JP5776629B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine.

  In the combustion chamber of the internal combustion engine, the air-fuel mixture is ignited in a compressed state. It is known that the ignition timing when the air-fuel mixture is ignited affects the output torque and the fuel consumption. If the ignition timing is advanced, torque can be increased and fuel consumption can be reduced, but abnormal combustion such as knocking occurs at a predetermined ignition timing. It is also known that the compression ratio when the air-fuel mixture is compressed also affects the output torque and fuel consumption. The torque output can be increased by increasing the compression ratio. However, it is known that abnormal combustion occurs when the compression ratio is too high. In the prior art, an internal combustion engine having a variable compression ratio mechanism capable of changing the compression ratio during an operation period is known. In addition to the compression ratio variable mechanism, there is known an internal combustion engine that includes a variable valve timing mechanism formed so that the opening / closing timing of the intake valve can be changed.

  Japanese Patent Laid-Open No. 2006-177176 discloses an internal combustion engine that includes an ignition device that sparks an air-fuel mixture in a combustion chamber, a variable compression ratio mechanism that can change the compression ratio of the engine, and a knocking sensor that detects the occurrence of knocking. It is disclosed. In this internal combustion engine, it is disclosed that the ignition timing is retarded when knocking occurs, and after the ignition timing is retarded, the target compression ratio is lowered and the ignition timing is further advanced.

  Japanese Patent Laid-Open No. 9-242655 discloses an engine ignition method in which the ignition timing of each cylinder of an in-line four-cylinder engine is changed according to the cooling state of each cylinder. The cylinders positioned at both ends of the cylinder block of the in-line four-cylinder engine have a relatively low temperature due to a large area in contact with the coolant. For this reason, the knocking limit of the cylinders at both ends of the cylinder block is increased, and the advance amount of the ignition timing is set large. It is disclosed that the remaining cylinders are set to have a small ignition timing advance amount because the knocking limit is low.

  Japanese Patent Laying-Open No. 2005-2931 discloses an internal combustion engine including a supercharger, a valve timing changing device, and a compression ratio variable mechanism. The internal combustion engine includes an exhaust bypass passage that bypasses the exhaust turbine of the supercharger and an exhaust bypass valve that opens and closes the exhaust bypass passage. In this publication, when the switching from the open side to the closed side by the exhaust bypass valve and the switching from the compression ratio variable mechanism to the low compression ratio side are required simultaneously, the exhaust bypass valve is switched to the closed side. It is disclosed that the occurrence of knocking at the time of transition is suppressed by delaying the start time by a predetermined time.

JP 2006-177176 A JP 2010-196547 A JP 09-242655 A JP 2007-032435 A JP 2005-002931 A International Publication No. 97/13063 Pamphlet

  When knocking occurs during the operation period of the internal combustion engine, the occurrence of knocking can be quickly suppressed by retarding the ignition timing. As disclosed in JP-A-2006-177176, the thermal efficiency can be improved by lowering the mechanical compression ratio and advancing the ignition timing after retarding the ignition timing. However, the mechanical compression ratio of the internal combustion engine has a variation in the mechanical compression ratio for each cylinder. For example, due to manufacturing errors, the dimensions of the combustion chambers of each cylinder vary within tolerances.

  In each cylinder, the volume of the combustion chamber when the piston reaches the top dead center affects the mechanical compression ratio. The variation in the volume of the combustion chamber has a greater effect on the mechanical compression ratio as the mechanical compression ratio increases. For this reason, even if the tolerance is within a predetermined range, the influence of the variation in the volume of the combustion chamber is particularly large in the region where the mechanical compression ratio is high, and as a result, the variation in the mechanical compression ratio between the cylinders is large. It has the characteristic of becoming.

  As disclosed in the above Japanese Patent Application Laid-Open No. 2006-177176, when the ignition timing is advanced to the initial value before retarding after the mechanical compression ratio is lowered, the cylinder with the originally low mechanical compression ratio is used. Even if the ignition timing is advanced to the initial value before retarding, there is a large margin for the limit at which knocking occurs. For this reason, there is room for improvement in thermal efficiency in a cylinder having a low mechanical compression ratio. That is, even if knocking occurs in some cylinders, even if the ignition timing is advanced by a certain amount after lowering the mechanical compression ratio, the knocking will not occur in cylinders with low mechanical compression ratio that are not knocked originally. A sufficient margin remains with respect to the ignition timing at which this occurs, and there is room for improvement.

  An object of the present invention is to provide an internal combustion engine that includes a compression ratio variable mechanism and a variable valve mechanism and that improves thermal efficiency while suppressing the occurrence of abnormal combustion.

  The internal combustion engine of the present invention includes a variable compression ratio mechanism that can change the mechanical compression ratio, a variable valve mechanism that can change the closing timing of the intake valve, and a supercharger that can change the pressure of air supplied to the combustion chamber. A pressure acquisition means for acquiring the pressure of the air supplied to the combustion chamber, and a determination means for determining whether or not abnormal combustion has occurred for each cylinder. When abnormal combustion occurs in at least some of the cylinders, the internal combustion engine retards the ignition timing until the abnormal combustion stops, and then reduces the mechanical compression ratio and advances the ignition timing. It is formed to perform control. In the abnormal combustion suppression control, the ignition timing is advanced so that the advance amount of the ignition timing of the cylinder where the abnormal combustion does not occur is larger than the advance amount of the ignition timing of the cylinder where the abnormal combustion occurs. And a control for advancing the closing timing of the intake valve and lowering the boost pressure when the pressure of the air supplied to the combustion chamber is larger than a predetermined pressure judgment value.

  In the above invention, when the pressure of the air supplied to the combustion chamber is larger than a predetermined pressure judgment value, the advance amount of the intake valve closing timing is increased as the reduction amount of the mechanical compression ratio is larger. Can do.

  In the above invention, when the pressure of the air supplied to the combustion chamber is larger than a predetermined pressure determination value, when the amount of decrease in the mechanical compression ratio is larger than the predetermined compression ratio determination value, the intake valve Advances the valve closing timing and lowers the supercharging pressure, and when the amount of decrease in the mechanical compression ratio is equal to or less than a predetermined compression ratio judgment value, advances the valve closing timing of the intake valve and lowers the supercharging pressure Control can be prohibited.

  In the above invention, the amount of decrease in the mechanical compression ratio can be set based on the retard amount of the ignition timing when the ignition timing is retarded until the abnormal combustion stops.

  In the above invention, when the pressure of the air supplied to the combustion chamber is equal to or lower than a predetermined pressure determination value, it is possible to prohibit the control for advancing the closing timing of the intake valve and lowering the supercharging pressure. .

