JP5333268B2 - Spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark-ignition internal combustion engine suppressing occurrence of knocking and degradation of combustion and also suppressing deterioration of fuel economy, even if a mechanical compression ratio detector fails. <P>SOLUTION: This spark-ignition internal combustion engine includes: a variable compression ratio mechanism A varying a mechanical compression ratio; a variable valve timing mechanism B controlling the valve closing timing of an intake valve; the mechanical compression ratio detector 22 detecting the mechanical compression ratio; and a torque variation detection means 43 detecting a torque variation. The variable compression ratio mechanism is controlled so that the mechanical compression ratio becomes a target mechanical compression ratio set according to the operating condition of the engine, and the variable valve timing mechanism is controlled so that the valve closing timing of the intake valve becomes a target valve closing timing set according to the operating condition of the engine. When the mechanical compression ratio detector fails, the mechanical compression ratio is reduced within such a range that the torque variation larger than a reference torque variation is not detected initially by the torque variation detection means if an engine load is increased. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a spark ignition internal combustion engine.

  A spark having a variable compression ratio mechanism capable of changing the mechanical compression ratio and a variable valve timing mechanism capable of controlling the closing timing of the intake valve so that the actual compression ratio is maintained substantially constant regardless of the engine load. An ignition type internal combustion engine is known (for example, Patent Document 1). In this internal combustion engine, as the engine load increases, that is, as the required intake air amount increases, the valve closing timing of the intake valve is advanced so as to approach the intake bottom dead center, and at this time, the actual compression ratio is maintained substantially constant. Therefore, the mechanical compression ratio is lowered as the required intake air amount increases.

JP 2007-303423 A JP 2004-308618 A JP 2006-161583 A

  By the way, as described above, when the valve closing timing and the mechanical compression ratio of the intake valve are changed according to the change in the required intake air amount, the valve closing timing and the mechanical compression ratio of the intake valve are set according to the required intake air amount. The feedback control is performed so that the target valve closing timing and the target mechanical compression ratio of the intake valve are set. That is, with regard to the closing timing of the intake valve, the intake valve in which the current closing timing of the intake valve detected by the closing timing detection device capable of detecting the closing timing of the intake valve is set according to the required intake air amount. The variable valve timing mechanism is controlled so that the target valve closing timing is reached, and for the mechanical compression ratio, the current mechanical compression ratio detected by the mechanical compression ratio detection device capable of detecting the mechanical compression ratio is the required intake air amount The variable compression ratio mechanism is controlled so that the target mechanical compression ratio is set according to the above.

  However, if the valve closing timing detection device or the mechanical compression ratio detection device breaks down, the current valve closing timing and mechanical compression ratio of the intake valve cannot be detected. For this reason, it becomes impossible to control the valve closing timing and the mechanical compression ratio of the intake valve to the target valve closing timing and the target mechanical compression ratio. As a result, fuel consumption is deteriorated and, in some cases, occurrence of knocking or It will lead to deterioration of combustion.

  In view of the above problems, an object of the present invention is to suppress the occurrence of knocking and the deterioration of combustion and the deterioration of fuel consumption even when the valve closing timing detection device and the mechanical compression ratio detection device are out of order. It is an object of the present invention to provide a spark ignition type internal combustion engine.

  In order to solve the above problems, in the first invention, a variable compression ratio mechanism capable of changing the mechanical compression ratio, a variable valve timing mechanism capable of controlling the closing timing of the intake valve, and a mechanical compression ratio can be detected. A mechanical compression ratio detection device and a torque fluctuation detection means for detecting torque fluctuation are provided so that the mechanical compression ratio detected by the mechanical compression ratio detection device becomes a target mechanical compression ratio set according to the engine operating state. In the spark ignition internal combustion engine, the variable compression ratio mechanism is controlled to control the variable valve timing mechanism so that the closing timing of the intake valve becomes the target closing timing set according to the engine operating state. If the compression ratio detection device fails and the engine load increases, the mechanical compression ratio is first lowered within a range in which torque fluctuations greater than the reference torque fluctuation are not detected by the torque fluctuation detection means. It was.

  According to a second invention, in the first invention, when the mechanical compression ratio detection device fails, when the engine load increases, the lowest machine within a range in which the torque fluctuation more than the reference torque fluctuation is not detected by the torque fluctuation detecting means. After the compression ratio is reached or the minimum limit mechanical compression ratio at which the mechanical compression ratio cannot be lowered further due to the mechanism of the variable compression ratio mechanism is reached, the change of the closing timing of the intake valve is started.

  In the third invention, in the first or second invention, when the mechanical compression ratio detection device fails, when the engine load decreases, a range in which torque fluctuation more than the reference torque fluctuation does not occur first by the torque fluctuation detection means. The mechanical compression ratio was increased.

  According to a fourth invention, in the third invention, when the mechanical compression ratio detection device fails, when the engine load decreases, the highest machine within a range in which the torque fluctuation more than the reference torque fluctuation is not detected by the torque fluctuation detecting means. After reaching the compression ratio or reaching the maximum critical mechanical compression ratio at which the mechanical compression ratio cannot be increased further due to the mechanism of the variable compression ratio mechanism, the change of the closing timing of the intake valve is started.

  In a fifth aspect of the invention, in any one of the first to fourth aspects of the invention, during normal operation of the internal combustion engine, the mechanical fluctuation ratio and the intake valve are closed so that the torque fluctuation detection means does not cause a torque fluctuation greater than the reference torque fluctuation. When the valve timing is controlled and the torque fluctuation more than the reference torque fluctuation is detected by the torque fluctuation detecting means during the operation of the internal combustion engine, it is determined that the mechanical compression ratio detection device has failed.

  According to a sixth invention, in any one of the first to fifth inventions, a valve closing timing detection device capable of detecting the valve closing timing of the intake valve, and an intake air amount for detecting a flow rate of air flowing in the intake passage And a variable valve timing mechanism that controls the variable valve timing mechanism so that the closing timing of the intake valve detected by the closing timing detection device becomes a target closing timing set according to the engine operating state. When the timing detection device fails, the closing timing of the intake valve is estimated based on the flow rate of air flowing through the intake passage detected by the intake air amount detection device.

  In a seventh invention, in any one of the first to sixth inventions, an entry prohibition region is set for an operating point indicating a combination of the mechanical compression ratio and the intake valve closing timing, and the mechanical compression ratio detection is performed. If the device is not broken, it can be reached after a certain time without entering the intrusion prohibited area from the current operating point to the operating point that satisfies the required intake air amount when the required intake air amount changes. The target operating point was calculated, and the mechanical compression ratio and intake valve closing timing were changed toward the target operating point.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where a valve closing timing detection apparatus or a mechanical compression ratio detection apparatus fails, generation | occurrence | production of knocking and combustion deterioration can be suppressed, and deterioration of fuel consumption can be suppressed.

1 is an overall view of a spark ignition internal combustion engine. It is a disassembled perspective view of a variable compression ratio mechanism. 1 is a schematic side sectional view of an internal combustion engine. It is a figure which shows a variable valve timing mechanism. It is a figure which shows the lift amount of an intake valve and an exhaust valve. It is a figure for demonstrating a mechanical compression ratio, an actual compression ratio, and an expansion ratio. It is a figure which shows the relationship between theoretical thermal efficiency and an expansion ratio. It is a figure for demonstrating a normal cycle and a super-high expansion ratio cycle. It is a figure which shows changes, such as a mechanical compression ratio according to an engine load. It is a figure which shows an intrusion prohibition area | region and a target operation line. It is a figure which shows an intrusion prohibition area | region and a target operation line. It is a figure which shows an intrusion prohibition area | region. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows the change of mechanical compression ratio, intake valve closing timing, and throttle opening. It is a figure which shows the change of mechanical compression ratio, intake valve closing timing, and throttle opening. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a time chart which shows changes, such as a mechanical compression ratio, intake valve closing timing, and throttle opening. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a figure which shows a target operating point and an operating point. It is a time chart which shows changes, such as a mechanical compression ratio, intake valve closing timing, and throttle opening. It is a flowchart for calculating a target value. It is a flowchart for performing drive control of a variable compression ratio mechanism or the like. It is a figure which shows an intrusion prohibition area | region and a reaching target line. It is a figure which shows an intrusion prohibition area | region and a reaching target line. It is a figure which shows transition of the operating point when the request | requirement intake air amount reduces. It is a figure which shows transition of the operating point when the request | requirement intake air amount reduces. It is a figure which shows transition of the operating point when the request | requirement intake air amount reduces. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a figure which shows transition of the operating point when the request | requirement intake air amount increases. It is a figure which shows transition of the operating point when the request | requirement intake air amount increases. It is a figure which shows transition of the operating point when the request | requirement intake air amount increases. It is a figure which shows transition of the operating point when the request | requirement intake air amount increases. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a figure for demonstrating the advantage at the time of performing control by embodiment of this invention. It is a flowchart for performing drive control of a variable compression ratio mechanism or the like. It is a flowchart for performing drive control of a variable compression ratio mechanism or the like. It is a flowchart for performing drive control of a variable compression ratio mechanism or the like. It is a block diagram of a valve closing timing estimation model. It is a figure which shows the basic concept of a throttle model. It is a figure which shows the relationship between the opening degree of a throttle valve, and a flow coefficient. It is a figure which shows the relationship between the opening degree of a throttle valve, and opening cross-sectional area. It is a figure which shows function (PHI) (Pm / Pa). It is a figure which shows the basic concept of an intake pipe model. It is a figure which shows the basic concept of an intake valve model. It is a figure which shows the function fc.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

FIG. 1 shows a side sectional view of a spark ignition type internal combustion engine.
Referring to FIG. 1, 1 is a crankcase, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is a spark plug disposed at the center of the top surface of the combustion chamber 5, and 7 is an intake air 8 is an intake port, 9 is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via an intake branch pipe 11, and a fuel injection valve 13 for injecting fuel into the corresponding intake port 8 is arranged in each intake branch pipe 11. The fuel injection valve 13 may be arranged in each combustion chamber 5 instead of being attached to each intake branch pipe 11.

  The surge tank 12 is connected to an air cleaner 15 via an intake duct 14, and a throttle valve 17 driven by an actuator 16 and an air flow meter 18 using, for example, heat rays are arranged in the intake duct 14. On the other hand, the exhaust port 10 is connected to a catalytic converter 20 containing, for example, a three-way catalyst via an exhaust manifold 19, and an air-fuel ratio sensor 21 is disposed in the exhaust manifold 19. In the following description, portions of the intake branch pipe 11, the surge tank 12, the intake duct 14 and the like from the throttle valve 17 to the intake valve 7 are referred to as an intake pipe portion.

  On the other hand, in the embodiment shown in FIG. 1, the piston 4 is positioned at the compression top dead center by changing the relative position of the crankcase 1 and the cylinder block 2 in the cylinder axial direction at the connecting portion between the crankcase 1 and the cylinder block 2. There is provided a variable compression ratio mechanism A capable of changing the volume of the combustion chamber 5 at the time, and further an actual compression action start timing changing mechanism B capable of changing the actual start time of the compression action. In the embodiment shown in FIG. 1, the actual compression operation start timing changing mechanism B is composed of a variable valve timing mechanism capable of controlling the closing timing of the intake valve 7.

  As shown in FIG. 1, a relative position sensor 22 for detecting a relative positional relationship between the crankcase 1 and the cylinder block 2 is attached to the crankcase 1 and the cylinder block 2. An output signal indicating a change in the interval between the crankcase 1 and the cylinder block 2 is output. The variable valve timing mechanism B is provided with a valve timing sensor 23 for generating an output signal indicating the closing timing of the intake valve 7, and an output signal indicating the throttle valve opening is provided to the actuator 16 for driving the throttle valve. A throttle opening sensor 24 is attached. In the present embodiment, the relative position sensor 22 is used as a mechanical compression ratio detection device for detecting the current mechanical compression ratio, but a detection device other than the relative position sensor 22 is used as the mechanical compression ratio detection device. It is also possible.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. It comprises. Output signals of the air flow meter 18, the air-fuel ratio sensor 21, the relative position sensor 22, the valve timing sensor 23, and the throttle opening degree sensor 24 are input to the input port 35 via the corresponding AD converters 37, respectively. A load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Is done. Further, a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 35.

  In addition, a torque sensor 43 that generates an output voltage corresponding to the output torque of the internal combustion engine is connected to the crankshaft (not shown), and the output voltage of the torque sensor 43 is input to the input port via the corresponding AD converter 37. 35. On the other hand, the output port 36 is connected to the spark plug 6, the fuel injection valve 13, the throttle valve driving actuator 16, the variable compression ratio mechanism A, and the variable valve timing mechanism B through corresponding drive circuits 38. An intake air temperature sensor 44 that detects the intake air temperature and an atmospheric pressure sensor 45 that detects atmospheric pressure are provided in the vicinity of the air cleaner 15. The intake air temperature sensor 44 and the atmospheric pressure sensor 45 generate output voltages corresponding to the intake air temperature and atmospheric pressure, respectively, and this output signal is input to the input port 35 via the corresponding AD converter 38.

  2 is an exploded perspective view of the variable compression ratio mechanism A shown in FIG. 1, and FIG. 3 is a side sectional view of the internal combustion engine schematically shown. Referring to FIG. 2, a plurality of projecting portions 50 spaced from each other are formed below both side walls of the cylinder block 2, and cam insertion holes 51 each having a circular cross section are formed in each projecting portion 50. Has been. On the other hand, a plurality of protrusions 52 are formed on the upper wall surface of the crankcase 1 so as to be fitted between the corresponding protrusions 50 with a space between each other. Cam insertion holes 53 each having a circular cross section are formed.

  As shown in FIG. 2, a pair of camshafts 54 and 55 are provided, and on each camshaft 54 and 55, a circular cam 58 is rotatably inserted into each cam insertion hole 53. It is fixed. These circular cams 58 are coaxial with the rotational axes of the camshafts 54 and 55. On the other hand, as shown in FIG. 3, eccentric shafts 57 arranged eccentrically with respect to the rotational axes of the cam shafts 54 and 55 extend on both sides of each circular cam 58, and another circular cam is disposed on the eccentric shaft 57. 56 is mounted eccentrically and rotatable. As shown in FIG. 2, these circular cams 56 are arranged on both sides of each circular cam 58, and these circular cams 56 are rotatably inserted into the corresponding cam insertion holes 51. As shown in FIG. 2, a cam rotation angle sensor 25 that generates an output signal representing the rotation angle of the camshaft 55 is attached to the camshaft 55.

  When the circular cams 58 fixed on the camshafts 54 and 55 are rotated in opposite directions as indicated by arrows in FIG. 3A from the state shown in FIG. 3A, the eccentric shafts 57 are separated from each other. In order to move in the direction, the circular cam 56 rotates in the opposite direction to the circular cam 58 in the cam insertion hole 51, and as shown in FIG. 3B, the position of the eccentric shaft 57 is changed from the high position to the intermediate height position. It becomes. Next, when the circular cam 58 is further rotated in the direction indicated by the arrow, the eccentric shaft 57 is at the lowest position as shown in FIG.

  3A, 3B, and 3C show the positional relationship among the center a of the circular cam 58, the center b of the eccentric shaft 57, and the center c of the circular cam 56 in each state. It is shown.

