JP6168231B2 - Control device for premixed compression self-ignition internal combustion engine - Google Patents

Description

  The present invention relates to a control device for a premixed compression self-ignition internal combustion engine.

  In recent years, a premixed compression self-ignition internal combustion engine that uses premixed compression self-ignition combustion in which high-temperature burned gas is introduced into a cylinder to self-ignite an air-fuel mixture has been proposed. Such premixed compression self-ignition combustion is called HCCI (Homogeneous Charge Compression Ignition) combustion, and is used as one of the combustion forms of a gasoline engine or a diesel engine.

  In HCCI combustion, an air-fuel mixture in a cylinder is compressed and heated to a high temperature and pressure, so that the air-fuel mixture is self-ignited regardless of spark ignition. HCCI combustion is combustion in which ignition is performed simultaneously and frequently at various locations in the cylinder, and has the advantage that the combustion period is short and higher thermal efficiency is obtained.

  Therefore, for example, in a gasoline engine, improvement in fuel efficiency is expected mainly by using HCCI combustion. Further, in diesel engines, reduction of soot and nitrogen oxides is expected mainly by using HCCI combustion.

  On the other hand, the self-ignition timing of a premixed compression self-ignition internal combustion engine using HCCI combustion varies greatly depending on various in-cylinder state quantities such as in-cylinder temperature, in-cylinder pressure, air amount, residual gas amount, and fuel amount. To do. Therefore, in the premixed compression self-ignition internal combustion engine, there is a problem in that combustion cannot be performed at an optimal time unless the self-ignition timing is accurately controlled, and knocking or misfire is likely to occur. Here, in order to accurately control the self-ignition timing, it is necessary to estimate an accurate self-ignition timing and combustion timing in HCCI combustion.

  Conventionally, those described in Patent Documents 1 to 3 are known as premixed compression self-ignition internal combustion engines for estimating the self-ignition timing and combustion timing in HCCI combustion.

  In the premixed compression self-ignition internal combustion engine described in Patent Document 1, the amount of fuel injected in the preceding stroke, the average pressure, and the combustion center of gravity in the preceding stroke are adjusted. The combustion center of gravity is estimated from the relational expression based on the instantaneous value and various adjustment factors.

  The premixed compression self-ignition internal combustion engine described in Patent Document 2 estimates the ignition delay period using the Arrhenius equation based on coefficients corresponding to the in-cylinder pressure, the in-cylinder temperature, the air-fuel ratio, and the like.

  The premixed compression self-ignition internal combustion engine described in Patent Document 3 estimates an ignition delay period using an Arrhenius equation based on in-cylinder pressure, activation energy, in-cylinder absolute temperature, gas constant, and various constants. .

JP 2009-168027 A JP 2006-2638 A JP 2008-101591 A

  However, in the HCCI combustion, the self-ignition timing and the combustion timing are physical factors such as temperature distribution due to turbulent mixing and wall heat loss, for example, with respect to the ignition delay time controlled by the chemical reaction of low temperature oxidation reaction and high temperature oxidation reaction. Is governed by the influence. In addition, in the chemical reaction rate in HCCI combustion, in addition to the in-cylinder pressure, for example, an equivalence ratio, a residual gas ratio, and the like greatly affect.

  However, in the premixed compression self-ignition internal combustion engine described in Patent Documents 1 to 3 described above, HCCI combustion is performed in consideration of all the above-described physical factors and factors affecting the chemical reaction rate. It does not estimate the auto-ignition timing or combustion timing in Japan. Therefore, in the premixed compression self-ignition internal combustion engine described in Patent Documents 1 to 3 above, it cannot be said that the estimation accuracy of the self-ignition timing and the combustion timing in HCCI combustion is necessarily high.

  Therefore, an object of the present invention is to provide a control device for a premixed compression self-ignition internal combustion engine capable of improving the estimation accuracy of the self-ignition timing and the combustion timing in HCCI combustion as compared with the prior art.

  A control device according to the present invention that solves the above-described problems is a control device for a premixed compression self-ignition internal combustion engine that self-ignites and burns by compressing an air-fuel mixture in a cylinder. The gas based on the in-cylinder pressure at CA, the equivalence ratio, the in-cylinder mixture amount, the in-cylinder pressure and the exhaust temperature when the intake valve is opened, and the volume of the combustion chamber when the in-cylinder pressure and the exhaust temperature are detected The ratio of the residual gas amount calculated using the equation of state is the frequency factor of the Arrhenius equation, and the premixed compression self-compression using the frequency factor and the in-cylinder temperature at 10 ° CA before compression top dead center is used in the Arrhenius equation. The time when 50% of the fuel injected in the cylinder in the ignition internal combustion engine is consumed is estimated, and the premixed compression self-ignition internal combustion engine is controlled so that the estimated time becomes the target combustion timing.

  The present invention can provide a control device for a premixed compression self-ignition internal combustion engine capable of improving the estimation accuracy of the self-ignition timing and combustion timing in HCCI combustion as compared with the prior art.

