JP4706618B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine capable of switching an operating state between a non-supercharged stoichiometric combustion mode and a supercharged lean combustion mode.

  In a general in-cylinder injection type engine, a lean combustion mode capable of realizing homogeneous combustion at a lean air-fuel ratio and a stoichiometric combustion mode capable of realizing homogeneous combustion at a theoretical (stoichiometric) air-fuel ratio can be switched. In this case, for example, the control device has a combustion mode map based on the engine speed and the engine load, and performs switching control between the lean combustion mode and the stoichiometric combustion mode according to the engine operating state.

  In such an engine capable of switching the combustion mode, when switching between the lean air-fuel ratio and the stoichiometric air-fuel ratio according to the operating state, the generated torque differs if the air-fuel ratio is greatly changed. There is a problem that a large torque step occurs when the air-fuel ratio is switched, and drivability deteriorates.

  Therefore, conventionally, control for retarding the ignition timing is executed in order to prevent a torque step generated when the air-fuel ratio is changed. For example, when the stoichiometric combustion mode is switched to the lean combustion mode, the control device controls the stoichiometric air-fuel ratio during the switching control, and changes from stoichiometric to lean after the switching control. That is, when a command for switching from the stoichiometric combustion mode to the lean combustion mode is issued in accordance with the engine operating state, the throttle opening is increased to increase the intake air amount and the fuel injection amount. At this time, by retarding the ignition timing, an increase in the generated torque is suppressed, and after a predetermined period of time, the ignition timing is advanced to an ignition timing according to the operating state, and the fuel injection amount is decreased. By doing so, it changes from stoichiometric to lean.

  In addition, there exists what was described in following patent document 1 as such an internal combustion engine.

Japanese Patent Laid-Open No. 08-114166

  However, when the turbocharger is mounted on the internal combustion engine and the combustion mode is switched between the non-supercharged stoichiometric combustion mode and the supercharged lean combustion mode, the boost pressure becomes higher than necessary due to the increase in exhaust energy. Thus, a torque step occurs at the end of the air-fuel ratio switching control, and drivability deteriorates. That is, when switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the exhaust gas temperature rises due to the retard of the ignition timing, and the actual supercharging pressure rises above the target supercharging pressure by the turbocharger. Since the boost pressure becomes higher than necessary and the torque increases, a torque step is generated here because the increased torque needs to be reduced at the end of the air-fuel ratio switching control. In this case, since the amount of torque reduction with respect to the retard amount of the ignition timing increases as the engine load (intake air amount) increases, the torque step generated at the time of switching the combustion mode becomes conspicuous, and drivability deteriorates. The problem of end up occurs.

  In addition, when switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the ignition timing is retarded while maintaining the stoichiometric air-fuel ratio during the air-fuel ratio change control, and then changed to the lean air-fuel ratio after the air-fuel ratio change control. The ignition timing is advanced. For this reason, if the timing of the air-fuel ratio control and the ignition timing control after the air-fuel ratio change control is deviated, knocking may occur and a misfire may occur. The same applies when switching from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode. When the air-fuel ratio change control is performed, the ignition timing is retarded by changing to the stoichiometric air-fuel ratio. May lead to

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide an internal combustion engine capable of suppressing the occurrence of a torque step or knocking at the time of air-fuel ratio change and improving drivability. And

In order to solve the above-described problems and achieve the object, an internal combustion engine according to the present invention includes a supercharger capable of compressing intake air and supplying the compressed air to a combustion chamber, and a central ignition means provided at a central portion of the combustion chamber. Side ignition means provided in the periphery of the combustion chamber, air-fuel ratio changing means capable of changing the air-fuel ratio, ignition timing changing means capable of changing the ignition timing by the central ignition means and the side ignition means, In an internal combustion engine comprising a control means for retarding the ignition timing of the central ignition means and the side ignition means by the ignition timing changing means when the stoichiometric air-fuel ratio is changed from the stoichiometric air-fuel ratio by the air-fuel ratio changing means, wherein, when changing from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, in the air-fuel ratio change control is retarded ignition timing while maintaining the stoichiometric air-fuel ratio hide, the air-fuel ratio change control after Advancing the ignition timing based on the engine operating conditions as well as changes to the lean air-fuel ratio hidden, when the advancement amount is larger than a preset predetermined value, reducing the advance amount of the ignition timing in the central ignition means It is characterized by.

In the internal combustion engine of the present invention, when the control means changes from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode , during the air-fuel ratio change control, the ignition timing is retarded while maintaining the stoichiometric air-fuel ratio. After the fuel ratio change control, the air-fuel ratio is changed to a lean air-fuel ratio, the ignition timing is advanced, and the ignition timing of the side ignition means is set to MBT.

In the internal combustion engine of the present invention, when the control means changes from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode , with respect to the retard amount of the ignition timing of the central ignition means during the air-fuel ratio change control, A retard amount of the ignition timing of the side ignition means is set small.

