JP6740915B2 - Internal combustion engine self-ignition timing estimation device - Google Patents

Description

The present invention relates to a self-ignition timing estimation device for an internal combustion engine.

An internal combustion engine in which a main fuel for forming a premixed mixture is injected into the cylinder, then an assist fuel is injected into the cylinder and the assist fuel is ignited by a spark plug, and then the premixed mixture is combusted by compression ignition is known. (For example, see Patent Document 1). In Patent Document 1, the compression ignition of the premixed gas is started by the heat generated by the combustion of the assist fuel. In this case, although not explicitly disclosed in Patent Document 1, it is considered that the compression ignition combustion of the premixed gas is started during the combustion of the assist fuel.

By the way, it is necessary to control combustion for fuel consumption, exhaust emission, engine vibration or noise. For better control of combustion, it is necessary to know exactly when the compression ignition combustion is started, that is, the ignition timing.

In this regard, a technique for estimating the self-ignition timing in an internal combustion engine in which premixed mixture compression self-ignition combustion is performed is known (see, for example, Patent Document 2). In Patent Document 2, the state amount of the in-cylinder gas at the time when the in-cylinder gas starts to be compressed, the change amount of the state amount of the in-cylinder gas due to compression is estimated, and prior to autoignition of the premixed gas. The calorific value of the generated cold flame is estimated, and the self-ignition timing is estimated based on the state amount of the in-cylinder gas, the change amount of the state amount of the in-cylinder gas, and the calorific value of the cold flame. Further, in Patent Document 2, the state quantity of the in-cylinder gas is, for example, temperature, pressure, internal energy, etc. detected by a sensor. The change amount of the state quantity of the in-cylinder gas is estimated, for example, under the assumption that the state of the in-cylinder gas in the compression stroke changes adiabatically. The heat generation amount of the cold flame is estimated based on the fuel injection amount, the property of the fuel, the oxygen concentration in intake air, and the density of the in-cylinder gas.

JP-A-2005-034475 JP, 2005-273513, A

However, in Patent Document 2, after all, the self-ignition timing is estimated based only on the state quantity before the start of the compression self-ignition combustion. That is, the state quantity when the compression ignition combustion is performed is not considered at all. Therefore, the self-ignition timing may not be accurately estimated. Moreover, when the compression ignition combustion starts during combustion of the assist fuel as in Patent Document 1, for example, the in-cylinder pressure detected at this time is different from the combustion of the assist fuel and the compression ignition combustion of the premixed gas. Both are affected. Therefore, it is difficult to accurately estimate the self-ignition timing by simply detecting the state quantity when the compression self-ignition combustion is performed.

According to one aspect of the present invention, a fuel injection valve configured to supply fuel into the cylinder, a spark plug configured to ignite the fuel, and a premixture formed in the cylinder. The main fuel for injection is injected by the fuel injection valve, the assist fuel is then injected into the cylinder, the assist fuel is ignited by the spark plug, and the premixed mixture is then combusted by compression ignition. Ignition assisted self-ignition combustion control unit, in-cylinder pressure sensor configured to detect in-cylinder pressure, and heat release rate calculation configured to calculate a heat release rate with respect to a crank angle based on the in-cylinder pressure And a self-ignition timing estimation unit configured to estimate the self-ignition timing based on the heat release rate, the self-ignition timing estimation unit is configured to provide a crank angle at which the heat release rate is maximum. In the crank angle range set on the retard side of the maximum heat release rate crank angle, an approximate expression that approximates the heat release rate with a straight line is determined, and the crank angle at which the heat release rate is zero in the approximate expression. The zero heat release rate crank angle is determined, the difference between the maximum heat release rate crank angle and the zero heat release rate crank angle is calculated, and the crank angle is advanced by the difference from the maximum heat release rate crank angle. Is provided as the self-ignition timing, the self-ignition timing estimation device for an internal combustion engine is provided.

