JP5936722B1 - Control device for internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine capable of avoiding a misfire region and switching a combustion mode as reliably and quickly as possible. A misfire region determining means for determining whether or not an exhaust gas recirculation amount control value set based on an operating state of an internal combustion engine is in a misfire region of the internal combustion engine, the misfire region determining means includes: When the exhaust gas recirculation amount control value is larger than the spark ignition upper limit exhaust gas recirculation amount estimated value and smaller than the premixed compression ignition lower limit exhaust gas recirculation amount estimated value, it is determined that the region is a misfire region. [Selection] Figure 1

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that controls exhaust gas recirculation at the time of switching control between spark ignition combustion mode control and premixed compression ignition combustion mode control in a direct injection internal combustion engine. is there.

  In recent years, there has been a strong demand for improvements in exhaust gas and fuel consumption of internal combustion engines (hereinafter referred to as “engines”) due to air pollution and fluctuations in petroleum circumstances. One way to improve the exhaust gas and fuel consumption of engines using gasoline is to use a mixture in the latter half of the compression stroke instead of conventional spark ignition (hereinafter referred to as “SI”). Combustion control by premixed compression ignition (hereinafter referred to as “HCCI”), which raises the temperature and pressure to a higher temperature and self-ignites the air-fuel mixture, has attracted attention.

  HCCI combustion can reduce fuel consumption because combustion with a leaner air-fuel mixture is possible compared to SI combustion, and NOx of exhaust gas can be reduced due to a lower combustion temperature than SI combustion. Misfire and knocking can occur if the temperature is not appropriate. Therefore, for example, exhaust gas recirculation (hereinafter referred to as “EGR”), for example, by causing the valve closing timing of the exhaust valve to be before the intake top dead center and minus opening the intake valve to be after the intake top dead center. There is a well-known control technique in which the temperature of the air-fuel mixture is increased to obtain good HCCI combustion.

  In addition, HCCI combustion can be performed in a relatively low engine speed and load range, but the region is narrower than the SI combustion range, so that the operation is outside the HCCI combustion range during HCCI combustion. When the state changes, the HCCI combustion is switched to the SI combustion in order to keep the combustion good, and conversely, when the operation state that becomes the HCCI combustion region at the time of SI combustion is reached, the fuel consumption and exhaust gas reduction are promptly performed. There is a known control technique in which the EGR is changed to switch to the HCCI combustion so that the HCCI combustion can be switched to the HCCI combustion.

  However, there is an operating state in which SI combustion and HCCI combustion cannot be continuously switched in response to a change in EGR. That is, for example, when the EGR is gradually increased in a steady operation state where the engine speed and the load are constant, in a certain EGR range, there is too much EGR for SI combustion, and an air-fuel mixture by EGR for HCCI combustion. Since the temperature rise is insufficient, there is an operating state in which combustion becomes unstable and misfires occur. Therefore, control in consideration of such an operating state is required.

  Thus, for example, in the technique disclosed in Patent Document 1, when switching from SI combustion to HCCI combustion in a low-rotation low-load region at start-up where the EGR range where combustion becomes unstable is large, EGR sets the combustion unstable region. When passing, it is determined that combustion switching is impossible, and SI combustion is performed even in the HCCI combustion enabled operation state, and combustion switching is prohibited.

JP 2004-11539 A

  As described above, during transient operation where the engine speed and load are high, HCCI combustion at high speed and high load is difficult due to knocking, so it is necessary to quickly switch from HCCI combustion to SI combustion. In a transient operation state where the rotational speed and load are low, it is desirable to quickly switch from SI combustion to HCCI combustion in order to improve fuel efficiency. Therefore, not only the conditions for switching from SI combustion to HCCI combustion at the time of starting described in Patent Document 1, but also in a transient operation state where there is a high possibility of switching the combustion mode, SI combustion and HCCI combustion are both difficult and combustion becomes unstable. It is necessary to set the control in consideration of the range. In addition, it is desirable to perform the combustion mode switching control as much as possible instead of prohibiting the combustion mode switching control because it leads to improvement of exhaust gas, fuel consumption, and drivability.

  The present invention has been made in view of the problems related to switching of the combustion mode in the transient operation state as described above, and can avoid the misfire region and can switch the combustion mode as reliably and quickly as possible. An object of the present invention is to provide a control device.

An internal combustion engine control apparatus according to the present invention includes:
A spark ignition combustion mode in which a mixture of air and fuel in a cylinder of the internal combustion engine is burned by an ignition plug, and an exhaust valve of the internal combustion engine is controlled in the cylinder by controlling the opening and closing timings of the exhaust valve and the intake valve of the internal combustion engine. the mixture was warmed to recirculate, and the internal combustion engine HCCI combustion mode for burning by compression self-ignition in the latter half of the compression stroke of, and is switched based on the operating state of the internal combustion engine combustion An engine control device,
Spark ignition upper limit exhaust gas recirculation amount estimation means for calculating an estimated value of spark ignition upper limit exhaust gas recirculation amount operable in the spark ignition combustion mode based on the operating state of the internal combustion engine;
Premixed compression ignition lower limit exhaust gas recirculation amount estimating means for calculating a premixed compression ignition lower limit exhaust gas recirculation amount estimated value operable in the premixed compression ignition combustion mode based on the operating state of the internal combustion engine;
A misfire region determination means for determining whether or not an exhaust gas recirculation amount control value set based on an operating state of the internal combustion engine is in a misfire region of the internal combustion engine;
When it is determined by the misfire region determination means that the misfire region is present, the premixed compression ignition lower limit exhaust gas recirculation that can set the exhaust gas recirculation amount control value to the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. A quantity setting means;
With
The misfire region determination means, when the exhaust gas recirculation amount control value is larger than the spark ignition upper limit exhaust gas recirculation amount estimated value and smaller than the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. , Configured to determine that the misfire region is,
When it is determined that the misfire region is determined by the misfire region determining means, the spark ignition combustion mode and the premixed compression ignition combustion mode can be switched.
It is characterized by that.

