing correction unit 304 corrects the ignition timing based on the input estimated MFB50 (S8). Ignition timing correction section 304 outputs the corrected ignition timing to ignition output circuit 208. The ignition timing corrector 304 writes the corrected ignition timing into the RAM 203.

The control device 200 according to the first embodiment described above sequentially learns the ignition timing at the switching point in the calibration curve of MFB50 and θω_MAX, and switches the calibration curve using the learned switching ignition timing as an index. is estimated.

Therefore, as a step according to the present embodiment, the switching ignition timing is left undetermined at the start of startup of the internal combustion engine 100. Thereafter, when the ignition timing is advanced and θω_MAX becomes θω_ch, the ignition timing at that time is learned as the switching ignition timing. If the current ignition timing is further advanced than the switching ignition timing, the selection calculation unit 312 switches to the calibration curve (2) and estimates MFB50. On the other hand, if the current ignition timing is delayed from the switching ignition timing, the selection calculation unit 312 estimates MFB50 using the calibration curve (1).

The value of MFB50 estimated in this way accurately matches the true value as shown in FIG. 11. Since the control device 200 controls the optimal ignition timing based on the estimated combustion center of gravity, it is possible to improve fuel efficiency compared to the conventional method. Therefore, deterioration in fuel efficiency due to environmental changes can be prevented in compliance with recently introduced exhaust gas regulations (Real Driving Emission (RDE) regulations) that are applied when driving on real roads.

[Second embodiment]
Next, an example of the operation of the control device 200 according to the second embodiment of the present invention will be described with reference to FIGS. 13 and 14.
For example, in a mobile body equipped with the internal combustion engine 100, if the external environment changes in a place where the mobile body has moved after the switching ignition timing has already been learned, the previously learned switching ignition timing may not be correctly calibrated. I can't switch between curves. The timing of the control performed by the control device 200 according to the second embodiment is assumed to be a time when the temperature and humidity of the outside world suddenly change, for example, when a moving object moves from a cold place to a warm place. .

Therefore, after updating the ignition timing at the switching point, the control device 200 according to the second embodiment advances or retards the ignition timing again and updates the switching ignition timing when it reaches θω_ch. Using the updated ignition timing, change the calibration curve and estimate MFB50.

FIG. 13 is a diagram for explaining a method for estimating MFB50 by control device 200 according to the second embodiment. In addition, in FIG. 13, descriptions of explanatory diagrams (1) and (2) shown in FIG. 10 are omitted, and an example is shown after the ignition timing represented as the current operating point reaches the calibration curve (2). It will be done.

Explanatory diagram (3)-B in FIG. 13 is the same as explanatory diagram (3)-B in FIG. It is assumed that the first learning of the ignition timing for switching has been completed and that the calibration curve (2) is being used. Assume that after the ignition timing at the switching point has been updated, the ignition timing is advanced or retarded again.

Explanatory diagram (4) in FIG. 13 shows how the ignition timing is retarded.
In explanatory diagram (5) of FIG. 13, when the retarded ignition timing reaches θω_ch learned as an inflection point, the learning unit 305 updates the switching ignition timing again. That is, after learning the switching ignition timing, the learning unit (learning unit 305) retards the ignition timing that had been advanced from the switching ignition timing, and the maximum value (θω_MAX) of the rotation speed becomes the threshold value (θω_ch). The ignition timing that is output to the ignition output circuit (ignition output circuit 208) at the time when the ignition timing is reached is learned again as the switching ignition timing. The comparison unit 311 then compares the current ignition timing and the switching ignition timing.

As shown in explanatory diagram (6)-A in FIG. 13, when the comparison result indicating that the ignition timing is retarded is inputted by the comparison unit 311, the selection calculation unit 312 converts the calibration curve (2) to the calibration curve (1). , and estimate MFB50.

On the other hand, as shown in explanatory diagram (6)-B in FIG. 13, when the comparison result indicating that the ignition timing has been advanced is inputted by the comparison unit 311, the selection calculation unit 312 maintains the calibration curve (2). In order to estimate MFB50, the calibration curve is not changed.

FIG. 14 is a flowchart illustrating an example of a control procedure performed by control device 200 according to the second embodiment. The execution details of each step will be explained with reference to FIG. 14.

FIG. 14 is a flowchart illustrating an example of a control procedure performed by the control device 200 according to the first embodiment. The execution details of each step will be explained with reference to FIG. 14.

First, it is assumed that the selection calculation unit 312 of the MFB50 estimation unit 303 is in a state where the ignition timing is advanced from the switching ignition timing. Therefore, the selection calculation unit 312 estimates MFB50 using the calibration curve (2) (S11).

Next, the selection calculation unit 312 retards the ignition timing, leaves the switching ignition timing of the calibration curve undetermined, and estimates MFB50 using the calibration curve (1) (S12).