FIG. 1 is a configuration diagram showing an outline of a vehicle to which a control device according to a first embodiment of the present invention is applied. FIG. 2 is a block diagram showing an outline of combustion timing estimation control in the first embodiment of the present invention. FIG. 3 is a flowchart showing a flow of processing of combustion timing estimation control and ignition timing control executed by the ECU according to the first embodiment of the present invention. FIG. 4 is a diagram comparing the estimation accuracy of the combustion timing with that of the prior art, (a) is the estimation accuracy of the combustion timing by the control device according to the first embodiment of the present invention, and (b) is the conventional accuracy. The estimation accuracy of the combustion timing by the control device is shown. FIG. 5 is a flowchart showing a flow of processing of combustion timing estimation control and ignition timing control executed by the ECU according to the second embodiment of the present invention. FIG. 6 is a flowchart showing a flow of processing of combustion timing estimation control and ignition timing control executed by the ECU according to the third embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(First embodiment)

  As shown in FIG. 1, the vehicle 1 according to the present embodiment includes an engine 2, an intake pipe 3, an exhaust pipe 4, an EGR device 5, and an ECU 10 as a control device.

  The engine 2 is composed of, for example, an inline 4-cylinder gasoline engine. The engine 2 is a so-called direct injection engine provided with an injector 23 for injecting fuel directly into the cylinder 21, that is, into the combustion chamber. Note that the number of cylinders of the engine 2 is not limited to four. The engine 2 is not limited to a gasoline engine but may be a diesel engine.

  In addition, the engine 2 according to the present embodiment does not rely on the spark plug 20 but premixed compression self-ignition combustion (hereinafter referred to as “HCCI combustion”) in which the air-fuel mixture in the cylinder 21 is compressed and burned by compression. Is a premixed compression self-ignition internal combustion engine.

  Further, the engine 2 is configured to be capable of SI (Spark Ignition) combustion in which the air-fuel mixture is forcibly ignited by spark discharge from the spark plug 20. Therefore, the engine 2 can switch between HCCI combustion and SI combustion according to the engine operating state such as the engine speed and the engine load.

  An intake passage 3 a is formed inside the intake pipe 3. A supercharger 30 and an intercooler 31 are provided on the intake passage 3a. The supercharger 30 is a so-called mechanical supercharger that compresses and supercharges intake air by two rotors rotating in conjunction with each other in a housing. The supercharger 30 uses the engine 2 as a drive source.

  The intercooler 31 is provided downstream of the supercharger 30 in the intake direction, and cools the intake air compressed by the supercharger 30. This increases the volumetric efficiency of the intake air and improves the suction efficiency.

  An exhaust passage 4 a is formed inside the exhaust pipe 4. A catalyst 40 is provided on the exhaust passage 4a. The catalyst 40 purifies the exhaust gas discharged from the engine 2.

  The EGR device 5 includes an EGR pipe 50 in which an EGR passage 50a is formed, and an EGR valve 51. The EGR passage 50a is a passage that connects the exhaust passage 4a and the intake passage 3a and recirculates a part of the exhaust gas flowing through the exhaust passage 4a to the intake passage 3a.

  The EGR valve 51 is provided on the EGR passage 50a and adjusts an EGR amount that is an amount of exhaust gas recirculated to the intake passage 3a. The EGR valve 51 is controlled to open and close by the ECU 10.

  The ECU 10 includes, for example, a microcomputer including a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM and performs signal processing according to a program stored in advance in the ROM. . Various control constants and various maps are stored in advance in the ROM.

On the input side of the ECU 10, an airflow sensor 101, an intake air temperature sensor 102, an intake air pressure sensor 103, an intake air O ₂ sensor 104, an in-cylinder pressure sensor 105, an exhaust gas temperature sensor 106, a linear A / F sensor 107, a crank angle sensor 180. Various sensors such as a water temperature sensor 181 are connected.

  The airflow sensor 101 is provided on the intake passage 3a upstream of the supercharger 30 in the intake direction, and detects the intake air amount. The intake air temperature sensor 102 is provided on the intake passage 3a downstream of the intercooler 31 in the intake direction, and detects an intake air temperature (hereinafter simply referred to as “intake air temperature”) that is the temperature of the intake air.

The intake pressure sensor 103 is provided on the intake passage 3a downstream of the intercooler 31 in the intake direction, and detects intake pressure that is the pressure of intake air. The intake O ₂ sensor 104 is provided on the intake passage 3 a downstream of the intercooler 31 in the intake direction, and detects the oxygen concentration of the gas sucked into the cylinder 21.

  The in-cylinder pressure sensor 105 is provided in a cylinder head (not shown) that forms the cylinder 21 and detects an in-cylinder pressure that is a pressure in the cylinder 21. The exhaust temperature sensor 106 is provided on the exhaust passage 4a upstream of the catalyst 40 in the exhaust direction, and detects an exhaust temperature (hereinafter simply referred to as “exhaust temperature”) that is the temperature of the exhaust gas.

  The linear A / F sensor 107 is an A / F sensor that is provided on the exhaust passage 4a upstream of the catalyst 40 in the exhaust direction and has a linear output characteristic proportional to the air-fuel ratio of the exhaust gas. The linear A / F sensor 107 detects the air-fuel ratio of the exhaust gas based on the oxygen concentration in the exhaust gas discharged from the cylinder 21.

  The crank angle sensor 180 is provided in the engine 2 and detects the crank angle of the crankshaft of the engine 2. The water temperature sensor 181 is provided in the engine 2 and detects the temperature of the cooling water of the engine 2, that is, the cooling water temperature.

  Various devices such as an EGR valve 51, a spark plug 20, and an injector 23 are connected to the output side of the ECU 10. The ECU 10 controls the various devices described above based on the inputs from the various sensors described above.