According to the control apparatus for an internal combustion engine according to the present invention, the combustion mode can be switched while avoiding the misfire region, and exhaust gas, fuel consumption, and drivability can be improved.

1 is a block diagram showing an internal combustion engine control apparatus according to Embodiment 1 of the present invention. FIG. 1 is a configuration diagram illustrating an entire system including a control device for an internal combustion engine according to Embodiment 1 of the present invention. FIG. It is a flowchart which shows operation | movement of the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the combustion area characteristic according to the driving | running state and EGR, and the misfire generation | occurrence | production path | route at the time of a transient driving | running state. 6 is a second map showing the characteristics of the premixed compression ignition lower limit exhaust gas recirculation amount estimated value obtained from the operating state value in the control apparatus for an internal combustion engine according to the first embodiment of the present invention. FIG. 9 is a third map showing the characteristics of the operating state value obtained from the engine speed and boost pressure in the control apparatus for an internal combustion engine according to Embodiment 1 of the present invention. FIG. 9 is a fourth map showing the characteristic of the spark ignition upper limit exhaust gas recirculation amount estimated value obtained from the operating state value in the control apparatus for an internal combustion engine according to Embodiment 1 of the present invention; FIG. 3 is a timing chart showing the behavior of exhaust gas recirculation control when the combustion switching mode is established in the control apparatus for an internal combustion engine according to Embodiment 1 of the present invention. It is explanatory drawing which shows the difference in the behavior of exhaust gas recirculation amount control in the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention, and the conventional apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts will be described with the same reference numerals.
Embodiment 1 FIG.

  In the following description, when the combustion switching condition is established and the EGR amount control value is in the misfire region, the HCCI lower limit EGR amount is set, or the EGR amount for continuing the current combustion mode is set. A control apparatus for an internal combustion engine according to a first embodiment of the invention will be described. FIG. 1 is a block diagram showing an internal combustion engine control apparatus according to Embodiment 1 of the present invention, and each means shown in FIG. 1 is stored in an engine control electronic control unit described later. FIG. 2 is a configuration diagram showing the entire system including the control device for the internal combustion engine according to the first embodiment of the present invention. In general, an engine is provided with a plurality of cylinders, but only one of them is shown in FIG.

  In FIG. 2, the engine 1 is provided with a cylindrical cylinder 2. A piston 3 that can reciprocate in the axial direction of the cylinder 2 is provided. The cylinder 2 and the piston 3 form a combustion chamber 4 in which a mixture of fuel and air burns. In addition, a crankshaft 5 that converts the reciprocating motion of the piston 3 into a rotational motion is provided, and a crank angle sensor 6 that detects a crank angle that is a rotational angle of the crankshaft 5 is provided. Further, the cylinder 2 is provided with a water temperature sensor 7 that outputs a voltage corresponding to the temperature of cooling water (not shown) for cooling the engine 1.

  An intake manifold 8 that sucks air into the cylinder 2 (hereinafter referred to as “in-cylinder”), and an exhaust manifold that discharges exhaust gas generated by combustion of a mixture of air and fuel inside the combustion chamber 4. 9 is connected to the cylinder 2. The cylinder 2 has two intake valves 10 that open and close between the combustion chamber 4 and the intake manifold 8, and two exhaust valves 11 that open and close between the combustion chamber 4 and the exhaust manifold 9 (in FIG. 2). Only one is shown).

  In order to control the intake valve 10 and the exhaust valve 11 with an appropriate valve opening timing and an appropriate lift amount, cams (not shown) that rotate and push down the respective valves are provided above the intake valve 10 and the exhaust valve 11. The intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 are installed. By the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13, a negative valve overlap in which the exhaust valve 11 is closed before the intake top dead center and the intake valve 10 is opened after the intake top dead center ( Negative Valve Overlap (hereinafter referred to as “NVO”) can be controlled to obtain a desired internal EGR amount.

  A fuel injection valve 14 that directly injects fuel into the cylinder at an appropriate timing is attached to the top of the cylinder 2. Further, an ignition plug 15 that sparks and ignites the air-fuel mixture formed in the combustion chamber 4 and an ignition coil 16 that supplies high voltage energy to the ignition plug 15 are attached to the top of the cylinder 2.

  A surge tank 17 that temporarily stores air sucked into the combustion chamber 4 is connected to the upstream side of the intake manifold 8, and a throttle valve 18 is connected to the upstream side of the surge tank 17. The throttle valve 18 is provided with a throttle valve opening sensor (not shown) that outputs a voltage corresponding to the valve opening. Further, a boost pressure sensor 19 that outputs a voltage corresponding to the boost pressure and an intake air temperature sensor 20 that outputs a voltage corresponding to the temperature of the intake air are provided on the downstream side of the throttle valve 18.

  The exhaust manifold 9 is provided with an exhaust temperature sensor 21 that outputs a voltage corresponding to the temperature of the exhaust gas that passes through the exhaust manifold 9. A catalyst device (not shown) for removing harmful substances in the exhaust gas is connected to the downstream side of the exhaust manifold 9, and a tail pipe (not shown) for exhausting the exhaust gas to the outside is connected to the downstream side of the catalyst device. Connected).

  An electronic control unit for engine control (hereinafter referred to as ECU) 22 includes a CPU that performs arithmetic processing, a ROM that stores program data and fixed value data, a RAM that can be sequentially rewritten by updating stored data, and ECU 22 A microcomputer (not shown) having a backup RAM for holding stored data even when the power is turned off, a drive circuit (not shown) for driving an actuator, and an I / O for inputting and outputting various signals And an O interface (not shown).