  3A to 3C, the relative positions of the crankcase 1 and the cylinder block 2 are determined by the distance between the center a of the circular cam 58 and the center c of the circular cam 56. As the distance between the center a of 58 and the center c of the circular cam 56 increases, the cylinder block 2 moves away from the crankcase 1. That is, the variable compression ratio mechanism A changes the relative position between the crankcase 1 and the cylinder block 2 by a crank mechanism using a rotating cam. When the cylinder block 2 moves away from the crankcase 1, the volume of the combustion chamber 5 increases when the piston 4 is located at the compression top dead center. Therefore, by rotating the camshafts 54 and 55, the piston 4 is compressed at the top dead center. The volume of the combustion chamber 5 when it is located at can be changed.

  As shown in FIG. 2, in order to rotate the camshafts 54 and 55 in opposite directions, a pair of worms 61 and 62 having opposite spiral directions are attached to the rotation shaft of the drive motor 59, respectively. Worm wheels 63 and 64 meshing with the worms 61 and 62 are fixed to end portions of the camshafts 54 and 55, respectively. In this embodiment, by driving the drive motor 59, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center can be changed over a wide range.

  On the other hand, FIG. 4 shows the variable valve timing mechanism B attached to the end of the camshaft 70 for driving the intake valve 7 in FIG. Referring to FIG. 4, the variable valve timing mechanism B includes a timing pulley 71 that is rotated in the direction of an arrow by a crankshaft of an engine via a timing belt, a cylindrical housing 72 that rotates together with the timing pulley 71, an intake valve A rotating shaft 73 that rotates together with the driving camshaft 70 and is rotatable relative to the cylindrical housing 72, and a plurality of partition walls 74 that extend from the inner peripheral surface of the cylindrical housing 72 to the outer peripheral surface of the rotating shaft 73. And vanes 75 extending from the outer peripheral surface of the rotary shaft 73 to the inner peripheral surface of the cylindrical housing 72 between the partition walls 74, and advance hydraulic chambers 76 on both sides of each vane 75. A retarding hydraulic chamber 77 is formed.

  The hydraulic oil supply control to the hydraulic chambers 76 and 77 is performed by a hydraulic oil supply control valve 78. The hydraulic oil supply control valve 78 includes hydraulic ports 79 and 80 connected to the hydraulic chambers 76 and 77, a hydraulic oil supply port 82 discharged from the hydraulic pump 81, a pair of drain ports 83 and 84, And a spool valve 85 that performs communication cutoff control between the ports 79, 80, 82, 83, and 84.

  When the cam phase of the intake valve driving camshaft 70 should be advanced, the spool valve 85 is moved to the right in FIG. 4 and the hydraulic oil supplied from the supply port 82 is advanced via the hydraulic port 79. The hydraulic oil in the retard hydraulic chamber 77 is discharged from the drain port 84 while being supplied to the hydraulic chamber 76. At this time, the rotary shaft 73 is rotated relative to the cylindrical housing 72 in the direction of the arrow.

  On the other hand, when the cam phase of the intake valve driving camshaft 70 should be retarded, the spool valve 85 is moved to the left in FIG. 4, and the hydraulic oil supplied from the supply port 82 causes the hydraulic port 80 to move. The hydraulic oil in the advance hydraulic chamber 76 is discharged from the drain port 83 while being supplied to the retard hydraulic chamber 77. At this time, the rotating shaft 73 is rotated relative to the cylindrical housing 72 in the direction opposite to the arrow.

  If the spool valve 85 is returned to the neutral position shown in FIG. 4 while the rotation shaft 73 is rotated relative to the cylindrical housing 72, the relative rotation operation of the rotation shaft 73 is stopped, and the rotation shaft 73 is The relative rotation position at that time is held. Therefore, the variable valve timing mechanism B can advance and retard the cam phase of the intake valve driving camshaft 70 by a desired amount.

  In FIG. 5, the solid line shows the time when the cam phase of the intake valve driving camshaft 70 is advanced the most by the variable valve timing mechanism B, and the broken line shows the cam phase of the intake valve driving camshaft 70 being the most advanced. It shows when it is retarded. Therefore, the valve opening period of the intake valve 7 can be arbitrarily set between the range indicated by the solid line and the range indicated by the broken line in FIG. 5, and therefore the closing timing of the intake valve 7 is also the range indicated by the arrow C in FIG. Any crank angle can be set.

  The variable valve timing mechanism B shown in FIG. 1 and FIG. 4 shows an example. For example, the variable valve timing that can change only the closing timing of the intake valve while keeping the opening timing of the intake valve constant. Various types of variable valve timing mechanisms, such as mechanisms, can be used.

  Next, the meanings of terms used in the present application will be described with reference to FIG. 6A, 6B, and 6C show an engine having a combustion chamber volume of 50 ml and a piston stroke volume of 500 ml for the sake of explanation. , (B), (C), the combustion chamber volume represents the volume of the combustion chamber when the piston is located at the compression top dead center.

  FIG. 6A explains the mechanical compression ratio. The mechanical compression ratio is a value mechanically determined only from the stroke volume of the piston and the combustion chamber volume during the compression stroke, and this mechanical compression ratio is expressed by (combustion chamber volume + stroke volume) / combustion chamber volume. In the example shown in FIG. 6A, this mechanical compression ratio is (50 ml + 500 ml) / 50 ml = 11.

  FIG. 6B describes the actual compression ratio. This actual compression ratio is a value determined from the actual piston stroke volume and the combustion chamber volume from when the compression action is actually started until the piston reaches top dead center, and this actual compression ratio is (combustion chamber volume + actual (Stroke volume) / combustion chamber volume. That is, as shown in FIG. 6B, even if the piston starts to rise in the compression stroke, the compression action is not performed while the intake valve is open, and the actual compression starts from the time when the intake valve is closed. The action begins. Therefore, the actual compression ratio is expressed as above using the actual stroke volume. In the example shown in FIG. 6B, the actual compression ratio is (50 ml + 450 ml) / 50 ml = 10.

  FIG. 6C illustrates the expansion ratio. The expansion ratio is a value determined from the stroke volume of the piston and the combustion chamber volume during the expansion stroke, and this expansion ratio is expressed by (combustion chamber volume + stroke volume) / combustion chamber volume. In the example shown in FIG. 6C, this expansion ratio is (50 ml + 500 ml) / 50 ml = 11.

  Next, the super expansion ratio cycle used in the present invention will be described with reference to FIGS. FIG. 7 shows the relationship between the theoretical thermal efficiency and the expansion ratio, and FIG. 8 shows a comparison between a normal cycle and an ultrahigh expansion ratio cycle that are selectively used according to the load in the present invention.

  FIG. 8A shows a normal cycle when the intake valve closes near the bottom dead center and the compression action by the piston is started from the vicinity of the intake bottom dead center. In the example shown in FIG. 8A, the combustion chamber volume is 50 ml and the piston stroke volume is 500 ml as in the examples shown in FIGS. 6A, 6B, and 6C. As can be seen from FIG. 8A, in a normal cycle, the mechanical compression ratio is (50 ml + 500 ml) / 50 ml = 11, the actual compression ratio is almost 11, and the expansion ratio is also (50 ml + 500 ml) / 50 ml = 11. That is, in a normal internal combustion engine, the mechanical compression ratio, the actual compression ratio, and the expansion ratio are substantially equal.

  The solid line in FIG. 7 shows the change in the theoretical thermal efficiency when the actual compression ratio and the expansion ratio are substantially equal, that is, in a normal cycle. In this case, it can be seen that the theoretical thermal efficiency increases as the expansion ratio increases, that is, as the actual compression ratio increases. Therefore, in order to increase the theoretical thermal efficiency in a normal cycle, the actual compression ratio should be increased. However, the actual compression ratio can only be increased to a maximum of about 12 due to the restriction of the occurrence of knocking at the time of engine high load operation, and thus the theoretical thermal efficiency cannot be sufficiently increased in a normal cycle.

  On the other hand, under such circumstances, it is considered to increase the theoretical thermal efficiency while strictly dividing the mechanical compression ratio and the actual compression ratio. As a result, the theoretical thermal efficiency is governed by the expansion ratio, and the actual compression ratio is compared to the theoretical thermal efficiency. Was found to have little effect. That is, if the actual compression ratio is increased, the explosive force is increased, but a large amount of energy is required for compression. Thus, even if the actual compression ratio is increased, the theoretical thermal efficiency is hardly increased.

  On the other hand, when the expansion ratio is increased, the period during which the pressing force acts on the piston during the expansion stroke becomes longer, and thus the period during which the piston applies the rotational force to the crankshaft becomes longer. Therefore, the larger the expansion ratio, the higher the theoretical thermal efficiency. The broken line ε = 10 in FIG. 7 indicates the theoretical thermal efficiency when the expansion ratio is increased with the actual compression ratio fixed at 10. Thus, the theoretical thermal efficiency when the expansion ratio is increased while the actual compression ratio ε is maintained at a low value, and the theoretical thermal efficiency when the actual compression ratio is increased with the expansion ratio as shown by the solid line in FIG. It can be seen that there is no significant difference from the amount of increase.

  Thus, if the actual compression ratio is maintained at a low value, knocking does not occur. Therefore, if the expansion ratio is increased while the actual compression ratio is maintained at a low value, the theoretical thermal efficiency is reduced while preventing the occurrence of knocking. Can be greatly increased. FIG. 8B shows an example where the variable compression ratio mechanism A and variable valve timing mechanism B are used to increase the expansion ratio while maintaining the actual compression ratio at a low value.

  Referring to FIG. 8B, in this example, the variable compression ratio mechanism A reduces the combustion chamber volume from 50 ml to 20 ml. On the other hand, the variable valve timing mechanism B delays the closing timing of the intake valve until the actual piston stroke volume is reduced from 500 ml to 200 ml. As a result, in this example, the actual compression ratio is (20 ml + 200 ml) / 20 ml = 11, and the expansion ratio is (20 ml + 500 ml) / 20 ml = 26. In the normal cycle shown in FIG. 8A, the actual compression ratio is almost 11 and the expansion ratio is 11, as described above. Compared with this case, only the expansion ratio is shown in FIG. 8B. It can be seen that it has been increased to 26. This is why it is called an ultra-high expansion ratio cycle.

  Generally speaking, in an internal combustion engine, the lower the engine load, the worse the thermal efficiency. Therefore, in order to improve the thermal efficiency during engine operation, that is, to improve fuel efficiency, it is necessary to improve the thermal efficiency when the engine load is low. Necessary. On the other hand, in the ultra-high expansion ratio cycle shown in FIG. 8B, since the actual piston stroke volume during the compression stroke is reduced, the amount of intake air that can be sucked into the combustion chamber 5 is reduced. The expansion ratio cycle can only be adopted when the engine load is relatively low. Therefore, in the present invention, when the engine load is relatively low, the super high expansion ratio cycle shown in FIG. 8B is used, and during the engine high load operation, the normal cycle shown in FIG. 8A is used.

Next, the overall operation control will be schematically described with reference to FIG.
FIG. 9 shows changes in the intake air amount, the intake valve closing timing, the mechanical compression ratio, the expansion ratio, the actual compression ratio, and the opening degree of the throttle valve 17 according to the engine load at a certain engine speed. . 9 shows that the average air-fuel ratio in the combustion chamber 5 is the output signal of the air-fuel ratio sensor 21 so that unburned HC, CO and NO _x in the exhaust gas can be simultaneously reduced by the three-way catalyst in the catalytic converter 20. This shows a case where feedback control is performed to the stoichiometric air-fuel ratio based on the above.

  As described above, the normal cycle shown in FIG. 8 (A) is executed during engine high load operation. Therefore, as shown in FIG. 9, the expansion ratio is low because the mechanical compression ratio is lowered at this time, and the valve closing timing of the intake valve 7 is advanced as shown by the solid line in FIG. ing. At this time, the amount of intake air is large, and at this time, the opening degree of the throttle valve 17 is kept fully open, so that the pumping loss is zero.

  On the other hand, as shown by the solid line in FIG. 9, when the engine load becomes low, the closing timing of the intake valve 7 is delayed in order to reduce the intake air amount. Further, at this time, as shown in FIG. 9, the mechanical compression ratio is increased as the engine load is lowered so that the actual compression ratio is kept substantially constant. Therefore, the expansion ratio is also increased as the engine load is lowered. At this time, the throttle valve 17 is kept fully open, and therefore the amount of intake air supplied into the combustion chamber 5 is controlled by changing the closing timing of the intake valve 7 without depending on the throttle valve 17. Has been.

  As described above, when the engine load is reduced from the engine high load operation state, the mechanical compression ratio is increased as the intake air amount is decreased while the actual compression ratio is substantially constant. That is, the volume of the combustion chamber 5 when the piston 4 reaches the compression top dead center is reduced in proportion to the reduction in the intake air amount. Therefore, the volume of the combustion chamber 5 when the piston 4 reaches the compression top dead center changes in proportion to the intake air amount. At this time, in the example shown in FIG. 9, the air-fuel ratio in the combustion chamber 5 is the stoichiometric air-fuel ratio, so the volume of the combustion chamber 5 when the piston 4 reaches the compression top dead center is proportional to the fuel amount. Will change.

When the engine load is further reduced, the mechanical compression ratio is further increased, and when the engine load is reduced to the medium load L ₁ slightly close to the low load, the mechanical compression ratio reaches the maximum limit mechanical compression ratio that is the structural limit of the combustion chamber 5. . When the mechanical compression ratio reaches the maximum critical mechanical compression ratio, the mechanical compression ratio is maintained at the maximum critical mechanical compression ratio in a region where the load is lower than the engine load L ₁ when the mechanical compression ratio reaches the maximum critical mechanical compression ratio. The Therefore, the mechanical compression ratio is maximized and the expansion ratio is maximized at the time of low engine load operation and low engine load operation, that is, on the engine low load operation side. In other words, the mechanical compression ratio is maximized so that the maximum expansion ratio is obtained on the engine low load operation side.

On the other hand, in the embodiment shown in FIG. 9, when the engine load decreases to L ₁ , the closing timing of the intake valve 7 becomes the limit closing timing that can control the amount of intake air supplied into the combustion chamber 5. When the closing timing of the intake valve 7 reaches the limit closing timing, the closing timing of the intake valve 7 in a region where the load is lower than the engine load L ₁ when the closing timing of the intake valve 7 reaches the closing timing. Is held at the limit valve closing timing.

When the closing timing of the intake valve 7 is held at the limit closing timing, the amount of intake air can no longer be controlled by changing the closing timing of the intake valve 7. In the embodiment shown in FIG. 9, at this time, that is, in a region where the load is lower than the engine load L ₁ when the closing timing of the intake valve 7 reaches the limit closing timing, the throttle valve 17 supplies the fuel into the combustion chamber 5. The amount of intake air to be controlled is controlled, and the opening degree of the throttle valve 17 is made smaller as the engine load becomes lower.

