JP6001920B2 - Engine combustion control device - Google Patents

Description

  In the present invention, a part of the in-cylinder air is caused to flow into the exhaust system and burned in an air-fuel ratio rich state, and the exhaust gas is mixed with the air that has flowed into the exhaust system to obtain an air-fuel ratio corresponding to the purification capacity of the catalyst. The present invention relates to an engine combustion control device.

  Conventionally, in the fast idle after the engine is started, the air-fuel ratio is made lean and the ignition timing is retarded from the viewpoint of exhaust measures. This is to achieve an early activation of the catalyst by increasing the exhaust temperature by retarding the ignition timing by suppressing the amount of HC (hydrocarbon) emission in the exhaust gas by making the air-fuel ratio lean. It is because it can do.

  However, lean air-fuel ratio and retarded ignition timing in fast idling lead to instability of combustion and promote discharge of unfueled gas, so air-fuel ratio control that does not exceed the lean limit is required. The

  Further, in recent vehicles such as small displacement vehicles, hybrid vehicles, CVT vehicles, etc., there is a tendency that a low rotation and high load operation region is frequently used in order to improve fuel efficiency. In addition, knocking is likely to occur during low-rotation high-load operation or maximum load operation (WOT: Wide Open Throttle). When knocking occurs, control is performed to retard the ignition timing and avoid knocking. If this is done, the torque will decrease.

  For example, a technique disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2009-293424) is used as means for realizing stabilization of combustion at the time of fast idling and effectively avoiding knocking at the time of high load operation. It is possible to do. This document discloses a technique in which an intake valve or an exhaust valve is temporarily opened during a compression stroke so that a part of the air amount in the cylinder is discharged to the intake system or the exhaust system.

  If this technology is applied to combustion control, the effective compression ratio can be reduced by allowing a portion of the air that is sucked into the cylinder during the intake stroke (hereinafter referred to as “in-cylinder air”) to flow into the intake system or the exhaust system. As a result, knocking can be effectively avoided without retarding the ignition timing.

JP 2009-293424 A

  In the technique disclosed in the above-described document, since fuel is injected with both the intake valve and the exhaust valve closed, the fuel supplied into the cylinder flows out to the intake system or the exhaust system. Therefore, for example, when a part of the air in the cylinder is discharged to the exhaust system by opening the exhaust valve, for example, the air-fuel ratio of the exhaust system is equal to the amount of the outflowed air with respect to the air-fuel ratio in the cylinder. Become lean.

  However, the above-mentioned document does not clearly describe the relationship between the air-fuel ratio in the cylinder and the air-fuel ratio of the exhaust gas flowing through the exhaust system, and the air-fuel ratio lean state of the exhaust gas passing through the catalyst has been continued. In this case, there is an inconvenience that oxygen excess is caused and the catalyst purification ability cannot be fully exhibited.

  In view of the above circumstances, the present invention can appropriately control the air-fuel ratio of the exhaust gas flowing into the catalyst, realizes stabilization of combustion at the time of fast idling, and further achieves low rotation high load operation and maximum load. An object of the present invention is to provide an engine combustion control device capable of effectively avoiding the occurrence of knocking during operation.