According to another aspect of the present invention, a fuel injection valve configured to supply fuel into the cylinder, a spark plug configured to ignite the fuel, and a premixture formed in the cylinder. Main fuel for injecting the fuel by the fuel injection valve, then injecting the assist fuel into the cylinder and igniting the assist fuel by the spark plug, and then the premixed mixture is combusted by compression ignition combustion. An ignition assist self-ignition combustion control unit, an in-cylinder pressure sensor for detecting an in-cylinder pressure, and a heat release rate calculation unit configured to calculate a heat release rate for a crank angle based on the in-cylinder pressure, And a self-ignition timing estimation unit configured to estimate the self-ignition timing based on the heat generation rate, wherein the self-ignition timing estimation unit is a crank angle that maximizes the heat generation rate. Heat release rate The maximum heat release rate is determined by determining an approximate expression that approximates the heat release rate with a Wiebe function in a crank angle range set to include a crank angle, and the heat release rate is zero in the approximate expression. There is provided a self-ignition timing estimation device for an internal combustion engine configured to estimate a crank angle on the advance side of a crank angle as the self-ignition timing.

The ignition timing can be more accurately estimated during ignition-assisted self-ignition combustion.

1 is an overall view of an internal combustion engine. It is a partial cross-sectional view of an internal combustion engine. It is a block diagram which shows the function of an electronic control unit. It is a map which shows SI combustion area, CI combustion area, and SACI combustion area. It is a diagram showing an example of fuel injection action and ignition action during SACI combustion. It is a block diagram which shows an example of a SACI combustion control part. It is a diagram showing an actual in-cylinder pressure, a predicted in-cylinder pressure, and the like. FIG. 6 is a diagram showing a heat release rate ROHR with respect to a crank angle CA during SACI combustion. FIG. 5 is a diagram showing a heat release rate ROHR with respect to a crank angle CA for explaining an example according to the present invention. It is a flow chart for performing a self-ignition timing estimation routine of an example by the present invention. FIG. 8 is a diagram showing a heat release rate ROHR with respect to a crank angle CA for explaining another embodiment according to the present invention. It is a flowchart for performing the self-ignition timing estimation routine of another embodiment according to the present invention.

Referring to FIG. 1, an internal combustion engine 1 includes an engine body 2 having a plurality of, for example, four cylinders 2a. The cylinder 2a is connected to the surge tank 4 via the intake branch pipe 3, and the surge tank 4 is connected to the outlet of the compressor 6c of the exhaust supercharger 6 via the intake duct 5. The inlet of the compressor 6c is connected to the air cleaner 8 through the intake introduction pipe 7. An air flow meter 9 for detecting the intake air amount is arranged in the intake introduction pipe 7. In the intake duct 5, a cooler 10 for cooling the intake air and a throttle valve 11 are sequentially arranged.

Further, the cylinder 2 a is connected to the inlet of the turbine 6 t of the exhaust supercharger 6 via the exhaust manifold 12. The outlet of the turbine 6t is connected to the catalyst 14 via the exhaust pipe 13. The upstream and downstream of the turbine 6t are connected to each other by the waste gate valve 15. An air-fuel ratio sensor 16 for detecting the air-fuel ratio is arranged in the exhaust pipe 13. The surge tank 4 and the exhaust manifold 12 are connected to each other by an exhaust gas recirculation (hereinafter referred to as EGR) passage 17. An EGR control valve 18 for controlling the EGR gas amount and a cooler 19 for cooling the EGR gas are arranged in the EGR passage 17.

FIG. 2 shows the engine body 2 of an embodiment according to the present invention in detail. Referring to FIG. 2, 30 is a cylinder block, 31 is a cylinder head, 32 is a piston, 33 is a combustion chamber, 34 is an intake port, 35 is an intake valve, 36 is a valve operating mechanism of an intake valve 35, 37 is an exhaust port, 38 is an exhaust valve, 39 is a variable valve mechanism of the exhaust valve 38, 40 is a fuel injection valve arranged substantially in the center of the combustion chamber 33, 41 is a spark plug arranged adjacent to the fuel injection valve 40, and 42 is a combustion chamber. Each of the in-cylinder pressure sensors arranged in 33 is shown. In the embodiment according to the present invention, gasoline is used as the fuel. The in-cylinder pressure sensor 42 is provided in at least one cylinder 2a.