On the other hand, as shown by the broken line in FIG. 9, the intake air amount can be controlled without depending on the throttle valve 17 by advancing the closing timing of the intake valve 7 as the engine load becomes lower. Therefore, when expressed so as to include both the case indicated by the solid line and the case indicated by the broken line in FIG. It is moved in a direction away from the intake bottom dead center BDC until the limit valve closing timing L ₁ which can control the intake air amount supplied into the combustion chamber. As described above, the intake air amount can be controlled by changing the closing timing of the intake valve 7 as shown by the solid line in FIG. 9 or by changing it as shown by the broken line. Hereinafter, the present invention will be described by taking as an example a case where the closing timing of the intake valve 7 is changed as shown by a solid line in FIG.

  Incidentally, as described above, the expansion ratio is set to 26 in the ultra-high expansion ratio cycle shown in FIG. The higher the expansion ratio, the better. However, as can be seen from FIG. 7, a considerably high theoretical thermal efficiency can be obtained if it is 20 or more with respect to the practically usable lower limit actual compression ratio ε = 5. Therefore, in the present invention, the variable compression ratio mechanism A is formed so that the expansion ratio is 20 or more.

  Next, the reference prohibition line for the intrusion prohibited region, the mechanical compression ratio, and the intake valve closing timing will be described with reference to FIGS.

  FIG. 10 shows the intake air amount necessary to obtain the required engine load, that is, the required intake air amount, the mechanical compression ratio, and the intake valve closing timing. In FIG. 10, the required intake air amount increases as the distance from the origin 0 increases, and the mechanical compression ratio increases as the distance from the origin 0 increases. Further, in FIG. 10, the intake valve closing timing is represented by the crank angle after the intake bottom dead center (ABDC). Therefore, the intake valve closing timing is retarded as the distance from the origin 0 is increased.

On the other hand, in FIG. 10, Q ₁ , Q ₂ , Q ₃ , Q ₄ , and Q ₅ each represent the same intake air amount surface, and Q ₆ represents the throttle fully open surface where the throttle valve 17 is fully open. As can be seen from FIG. 10, the throttle fully open surface Q ₆ is a curved surface convex upward. In the region below the throttle fully open surface Q _6, the throttle opening becomes smaller as it goes downward.

In FIG. 10, hatched areas indicate intrusion prohibited areas in the same intake air amount surfaces Q ₁ , Q ₂ , Q ₃ , Q ₄ , and Q ₅ . On the other hand, FIG. 11 shows the top view of FIG. 10, FIG. 12 (A) shows the left side surface S ₁ in FIG. 10 as seen from the direction of the arrow, and FIG. The right side S ₂ is shown as seen from the direction of the arrow, and in FIGS. 11 and 12A and 12B, the hatched area indicates an intrusion prohibited area.

10, 11, 12 (A) and 12 (B), the intrusion prohibition region is three-dimensionally expanded. Further, the intrusion prohibition region includes a high load side region X ₁ and a low load side region X ₂ . It can be seen that it consists of two regions. As can be seen from FIGS. 10, 11, 12 (A) and 12 (B), the high load side intrusion prohibited region X ₁ has a large required intake air amount, and the intake valve closing timing is advanced and the mechanical compression ratio is increased. is formed on the high side, low-load forbidden entry area X ₂ is less required intake air amount, the mechanical compression ratio is formed on a lower side in the intake valve closing timing is retarded side.

FIG. 9 shows the relationship between the intake valve closing timing, the mechanical compression ratio, the actual compression ratio, and the throttle opening, at which the minimum fuel consumption can be obtained with respect to the required intake air amount. In FIG. 10 and FIG. As can be seen from FIG. 10, this line W extends on the throttle fully open surface Q ₆ on the side where the intake air amount is larger than the same intake air amount surface Q ₃ , and the intake air amount is larger than the same intake air amount surface Q _3. less the side extends over the right side S _2. The same intake air amount surface Q ₃ corresponds to the load L ₁ in FIG.

That is, in the region where the engine load is higher than L ₁ in FIG. 9, the intake valve closing timing is advanced with the throttle valve 17 being held fully open as the engine load increases, that is, as the required intake air amount increases. At this time, the mechanical compression ratio is lowered as the required intake air amount increases so that the actual compression ratio becomes constant. The relationship between the mechanical compression ratio and the intake valve closing timing at this time is represented by a line W on the throttle fully open surface Q ₆ in FIG. That is, as shown in FIG. 10, on the side where the intake air amount is larger than the same intake air amount surface Q ₃ , the intake valve closing timing is set while the throttle valve 17 is held fully open as the required intake air amount increases. At this time, the mechanical compression ratio is lowered as the required intake air amount increases so that the actual compression ratio becomes constant.

On the other hand, in the region where the engine load is lower than L ₁ in FIG. 9, the mechanical compression ratio and the intake valve closing timing are kept constant, and the throttle valve 17 opens as the engine load decreases, that is, the required intake air amount decreases. The degree is reduced. Relationship, the mechanical compression ratio and the intake valve closing timing at this time is represented by a line W on the right side S ₂ of Figure 10. That is, as shown in FIG. 10, on the side where the intake air amount is smaller than the same intake air amount surface Q ₃ , the mechanical compression ratio and the intake valve closing timing are kept constant, and the lower the engine load, that is, the required intake air. As the amount decreases, the opening degree of the throttle valve 17 is decreased.

  In the present specification, the line that the mechanical compression ratio and the intake valve closing timing follow when the required intake air amount changes is referred to as an operation line, and in particular, the line W shown in FIG. 10 is referred to as a reference operation line. ing. Note that, as described above, this reference operation line indicates the minimum fuel consumption operation line with which the minimum fuel consumption can be obtained.

As described above, the actual compression ratio is constant on the reference operation line W. Since the actual compression ratio is independent of the opening degree of the throttle valve 17 and is determined only by the mechanical compression ratio and the intake valve closing timing, the actual compression ratio is the same on the curved surface extending in the vertical direction through the reference operation line W in FIG. Become. In this case, the actual compression ratio becomes higher on the side where the mechanical compression ratio is higher than the curved surface, and the actual compression ratio becomes lower on the side where the mechanical compression ratio is lower than the curved surface. That is, roughly speaking, the high load side intrusion prohibited region X ₁ is located in a region where the actual compression ratio is higher than the actual compression ratio on the reference operation line W, and the low load side intrusion prohibited region X ₂ is the reference operation. It is located in a region where the actual compression ratio is lower than the actual compression ratio on the line W.

If the actual compression ratio is increased to improve fuel consumption, knocking occurs. If the ignition timing is retarded to prevent knocking, combustion becomes unstable and torque fluctuation occurs. High load forbidden entry area X ₁ is operating regions produce such torque variations, hence at the time of engine operation the operating state of the engine needs to be prevented from entering the operating area of produce such torque fluctuations. On the other hand, when the amount of intake air is small and the actual compression ratio is low, combustion is difficult, and when the opening of the throttle valve 17 is small and the compression end pressure is low, combustion is deteriorated and torque fluctuation occurs. The low load side forbidden entry area X ₂ are operating region resulting such torque variations at the time of engine operation therefore it is necessary that the operating state of the engine in this operating region from entering.

On the other hand, the higher the actual compression ratio, the better the fuel consumption. Therefore, the minimum fuel consumption operation line that can obtain the minimum fuel consumption without causing knocking or torque fluctuation is prohibited from entering the high load side as indicated by W in FIGS. extends while along the outer edge of the high-load side forbidden entry area X ₁ outside the region X _1. As described above, in the embodiment according to the present invention, this minimum fuel consumption operation line is the reference operation line W, and basically shows a combination of the mechanical compression ratio and the intake valve closing timing according to the required intake air amount. The mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are controlled so that the operating point moves on the reference operating line W. The current operating point is always detected by the relative position sensor 22, the valve timing sensor 23, and the throttle opening sensor 24.

  Next, how to control the mechanical compression ratio, the intake valve closing timing and the opening degree of the throttle valve 17 according to the present invention will be described from the basic control method. This basic control method is shown in FIGS.

That is, FIG. 13 shows a case where the required intake air amount is increased when the mechanical compression ratio and the intake valve closing timing are maintained at the values at the point m on the reference operation line W. Incidentally, in the embodiment according to the present invention, for example, the required intake air amount is calculated every predetermined time, and the operating point on the reference operation line W satisfying the required intake air amount calculated every predetermined time. Are sequentially calculated. Examples of operating points that satisfy this required intake air amount, that is, required operating points are indicated by a ₁ , a ₂ , a ₃ , a ₄ , a ₅ , and a ₆ in FIG. That is, in this example, the requested operating point that satisfies the requested intake air amount that is detected first after the requested intake air amount is increased is a ₁ , and the requested operating point that satisfies the detected requested intake air amount is the next. is a _2, then fill the detected required amount of intake air required operating point is a _3.

When the required operating point changes, the operating point indicating the mechanical compression ratio and the intake valve closing timing changes toward a new required operating point. In other words, toward the _point a changes from the operating point requests the operating point is set to a ₁ m point showing a mechanical compression ratio and the intake valve closing timing in the example shown in FIG. 13, the required operating point is a _When it is ₂ , the operating point indicating the mechanical compression ratio and the intake valve closing timing changes toward a ₂ . In this case, if the mechanical compression ratio and intake valve closing timing reach the required operating point before the required operating point changes, the mechanical compression ratio and intake valve closing timing follow the change in the required operating point without any problem. Change. However, problems may arise if the mechanical compression ratio and the intake valve closing timing do not reach the required operating point before the required operating point changes.

That is, in FIG. 13, when the mechanical compression ratio and the intake valve closing timing are at the point m and the required operating point a ₁ is reached, the mechanical compression ratio and the intake valve timing do not change, and at this time, the required intake air amount is satisfied. Accordingly, the opening degree of the throttle valve 17 is increased. The response of the opening change of the throttle valve 17 by the actuator 16 is very fast. Therefore, when the required operating point becomes a ₁ , the operating point indicating the mechanical compression ratio and the intake valve closing timing immediately shifts from the m point to the a ₁ point.

Then the required operating point while it is just slightly advanced mechanical compression ratio is made to decrease only slightly and the intake valve closing timing becomes the a ₂ is the throttle valve 17 is fully opened. At this time, the mechanical compression ratio and the intake valve closing timing reach close to the required operating point a ₂ when the next required operating point a ₃ is calculated. Indicated by the operating point b ₂ in FIG. 14 showing the place mechanical compression ratio and the intake valve closing timing is viewed from above in FIG. 13 to reach this time.

When the required operating point a ₃ is calculated, the mechanical compression ratio and the intake valve closing timing start moving from the operating point b ₂ toward the required operating point a ₃ . That is, the mechanical compression ratio is lowered while the throttle valve 17 is fully open, and the intake valve closing timing is advanced. However, the response of the mechanical compression ratio change by the variable compression ratio mechanism A and the response of the valve closing timing change of the intake valve 7 by the variable valve timing mechanism B are not so fast. Sex is quite slow. Therefore, when the increase rate of the required intake air amount is high, the required operating point and the operating point indicating the actual values of the mechanical compression ratio and the intake valve closing timing are gradually separated. For example, in FIG. 14, when the required operating point moves to a _{6, the} operating point indicating the actual values of the mechanical compression ratio and the intake valve closing timing is still located near b ₂ .

However, when such a mechanical compression ratio and the intake valve closing timing when the move by the feedback control toward the required operating point without entering the closing timing mechanical compression ratio and the intake valve forbidden entry region X ₁ It takes time to reach the required operating point. That is, in this case, the advance action of the intake valve closing timing when the operating point is about to penetrate the forbidden entry area X ₁ is stopped by advancing the intake valve closing timing, then the mechanical compression ratio is It can be reduced by a certain amount. The mechanical compression ratio is again advanced the intake valve closing timing and used to lower by a certain amount, the operating point is advancing action of the intake valve closing timing is stopped to become likely to invade forbidden entry area X _1. This is repeated below.

That is, the operating point showing a mechanical compression ratio and the intake valve closing timing when the move by the feedback control toward the mechanical compression ratio and the intake valve closing timing to the required operating point along the outer edge of the forbidden entry area X ₁ Therefore, it takes time for the mechanical compression ratio and the intake valve closing timing to reach the required operating point. As a result, good engine responsiveness cannot be obtained with respect to changes in the required intake air amount.

Therefore, in the present invention, when the required intake air amount changes, the mechanical compression ratio and the intake valve closing timing enter the intrusion prohibited areas X ₁ and X ₂ from the current operating point toward the required operating point that satisfies the required intake air amount. A target operating point that can be reached after a certain time without intrusion is calculated, and the mechanical compression ratio and the intake valve closing timing are changed toward the target operating point.

Next, an embodiment embodying the present invention will be described with reference to FIG. 14 showing a throttle fully open surface Q ₆ . As described above, FIG. 14 shows a case where the operating point indicating the mechanical compression ratio and the intake valve closing timing is b ₂ when the required operating point becomes a ₃ . In this case, the arrow R ₂ indicates the amount that the mechanical compression ratio can reach in the predetermined operation time toward the required operating point a ₃ , and the arrow T ₂ indicates that the intake valve closing timing is the required operating point a _3. Represents the amount that can be reached in a predetermined time. In FIG. 14, c ₂ is a target operating point that can be reached after a certain time without entering the intrusion prohibited area X ₁ from the current operating point b ₂ toward the required operating point a ₃ that satisfies the required intake air amount. Show.

As the target operating point c ₂ when the required intake air amount is made to increase and the operating point b ₂ and the required operating point a ₃ is on full throttle surface Q ₆ is on the reference operating line W shown in FIG. 14, In the example shown in FIG. 14, it is located on the minimum fuel consumption operation line W. That is, in the example shown in FIG. 14, the minimum fuel consumption operating target operating point which extends along the outer edge of the outside and a by forbidden entry area X ₁ of the forbidden entry area X ₁ when the throttle valve 17 is maintained fully open It can be moved on the line W.

In FIG. 14, if the operating point indicating the mechanical compression ratio and the intake valve closing timing is b _i when the required operating point is a ₆ , the target operating point is also a point on the reference operating line W. c _i . In FIG. 14, the arrow R _i similarly represents the amount that the mechanical compression ratio can reach after a certain time, and the arrow T _i represents the amount that the intake valve closing timing can reach after a certain time.

In this way, in the example shown in FIG. 14, when the target operating point c ₂ is calculated when the operating point is b ₂ , the operating point indicating the mechanical compression ratio and the intake valve closing timing after a certain time is the target operating point c. Reach ₂ At this time, the next new target operating point that can be reached after a certain time without entering the intrusion prohibited area X ₁ from the current operating point c ₂ toward the required operating point that satisfies the required intake air amount is calculated, The point reaches this new target operating point after a certain time. In this case, in the embodiment according to the present invention, the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are made to reach the target operating point by PID (proportional integral derivative) control.

  As described above, in the example shown in FIG. 14, the operating point indicating the mechanical compression ratio and the intake valve closing timing moves smoothly along the reference operation line W without stagnation. That is, when the required intake air amount is increased when the mechanical compression ratio and the intake valve closing timing are maintained at the point m in FIG. 13, the mechanical compression ratio and the intake valve closing timing are indicated by arrows in FIG. Thus, it can be smoothly changed along the reference operation line W without stagnating. As a result, it is possible to ensure a good engine response to changes in the required intake air amount.