The internal combustion engine of the present invention includes a supercharger capable of compressing intake air and supplying the compressed air to the combustion chamber, central ignition means provided at the center of the combustion chamber, and side ignition means provided at the periphery of the combustion chamber. An air-fuel ratio changing means capable of changing the air-fuel ratio, an ignition timing changing means capable of changing the ignition timing by the central ignition means and the side ignition means, and a lean air-fuel ratio to a stoichiometric air-fuel ratio by the air-fuel ratio changing means. In an internal combustion engine comprising a control means for retarding the ignition timings of the central ignition means and the side ignition means by the ignition timing changing means when changing, the control means is in a supercharged lean combustion mode and is not supercharged. when changing to the stoichiometric combustion mode, is larger than a predetermined value retarded ignition timing hidden, the retard amount of this is set in advance based on the engine operating state is changed to the stoichiometric air-fuel ratio when the air-fuel ratio switching request Kiniwa, sets the ignition timing of the side ignition means to MBT, is characterized in reducing the retard amount during air-fuel ratio variation control.

In the internal combustion engine of the present invention, when the control means changes from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode , with respect to the retard amount of the ignition timing of the central ignition means during the air-fuel ratio change control, A retard amount of the ignition timing of the side ignition means is set small.

  In the internal combustion engine of the present invention, the central ignition means is provided on the lower surface of the cylinder head above the center of the combustion chamber, and the side ignition means is above the outer periphery of the combustion chamber and between the intake port and the exhaust port. It is provided on the lower surface of the cylinder head.

According to the internal combustion engine of the present invention, when changing from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode , during the air-fuel ratio change control, the ignition timing is retarded while maintaining the stoichiometric air-fuel ratio, and the air-fuel ratio change control is performed. Later, when the air-fuel ratio is changed to a lean air-fuel ratio and the ignition timing is advanced based on the engine operating state, and the advance amount is larger than a predetermined value, the advance amount of the ignition timing in the central ignition means is reduced. Moreover, it is possible to improve the drivability by preventing the deterioration of combustion after the air-fuel ratio change control and suppressing the occurrence of a torque step and suppressing the occurrence of knocking.

According to the internal combustion engine of the present invention, when changing from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode , the ignition timing is retarded based on the engine operating state by changing to the stoichiometric air-fuel ratio when the air-fuel ratio switching request is made. , when the retard amount of this is greater than a preset predetermined value, sets the ignition timing of the side ignition means to MBT, because it reduces the amount of delay in air-fuel ratio change control, combustion of air-fuel ratio change control It is possible to improve the drivability by preventing the deterioration and suppressing the occurrence of a torque step and suppressing the occurrence of knocking.

  Embodiments of an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a schematic plan view of a V-type 6-cylinder engine representing an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of the V-type 6-cylinder engine of this embodiment, and FIG. 4 is a horizontal sectional view of the combustion chamber of the first bank in the V-type 6-cylinder engine of the example, FIG. 4 is a mode map showing combustion modes in the V-type 6-cylinder engine of the present embodiment, and FIG. FIG. 6 is a time chart showing the engine operating state when switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode in the V-type 6-cylinder engine of this embodiment. FIG. 7 is a time chart showing the engine operating state at the time of switching from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode in the V-type six-cylinder engine of the present embodiment.

  In this embodiment, a V-type 6-cylinder engine is applied as the internal combustion engine. In this V-type 6-cylinder engine, as shown in FIGS. 1 to 3, the cylinder block 11 has left and right banks 12, 13 inclined at a predetermined angle at the upper portion, and a plurality of banks 12, 13 are provided with a plurality of banks 12, 13. A cylinder is provided to form two cylinder groups. Each of the banks 12 and 13 is formed with three cylinder bores 14 and 15, and pistons 16 and 17 are fitted to the cylinder bores 14 and 15 so as to be vertically movable. A crankshaft (not shown) is rotatably supported at the lower part of the cylinder block 11, and the pistons 16 and 17 are connected to the crankshaft via connecting rods 18 and 19, respectively.

  On the other hand, cylinder heads 20 and 21 are fastened to the upper portions of the banks 12 and 13 of the cylinder block 11, and the combustion chambers 22 and 23 are constituted by the cylinder block 11, the pistons 16 and 17, and the cylinder heads 20 and 21. ing. The intake ports 24 and 25 and the exhaust ports 26 and 27 are formed on the upper portions of the combustion chambers 22 and 23, that is, the lower surfaces of the cylinder heads 20 and 21 so as to face each other. 27, the lower end portions of the intake valves 28 and 29 and the exhaust valves 30 and 31 are located. The intake valves 28 and 29 and the exhaust valves 30 and 31 are supported by the cylinder heads 20 and 21 so as to be movable in the axial direction, and are attached in a direction to close the intake ports 24 and 25 and the exhaust ports 26 and 27. It is supported. Further, intake camshafts 32 and 33 and exhaust camshafts 34 and 35 are rotatably supported on the cylinder heads 20 and 21, and the intake cams 36 and 37 and the exhaust cams 38 and 39 are interposed via a roller rocker arm (not shown). Are in contact with the upper ends of the intake valves 28 and 29 and the exhaust valves 30 and 31.