  For example, the ECU 10 performs combustion timing estimation control for estimating the combustion timing of HCCI combustion in the engine 2 based on the input from the various sensors described above. Further, the ECU 10 performs ignition timing control for controlling the injector 23 and the spark plug 20 so that HCCI combustion is performed at an optimal time in the engine 2 based on the combustion timing estimated by the combustion timing estimation control. Yes.

  Next, the combustion timing estimation control and the ignition timing control executed by the ECU 10 will be described with reference to FIG.

  As shown in FIG. 2, the ECU 10 calculates the engine speed Ne based on the detection result input from the crank angle sensor 180. Further, the ECU 10 calculates the engine load based on the accelerator opening inputted from the accelerator opening sensor.

  The ECU 10 calculates a basic fuel injection amount based on the engine speed Ne, the engine load, and the intake air amount detected by the airflow sensor 101. Further, the ECU 10 calculates an equivalence ratio φ that is a ratio between the air-fuel ratio of the air-fuel mixture sucked into the engine 2 and the stoichiometric air-fuel ratio based on the basic fuel injection amount and the intake air amount.

The ECU 10 uses the EGR device 5 to return to the intake side based on the intake air amount, the oxygen concentration detected by the intake O ₂ sensor 104, and the equivalent ratio determined based on the actual air-fuel ratio detected by the linear A / F sensor 107. The amount of exhaust gas (hereinafter referred to as external EGR gas amount) is calculated.

Here, the ratio of oxygen (O ₂ ), nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and the like in the air is known because it is the composition of air. For this reason, the oxygen concentration in the intake air amount detected by the airflow sensor 101 is also known. Therefore, the ECU 10 can detect the external EGR gas amount by detecting the oxygen concentration of the intake air including the exhaust gas having the oxygen concentration detected by the linear A / F sensor 107 by the intake O ₂ sensor 104.

  The ECU 10 is based on the in-cylinder pressure and the exhaust temperature detected by the in-cylinder pressure sensor 105 and the exhaust temperature sensor 106 when the intake valve is opened, and the volume of the combustion chamber when the in-cylinder pressure and the exhaust temperature are detected. The mass of the residual gas is calculated as the residual gas amount using the gas equation of state. The equation of state of the gas is that the in-cylinder pressure is “P”, the combustion chamber volume is “V”, the residual gas mass is “m”, the residual gas constant is “R”, and the exhaust gas temperature substantially matches the in-cylinder temperature. Is represented by “PV = mRT”.

The ECU 10 calculates a residual gas ratio X _rg based on the external EGR gas amount and the residual gas amount. Specifically, the ECU 10 calculates a residual gas ratio X _rg that is a ratio of the residual gas amount to the in-cylinder mixture amount that is the sum of the external EGR gas amount, the residual gas amount, the intake air amount, and the basic fuel injection amount. .

The ECU 10 calculates the in-cylinder pressure P _{cyl — 10BTDC} based on the external EGR gas amount, the intake air amount, the basic fuel injection amount, the residual gas amount, and the in-cylinder pressure. Here, “cyl” indicates that the cylinder is in the cylinder, and “10BTDC” indicates that the timing is 10 ° CA before compression top dead center.

Specifically, when the in-cylinder pressure is detected using the in-cylinder pressure sensor 105, the ECU 10 calculates the in-cylinder pressure P _{cyl — 10BTDC} as follows. That, ECU 10, for example assuming a polytropic change, by using the volume _{V Cyl_10BTDC} the combustion chamber in the cylinder pressure _{P Cyl_ivc} the combustion chamber volume _{V Cyl_ivc} the compression top dead center 10 ° CA during closing of the intake valve In-cylinder pressure P _{cyl — 10BTDC} is calculated based on the following formula (1). Here, “ivc” indicates when the intake valve is closed. Further, “n” in the following formula (1) is a polytropic index.
Further, the ECU 10 can also _calculate the in-cylinder temperature T _{cyl — 10BTDC} based on the following equation (2), similarly to the above-mentioned in-cylinder pressure P _{cyl — 10BTDC} .

Here, the in-cylinder temperature T _{cyl_ivc} in the above equation (2) is the in-cylinder pressure P _{cyl_ivc} when the intake valve is closed, the volume V _{cyl_ivc of the} combustion chamber, the mass m of the in-cylinder mixture, and the gas of the mixture Using the constant R, the ECU 10 _obtains the gas state equation “P _{cyl_ivc} V _{cyl_ivc} = mRT”.

The gas constant R of the air-fuel mixture is calculated by calculating the average molecular weight of the gas from the molar fraction that is the mass ratio of each gas such as external EGR gas, residual gas, and air-fuel mixture of intake air and fuel. By dividing the general gas constant (R = 8.3144621 (75) JK ⁻¹ mol ⁻¹ ). The in-cylinder temperature T _{cyl_ivc} may be obtained using the law of energy conservation.

When the in-cylinder pressure sensor 105 is not used, the ECU 10 can also calculate the in-cylinder pressure P _{cyl_ivc} and the in-cylinder temperature T _{cyl_ivc} using the following equations (3) and (4), respectively. .

Here, M _air in the above equation (3) is the amount of intake air detected by the airflow sensor 101, and P _{in_ivc} is the intake pressure when the intake valve is closed. In addition, T _{in_ivo} in the above equation (4) is the intake air temperature when the intake valve is opened, T _{ex_ivo} is the exhaust temperature when the intake valve is opened, and T _water is the cooling water temperature detected by the water temperature sensor 181. is there.