In this case, in order to further improve the responsiveness of the engine with respect to the required intake air amount, it is preferable that the target operating points c ₂ and c _i be separated from the corresponding current operating points b ₂ and b _i as much as possible. Therefore, in the embodiment according to the present invention, the target operating points c ₂ and c _i enter the intrusion prohibited area X ₁ from the corresponding current operating points b ₂ and b _i toward the required operating point that satisfies the required intake air amount. Among the operating points that can be reached after a certain time, the operating point is the farthest from the current operating points b ₂ and b _i .

That is reached the limit of the mechanical compression ratio from the operating point b ₂ in the case the current operating point is b ₂ is a target operating point c _2, the target operating point c ₂ for intake valve closing timing operating point the front of the arrival limit of the intake valve closing timing from b _2. Therefore, at this time, the mechanical compression ratio is lowered at the maximum possible speed, and the intake valve closing timing is advanced at a speed slower than the maximum possible speed. In contrast, the arrival limit of the intake valve closing timing from the operating point b _i in the case of the b _i the current operating point is a target operating point c _i, the target operating point c _i for the mechanical compression ratio the front of the arrival limit of the intake valve closing timing from the operating point b _i. Therefore, at this time, the intake valve closing timing is advanced at the maximum possible speed, and the mechanical compression ratio is decreased at a speed slower than the maximum possible speed.

  Next, a case where the required intake air amount is reduced will be described with reference to FIGS. Of FIGS. 16 to 31, FIGS. 16 and 17 show cases where the required intake air amount is slowly reduced, and FIGS. 18 to 25 show the required intake air amount being reduced relatively quickly. FIG. 26 to FIG. 31 show the case where the required intake air amount is sharply reduced. 16 to 31 show a case where the action of reducing the required intake air amount is started when the operating point indicating the combination of the mechanical compression ratio and the intake valve closing timing is n point on the reference operating line W. ing.

First, a case where the required intake air amount is slowly reduced will be described with reference to FIGS. 16 and 17. FIG. 17 shows a throttle fully open surface Q ₆ similar to FIG.

FIG. 17 shows the relationship between the current operating point and the requested operating point in this case. In other words, the required operating point of time in Figure 17 the current operating point is e _i is indicated by d _i, the amount can reach after the mechanical compression ratio at this time is a predetermined time is indicated by R _i At this time, the amount that the intake valve closing timing can be reached after a predetermined time is indicated by S _i . Further in FIG. 17 is shown requesting operating point when the current operating point is e _j is in d _j, this time the amount can reach after the mechanical compression ratio is a predetermined time is indicated by R _j, At this time, the amount that the intake valve closing timing can be reached after a certain time is indicated by S _j .

In this case, the required operating point d _i is before the reaching limit of the mechanical compression ratio and is before the reaching limit of the intake valve closing timing, so that the required operating point d _i becomes the target operating point. Similarly, the required operating point _dj is before the reaching limit of the mechanical compression ratio and is before the reaching limit of the intake valve closing timing, so that the required operating point _dj is the target operating point. Therefore, in this case, the operating point moves along the reference operating line W. That is, when the required intake air amount decreases slowly, the intake valve closing timing is gradually retarded while the throttle valve 17 is kept fully open, and the mechanical compression ratio gradually increases so that the actual compression ratio becomes constant. Will be increased.

Next, a case where the required intake air amount is decreased relatively quickly will be described with reference to FIGS. As described above, in the embodiment according to the present invention, for example, the required intake air amount is calculated every predetermined time, and the required operation point on the reference operation line W that satisfies the sequentially calculated required intake air amount is shown in FIG. D ₁ , d ₂ , d ₃ , d ₄ , and d ₅ .

In order to easily understand the control according to the present invention, FIG. 18 shows that the required intake air amount at the required operation point d ₁ is Q ₅ , and the required intake air amounts at the required operation point d ₂ are Q ₅ and Q ₄ . It is an intermediate value, the required intake air amount at the required operating point d ₃ is Q ₄ , the required intake air amount at the required operating point d ₄ is an intermediate value between Q ₄ and Q ₃ , and at the required operating point d ₅ The case where the required intake air amount is Q ₃ is shown. That sequentially calculated required amount of intake air from the Q ₆ (n points), an intermediate value of Q _5, Q ₅ and Q _4, an intermediate value of Q _4, Q ₄ and Q _3, a case where the change in Q ₃ Show.

The Figure 19 shows a wide open throttle plane Q _6, FIG. 20 is the intake air amount represents the same intake air amount plane of Q _5, FIG. 21 is the intake air amount of the intermediate value Q ₅ and Q ₄ 22 shows the same intake air amount surface, FIG. 22 shows the same intake air amount surface where the intake air amount is Q ₄ , and FIG. 23 shows the same intake air amount where the intake air amount is an intermediate value between Q ₄ and Q _3. It shows a plane, Figure 24 is the intake air amount indicates the same intake air amount plane of Q _3.

Now, when the mechanical compression ratio and the intake valve closing timing are held at the operating point n shown in FIG. 18, the required intake air amount changes from Q ₆ to Q _5, and as a result, the required operating point becomes d ₁ . If this is the case, first, the target operating point e ₁ is calculated on the throttle fully open surface Q ₆ as shown in FIG. The calculation method of the target operating point e ₁ is the same as the calculation method described so far, and the intrusion starts from the amount that the mechanical compression ratio can reach after a certain time and the amount that the intake valve closing timing can reach the certain time. target operating point e ₁ closest to the required operating point d ₁ without entering the forbidden area X ₁ is calculated. In the example shown in FIG. 19, the target operation point e ₁ is located on the reference operation line W.

Incidentally, the intake air amount at the target operating point e ₁ is an intermediate value between Q ₆ and Q ₅ and is larger than the required intake air amount Q ₅ . However, it is preferable that the intake air amount matches the required intake air amount as much as possible. However, when the required intake air amount is decreased, the intake air amount can be adjusted by changing the opening of the throttle valve 17. Therefore, when the intake air amount at the target operating point e ₁ is larger than the required intake air amount Q _{5, the} required intake air amount is set without changing the target values for the mechanical compression ratio and the intake valve closing timing. until the target opening degree required for the amount Q ₅ so that to close the throttle valve 17.

That is, in FIG. 18, the final target operating point e ₁ is a point on the same intake air amount surface Q ₅ located immediately below the target operating point e ₁ on the throttle fully open surface Q ₆ shown in FIG. . The final target operating point e ₁ on the same intake air amount surface Q ₅ is shown in FIGS. 18 and 20, and the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are the final values. The target operating point e ₁ is changed. That is, at this time, the mechanical compression ratio is increased, the intake valve closing timing is retarded, and the opening degree of the throttle valve 17 is decreased from the fully opened state.

Next, when the required intake air amount becomes an intermediate value between Q ₅ and Q ₄ and the required operating point becomes d ₂ , this time, on the same intake air amount surface at the current intake air amount Q ₅ as shown in FIG. A target operating point e ₂ is calculated. The calculation method of the target operating point e ₂ is the same as the calculation method described so far, and the intrusion starts from the amount that the mechanical compression ratio can reach after a certain time and the amount that the intake valve closing timing can reach the certain time. target operating point e ₂ closest to the required operating point d ₂ without entering the forbidden area X ₁ is calculated. In the example shown in FIG. 20, this target operating point e ₂ is located on the reference operating line W in the same intake air amount surface Q ₅ (note that the reference operating line W at this time is the reference operating line shown in FIG. It is different from the operation wire W, and the minimum fuel consumption operation line at the same intake air amount plane Q _5).

In this case as well, the intake air amount at the target operating point e ₂ is larger than the required intake air amount. Therefore, also in this case, in FIG. 18, on the same intake air amount surface (intermediate value between Q ₅ and Q ₄ ) located directly below the target operating point e ₂ on the same intake air amount surface Q ₅ shown in FIG. Is the final target operating point e ₂ . The final target operating point e ₂ on the same intake air amount surface (intermediate value between Q ₅ and Q ₄ ) is shown in FIGS. 18 and 21, and the mechanical compression ratio, intake valve closing timing and throttle valve are shown. The opening degree of 17 is changed toward this final target operating point e ₂ . Also at this time, the mechanical compression ratio is increased, the intake valve closing timing is retarded, and the opening degree of the throttle valve 17 is reduced from the fully opened state.

Next, when the required intake air amount becomes Q ₄ , then becomes an intermediate value between Q ₄ and Q ₃ , and then becomes Q ₃ , the same thing is sequentially repeated. That is, when the required intake air amount reaches Q ₄ , the final target operating point e ₃ on the same intake air amount surface Q ₄ is calculated as shown in FIG. 22, and the required intake air amount is between Q ₄ and Q ₃ . It becomes an intermediate value is a final target operating point e ₄ is calculated on the (intermediate value between Q ₄ and Q ₃₎ identical intake air amount plane as shown in FIG. 23, then requested intake air amount to the Q ₃ Then, as shown in FIG. 24, the final target operating point e ₅ on the same intake air amount surface Q ₃ is calculated.

During this time, that is, while the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are sequentially changed toward the final target operating points e ₃ , e ₄ , e ₅ , the mechanical compression ratio increases. The intake valve closing timing is retarded, and the opening degree of the throttle valve 17 is reduced.

When the required intake air amount reaches Q ₃ , final target operating points e ₆ , e ₇ , e ₈ , e ₉ , e ₁₀ are calculated sequentially on the same intake air amount surface Q ₃ as shown in FIG. The mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are sequentially changed to the required operating point d ₅ through these final target operating points e ₆ , e ₇ , e ₈ , e ₉ , e _10. It will be. During this time, the mechanical compression ratio is increased, the intake valve closing timing is retarded until reaching e ₈ , the opening of the throttle valve 17 is gradually increased, and when it reaches e _8, it is fully opened.

FIG. 25 shows the intake valve closing timing and the mechanical compression ratio when the target intake air amount is decreased relatively quickly from Q ₆ (n point) to Q ₃ (target operating point d ₅ ) as shown in FIG. , Changes in actual compression ratio and throttle opening. From FIG. 25, in this case, after the required intake air amount reaches the final target value Q ₃ (operating point e ₄ ), the retarding operation of the intake valve closing timing is completed (operating point e ₈ ). It can be seen that the increasing action of the mechanical compression ratio is completed (target operating point d ₅ ). On the other hand, the actual compression ratio gradually decreases until the retarding action of the intake valve closing timing is completed (operating point d ₈ ), and then gradually increases. Further, the throttle opening is gradually decreased from the fully opened state until the operating point becomes the operating point e ₅ on the same intake air amount surface Q ₃ , and then until the retarding operation of the intake valve closing timing is completed (operation The valve is gradually opened until it is fully opened up to point e ₈ ).

As shown in FIGS. 18 to 25, when the required intake air amount is decreased relatively quickly, the throttle opening is also controlled in addition to the control of the mechanical compression ratio and the intake valve closing timing. In the present invention, at this time, the three-dimensional intrusion prohibited areas X ₁ and X ₂ are set for the combination of the mechanical compression ratio, the intake valve closing timing, and the throttle opening, and the mechanical compression ratio, the intake valve closing timing, An operating point indicating a combination with the throttle opening is prohibited from entering the three-dimensional intrusion prohibited areas X ₁ and X ₂ .

In this case as well, when the required intake air amount changes, the mechanical compression ratio and the intake valve closing timing are three-dimensional intrusion prohibited region X ₁ from the current operating point toward the operating point that satisfies the required intake air amount. The target operating point that can be reached after a certain time without entering X ₂ is calculated, and the mechanical compression ratio and the intake valve closing timing are changed toward the calculated target operating point. Further, in this case, when the required intake air amount changes, the throttle opening is changed according to the required intake air amount so as not to enter the three-dimensional intrusion prohibited areas X ₁ and X ₂ .

Even in this case, the target operating point is the required intake air amount from the current operating point so that the mechanical compression ratio, intake valve closing timing, and throttle opening reach the required operating point that satisfies the required intake air amount as soon as possible. Among the operating points that can be reached after a certain time without entering the three-dimensional intrusion prohibited areas X ₁ and X ₂ toward the operating point that satisfies the above, the operating point that is farthest from the current operating point is set.

Further, in this case, in the embodiment according to the present invention, when the required intake air amount decreases, the mechanical compression ratio and the intake valve closing timing are changed from the current operating point toward the operating point that satisfies the required intake air amount. A target operating point that can be reached after a certain time without entering the intrusion prohibited areas X ₁ and X ₂ in the intake air amount is calculated, and toward the target operating point where the mechanical compression ratio and the intake valve closing timing are calculated Can be changed. On the other hand, in this case, as for the throttle opening, the target opening satisfying the required intake air amount is calculated at the calculated target operating point, and the throttle is not limited unless the target opening is in the three-dimensional intrusion prohibited areas X ₁ and X _2. The opening is changed to the target opening.

Next, a case where the required intake air amount is suddenly reduced to the minimum intake air amount Q ₁ will be described with reference to FIGS. As described above, in the embodiment according to the present invention, for example, the required intake air amount is calculated every predetermined time, and the required operation point on the reference operation line W that satisfies the sequentially calculated required intake air amount is shown in FIG. D ₁ , d ₂ , and d ₃ .

In this case as well, in order to easily understand the control according to the present invention, FIG. 26 shows that the required intake air amount at the required operating point d ₁ is Q ₄ and the required intake air amount at the required operating point d ₂ is Q _2. And Q ₃ , and the required intake air amount at the required operating point d ₃ is Q ₁ . That is, a case is shown in which the sequentially calculated required intake air amount changes from Q ₆ (n point) to Q ₄ , an intermediate value between Q ₃ and Q ₂ , Q ₁ .

FIG. 27 shows the throttle fully open surface Q ₆ , FIG. 28 shows the same intake air amount surface with the intake air amount Q ₄ , and FIG. 29 shows the intake air amount with an intermediate value between Q ₃ and Q ₂ . It shows the same intake air amount plane, Figure 30 is the intake air amount indicates the same intake air amount plane of Q _1.

Now, when the mechanical compression ratio and the intake valve closing timing are held at the operating point n shown in FIG. 26, the required intake air amount changes from Q ₆ to Q _4, and as a result, the required operating point becomes d ₁ . If this is the case, first, as shown in FIG. 27, the target operating point e ₁ is calculated on the throttle fully open surface Q ₆ . The calculation method of this target operating point e ₁ is the same as the calculation method shown in FIG. 19, and enters from the amount that the mechanical compression ratio can be reached after a certain time and the amount that the intake valve closing timing can reach the certain time. target operating point e ₁ closest to the required operating point d ₁ without entering the forbidden area X ₁ is calculated. In the example shown in FIG. 27, the target operation point e ₁ is located on the reference operation line W.

On the other hand, at this time, similarly to the case shown in FIG. 18, the target values for the mechanical compression ratio and the intake valve closing timing are not changed, and the target opening required to make the intake air amount the required intake air amount Q ₄ is not changed. The throttle valve 17 is closed.

That is, in FIG. 26, a point on the same intake air amount surface Q ₄ located immediately below the target operating point e ₁ on the throttle fully open surface Q ₆ shown in FIG. 27 is set as the final target operating point e _1. . The final target operating point e ₁ on the same intake air amount surface Q ₄ is shown in FIGS. 26 and 28. The mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are the final values. The target operating point e ₁ is changed. At this time, the mechanical compression ratio is increased, the intake valve closing timing is retarded, and the opening degree of the throttle valve 17 is reduced from the fully opened state.