  Accordingly, when the intake camshafts 32 and 33 and the exhaust camshafts 34 and 35 rotate in synchronization with the engine, the intake cams 36 and 37 and the exhaust cams 38 and 39 operate the roller rocker arm, and the intake valves 28 and 29 and the exhaust valve 30 and 31 move up and down at a predetermined timing to open and close intake ports 24 and 25 and exhaust ports 26 and 27, intake ports 24 and 25 and combustion chambers 22 and 23, combustion chambers 22 and 23, and exhaust port 26. , 27 can communicate with each other.

  In addition, the valve mechanism of this engine is a variable intake valve timing mechanism (VVT) 40 that controls the intake valves 28 and 29 and the exhaust valves 30 and 31 at an optimal opening / closing timing according to the operating state. 41 and an exhaust variable valve mechanism 42, 43. The intake variable valve operating mechanisms 40 and 41 and the exhaust variable valve operating mechanisms 42 and 43 are configured, for example, by providing VVT controllers at the shaft end portions of the intake camshafts 32 and 33 and the exhaust camshafts 34 and 35. The opening / closing timing of the intake valves 28, 29 and the exhaust valves 30, 31 is advanced or retarded by changing the phase of each camshaft 32, 33, 34, 35 with respect to the cam sprocket by a pump (or electric motor). Is something that can be done. In this case, each variable valve mechanism 40, 41, 42, 43 advances or retards the opening / closing timing with the operating angle (opening period) of intake valves 28, 29 and exhaust valves 30, 31 being constant. The intake camshafts 32, 33 and the exhaust camshafts 34, 35 are provided with cam position sensors 44, 45, 46, 47 for detecting their rotational phases.

  A surge tank 50 is connected to the intake ports 24 and 25 of the cylinder heads 20 and 21 via intake manifolds 48 and 49. An air cleaner 52 is attached to an air intake port of the intake pipe (intake passage) 51. The intake pipe 51 is divided into two intake branch pipes 53 and 54, and the downstream ends of the intake branch pipes 53 and 54 are joined together. The intake tank 55 is connected to the surge tank 50 through the intake manifold 55. The intake manifold 55 is provided with an electronic throttle device 57 having a throttle valve 56.

  The exhaust ports 26 and 27 communicate with collecting passages 58 and 59 in which exhaust gases discharged from the combustion chambers 22 and 23 gather, and exhaust pipe connecting portions 58a and 59a are connected to the collecting passages 58 and 59, respectively. The first and second exhaust pipes 60 and 61 are connected to each other. In this case, the exhaust ports 26 and 27, the collecting passages 58 and 59, and the exhaust pipe connection portions 58a and 59a are integrally formed in the cylinder heads 20 and 21 of the left and right banks 12 and 13, respectively.

  The first exhaust pipe 60 is fitted with a first front three-way catalyst (purification catalyst) 62, while the second exhaust pipe 61 is fitted with a second front stage three-way catalyst (purification catalyst) 63. The downstream end portions of the first and second exhaust pipes 60 and 61 are joined and connected to the exhaust collecting pipe 64, and the NOx occlusion reduction type catalyst 65 is attached to the exhaust collecting pipe 64. Each of the front three-way catalysts 62 and 63 simultaneously purifies HC, CO, and NOx contained in the exhaust gas by an oxidation-reduction reaction when the exhaust air-fuel ratio is stoichiometric. The NOx occlusion reduction type catalyst 65 temporarily occludes NOx contained in the exhaust gas when the exhaust air-fuel ratio is lean, and occludes when the oxygen concentration in the exhaust gas is in the rich combustion region or stoichiometric combustion region. The released NOx is released, and NOx is reduced by the added fuel as a reducing agent.

  The first and second banks 12 and 13 are provided with turbochargers 66 and 67, respectively. In each turbocharger 66, 67, compressors 68, 69 provided in the intake branch pipes 53, 54 and turbines 70, 71 provided in the exhaust pipes 60, 61 are integrated by connecting shafts 72, 73. Concatenated. In this case, the turbochargers 66 and 67 can drive the turbines 70 and 71 by the exhaust gas from the exhaust pipes 60 and 61 of the first and second banks 12 and 13. In addition, intercoolers 74 and 75 for cooling the intake air compressed by the compressors 68 and 69 and cooled in the intake branch pipes 53 and 54 on the downstream side of the compressors 68 and 69 in the turbochargers 66 and 67. Is provided.

  Accordingly, the turbochargers 66 and 67 provided in the first and second banks 12 and 13 are connected to the exhaust pipes 60 and 61 from the combustion chambers 22 and 23 through the exhaust ports 26 and 27 and the collecting passages 58 and 59, respectively. The turbines 70 and 71 are driven by the exhaust gas discharged to the compressor, and the compressors 68 and 69 connected by the connecting shafts 72 and 73 are driven, so that the air flowing through the intake branch pipes 53 and 54 can be compressed. Therefore, the air introduced from the air cleaner 52 into the intake pipe 51 becomes compressed intake air and is cooled by the intercoolers 74 and 75 and then introduced into the surge tank 50. The intake manifolds 48 and 49 in the banks 12 and 13 and The air is sucked into the combustion chambers 22 and 23 through the intake ports 24 and 25.