According to the first aspect of the present invention, there is provided a combustion control apparatus for an engine, an air discharge valve for opening and closing a combustion chamber and an exhaust system, discharge valve driving means for opening and closing the air discharge valve, and fuel injection into the combustion chamber. Fuel injection means, a catalyst disposed in the exhaust system, and control means for operating the exhaust valve driving means and the fuel injection means. The control means is an empty space corresponding to the purification capacity of the catalyst. A fuel injection setting means for setting a fuel injection amount to become the fuel ratio, a cylinder target air-fuel ratio setting means for obtaining a cylinder target air-fuel ratio capable of exhibiting a maximum torque by combustion in the combustion chamber, and the fuel injection setting A required exhaust air amount for setting a required exhaust air amount to obtain the in-cylinder target air-fuel ratio based on the fuel injection amount calculated by the means and the in-cylinder target air-fuel ratio set by the in-cylinder target air-fuel ratio setting means Setting means; A drive signal corresponding to the required exhaust air amount set by the required exhaust air amount setting means is output to the exhaust valve drive means to open the air exhaust valve at a predetermined timing, and close the exhaust valve. And a drive control means for outputting a drive signal corresponding to the fuel injection amount set by the fuel injection setting means to the fuel injection means, and an operation area where the engine operating state is set as a fast idle area and a low load knock. Driving region determining means for determining any one of a region, a maximum load region, and a normal control region, the drive control means, wherein the driving region determining means determines that the driving region is the fast idle region or the low load knock region. If it is determined, the opening timing of the discharge valve is set with reference to the bottom dead center of the compression stroke. If it is determined that the maximum load range, the opening timing of the discharge valve is set. Ing the set based on the intake stroke top dead center.
A combustion control apparatus for a second engine according to the present invention includes an air discharge valve that opens and closes between a combustion chamber and an exhaust system, discharge valve driving means that opens and closes the air discharge valve, and fuel injection into the combustion chamber. Fuel injection means, a catalyst disposed in the exhaust system, and control means for operating the exhaust valve driving means and the fuel injection means. The control means is an empty space corresponding to the purification capacity of the catalyst. A fuel injection setting means for setting a fuel injection amount to become the fuel ratio, a cylinder target air-fuel ratio setting means for obtaining a cylinder target air-fuel ratio capable of exhibiting a maximum torque by combustion in the combustion chamber, and the fuel injection setting A required exhaust air amount for setting a required exhaust air amount to obtain the in-cylinder target air-fuel ratio based on the fuel injection amount calculated by the means and the in-cylinder target air-fuel ratio set by the in-cylinder target air-fuel ratio setting means Setting means; A drive signal corresponding to the required exhaust air amount set by the required exhaust air amount setting means is output to the exhaust valve drive means to open the air exhaust valve at a predetermined timing, and close the exhaust valve. And a drive control means for outputting a drive signal corresponding to the fuel injection amount set by the fuel injection setting means to the fuel injection means, and an operation area where the engine operating state is set as a fast idle area and a low load knock. An operation region determination means for determining any of the region, the maximum load region, and the normal control region, and the drive control means, when the operation region determination means determines that the operation region is the low load knock region, The valve opening timing of the discharge valve is set based on the bottom dead center of the compression stroke, and the negative load generated by exhaust pulsation in the maximum load region or the fast idle region. Waves If it is determined to be lower than the cylinder pressure in the intake stroke is set to the reference intake stroke top dead center of the opening timing of the exhaust valve.

  According to the present invention, the in-cylinder target air-fuel ratio and the in-cylinder target air-fuel ratio based on the fuel injection amount that becomes the air-fuel ratio corresponding to the purification ability of the catalyst and the in-cylinder target air-fuel ratio that can exhibit the maximum torque by combustion in the combustion chamber The required amount of exhaust air is set so that the amount of air corresponding to the required amount of exhaust air is discharged to the exhaust system, and fuel injection is set after the discharge of air is completed. When exhausting the exhaust system to the exhaust system, the fuel does not blow through the exhaust system, and the in-cylinder air-fuel ratio can be made relatively rich, combustion is stable during fast idling, low rotation high load operation and maximum It is possible to effectively avoid the occurrence of knocking during load operation. Further, since the exhaust air is exhausted to the exhaust system, mixing with the combustion gas provides an appropriate air-fuel ratio, and good exhaust gas purification performance can be obtained.

Schematic configuration diagram of an engine according to the first embodiment Schematic of exhaust cam structure Same configuration diagram of engine control system (A) is explanatory drawing of a driving | running | working area | region determination map, (b) is explanatory drawing of a target idle speed table. Same characteristic chart showing the relationship between required air discharge, engine torque, equivalence ratio, and in-cylinder air FIG. 6 is an explanatory diagram showing the relationship between the opening timing of the exhaust valve by the auxiliary cam during standby control and the fuel injection timing Explanatory drawing which shows the opening timing of the exhaust valve by the auxiliary cam at the time of fast idle control and partial load knock control FIG. 6 is an explanatory diagram showing the relationship between the opening timing of the exhaust valve by the auxiliary cam and the fuel injection timing during WOT control. The flowchart showing the exhaust valve opening timing setting routine by the auxiliary cam Same as above, flowchart showing atmospheric control subroutine The flowchart showing the fast idle control subroutine The flowchart showing the partial load knock control subroutine The flowchart showing the WOT control subroutine Schematic configuration diagram of an engine according to the second embodiment

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
1 to 13 show a first embodiment of the present invention. 1, reference numeral 1 denotes an engine body, 2 a piston, 3 a combustion chamber, 4 an intake port, 5 an exhaust port, 6 an intake valve, 7 an exhaust valve, and an intake passage 8 communicating with the intake port 4. A throttle valve 9 is interposed, and an air cleaner 10 is disposed upstream of the intake passage 8. An injection hole of an in-cylinder direct injection injector 11 as a fuel injection means is exposed at the center of the top surface of the combustion chamber 3, and an ignition portion of the spark plug 12 is exposed at one side of the combustion chamber 3. Further, an exhaust passage 13 communicates with the exhaust port 5 and communicates with a muffler (not shown). Further, a catalyst 14 for purifying the exhaust gas is interposed in the exhaust passage 13.