  In addition, the indexes J and K in the above equation (3) are values obtained by multiple regression analysis based on values obtained experimentally in advance in consideration of individual differences due to the specifications of the engine 2 and the like. Further, the coefficients I, L, N, and Q in the above formulas (3) and (4) are values obtained experimentally in advance in consideration of individual differences due to the specifications of the engine 2 and the like, similar to the indices J and K. This is the value obtained by multiple regression analysis.

  Further, the ECU 10 estimates the combustion timing CA50 of the engine 2 using the combustion reaction parameter and the fuel state parameter as frequency factors in the Arrhenius equation. In the present embodiment, the crank angle CA50 at the time when 50% of the fuel is consumed is handled as the combustion timing CA50.

  Here, the combustion timing of the premixed compression self-ignition internal combustion engine such as the engine 2 is due to turbulent mixing and wall heat loss with respect to the ignition delay time limited by the chemical reaction of the low temperature oxidation reaction and the high temperature oxidation reaction. It is governed by the influence of physical factors such as temperature distribution. For this reason, in order to estimate the exact combustion timing, it is necessary to consider the physical factors as described above and factors that influence the chemical reaction rate.

  Therefore, in the present embodiment, in order to improve the estimation accuracy of the combustion timing, the above-mentioned combustion reaction parameters and fuel state parameters are used as frequency factors in the Arrhenius equation that defines the speed of the chemical reaction at a certain temperature. did.

As the above-described combustion reaction parameters, the cylinder pressure P _{cyl — 10BTDC} calculated by the above equation (1) as the pressure state value based on the cylinder pressure, the residual gas ratio X as the burned gas state value based on the amount of burned gas in the cylinder 21 _rg , and the equivalence ratio φ calculated based on the basic fuel injection amount and the intake air amount are included. Here, the equivalence ratio φ of the present embodiment corresponds to a fuel ratio value based on the state of the fuel amount in the cylinder 21 and the air amount. The fuel ratio value may be the reciprocal of the equivalent ratio φ representing the excess air ratio.

In addition, as the above-described fuel state parameters, the reciprocal of the engine speed Ne as a mixed estimated value for estimating the mixed state of the fuel in the cylinder 21, the fuel injection end timing EoI, and the wall surface in the cylinder 21 and the fuel A deviation (T _ex −T _in ) between the exhaust temperature T _ex and the intake air temperature T _in as a heat loss estimation value for estimating heat loss due to heat transfer is included. The mixture estimated value may be the engine speed Ne.

Specifically, the ECU 10 calculates the combustion timing CA50 using the following equation (5) based on the above-described combustion reaction parameters, each fuel state parameter, and the in-cylinder temperature T _{cyl — 10BTDC} calculated by the above equation (2). .

  Here, R in the above equation (5) is a gas constant of the air-fuel mixture, and A is obtained by multiple regression analysis based on a value obtained experimentally in advance considering individual differences due to the specifications of the engine 2 and the like. It is a coefficient.

  Further, in the above equation (5), predetermined indices B to D and F to H are assigned to the combustion reaction parameters and the fuel state parameters, respectively. Like the coefficient A, these indices B to D and F to H are values obtained by multiple regression analysis based on values obtained experimentally in advance in consideration of individual differences due to the specifications of the engine 2 and the like.

  Further, the ECU 10 compares the target combustion timing obtained from the target combustion timing map with the combustion timing CA50 calculated using the above equation (5), and based on the comparison result, the fuel injection amount, the fuel injection timing, and the ignition timing. And the number of times of ignition are determined. The target combustion time map is a map for determining the target combustion time using, for example, the engine speed Ne as a parameter, and the relationship between the engine speed Ne and the combustion time is experimentally obtained in advance and stored in the ROM of the ECU 10. .

  The target combustion timing is represented by a crank angle, and is the target crank angle CA50 at the time when 50% of the fuel is consumed, as in the combustion timing CA50. Therefore, in the following, the target crank angle CA50 will be treated as the target combustion timing CA50.

  Specifically, the ECU 10 determines the fuel injection amount, the fuel injection timing, the ignition timing, and the number of ignitions depending on whether or not the combustion timing CA50 matches the target combustion timing CA50. Here, the fact that the combustion timing CA50 coincides with the target combustion timing CA50 includes, for example, that the combustion timing CA50 is within a predetermined threshold with respect to the target combustion timing CA50, in addition to the case where the combustion timing CA50 completely coincides. The predetermined threshold is arbitrarily determined according to the specifications of the engine 2 or the like, but is ± 1 ° CA, for example.

  For example, when the combustion timing CA50 coincides with the target combustion timing CA50, the ECU 10 determines the fuel injection amount, the fuel injection timing determined by a predetermined injection amount map, injection timing map, ignition timing map, ignition frequency map, and the like. The drive of the injector 23 and the spark plug 20 is controlled so that fuel injection and ignition are performed at the ignition timing and the number of ignitions.

  On the other hand, when the combustion timing CA50 does not coincide with the target combustion timing CA50, the ECU 10 determines the fuel injection amount, the fuel injection timing, the ignition timing, and the ignition timing by increasing or decreasing the fuel injection amount, the advance or retard of the ignition timing, and the like. The number of times is corrected. In this case, the ECU 10 controls the drive of the injector 23 and the spark plug 20 so as to perform fuel injection and ignition with the corrected fuel injection amount, fuel injection timing, ignition timing, and number of ignitions.