Next, when the required intake air amount becomes an intermediate value between Q ₃ and Q ₂ and the required operation point becomes d ₂ , this time, on the same intake air amount surface in the current intake air amount Q ₄ as shown in FIG. A target operating point e ₂ is calculated. The calculation method of the target operating point e ₂ is the same as the calculation method described so far, and the intrusion starts from the amount that the mechanical compression ratio can reach after a certain time and the amount that the intake valve closing timing can reach the certain time. target operating point e ₂ closest to the required operating point d ₂ without entering the forbidden area X ₁ is calculated. Also in this case, in FIG. 26, on the same intake air amount surface (intermediate value between Q ₃ and Q ₂ ) located directly below the target operating point e ₂ on the same intake air amount surface Q ₄ shown in FIG. The point is set as the final target operation point e ₂ . FIG. 26 and FIG. 29 show the final target operating point e ₂ on the same intake air amount surface (an intermediate value between Q ₃ and Q ₂ ).

Next, when the required intake air amount becomes Q ₁ and the required operating point becomes d ₃ , the target operating point e ₃ is calculated on the same intake air amount surface (intermediate value of Q ₃ and Q ₂ ) as shown in FIG. Then, as shown in FIG. 30, a final target operating point e ₃ on the same intake air amount surface Q ₁ is calculated. When the final target operating point e ₃ is calculated, the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are changed toward the final target operating point e ₃ . Also at this time, the mechanical compression ratio is increased, the intake valve closing timing is retarded, and the opening degree of the throttle valve 17 is reduced from the fully opened state.

Meanwhile the low load side forbidden entry area X ₂ comes appear in the same intake air amount plane in this way required intake air amount is reduced. Low load forbidden entry area X ₂ appearing on the same intake air amount plane increases as the amount of intake air is small, the low load side forbidden entry area X ₂ appearing on the same intake air amount plane as shown in FIG. 30 becomes maximum when the required intake air amount is minimized Q ₁ in. In the embodiment according to the present invention, the operating point into the low load intrusion prohibition region X ₂ is slightly spaced from the low load side intrusion prohibition region X ₂ around the low load side intrusion prohibition region X ₂ . An intrusion prevention surface for preventing intrusion is set in advance, and an intrusion prevention line that is an intersection line between the intrusion prevention surface and the same intake air amount surface is indicated by WX in FIG.

In the embodiment according to the present invention, when the intake air amount becomes the required intake air amount Q ₁ , as shown in FIG. 30, the amount that the mechanical compression ratio can reach after a certain time on the same intake air amount surface Q ₁ and the intake valve Each target operating point e ₄ , e ₅ , e ₆ , e ₇ , e ₈ , e ₉ , e ₁₀ , e ₁₁ , e ₁₂ closest to the required operating point d ₃ from the amount that the valve closing timing can reach a certain time. Are sequentially calculated. In this case, the calculated target operating point when the calculated target operating point closest to the required operating point d ₃ , such as the target operating point e ₄ , is located on the opposite side of the intrusion prevention area X ₂ with respect to the intrusion prevention line WX. Is the target operating point e ₄ . On the other hand, when the calculated target operating point closest to the required operating point d ₃ is closer to the intrusion prohibition region X ₂ than the intrusion prevention line WX, either the mechanical compression ratio or the intake valve closing timing is reached. The points on the intrusion prevention line WX that are the limits are set as the target operating points e ₅ , e ₆ , e ₇ , e ₈ , and e ₉ .

That is, when the required intake air amount becomes Q ₁ , the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are sequentially set to the final target operating points e ₄ , e ₅ , on the same intake air amount surface Q ₁ , The required operating point d _{3 is} changed through e ₆ , e ₇ , e ₈ , e ₉ , e ₁₀ , e ₁₁ , e ₁₂ . During this time, the mechanical compression ratio is increased, the intake valve closing timing is retarded until reaching e _10, and the opening of the throttle valve 17 is gradually increased, and when it reaches e _10, it is fully opened.

FIG. 31 shows the intake valve closing timing, mechanical compression ratio when the target intake air amount is suddenly decreased from Q ₆ (point n) to Q ₁ (target operating point d ₃ ), as shown in FIG. Changes in actual compression ratio and throttle opening are shown. From FIG. 31, in this case, after the required intake air amount reaches the final target value Q ₁ (operating point e ₂ ), the retarding action of the intake valve closing timing is completed (operating point e ₁₀ ). It can be seen that the increasing action of the mechanical compression ratio is completed (target operating point d ₃ ). On the other hand, the actual compression ratio gradually decreases until the retarding action of the intake valve closing timing is completed (operating point e ₁₀ ), and then gradually increases. Further, the throttle opening is lowered from the fully opened state until the operating point reaches the operating point e ₃ on the same intake air amount surface Q ₁ , and then until the retarding action of the intake valve closing timing is completed (operating point e _The valve is gradually opened until ₁₀ ).

It should be noted that the demanded intake meet air amount throttle valve 17 opening of the three-dimensional forbidden entry area, that is, if a low load side forbidden entry area X ₂ when required intake air amount changes. In this case, the opening degree of the throttle valve 17 is changed to the above-described intrusion prevention surface, that is, just before entering the three-dimensional intrusion prohibition region, and then the mechanical compression ratio, intake valve closing timing, and throttle opening degree are changed. The operating point indicating the combination is changed without entering the three-dimensional intrusion prohibited area toward the operating point satisfying the required intake air amount.

  FIG. 32 is a routine for calculating a target operating point that can be reached after a predetermined time from the current operating point, that is, a target value for mechanical compression ratio, intake valve closing timing, and throttle opening. Is shown.

  In this routine, a target operating point that can be reached after a predetermined time is calculated every predetermined time. Therefore, the routine shown in FIG. 32 is executed by this predetermined interruption every hour. The predetermined time can be arbitrarily determined, but in the embodiment according to the present invention, the predetermined time is 8 msec. Therefore, in the embodiment according to the present invention, the target value calculation routine shown in FIG. 32 is executed every 8 msec, and the target operating point that can be reached after 8 msec from the current operating point is calculated every 8 msec.

  Referring to FIG. 32, first, at step 100, the required intake air amount GX is calculated. The required intake air amount GX is stored in advance in the ROM 32 as a function of, for example, the depression amount of the accelerator pedal 40 and the engine speed. Next, at step 101, a required operating point on the reference operating line W corresponding to the required intake air amount GX is calculated. Next, at step 102, it is determined whether or not the current operating point is the requested operating point. When the current operating point is the requested operating point, the processing cycle is completed. On the other hand, when the current operating point is not the required operating point, the routine proceeds to step 103, where it is determined whether or not the required intake air amount GX is larger than the intake air amount GA at the current operating point.

When GX> GA, that is, when the intake air amount should be increased, the routine proceeds to step 104, where the target operating point is determined as described with reference to FIGS. That is, in step 104, the target throttle opening degree corresponding to the required intake air amount GX is calculated. When the target throttle opening degree required operating point is located on the throttle full open plane Q ₆ normally fully opened. Next, at step 105, the intake valve closing timing that can be reached after a certain time is calculated, and then at step 106, the mechanical compression ratio that can be reached after a certain time is calculated.

  Next, at step 107, the target operating point is determined by the method described with reference to FIG. Next, at step 108, the target value of the mechanical compression ratio and the target value of the intake valve closing timing are calculated from the determined target operating point. The target value of the throttle opening is already calculated as the target throttle opening in step 104.

  On the other hand, when it is determined in step 103 that GX ≦ GA, that is, when the intake air amount should be reduced or when the intake air amount is the required intake air amount, the routine proceeds to step 109, based on FIGS. The target operating point is determined as described above. That is, at step 109, the intake valve closing timing that can be reached after a certain time is calculated, and then at step 110, the mechanical compression ratio that can be reached after a certain time is calculated.

  Next, at step 112, a target throttle opening satisfying the required intake air amount is calculated, and this target throttle opening is set as a target value of the throttle opening. However, when the throttle opening satisfying the required intake air amount GX falls within the intrusion prohibition region, the target throttle opening is set to the value on the intrusion prevention surface described above, and the mechanical compression ratio and the intake valve closing timing are set as the required operating points. The target throttle opening is changed along the intrusion prevention surface as it approaches.

Although not described so far, the same can occur when the required intake air amount increases. For example, if the required intake air amount increases when the operating point is located below the high load side intrusion prohibition region X ₁ in FIG. 13, the target throttle opening may be within the high load side intrusion prohibition region X ₁ . . At this time, the target throttle opening is set to a value on the reference operation surface including each reference operation line W set in advance for each same intake air amount surface, and the mechanical compression ratio and the intake valve closing timing are set as the required operation points. As the distance approaches, the target throttle opening is changed along this reference operation surface.

  FIG. 33 shows the variable compression ratio mechanism A, variable valve timing mechanism B, and the like so that the mechanical compression ratio, the intake valve closing timing, and the throttle opening are set to the target values calculated in the routine shown in FIG. A drive routine for driving the throttle valve 17 is shown. This routine is repeatedly executed when the engine is started.

Referring to FIG. 33, in step 200, the difference ΔIT (= IT ₀ −IT) between the target value IT ₀ of the intake valve closing timing and the current intake valve closing timing IT is calculated, and the target value CR _{0 of the} mechanical compression ratio is calculated. And the current mechanical compression ratio CR is calculated ΔCR (= CR ₀ −CR), and the difference Δθ (θ ₀ −θ) between the throttle opening target value θ ₀ and the current throttle opening θ is calculated. The

Then the proportional term E _p1 of the drive voltage for the variable valve timing mechanism B is calculated by multiplying the proportionality constant K _p1 to ΔIT In step 201, the drive for the variable compression ratio mechanism A is multiplied by the proportional constant K _p2 to ΔCR A proportional term E _{p2 of} voltage is calculated, and a proportional term E _p3 of driving voltage for the throttle valve 17 is calculated by multiplying Δθ by a proportional constant K _p3 .

Next, at step 202, ΔIT is multiplied by an integral constant K _i1 and this multiplication result (K _i1 · ΔIT) is multiplied to calculate the integral term E _i1 of the drive voltage for the variable valve timing mechanism B, and ΔCR is integrated with the integral constant K. The integral term E _i2 of the drive voltage for the variable compression ratio mechanism A is calculated by multiplying _i2 and multiplying the multiplication result (K _i2 · ΔCR), and Δθ is multiplied by an integral constant K _i3 to obtain the multiplication result ( By integrating (K _i3 · Δθ), the integral term E _i3 of the drive voltage for the throttle valve 17 is calculated.

Then differential term E _d1 of the drive voltage for the variable valve timing mechanism B is calculated by multiplying the derivative constant K _d1 to the difference between DerutaIT ₁ that is currently DerutaIT and previously calculated in step 203 (ΔIT-ΔIT _1), A differential term E _d2 of the driving voltage for the variable compression ratio mechanism A is calculated by multiplying the difference between the current ΔCR and the previously calculated ΔCR ₁ (ΔCR−ΔCR ₁ ) by a differential constant K _d2 , and the current Δθ and differential term E _d3 of the drive voltage for the throttle valve 17 is calculated by multiplying the derivative constant K _d3 to the difference between [Delta] [theta] ₁ calculated the last time (Δθ-Δθ _1).

Then the drive voltage E ₁ for the variable valve timing mechanism B is calculated by adding the differential term and the proportional term E _p1 in step 204 and the integral term E _i1 E _d1, derivative and proportional term E _p2 and the integral term E _i2 term The drive voltage E ₂ for the variable compression ratio mechanism A is calculated by adding E _d2, and the drive voltage E ₃ for the throttle valve 17 is added by adding the proportional term E _p3 , the integral term E _i3, and the differential term E _d3. Is calculated.

When the variable valve timing mechanism B, the variable compression ratio mechanism A, and the throttle valve 17 are driven according to the drive voltages E ₁ , E ₂ , and E ₃ , the intake valve closing timing, the mechanical compression ratio, and the throttle opening are sequentially set. It will change towards the changing target value.

  Incidentally, in the above embodiment, the current mechanical compression ratio detected by the relative position sensor 22 that detects the relative positional relationship between the crankcase 1 and the cylinder block 2 is the target value calculated in the routine shown in FIG. Thus, the variable compression ratio mechanism A is feedback controlled (in particular, PID control in the above embodiment). Therefore, if the relative position sensor 22 fails and the current mechanical compression ratio cannot be detected, the variable compression ratio mechanism A cannot be properly controlled.

For this reason, when the relative position sensor 22 fails, not only the operating point indicating the combination of the mechanical compression ratio, the intake valve closing timing and the throttle valve opening cannot be controlled as the target operating point, will invade the side forbidden entry area X ₁ and lower load forbidden entry area X _2, in some cases resulting in an aggravation of knocking generation and combustion.

The intake valve closing timing from the viewpoint of preventing the operating point from entering the high-load side forbidden entry area X ₁ and lower load forbidden entry area X ₂ as a minimum the mechanical compression ratio causes the most advanced angle, the throttle valve It is also conceivable to control the intake air amount only by 17, that is, to perform the same control as that of a normal internal combustion engine that does not perform the super high expansion ratio cycle. However, when the intake air amount is controlled only by the throttle valve 17 as described above, the fuel consumption is deteriorated due to an increase in pumping loss and a decrease in expansion ratio.

Meanwhile, as described with reference to FIGS. 10 and 11, the mechanical compression ratio, operating points indicating a combination of opening of the intake valve is closed and when the throttle valve is in the high load side forbidden entry on the outer edge of the region X ₁ By controlling the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 so as to move, the minimum fuel consumption can be obtained without causing knocking or torque fluctuation. Therefore, when the relative position sensor 22 has failed even mechanical compression ratio so as to move on the outer edge of the operating point is a high load side forbidden entry area X _1, controls the opening of the intake valve closing timing and the throttle valve 17 If this can be done, the fuel consumption can be minimized without causing knocking or torque fluctuation.

Here, in the high load side forbidden entry area X _1, the ignition timing in order to prevent the knocking occurs by the actual compression ratio is higher is made to retard, as a result, a torque variation occurs. Such torque fluctuation becomes larger as the distance from the high load side forbidden entry area X ₁ of the boundary surface in the high load side forbidden entry in region X ₁ (outer edge). Conversely, on the high load side forbidden entry area X ₁ of the boundary surface (outer edge) would only slight torque variation occurs. Such a slight torque fluctuation can be detected by the torque sensor 43.

Therefore, in the embodiment according to the present invention, basically, the mechanical compression ratio is the highest and the opening of the throttle valve 17 is increased within a range where the torque fluctuation detected by the torque sensor 43 is very small. The compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are controlled. In other words, in the embodiment according to the present invention, basically, the mechanical compression ratio, so that the operating point indicating the mechanical compression ratio and the intake valve closing timing reaches the solid line W ′ shown in FIGS. It can be said that the intake valve closing timing and the opening degree of the throttle valve 17 are controlled. In the following description, this solid line W ′ is referred to as a reaching target line. As can be seen from FIGS. 34 and 35, the reaching target line W ′ is on the throttle fully open surface Q ₆ on the side where the intake air amount is larger than the same intake air amount surface Q ₃ and is on the high load side intrusion prohibited region X. ₁ extends on the boundary surface ₁ and extends vertically downward on the right side surface S ₂ on the side where the intake air amount is smaller than the same intake air amount surface Q ₃ .