  According to the present invention, it is possible to provide an internal combustion engine that includes a compression ratio variable mechanism and a variable valve mechanism and that improves thermal efficiency while suppressing the occurrence of abnormal combustion.

1 is a schematic view of an internal combustion engine in an embodiment. It is a general | schematic disassembled perspective view of the compression ratio variable mechanism in embodiment. In the internal combustion engine of the embodiment, it is a schematic cross-sectional view of a cylinder block and a crankcase portion when the mechanical compression ratio is a high compression ratio. In the internal combustion engine of the embodiment, it is a schematic cross-sectional view of a cylinder block and a crankcase portion when the mechanical compression ratio is a low compression ratio. 3 is a graph schematically illustrating overall operation control of the internal combustion engine in the embodiment. It is a graph explaining the variation | change_quantity of the mechanical compression ratio with respect to the mechanical compression ratio in embodiment. It is a graph explaining the change of the ignition timing in the abnormal combustion suppression control of embodiment, and the change of a mechanical compression ratio. It is a graph explaining the relationship between the supercharging pressure of the air supplied to a combustion chamber, and the mechanical compression ratio in which knocking occurs. It is a flowchart of abnormal combustion suppression control in an embodiment. It is a graph explaining the relationship between the intensity | strength of knocking in embodiment, and the fall amount of the mechanical compression ratio in abnormal combustion suppression control. It is a graph explaining the relationship between the fall amount of the mechanical compression ratio in the abnormal combustion suppression control of the embodiment, and the difference in the advance amount of the ignition timing between the knocking occurrence cylinder and the non-knock occurrence cylinder. It is another flowchart of the abnormal combustion suppression control of embodiment. In the abnormal combustion suppression control of the embodiment, is an equivalence line for explaining the relationship between the number of cylinders where knocking has not occurred and the correction amount of the opening degree of the waste gate valve.

  An internal combustion engine according to an embodiment will be described with reference to FIGS. In the present embodiment, an internal combustion engine disposed in a vehicle will be described as an example.

  FIG. 1 is a schematic view of an internal combustion engine in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type. The internal combustion engine includes an engine body 1. The engine body 1 includes a cylinder block 2 and a cylinder head 4. A piston 3 is disposed inside the cylinder block 2. The piston 3 reciprocates inside the cylinder block 2.

  The internal combustion engine in the present embodiment has a plurality of cylinders. The cylinder block 2 is provided with a knock sensor 44 for detecting the occurrence of knocking. The knock sensor 44 of the present embodiment functions as a determination unit that determines whether or not abnormal combustion has occurred for each cylinder. The discriminating means is not limited to this mode, and any device capable of detecting the occurrence of abnormal combustion for each cylinder can be employed.

  The combustion chamber 5 is formed for each cylinder. An engine intake passage and an engine exhaust passage are connected to the combustion chamber 5. An intake port 7 and an exhaust port 9 are formed in the cylinder head 4. The intake valve 6 is disposed at the end of the intake port 7 and is configured to be able to open and close the engine intake passage communicating with the combustion chamber 5. The exhaust valve 8 is disposed at the end of the exhaust port 9 and is configured to be able to open and close the engine exhaust passage communicating with the combustion chamber 5. A spark plug 10 as an ignition device is fixed to the cylinder head 4. The spark plug 10 is formed to ignite fuel in the combustion chamber 5.

  The internal combustion engine in the present embodiment includes a fuel injection valve 11 for supplying fuel to the combustion chamber 5. The fuel injection valve 11 in the present embodiment is arranged so as to inject fuel into the intake port 7. The fuel injection valve 11 is not limited to this configuration, and may be arranged so that fuel can be supplied to the combustion chamber 5. For example, the fuel injection valve may be arranged to inject fuel directly into the combustion chamber. The fuel injection valve 11 is connected to the fuel tank 28 via an electronically controlled fuel pump 29 with variable discharge amount. The fuel stored in the fuel tank 28 is supplied to the fuel injection valve 11 by the fuel pump 29.

  The internal combustion engine in the present embodiment includes an exhaust turbocharger 55 as a supercharger. The exhaust turbocharger 55 is disposed in the engine exhaust passage and includes an exhaust turbine 56 in which an internal turbine wheel is rotated by an exhaust flow. The exhaust turbocharger 55 includes a compressor 57 that is disposed in the engine intake passage and pressurizes intake air.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a corresponding intake branch pipe 13. The surge tank 14 is connected to the outlet portion of the compressor 57 of the exhaust turbocharger 55 via the intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed inside the intake pipe 15 that connects the surge tank 14 and the compressor 57. A cooler 60 for cooling the intake air is disposed in the middle of the intake pipe 15.

  The inlet portion of the compressor 57 is connected to the air cleaner 54 via the intake pipe 15. An air flow meter 16 that detects the amount of intake air is disposed inside the intake pipe 15 upstream of the compressor 57.

  On the other hand, the exhaust port 9 of each cylinder is connected to the inlet portion of the exhaust turbine 56 of the exhaust turbocharger 55 via the corresponding exhaust branch pipe 19 and the exhaust pipe 23. An outlet portion of the exhaust turbine 56 is connected to the exhaust treatment device 21 via the exhaust pipe 22. The exhaust treatment device 21 in the present embodiment includes a three-way catalyst 20. The exhaust treatment device 21 is not limited to this form, and any device that purifies exhaust gas can be employed.

  A bypass passage 58 that bypasses the exhaust turbine 56 is disposed between the exhaust pipe 23 upstream of the exhaust turbine 56 and the exhaust pipe 22 downstream of the exhaust turbine 56. A waste gate valve (WGV) 59 as a bypass valve that opens and closes the bypass passage 58 is disposed in the bypass passage 58. The supercharging pressure increases as the rotational speed of the exhaust turbocharger 55 increases. However, if the supercharging pressure becomes too high, there is a risk of damage. The wastegate valve 59 is controlled so that the opening degree is increased, for example, when the pressure in the intake pipe 15 downstream of the compressor 57 is higher than a predetermined pressure. It is possible to control so that the pressure of the intake air supplied to the combustion chamber 5 does not exceed a predetermined pressure.

  The supercharger in the present embodiment is formed so that the pressure of the air supplied to the combustion chamber 5 can be changed. The wastegate valve 59 in the present embodiment is formed so that the opening degree can be adjusted. By adjusting the opening degree of the wastegate valve 59, the flow rate of the exhaust gas flowing through the bypass passage 58 can be adjusted, and the rotational speed of the exhaust turbocharger 55 can be adjusted. As a result, the supercharging pressure supplied to the combustion chamber 5 can be adjusted. The supercharger in the present embodiment is formed so that the pressure of the air supplied to the combustion chamber can be changed by adjusting the exhaust gas flow rate that bypasses the exhaust turbine. It is possible to employ a supercharger equipped with an arbitrary mechanism capable of changing the above.