  Next, with reference to FIG. 3, the flow of processing of combustion timing estimation control and ignition timing control executed by the ECU 10 will be described. This combustion timing estimation control and ignition timing control are repeatedly executed by the ECU 10 at predetermined time intervals.

  As shown in FIG. 3, the ECU 10 first determines based on the detection result input from the crank angle sensor 180 whether or not it is timing of various calculations performed by the combustion timing estimation control and ignition timing control, and measurement by various sensors. Is determined (step S1). If the ECU 10 determines that it is not the timing of various calculations and measurements by various sensors, it repeats the process of step S1 again.

  On the other hand, when it is determined that it is the timing of various calculations and measurement by various sensors, the ECU 10 detects the engine operating state such as the engine speed Ne and the accelerator opening (step S2).

Next, the ECU 10 detects various sensor values used in the combustion timing estimation control and the ignition timing control such as the intake air amount, the intake air temperature T _in , the exhaust gas temperature T _ex , and the cooling water temperature T _water (step S3).

  Thereafter, the ECU 10 calculates a basic fuel injection amount based on the engine speed Ne, the engine load, and the intake air amount (step S4). Next, the ECU 10 calculates the combustion timing CA50 using the above equation (5) (step S5).

  Next, the ECU 10 determines whether or not the combustion timing CA50 coincides with the target combustion timing CA50 (step S6). As described above, whether or not the combustion timing CA50 matches the target combustion timing CA50 depends on whether or not the combustion timing CA50 completely matches the target combustion timing CA50, or whether the combustion timing CA50 matches the target combustion timing CA50. The determination is made based on whether or not it is within a predetermined threshold.

  If the ECU 10 determines that the combustion timing CA50 coincides with the target combustion timing CA50, the ECU 10 ends this process. In this case, the ECU 10 performs fuel injection and ignition with a fuel injection amount, a fuel injection timing, an ignition timing, and an ignition frequency determined by a predetermined injection amount map, injection timing map, ignition timing map, ignition frequency map, and the like. Thus, the drive of the injector 23 and the spark plug 20 is controlled.

  On the other hand, if the ECU 10 determines that the combustion timing CA50 does not coincide with the target combustion timing CA50, whether or not the combustion timing CA50 is greater than the target combustion timing CA50, that is, the combustion timing CA50 is equal to the target combustion timing CA50. It is determined whether or not the angle is retarded (step S7).

  If the ECU 10 determines that the combustion timing CA50 is retarded with respect to the target combustion timing CA50, the ECU 10 corrects the advance of the combustion timing CA50 (step S8). Specifically, the ECU 10 corrects the fuel injection amount, the fuel injection timing, the ignition timing, and the number of ignitions, for example, by increasing the fuel injection amount, the advance angle of the ignition timing, etc. so as to advance the combustion timing CA50. Thereby, the combustion timing CA50 is corrected to the advance side.

  On the other hand, when the ECU 10 determines that the combustion timing CA50 is not retarded, that is, advanced, with respect to the target combustion timing CA50, the ECU 10 corrects the retardation of the combustion timing CA50 (step S9). Specifically, the ECU 10 corrects the fuel injection amount, the fuel injection timing, the ignition timing, and the number of ignitions, for example, by reducing the fuel injection amount, retarding the ignition timing, etc. so as to retard the combustion timing CA50. As a result, the combustion timing CA50 is corrected to the retard side.

  The correction values such as the fuel injection amount and ignition timing used in steps S8 and S9 are values obtained experimentally in advance, and are stored in the ROM of the ECU 10 as a correction map such as the fuel injection amount and ignition timing, for example. Has been.

  Next, after the combustion timing CA50 is corrected in step S8 and step S9, the ECU 10 calculates the corrected combustion timing CA50 again in step S5, and whether or not the corrected combustion timing CA50 matches the target combustion timing CA50. Determine whether. Thus, in the present embodiment, the corrected combustion timing CA50 is corrected until the corrected combustion timing CA50 matches the target combustion timing CA50.

  Next, the estimation accuracy of the combustion timing CA50 in the control apparatus according to the present embodiment will be described with reference to FIG. FIG. 4 shows a comparison between the estimation accuracy of the combustion timing CA50 estimated using the above equation (5) and the estimation accuracy of the combustion timing CA50 estimated using the conventional Arrhenius equation in the control device of the present embodiment. It is a thing.

  In FIG. 4A, the horizontal axis indicated by “CA50 Calculated deg. ATDC” in the figure is the combustion timing CA50 estimated using the above equation (5), and the vertical axis indicated by “CA50 Measured deg. ATDC” in the figure. The axis indicates the combustion timing CA50 actually measured.

  4B, the horizontal axis indicated by “CA50 Calculated deg. ATDC” in the figure indicates the combustion timing CA50 estimated by using the conventional Arrhenius equation, and “CA50 Measured deg. ATDC” in the figure. The vertical axis represents the actually measured combustion time CA50. These combustion times CA50 are all after top dead center.

  4 (a) and 4 (b) are graphs showing the correlation between the estimated combustion timing CA50 and the actually measured combustion timing CA50, respectively, and each plot in the graph is a solid line (slope) shown in the figure. Indicates that the correlation between the estimated combustion timing CA50 and the actually measured combustion timing CA50 is higher, that is, the estimation accuracy of the combustion timing CA50 is higher.