  1 and 2, the memory of the ECU 22 includes an operation state prediction unit 23, a spark ignition upper limit exhaust gas recirculation amount estimation unit 24, a premixed compression ignition lower limit exhaust gas recirculation amount estimation unit 25, and a premixed compression ignition lower limit exhaust gas recirculation. Circulation amount correction means 26, misfire region determination means 27, premixed compression ignition lower limit exhaust gas recirculation amount setting means 28, and combustion mode switching standby means 29 are stored as software. Further, the ECU 22 receives the voltage output values from the intake air temperature sensor 20, the exhaust temperature sensor 21, the water temperature sensor 7, the boost pressure sensor 19, and the throttle valve opening sensor after A / D conversion, and these A / Ds are input. The converted output values are used for calculation in the above-described means as intake air temperature Ta, exhaust temperature Tex, water temperature Tw, boost pressure Pb, and throttle opening degree Th. Further, the ECU 22 receives an interrupt signal from the crank angle sensor 6 and calculates the engine speed Ne from the timer built in the ECU 22 and the signal from the crank angle sensor 6.

The operating state predicting means 23 uses the current engine speed Ne and boost pressure Pb, and the engine speed Neo and boost pressure Pb in the combustion cycle immediately before the present to determine the engine speed in the combustion cycle immediately after the present. Nen and boost pressure Pbn are predicted. A specific calculation method will be described in the flow of control using FIG. 3 described later.

The spark ignition upper limit exhaust gas recirculation amount estimating means 24 is the maximum EGR amount that can perform SI combustion according to the operating state value So calculated from the engine speed Nen and the boost pressure Pbn in the combustion cycle immediately after the present. A certain SI upper limit EGR amount estimated value Es is calculated. A specific calculation method will be described in the flow of control using FIG. 3 described later.

The premixed compression ignition lower limit exhaust gas recirculation amount estimating means 25 is the minimum EGR that can perform HCCI combustion according to the operating state value So calculated from the engine speed Nen and the boost pressure Pbn in the combustion cycle immediately after the present. The HCCI lower limit EGR amount estimated value Eh, which is a quantity, is calculated. A specific calculation method will be described in the flow of control using FIG. 3 described later.

  The premixed compression ignition lower limit exhaust gas recirculation correction means 26 adjusts the HCCI lower limit EGR so that the minimum EGR amount at which HCCI combustion is possible decreases with the intake air temperature Ta, the exhaust temperature Tex, and the water temperature Tw. The quantity estimated value Eh is corrected. A specific calculation method will be described in the flow of control using FIG. 3 described later.

The misfire region determination means 27 is calculated according to the engine speed Nen and the boost pressure Pbn in the combustion cycle immediately after the present, and is calculated in consideration of an intake air delay, an exhaust gas temperature delay, etc. during transient operation. It is determined whether or not the control value Ei is larger than the SI upper limit EGR amount estimated value Es and smaller than the HCCI lower limit EGR amount estimated value Eh. A specific calculation method will be described in the flow of control using FIG. 3 described later.

  The premixed compression ignition lower limit exhaust gas recirculation amount setting means 28 sets the final EGR amount control value Ef as the HCCI lower limit EGR amount estimated value Eh in the combustion cycle immediately after the predicted current time. A specific calculation method will be described in the flow of control using FIG. 3 described later.

  The combustion mode switching standby means 29 calculates the absolute value Ed of the difference between the EGR amount control value Ei and the HCCI lower limit EGR amount estimated value Eh from the change speed of the actuator that controls the preset EGR amount and the engine speed Nen. If the EGR change limit amount El is greater, the final EGR amount control value Ef is set to the HCCI lower limit EGR amount estimated value Eh for the current HCCI combustion mode, and to the SI upper limit EGR amount estimation for the current SI combustion mode. Set to the value Es. A specific calculation method will be described in the flow of control using FIG. 3 described later.

  Next, in the control apparatus for an internal combustion engine configured as described above, when the combustion switching mode condition is established, the EGR amount control value is compared with the estimated SI upper limit EGR amount estimated value and HCCI lower limit EGR amount estimated value. The operation of setting the EGR amount control value as the HCCI lower limit EGR amount estimated value when it is larger than the SI upper limit EGR amount estimated value and smaller than the HCCI lower limit EGR amount estimated value will be described.

  FIG. 3 is a flowchart showing the operation of the control device for the internal combustion engine according to the first embodiment of the present invention. First, each operation will be described with reference to the flowchart of FIG. This operation is executed as a subroutine in an interrupt routine executed by the ECU 22 by interrupting every predetermined crank angle. In the first embodiment, it is executed as a subroutine in an interrupt routine executed by interrupting every predetermined crank angle. However, it may be executed as a subroutine in a main routine having a predetermined time period.

  In FIG. 3, first, in step S101, it is determined whether or not the combustion switching mode is being performed. For example, combustion is determined by determining a combustion mode with reference to a combustion mode control map set in advance based on the engine speed Ne and boost pressure Pb, and setting a combustion switching mode flag when different from the current combustion mode. The condition for mode switching is satisfied.

  If it is determined in step S101 that the combustion switching mode is not established (N), an initialization process is executed in step S102. In the initialization process in step S102, the current engine speed Ne and boost pressure Pb are input to the engine speed Neo and boost pressure Pbo, and “0” is input to the combustion switching standby flag Fhld as an initial value.

Following step S102, the final EGR amount control value Ef is input to the current EGR amount control value Ei in step S103, and the subroutine is terminated. After the subroutine ends, the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 are controlled so that the NVO corresponding to the final EGR amount control value Ef is obtained. Here, when step S103 is performed after step S102,
As the final EGR amount control value Ef, the EGR amount control value Ei calculated outside this subroutine is input to the final EGR amount control value Ef.

If it is determined in step S101 that the combustion switching mode is established (Y), the engine speed Nen and boost pressure Pbn in the next combustion cycle are determined in step S104, the current engine speed Ne and boost pressure Pb, Prediction is performed using the following equation (1) and equation (2) using the engine speed Neo and boost pressure Pbo of the previous cycle. Further, after the calculation of the formulas (1) and (2), the engine speed Neo and the boost pressure Pbo are updated by the formulas (3) and (4) to be used when the next step S104 is performed.

Nen = (Ne−Neo) + Ne (1)
Pbn = (Pb−Pbo) + Pb (2)
Neo ← Ne Formula (3)
Pbo ← Pb ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Formula (4)

This step S104 corresponds to the driving state prediction means 23.