Next, how to control the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 when the relative position sensor 22 fails will be described. First, a case where the required intake air amount is reduced will be described with reference to FIGS. 36 to 38 are diagrams showing the control when the required intake air amount is reduced according to the embodiment of the present invention, and FIGS. 39 to 41 are diagrams when the control according to the embodiment of the present invention is performed. It is a figure for demonstrating an advantage. FIG. 37 shows the same intake air amount surface with the intake air amount Q ₄ , and FIG. 37 shows the same intake air amount surface with the intake air amount Q ₃ .

FIG. 36 shows a case where the required intake air amount is decreased from Q ₄ to Q ₃ when the mechanical compression ratio and the intake valve closing timing are at the n point. When the required intake air amount is decreased to Q ₃ , the mechanical compression ratio, the intake valve closing timing, and the opening of the throttle valve 17 toward the operating point f on the reaching target line W ′ satisfying the required intake air amount Q ₃ are opened. The degree will be controlled. That is, the intake valve closing timing is controlled to finally reach the intake valve closing timing corresponding to the operating point f based on the output of the valve timing sensor 23, and the opening of the throttle valve 17 is controlled by the throttle opening sensor. Based on the output of 24, the opening of the throttle valve 17 corresponding to the operating point f is finally reached. On the other hand, the mechanical compression ratio is the intake valve closing timing corresponding to the operating point f because the relative position sensor 22 that detects the mechanical compression ratio has failed as described above. In addition, when the opening degree of the throttle valve 17 is the opening degree of the throttle valve 17 corresponding to the operating point f, the mechanical compression ratio is finally reached such that only a small amount of torque fluctuation is detected by the torque sensor 43. To be controlled.

A specific control method when the required intake air amount is decreased to Q ₃ when the mechanical compression ratio and the intake valve closing timing are at the point n on the same intake air amount surface Q ₄ will be described. Since the relative position sensor 22 is out of order, when the actual operating point is at the n point, it is possible to detect the intake valve closing timing and the opening degree of the throttle valve 17 corresponding to the operating point n. Although it is possible, the mechanical compression ratio corresponding to the operating point n cannot be detected. Therefore, when the actual operating point is n, it is detected only that the operating point is somewhere on the broken line Z on the same intake air amount surface Q ₄ shown in FIGS. 36 and 37. become.

When the required intake air amount is reduced to Q ₃ when the mechanical compression ratio and the intake valve closing timing are at the point n, as shown in FIGS. 36 and 37, first, the intake valve closing timing and the throttle valve are reduced. Without changing the opening of 17, only the mechanical compression ratio is increased. That is, the operating point indicating the mechanical compression ratio and the intake valve closing timing is moved vertically upward from the point n on the same intake air amount surface Q ₄ shown in FIG.

When only the mechanical compression ratio is increased in this way, the current operating point eventually reaches the point g ₁ on the boundary surface of the high load side intrusion prohibited region X ₁ , and a small amount of torque fluctuation is detected by the torque sensor 43. Become so. Since it was grasped in advance the relationship between the opening degree of the mechanical compression ratio and the intake valve closing timing and the throttle valve 17 in the high load side forbidden entry area X ₁ of the boundary plane, the operating point is a high load side forbidden entry area When the point g ₁ on the boundary surface of X ₁ is reached, the current mechanical compression ratio can be grasped.

When the current operating point reaches the point g ₁ , the throttle valve 17 is then closed to the target opening required to set the intake air amount to the required intake air amount Q ₃ . In the present embodiment, the mechanical compression ratio is also increased at the same time. Here, since the operating speed of the throttle valve 17 is faster than the operating speed of the mechanical compression ratio, even if the opening degree of the throttle valve 17 is reduced and the mechanical compression ratio is increased simultaneously, the operating point is on the high load side. transitions without entering the forbidden entry area X _1.

As a result, when the opening degree of the throttle valve 17 reaches the target opening degree necessary for setting the intake air amount to the required intake air amount Q ₃ , the operating point is the same intake air amount surface Q as shown in FIG. The point g ₂ on ₃ is reached. The mechanical compression ratio at the operating point g ₂ is increased more than the mechanical compression ratio at the operating point g ₁ , and this increase range reduces the opening of the throttle valve 17 to change the intake air amount from Q ₃ to Q ₄ . It is equal to the increase when the mechanical compression ratio is increased at the maximum speed over the time required for the operation.

When the current operating point has reached the _two points g, intake valve closing timing and without changing the opening degree of the throttle valve 17, only the mechanical compression ratio is increased again. That is, the operating point indicating the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 is moved upward in the vertical direction from the point g _{2 on the} same intake air amount surface Q ₃ shown in FIG. When only the mechanical compression ratio is increased in this way, the current operating point eventually reaches the point g ₃ on the boundary surface of the high load side intrusion prohibited region X _{1, and} a slight amount of torque fluctuation is detected again by the torque sensor 43. Will come to be.

In this way, when the current operating point reaches the point g ₃ , the operating point is moved along the boundary surface of the high load side intrusion prohibited area X ₁ thereafter. That is, the intake valve closing timing is changed based on the output of the valve timing sensor 23 toward the intake valve closing timing corresponding to the operating point f. the opening degree of the throttle valve 17 is made to change so as to be located on the amount plane Q _3. At this time, the mechanical compression ratio is feedback controlled based on the output of the torque sensor 43. That is, when the torque fluctuation detected by the torque sensor 43 is 0, the torque fluctuation is increased, and when the torque fluctuation detected by the torque sensor 43 exceeds the minute amount, that is, the detected torque fluctuation is predetermined. When it becomes more than the reference torque fluctuation, it is reduced.

In the example described above, the intake valve closing timing and the throttle valve 17 without changing the degree of opening, the current when increased only mechanical compression ratio operating point always higher load side intrusion prohibition area X ₁ is While reaching the interface, there is a case where the mechanical compression ratio before reaching the boundary surface of the high load side forbidden entry area X ₁ is the maximum limit mechanical compression ratio forming the structural limit of the combustion chamber 5. In such a case, when the mechanical compression ratio reaches the maximum limit mechanical compression ratio, operating point subsequent control is carried out as it reaches the boundary surface of the high load side forbidden entry area X _1.

In the above-described example, when the operating point is changed from the n point to the g ₁ point, only the mechanical compression ratio is increased without changing the intake valve closing timing and the opening degree of the throttle valve 17. . However, since the actual compression ratio is increased only mechanical compression ratio is increased, the required intake air amount despite being made to reduce the Q _3, i.e. despite the deceleration request, the output torque is increased Will end up. Therefore, immediately after the required intake air amount is reduced, the opening of the throttle valve 17 may be reduced in addition to the increase in the mechanical compression ratio. As a result, the output torque can be reduced in accordance with the deceleration request, and thus a feeling of deceleration can be produced. However, if the opening degree of the throttle valve 17 is suddenly reduced at this time, the operating point may enter the low load side entry prohibition region X ₂ as described later. The decline is moderate.

Further, as described above, in the embodiment according to the present invention, the required intake air amount is calculated every predetermined time. FIGS. 36 to 38 show that the required intake air amount is decreased at a certain time. This shows a case where the required intake air amount calculated at times is Q ₃ and the detected required intake air amount thereafter maintained at Q ₃ . However, similar control is performed when the required intake air amount gradually changes.

For example, in the example shown in FIGS. 36 to 38, when the required intake air amount when the operating point reaches the _two points g was changed to Q ₂ are then shown from the operating point g ₂ in Figure 36 and towards the same intake air amount plane Q ₂ points on the f '(see FIG. 36), the mechanical compression ratio as described above, the opening degree of the intake valve closing timing and the throttle valve 17 is controlled.

Next, advantages of performing the control shown in FIGS. 36 to 38 will be described with reference to FIGS. 39 to 41. 39 to 41 show that when the control shown in FIGS. 36 to 38 is not performed, the required intake air amount is changed from Q ₄ to Q ₁ when the mechanical compression ratio and the intake valve closing timing are at the n point. The case where it was made to decrease is shown. In particular, in the example shown in FIG. 41 from FIG. 39, when the required intake air amount has been caused to decrease in Q _1, towards the operating point f on reaching target line W 'satisfying the required intake air quantity Q ₁ intake valve closing timing is made to retard at the maximum speed, the opening degree of the throttle valve 17 is made to decrease at maximum speed, also the mechanical compression ratio is toward the boundary surface of the high load side forbidden entry area X ₁ at the maximum speed (That is, toward the mechanical compression ratio at which the torque fluctuation detected by the torque sensor 43 becomes very small). 40 shows the same intake air amount surface where the intake air amount is Q ₄ , and FIG. 41 shows the same intake air amount surface where the intake air amount is Q ₁ .

In this way, when the operating point is at the n point, the intake valve closing timing is retarded at the maximum speed toward the operating point f, the opening of the throttle valve 17 is decreased at the maximum speed, and the mechanical compression ratio is increased. When increasing at the maximum speed, after a certain period of time, as shown in FIG. 40, the operating point indicating the mechanical compression ratio and the intake valve closing timing is higher than the n point and the intake valve closing timing is higher. The point g ₁ which is retarded from the point n is reached. Further, during this fixed period, in addition to changes in the mechanical compression ratio and the intake valve closing timing, the opening degree of the throttle valve 17 is changed at the maximum speed. Therefore, the mechanical compression ratio, the intake valve closing timing and the throttle valve are changed. The operating point g ₁ indicating the opening degree of the valve 17 is located on the same intake air amount surface Q ₁ located immediately below the operating point g ₁ on the same intake air amount surface Q ₄ shown in FIG. As a result, the intake air amount becomes equal to the required intake air amount.

As shown in FIG. 41, the mechanical compression ratio, the operating point that indicates the degree of opening of the intake valve closing timing and the throttle valve 17 reaches g _1, then, the intake valve closing timing is made to retard at the maximum speed and the mechanical compression ratio is made to increase at maximum speed, as a result, the intake valve closing timing is made to the most retarded to reach the operating point g _2. When the operating point g ₂ is reached, thereafter, only the mechanical compression ratio is increased until the torque fluctuation detected by the torque sensor 43 becomes very small.

Intake valve closing timing this way, the opening and the mechanical compression ratio of the throttle valve 17 is varied at the maximum speed, as can be seen from FIGS. 39 and 41, the operating point is in the low load side forbidden entry area X ₂ It will invade. This is because the higher is retarded and intake valve closing timing smaller the amount of intake air is lower load forbidden entry area X ₂ becomes wider. Therefore, before changing the operating point even when deviated from the low load side forbidden entry area X _2, or to reduce the opening degree of the throttle valve 17 to reduce the intake air amount, the intake valve is closed If the operating point is changed by retarding the timing, the operating point may enter the low load side intrusion prohibition region X ₂ depending on the value of the mechanical compression ratio.

On the other hand, according to the embodiment of the present invention, as shown in FIGS. 36 to 38, when the required intake air amount is decreased, the mechanical compression ratio is first changed without changing the intake valve closing timing. Is increased. Then, the maximum mechanical compression ratio that reaches the highest mechanical compression ratio within a range in which the torque fluctuation greater than the reference torque fluctuation is not detected by the torque sensor 43 or cannot increase the mechanical compression ratio further on the mechanism of the variable compression ratio mechanism. After reaching the ratio, the change of the intake valve closing timing is started. This first mechanical compression ratio is increased as would be the operating point is moved always in a direction away from the low-load side forbidden entry area X _2. Therefore, it is possible to suppress the operating point invades the lower load forbidden entry area X _2.

Next, a case where the required intake air amount is increased will be described with reference to FIGS. 42 to 45 are diagrams showing the control when the required intake air amount is increased according to the embodiment of the present invention, and FIGS. 46 to 49 are the cases when the control according to the embodiment of the present invention is performed. It is a figure for demonstrating an advantage. 43 shows the same intake air amount surface where the intake air amount is Q ₃ , FIG. 44 shows the same intake air amount surface where the intake air amount is between Q ₄ and Q ₅ , and FIG. The same intake air amount surface where the intake air amount is Q ₅ is shown.

FIG. 42 shows a case where the required intake air amount is increased from Q ₃ to Q ₅ when the mechanical compression ratio and the intake valve closing timing are at point m on the same intake air amount surface Q ₃ . When the required intake air amount is increased to Q ₅ , the mechanical compression ratio, the intake valve closing timing, and the opening of the throttle valve 17 are increased toward the operating point h on the reaching target line W ′ that satisfies the required intake air amount Q _5. The degree will be controlled. That is, the intake valve closing timing is controlled to finally reach the intake valve closing timing corresponding to the operating point h based on the output of the valve timing sensor 23, and the opening of the throttle valve 17 is controlled by the throttle opening sensor. Based on the output of 24, the opening of the throttle valve 17 corresponding to the operating point h is finally reached. On the other hand, the mechanical compression ratio is the intake valve closing timing corresponding to the operating point h because the relative position sensor 22 that detects the mechanical compression ratio has failed as described above. In addition, when the opening degree of the throttle valve 17 is the opening degree of the throttle valve 17 corresponding to the operating point h, the mechanical compression ratio is finally reached such that only a small amount of torque fluctuation is detected by the torque sensor 43. To be controlled.

A specific control method when the required intake air amount is increased to Q ₅ when the mechanical compression ratio and the intake valve closing timing are at the point m on the same intake air amount surface Q ₃ will be described. Since the relative position sensor 22 is out of order, when the actual operating point is at point m, it is possible to detect the intake valve closing timing and the opening degree of the throttle valve 17 corresponding to the operating point m. Although it is possible, the mechanical compression ratio corresponding to the operating point m cannot be detected.

When the required intake air amount is increased to Q ₅ when the operating point is at the point m, first, the intake valve closing timing and the opening degree of the throttle valve 17 are changed as shown in FIGS. Only the mechanical compression ratio is reduced. That is, the operating point indicating the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 is moved vertically downward from the point m on the same intake air amount surface Q ₃ shown in FIG.

If only the mechanical compression ratio is reduced in this way, the mechanical compression ratio eventually reaches the minimum limit mechanical compression ratio at which the compression ratio cannot be further reduced by the mechanism, and the current operating point is shown in FIGS. The indicated i ₁ point is reached. When the minimum limit mechanical compression ratio is reached, the drive motor 59 can no longer rotate, and therefore the load on the drive motor 59 increases, thereby grasping that the mechanical compression ratio has reached the minimum limit mechanical compression ratio. can do.

When the current operating point reaches i ₁ , the intake valve closing timing is advanced toward the intake valve closing timing corresponding to the operating point h while the mechanical compression ratio is maintained at the minimum limit mechanical compression ratio. At the same time, the opening degree of the throttle valve 17 is increased toward the opening degree of the throttle valve 17 corresponding to the operating point h. 42 and 43, the throttle valve whose opening degree of the throttle valve 17 corresponds to the operating point h before the intake valve closing timing reaches the intake valve closing timing corresponding to the operating point h. The opening reaches 17, that is, fully opened, and the operating point at this time is i ₂ . In particular, in the example shown in FIGS. 42 and 43, the operating point i ₂ is located on the same intake air amount surface between Q ₄ and Q ₅ shown in FIG. The mechanical compression ratio at the operating point i ₂ is the minimum limit mechanical compression ratio.