The degree of such correlation may be represented by coefficient of determination R ^2, coefficient of determination closer R ² is "1", higher correlation with actual measured combustion timing and the estimated combustion timing CA50 CA50 Is shown. Therefore, the estimation accuracy of combustion timing CA50 is the coefficient of determination ^{R 2} is higher the closer to "1".

Here, the determination coefficient R ^{2 in the} graph shown in FIG. 4A is “0.9675”, which is closer to “1” than the determination coefficient R ² = 0.698 in the graph shown in FIG. Value. Therefore, as is apparent from FIGS. 4A and 4B, the estimation accuracy of the combustion timing CA50 estimated using the above equation (5) is estimated using the conventional Arrhenius equation. It can be seen that it is higher than the accuracy.

  Therefore, it can be said that the control device according to the present embodiment has higher estimation accuracy of the combustion timing CA50 than the control device that estimates the combustion timing CA50 using the conventional Arrhenius equation.

  As described above, the control device according to the present embodiment performs the calculation using the combustion reaction parameter and the fuel state parameter that affect the change of the combustion timing CA50 in the Arrhenius equation for estimating the combustion timing CA50. Thus, it is possible to estimate the combustion timing CA50 that is more accurate than in the past.

  Since the control device according to the present embodiment performs calculations using a plurality of combustion reaction parameters and a plurality of fuel state parameters in the Arrhenius equation, the combustion timing can be accurately determined even when the operating state of the engine 2 changes. CA50 can be estimated.

  As described above, the control device according to the present embodiment can improve the estimation accuracy of the self-ignition timing and the combustion timing CA50 in HCCI combustion, as compared with the related art.

  Further, the control device according to the present embodiment can estimate combustion timing CA50 more accurately because a predetermined index is assigned to each combustion reaction parameter and each fuel condition parameter.

  For example, if an index assigned to each combustion reaction parameter and each fuel condition parameter is experimentally obtained in advance, individual differences due to the specifications of the engine 2 can be absorbed, and the combustion timing CA50 can be estimated with high accuracy. it can.

Further, the control device according to the present embodiment uses the residual gas ratio X _rg as the burned gas state value. The residual gas includes nitrogen oxides, partially oxidized fuel, and the like, and has different specific heat ratios and temperatures that are thermodynamic properties of fresh air, that is, intake air.

For this reason, the residual gas amount changes the temperature rise in the cylinder 21 and the scientific characteristics of combustion, and affects the combustion timing CA50. Therefore, since the control apparatus according to the present embodiment uses the residual gas ratio X _rg for the calculation of the Arrhenius equation, it is possible to improve the estimation accuracy of the combustion timing CA50.

  Further, the control device according to the present embodiment uses the engine speed Ne as the mixture estimated value. Here, it is known that the fuel mixing state affects the combustion speed, and the mixing degree changes depending on the engine speed Ne.

  Therefore, the control device according to the present embodiment uses the engine speed Ne that can estimate the fuel mixture state for the calculation of the Arrhenius equation, so that the estimation accuracy of the combustion timing CA50 can be improved.

Furthermore, the control device according to the present embodiment uses a deviation between the exhaust temperature T _ex and the intake air temperature T _in as the estimated heat loss. Here, the deviation between the exhaust gas temperature T _ex and the intake air temperature T _in correlates with the distribution of the gas temperature generated in the cylinder 21. Further, it is known that the distribution of gas temperature generated in the cylinder 21 affects the combustion timing CA50.

Therefore, the control device according to the present embodiment uses the deviation between the exhaust gas temperature T _ex and the intake air temperature T _in for the calculation of the Arrhenius equation _in order to consider the influence of the distribution of the gas temperature generated in the cylinder 21. The estimation accuracy of the time CA50 can be improved.

  In the present embodiment, all of the combustion reaction parameters and the fuel state parameters are used for estimating the combustion timing CA50 according to the equation (5). However, the present invention is not limited to this. When an engine having a relatively small equivalence ratio distribution is used, the following equation (6) to equation (8) in which the influence of the temperature distribution in the cylinder 21 and the equivalence ratio distribution is excluded from the equation (5) is used to estimate the combustion timing CA50. You may use for.

  Further, when an engine having a small influence such as turbulent mixing is used as the engine 2, the following equation (9) in which the term related to the engine speed Ne is omitted from the equation (5) may be used for estimating the combustion timing CA50. Good.

  Expressions (6) to (9) listed above are examples in which the combustion reaction parameter and the fuel state parameter in Expression (5) are changed according to the specifications of the engine 2 and the like, and are limited to this. It is not a thing.

For example, the control device according to the present embodiment may use at least two combustion reaction parameters among the in-cylinder pressure P _{cyl — 10BTDC} , the residual gas ratio X _rg , and the equivalent ratio φ in Expression (5).

Further, the control device according to the present embodiment, in equation (5), at least one combustion reaction parameter among the in-cylinder pressure P _{cyl — 10BTDC} , the residual gas ratio X _rg , and the equivalence ratio φ, the engine speed Ne, and the injection end timing EOI, and may be used at least one fuel state parameter of the deviation _(T ex _{-T in).}

  In addition, the control device according to the present embodiment corrects the ignition timing and the number of times of ignition when performing the advance angle correction and the retard angle correction of the combustion timing CA50. Instead, the configuration may be such that only the fuel injection amount and the fuel injection timing are corrected.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG.