  The operating state predicting means 23 is not limited to the above, and for example, the engine in the next combustion cycle using a map set in advance according to the change in the throttle opening Th that can quickly detect the change in the operating state. A configuration in which the rotational speed Nen and the boost pressure Pbn are obtained may be employed.

Next, in step S105, an EGR amount control value Ei based on the engine speed Nen and the boost pressure Pbn in the combustion cycle immediately after the current time calculated in step S104 is calculated. The EGR amount control value Ei is calculated outside this subroutine, and is calculated based on the following equation (5), for example, using the same equation as the equation for the EGR amount control value Ei in the conventional control.

Ei = map1 (Nen, Pbn) × Ka (5)

Here, the first map map1 is an optimal EGR amount control value set in advance according to the engine speed and boost pressure, and Ka takes into account the control delay and the water temperature during transient operation. Correction coefficient.

  Here, the range of the EGR amount that misfires due to unstable combustion will be described. FIG. 4 is an explanatory diagram showing the combustion region characteristics according to the operating state and the EGR amount, and the misfire occurrence path in the transient operating state, where the horizontal axis is the operating state (engine speed and load), and the vertical axis is the EGR amount. Is shown. As shown in FIG. 4, the range of the EGR amount that causes misfire due to unstable combustion is large when the engine operating state (hereinafter simply referred to as “operating state”) due to the engine speed or the load is low. , The higher the driving state, the narrower. Furthermore, there is an operating state in which there is no range of EGR amount to misfire and SI combustion and HCCI combustion are continuously switched.

  For example, at the time of transient operation where the operation state becomes low, when switching from the SI combustion region at point a in FIG. 4 to the HCCI combustion region at point b, the EGR amount indicated by a white circle in the middle is in the misfire region. A misfire occurs at point c, and it is impossible to reach point b, or drivability deteriorates. In such a case, the misfire region is avoided by controlling at point d which is SI combustion upper limit EGR amount capable of SI combustion, or point e which is HCCI combustion lower limit EGR amount capable of HCCI combustion instead of point c. be able to.

  However, when controlling to the SI combustion upper limit EGR amount at the point d, it is necessary to switch to the HCCI combustion region over a wider misfire region in order to reach the point b. On the other hand, when it is controlled to the HCCI combustion lower limit EGR amount at point e, it is possible to cross over a narrow misfire region and switch to HCCI combustion at point e. It is not necessary to consider the misfire region in order to reach point b after point e. Therefore, it can be seen that by passing the e point instead of the c point, it is possible to quickly switch from SI combustion to HCCI combustion without deteriorating exhaust gas and drivability due to misfire, and to improve fuel efficiency.

  On the other hand, when switching from the b-point HCCI combustion region to the a-point SI combustion region during a transient operation where the operation state becomes high, misfire occurs at the point c as described above. In order to avoid this, it is necessary to pass the point d or the point e. However, reaching the point e over the point d crosses a narrower misfire region. Therefore, by passing the e point instead of the c point, the exhaust gas and the drivability are not deteriorated due to misfire, and the HCCI combustion period is long, so the fuel efficiency is improved. Further, since the point e is the HCCI combustion lower limit EGR amount capable of HCCI combustion, the possibility of occurrence of knocking is low.

From the above, in both cases where the combustion mode is switched from SI combustion to HCCI combustion or from HCCI combustion to SI combustion in the transient operation state, the HCCI combustion capable of HCCI combustion is achieved when the EGR amount is in the misfire region. It has been found that by controlling to the combustion lower limit EGR amount, a misfire region can be avoided and exhaust gas, fuel consumption, and drivability can be improved.

  Here, as a method of avoiding misfire by a method other than controlling the EGR amount, fuel injection amount control or air-fuel mixture heating control is conceivable. However, since the fuel injection amount is increased, the fuel consumption deteriorates and the air-fuel mixture other than EGR is controlled. Temperature heating requires a very large amount of heat input for control, such as a heater, and as a result, fuel consumption deteriorates. Therefore, when the EGR amount is in the misfire region, a method for controlling the EGR amount is an effective means.

Returning to FIG. 3, based on the consideration in FIG. 4 described above, in step S <b> 106, the HCCI lower limit EGR amount estimated value Eh, which is the minimum EGR amount capable of HCCI combustion, is calculated based on the following equation (6) using the operating state value So. The calculation is performed with reference to the second map map2 set in advance. Here, the second map map2 for calculating the HCCI lower limit EGR amount estimated value Eh is set in advance extracted from the characteristics shown in FIG. 4, and is shown in FIG. That is, FIG. 5 is a second map showing the characteristics of the HCCI lower limit EGR amount estimated value obtained from the operating state value in the control apparatus for an internal combustion engine according to Embodiment 1 of the present invention, and the horizontal axis represents the operating state. The value So and the vertical axis indicate the HCCI lower limit EGR amount estimated value Eh.

Eh = map2 (So) ..... Formula (6)

The operating state value So is calculated based on the following equation (7). Here, a third map map3 for calculating the driving state value So is shown in FIG. That is, FIG. 6 is a third map showing the characteristics of the operating state value obtained from the engine speed and boost pressure in the control apparatus for an internal combustion engine according to the first embodiment of the present invention. The number and the vertical axis indicate the boost pressure. As shown in FIG. 6, when the engine speed or boost pressure increases, the operating state value So is set in advance.

So = map3 (Nen, Pbn) (7)

Step S106 corresponds to the premixed compression ignition lower limit exhaust gas recirculation amount estimating means 25.

In FIG. 3, in step S107, the HCCI lower limit EGR amount estimated value Eh obtained in step S106 is corrected as shown in the following equation (8) based on the intake air temperature Ta, the exhaust air temperature Tex, and the water temperature Tw. HCCI lower limit EGR amount estimated value Eh1.