  The internal combustion engine in the present embodiment includes pressure acquisition means for acquiring the pressure of air supplied to the combustion chamber 5, that is, the supercharging pressure. The pressure acquisition means in the present embodiment includes a supercharging pressure sensor 45 as a pressure detector. The supercharging pressure sensor 45 in the present embodiment is disposed downstream of the throttle valve 18 in the intake pipe 15. The pressure acquisition means for acquiring the supercharging pressure is not limited to this form, and any device capable of acquiring the pressure of the air supplied to the combustion chamber can be employed. For example, the pressure acquisition means may be a device that estimates the pressure of air supplied to the combustion chamber from the operating state of the internal combustion engine.

  The internal combustion engine in the present embodiment includes an electronic control unit 31. The electronic control unit 31 in the present embodiment includes a digital computer. The electronic control unit 31 includes a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU (microprocessor) 35, an input port 36 and an output port 37 which are connected to each other via a bidirectional bus 32. Including.

  The output signal of the air flow meter 16 is input to the input port 36 via the corresponding AD converter 38. A load sensor 41 is connected to the accelerator pedal 40. The load sensor 41 generates an output voltage proportional to the depression amount of the accelerator pedal 40. This output voltage is input to the input port 36 via the corresponding AD converter 38.

  The crank angle sensor 42 generates an output pulse each time the crankshaft rotates, for example, a predetermined angle, and this output pulse is input to the input port 36. The engine speed can be detected from the output of the crank angle sensor 42. Further, the crank angle can be detected from the output of the crank angle sensor 42. The output of knock sensor 44 and the output of supercharging pressure sensor 45 are input to input port 36 via corresponding AD converters 38. In the engine exhaust passage, a temperature sensor 43 that detects the temperature of the exhaust treatment device 21 is disposed downstream of the exhaust treatment device 21. The output of the temperature sensor 43 is input to the input port 36 via the corresponding AD converter 38.

  The output port 37 of the electronic control unit 31 is connected to the fuel injection valve 11 and the spark plug 10 via the corresponding drive circuits 39. The electronic control unit 31 in the present embodiment is formed to perform fuel injection control and ignition control. The ignition timing of the spark plug 10 is controlled by the electronic control unit 31. The output port 37 is connected to the step motor 17 that drives the throttle valve 18, the fuel pump 29, and the waste gate valve 59 via a corresponding drive circuit 39. These devices are controlled by the electronic control unit 31.

  The intake valve 6 is formed to open and close as the intake cam 51 rotates. The exhaust valve 8 is formed to open and close as the exhaust cam 52 rotates. The internal combustion engine in the present embodiment includes a variable valve mechanism. The variable valve mechanism includes a variable valve timing device 53 that changes the opening / closing timing of the intake valve 6. The variable valve timing device 53 in the present embodiment is connected to the rotation shaft of the intake cam 51. The variable valve timing device 53 is controlled by the electronic control unit 31.

  The variable valve timing device according to the present embodiment is configured such that the operating angle from when the valve starts to open until it closes is substantially constant, and the phase at the center of the operating angle can be changed. The variable valve timing device is not limited to this form, and the operating angle may be variably formed. In addition, any variable valve timing device that can change the valve closing timing of the intake valve can be employed.

  The internal combustion engine in the present embodiment includes a variable compression ratio mechanism. In the present invention, the space in the cylinder surrounded by the crown surface of the piston and the cylinder head when the piston reaches compression top dead center is referred to as a combustion chamber. The compression ratio of the internal combustion engine is determined depending on the volume of the combustion chamber and the like. The variable compression ratio mechanism in the present embodiment is formed to change the compression ratio by changing the volume of the combustion chamber. The actual compression ratio, which is the actual compression ratio in the combustion chamber, is represented by (actual compression ratio) = (combustion chamber volume + volume that the piston moves while the intake valve is closed) / (combustion chamber volume). .

  FIG. 2 is an exploded perspective view of the compression ratio variable mechanism of the internal combustion engine in the present embodiment. FIG. 3 is a first schematic cross-sectional view of the combustion chamber portion of the internal combustion engine. FIG. 3 is a schematic diagram when a high compression ratio is obtained by the variable compression ratio mechanism. In the internal combustion engine in the present embodiment, the lower structure including the crankcase and the cylinder block arranged on the upper side of the lower structure move relative to each other. The substructure in the present embodiment supports the cylinder block via a compression ratio variable mechanism. Further, the lower structure in the present embodiment supports the crankshaft.

  2 and 3, a plurality of protrusions 80 are formed below the side walls on both sides of the cylinder block 2. The protrusion 80 is formed with a cam insertion hole 81 having a circular cross section. A plurality of protrusions 82 are formed on the upper wall of the crankcase 79. The protrusion 82 is formed with a cam insertion hole 83 having a circular cross-sectional shape. The protrusion 82 of the crankcase 79 is fitted between the protrusions 80 of the cylinder block 2.

  The compression ratio variable mechanism in the present embodiment includes a pair of camshafts 84 and 85 as support shafts for the cylinder block. A circular cam 88 that is rotatably inserted into each cam insertion hole 83 is fixed to the cam shafts 84 and 85. The circular cam 88 is arranged coaxially with the rotation axis of each camshaft 84, 85. On the other hand, eccentric shafts 87 arranged eccentrically with respect to the rotation axis of the cam shafts 84 and 85 extend on both sides of each circular cam 88. On the eccentric shaft 87, another circular cam 86 is eccentrically attached to be rotatable. These circular cams 86 are arranged on both sides of the circular cam 88. The circular cam 86 is rotatably inserted into the corresponding cam insertion hole 81.

  The compression ratio variable mechanism includes a motor 89. Two worm gears 91 and 92 having spiral directions opposite to each other are attached to the rotating shaft 90 of the motor 89. Gears 93 and 94 are fixed to the end portions of the camshafts 84 and 85, respectively. The gears 93 and 94 are arranged so as to mesh with the worm gears 91 and 92. When the motor 89 rotates the rotating shaft 90, the camshafts 84 and 85 can be rotated in directions opposite to each other.

  Referring to FIG. 3, when the circular cams 88 arranged on the respective camshafts 84 and 85 are rotated in opposite directions as indicated by arrows 97, the eccentric shaft 87 faces the upper end of the circular cam 88. Moving. The circular cam 86 rotates in the opposite direction to the circular cam 88 as indicated by an arrow 96 in the cam insertion hole 81.