  This embodiment differs from the first embodiment described above in part of the combustion timing estimation control and the ignition timing control, but the other configurations and processing contents are the same as those of the first embodiment. . Therefore, in the following, description of the same configuration and processing contents as those of the first embodiment will be omitted, and only portions different from those of the first embodiment will be described.

  In the combustion timing estimation control and ignition timing control, in the first embodiment, the ECU 10 determines that the combustion timing CA50 after the advance angle correction and the retard angle correction in steps S8 and S9 in FIG. The combustion timing CA50 was repeatedly corrected until it coincided with CA50.

  On the other hand, ECU 10 according to the present embodiment performs correction of combustion timing CA50 only once in steps S18 and S19 without repeating correction of combustion timing CA50.

  Specifically, as shown in FIG. 5, the ECU 10 according to the present embodiment corrects the advance angle of the combustion timing CA50 in step S18, and then ends this process. Further, the ECU 10 according to the present embodiment ends the present process after correcting the retard of the combustion timing CA50 in step S19.

  In step S18, for example, the ECU 10 refers to a correction map in which the relationship between the deviation between the combustion timing CA50 and the target combustion timing CA50, the fuel injection amount increase amount, the ignition timing advance amount, and the like is defined. Thus, the advance angle correction of the combustion timing CA50 can be performed in one process. The aforementioned correction map is experimentally obtained in advance and stored in the ROM of the ECU 10.

  Also in step S19, as in step S18, the ECU 10 is a correction in which the relationship between the deviation between the combustion timing CA50 and the target combustion timing CA50, the fuel injection amount reduction amount, the ignition timing retardation amount, and the like is defined. By referring to the map, the retard correction of the combustion timing CA50 can be performed in one process.

  In addition, since the content of each step of FIG.5 S11-step S19 is the same as the content of each step of FIG.3 S1 in FIG. 3 in 1st Embodiment, in this Embodiment, Description is omitted.

  As described above, the control device according to the present embodiment has the following operational effects in addition to the operational effects of the first embodiment. That is, since the control device according to the present embodiment is configured to correct the combustion timing CA50 only once in steps S18 and S19, the correction of the combustion timing CA50 is not repeated and the processing load on the ECU 10 is reduced. can do.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.

  In the first embodiment described above, the fuel injection amount, the fuel injection timing, the ignition timing, and the fuel injection amount are increased or decreased and the ignition timing is advanced or retarded so that the combustion timing CA50 becomes the optimal timing. The number of ignitions was corrected.

  However, when such correction is performed to set the combustion timing CA50 to an optimal timing, the combustion period is shortened, which may cause a problem in noise and engine strength. The combustion period is shortened in this way because, for example, the pressure increase rate dP / dCA of the in-cylinder pressure increases.

  Therefore, in the present embodiment, the ECU 10 performs the combustion period CA10-CA90, the maximum in-cylinder pressure Pmax, and the pressure increase rate dP / dCA in the same manner as the estimation method of the combustion timing CA50 of the first embodiment described above. Is estimated. Combustion period CA10-CA90 is the time from when 10% of combustion in cylinder 21 is consumed to the time when 90% is consumed, that is, the crank angle.

  Further, the ECU 10 reduces the fuel injection amount and retards the ignition timing based on the estimated pressure increase rate dP / dCA. Thereby, the in-cylinder pressure is reduced and an increase in the pressure increase rate dP / dCA is suppressed.

  Here, with reference to FIG. 6, the combustion timing estimation control and the ignition timing control according to the present embodiment will be described. Each process from step S21 to step S25 in FIG. 6 is the same as step S1 to step S5 in FIG. 3 shown in the first embodiment. Therefore, in the following, only processing different from that of the first embodiment will be described.

  As shown in FIG. 6, the ECU 10 determines whether or not the combustion timing CA50 calculated in step S25 matches the target combustion timing CA50 (step S26). Whether the combustion timing CA50 matches the target combustion timing CA50 is determined in the same manner as in the first embodiment.

  If the ECU 10 determines that the combustion timing CA50 coincides with the target combustion timing CA50, the ECU 10 moves the process to step S28. On the other hand, when it is determined that the combustion timing CA50 does not coincide with the target combustion timing CA50, the ECU 10 corrects the combustion timing CA50 (step S27) and returns the process to step S25.

  As a correction of the combustion timing CA50, the ECU 10 increases or decreases the fuel injection amount, advances or retards the ignition timing, for example. Thereby, the combustion timing CA50 is corrected to the advance side or the retard side.

  In step S28, the ECU 10 calculates the pressure increase rate dP / dCA. Next, the ECU 10 determines whether or not the pressure increase rate dP / dCA calculated in step S28 is smaller than the target pressure increase rate (step S29). Here, the target pressure increase rate is a pressure increase rate that can suppress the combustion period from being shortened, and is experimentally obtained in advance and stored in the ROM of the ECU 10 as a map.

  When the ECU 10 determines that the pressure increase rate dP / dCA is smaller than the target pressure increase rate, the ECU 10 ends this process. On the other hand, when the ECU 10 determines that the pressure increase rate dP / dCA is not smaller than the target pressure increase rate, that is, equal to or higher than the target pressure increase rate, the ECU 10 performs in-cylinder pressure reduction control (step S30), and proceeds to step S28. Return processing.

  As in-cylinder pressure reduction control, for example, control is performed to retard the combustion timing CA50 or reduce the fuel injection amount. Thereby, the in-cylinder pressure is reduced.