Eh ← Eh × (Ta + Tex + Tw) × Kb (8)

Here, the correction coefficient Kb is determined if the intake air temperature Ta, the exhaust temperature Tex, or the water temperature Tw is higher than the reference, based on the temperature condition when the second map map2 used in the above equation (6) is created. , [(Ta + Tex + Tw) × Kb] is set in advance so as to be equal to or less than “1”. The behavior that the final HCCI lower limit EGR amount estimated value Eh1 becomes smaller as the intake air temperature Ta, the exhaust air temperature Tex, or the water temperature Tw becomes higher can be calculated by the equation (8). This step S107 corresponds to the premixed compression ignition lower limit exhaust gas recirculation correction means 26.

Next, in step S108, a fourth map map4 in which the SI upper limit EGR amount estimated value Es, which is the maximum EGR amount capable of SI combustion, is preset based on the following equation (9) with the operation state value So. Operate with reference to. Here, the fourth map map4 for calculating the SI ceiling EGR amount estimation value Es has been set in advance by extracting the characteristics of FIG. 4, shown in Figure 7. That is, FIG. 7 is a fourth map map4 showing the characteristic of the SI upper limit EGR amount estimated value obtained from the operating state value in the control apparatus for an internal combustion engine according to the first embodiment of the present invention, and the horizontal axis is the operating state. The value So and the vertical axis indicate the SI upper limit EGR estimated value Es.

Es = map4 (So) (9)

This step S108 corresponds to the spark ignition upper limit exhaust gas recirculation amount estimating means 24.

  In step S109, whether or not the EGR amount control value Ei is less than the HCCI lower limit EGR amount estimated value Eh and greater than the SI upper limit EGR amount estimated value Es, or Fhld which is a combustion switching standby flag described later. It is determined whether “1” is input. This step S109 corresponds to the misfire region determination means 27.

  If it is determined in step S109 that [Eh> Ei> Es] or [Fld = 1] is not satisfied (N), the EGR amount does not become a misfire region, so the EGR amount in the conventional control is set. Therefore, the process proceeds to step S103, the EGR amount control value Ei is input as the final EGR amount control value Ef, and the subroutine is terminated. After the subroutine ends, the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 are controlled so that the NVO corresponding to the final EGR amount control value Ef is obtained.

If it is determined in step S109 that [Eh>Ei> Es] or [Fld = 1] is satisfied (Y), the current timing calculated by the following equation (10) in step S110. EGR change amount Ed, which is the difference between the final EGR amount control value Ef and the HCCI lower limit EGR amount estimated value Eh, is the limit at which the actuator controlling the EGR amount can change during one combustion cycle. Determine whether the value is larger. In the EGR amount change limit value El, the maximum change width per combustion of the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 as actuators that control the EGR amount is set in advance.

Ed = abs (Ef−Eh) (10)

  The EGR amount change limit value El is not limited to a preset value, and may be a value obtained by correcting the change limit amount of the actuator with, for example, the engine speed or each temperature information.

  If it is determined in step S110 that [Ed> El] is not satisfied (N), “0” is input to a combustion switching standby flag Fhld described later in step S111, and then the final EGR is determined in step S112. The HCCI lower limit EGR amount estimated value Eh is input to the amount control value Ef, and the subroutine is terminated. After the subroutine ends, the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 are controlled so that the NVO corresponding to the final EGR amount control value Ef is obtained. This step S112 corresponds to the premixed compression ignition lower limit exhaust gas recirculation amount setting means 28.

If it is determined in step S110 that [Ed> El] is satisfied (Y), it is stored in the combustion switching standby flag Fhld in step S113 in order to store that the combustion switching standby mode is currently set. After inputting “1”, it is determined in step S114 whether the current combustion mode is the SI combustion mode. If it is determined in step S114 that the current mode is not the SI combustion mode, that is, the HCCI combustion mode (N), in step S115, the HCCI combustion standby EGR amount control value Ehh is expressed by the following equation (11). ), The HCCI lower limit EGR amount estimated value Eh, the difference between the current final EGR amount control value Ef and the EGR amount change limit value El, and the maximum value of these two values are calculated.

Ehh = max (Eh, Ef−El) (11)

  As a result, within the range of EGR amount in which HCCI combustion is possible, the current EGR amount control value Ef is set to a value that becomes an EGR amount that approaches SI combustion as much as possible, and combustion mode switching is on standby. The EGR amount is such that the combustion mode can be switched more easily after the combustion cycle.

  After step S115, at step S116, the HCCI combustion standby EGR amount control value Ehh is input as the final EGR amount control value Ef, and the subroutine is terminated. After the subroutine ends, the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 are controlled so that the NVO corresponding to the final EGR amount control value Ef is obtained.

If it is determined in step S114 that the current combustion mode is SI combustion mode (Y), in step S117, the SI combustion standby EGR amount control value Ehs is calculated as follows: It is calculated by adding Es, the current final EGR amount control value Ef, and the EGR amount change limit value El, and the minimum value of these two values.

Ehs = min (Es, Ef + El) (12)

As a result, within the range of EGR amount in which SI combustion is possible, the current EGR amount control value Ef is set to a value that becomes an EGR amount that approaches HCCI combustion as much as possible, and combustion mode switching is on standby. The EGR amount is such that the combustion mode can be switched more easily after the combustion cycle.

  After step S117, the SI combustion standby EGR amount control value Ehs is input as the final EGR amount control value Ef in step S118, and the subroutine is terminated. After the subroutine ends, the intake variable valve mechanism 12 and the exhaust variable valve mechanism 13 are controlled so that the NVO corresponding to the final EGR amount control value Ef is obtained.

  Step S110, step S111, and step S113 to step S118 correspond to the combustion mode switching standby means 29.

  As described above, the control apparatus for an internal combustion engine according to Embodiment 1 of the present invention provides the estimated EGR amount control value, the estimated SI upper limit EGR amount, and the estimated HCCI lower limit EGR amount when the combustion switching mode condition is satisfied. In comparison, when the EGR amount control value is larger than the SI upper limit EGR amount estimated value and smaller than the HCCI lower limit EGR amount estimated value, the EGR amount control value is set as the HCCI lower limit EGR amount estimated value.