  The intake valve 6 and the exhaust valve 7 are opened and closed by the intake cam 15 and the exhaust cam 16 at a predetermined timing. The intake cam 15 and the exhaust cam 16 are respectively attached to the intake cam shaft 17 and the exhaust cam shaft 18, and the intake valve 6 and the exhaust valve 7 are rotated by 1/2 of the rotation of the engine. Is opened and closed.

  A variable valve timing (VVT) mechanism 19 is disposed on the exhaust camshaft 18. As shown in FIG. 2, the VVT mechanism 19 is provided with a VVT shaft 19a extending coaxially with respect to the exhaust cam shaft 18, and an auxiliary cam 20 as a discharge valve driving means is provided on the VVT shaft 19a. It is attached to the shaft. The auxiliary cam 20 is disposed adjacent to the exhaust cam 16 and is in sliding contact with the tappet 7 a of the exhaust valve 7 together with the exhaust cam 16.

  The VVT mechanism 19 changes the rotational phase of the auxiliary cam 20 by the operating pressure (or operating signal) supplied from the VVT actuator 21 such as a hydraulic solenoid (or electromagnetic solenoid). When changed, the opening timing of the exhaust valve 7 opened and closed by the auxiliary cam 20 is variably controlled. 6 to 8 show the opening timing of the exhaust valve 7 by the auxiliary cam 20.

  That is, when the auxiliary cam 20 is advanced and the cam crest of the auxiliary cam 20 is moved to the cam crest of the exhaust cam 16, the auxiliary cam 20 is idled. As shown in FIG. 7, when the auxiliary cam 20 is advanced to the compression stroke side, the exhaust valve 7 is opened at the initial stage of the compression stroke. Further, as shown in FIG. 8, when the auxiliary cam 20 is moved to the intake stroke side, the exhaust valve 7 is opened at the initial stage of the intake stroke.

  When the exhaust valve 7 is opened at the beginning of the compression stroke, a part of the amount of air sucked into the cylinder is discharged to the exhaust system by the pressing force of the piston 2. When the exhaust valve 7 is opened at the beginning of the intake stroke, a part of the amount of air sucked into the cylinder is discharged to the exhaust system using the pulsation of the exhaust system. Therefore, in this embodiment, the exhaust valve 7 that is opened by the auxiliary cam 20 serves as an air discharge valve.

  When the exhaust valve 7 is opened at the initial stage of the compression stroke, air can be surely discharged to the exhaust system by the pressing force of the piston 2, but when the mixture is prevented from being blown out, the injection timing is Since it must be set after 7 is closed, there may be a case where gas-liquid mixing cannot be sufficiently performed in the cylinder depending on the operation region.

  On the other hand, if the exhaust valve 7 is opened at the initial stage of the intake stroke, the injection timing can be advanced and the gas-liquid mixture can be sufficiently mixed. However, in order to discharge the air in the cylinder to the exhaust system, the pulsation pressure (exhaust pulsation pressure) generated in the exhaust system must be lower than the pressure in the cylinder, so that the operating range is limited. For this reason, in this embodiment, the phase angle of the auxiliary cam is set for each operation region, and the optimum air discharge mode is selected (details will be described later).

  1 is disposed immediately downstream of the air cleaner 10 to measure the intake air amount Q, 23 is a water temperature sensor that detects the cooling water temperature Tw, and 24 is immediately upstream of the catalyst 14. It is an air-fuel ratio sensor as an air-fuel ratio detecting means that is disposed and detects an oxygen concentration (air-fuel ratio) in exhaust gas.

  Signals detected by the sensors are input to an electronic control unit (ECU) 26 as control means. The ECU 26 is configured around a well-known microcomputer comprising a CPU, ROM, RAM, and the like, and in accordance with a control program stored in advance in the CPU, an injector drive circuit 27 that drives the in-cylinder direct injection injector 11, and A drive signal is output to the VVT actuator 21. In addition to the sensors described above, an engine speed sensor 25 that detects the engine speed Ne is connected to the input side of the ECU 26.

  As shown in FIG. 4A, the ECU 26 refers to the operation region determination map on the basis of the engine speed Ne and the intake air amount Q that is a substitute for the engine load, and waits with a low possibility of occurrence of knocking. The control region I, the partial load knock region II, and the maximum load (WOT) region III, which are likely to generate knock even in the partial load operation, are specified. Further, immediately after the engine is started, as shown in FIG. 5B, it is checked whether or not the engine temperature (cooling water temperature Tw) is in the fast idle region IV based on the cooling water temperature Tw. The low rotation high load operation is included in the partial load knock region II, and the low rotation side of the WOT region III is a low rotation high load operation.