Referring again to FIG. 1, the electronic control unit 50 comprises a digital computer and includes a ROM (read only memory) 52, a RAM (random access memory) 53, a CPU (microprocessor) 54, which are connected to each other by a bidirectional bus 51. It has an input port 55 and an output port 56. The output voltages of the air flow meter 9, the air-fuel ratio sensor 16, and the in-cylinder pressure sensor 42 are input to the input port 55 via the corresponding A/D converters 57. Further, a load sensor 60 that generates an output voltage proportional to the amount of depression of the accelerator pedal 59 is connected to the accelerator pedal 59, and the output voltage of the load sensor 60 is input to the input port 55 via the corresponding AD converter 57. It Further, a crank angle sensor 61 that generates an output pulse each time the crankshaft rotates, for example, 30 degrees is connected to the input port 55. The CPU 54 calculates the engine speed based on the output pulse from the crank angle sensor 61. On the other hand, the output port 56, via the corresponding drive circuit 58, the variable valve mechanism 39 of the cylinder 2a, the fuel injection valve 40 and the spark plug 41, the actuator of the throttle valve 11, the waste gate valve 15, and the EGR control valve. 18 are connected respectively.

FIG. 3 shows a block diagram showing the functions of the electronic control unit 50 in the embodiment according to the present invention. Referring to FIG. 3, an electronic control unit 50 according to an embodiment of the present invention includes a combustion selection unit 50a, a spark ignition (SI) combustion control unit 50b, a compression ignition (CI) combustion control unit 50c, and an ignition assisted auto ignition. (SACI) Combustion control unit 50d is provided.

The combustion selection unit 50a is configured to select a combustion to be executed from a plurality of combustions. In the embodiment according to the present invention, as shown in FIG. 4, for example, a spark ignition (SI) combustion region RSI, a compression ignition (CI) combustion region RCI, in an engine operating region determined by the engine torque TQ and the engine speed NE, An ignition assisted self-ignition (SACI) combustion region RSACI is defined. In the example shown in FIG. 4, the CI combustion region RCI is defined in a region where the engine torque TQ is relatively low and the engine speed Ne is relatively low. The SACI fuel region RSACI is defined on the higher torque side of the CI combustion region RCI while being adjacent to the CI combustion region RCI. The SI combustion region RSI is defined in other regions. In addition, in FIG. 4, WOT represents the full load.

When the engine operating state determined by the engine torque TQ and the engine speed Ne falls within the SI combustion region RSI, the combustion selection unit 50a selects spark ignition (SI) combustion. The SI combustion control unit 50b is configured to control the fuel injection valve 40, the spark plug 41 and the like to execute and control the SI combustion when the SI combustion is selected. Specifically, fuel injection is performed in the intake stroke, so that a substantially homogeneous premixed gas is formed in the combustion chamber 33. This premixed gas is then ignited by the spark plug 41 and burned in flame propagation. In the embodiment according to the present invention, the air-fuel ratio during SI combustion is set to the stoichiometric air-fuel ratio.

When the engine operating state belongs to the CI combustion region RCI, the combustion selection unit 50a selects compression self-ignition (CI) combustion. When the CI combustion is selected, the CI combustion control unit 50c is configured to control the fuel injection valve 40 and the like to execute and control the CI combustion when the CI combustion is selected. Specifically, fuel injection is performed in the intake stroke or the compression stroke, so that a substantially homogeneous premixed gas is formed in the combustion chamber 33. This premixed air is then compressed as the piston 32 rises, which causes it to self-ignite and burn. In this case, it is considered that the temperatures of the premixed gas in many positions in the combustion chamber 33 reach the self-ignition temperature almost at the same time, and the combustion is started almost simultaneously in the many positions. Thus, in CI combustion, the ignition action by the spark plug 41 is not performed. In the embodiment of the present invention, the air-fuel ratio during CI combustion is set leaner than the stoichiometric air-fuel ratio.