  Next, the operation of the control apparatus for an internal combustion engine according to the first embodiment of the present invention will be described using a timing chart. FIG. 8 is a timing chart showing the behavior of the EGR amount control when the combustion switching mode is established in the control apparatus for an internal combustion engine according to the first embodiment of the present invention. A case where the engine is lowered and is in an engine transient operation state is shown as an example. FIG. 8 shows various behaviors linearly for simplification. In FIG. 8, the horizontal axis represents time, and the vertical axis represents the combustion switching mode flag, the operation state value (prediction) So, the conventional EGR amount control value Ei, the EGR change amount Ed, the combustion switching standby flag Fhld, and the final EGR in order from the top. A quantity control value Ef is shown.

  In FIG. 8, the operation state regarding the combustion cycle immediately after the present is predicted, and the EGR amount control value in the predicted operation state is calculated. Therefore, since the period from the setting of the EGR amount control value to the actuator control is longer than the case where the actuator is controlled by calculating the EGR amount control value in the operation state of the current combustion cycle, the change range of the EGR amount is large or The actuator is controlled to the EGR amount control value that is set reliably without being affected by the response delay of the actuator.

  In FIG. 8, first, before the timing A, HCCI combustion is performed, and the combustion switching mode is not established because the operating state value (predicted) So obtained from the engine speed and the boost pressure is constant. Therefore, the final EGR amount control value Ef is set to the same value as the conventional EGR amount control value Ei not subjected to the processing according to the first embodiment of the present invention, and the EGR amount is controlled by this final EGR amount control value Ef. The

  Between timing A and timing C, the operating state value (predicted) So increases and the engine is in a transient operating state. Therefore, immediately after timing A, it is determined that the engine is in the transient operation state, the combustion switching mode is established so as to switch from HCCI combustion to SI combustion, and the combustion switching mode flag is turned on. At timing B, it is determined that the conventional EGR amount control value Ei is within the misfire region, but in the first embodiment of the present invention, the final EGR amount control value Ef is set to the HCCI lower limit EGR amount estimated value Eh. The amount of EGR is controlled and misfire is avoided. At the timing B1 immediately after the timing B, the EGR amount control is not performed in the conventional EGR amount control but the SI combustion mode EGR is performed, so that the combustion switching is completed and the conditions for the combustion switching mode are not satisfied, and the combustion switching mode flag Is turned off. Thereby, EGR which becomes a misfire region can be avoided, and switching from HCCI combustion to SI combustion can be performed without deteriorating combustion.

  Between timing D and timing F, the operating state value (predicted) So decreases and the engine is in a transient operating state. Immediately after timing D, the engine is determined to be in a transient operating state, and the combustion switching mode flag is turned on. . Thereby, the combustion switching mode is established so as to switch from SI combustion to HCCI combustion. Since there was a high operation state at timing C, the temperature such as exhaust temperature is higher than that in the steady operation state after timing C, and the HCCI lower limit EGR amount estimated value Eh is corrected to be slightly lower, but the timing is In E, it is determined that the conventional EGR amount control value Ei is within the misfire region.

  However, in Embodiment 1 of the present invention, since the EGR change amount Ed exceeds the EGR amount change limit value El at the timing E, the combustion switching standby flag Fhld is set to ON, and the final EGR amount control value Ef is set to SI. The EGR amount is controlled to be set to the upper limit EGR amount estimated value Es and to perform SI combustion. After timing E, the combustion switching standby state is entered, but until the timing F is reached, the EGR change amount Ed exceeds the EGR amount change limit value El, and the combustion cannot be switched without deteriorating the combustion. The amount control value Ef is set to the SI upper limit EGR amount estimated value Es, and the EGR is controlled so that SI combustion is performed. Thereby, it is possible to accurately determine the misfire region and reliably maintain good combustion.

  Between timing F and timing H, the operating state value (predicted) So increases and the engine is in a transient operating state. In this engine transient operation state, normal combustion switching does not occur, but since combustion switching is waited after timing E, the conditions for combustion switching mode are also satisfied after timing F. After the timing E, the EGR change amount Ed exceeds the EGR amount change limit value El, but immediately before the timing G, the EGR change amount Ed becomes lower than the EGR amount change limit value El. Therefore, the combustion switching standby is canceled at timing G, the final EGR amount control value Ef is set to the HCCI lower limit EGR amount estimated value Eh, and the EGR amount is controlled. Thereby, EGR which becomes a misfire region can be avoided, and switching from SI combustion to HCCI combustion can be performed without deteriorating combustion.

  Here, the difference between the conventional control and the EGR amount control by the control of the present invention in the change of the operation state shown in FIG. 8 will be described. FIG. 9 is an explanatory diagram showing the difference in behavior of EGR amount control between the control device for an internal combustion engine according to Embodiment 1 of the present invention and the conventional device, and from timing A to timing C and timing D in FIG. 9A, 9B, and 9C show the behavior of the EGR amount control that accompanies the change in the operation state from the timing F to the timing F and from the timing F to the timing H, respectively. In addition, it has shown that each combustion cycle shown in FIG. 9 is controlled by the value of the EGR amount of the white triangle mark and black circle mark in a figure.

  The EGR amount between timing A and timing C shown in (a) of FIG. 9 is controlled by the EGR amount control value in the misfire region at timing B in the conventional control, and misfire or combustion fluctuation occurs in this combustion cycle. Will occur. Here, by setting the EGR amount control value to the value of the HCCI combustion lower limit EGR amount as in the control by the control device for the internal combustion engine according to the first embodiment of the present invention, the combustion at the timing B causes the HCCI combustion and misfires. In the next cycle, the EGR amount control value for SI combustion is controlled so as to straddle the misfire region, thereby avoiding misfire during combustion switching.

  The EGR between the timing D and the timing F shown in (b) of FIG. 9 is controlled by the EGR in the misfire region at the timing E in the conventional control, and misfire or combustion fluctuation occurs in this combustion cycle. . Here, in the control by the control device for the internal combustion engine according to the first embodiment of the present invention, an attempt is made to control with the value of the HCCI combustion lower limit EGR amount, but the HCCI combustion is calculated from the EGR amount at the combustion cycle immediately before the timing E. It is determined that the amount of change to the lower limit EGR amount exceeds the amount that the actuator controlling the EGR amount can change during one combustion cycle, and at timing E, the value cannot be controlled to the value of the HCCI combustion lower limit EGR amount. By controlling by the value of the SI combustion upper limit EGR amount so as to wait for the SI combustion, the combustion switching is made to wait in order to avoid misfire during the combustion switching.