Even after the opening degree of the throttle valve 17 reaches the opening degree of the throttle valve 17 corresponding to the operating point h, the intake valve closing timing remains at the operating point h while the mechanical compression ratio is maintained at the minimum limit mechanical compression ratio. Is advanced toward the intake valve closing timing corresponding to. At this time, the operating point moves on the throttle fully open surface Q ₆ . When the intake valve closing timing is advanced, the intake valve closing timing eventually reaches the intake valve closing timing corresponding to the operating point h, and the operating point at this time is the same intake air amount surface shown in FIG. This is the point i ₃ on Q ₅ . The mechanical compression ratio at the operating point i ₃ is also the minimum limit mechanical compression ratio.

Thus, when the intake valve closing timing reaches the intake valve closing timing corresponding to the operating point h, and the opening degree of the throttle valve 17 reaches the opening degree of the throttle valve 17 corresponding to the operating point h, the intake valve closing timing is reached. Only the mechanical compression ratio is increased without changing the valve timing and the opening degree of the throttle valve 17. That is, the operating point indicating the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 is moved upward in the vertical direction from the i ₃ point on the same intake air amount surface Q ₅ shown in FIG.

As described above, when only the mechanical compression ratio is increased, the current operating point eventually reaches a point on the boundary surface of the high load side intrusion prohibited region X _{1 so that} a small amount of torque fluctuation is detected by the torque sensor 43. Finally, the operating point h on the reaching target line W ′ is reached.

In the above-described example, the mechanical compression ratio is first reduced to the minimum limit mechanical compression ratio without changing the intake valve closing timing and the opening degree of the throttle valve 17, but the mechanical compression ratio is the minimum limit mechanical compression. in some cases the operating point before reaching the ratio reaches the boundary of the low-load side forbidden entry area X _2. In such a case, the operating point when it reaches the boundary of the low-load side forbidden entry area X _2, the mechanical compression ratio is subsequent control is carried out as it reaches the minimum limit mechanical compression ratio.

In the above example, when the operating point is changed from the point m to the point i ₁ , only the mechanical compression ratio is reduced without changing the intake valve closing timing and the opening degree of the throttle valve 17 first. Yes. However, if only the mechanical compression ratio is decreased, the output torque will be decreased although the required intake air amount is increased to Q ₅ , that is, there is an acceleration request. Therefore, immediately after the required intake air amount is increased, the opening of the throttle valve 17 may be increased in addition to the decrease in the mechanical compression ratio. As a result, the output torque can be increased in accordance with the acceleration request, and thus a sense of acceleration can be obtained. However, if the opening degree of the throttle valve 17 is suddenly increased at this time, the operating point may enter the high load side entry prohibition region X ₁ as will be described later. Is moderate.

Furthermore, as described above, in the embodiment according to the present invention, the required intake air amount is calculated every predetermined time. FIGS. 42 to 45 show that the required intake air amount is increased at a certain time. This shows a case where the required intake air amount calculated at times is Q ₅ and the detected intake air amount detected thereafter is maintained at Q ₅ . However, similar control is performed when the required intake air amount gradually changes.

The advantages of performing the control shown in FIGS. 42 to 45 will be described with reference to FIGS. 46 to 49. FIG. FIGS. 46 to 49 show cases where the required intake air amount is increased from Q ₃ to Q ₄ when the operating point is at the point m when the control shown in FIGS. 42 to 45 is not performed. ing. In particular, in the example shown in FIG. 49 from FIG. 46, when the required intake air amount has been made to increase the Q _4, toward the operating point h on reaching target line W 'satisfying the required intake air quantity Q ₄ The case where the intake valve closing timing is advanced at the maximum speed and the opening degree of the throttle valve 17 is increased at the maximum speed is shown. At this time, the mechanical compression ratio is controlled so as to be decreased when the torque fluctuation detected by the torque sensor 43 becomes equal to or greater than the reference torque fluctuation. Note that FIG. 47 is the intake air amount indicates the same intake air amount plane of Q _3, Figure 48 is identical intake air amount plane between the intake air amount of Q ₃ and Q _4, Figure 49 is the intake air amount It shows the same intake air amount plane of Q _4.

In this way, when the operating point indicating the mechanical compression ratio and the intake valve closing timing is at the m point, the intake valve closing timing is advanced at the maximum speed toward the operating point h, and the opening degree of the throttle valve 17 is increased. When the maximum speed is increased, after a certain period of time, as shown in FIG. 48, the operating point is that the intake valve closing timing is earlier than the m point and the opening of the throttle valve 17 is larger than the m point. The amount moves to point i ₁ on the same intake air amount surface between Q ₃ and Q ₄ . Since this operating point i ₁ slightly enters the high load side intrusion prohibition region X ₁ and the torque fluctuation exceeds the reference torque fluctuation, the mechanical compression ratio is maximum after the operating point reaches i _1. It will be reduced at speed.

After the current operating point has reached the _point i, the intake valve closing timing is advanced at the maximum speed, increasing the degree of opening of the throttle valve 17 at a maximum speed, reduce the mechanical compression ratio at the maximum speed Then, after a certain period of time, the intake valve closing timing reaches the intake valve closing timing corresponding to the operating point h, and the opening degree of the throttle valve 17 becomes the opening degree of the throttle valve 17 corresponding to the operating point h. To reach. The operating point at this time is a point i ₂ on the same intake air amount surface Q ₄ shown in FIG. When the operating point i ₂ is reached, then only the mechanical compression ratio is decreased until the torque fluctuation detected by the torque sensor 43 becomes smaller than the reference torque fluctuation.

As described above, when the intake valve closing timing and the opening degree of the throttle valve 17 are changed at the maximum speed, the operating point enters the high load side intrusion prohibited region X _{1 as} can be seen from FIGS. It will be. This is because the higher and the intake valve closing timing more the intake air amount is advanced high load forbidden entry area X ₁ becomes wider. Accordingly, even if before changing the operating point is out of the high-load side forbidden entry area X _1, or increasing the opening degree of the throttle valve 17 so as to increase the intake air amount, the intake valve is closed If the operating point is changed by advancing the timing, the operating point may enter the high load side intrusion prohibition region X ₁ depending on the value of the mechanical compression ratio.

On the other hand, according to the embodiment of the present invention, as shown in FIGS. 42 to 45, when the required intake air amount is decreased, the mechanical compression ratio is first changed without changing the intake valve closing timing. Is reduced. Thereafter, the minimum mechanical compression at which the lowest mechanical compression ratio is reached within a range in which no torque fluctuation greater than the reference torque fluctuation is detected by the torque sensor 43 or the mechanical compression ratio cannot be further reduced due to the mechanism of the variable compression ratio mechanism. The change of the intake valve closing timing of Achi that has reached the ratio is started. This first mechanical compression ratio is made to decrease as would be the operating point is moved always in a direction away from the high load side forbidden entry area X _1. Therefore, it is possible to suppress the operating point invades the high load side forbidden entry area X _1.

  50 to 52 show a driving routine for driving the variable compression ratio mechanism A, the variable valve timing mechanism B, and the throttle valve 17 when the relative position sensor 22 fails. This routine is a collection of the routine for calculating the target value shown in FIG. 32 and the drive routine shown in FIG. 33 when the relative position sensor 22 is not out of order. It is executed by every interrupt.

Current required intake air amount GX _n first, at step 300 that the reference is calculated to FIG. 50. Then, the current required intake air amount GX _n At step 301, whether substantially the same out the required intake air amount GX _n-1 of the last, that is, determines whether there is no change in the required intake air amount, the current when the required intake air amount GX _n is determined to be substantially identical to the required intake air amount GX _n-1 of the previous _{(GX n ≒ GX n-1} ) proceeds to step 302.

In step 302, it is determined whether or not the deceleration flag Xd is 1. The deceleration flag Xd is set to 1 after the required intake air amount is reduced until the operating point reaches the operating point on the reaching target line W ′ corresponding to the reduced required intake air amount. In this case, the flag is set to 0. Explaining with reference to FIGS. 36 to 38, the deceleration flag Xd is set to 1 until the current operating point reaches the point f after the required intake air amount decreases to Q ₃ , and after reaching the point f. Reset to zero. If it is determined in step 302 that the deceleration flag Xd is 0, that is, if it is determined that the operating point is not being changed due to a decrease in the required intake air amount, the routine proceeds to step 303.

In step 303, it is determined whether or not the acceleration flag Xa is 1. The acceleration flag Xa is set to 1 during the period from when the required intake air amount is increased to when the operating point reaches the operating point on the reaching target line W ′ corresponding to the increased required intake air amount. In this case, the flag is set to 0. With referring to Figure 45 will be described from FIG 42, the acceleration flag Xa current operating point from the required intake air amount is increased to Q ₅ is 1 to reach the point h, after reaching the point h Reset to zero. If it is determined in step 303 that the acceleration flag Xa is 0, that is, if it is determined that the operating point is not being changed due to an increase in the required intake air amount, the routine proceeds to step 304. Note that the case where the routine proceeds to step 304 is a case where the engine operating state is in a steady operating state because there is no change in the required intake air amount and the operating point is not being changed as the required intake air amount increases or decreases. Means.

In step 304, the opening degree of the corresponding throttle valve 17 to the operating point on the goals line W 'to meet the current demand intake air amount GX _n is calculated as the target opening degree theta _0, the current throttle opening theta And the difference Δθ (= θ ₀ −θ) between the target opening degree θ ₀ and the target opening degree θ ₀ is calculated. Next, at step 305, the intake valve closing timing corresponding to the operating point on the reaching target line W ′ that satisfies the current required intake air amount GX _n is calculated as the target valve closing timing IT ₀ , and the current intake valve A difference ΔIT (= IT ₀ −IT) between the valve closing timing IT and the target valve closing timing IT ₀ is calculated.

Next, at step 306, the drive voltage E ₃ for the throttle valve 17 is calculated based on Δθ calculated at step 304 by the method shown at step 201 to step 204 in FIG. 33, and ΔIT calculated at step 305 is calculated. Based on this, the driving voltage E ₁ for the variable valve timing mechanism B is calculated by the method shown in step 201 to step 204 in FIG. The variable valve timing mechanism B and the throttle valve 17 are driven according to the drive voltages E ₁ and E ₃ .

Next, at step 307, it is determined whether or not the torque fluctuation TR detected by the torque sensor 43 is substantially zero. In step 307, if it is determined that the torque variation TR is approximately 0, that is, when the operating point is a high load side forbidden entry area X ₁ out away from the boundary of the high load side forbidden entry area X ₁ Then go to step 308. In step 308, the current drive voltage E _{2 (n)} for the variable compression ratio mechanism A is set to a value obtained by adding a predetermined value ΔE ₂ to the previous drive voltage E _{2 (n−1)} , and the mechanical compression ratio is increased.

On the other hand, if it is determined in step 307 that the torque fluctuation Tr is not zero, the process proceeds to step 309. In step 309, it is determined whether or not the torque fluctuation TR is greater than or equal to the reference torque fluctuation TRs. In step 309, if it is determined that the torque variation TR is the reference torque fluctuation TRs above, that is, when the operating point is invaded to the high load side forbidden entry area X ₁ proceeds to step S310. In step S310, the current drive voltage E _{2 (n)} for the variable compression ratio mechanism A is set to a value obtained by subtracting the predetermined value ΔE ₂ from the previous drive voltage E _{2 (n−1)} , and the mechanical compression ratio is decreased. . On the other hand, in step 309, if it is determined that the torque variation Tr is smaller than the reference torque fluctuation TRs, i.e. if the operating point is located on the high load side forbidden entry area X ₁ of the boundary on the current drive voltage E _{2 (n)} remains the same as the previous drive voltage E _{2 (n-1)} .

On the other hand, if the required intake air amount has decreased, it is determined in step 301 that the current required intake air amount GX _n is different from the previous required intake air amount GX _n−1 , and the process proceeds to step 313. Whether In step 313 the current required intake air amount GX _n is smaller than the required intake air amount GX _n-1 of the previous time is determined. If the required intake air amount has decreased, it is determined that the current required intake air amount GX _n is smaller than the previous required intake air amount GX _n−1 , and the routine proceeds to step 314 where the deceleration flag Xd is set to 1. .

Next, at step 315, it is judged if the arrival flag Xga is 0 or not. Reaching flag Xga is 1 when the operating point by increasing only the mechanical compression ratio from being made to reduce the required amount of intake air reaches the high load side forbidden entry area X ₁ of the boundary surface, before reaching Is a flag set to 0. Immediately after the required intake air amount has decreased, the arrival flag Xga is set to 0. Therefore, in step 315, it is determined that the arrival flag Xga is 0, and the process proceeds to step 316.

Whether the step 316 the torque fluctuation TR is larger than 0, i.e. whether the operating point has reached a high load side forbidden entry area X ₁ of the boundary plane it is determined. If it is determined that the torque fluctuation TR is 0, the process proceeds to step 317. In step S317, as in step 308, the current drive voltage E _{2 (n)} for the variable compression ratio mechanism A is set to a value obtained by adding a predetermined value ΔE ₂ to the previous drive voltage E _{2 (n−1).} The ratio is increased. Thereby, in the example shown in FIGS. 36 and 37, the operating point is changed from the n point to the g ₁ point. Thereafter, when the operating point reaches the boundary surface of the high load side prohibited region X ₁ due to an increase in the mechanical compression ratio, that is, when the operating point reaches the point g ₁ in the examples shown in FIGS. In the routine, it is determined in step 316 that the torque fluctuation TR is larger than 0, and the process proceeds from step 316 to step 318. In step 318, the arrival flag Xga is set to 1.

When the arrival flag Xga is set to 1, in the next routine, it is determined in step 315 that the arrival flag Xga is not 0, and the process proceeds to steps 319 and 320. In steps 319 and 320, Δθ and ΔIT are calculated in the same manner as in steps 304 and 305, respectively, and the process proceeds to step 321. In step 321, whether Δθ and ΔIT are substantially 0 and whether the torque fluctuation TR is larger than 0 and smaller than the reference torque fluctuation TRs, that is, the operating point is f point in the example shown in FIGS. 36 to 38. It is determined whether or not it has been reached. If any of these requirements is not satisfied in step 321, the process proceeds to step 322. In step 322, the drive voltage E ₃ for the throttle valve 17 is calculated based on Δθ calculated in step 319 as in step 306. Thereby, in the example shown in FIGS. 36 to 38, the opening degree of the throttle valve 17 is changed toward the opening degree of the throttle valve 17 corresponding to the operating point f.

Next, at step 323, it is determined whether or not the torque fluctuation TR detected by the torque sensor 43 is zero. If it is determined that the torque fluctuation TR is zero, the routine proceeds to step 324. In step 324, the current drive voltage E _{2 (n)} for the variable compression ratio mechanism A is calculated in the same manner as in step 309, and the mechanical compression ratio is increased.