  The cylinder heads 20 and 21 are respectively equipped with injectors 76 and 77 for injecting fuel (gasoline) directly into the combustion chambers 22 and 23. Delivery pipes 78 and 79 are connected to the injectors 76 and 77, respectively. Each of the delivery pipes 78 and 79 can be supplied with fuel of a predetermined pressure from a high-pressure fuel pump 80. The cylinder heads 20 and 21 are mounted with two types of spark plugs 81a, 81b, 82a and 82b which are located above the combustion chambers 22 and 23 and ignite the air-fuel mixture. The central ignition plugs 81a and 82a as the central ignition means are provided in the central part of the combustion chambers 22 and 23, while the side ignition plugs 81b and 82b as the side ignition means are provided in the peripheral part of the combustion chamber 22.23. ing.

  Specifically, in the first bank 12, as shown in detail in FIGS. 2 and 3, the central spark plug 81a has two intake ports on the lower surface of the cylinder head 20 constituting the ceiling portion of the combustion chamber 22. 24 and two exhaust ports 26 are mounted at the center. The side spark plug 81 b is a peripheral portion of the two intake ports 24 and the two exhaust ports 26 on the lower surface of the cylinder head 20 constituting the ceiling portion of the combustion chamber 22, and includes one intake port 24 and one exhaust port 26. It is located between. In the second bank 13, as in the first bank 12, the central spark plug 82 a and the side spark plug 82 b are attached to the central portion and the peripheral portion of the cylinder head 21.

  The vehicle is equipped with an electronic control unit (ECU) 83, which can control the fuel injection timing of the injectors 76, 77, the ignition timing of the spark plugs 81a, 81b, 82a, 82b, and the like. The fuel injection amount, injection timing, ignition timing, etc. are determined based on the engine operating conditions such as the detected intake air amount, intake air temperature, boost pressure, throttle opening, accelerator opening, engine speed, cooling water temperature, etc. Yes. That is, an air flow sensor 84 and an intake air temperature sensor 85 are mounted on the upstream side of the intake pipe 51, and the measured intake air amount and intake air temperature are output to the ECU 83. Further, a supercharging pressure sensor 86 is attached to the intake manifold 55, and the measured supercharging pressure is output to the ECU 83. The electronic throttle device 57 is provided with a throttle position sensor 87, and the accelerator pedal is provided with an accelerator position sensor 88, which outputs the current throttle opening and accelerator opening to the ECU 83. Further, a crank angle sensor 89 is provided on the crankshaft, and the detected crank angle is output to the ECU 83, and the ECU 83 calculates the engine speed based on the crank angle. The cylinder block 11 is provided with a water temperature sensor 90 and outputs the detected engine cooling water temperature to the ECU 83.

  In addition, A / F sensors 91 and 92 are provided upstream of the upstream three-way catalysts 62 and 63 in the exhaust pipes 60 and 61, respectively. The A / F sensors 91 and 92 detect the exhaust air / fuel ratio of the exhaust gas exhausted to the exhaust pipes 60 and 61 through the exhaust ports 26 and 27 from the combustion chambers 22 and 23, and the detected exhaust air / fuel ratio is detected. It is output to the ECU 83. The ECU 83 corrects the fuel injection amount by feeding back the exhaust air / fuel ratio detected by the A / F sensors 91 and 92 and comparing it with the target air / fuel ratio set according to the engine operating state.

  The ECU 83 can control the intake variable valve mechanisms 40 and 41 and the exhaust variable valve mechanisms 42 and 43 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idling, or when the load is light, the exhaust gas 30 is exhausted from the intake port 24, 31 by eliminating the overlap between the exhaust valve 30, 31 opening timing and the intake valve 28, 29 opening timing. 25 or the amount of air blown back to the combustion chambers 22 and 23 is reduced, and combustion stability and fuel efficiency can be improved. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valves 28 and 29 is advanced to reduce the amount of intake air that blows back to the intake ports 24 and 25, thereby improving volumetric efficiency. At the time of high load and high rotation, the closing timing of the intake valves 28 and 29 is retarded according to the rotational speed, thereby improving the volume efficiency as the timing according to the inertial force of the intake air.

  By the way, in the V-type 6-cylinder engine of the present embodiment, the ECU 83 can realize the lean combustion mode capable of realizing the homogeneous combustion at the lean air-fuel ratio according to the engine operating state and the homogeneous combustion at the theoretical (stoichiometric) air-fuel ratio. It is possible to switch between various stoichiometric combustion modes. In this case, as shown in FIG. 4, the ECU 83 has a combustion mode map based on the engine speed and the engine load (air amount), and the lean combustion mode and the stoichiometric combustion mode are determined using this combustion mode map. Is controlled.

  When the ECU 83 performs switching control between the lean combustion mode and the stoichiometric combustion mode using the combustion mode map, the ECU 83 performs control with the stoichiometric air-fuel ratio during the switching control, and changes the air-fuel ratio after the switching control. That is, when switching between the stoichiometric combustion mode and the lean combustion mode, the torque generated by changing the throttle opening and changing the fuel injection amount to maintain the stoichiometric air-fuel ratio and retarding the ignition timing The ignition timing is advanced to change to the ignition timing according to the operating state and the fuel injection amount is changed to change the fuel injection amount from the stoichiometric air-fuel ratio after the end of the switching control after a predetermined period of time. Has been changed.