  FIG. 4 shows a second schematic cross-sectional view of the combustion chamber portion of the internal combustion engine in the present embodiment. FIG. 4 is a schematic diagram when a low compression ratio is achieved by the compression ratio variable mechanism. As shown in FIG. 4, when the eccentric shaft 87 moves to the upper end of the circular cam 88, the central axis of the circular cam 88 moves below the eccentric shaft 87. Referring to FIGS. 3 and 4, the relative position between crankcase 79 and cylinder block 2 is determined by the distance between the central axis of circular cam 86 and the central axis of circular cam 88. The cylinder block 2 moves away from the crankcase 79 as the distance between the central axis of the circular cam 86 and the central axis of the circular cam 88 increases. As the cylinder block 2 moves away from the crankcase 79 as indicated by an arrow 98, the volume of the combustion chamber 5 when the piston 3 reaches the compression top dead center increases.

  In the variable compression ratio mechanism in the present embodiment, the volume of the combustion chamber is variably formed by moving the cylinder block relative to the crankcase. In the present embodiment, the compression ratio determined only from the stroke volume of the piston from the bottom dead center to the top dead center and the volume of the combustion chamber is referred to as a mechanical compression ratio. That is, the mechanical compression ratio is represented by (mechanical compression ratio) = (combustion chamber volume + piston stroke volume from bottom dead center to top dead center) / (combustion chamber volume).

  In FIG. 3, the piston 3 has reached the compression top dead center, and the volume of the combustion chamber 5 is reduced. When the intake air amount is always constant, the compression ratio becomes high. This state is a state where the mechanical compression ratio is high. On the other hand, in FIG. 4, the piston 3 reaches the compression top dead center, and the volume of the combustion chamber 5 is increased. When the intake air amount is always constant, the compression ratio becomes low. This state is a state where the mechanical compression ratio is low. Thus, the internal combustion engine in the present embodiment can change the compression ratio during the operation period. For example, the compression ratio can be changed by a variable compression ratio mechanism according to the operating state of the internal combustion engine.

  The variable compression ratio mechanism according to the present embodiment moves the cylinder block relative to the crankcase by rotating a circular cam having an eccentric rotation shaft. Any variable compression ratio mechanism capable of changing the mechanical compression ratio by the mechanism can be employed.

  An internal combustion engine generally has a lower thermal efficiency as the engine load is lower. Therefore, in order to improve the thermal efficiency during operation of the internal combustion engine, it is preferable to improve the thermal efficiency when the load is low. Thermal efficiency can be improved by increasing the compression ratio with the variable compression ratio mechanism in the present embodiment. In particular, when the compression ratio is increased, the expansion ratio when the piston moves from the top dead center to the bottom dead center is increased, so that the thermal efficiency is improved. However, when the compression ratio is increased by the compression ratio variable mechanism, abnormal combustion such as knocking occurs at a predetermined compression ratio.

  The internal combustion engine in the present embodiment includes a variable valve timing device as a variable valve mechanism, and the intake valve opening and closing timing is variably formed. By delaying the timing of closing the intake valve, the amount of air flowing into the combustion chamber can be reduced. That is, by delaying the timing for closing the intake valve, the actual compression ratio when the air-fuel mixture is compressed in the combustion chamber can be reduced.

  FIG. 5 is a graph schematically illustrating the overall operation control of the internal combustion engine in the present embodiment. FIG. 5 shows the mechanical compression ratio with respect to the load and the timing for closing the intake valve. In the internal combustion engine of the present embodiment, the air-fuel ratio at the time of combustion is such that unburned hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas can be simultaneously purified by the three-way catalyst of the exhaust purification device. The theoretical air-fuel ratio is controlled.

  The internal combustion engine in the present embodiment is controlled such that the mechanical compression ratio is lowered by a variable compression ratio mechanism when the load is high. That is, it is possible to suppress the occurrence of abnormal combustion by controlling so that the volume of the combustion chamber is increased when the piston reaches compression top dead center. In addition, when the load is high, the timing of closing the intake valve is advanced by the variable valve mechanism to increase the amount of intake air taken into the combustion chamber. In the internal combustion engine in the present embodiment, the throttle valve is held fully open when the load is high. For this reason, the pumping loss can be made substantially zero.

  In the internal combustion engine of the present embodiment, when the load becomes small as indicated by an arrow 61, the variable valve mechanism controls the intake valve closing timing late in order to reduce the intake air amount. In the region where the intake valve closing timing is changed late, the mechanical compression ratio is increased by the variable compression ratio mechanism. By this control, the actual compression ratio in the combustion chamber can be kept substantially constant. It can be controlled that the actual compression ratio becomes high and abnormal combustion occurs. Even in the region where the load is reduced, the throttle valve is kept fully open, and the pumping loss can be made substantially zero. Furthermore, the internal combustion engine of the present embodiment can improve the thermal efficiency because the expansion ratio remains large even when the intake valve is closed late. The internal combustion engine in the present embodiment can improve the thermal efficiency by increasing the expansion ratio at low loads while maintaining the actual compression ratio in the combustion chamber below the compression ratio at which abnormal combustion occurs.

  In the internal combustion engine in the present embodiment, when the load is further reduced and reaches a load L1 that is slightly lower, the limit mechanical compression ratio that becomes the limit of the compression ratio change on the structure of the compression ratio variable mechanism is reached. To do. For this reason, in the region lower than the load L1, the mechanical compression ratio is maintained at the limit mechanical compression ratio.

  Further, in the embodiment shown in FIG. 5, when the load L1 is reduced, the closing timing of the intake valve becomes the limit closing timing at which the amount of intake air supplied to the combustion chamber can be controlled. For this reason, in the region where the load is lower than the load L1, the closing timing of the intake valve is held at the limit closing timing. In the internal combustion engine of the present embodiment, the amount of intake air taken into the combustion chamber is controlled by the throttle valve in a region lower than the load L1. That is, in the region lower than the load L1, the throttle valve opening can be controlled to be smaller as the load is lower.

  Thus, the internal combustion engine in the present embodiment can improve the thermal efficiency by using a combination of the compression ratio variable mechanism and the variable valve mechanism. By the way, the internal combustion engine of the present embodiment performs abnormal combustion suppression control that suppresses the occurrence of abnormal combustion when abnormal combustion occurs during the operation period. Abnormal combustion in the present embodiment includes, for example, a knocking phenomenon.