  In the conventional control between the timing F and the timing H shown in (c) of FIG. 9, the HCCI combustion is continued to control the EGR amount. Here, the timing from the timing D shown in (b) of FIG. If combustion switching to HCCI combustion is successful when the operating state of F is changed, the conventional control of FIG. 9C is performed, but misfire or combustion fluctuation occurs at timing E of FIG. 9B. Therefore, at timing F in FIG. 9C, HCCI combustion has not been reached or combustion has deteriorated at timing E in FIG. 9B at timing F in FIG. 9C. HCCI combustion.

  For this reason, in the conventional control, the EGR amount is changed from the EGR having a problem in combustion to the EGR amount at the timing H by the combustion switching control. Here, in the control by the control device for the internal combustion engine according to the first embodiment of the present invention, the EGR amount for performing SI combustion is controlled at the timing F in FIG. 9C, but from the timing F to the timing H. While the operating state changes, it is possible to control to the value of the HCCI combustion lower limit EGR amount at the timing G, and it is determined that there is no need to wait for the combustion switching, and the combustion switching is performed by switching to the HCCI combustion. Prioritizing maintaining good combustion during standby was prioritized, but misfire at the time of combustion switching is reliably avoided by controlling so as to quickly cross the misfire region if combustion switching is possible.

As described above, according to the control apparatus for an internal combustion engine according to the first embodiment of the present invention, the exhaust gas recirculation amount control value set according to the operating state is based on the spark ignition upper limit exhaust gas recirculation amount estimated value. If the exhaust gas recirculation amount is larger and smaller than the premixed compression ignition lower limit exhaust gas recirculation estimated value, and it is determined whether it is in the misfire region, the exhaust gas By setting the circulation amount control value to the premixed compression ignition lower limit exhaust gas recirculation amount estimated value, the combustion mode can be switched while avoiding the misfire region, and exhaust gas, fuel consumption, and drivability can be improved.

Furthermore, according to the control apparatus for an internal combustion engine according to the first embodiment of the present invention, at least one of the temperature information of the water temperature, the intake air temperature, the exhaust gas temperature, the oil temperature, the in-cylinder wall surface temperature, and the combustion temperature of the internal combustion engine. By correcting the lower limit of the exhaust gas recirculation amount that can be operated in the premixed compression ignition combustion mode using two types of information, it is possible to determine the misfire region more accurately, and more reliably, the exhaust gas, fuel consumption, and driver it is possible to improve the drivability.

Further, according to the control apparatus for an internal combustion engine according to the first embodiment of the present invention, the exhaust gas reactivation set in accordance with the operation state is set at least for the operation state of the next combustion cycle with respect to the combustion cycle ahead of the present. When it is determined whether the circulation amount control value is larger than the spark ignition upper limit exhaust gas recirculation amount estimated value and smaller than the premixed compression ignition lower limit exhaust gas recirculation amount estimated value and is in the misfire region, premixing is performed. By setting the exhaust gas recirculation amount control value to the premixed compression ignition lower limit exhaust gas recirculation amount estimation value so as to burn at the exhaust gas recirculation amount at the compression ignition combustion lower limit, the present invention is significantly more effective than the conventional EGR control. The EGR can be changed, and the influence of the response delay of the actuator can be reduced, and the exhaust gas, fuel consumption, and drivability can be improved.

Further, according to the control apparatus for an internal combustion engine according to the first embodiment of the present invention, the operating state is determined to be the misfire region, and the current exhaust gas recirculation amount is changed to the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. When there is no means for avoiding the misfire region by waiting for switching of the combustion mode when the amount to be exceeded exceeds the change limit amount during the combustion of one cycle of the actuator that introduces exhaust gas recirculation into the cylinder Priority is given to reliably maintaining good combustion, and drivability can be improved.

The control apparatus for an internal combustion engine according to the first embodiment of the present invention described above embodies the following invention.
(1) A spark ignition combustion mode in which a mixture of air and fuel in a cylinder of the internal combustion engine is burned by an ignition plug, and an open / close timing of an exhaust valve and an intake valve of the internal combustion engine are controlled to control the internal combustion engine in the cylinder. the mixture exhaust was recirculated warmed engine, said internal combustion engine HCCI combustion mode for burning by compression self-ignition in the latter half of the compression stroke of, switched based on the operating state of the internal combustion engine A control device for an internal combustion engine,
Spark ignition upper limit exhaust gas recirculation amount estimation means for calculating an estimated value of spark ignition upper limit exhaust gas recirculation amount operable in the spark ignition combustion mode based on the operating state of the internal combustion engine;
Premixed compression ignition lower limit exhaust gas recirculation amount estimating means for calculating a premixed compression ignition lower limit exhaust gas recirculation amount estimated value operable in the premixed compression ignition combustion mode based on the operating state of the internal combustion engine;
A misfire region determination means for determining whether or not an exhaust gas recirculation amount control value set based on an operating state of the internal combustion engine is in a misfire region of the internal combustion engine;
When it is determined by the misfire region determination means that the misfire region is present, the premixed compression ignition lower limit exhaust gas recirculation that can set the exhaust gas recirculation amount control value to the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. A quantity setting means;
With
The misfire region determination means, when the exhaust gas recirculation amount control value is larger than the spark ignition upper limit exhaust gas recirculation amount estimated value and smaller than the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. , Configured to determine that the misfire region is,
When it is determined that the misfire region is determined by the misfire region determining means, the spark ignition combustion mode and the premixed compression ignition combustion mode can be switched.
A control device for an internal combustion engine.