  However, when the engine is equipped with a turbocharger, when the combustion mode is switched between the non-supercharged stoichiometric combustion mode and the supercharged lean combustion mode, the boost pressure becomes higher than necessary due to an increase in exhaust energy. Thus, knocking or a torque step occurs at the end of the air-fuel ratio switching control, and drivability deteriorates.

  Therefore, in the internal combustion engine of the present embodiment, the ECU 83 switches the mode when the ignition timing is retarded by changing from the non-supercharged stoichiometric combustion mode (stoichiometric air-fuel ratio) to the supercharged lean combustion mode (lean air-fuel ratio). During control (during air-fuel ratio change control), the ignition timing is retarded while maintaining the stoichiometric air-fuel ratio, the air-fuel ratio is changed to a lean air-fuel ratio after mode switching control, and the ignition timing is advanced. When larger than the predetermined value, the advance amount of the ignition timing in the central spark plugs 81a and 82a is decreased.

  In this embodiment, the air-fuel ratio changing means capable of changing the air-fuel ratio, the ignition timing changing means capable of changing the ignition timing, and the ignition timing changing means when changing from the stoichiometric air-fuel ratio to the lean air-fuel ratio by the air-fuel ratio changing means. Thus, the ECU 83 is applied as a control means for retarding the ignition timing of each spark plug 81a, 81b, 82a, 82b.

  In this case, when changing from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the ECU 83 retards the ignition timing while maintaining the stoichiometric air-fuel ratio during the mode switching control, and sets the lean air-fuel ratio after the mode switching control. In addition, the ignition timing is advanced and the ignition timing of the side spark plugs 81b and 82b is set to MBT. Note that MBT (Minimum advance for Best Torque) is an ignition reference timing at which the engine output and the fuel consumption rate are the best.

  Then, when the ECU 83 changes from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the side spark plugs 81b, 82b with respect to the retard amount of the ignition timing of the central spark plugs 81a, 82a during the mode switching control. The ignition timing retard amount is set small.

  Further, when changing from the supercharged lean combustion mode (lean air-fuel ratio) to the non-supercharged stoichiometric combustion mode (stoichiometric air-fuel ratio), the ECU 83 changes the stoichiometric air-fuel ratio during the mode switching control to retard the ignition timing, When the ignition timing is advanced during the mode switching control and this retardation amount is larger than a predetermined value, the ignition timing of the side spark plugs 81b and 82b is set to MBT.

  In this case, when changing from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode, the ECU 83 sets the side spark plugs 81b, The retard amount of the ignition timing 82b is set small.

  Here, in the V-type 6-cylinder engine of this embodiment described above, the combustion mode switching control will be specifically described based on the flowchart of FIG.

  In the V-type 6-cylinder engine of this embodiment, as shown in FIG. 5, in step S11, the ECU 83 determines whether or not a combustion mode switching request has been issued based on the engine operating state, and switches the combustion mode. If it is determined that there is no request command, this routine is exited without doing anything. On the other hand, if the ECU 83 determines that a command for switching the combustion mode has been issued, the switching request for the combustion mode is a request for switching from the non-supercharging stoichiometric combustion mode to the supercharging lean combustion mode in step S12. Determine if there is.

  If the ECU 83 determines in step S12 that the request is for switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, in step S13, the central spark plugs 81a and 82a and the side The retard amount of the ignition timing of the spark plugs 81b and 82b is calculated. In step S14, the ECU 83 performs ignition timing retard control based on the calculated retard amounts of the center spark plugs 81a and 82a and the side spark plugs 81b and 82b while maintaining the stoichiometric air-fuel ratio. Execute.

  In this case, the ECU 83 sets the retard amount of the ignition timing of the side spark plugs 81b and 82b to be smaller than the retard amount of the ignition timing of the central spark plugs 81a and 82a during the mode switching control. Therefore, during the switching control from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the side spark plugs 81b and 82b first spark with respect to the air-fuel mixture in each combustion chamber 22 and 23, and then the center. Spark plugs 81a and 82a spark, and the occurrence of a torque step is suppressed by suppressing the deterioration of combustion.

  In step S15, the ECU 83 determines whether or not the switching control from the non-supercharging stoichiometric combustion mode to the supercharging lean combustion mode has been completed, for example, whether or not the intake air amount has increased to a predetermined amount. Here, if it is determined that the switching control from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode has not ended, the process returns to step S14 and the process is repeated. On the other hand, if it is determined that the switching control from the non-supercharging stoichiometric combustion mode to the supercharging lean combustion mode is completed. In step S16, ignition timing advance amounts of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b are calculated based on the engine operating state.