  Then, the ECU 26 controls the phase of the auxiliary cam 20 according to each operation region, varies the valve opening timing of the exhaust valve 7, and discharges it to the exhaust system so that the in-cylinder air-fuel ratio becomes the target air-fuel ratio. The amount of air to be discharged (hereinafter referred to as “exhaust air amount”) is adjusted.

  Specifically, the auxiliary cam phase control executed by the ECU 26 is processed in accordance with an auxiliary cam phase control routine shown in FIG.

  This routine is executed every set calculation cycle after the engine is started. First, in step S1, the intake air amount Q detected by the intake air amount sensor 22, the engine speed Ne detected by the engine speed sensor 25, and the water temperature sensor. The cooling water temperature Tw detected at 23 is read.

  Next, the process proceeds to step S2, and the cooling water temperature Tw is compared with a preset fast idle determination water temperature To. As shown in FIG. 4B, the fast idle determination water temperature To is the warm-up completion temperature, and the water temperature region below the fast idle determination water temperature To is set as the fast idle region IV.

  If Tw ≧ To, it is determined that the fast idle control has ended, and the process proceeds to step S3. On the other hand, in the case of Tw <To, it is determined that fast idling, which is a warm-up operation after cold start, is branched to step S4, fast idle control is executed, and the process proceeds to step S9. The fast idle control executed in step S4 will be described later.

  Further, when proceeding to step S3, based on the intake air amount Q and the engine speed Ne, the operation region is set with reference to the operation region determination map with interpolation calculation, and the operation proceeds to step S5. FIG. 4A shows the concept of the driving region determination map. As shown in the figure, the operation area includes a WOT area III in which the throttle valve 9 is almost fully open, a partial load knock area II in which knocking is likely to occur even at a partial load, and normal control in which the possibility of knocking is low. It is divided into standby areas I, which are areas. Note that NIDL in the figure is an idle speed set after the completion of warm-up.

  Then, it progresses to step S5 and determines the present driving | operation area | region. And when it determines with the standby area | region I, it progresses to step S6, performs standby control, and progresses to step S9. If it is determined that the partial load knock region II is determined, the process proceeds to step S7, partial load knock control is executed, and the process proceeds to step S9. If it is determined that the region is the WOT region III, the process proceeds to step S8, WOT control is executed, and the process proceeds to step S9. The control of each operation region will be described later. In addition, the process in step S3, S4 mentioned above respond | corresponds to the driving | running | working area | region determination means of this invention.

  Then, the process proceeds to step S9, fuel injection control is executed, and the routine is exited. In step S9, in the processing after executing the standby control in step S6, normal air-fuel ratio feedback control is executed, and the fuel injection amount corresponding to the preset air-fuel ratio is used for in-cylinder direct injection at a predetermined timing. Inject from the injector 11. On the other hand, in the processing after the control for each operation region is executed in any of steps S4, S7, and S8, the fuel injection amount TINJ obtained in steps S4, S7, and S8 is used to open the exhaust valve 7 by the auxiliary cam 20. The fuel is injected by outputting an injection signal having an injection start timing immediately after the end of the valve period. Thus, even if the auxiliary cam 20 opens the exhaust valve 7 in any of steps S4, S7, and S8, the fuel does not blow through the exhaust system.

  The processing in step S9 described above, the processing in steps S25 to S27 of the fast idle control subroutine described later, the processing in steps S34 to S36 in the partial load knock control subroutine, and the steps S44 to S46 in the WOT control subroutine. The processing corresponds to the drive control means of the present invention.

(Standby control)
The standby control processed in step S6 of the auxiliary cam phase control routine is executed in the standby control subroutine shown in FIG. 10, and in step S11, the cam phase angle θC is set with a preset initial standby angle θINI [° C A]. (ΘC ← θINI). The initial standby angle θINI is set to the reference phase angle (0 [° C. A]) of the auxiliary cam 20.

  In step S12, a drive signal corresponding to the cam phase angle θC is output to the VVT actuator 21, and the routine is exited. This initial standby angle θINI is set so that the cam crest of the auxiliary cam 20 moves to the valve opening position of the intake valve 6. The VVT mechanism 19 advances the fast idle auxiliary cam 20 to substantially the same crank angle as the valve opening position of the exhaust valve 7 in accordance with a drive signal from the ECU 26. As a result, as shown in FIG. 6, since the cam crest of the auxiliary cam 20 moves into the cam crest of the exhaust cam 16 and is idled, air-fuel ratio feedback control with the compression ratio = expansion ratio is performed, and the injection is performed in the intake stroke. A predetermined amount of fuel is injected from the in-cylinder direct injection injector 11 into the target cylinder. The air-fuel ratio feedback control is well known and will not be described.