When the engine operating state belongs to the SACI combustion region RSACI, the combustion selection unit 50a selects ignition assisted self-ignition (SACI) combustion. The SACI combustion control unit 50d is configured to control the fuel injection valve 40, the spark plug 41, and the like to execute and control the SACI combustion when the SACI combustion is selected. Specifically, the main fuel is injected in the intake stroke or the compression stroke, so that a substantially homogeneous premixed gas is formed in the combustion chamber 33. Next, for example, a relatively small amount of assist fuel is injected at the end of the compression stroke. Next, the assist fuel is ignited by the spark plug 41 and burns and propagates in flame. Next, the premixed mixture is subjected to compression ignition combustion. In this case, the compression ignition ignition combustion of the premixed gas is reliably and easily caused by the heat generated by the combustion of the assist fuel. FIG. 5 shows an example of the fuel injection action and the ignition action during SACI combustion. In the example shown in FIG. 5, the main fuel is injected in the middle of the compression stroke as indicated by FM, and the assist fuel is injected at the end of the compression stroke as indicated by FA. Next, as indicated by SP, the assist fuel is ignited by the spark plug 41. In the embodiment of the present invention, the air-fuel ratio during SACI combustion is set leaner than the stoichiometric air-fuel ratio.

In SACI combustion, compression ignition combustion can be controlled by controlling flame propagation combustion of assist fuel. That is, for example, by controlling at least one of the amount and injection timing of the assist fuel and the ignition timing, the self-ignition timing of the compression self-ignition combustion can be easily controlled. Further, for example, by controlling the ratio of the calorific value due to flame propagation combustion to the calorific value due to compression self-ignition combustion, noise due to compression self-ignition combustion can be reduced or controlled.

In another embodiment (not shown), another fuel injection valve configured to inject fuel into the intake port 34 is provided, and when fuel should be injected into the intake stroke in each combustion, the other fuel injection valve is provided. A fuel injection valve is used.

In the embodiment according to the present invention, the SACI combustion control unit 50d is configured to control the engine control parameter so that the actual self-ignition timing becomes the target self-ignition timing, for example. FIG. 6 is a block diagram showing an example of the SACI combustion control unit 50d. In the example shown in FIG. 6, the SACI combustion control unit 50d includes a target self-ignition timing calculation unit 60a, a parameter calculation unit 60b, a heat release rate calculation unit 60c, a self-ignition timing estimation unit 60d, a cylinder state estimation unit 60e, and self-ignition. The time prediction unit 60f and the correction amount calculation unit 60g are provided.

The target self-ignition timing calculation unit 60a is configured to calculate the target self-ignition timing titt based on, for example, the engine operating state, the target torque, and the target efficiency. In one example, the target self-ignition timing tigt is stored in advance in the ROM 52 in the form of a map as a function of the engine operating state, the target torque, and the target efficiency.

The parameter calculation unit 60b is configured to calculate an engine control parameter required to set the self-ignition timing to the target self-ignition timing tight. The engine control parameters include the injection timing and injection amount of assist fuel, and the ignition timing.

The heat release rate calculation unit 60c is configured to calculate the heat release rate ROHR with respect to the crank angle CA based on the in-cylinder pressure detected by the in-cylinder pressure sensor 42. The heat release rate ROHR in this case is, for example, (dQ/dCA)/QT (for example, 1/deg.CA) when the heat release amount is Q, the crank angle is CA, and the total heat release amount is QT. ).

The self-ignition timing estimation unit 60d is configured to estimate the actual self-ignition timing based on the heat release rate ROHR. That is, the actual ignition timing estimator 60d calculates the actual ignition timing tiga.

The in-cylinder state estimation unit 60e is configured to estimate the in-cylinder state based on, for example, the engine operating state, the target torque, the target efficiency, and the second deviation dt2. The in-cylinder state is represented, for example, by at least one of the in-cylinder pressure, the in-cylinder temperature, the EGR rate (=EGR gas amount/in-cylinder gas amount) from the closing timing of the intake valve 35 to the self-ignition timing. In one example, the in-cylinder state is calculated using a model.