  In step S17, it is determined whether or not the calculated advance amount of the ignition timing of the central spark plugs 81a and 82a is greater than a predetermined value set in advance. Here, if it is determined that the advance amount of the ignition timing of the central spark plugs 81a, 82a is larger than the predetermined value, in step S18, the advance amount of the ignition timing in the central spark plugs 81a, 82a is corrected so as to decrease. To do. In step S19, the ECU 83 executes ignition timing advance control based on the calculated advance amounts of the ignition timing of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b. In this case, after the mode switching control, the ECU 83 changes to the lean air-fuel ratio and advances the ignition timing of the ignition timing of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b. While the ignition timing is set to lean MBT, the ignition timing of the central spark plugs 81a and 82a is set to the retard side with respect to the lean MBT, and control is performed so that the advance amount is gradually increased to become lean MBT.

  If it is determined in step S17 that the advance amount of the ignition timing of the central spark plugs 81a, 82a is not greater than the predetermined value, the ECU 83 determines the advance amount of the ignition timing of the central spark plugs 81a, 82a in step S19. Without correction, the ignition timing advance control is executed based on the calculated ignition timing advance amounts of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b. In this case, the ignition timing of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b is set to lean MBT.

  Accordingly, when the ignition timing of the central spark plugs 81a, 82a and the side spark plugs 81b, 82b is advanced after the switching control from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode is completed, the central spark plug 81a, When the amount of advance of the ignition timing of 82a is larger than a predetermined value, the amount of advance of the ignition timing of the central spark plugs 81a, 82a is decreased, so that the air-fuel mixture in each combustion chamber 22, 23 is first The side spark plugs 81b and 82b spark, and then the central spark plugs 81a and 82a spark, thereby suppressing the deterioration of combustion and the occurrence of knocking. Further, after the mode switching control, by changing to a lean air-fuel ratio and setting the ignition timing of the side spark plugs 81b and 82b to lean MBT, combustion deterioration is suppressed and occurrence of knocking and misfire is suppressed.

  On the other hand, if the ECU 83 determines in step S12 that it is not a request for switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the ECU 83 switches from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode in step S20. It is determined whether it is a switching request. If it is determined that the request is for switching from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode, in step S21, the central spark plugs 81a and 82a and the side spark plugs 81b and 82b are based on the engine operating state. The retard amount of the ignition timing is calculated. In step S22, the ECU 83 determines whether or not the calculated retard amount of the ignition timing of the central spark plugs 81a and 82a is larger than a predetermined value set in advance.

  If it is determined in step S22 that the retard amount of the ignition timing of the central spark plugs 81a and 82a is larger than a predetermined value, the retard amount of the ignition timing in the side spark plugs 81b and 82b is decreased in step S23. Correct as follows. In step S24, the ECU 83 executes ignition timing retard control based on the calculated retard amounts of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b. In this case, the ECU 83 changes to the stoichiometric air-fuel ratio at the time of mode switching control and retards the ignition timing of the central spark plugs 81a, 82a and the side spark plugs 81b, 82b, but the side spark plugs 81b, 82b While the ignition timing is set to the stoichiometric MBT, the ignition timing of the central spark plugs 81a and 82a is set to the retard side with respect to the stoichiometric MBT, and control is performed so that the retard amount is gradually decreased to become the stoichiometric MBT.

  If it is determined in step S22 that the retard amount of the ignition timing of the side spark plugs 81b and 82b is not greater than the predetermined value, the ECU 83 determines the retard amount of the ignition timing of the side spark plugs 81b and 82b in step S24. Without correction, ignition timing retardation control is executed based on the calculated ignition timing retardation values of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b. In this case, the ignition timing of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b is set to stoichiometric MBT.

  On the other hand, if it is determined at step S20 that the request is not to switch from the supercharged lean combustion mode to the non-supercharging stoichiometric combustion mode, at step S25, ignition timing retardation control corresponding to the engine operating state is executed.

  Therefore, when switching control from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode is started and the ignition timing of the central spark plugs 81a, 82a and the side spark plugs 81b, 82b is retarded, the side spark plugs 81b, 82b When the retard amount of the ignition timing is greater than a predetermined value, the retard amount of the ignition timing of the side spark plugs 81b, 82b is decreased, so that the air-fuel mixture in each combustion chamber 22, 23 is The spark plugs 81b and 82b spark, and then the central spark plugs 81a and 82a spark, so that the deterioration of combustion is suppressed and the occurrence of knocking is suppressed. Further, during the mode switching control, by changing to the stoichiometric air-fuel ratio and setting the ignition timing of the side spark plugs 81b and 82b to stoichiometric MBT, the deterioration of combustion is suppressed and the occurrence of knocking and misfire is suppressed.

  Here, in the V-type 6-cylinder engine of the present embodiment, the change in the engine operation state accompanying the combustion mode switching control will be specifically described based on the time charts of FIGS. 6 and 7.

  In the V-type 6-cylinder engine of this embodiment, as shown in FIG. 6, when there is a request for switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode at time t1, the throttle opening is increased. By increasing the intake air amount and the fuel injection amount, the stoichiometric air-fuel ratio is maintained, and immediately, the ignition timings of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b are gradually retarded. At this time, by setting the retard amount of the ignition timing of the side spark plugs 81b and 82b to be smaller than the retard amount of the ignition timing of the central spark plugs 81a and 82a during the mode switching control, the in-cylinder temperature abnormality The rise is suppressed and combustion deterioration is suppressed.