  FIG. 6 shows a graph for explaining the variation amount of the mechanical compression ratio with respect to the mechanical compression ratio of the internal combustion engine in the present embodiment. Internal combustion engines have dimensional variations within tolerances during manufacturing. Each cylinder has a manufacturing error. The size of the combustion chamber also varies in size, and as a result, the mechanical compression ratio also varies. The vertical axis in FIG. 6 indicates the amount of variation in the mechanical compression ratio, and the point where the amount of variation is 0 indicates that it is as designed. The horizontal axis represents the mechanical compression ratio ε.

  In the region where the mechanical compression ratio is small, as shown by the arrow 100a, the amount of variation in the mechanical compression ratio due to the dimensional tolerance is small. For this reason, the error of the actual mechanical compression ratio with respect to the target mechanical compression ratio is small. On the other hand, when the mechanical compression ratio increases, the amount of variation in the mechanical compression ratio also increases as indicated by arrows 100b and 100c. That is, as the mechanical compression ratio increases, the amount of variation in the mechanical compression ratio in each cylinder also increases. The internal combustion engine of the present embodiment includes a compression ratio variable mechanism, and the mechanical compression ratio is increased. The influence of variations in the mechanical compression ratio between the cylinders also increases. For this reason, in the abnormal combustion suppression control of the present embodiment, control is performed in consideration of variations in the mechanical compression ratio among the plurality of cylinders.

  FIG. 7 shows a graph for explaining a part of the abnormal combustion suppression control in the present embodiment. The horizontal axis is the mechanical compression ratio, and the vertical axis is the ignition timing. The graph shows cylinder A and cylinder B among the plurality of cylinders of the internal combustion engine. In the example, the mechanical compression ratio of the cylinder B is larger than the mechanical compression ratio of the cylinder A due to the influence of the manufacturing error.

  In the graph of FIG. 7, knocking occurs when the ignition timing is on the advance side of the knocking limit line. When the ignition timing is retarded from the knock limit line, knocking is suppressed. That is, it is a state in which knocking has not occurred. The state A1 of the cylinder A and the state B1 of the cylinder B indicate the current operation state. In the state A1 of the cylinder A, since the ignition timing is positioned on the retard side with respect to the knocking limit line, the cylinder A is in a state where knocking has not occurred and knocking has not occurred. On the other hand, in the state B1 of the cylinder B, knocking occurs because the ignition timing is located on the advance side of the knock limit line. That is, the cylinder B is a knocking cylinder.

  In the internal combustion engine in the present embodiment, the cylinder B can be detected as a knocking occurrence cylinder and the cylinder A can be detected as a non-knocking occurrence cylinder based on the output of the knock sensor 44 attached to the engine body 1.

  In the abnormal combustion suppression control of the present embodiment, the ignition timing is retarded when the occurrence of knocking is detected. In the cylinder B, the state B1 is shifted to the state B2 on the retard side of the knock limit line. Knocking is stopped by retarding the ignition timing to state B2. In the cylinder A, the state A1 is shifted to the state A2.

  Next, in the abnormal combustion suppression control of the present embodiment, control for lowering the mechanical compression ratio and control for advancing the ignition timing are performed. By reducing the mechanical compression ratio, it is possible to shift to a state in which knocking is suppressed. By reducing the mechanical compression ratio, there is a margin of ignition timing with respect to the knock limit line. For this reason, the ignition timing can be advanced. For example, the ignition timing can be advanced to almost the knocking limit or close to the knocking limit. By performing this control, the thermal efficiency can be improved.

  In the cylinder B that is the knocking occurrence cylinder, the state is shifted from the state B2 to the state B3 by lowering the mechanical compression ratio. In the cylinder A that is not knocked, the state A2 is shifted to the state A3. After that, by advancing the ignition timing, the cylinder B shifts from the state B3 to the state B4. In the cylinder B, the ignition timing is advanced to the vicinity of the knocking limit that is later than the knocking limit.

  By the way, when the ignition timing of the cylinder A is advanced by the same advance amount as that of the cylinder B, the state A3 is shifted to the state A4 '. However, as shown in FIG. 7, the cylinder A is originally a cylinder in which knocking has not occurred. In the state A4 'of the cylinder A, a large ignition timing margin with respect to the knocking limit line remains. In the internal combustion engine of the present embodiment, control is performed to further advance the ignition timing in a cylinder where knocking has not occurred. In the cylinder A, the ignition timing is advanced from the state A4 'to the state A4. State A4 is a timing in the vicinity of the knocking limit whose ignition timing is later than the knocking limit.

  Thus, when the internal combustion engine includes the first cylinder and the second cylinder and the actual mechanical compression ratio is higher in the second cylinder than in the first cylinder, the ignition timing of the first cylinder is advanced. The angular amount can be controlled to be larger than the advance amount of the ignition timing of the second cylinder. In particular, in the present embodiment, the ignition timing is advanced so that the advance amount of the ignition timing of the cylinder in which knocking has not occurred is larger than the advance amount of the ignition timing of the cylinder in which knocking has occurred. Control to make the corner. By performing this control, even when the mechanical compression ratio varies between cylinders due to manufacturing errors or the like, the ignition timing can be advanced to the vicinity of the knocking limit for each cylinder. The thermal efficiency in each cylinder can be improved, and as a result, the thermal efficiency of the entire internal combustion engine can be improved.

  In the combustion suppression control of the present embodiment, when knocking occurs in at least some of the cylinders, the ignition timing is retarded until knocking stops, and then the mechanical compression ratio is lowered and the ignition timing is advanced. Control is performed. That is, the mechanical compression ratio is corrected and the ignition timing is corrected. When abnormal combustion is occurring in all the cylinders, the advance amount of the ignition timing can be made substantially the same for all the cylinders. Further, the reduction of the mechanical compression ratio and the advance of the ignition timing may be performed simultaneously.

  By the way, with reference to FIG. 1, the internal combustion engine in the present embodiment includes an exhaust turbocharger 55 as a supercharger. The internal combustion engine has a characteristic that the knocking sensitivity increases as the pressure of the air supplied to the combustion chamber 5 increases. That is, when the supercharging pressure increases, the frequency of occurrence of knocking increases or the strength of vibration when knocking occurs increases.

  FIG. 8 shows a graph for explaining the relationship between the supercharging pressure and the mechanical compression ratio at which knocking occurs. In FIG. 8, the engine speed, the load, the closing timing of the intake valve, and the like are under constant conditions. The higher the supercharging pressure, the lower the mechanical compression ratio at which knocking occurs. That is, it can be seen that knocking is more likely to occur and the sensitivity of knocking increases as the boost pressure increases.