Next, the selection calculation unit 312 sets θω_MAX to θω_ch, which is the switching point of the calibration curve, with the switching ignition timing of the calibration curve being undetermined (S13).

Next, when θω_MAX reaches θω_ch, which is the switching point of the calibration curve, the learning unit 305 learns the current ignition timing as the switching ignition timing (ADV_ch) (S14).

Next, the comparison unit 311 compares the current ignition timing and the switching ignition timing, and determines whether the current ignition timing is advanced or retarded from the switching ignition timing (ADV_ch), The determination result is output to the selection calculation section 312 (S15).

When the selection calculation unit 312 determines that the current ignition timing is advanced than the switching ignition timing, the selection calculation unit 312 maintains the use of the calibration curve (2) (S16).
On the other hand, if the selection calculation unit 312 determines that the current ignition timing is retarded than the switching ignition timing, the selection calculation unit 312 switches from the calibration curve (2) to the calibration curve (1) (S17).

Next, the selection calculation unit 312 estimates MFB50 using the selected calibration curve (1) or (2) (S18), and outputs the estimated MFB50 to the ignition timing correction unit 304.

The ignition timing correction unit 304 corrects the ignition timing based on the input estimated MFB50 (S19). Ignition timing correction section 304 outputs the corrected ignition timing to ignition output circuit 208. The ignition timing corrector 304 writes the corrected ignition timing into the RAM 203.

Also in the control device 200 according to the second embodiment described above, the ignition timing of the switching point in the calibration curve of MFB50 and θω_MAX is sequentially learned, and the calibration curve is switched using the learned switching ignition timing as an index. An estimation of MFB50 is performed. Even if the ignition timing for switching was previously advanced, if θω_MAX reaches θω_ch again due to the retardation of the ignition timing, the ignition timing for switching is learned again, and the ignition timing for switching is learned again. Based on the ignition timing, the previously learned switching ignition timing is updated.

Therefore, as a step according to the present embodiment, after the internal combustion engine 100 is started and the switching ignition timing is learned, it is detected that θω_MAX has become θω_ch. The switching ignition timing at the time when ω_MAX becomes θω_ch is learned again. If the current ignition timing is further advanced than the switching ignition timing, the selection calculation unit 312 maintains the calibration curve (2) and estimates MFB50. On the other hand, when the ignition timing is retarded than the switching ignition timing, the selection calculation unit 312 switches to the calibration curve (1) and estimates MFB50.

The value of MFB50 estimated in this way also accurately matches the true value as shown in FIG. 11. Since the control device 200 controls the optimal ignition timing based on the estimated combustion center of gravity, it is possible to improve fuel efficiency compared to the conventional method. Therefore, it is possible to prevent deterioration of fuel efficiency due to environmental changes in response to RDE regulations for driving on actual roads that have been introduced in recent years.

The learning timing of the switching ignition timing according to the second embodiment is not only when the above-mentioned ignition timing reaches θω_ch, but also when, for example, the outside temperature detected by the temperature sensor reaches a predetermined value. You can also do it when you do.

[Modified example]
In the first and second embodiments described above, an example has been described in which the switching ignition timing is learned when the outside world changes from a standard state to a high temperature and high humidity state. On the other hand, when the outside world changes to a low temperature and low humidity state, the switching ignition timing is retarded. Therefore, even in a low-temperature, low-humidity state, the learning unit 305 may learn the switching ignition timing, and the selection calculation unit 312 may estimate the MFB 50 using the learned switching ignition timing.

Further, the learning unit (learning unit 305) starts learning the ignition timing after starting the internal combustion engine (internal combustion engine 100), and when the value of external world information representing the external environment reaches a specific value, the learning unit (learning unit 305) starts learning the ignition timing again. You can also learn. For example, when the temperature is 30° C. and the humidity is 45%, it is considered to be a high temperature and high humidity state. Then, when the temperature changes from 25°C to 30°C and the humidity changes from 40% to 45%, the learning unit 305 can learn the ignition timing by defining the values after these changes as specific values. .

Further, the numerical value estimated by the selection calculation unit 312 may be other than MFB50. For example, the selection calculation unit 312 may estimate numerical values such as MFB40 and MFB60.

Note that the present invention is not limited to the embodiments described above, and it goes without saying that various other applications and modifications can be made without departing from the gist of the present invention as set forth in the claims.
For example, in each of the embodiments described above, configurations of devices and systems are explained in detail and specifically in order to explain the present invention in an easy-to-understand manner, and the embodiments are not necessarily limited to having all the configurations described. Furthermore, it is possible to replace a part of the configuration of the embodiment described here with the configuration of other embodiments, and it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment. It is possible. Furthermore, it is also possible to add, delete, or replace some of the configurations of each embodiment with other configurations.
Further, the control lines and information lines are shown to be necessary for explanation purposes, and not all control lines and information lines are necessarily shown in the product. In reality, almost all components may be considered to be interconnected.