The self-ignition timing prediction unit 60f is configured to predict the self-ignition timing based on the estimated in-cylinder state and the second deviation dt2. That is, the self-ignition timing prediction unit 60f calculates the predicted self-ignition timing tigp. In one example, the predicted self-ignition timing tigp is calculated using a model. In this case, for example, the in-cylinder pressure when SACI combustion is assumed to be performed under the estimated in-cylinder state is predicted, and the self-ignition timing is predicted from this in-cylinder pressure.

The correction amount calculation unit 60g is configured to calculate the correction amount of the engine control parameter based on the first deviation dt1 and the second deviation dt2. The correction amount is, for example, a value required to make the first deviation dt1 and the second deviation dt2 zero.

The first deviation dt1 is the difference (=tight-tigp) between the target autoignition timing tigt and the predicted autoignition timing tigp. The second deviation dt2 is a difference (=tig-tiga) between the target self-ignition timing tigt and the actual self-ignition timing tiga. In the engine body 2, combustion control is performed using the result of correcting the engine control parameter calculated by the parameter calculation unit 60b with the correction amount calculated by the correction amount calculation unit 60g.

In FIG. 7, an example of an actual in-cylinder pressure detected by the in-cylinder pressure sensor 42 is shown by a solid line PCa, and an example of an in-cylinder pressure predicted by the self-ignition timing predicting unit 60f is shown by a broken line PCp. ing. As shown in FIG. 7, although the first deviation dt1 which is the difference between the target self-ignition timing tigt and the predicted self-ignition timing tigp is relatively large, it is the difference between the target self-ignition timing tigt and the actual self-ignition timing tiga. The certain second deviation dt2 is relatively small. That is, it can be seen that the actual self-ignition timing tiga is brought closer to the target self-ignition timing tigt by the correction amount calculated by the correction amount calculation unit 60g. In FIG. 7, IVC indicates the closing timing of the intake valve 35, BDC indicates the compression bottom dead center, and TDC indicates the compression top dead center.

As described above, in the embodiment according to the present invention, since the correction amount of the engine control parameter is calculated using the first deviation dt1 which is the difference between the target autoignition timing tigt and the predicted autoignition timing tigp, the feedforward control is performed. You can think you are going. At the same time, since the correction amount of the engine control parameter is calculated using the second deviation dt2 which is the difference between the target self-ignition timing tigt and the actual self-ignition timing tiga, it can be considered that feedback control is performed. Further, since the in-cylinder state and the predicted auto-ignition timing tigp are calculated using the second deviation dt2, the error of the model for calculating the in-cylinder state and the predicted auto-ignition timing tigp is reduced by learning. Therefore, the engine control can be performed with higher accuracy.

Now, in order to perform the above-mentioned self-ignition timing control with higher accuracy, it is necessary to more accurately calculate or estimate the actual self-ignition timing tiga. In this respect, a technique is known in which a heat release rate for a crank angle is calculated based on the in-cylinder pressure, and the self-ignition timing is estimated based on this heat release rate. However, in the case of SACI combustion, it is difficult to accurately estimate the self-ignition timing by this technique. This is for the following reason.

In FIG. 8, an example of the heat release rate ROHR calculated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 42 during SACI combustion is shown by a solid line Ra, and the heat release rate component due to flame propagation combustion is shown. Is indicated by a broken line Rfp, and an example of a heat release rate component by compression self-ignition combustion is indicated by a one-dot chain line Rci. As described above, in the SACI combustion, roughly speaking, the flame propagation combustion is first started, and the compression self-ignition combustion is started in the middle of the flame propagation combustion. Therefore, the heat release rate Ra based on the detection result of the in-cylinder pressure sensor 42 corresponds to the sum of the heat release rate component Rfp due to flame propagation combustion and the heat release rate component Rci due to compression self-ignition combustion. In other words, the in-cylinder pressure sensor 42 can detect only the sum of the heat release rate component Rfp due to flame propagation combustion and the heat release rate component Rci due to compression self-ignition combustion. Therefore, it is difficult to accurately specify the start time of the compression ignition combustion, that is, the auto ignition timing CAig.