  During the operation period of the internal combustion engine, even if the correction of the mechanical compression ratio and the correction of the ignition timing are performed, the correction accuracy of the mechanical compression ratio, etc., or the variation of other variables, etc. The possibility of sporadic knocking remains. In particular, in a region where the supercharging pressure is high, the knocking sensitivity is increased, so that the possibility of knocking sporadic increases.

  For this reason, in the abnormal combustion suppression control of the present embodiment, when the supercharging pressure is larger than a predetermined pressure determination value, in addition to the control of the mechanical compression ratio and the control of the ignition timing, In order to suppress the occurrence of knocking, control is performed to further reduce the supercharging pressure and advance the closing timing of the intake valve. On the other hand, when the supercharging pressure is equal to or lower than a predetermined pressure determination value, control for reducing the supercharging pressure and advancing the closing timing of the intake valve is prohibited.

  By reducing the supercharging pressure, the temperature of the air flowing into the combustion chamber can be reduced and knocking can be suppressed. Referring to FIG. 1, in the internal combustion engine of the present embodiment, the boost pressure can be reduced by increasing the opening degree of waste gate valve 59. By increasing the opening degree of the waste gate valve 59, the exhaust gas flow rate that bypasses the exhaust turbine 56 increases. For this reason, the flow rate of the exhaust gas flowing into the exhaust turbine 56 decreases, and the rotational speed of the exhaust turbocharger 55 decreases. As a result, the pressure of the intake air pressurized by the compressor 57 can be reduced.

  However, the charging efficiency in the combustion chamber decreases due to the decrease in supercharging pressure. As a result, the output torque varies. Therefore, in the present embodiment, a decrease in charging efficiency in the combustion chamber is suppressed by advancing the closing timing of the intake valve as the supercharging pressure decreases. Referring to FIG. 5, the closing timing of the intake valve of the present embodiment is after the timing when the piston is located at the bottom dead center. That is, the intake valve is closed while the piston is rising. By advancing the valve closing timing of the intake valve, the amount of air flowing into the combustion chamber can be increased, and the charging efficiency can be increased. In the present embodiment, the closing timing of the intake valve is advanced so that the charging efficiency is the same before and after the decrease in supercharging pressure. With this control, torque fluctuations can be suppressed.

  Further, by advancing the closing timing of the intake valve, the volume of the space in the cylinder from the crown surface of the piston to the upper surface of the combustion chamber when the intake valve is closed increases. When the same amount of air is charged into the combustion chamber, the cylinder pressure when the intake valve is closed can be increased by lowering the boost pressure and advancing the closing timing of the intake valve. Thus, an error in the intake air amount can be suppressed. In other words, when the closing timing of the intake valve is set to the retard side, the sensitivity to variations in the intake air amount becomes higher than when the intake valve is set to the advance side. For this reason, the intake air amount error can be reduced by advancing the closing timing of the intake valve.

  Next, examples of abnormal combustion suppression control in the present embodiment will be described. FIG. 9 shows a flowchart of abnormal combustion suppression control in the present embodiment. The control shown in FIG. 9 can be performed repeatedly at predetermined time intervals, for example. In addition, the determination value of each control can be set by reading a map or the like stored in advance in the electronic control unit.

  In step 111, the occurrence of knocking is detected for each cylinder. It is determined whether each cylinder is a knocking occurrence cylinder or a non-knocking occurrence cylinder. Further, the knocking intensity is also detected in the knocking cylinder. In the present embodiment, the knocking intensity can be detected by the output of knock sensor 44.

  Next, in step 112, the ignition timing is retarded. In the present embodiment, referring to FIG. 7, the ignition timing is retarded until knocking stops in the knocking cylinder. The retard amount of the ignition timing at this time can be stored in the electronic control unit.

  Next, in step 113, a reduction amount εm (absolute value) of the mechanical compression ratio is set. That is, an amount for reducing the mechanical compression ratio is set. FIG. 10 shows a graph of the relationship between the knocking strength and the amount of decrease in the mechanical compression ratio in the present embodiment. The horizontal axis indicates the knocking strength. As the knocking strength, for example, the strength (amplitude, etc.) of vibration when knocking occurs can be exemplified. As the knocking intensity detected by the knock sensor increases, the reduction amount of the mechanical compression ratio can be set larger. In this way, the amount of decrease in the mechanical compression ratio can be set based on the knocking strength.

  Alternatively, the amount of decrease in the mechanical compression ratio may be set based on the retard amount of the ignition timing. For example, the reduction amount of the mechanical compression ratio can be set larger as the retard amount of the ignition timing until knocking stops is larger.

  In step 114, the mechanical compression ratio is reduced based on the set reduction amount of the mechanical compression ratio.

  Next, in step 115, the advance amount of the ignition timing is set for each cylinder. In the present embodiment, a plurality of cylinders are classified into knock generation cylinders and knock non-generation cylinders, and the advance amount of the ignition timing is set for each cylinder. The advance amount of the ignition timing of the knocking cylinder can be set based on, for example, the retard amount when the ignition timing is retarded in step 112 and the reduction amount of the mechanical compression ratio. On the other hand, the advance amount of the ignition timing of the non-knocked cylinder can be set by adding a predetermined amount to the advance amount of the ignition timing of the knocked cylinder.

  FIG. 11 is a graph for explaining the amount of decrease in the mechanical compression ratio and the difference in the advance amount of the ignition timing between the knocking occurrence cylinder and the non-knocking occurrence cylinder. The vertical axis represents the value obtained by subtracting the advance amount of the knocking cylinder from the advance amount of the cylinder where knocking has not occurred. The larger the amount of decrease in the mechanical compression ratio, the larger the difference in the advance amount of the ignition timing. By setting the difference in the advance amount of the ignition timing based on the amount of decrease in the mechanical compression ratio and adding the difference in the advance amount of the ignition timing to the advance amount of the ignition timing of the knocking cylinder, no knocking occurs The advance amount of the ignition timing of the cylinder can be set.

  Referring to FIG. 9, next, in step 116, the ignition timing is advanced based on the advance amount of the ignition timing set for each cylinder. Here, in step 116, if knocking occurs in any of the cylinders during the period in which the ignition timing is advanced, control is performed to stop the ignition timing advance in the cylinder in which knocking has occurred. It doesn't matter.

  Alternatively, in setting the advance amount of the ignition timing of the cylinder where knocking has not occurred, for example, the advance of the ignition timing is stopped at the ignition timing MBT (Minimum advance for Best Torque) at which the internal combustion engine generates the maximum torque. It doesn't matter. For example, when a means for detecting the ignition timing MBT is arranged in the internal combustion engine, the advance amount can be set so that the ignition timing MBT is reached by the advance of the ignition timing.