  Then, at time t2, the retard of the ignition timing of the central spark plugs 81a, 82a and the side spark plugs 81b, 82b is stopped, the ignition timing is advanced, and the fuel injection amount is decreased, thereby reducing the air-fuel ratio. Is changed to a lean air-fuel ratio, and the combustion mode switching control from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode is completed. At this time, the advance amount of the ignition timing in the central spark plugs 81a and 82a is reduced, and the ignition timing of the side spark plugs 81b and 82b is set to MBT, thereby suppressing combustion deterioration and occurrence of knocking.

  On the other hand, in the V-type 6-cylinder engine of this embodiment, as shown in FIG. 7, when there is a request for switching from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode at time t1, the throttle opening is decreased. Then, by reducing the intake air amount and increasing the fuel injection amount, the air-fuel ratio is changed to the stoichiometric air-fuel ratio, and immediately after the ignition timings of the central spark plugs 81a and 82a and the side spark plugs 81b and 82b are retarded, gradually. Advance to. At this time, the retard amount of the ignition timing of the side spark plugs 81b and 82b is set smaller than the retard amount of the ignition timing of the central spark plugs 81a and 82a during the mode switching control, and the side spark plugs 81b and 82b are set. By setting the ignition timing to stoichiometric MBT, an abnormal rise in the in-cylinder temperature is suppressed and combustion deterioration is suppressed. Then, at time t2, the combustion mode switching control from the supercharged lean combustion mode to the non-supercharging stoichiometric combustion mode is completed.

  As described above, in the internal combustion engine of this embodiment, the turbochargers 66 and 67 capable of compressing the intake air and supplying the compressed air to the combustion chambers 22 and 23 are provided in the V-type 6-cylinder engine. According to the operating state, the combustion mode can be switched from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, and the ECU 83 is in mode switching control when switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode. Retards the ignition timing while maintaining the stoichiometric air-fuel ratio, changes to the lean air-fuel ratio after the mode switching control, and advances the ignition timing. When this advance amount is larger than a predetermined value, the central ignition The advance amount of the ignition timing in the plugs 81a and 82a is reduced.

  Therefore, when the advance amount of the central spark plugs 81a and 82a is larger than a predetermined value at the time of switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, each of the combustion chambers 22 is reduced by reducing the advance amount. , 23, after the side spark plugs 81b and 82b spark, the central spark plugs 81a and 82a spark, thereby preventing deterioration of combustion after the mode switching control and suppressing the occurrence of torque steps. And the occurrence of knocking can be suppressed, and as a result, drivability can be improved.

  At this time, the ECU 83 retards the ignition timing while maintaining the stoichiometric air-fuel ratio during the mode switching control, changes to the lean air-fuel ratio after the mode switching control, and advances the ignition timing, so that the side spark plugs 81b, The ignition timing 82b is set to MBT. Accordingly, the deterioration of the lean combustion after the mode switching control is suppressed, and the occurrence of knocking and misfire can be prevented.

  On the other hand, when changing from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode, the ECU 83 controls the side spark plugs 81b, 82b with respect to the retard amount of the ignition timing of the central spark plugs 81a, 82a during the mode switching control. The ignition timing retard amount is set small. Therefore, the occurrence of torque fluctuation with respect to the retard of the ignition timing is suppressed, and drivability can be improved.

  Further, in the internal combustion engine of the present embodiment, the ECU 83 can switch the combustion mode from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode according to the engine operating state. When switching from the mode to the non-supercharged stoichiometric combustion mode, the ignition timing is retarded by changing to the stoichiometric air-fuel ratio during the mode switching control, the ignition timing is advanced during the mode switching control, and this retardation amount is preset. When it is greater than the predetermined value, the ignition timing of the side spark plugs 81b, 81b is set to MBT.

  Therefore, when the retard amount of the central spark plugs 81a and 82a is larger than a predetermined value when switching from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode, the ignition timing of the side spark plugs 81b and 82b is set to MBT. Thus, the deterioration of the lean combustion after the mode switching control is suppressed, the occurrence of a torque step can be suppressed and the occurrence of knocking can be suppressed, and as a result, drivability can be improved.

  At this time, when changing from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode, the ECU 83 controls the side spark plug with respect to the retard amount of the ignition timing of the central spark plugs 81a and 82a during the mode switching control. The retard amount of the ignition timings 81b and 82b is set small. Therefore, the occurrence of torque fluctuation with respect to the retard of the ignition timing is suppressed, and drivability can be improved.

  In the above-described embodiment, the central ignition plugs 81a and 82a as the central ignition means are provided in the central portion of the combustion chamber 22, that is, the central portions of the intake ports 24 and 25 and the exhaust ports 26 and 27, respectively. Side spark plugs 81b and 82b as means are provided in the periphery of the combustion chamber 22, that is, between one intake port 24 and 25 and one exhaust port 26 and 27, but side spark plug 81b as side ignition means. , 82b may be provided between the other intake ports 24, 25 and the other exhaust ports 26, 27, or both. Further, side ignition plugs 81b and 82b as side ignition means may be provided between the intake ports 24 and 25.