  In this embodiment, since the exhaust valve 7 also serves as an air discharge valve, the number of parts can be simplified.

(Fast idle control)
The fast idle control executed in step S4 of the auxiliary cam phase control routine is processed according to the fast idle control subroutine shown in FIG. In this subroutine, first, in step S21, the target idle speed NIDO is set based on the coolant temperature Tw with reference to the target idle speed table. FIG. 4B shows the concept of the target idle speed table. As shown in the figure, the target idle speed NIDO of the fast idle region IV is set to a higher target idle speed NIDO as the cooling water temperature Tw is lower. When the fast idle determination water temperature To is reached, this target idle speed NIDO is set. The rotational speed NIDO is fixed to the normal idle rotational speed NIDL.

  In step S22, the fuel injection amount TINJ corresponding to the target idle speed NIDO is set. Note that the air-fuel ratio is a value corresponding to the exhaust purification capacity of the catalyst 14, and in this embodiment, it is set to stoichiometric or slightly leaner than that. The processing in this step corresponds to the fuel injection setting means of the present invention.

  Thereafter, the process proceeds to step S23, and the in-cylinder target air-fuel ratio λIN that becomes the maximum torque is set with reference to the torque map. The processing in this step corresponds to the cylinder target air-fuel ratio setting means of the present invention.

  FIG. 5 shows the relationship between the in-cylinder equivalent ratio 1 / in-cylinder λ and the in-cylinder air amount corresponding to the reciprocal of the in-cylinder air amount and the in-cylinder air-fuel ratio.

  The sum of the in-cylinder air amount and the exhaust air amount blown into the exhaust system is taken as the intake air amount Q measured by the intake air amount sensor 22 and the amount of fuel injected from the in-cylinder direct injection injector 11 is made constant. In this case, if the exhaust air amount is increased, the in-cylinder air amount naturally decreases, so that the in-cylinder air-fuel ratio becomes rich. The in-cylinder air amount is substantially proportional to the reachable torque when ignoring the knock, and the relationship between the in-cylinder equivalence ratio and the ease of occurrence of the knock is also almost proportional. As a result, when the amount of exhaust air is gradually increased, the engine torque increases along the initial in-cylinder equivalence ratio 1 / in-cylinder λ. This is because knocking is less likely to occur due to the rich air-fuel ratio, and the ignition timing can be advanced in the MBT (Minimum spark advance for Best Torque) direction accordingly. However, if the exhaust air amount is further increased thereafter, the in-cylinder air-fuel ratio becomes overrich, and the engine torque decreases almost in proportion to the decrease in the in-cylinder air amount.

  In step S23, the cylinder capable of obtaining the maximum torque by the advance of the ignition timing from the balance between the torque increase due to the enrichment of the cylinder target air-fuel ratio λIN and the torque decrease due to the decrease in the cylinder air amount. The internal target air-fuel ratio λIN is obtained from map search or calculation.

  Then, the process proceeds to step S24, and the required exhaust air amount QOUT is set from the following equation based on the intake air amount Q, the engine speed Ne, the fuel injection amount TINJ, and the in-cylinder target air-fuel ratio λIN. The processing in this step corresponds to the required exhaust air amount setting means of the present invention.

QOUT ← Q-QM (1)
QM ← TINJ · Ne / λIN (2)
Here, QM is the target air amount in the cylinder.

  Thereafter, the process proceeds to step S25, and the cam phase angle θBDC [° C. A (crank angle)] of the auxiliary cam 20 corresponding to the required exhaust air amount QOUT is set. In the present embodiment, the cam phase angle θBDC at the time of fast idle control is set based on the compression stroke bottom dead center BDC. When the cam phase angle θBDC is retarded toward the top dead center side of the intake stroke, the required amount of exhaust air per unit time due to the increase in internal pressure accompanying the rise of the piston 2 even if the valve opening period of the exhaust valve 7 is constant. Since QOUT increases, an optimal in-cylinder air amount can be obtained by setting the cam phase angle θBDC of the auxiliary cam 20. Note that if the cam phase angle θBDC is advanced from the compression stroke bottom dead center BDC to the intake stroke top dead center side, the pressure in the cylinder has not risen even if the exhaust valve 7 is opened. Further, the required exhaust air amount QOUT from the exhaust valve 7 can be reduced.

  Then, the process proceeds to step S26, and based on the cam phase angle θBDC, the initial standby angle θINI described above is converted into the cam phase angle θC with the reference angle 0 [° C. A] (θC ← f (θBDC)), and the process proceeds to step S27. Then, a drive signal corresponding to the cam phase angle θC is output to the VVT actuator 21 and the routine is exited.