  The means for estimating the ignition timing MBT includes, for example, a torque sensor that can detect the output torque. A magnetostrictive torque sensor can be disposed on the crankshaft of the internal combustion engine. The point at which the ignition timing is advanced with time and the torque starts to decrease after increasing can be determined as the ignition timing MBT. Alternatively, the ignition timing MBT may be detected by an in-cylinder pressure sensor that can detect the pressure inside the combustion chamber. When the means for estimating the ignition timing MBT includes an in-cylinder pressure sensor, the output torque can be estimated by integrating the pressure changing in time series. The timing at which the estimated torque becomes maximum can be determined as the ignition timing MBT by gradually advancing the ignition timing.

  Next, control is performed to lower the supercharging pressure and advance the closing timing (IVC) of the intake valve. First, in step 117 to step 119, it is determined whether or not control is performed to lower the supercharging pressure and advance the closing timing of the intake valve. In step 117, the pressure of the air supplied to the combustion chamber, that is, the supercharging pressure is detected. With reference to FIG. 1, the supercharging pressure can be detected by a supercharging pressure sensor 45.

  Next, in step 118, it is determined whether or not the detected supercharging pressure is greater than a predetermined pressure determination value. As the pressure determination value, a value that is a function of the operating state of the internal combustion engine such as the engine speed and load can be set in advance and stored in the electronic control unit. When the detected supercharging pressure is greater than a predetermined pressure determination value, it can be determined that there is a risk of knocking. In this case, the process proceeds to step 119. On the other hand, when the detected supercharging pressure is equal to or lower than a predetermined pressure determination value, this control is terminated. That is, the control for advancing the closing timing of the intake valve and lowering the supercharging pressure is prohibited.

  In step 119, it is determined whether or not the reduction amount of the mechanical compression ratio is larger than a predetermined compression ratio determination value. In the abnormal combustion suppression control in the present embodiment, when the amount of decrease (absolute value) of the mechanical compression ratio is larger than a predetermined compression ratio determination value, the intake valve closing timing is advanced and supercharging is performed. Control to reduce the pressure. On the other hand, when the amount of decrease (absolute value) of the mechanical compression ratio is equal to or smaller than a predetermined compression ratio determination value, control for advancing the closing timing of the intake valve and lowering the supercharging pressure is prohibited. As the predetermined compression ratio determination value, a determination value for determining whether or not the amount of decrease in the mechanical compression ratio is within the range of the normal design tolerance can be adopted. For example, within the normal design tolerance range, it is possible to prohibit the control for advancing the closing timing of the intake valve and lowering the supercharging pressure.

  In step 119, when the amount of decrease in the mechanical compression ratio is equal to or smaller than a predetermined compression ratio determination value, this control is terminated. If the amount of decrease in the mechanical compression ratio is larger than the predetermined compression ratio determination value in step 119, the process proceeds to step 120.

  In step 120, the advance amount of the intake valve closing timing and the reduction amount of the supercharging pressure are set. In the present embodiment, the advance amount of the intake valve closing timing can be increased as the amount of decrease in the mechanical compression ratio increases. Moreover, the amount of decrease in supercharging pressure can be increased as the amount of decrease in mechanical compression ratio increases. Alternatively, in step 120, a predetermined amount of decrease in the boost pressure and a predetermined amount of advance amount of the closing timing of the intake valve may be employed.

  In step 121, the valve closing timing of the intake valve is advanced based on the set amount of advancement of the valve closing timing of the intake valve, and the boost pressure is reduced based on the set amount of decrease in the boost pressure.

  The abnormal combustion suppression control in the present embodiment reduces the supercharging pressure when the valve closing timing of the intake valve is advanced. As a result, the pump work due to supercharging is reduced and the fuel consumption is deteriorated. For this reason, it is preferable that the closing timing of the intake valve be delayed and not advanced as much as possible. That is, the larger the advance amount of the intake valve closing timing and the lowering amount of the supercharging pressure, the more reliably the knocking can be suppressed. In order to suppress the deterioration of the fuel consumption that occurs at this time, The valve is preferably closed late.

  In the present embodiment, when the pressure of the air supplied to the combustion chamber is larger than a predetermined pressure determination value, control is performed to advance the closing timing of the intake valve and lower the supercharging pressure. However, when the pressure of the air supplied to the combustion chamber is equal to or less than a predetermined pressure determination value, control for advancing the closing timing of the intake valve and lowering the supercharging pressure is prohibited. By performing this control, only when there is a high possibility of knocking, the intake valve closing timing can be advanced and the supercharging pressure can be reduced, thereby suppressing deterioration in fuel consumption. it can.

  Also, the greater the amount of decrease in the mechanical compression ratio, the greater the change in the operating state of the internal combustion engine, so the possibility of knocking increases. In this embodiment, the amount of advancement of the closing timing of the intake valve is increased by performing control to increase the amount of advancement of the closing timing of the intake valve as the amount of decrease in the mechanical compression ratio is larger. Knocking can be effectively suppressed while avoiding. Furthermore, in the present embodiment, only when the amount of decrease in the mechanical compression ratio is larger than a predetermined compression ratio determination value, the closing timing of the intake valve is advanced and the supercharging pressure is decreased. . When the reduction amount of the mechanical compression ratio is equal to or less than a predetermined compression ratio determination value, it is possible to suppress the deterioration of the fuel consumption by performing the control for delaying the closing timing of the intake valve.

  Thus, in the present embodiment, knocking can be suppressed by changing the boost pressure and the closing timing of the intake valve in addition to changing the ignition timing and changing the mechanical compression ratio.

  By the way, the abnormal combustion suppression control of the present embodiment includes control for reducing the mechanical compression ratio. By changing the mechanical compression ratio, the energy of the exhaust gas flowing out from the combustion chamber changes, and as a result, the supercharging pressure changes. Here, when knocking has occurred in all the cylinders of the internal combustion engine, the energy of the exhaust gas discharged from all the cylinders becomes almost equal in order to match the mechanical compression ratio targeted for all the cylinders. . However, when knocking has occurred in some of the cylinders, the mechanical compression ratio of the cylinder in which knocking has not occurred is lower than the desired mechanical compression ratio of the cylinder in which knocking has occurred. For this reason, the exhaust energy is in a state smaller than the desired energy, and the supercharging pressure is smaller than the target pressure.