(2) The premixed compression ignition lower limit exhaust gas recirculation amount estimation value is corrected using at least one information among the water temperature, the intake air temperature, the exhaust gas temperature, the in-cylinder wall surface temperature, and the combustion temperature of the internal combustion engine. Equipped with premixed compression ignition lower limit exhaust gas recirculation correction means,
The control apparatus for an internal combustion engine according to (1) above, wherein
According to the present invention, the misfire region can be determined with higher accuracy, and exhaust gas, fuel consumption, and drivability can be more reliably improved.

(3) An operation state prediction means for predicting an operation state of at least the next combustion cycle from the current combustion cycle of the internal combustion engine,
With
The spark ignition upper limit exhaust gas recirculation amount estimating means, the premixed compression ignition lower limit exhaust gas recirculation amount estimating means, the misfire region determining means, and the premixed compression ignition lower limit exhaust gas recirculation amount setting means are the operation Operating based on the operating state of the next combustion cycle predicted by the state predicting means;
The control apparatus for an internal combustion engine according to the above (1) or (2), wherein
According to the present invention, the EGR change in the present invention that is significantly greater than that in the conventional EGR control can be achieved before reaching the predicted combustion cycle, and the influence of the response delay of the actuator can be reduced. , Fuel economy, and drivability can be improved.

(4) The exhaust gas recirculation amount that is determined to be the misfire region by the misfire region determination means and that is changed from the current exhaust gas recirculation amount to the premixed compression ignition lower limit exhaust gas recirculation amount estimated value is the internal combustion engine. The spark ignition combustion mode and the premixed compression ignition combustion when the exhaust gas recirculation amount corresponding to the change limit amount of the actuator that introduces exhaust gas recirculation of the internal combustion engine into the cylinder during one cycle of combustion is exceeded Combustion mode switching standby means for waiting for switching between modes,
The control apparatus for an internal combustion engine according to any one of (1) to (3), wherein the control apparatus is provided.
According to the present invention, when there is no means for avoiding the misfire region, priority is given to maintaining good combustion, and drivability can be improved.

  DESCRIPTION OF SYMBOLS 1 Engine, 2 cylinder, 3 piston, 4 combustion chamber, 5 crankshaft, 6 crank angle sensor, 7 water temperature sensor, 8 intake manifold, 9 exhaust manifold, 10 intake valve, 11 exhaust valve, 12 intake variable valve mechanism, 13 exhaust Variable valve mechanism, 14 Fuel injection valve, 15 Spark plug, 16 Ignition coil, 17 Surge tank, 18 Throttle valve, 19 Boost pressure sensor, 20 Intake temperature sensor, 21 Exhaust temperature sensor, 22 Electronic control unit (ECU) for engine control , 23 operation state prediction means, 24 spark ignition upper limit exhaust gas recirculation amount estimation means, 25 premix compression ignition lower limit exhaust gas recirculation amount estimation means, 26 premix compression ignition lower limit exhaust gas recirculation amount correction means, 27 misfire region determination means, 28 Premixed compression ignition lower limit exhaust gas recirculation amount setting means, 2 Combustion mode switching standby means

Claims (4)

A spark ignition combustion mode in which a mixture of air and fuel in a cylinder of the internal combustion engine is burned by an ignition plug, and an exhaust valve of the internal combustion engine is controlled in the cylinder by controlling the opening and closing timings of the exhaust valve and the intake valve of the internal combustion engine. the mixture was warmed to recirculate, and the internal combustion engine HCCI combustion mode for burning by compression self-ignition in the latter half of the compression stroke of, and is switched based on the operating state of the internal combustion engine combustion An engine control device,
Spark ignition upper limit exhaust gas recirculation amount estimation means for calculating an estimated value of spark ignition upper limit exhaust gas recirculation amount operable in the spark ignition combustion mode based on the operating state of the internal combustion engine;
Premixed compression ignition lower limit exhaust gas recirculation amount estimating means for calculating a premixed compression ignition lower limit exhaust gas recirculation amount estimated value operable in the premixed compression ignition combustion mode based on the operating state of the internal combustion engine;
A misfire region determination means for determining whether or not an exhaust gas recirculation amount control value set based on an operating state of the internal combustion engine is in a misfire region of the internal combustion engine;
When it is determined by the misfire region determination means that the misfire region is present, the premixed compression ignition lower limit exhaust gas recirculation that can set the exhaust gas recirculation amount control value to the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. A quantity setting means;
With
The misfire region determination means, when the exhaust gas recirculation amount control value is larger than the spark ignition upper limit exhaust gas recirculation amount estimated value and smaller than the premixed compression ignition lower limit exhaust gas recirculation amount estimated value. , Configured to determine that the misfire region is,
When it is determined that the misfire region is determined by the misfire region determining means, the spark ignition combustion mode and the premixed compression ignition combustion mode can be switched.
A control device for an internal combustion engine. Premixed compression for correcting the premixed compression ignition lower limit exhaust gas recirculation amount estimated value using at least one information among water temperature, intake air temperature, exhaust gas temperature, in-cylinder wall surface temperature, and combustion temperature of the internal combustion engine Equipped with an ignition lower limit exhaust gas recirculation correction means,
The control apparatus for an internal combustion engine according to claim 1. An operation state prediction means for predicting an operation state of at least the next combustion cycle from the current combustion cycle of the internal combustion engine;
With
The spark ignition upper limit exhaust gas recirculation amount estimating means, the premixed compression ignition lower limit exhaust gas recirculation amount estimating means, the misfire region determining means, and the premixed compression ignition lower limit exhaust gas recirculation amount setting means are the operation Operating based on the operating state of the next combustion cycle predicted by the state predicting means;
The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by the above. The exhaust gas recirculation amount that is determined by the misfire region determination means to be the misfire region and is changed from the current exhaust gas recirculation amount to the estimated premixed compression ignition lower limit exhaust gas recirculation amount is one cycle of the internal combustion engine. Between the spark ignition combustion mode and the premixed compression ignition combustion mode when the exhaust gas recirculation amount corresponding to the change limit amount of the actuator that introduces exhaust gas recirculation of the internal combustion engine into the cylinder during combustion is exceeded. the control device according to any one of claims 1 to 3, characterized in that example Bei combustion mode switching waiting means for waiting to switch between.