  In the above-described embodiment, the V-type 6-cylinder engine is applied as the internal combustion engine. However, the engine type, the number of cylinders, and the like are not limited to the embodiment.

  As described above, the internal combustion engine according to the present invention can improve the drivability by suppressing the generation of a torque step or the occurrence of knocking when the air-fuel ratio is changed, and is useful for any internal combustion engine. .

1 is a schematic plan view of a V-type 6-cylinder engine that represents an internal combustion engine according to an embodiment of the present invention. It is a schematic sectional drawing of the V type 6 cylinder engine of a present Example. It is a horizontal sectional view of the combustion chamber of the 1st bank in the V type 6 cylinder engine of this example. It is a mode map showing the combustion mode in the V type 6 cylinder engine of a present Example. It is a flowchart showing the combustion mode switching control in the V type 6 cylinder engine of a present Example. It is a time chart showing the engine operating state at the time of switching from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode in the V-type 6-cylinder engine of the present embodiment. It is a time chart showing the engine operating state at the time of switching from the supercharging lean combustion mode to the non-supercharging stoichiometric combustion mode in the V-type 6-cylinder engine of the present embodiment.

Explanation of symbols

12 First bank 13 Second bank 22, 23 Combustion chamber 24, 25 Intake port 26, 27 Exhaust port 28, 29 Intake valve 30, 31 Exhaust valve 51 Intake pipe 53, 54 Intake branch pipe 57 Electronic throttle device 60 First exhaust Pipe 61 Second exhaust pipe 62 First front three-way catalyst 63 Second front three-way catalyst 65 NOx occlusion reduction type catalyst 66, 67 Turbocharger 76, 77 Injector 81a, 82a Central ignition plug (central ignition means)
81b, 82b Side ignition plug (side ignition means)
83 Electronic control unit, ECU (control means, air-fuel ratio changing means, ignition timing changing means)
84 Airflow sensor 86 Supercharging pressure sensor 87 Throttle position sensor 88 Accelerator position sensor 89 Crank angle sensor

Claims (6)

The air-fuel ratio can be changed by a supercharger capable of compressing intake air and supplying it to the combustion chamber, central ignition means provided at the center of the combustion chamber, side ignition means provided at the periphery of the combustion chamber An air-fuel ratio changing means, an ignition timing changing means capable of changing the ignition timing by the central ignition means and the side ignition means, and the ignition timing when the air-fuel ratio changing means changes the stoichiometric air-fuel ratio to a lean air-fuel ratio. In an internal combustion engine comprising a control means for retarding the ignition timing of the central ignition means and the side ignition means by a changing means, the control means changes from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode. , air in ratio changing control is slow the ignition timing while maintaining the stoichiometric air-fuel ratio hidden, the ignition timing based on the engine operating conditions as well as changes to the lean air-fuel ratio after the air-fuel ratio change control proceeds And, this advance when angle amount is greater than a preset predetermined value, an internal combustion engine, characterized in that to reduce the advance amount of the ignition timing in the central ignition means. 2. The internal combustion engine according to claim 1, wherein the control means retards the ignition timing while maintaining the stoichiometric air-fuel ratio during the air-fuel ratio change control when changing from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode. An internal combustion engine characterized by changing to a lean air-fuel ratio after the air-fuel ratio change control and advancing the ignition timing and setting the ignition timing of the side ignition means to MBT. 3. The internal combustion engine according to claim 1, wherein the control means retards the ignition timing of the central ignition means during the air-fuel ratio change control when changing from the non-supercharged stoichiometric combustion mode to the supercharged lean combustion mode. An internal combustion engine characterized in that the retard amount of the ignition timing of the side ignition means is set small with respect to the amount. The air-fuel ratio can be changed by a supercharger capable of compressing intake air and supplying it to the combustion chamber, central ignition means provided at the center of the combustion chamber, side ignition means provided at the periphery of the combustion chamber The air-fuel ratio changing means, the ignition timing changing means capable of changing the ignition timing by the central ignition means and the side ignition means, and the ignition timing when the air-fuel ratio changing means changes the lean air-fuel ratio to the stoichiometric air-fuel ratio. In an internal combustion engine having a control means for retarding the ignition timing of the central ignition means and the side ignition means by a changing means, the control means changes from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode. , the air-fuel ratio switching request retarded ignition timing based on the engine operating state is changed to the stoichiometric air-fuel ratio at the time, when the retard amount of this is greater than a preset predetermined value, the side Set the ignition timing of the fire unit in MBT, the internal combustion engine, characterized in that reducing the retard amount during air-fuel ratio variation control. 5. The internal combustion engine according to claim 4, wherein when the control means changes from the supercharged lean combustion mode to the non-supercharged stoichiometric combustion mode , the control means sets the retard amount of the ignition timing of the central ignition means during the air-fuel ratio change control. On the other hand, an internal combustion engine characterized in that the retard amount of the ignition timing of the side ignition means is set small.   6. The internal combustion engine according to claim 1, wherein the central ignition means is provided on a lower surface of the cylinder head above the center of the combustion chamber, and the side ignition means is provided above the outer periphery of the combustion chamber. An internal combustion engine provided on a lower surface of a cylinder head between an intake port and an exhaust port.

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