Therefore, the self-ignition timing estimation unit 60d according to the embodiment of the present invention estimates the self-ignition timing during SACI combustion as follows.

That is, in the embodiment according to the present invention, as shown in FIG. 9, the maximum heat release rate crank angle CAmax, which is the crank angle CA that maximizes the heat release rate ROHR, is calculated. The heat release rate ROHR with respect to the crank angle CA in this case is calculated by the heat release rate calculation unit 60c as described above. Next, the crank angle range RCA is set on the retard side of the maximum heat release rate crank angle CAmax. This crank angle range RCA is, for example, previously obtained as a function of the engine operating state, and is stored in advance in the ROM 52 in the form of a map.

Next, an approximate expression APL that approximates the heat release rate ROHR by a straight line in the crank angle range RCA is determined. Next, the zero heat release rate crank angle CA0, which is the crank angle CA at which the heat release rate ROHR becomes zero in the approximate expression APL, is determined. In other words, the intersection of the approximate expression APL and the straight line of ROHR=0 is set to the zero heat release rate crank angle CA0.

Next, the difference dif (=CA0-CAmax) between the maximum heat release rate crank angle CAmax and the zero heat release rate crank angle CA0 is calculated. Then, the crank angle (=CAmax-dif) advanced from the maximum heat release rate crank angle CAmax by the difference dif is estimated as the self-ignition timing CAig.

The curve representing the heat release rate ROHR when compression self-ignition combustion is performed alone has a relatively high left-right symmetry with respect to the straight line CA=CAmax. Therefore, the crank angle CAig estimated as described above accurately represents the self-ignition timing.

Moreover, as can be seen from FIG. 8, the heat generation based on the output of the in-cylinder pressure sensor 42 is more retarded than the maximum heat generation rate crank angle CAmax and more advanced than the maximum heat generation rate crank angle CAmax. The effect of flame propagation combustion on the rate ROHR is small. In other words, on the retard side of the maximum heat release rate crank angle CAmax, the heat release rate ROHR based on the output of the in-cylinder pressure sensor 42 is on compression ignition rather than on the advance side of the maximum heat release rate crank angle CAmax. Better represents combustion. In the embodiment according to the present invention, as described above, the crank angle range RCA is set on the retard side of the maximum heat release rate crank angle CAmax, so that the self-ignition timing CAig can be estimated with higher accuracy.

FIG. 10 shows the self-ignition timing estimation routine of the embodiment according to the present invention. This routine is executed by interruption every predetermined set time. Referring to FIG. 10, in step 100, the maximum heat release rate crank angle CAmax is calculated. In the following step 101, the crank angle range RCA is set. In the following step 102, the approximate expression APL is determined. In the following step 103, the zero heat release rate crank angle CA0 is calculated. In the following step 104, the difference dif is calculated. In the following step 105, the self-ignition timing CAig is calculated.

Next, another embodiment according to the present invention will be described. In another embodiment according to the present invention, the self-ignition timing during SACI combustion is estimated as follows.

That is, in another embodiment according to the present invention, as shown in FIG. 11, the maximum heat release rate crank angle CAmax, which is the crank angle CA that maximizes the heat release rate ROHR, is calculated. Next, the crank angle range RCA is set so as to include the maximum heat release rate crank angle CAmax. This crank angle range RCA is, for example, previously obtained as a function of the engine operating state, and is stored in advance in the ROM 52 in the form of a map. In another setting example (not shown), the crank angle range RCA is set to the range of the maximum heat release rate crank angle CAmax±constant value. In yet another setting example (not shown), the crank angle range RCA is set to the crank angle range in which the heat release rate ROHR is larger than the threshold value. In this case, the threshold value is set, for example, by multiplying the maximum value Rmax of the heat release rate ROHR by a coefficient r (<1.0) (Rmax·r). An example of the coefficient r is 0.8. It is more preferable to set a crank angle range in which flame propagation combustion is not dominant.