  Therefore, in the present embodiment, referring to FIG. 1, before reducing the mechanical compression ratio (when the ignition timing is retarded), the flow rate of the exhaust turbine 56 is determined based on the number of cylinders in which knocking has occurred. Make adjustments. In the present embodiment, the opening degree of the waste gate valve 59 disposed in the bypass passage 58 is corrected. The internal combustion engine of the present embodiment performs control to increase the flow rate of the exhaust turbine 56 by reducing the opening degree of the waste gate valve 59 when knocking has occurred in only some of the cylinders. Control to increase the boost pressure to the target pressure.

  FIG. 12 shows another flowchart of the abnormal combustion suppression control in the present embodiment. The control shown in FIG. 12 can be performed following the control shown in FIG. Alternatively, it can be performed together with the control shown in FIG.

  In step 131, it is read whether knocking has occurred in each cylinder. For example, the knocking occurrence cylinder and the non-knock occurrence cylinder detected in step 111 of FIG. 9 can be read.

  In step 132, it is determined whether or not some of the cylinders where knocking has occurred. If all cylinders are knocking, this control is terminated. If some of the cylinders are knocked, the process proceeds to step 133.

  In step 133, a correction amount for the opening degree of the wastegate valve is set. As the number of cylinders in which knocking has not occurred increases, the control for reducing the opening degree of the wastegate valve can be performed.

  FIG. 13 shows a graph of the correction amount of the opening degree of the waste gate valve. The horizontal axis is the number of cylinders where knocking has not occurred. The vertical axis represents the correction amount in the closing direction of the opening degree of the wastegate valve. FIG. 13 shows a graph of three equal lines from a state where the amount of decrease in the mechanical compression ratio is large to a small state. As shown in FIG. 13, as the number of cylinders where knocking has not occurred increases, the supercharging pressure becomes insufficient. Therefore, control for increasing the correction amount of the opening degree of the wastegate valve is performed. That is, control is performed to reduce the opening of the wastegate valve. Further, the control for increasing the correction amount of the opening degree of the waste gate valve can be performed as the amount of decrease in the compression ratio increases. As described above, the correction amount of the wastegate valve can be set based on the amount of decrease in the compression ratio and the number of cylinders in which knocking has not occurred and in which knocking has not occurred.

  Referring to FIG. 12, next, in step 134, the correction of the opening degree of the wastegate valve can be performed based on the set correction amount of the opening degree. As described above, in the abnormal combustion suppression control of the present embodiment, it is possible to suppress a shortage of the supercharging pressure due to the low mechanical compression ratio of the cylinder in which knocking has not occurred.

  The internal combustion engine of the present embodiment has been described with reference to an operation example in which when the load decreases from a high load, the mechanical compression ratio is increased and the closing timing of the intake valve is retarded (see FIG. 5). The present invention can be applied to an internal combustion engine provided with a variable compression ratio mechanism, a variable valve mechanism, and a supercharger.

  The above embodiments can be combined as appropriate. Further, in each of the above-described controls, the order of the steps can be appropriately changed within a range where the functions and actions of the respective steps are the same. In the respective drawings described above, the same or equivalent parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. In the embodiment, the change shown in a claim is included.

DESCRIPTION OF SYMBOLS 1 Engine body 5 Combustion chamber 10 Spark plug 31 Electronic control unit 44 Knock sensor 45 Boost pressure sensor 53 Variable valve timing device 55 Exhaust turbocharger 56 Exhaust turbine 57 Compressor 58 Bypass passage 59 Wastegate valve 79 Crankcase 84, 85 Camshaft 86 Circular cam 87 Eccentric shaft 88 Circular cam 89 Motor

Claims (5)

A variable compression ratio mechanism capable of changing the mechanical compression ratio;
A variable valve mechanism that can change the closing timing of the intake valve;
A supercharger capable of changing the pressure of air supplied to the combustion chamber;
Pressure acquisition means for acquiring the pressure of the air supplied to the combustion chamber;
A discriminating means for discriminating whether or not abnormal combustion has occurred for each cylinder;
If abnormal combustion occurs in at least some of the cylinders, the ignition timing is retarded until abnormal combustion stops, and then the mechanical compression ratio is lowered compared to the mechanical compression ratio when abnormal combustion occurs. , Is configured to perform abnormal combustion suppression control to advance the ignition timing compared to the ignition timing when abnormal combustion occurs ,
In the abnormal combustion suppression control, the ignition timing is advanced so that the advance amount of the ignition timing of the cylinder where the abnormal combustion does not occur is larger than the advance amount of the ignition timing of the cylinder where the abnormal combustion occurs. In addition, when the pressure of the air supplied to the combustion chamber is greater than a predetermined pressure determination value, the supercharging pressure is reduced compared to the supercharging pressure when abnormal combustion occurs , and Control to advance the closing timing of the intake valve compared to the closing timing of the intake valve when abnormal combustion occurs so as to suppress a decrease in the efficiency of air filling in the combustion chamber due to the decrease in the supercharging pressure. Including an internal combustion engine.   The advance amount of the valve closing timing of the intake valve is increased as the amount of decrease in the mechanical compression ratio is larger when the pressure of the air supplied to the combustion chamber is larger than a predetermined pressure judgment value. Internal combustion engine. When the pressure of the air supplied to the combustion chamber is larger than a predetermined pressure judgment value, and the amount of decrease in the mechanical compression ratio is larger than the predetermined compression ratio judgment value, the excess when abnormal combustion occurs is exceeded. compared to the boost pressure Rutotomoni lowers the boost pressure, so as to suppress a decrease in charging efficiency of air in the combustion chamber due to a decrease in supercharger pressure, the closing timing of the intake valve when the abnormal combustion occurs Compared to the boost pressure when abnormal combustion occurs, the boost pressure is reduced when the closing timing of the intake valve is advanced and the amount of decrease in the mechanical compression ratio is less than the predetermined compression ratio judgment value. It is allowed Rutotomoni, so as to suppress a decrease in charging efficiency of air in the combustion chamber due to a decrease in supercharger pressure, the closing timing of the intake valve compared to the closing timing of the intake valve advances when the abnormal combustion occurs prohibiting Ru control is angularly internal combustion engine according to claim 1 or 2   4. The reduction amount of the mechanical compression ratio is set based on a retard amount of the ignition timing when the ignition timing is retarded until the abnormal combustion stops. 5. Internal combustion engine. When the pressure of the air supplied to the combustion chamber is equal to or lower than a predetermined pressure judgment value, the supercharging pressure is reduced compared to the supercharging pressure when abnormal combustion occurs , and combustion is caused by the reduction of the supercharging pressure. so as to suppress the decrease in the charging efficiency of air in the chamber, prohibits Ru control is advanced the closing timing of the intake valve compared to the closing timing of the intake valve when the abnormal combustion occurs, to claim 1 The internal combustion engine described.

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