  The VVT mechanism 19 retards the phase of the fast idle auxiliary cam 20 to near the compression stroke bottom dead center BDC in accordance with the drive signal from the ECU 26. As a result, the exhaust valve 7 is opened in the vicinity of the compression stroke bottom dead center BDC, and an exhaust air amount corresponding to the required exhaust air amount QOUT is exhausted to the exhaust system. Then, after the exhaust valve 7 is closed to a predetermined level, fuel of the fuel injection amount TINJ is injected from the in-cylinder direct injection injector 11 (see FIG. 7), and the air-fuel mixture in the cylinder can obtain the maximum torque. The in-cylinder target air-fuel ratio λIN is set. As a result, the ignition timing at the time of fast idling can be advanced more than before, and warm-up performance and exhaust gas performance can be improved by stabilizing combustion.

  When the combustion gas (exhaust gas) in the cylinder is discharged to the exhaust system in the exhaust stroke, it is mixed with the exhaust air discharged in the vicinity of the compression stroke bottom dead center BDC. Therefore, the exhaust gas passing through the catalyst 14 is It becomes stoichio or weak lean, and exhaust gas can be purified efficiently.

(Partial load knock control)
The partial load knock control executed in step S7 of the auxiliary cam phase control routine is processed according to the partial load knock control subroutine shown in FIG.

  In this subroutine, first, in step S31, the fuel injection amount TINJ is calculated. This fuel injection amount TINJ is based on parameters such as the intake air amount Q, the engine speed Ne, the coolant temperature Tw, the air-fuel ratio A / F in the exhaust gas detected by the air-fuel ratio sensor 24, and the like by well-known air-fuel ratio feedback control. Ask. The processing in this step corresponds to the fuel injection setting means of the present invention.

  Then, the process proceeds to step S32, where the in-cylinder target air-fuel ratio λIN, which is the maximum torque, is increased by increasing the in-cylinder target air-fuel ratio λIN, and the in-cylinder air amount is decreased, as in the case of the above-described fast idle. From the balance with the torque decrease, the in-cylinder target air-fuel ratio λIN at which the maximum torque can be obtained by the advance of the ignition timing is obtained by referring to the torque map or by calculation. The processing in this step corresponds to the cylinder target air-fuel ratio setting means of the present invention.

  Thereafter, the process proceeds to step S33, and the required exhaust air amount QOUT is set from the above-described equation (1) based on the intake air amount Q, the engine speed Ne, the fuel injection amount TINJ, and the in-cylinder target air-fuel ratio λIN.

  Thereafter, the process proceeds to step S34, and the cam phase angle θBDC [° C. A] of the auxiliary cam 20 corresponding to the required exhaust air amount QOUT is set. This cam phase angle θBDC is set with reference to the compression stroke bottom dead center BDC as in the above-described fast idle control.

  In step S35, the cam phase angle θBDC is converted into a cam phase angle θC having the initial standby angle θINI as the reference angle 0 [° C. A] (θC ← f (θBDC)). A drive signal corresponding to the angle θC is output to the VVT actuator 21 and the routine is exited.

  The VVT mechanism 19 retards the phase of the auxiliary cam 20 in the partial load knock region II (see FIG. 4) to near the compression stroke bottom dead center BDC in accordance with the drive signal from the ECU 26. Then, as shown in FIG. 7, the exhaust valve 7 is opened in the vicinity of the compression stroke bottom dead center BDC, and an exhaust air amount corresponding to the required exhaust air amount QOUT is exhausted to the exhaust system.

  Then, after the exhaust valve 7 is closed to a predetermined value, the fuel for the fuel injection amount TINJ is injected into the cylinder from the in-cylinder direct injection injector 11, and the mixture in the cylinder can obtain the maximum torque. A rich in-cylinder target air-fuel ratio λIN is set. As a result, the occurrence of knocking is suppressed, the ignition timing can be relatively advanced, and a good engine output can be obtained. Furthermore, fuel consumption can be improved by stabilizing the combustion.

  When the combustion gas in the cylinder is discharged to the exhaust system in the exhaust stroke, the exhaust gas mixed with the exhaust air discharged in the vicinity of the compression stroke bottom dead center BDC and passing through the catalyst 14 is a known air-fuel ratio. Since the target air-fuel ratio is set by feedback control, the purification process is satisfactorily performed.

(WOT control)
The WOT control executed in step S8 of the auxiliary cam phase control routine is processed according to the WOT control subroutine shown in FIG.

    In this subroutine, first, in step S41, the fuel injection amount TINJ is obtained by air-fuel ratio feedback control as in step S31 described above. The processing in this step corresponds to the fuel injection setting means of the present invention.