Next, an approximate expression APW that approximates the heat release rate ROHR by the Wiebe function in the crank angle range RCA is determined. The Wiebe function is represented by the following equation (1), for example. In the formula (1), a represents a constant (for example, 6.9), CAp represents a combustion period, and m represents a shape parameter.
ROHR
=(dQ/dCA)/QT
=a/CAp·(m+1)·{(CA-CAig)/CAp}^m
.Exp[-a.{(CA-CAig)/CAp}^(m+1)] (1)

As can be seen from FIG. 11, the approximate expression APW has two crank angles CA at which the heat release rate ROHR becomes zero. In another embodiment according to the present invention, of the two crank angles CA at which the heat release rate is zero in the approximate expression APW, the crank angle CAig on the advance side of the maximum heat release rate crank angle CAmax is estimated as the self-ignition timing. To be done.

The Wiebe function can approximate the heat release rate with higher accuracy. Therefore, the crank angle CAig estimated as described above accurately represents the self-ignition timing.

FIG. 12 shows an autoignition timing estimation routine according to another embodiment of the present invention. This routine is executed by interruption every predetermined set time. Referring to FIG. 12, in step 200, the maximum heat release rate crank angle CAmax is calculated. In the following step 201, the crank angle range RCA is set. In the following step 202, the approximate expression APW is determined. In the following step 203, the self-ignition timing CAig is calculated.

1 Internal Combustion Engine 40 Fuel Injection Valve 41 Spark Plug 42 Cylinder Pressure Sensor 50 Electronic Control Unit 50d Ignition Assisted Auto Ignition Combustion Control Section 60c Heat Release Rate Calculation Section 60d Auto Ignition Timing Estimation Section

Claims (2)

A fuel injection valve configured to supply fuel into the cylinder;
A spark plug configured to ignite fuel,
The main fuel for forming the premixed mixture in the cylinder is injected by the fuel injection valve, then the assist fuel is injected in the cylinder and the assist fuel is ignited by the spark plug, and then the premixed mixture is compressed. An ignition assist self-ignition combustion control unit configured to perform ignition combustion,
An in-cylinder pressure sensor configured to detect the in-cylinder pressure,
A heat release rate calculation unit configured to calculate a heat release rate for a crank angle based on the in-cylinder pressure;
An autoignition timing estimation unit configured to estimate the autoignition timing based on the heat release rate,
Equipped with
The self-ignition timing estimation unit,
The heat generation rate is a crank angle that is the maximum crank angle is determined to determine an approximate expression that approximates the heat generation rate by a straight line in the crank angle range set to the retard side of the crank angle,
The zero heat release rate crank angle, which is the crank angle at which the heat release rate is zero in the approximate expression, is determined,
Calculate the difference between the maximum heat release rate crank angle and the zero heat release rate crank angle,
Estimating the crank angle advanced by the difference from the maximum heat release rate crank angle as the self-ignition timing,
A self-ignition timing estimation device for an internal combustion engine configured as described above. A fuel injection valve configured to supply fuel into the cylinder;
A spark plug configured to ignite fuel,
The main fuel for forming the premixed mixture in the cylinder is injected by the fuel injection valve, then the assist fuel is injected in the cylinder and the assist fuel is ignited by the spark plug, and then the premixed mixture is compressed. An ignition assist self-ignition combustion control unit configured to perform ignition combustion,
An in-cylinder pressure sensor for detecting the in-cylinder pressure,
A heat release rate calculator configured to calculate a heat release rate for a crank angle based on the in-cylinder pressure;
An autoignition timing estimation unit configured to estimate the autoignition timing based on the heat release rate,
Equipped with
The self-ignition timing estimation unit,
Determining an approximate expression approximating the heat release rate by a Wiebe function in a crank angle range set so as to include the maximum heat release rate crank angle, which is the crank angle at which the heat release rate becomes maximum;
In the approximation formula, the heat release rate becomes zero, and the crank angle on the advance side of the maximum heat release rate crank angle is estimated as the self-ignition timing.
A self-ignition timing estimation device for an internal combustion engine configured as described above.

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