6... Spark plug, 9... Fuel injection device, 10... Piston, 100... Internal combustion engine, 200... Control device, 208... Ignition output circuit, 300... Combustion detection section, 301... Rotation speed conversion section, 302... θω_MAX detection section, 303...MFB50 estimation section, 304...Ignition timing correction section, 305...Learning section, 311...Comparison section, 312...Selection calculation section

Claims (8)

a rotation speed conversion unit that converts the measured crank angle to the rotation speed of the internal combustion engine;
a maximum rotational speed detection unit that detects the maximum value of the rotational speed;
As the ignition timing advances, the ignition timing at the time when the maximum rotation speed reaches a prescribed threshold value is set as the switching ignition timing, and the switching ignition timing is set as the switching ignition timing of the mobile body in which the internal combustion engine is mounted. When the ignition timing changes in accordance with the external environment and is retarded than the switching ignition timing, the combustion center of gravity is estimated from the maximum value of the rotation speed using a first calibration curve, and the ignition timing is retarded from the switching ignition timing. a combustion center of gravity estimating unit that estimates the combustion center of gravity from the maximum value of the rotation speed using a second calibration curve when the ignition timing is advanced from the original ignition timing;
an ignition timing correction unit that corrects the ignition timing based on the estimated combustion center of gravity and outputs the corrected ignition timing to an ignition output circuit that outputs an activation signal to a spark plug that ignites the air-fuel mixture; Equipped with
The first calibration curve is used when the external environment is in a standard state, and the second calibration curve is used when the external environment is in a state other than the standard state,
The combustion center of gravity estimating unit is
a comparison unit that compares the switching ignition timing and the corrected ignition timing output to the ignition output circuit and outputs a comparison result;
a selection calculation unit that selects the first calibration curve or the second calibration curve and calculates the combustion center of gravity based on the comparison result;
Internal combustion engine control device. After the internal combustion engine starts, the switching ignition timing is undetermined, and when the maximum value of the rotation speed reaches the threshold value, the ignition timing output to the ignition output circuit is set as the switching ignition timing. The internal combustion engine control device according to claim 1, further comprising a learning section that performs learning. After learning the switching ignition timing, the learning section learns again the ignition timing that is output to the ignition output circuit when the maximum value of the rotation speed reaches the threshold value as the switching ignition timing. The internal combustion engine control device according to claim 2 , wherein the previously learned switching ignition timing is updated with the switching ignition timing learned again. After learning the switching ignition timing, the learning section retards the ignition timing that was advanced from the switching ignition timing, and when the maximum value of the rotation speed reaches the threshold value, the learning section starts the ignition timing. The internal combustion engine control device according to claim 3 , wherein the ignition timing output to the output circuit is learned again as the switching ignition timing. The learning unit starts learning the ignition timing after starting the internal combustion engine, and learns the ignition timing again when a value of external world information representing the external environment reaches a specific value. The internal combustion engine control device described. The rotation speed conversion unit converts the crank angle into the rotation speed using a first approximate curve that approximates the rotation speed with respect to the crank angle,
The internal combustion engine control device according to claim 5 , wherein the ignition timing correction section corrects the ignition timing using a second approximate curve that approximates the ignition timing from the combustion center of gravity. The internal combustion engine control device according to claim 6 , wherein the external world information includes at least one value of temperature and humidity of the external environment. A process of converting the measured crank angle into the rotational speed of the internal combustion engine,
a process of detecting the maximum value of the rotational speed;
As the ignition timing advances, the ignition timing at the time when the maximum rotation speed reaches a prescribed threshold value is set as the switching ignition timing, and the switching ignition timing is set as the switching ignition timing of the mobile body in which the internal combustion engine is mounted. When the ignition timing changes in accordance with the external environment and is retarded than the switching ignition timing, the combustion center of gravity is estimated from the maximum value of the rotation speed using a first calibration curve, and the ignition timing is retarded from the switching ignition timing. a process of estimating the combustion center of gravity from the maximum value of the rotational speed using a second calibration curve when the ignition timing is advanced from the original ignition timing;
correcting the ignition timing based on the estimated combustion center of gravity and outputting the corrected ignition timing to an ignition output circuit that outputs an activation signal to a spark plug that ignites the air-fuel mixture;
The first calibration curve is used when the external environment is in a standard state, and the second calibration curve is used when the external environment is in a state other than the standard state,
In the process of estimating the combustion center of gravity,
a comparison process of comparing the switching ignition timing with the corrected ignition timing output to the ignition output circuit and outputting a comparison result;
A selection calculation process of selecting the first calibration curve or the second calibration curve and calculating the combustion center of gravity based on the comparison result is performed.
Internal combustion engine control method.

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