  Thereafter, the process proceeds to step S42, where the in-cylinder target air-fuel ratio λIN that is the maximum torque is increased by increasing the in-cylinder target air-fuel ratio λIN, and the in-cylinder air amount is decreased, as in the case of the above-described fast idle. From the balance with the torque decrease, the in-cylinder target air-fuel ratio λIN at which the maximum torque can be obtained by the advance of the ignition timing is obtained by referring to the torque map or by calculation. The processing in this step corresponds to the cylinder target air-fuel ratio setting means of the present invention.

  Next, the routine proceeds to step S43, where the required exhaust air amount QOUT is set from the above-described equation (1) based on the intake air amount Q, the engine speed Ne, the fuel injection amount TINJ, and the in-cylinder target air-fuel ratio λIN.

  Thereafter, the process proceeds to step S44, and the cam phase angle θTDC [° C. A] of the auxiliary cam 20 corresponding to the required exhaust air amount QOUT is set. This cam phase angle θTDC is set with reference to the intake stroke top dead center TDC.

  Next, the process proceeds to step S45, where the cam phase angle θTDC is converted into the cam phase angle θC with the initial standby angle θINI as the reference angle 0 [° C. A] (θC ← f (θTDC)). A drive signal corresponding to the angle θC is output to the VVT actuator 21 and the routine is exited.

  The VVT mechanism 19 retards the phase of the auxiliary cam 20 in the WOT region III (see FIG. 4) to near the intake stroke top dead center TDC in accordance with a drive signal from the ECU 26. Then, as shown in FIG. 8, the exhaust valve 7 is opened near the intake stroke top dead center TDC. In the WOT region III, the negative pressure wave due to the exhaust pulsation increases (the pressure decreases). Therefore, by opening the exhaust valve 7 even in the intake stroke, the differential pressure between the cylinder and the exhaust system causes a difference in the cylinder. Air can be discharged to the exhaust system.

  Further, if the phase of the auxiliary cam 20 is advanced from the intake stroke top dead center TDC to the exhaust stroke side, the valve opening period by the auxiliary cam 20 in the intake stroke is substantially shortened, so the cam phase angle θTDC is adjusted. By doing so, the amount of exhaust air can be adjusted, and the air-fuel mixture in the cylinder can be set to the in-cylinder target air-fuel ratio λIN from which the maximum torque can be obtained.

  Furthermore, in this embodiment, since the fuel injection timing is set immediately after the opening period of the exhaust valve 7 by the auxiliary cam 20 ends, the fuel injection timing can be set during the intake stroke in the WOT region III. . As a result, the injected fuel and air can be sufficiently mixed in the cylinder to generate a homogeneous air-fuel mixture, thereby improving the isovolume and further improving the thermal efficiency. Further, since the air-fuel ratio at the time of combustion is rich, the generation of knock can be effectively avoided. Furthermore, since knock can be effectively avoided, the ignition timing can be advanced accordingly, and a good engine output can be obtained.

  Further, since the combustion gas discharged in the exhaust stroke is mixed with the exhaust air discharged to the exhaust system, it becomes a value corresponding to the target air-fuel ratio set by the well-known air-fuel ratio feedback control, and the catalyst 14 And is well purified.

  In the above-described embodiment, the opening timing of the exhaust valve 7 by the auxiliary cam 20 in the fast idle region IV is set near the compression stroke bottom dead center BDC, but a negative pressure wave generated by exhaust pulsation during fast idle However, when the pressure in the cylinder in the intake stroke is lower, the valve opening timing by the auxiliary cam 20 may be set to the intake stroke top dead center TDC side.

[Second Embodiment]
FIG. 14 shows a second embodiment of the present invention. In the first embodiment described above, the in-cylinder air is discharged to the exhaust system by opening the exhaust valve 7 with the auxiliary cam 20, but in this embodiment, the air discharge valve, the discharge valve driving means, The actuator valve integrated with the above function is directly controlled to open and close to adjust the amount of exhaust air. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is simplified or omitted.

  That is, in the present embodiment, the combustion chamber 3 and the exhaust passage 13 between the exhaust manifold assembly and the air-fuel ratio sensor 24 are communicated with each other by the air bypass passage 31, and the air bypass passage 31 is electromagnetically or hydraulically connected. The actuator valve 32 is interposed, and the opening / closing operation of the actuator valve 32 is controlled by the ECU 26 shown in the first embodiment.