  In addition, self-ignition in HCCI combustion and knocking in a spark ignition engine are the same phenomenon. Therefore, the combustion timing estimation method described in each of the above-described embodiments can be used for knocking control of a spark ignition engine. For example, in such knocking control, the presence or absence of knocking is estimated instead of the combustion timing. Further, the combustion timing estimation method can be used not only for knocking control but also for controlling preignition that occurs during supercharging, for example. In this case, the presence / absence of pre-ignition is estimated instead of the combustion timing.

  Although the embodiments of the present invention have been disclosed as described above, it is obvious that those skilled in the art can make changes without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 vehicle 2 engine (premixed compression self-ignition internal combustion engine)
5 EGR device 10 ECU
20 Spark plug 21 Cylinder 23 Injector 30 Supercharger 101 Airflow sensor 102 Intake air temperature sensor 103 Intake air pressure sensor 104 Intake air O ₂ sensor 105 In-cylinder pressure sensor 106 Exhaust air temperature sensor 107 Linear A / F sensor 180 Crank angle sensor 181 Water temperature sensor

Claims (7)

In a control device for a premixed compression self-ignition internal combustion engine that self-ignites and burns by compressing an air-fuel mixture in a cylinder,
At least when the in-cylinder pressure and the exhaust temperature and the in-cylinder pressure and the exhaust temperature at the time of opening the intake valve with respect to the in-cylinder pressure at 10 ° CA before compression top dead center, the equivalence ratio, and the in-cylinder mixture amount are detected. The ratio of the residual gas amount calculated using the gas equation of state based on the volume of the combustion chamber is the frequency factor of the Arrhenius equation, and the frequency factor and the in-cylinder temperature at 10 ° CA before compression top dead center are the Arrhenius equation. The premixed compression self-ignition internal combustion engine is used for estimating the time when 50% of the fuel injected in the cylinder in the premixed compression self-ignition internal combustion engine is consumed, and the premixed compression self-ignition internal combustion engine is set so that the estimated time becomes the target combustion timing. A control device for a premixed compression self-ignition internal combustion engine, characterized by controlling.   2. The preliminary index according to claim 1, wherein a predetermined index is assigned to each of the in-cylinder pressure, the equivalence ratio, and the ratio of the residual gas amount used as the frequency factor of the Arrhenius equation. A control device for a mixed compression self-ignition internal combustion engine. In a control device for a premixed compression self-ignition internal combustion engine that self-ignites and burns by compressing an air-fuel mixture in a cylinder,
The number of revolutions of the premixed compression self-ignition internal combustion engine, the end timing of fuel injected into the cylinder, the heat loss estimated value for estimating the heat loss due to the transfer of heat between the wall surface in the cylinder and the fuel, In-cylinder pressure at 10 ° CA before compression top dead center, equivalent ratio, and in-cylinder pressure and exhaust temperature when the intake valve is opened, and combustion when the in-cylinder pressure and exhaust temperature are detected The ratio of the amount of residual gas calculated using the equation of state of the gas based on the volume of the chamber is used as the frequency factor of the Arrhenius equation, and the frequency factor and the in-cylinder temperature at 10 ° CA before compression top dead center are expressed in the Arrhenius equation. The premixed compression self-ignition internal combustion engine is used to estimate when 50% of the fuel injected in the cylinder is consumed, and the premixed compression self-ignition internal combustion engine is controlled so that the estimated time becomes the target combustion timing. Premixed compression self-ignition type characterized by Control device for internal combustion engine.   For each of the rotational speed of the premixed compression auto-ignition internal combustion engine used as the Arrhenius type frequency factor, the injection end timing, the heat loss estimated value, the in-cylinder pressure, the equivalent ratio, and the ratio of the residual gas amount 4. The control device for a premixed compression self-ignition internal combustion engine according to claim 3, wherein a predetermined index is assigned. In a control device for a premixed compression self-ignition internal combustion engine that self-ignites and burns by compressing an air-fuel mixture in a cylinder,
At least when the in-cylinder pressure and the exhaust temperature and the in-cylinder pressure and the exhaust temperature at the time of opening the intake valve with respect to the in-cylinder pressure at 10 ° CA before compression top dead center, the equivalence ratio, and the in-cylinder mixture amount are detected. The ratio of the residual gas amount calculated using the gas equation of state based on the volume of the combustion chamber and the heat loss estimated value for estimating the heat loss due to heat transfer between the wall surface in the cylinder and the fuel are expressed by the Arrhenius equation. The time when 50% of the fuel injected in the cylinder in the premixed compression self-ignition internal combustion engine is consumed by using the Arrhenius equation using the frequency factor and the cylinder temperature at 10 ° CA before compression top dead center as the frequency factor. A control device for a premixed compression self-ignition internal combustion engine, wherein the premixed compression self-ignition internal combustion engine is controlled so that the estimated combustion timing is a target combustion timing.   The control device for a premixed compression self-ignition internal combustion engine according to any one of claims 3 to 5, wherein the estimated heat loss value is a deviation between an exhaust gas temperature and an intake air temperature.   After estimating 50% of the fuel injected in-cylinder in the premixed compression self-ignition internal combustion engine and controlling the premixed compression self-ignition internal combustion engine so that the estimated time becomes the target combustion timing The premixed compression self-ignition internal combustion engine is controlled to reduce the in-cylinder pressure if the rate of increase in the in-cylinder pressure is equal to or higher than the target pressure increase rate. The control device of the premixed compression self-ignition internal combustion engine described.