  The opening / closing timing of the actuator valve 32 controlled by the ECU 26 is based on the required exhaust air amount QOUT obtained in each of the subroutines shown in FIGS. 11 to 13 described above, and when a negative pressure wave due to exhaust pulsation can be used, The valve 32 is opened / closed. When the negative pressure wave due to exhaust pulsation cannot be used, the opening / closing operation is performed in the compression stroke.

  In the present embodiment, since the exhaust air amount is adjusted by the opening / closing timing of the actuator valve 32, in addition to the effect of the first embodiment described above, the air amount corresponding to the required exhaust air amount QOUT is more accurately discharged. be able to.

  The present invention is not limited to the above-described embodiments. For example, the intake air amount (Q / Ne) per unit rotational speed is changed to the engine load instead of the intake air amount Q which is a parameter of the operation region map. It may be used as a substitute for.

3 ... combustion chamber,
7 ... Exhaust valve,
8 ... Intake passage,
11 ... In-cylinder direct injection injector,
13 ... exhaust passage,
14 ... Catalyst,
19 ... VVT mechanism,
20 ... auxiliary cam,
21 ... Actuator,
24 ... Air-fuel ratio sensor,
26: Electronic control unit,
27. Injector drive circuit,
32 ... Actuator valve,
QOUT: Required exhaust air volume,
TINJ ... Fuel injection amount,
θBDC, θC, θTDC ... cam phase angle,
λIN: In-cylinder target air-fuel ratio

Claims (2)

An air discharge valve that opens and closes between the combustion chamber and the exhaust system;
A discharge valve driving means for opening and closing the air discharge valve;
Fuel injection means for injecting fuel into the combustion chamber;
A catalyst disposed in the exhaust system;
Control means for operating the discharge valve driving means and the fuel injection means,
The control means includes
Fuel injection setting means for setting a fuel injection amount to be an air-fuel ratio corresponding to the purification capacity of the catalyst;
In-cylinder target air-fuel ratio setting means for obtaining an in-cylinder target air-fuel ratio capable of exhibiting maximum torque by combustion in the combustion chamber;
Based on the fuel injection amount calculated by the fuel injection setting means and the in-cylinder target air-fuel ratio set by the in-cylinder target air-fuel ratio setting means, a required exhaust air amount for setting the in-cylinder target air-fuel ratio is set. Required discharge air amount setting means,
A drive signal corresponding to the required exhaust air amount set by the required exhaust air amount setting means is output to the exhaust valve drive means to open the air exhaust valve at a predetermined timing and close the exhaust valve. A drive control means for outputting a drive signal corresponding to the fuel injection amount set by the fuel injection setting means to the fuel injection means ;
An operation region determination means for determining one of a fast idle region, a low load knock region, a maximum load region, and a normal control region as an operation region in which the engine operation state is set ;
The drive control means sets the valve opening timing of the discharge valve based on the compression stroke bottom dead center when the operation area determination means determines the operation area as the fast idle area or the low load knock area, A combustion control apparatus for an engine, characterized in that when it is determined as a maximum load region, the valve opening timing of the exhaust valve is set based on an intake stroke top dead center .
An air discharge valve that opens and closes between the combustion chamber and the exhaust system;
A discharge valve driving means for opening and closing the air discharge valve;
Fuel injection means for injecting fuel into the combustion chamber;
A catalyst disposed in the exhaust system;
Control means for operating the discharge valve driving means and the fuel injection means,
The control means includes
Fuel injection setting means for setting a fuel injection amount to be an air-fuel ratio corresponding to the purification capacity of the catalyst;
In-cylinder target air-fuel ratio setting means for obtaining an in-cylinder target air-fuel ratio capable of exhibiting maximum torque by combustion in the combustion chamber;
Based on the fuel injection amount calculated by the fuel injection setting means and the in-cylinder target air-fuel ratio set by the in-cylinder target air-fuel ratio setting means, a required exhaust air amount for setting the in-cylinder target air-fuel ratio is set. Required discharge air amount setting means,
A drive signal corresponding to the required exhaust air amount set by the required exhaust air amount setting means is output to the exhaust valve drive means to open the air exhaust valve at a predetermined timing and close the exhaust valve. A drive control means for outputting a drive signal corresponding to the fuel injection amount set by the fuel injection setting means to the fuel injection means ;
An operation region determination means for determining one of a fast idle region, a low load knock region, a maximum load region, and a normal control region as an operation region in which the engine operation state is set ;
The drive control means sets the valve opening timing of the discharge valve based on the compression stroke bottom dead center when the operation area determination means determines the operation area as the low load knock area, and the maximum load area, or When the negative pressure wave generated by exhaust pulsation in the fast idle region is determined to be lower than the in-cylinder pressure in the intake stroke, the valve opening timing of the exhaust valve is set based on the intake stroke top dead center. combustion control device to Rue engine.

Images