On the other hand, if it is determined in step 323 that the torque fluctuation TR is not zero, the routine proceeds to step 325. In step 325, the drive voltage E ₁ for the variable valve timing mechanism B is calculated based on ΔIT calculated in step 320 in the same manner as in step 306. Thereby, in the example shown in FIGS. 36 to 38, the intake valve closing timing is changed toward the intake valve closing timing corresponding to the operating point f. Next, at step 326, it is determined whether or not the torque fluctuation TR detected by the torque sensor 43 is equal to or greater than the reference torque fluctuation TRs. If it is determined that the torque fluctuation TR is greater than or equal to the reference torque fluctuation TRs, the routine proceeds to step 327, where the current drive voltage E _{2 (n)} for the variable compression ratio mechanism A is calculated as in step 310, and mechanical compression is performed. The ratio is reduced.

  As a result of repeating the control from step 322 to step 327, when the operating point reaches the operating point on the reaching target line W ′ corresponding to the required intake air amount, that is, the current operation in the example shown in FIGS. When the point reaches the operating point f, in the next routine, it is determined in step 321 that Δθ and ΔIT are substantially 0 and the torque fluctuation TR is larger than 0 and smaller than the reference torque fluctuation TRs. move on. In step 328, the arrival flag Xga and the deceleration flag Xd are reset to zero.

Conversely, if the required intake air amount has increased, it is determined in step 313 that the current required intake air amount GX _n is greater than the previous required intake air amount GX _n−1 and the routine proceeds to step 330. In step 330, the acceleration flag Xa is set to 1.

Next, at step 331, it is judged if the arrival flag Xgb is zero. By reaching flag Xgb is to reduce only the mechanical compression ratio from being made to reduce the required amount of intake air, when the operating point has reached the low load side forbidden entry area X ₂ of the boundary plane or the mechanical compression ratio is the minimum limit This flag is set to 1 when the mechanical compression ratio is reached, and is set to 0 before reaching the mechanical compression ratio. Immediately after the required intake air amount increases, the arrival flag Xgb is set to 0. Therefore, it is determined in step 331 that the arrival flag Xgb is 0, and the process proceeds to step 332.

In step 332, it is determined whether or not the torque fluctuation TR detected by the torque sensor 43 is larger than 0, that is, whether or not the operating point has reached the boundary surface of the low load side prohibited region X _2. Then, it is determined whether or not the mechanical compression ratio has reached the minimum limit mechanical compression ratio. If it is determined in step 332 that the torque fluctuation TR is 0 and it is determined in step 333 that the mechanical compression ratio has not reached the minimum limit mechanical compression ratio, the routine proceeds to step 334. In step 334, as in step 310, the current drive voltage E _{2 (n)} for the variable compression ratio mechanism A is set to a value obtained by subtracting a predetermined value ΔE ₂ from the previous drive voltage E _{2 (n-1).} Is reduced. Thereby, in the example shown in FIGS. 42 and 43, the operating point is changed from m point to i ₁ point. Thereafter, when the operating point reaches the boundary surface of the low load side prohibited region X ₂ due to the increase of the mechanical compression ratio or the mechanical compression ratio reaches the minimum limit mechanical compression ratio, the process proceeds from step 332 or step 333 to step 335. . In step 345, the arrival flag Xgb is set to 1.

When the arrival flag Xgb is set to 1, in the next routine, it is determined in step 331 that the arrival flag Xgb is not 0, and the process proceeds to steps 336 and 337. In steps 336 and 337, Δθ and ΔIT are calculated in the same manner as in steps 304 and 305, respectively, and the process proceeds to step 338. In step 338, it is determined whether or not Δθ and ΔIT are substantially 0, that is, whether or not the operating point has reached point i ₃ in the examples shown in FIGS. If it is determined in step 338 that at least one of Δθ and ΔIT is not 0, the process proceeds to step 339. In step 339, the drive voltage E ₃ for the throttle valve 17 and the drive voltage E ₁ for the variable valve timing mechanism B are calculated based on Δθ calculated in step 336 and ΔIT calculated in step 337 as in step 306. . As a result, the operating point is changed toward the point i ₃ in the example shown in FIGS.

Thereafter, when the operating point reaches the point i ₃ in the example shown in FIGS. 36 to 38, it is determined in the next routine that Δθ and ΔIT are substantially 0 in step 338, and the process proceeds to step 340. In step 340, it is determined whether or not the torque fluctuation TR detected by the torque sensor 43 is 0. If it is determined that the torque fluctuation TR is 0, the variable compression ratio is determined in step 341 as in step 308. The current drive voltage E _{2 (n)} for the mechanism A is calculated, and the mechanical compression ratio is increased. As a result, the operating point reaches the high load side prohibition region X ₁ of the boundary plane, the following routine is determined that there is not zero torque variation TR in step 340, the process proceeds to step 342. In step 342, the arrival flag Xgb and the acceleration flag Xa are reset to zero.

Next, a method for diagnosing a failure of the relative position sensor 22 will be described. As described with reference to FIGS. 10 to 31, when the relative position sensor 22 has not failed, the operating points indicating the mechanical compression ratio and the intake valve closing timing are in the intrusion prohibited areas X ₁ and X ₂ . The mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 are controlled so as not to enter. Therefore, when the relative position sensor 22 is not out of order, the torque fluctuation detected by the torque sensor 43 is always almost zero or smaller than the reference torque fluctuation.

However, when the relative position sensor 22 breaks down, the operating point indicating the mechanical compression ratio and the intake valve closing timing cannot be accurately grasped, so that the operating point enters the intrusion prohibited areas X ₁ and X ₂ . In this case, the torque variation greater than the reference torque variation is detected by the torque sensor 43. Therefore, in the present embodiment, when the mechanical compression ratio, the intake valve closing timing, and the opening degree of the throttle valve 17 shown in FIGS. When the torque fluctuation is detected, it is determined that the relative position sensor 22 is out of order, and the control shown in FIGS. 36 to 38 and FIGS. 42 to 45 is performed.

Incidentally, in the above embodiment, the variable valve is set so that the current intake valve closing timing detected by the valve timing sensor 23 for detecting the intake valve closing timing becomes the target value calculated by the routine shown in FIG. The timing mechanism B is feedback controlled. Therefore, if the valve timing sensor 23 fails and the current intake valve closing timing cannot be detected, the variable valve timing mechanism B cannot be properly controlled. For this reason, even when the valve timing sensor 23 fails, the operating point enters the high load side intrusion prohibition region X ₁ and the low load side intrusion prohibition region X ₂ , causing knocking and deterioration of combustion. There is a case.

  Accordingly, in the embodiment according to the present invention, the intake valve closing timing is calculated by dividing the intake system of the internal combustion engine into elements such as a throttle valve, an intake pipe, an intake valve and the like, modeling each element, and expressing it by a mathematical expression. The intake valve closing timing is calculated using the valve closing timing estimation model obtained by the above equation. When the valve timing sensor 23 fails, the variable valve timing mechanism B is calculated based on the intake valve closing timing calculated by the valve closing timing estimation model. Is going to be feedback controlled. Hereinafter, the valve closing timing estimation model M10 will be described.

As shown in FIG. 53, the valve closing timing estimation model M10 includes a throttle model M11, an intake pipe model M12, and an intake valve model M13.
In the throttle model M11, the opening degree of the throttle valve 19 (throttle valve opening degree) θt detected by the throttle opening degree sensor 24 and the atmospheric temperature around the internal combustion engine detected by the intake air temperature sensor 44 (or the intake pipe 16). The temperature of the air sucked into the air) Ta, the atmospheric pressure around the internal combustion engine detected by the atmospheric pressure sensor 45 (or the pressure of the air sucked into the intake pipe 16) Pa, and the air flow detected by the air flow meter 18. The air flow rate passing through the meter 18 (note that the air flow rate passing through the air flow meter 18 can be approximated to the air flow rate passing through the throttle valve 17 and is hereinafter referred to as “the throttle valve passing air flow rate”) mt. By substituting the input parameter values into the model equation of the throttle model M11, which will be described later, the intake pipe Pressure within minutes (hereinafter, "the intake pipe pressure" referred) Pm is calculated. The intake pipe pressure Pm calculated by the throttle model M11 is input to the intake pipe model M12 and the intake valve model M13.

The model formula of the throttle model M11 will be described with reference to FIG. A throttle as shown in FIG. 54, where the pressure of the gas upstream of the throttle valve 17 is the atmospheric pressure Pa, the temperature of the gas upstream of the throttle valve 17 is the atmospheric temperature Ta, and the pressure of the gas downstream of the throttle valve 17 is the intake pipe pressure Pm. Applying the law of conservation of mass, law of conservation of energy and law of conservation of momentum to the model of the valve 17, and further using the equation of state of gas, the definition of specific heat ratio, and the Meyer's relational expression, the following formula (1) is obtained. It is done.

  Here, μt in the equation (1) is a flow coefficient in the throttle valve, which is a function of the throttle valve opening θt, and is thus determined from a map as shown in FIG. In addition, At indicates the opening cross-sectional area of the throttle valve, which is a function of the throttle valve opening θt, and is determined from a map as shown in FIG. Note that μt · At obtained by collecting the flow coefficient μt and the opening cross-sectional area At may be obtained from one throttle map from the throttle valve opening θt. R is a constant related to the gas constant, and is actually a value obtained by dividing the gas constant by the mass Mmol of gas (air) per mol.

Φ (Pm / Pa) is a function shown in the following formula (2), and κ in the formula (2) is a specific heat ratio (a constant value). Since this function Φ (Pm / Pa) can be expressed in a graph as shown in FIG. 56, such a graph is stored as a map in the ROM 32 of the ECU 30 and is actually calculated using the equation (2). Alternatively, the value of Φ (Pm / Pa) may be obtained from the map.

Then, the following equation (3) of the throttle model is obtained by modifying the equation (1) calculated in this way. In the throttle model M11, the equation (3) includes the flow coefficient μt in the throttle valve obtained from the throttle valve opening θt, the opening cross-sectional area At of the throttle valve, the atmospheric temperature Ta, the atmospheric pressure Pa, and the air passing through the throttle valve. By inputting the flow rate mt, the intake pipe pressure Pm is calculated.

  The intake pipe model M12 includes a throttle valve passage air flow rate mt detected by the air flow meter 18, an intake pipe pressure Pm calculated by the throttle model M11, and an ambient temperature Ta around the internal combustion engine detected by the intake temperature sensor 44. Are substituted into the model equation of the intake pipe model M12, which will be described later, and the flow rate of air flowing into the combustion chamber 5 per unit time (hereinafter referred to as “in-cylinder intake”). The value mc · Tm obtained by multiplying the air flow rate mc ”) and the temperature of the air in the intake pipe portion 23 (hereinafter referred to as“ intake pipe temperature Tm ”) is calculated. The value mc · Tm calculated by the intake pipe model M12 is input to the intake valve model M30.

The model formula of the intake pipe model M12 will be described with reference to FIG. Assuming that the total amount of gas in the intake pipe portion (total air amount) is M, the amount of time change of the gas energy M, Cv, and Tm in the intake pipe portion is determined from the energy of the gas flowing into the intake pipe portion and the intake pipe portion. It is equal to the difference from the energy of the gas that flows out. For this reason, if the temperature of the gas flowing into the intake pipe portion is the atmospheric temperature Ta and the temperature of the gas flowing out from the intake pipe portion is the intake pipe temperature Tm, the following equation (4) is obtained from the energy conservation law. From (4) and the gas equation of state (Pm · Vm = M · R · Tm), Equation (5) is obtained. In Equation (5), Vm is a constant equal to the volume of the intake branch pipe 11, the surge tank 12, the intake duct 14 and the like (intake pipe part) from the throttle valve 17 to the intake valve 7.

Then, the equation (6) of the intake pipe model M12 is obtained by modifying the equation (5) calculated in this way. In the intake pipe model M12, the cylinder intake air flow rate mc and the intake pipe internal temperature Tm are obtained by inputting the throttle valve passing air amount mt, the intake pipe internal pressure Pm, and the atmospheric temperature Ta into the model equation (6). Is multiplied by mc · Tm.

  The intake valve model M13 receives the intake pipe pressure Pm calculated by the throttle model M11, the value mc · Tm calculated by the intake pipe model M12, and the atmospheric temperature Ta, and the values of these input parameters are input. The intake valve closing timing IVC is calculated by substituting it into a model formula of an intake valve model M13 described later.

  The model formula of the intake valve model M13 will be described with reference to FIG. In general, the cylinder charge air amount Mc, which is the amount of air charged in the combustion chamber 5 when the intake valve 7 is closed, is determined when the intake valve 7 is closed (when the intake valve is closed). , Proportional to the pressure in the combustion chamber 5 when the intake valve 7 is closed. Further, the pressure in the combustion chamber 5 when the intake valve 7 is closed can be regarded as being equal to the pressure of the gas upstream of the intake valve 7, that is, the intake pipe pressure Pm. Therefore, the cylinder charge air amount Mc can be approximated as being proportional to the intake pipe pressure Pm.

Here, an average of the total air flow rate flowing out from the intake pipe portion per fixed time (for example, a crank angle of 720 °), or all from the intake pipe portion per fixed time (for example, a crank angle of 720 °) If the cylinder intake air flow rate mc is obtained by dividing the amount of air sucked into the combustion chamber 5 of the cylinder by the predetermined time into the cylinder intake air flow rate mc, the cylinder intake air amount Mc is proportional to the intake pipe pressure Pm. It is considered that the air flow rate mc is also proportional to the intake pipe pressure Pm. From this, the following formula (7) is obtained based on the theory and empirical rules.

  In actual operation, the intake pipe temperature Tm may change greatly during transient operation. Therefore, Ta / Tm derived based on theory and empirical rule is multiplied as a correction for this. Further, a in equation (7) is a proportional coefficient, and b is a conforming value representing the burnt gas remaining in the combustion chamber 5 (the amount of burnt gas remaining in the combustion chamber 5 when the exhaust valve 8 is closed). This is considered to be divided by a time ΔT180 ° described later).

Here, a and b are values determined from the intake valve closing timing IVC. Therefore, the equation (7) can be expressed as Equation (8) using the function f _c. The function f _c is derived based on theory and empirical rules, and changes as shown in FIG. 60 with respect to the intake valve closing timing IVC, for example.

Then, the equation (8) of the intake valve model M13 is obtained by modifying the equation (8) calculated in this way. In the intake valve model M13, a value mc · Tm obtained by multiplying the intake pipe pressure Pm, the in-cylinder intake air flow rate mc, and the intake pipe temperature Tm, and the atmospheric temperature Ta are input to the model equation (9). Then, the intake valve closing timing IVC is calculated.

  As described above, in the embodiment according to the present invention, even when the valve timing sensor 23 fails, the current intake valve closing timing is calculated by calculating the intake valve closing timing IVC using the valve closing timing estimation model M10. The timing can be grasped relatively accurately, and therefore the variable valve timing mechanism B can be appropriately feedback controlled.

  In the above description, a simple example of the valve closing timing estimation model M10 is shown, but the output value of the air flow meter 18 is corrected using, for example, an air flow meter model that compensates for a response delay in the air flow meter 18. Various changes are possible, such as inputting the throttle passage air flow rate mt to the throttle model M11.

  Next, how to diagnose the failure of the valve timing sensor 23 will be described. The calculation of the intake valve closing timing IVC using the valve closing timing estimation model M10 as described above can be performed even when the valve timing sensor 23 has not failed. Therefore, in the embodiment according to the present invention, the intake valve closing timing IVC is always calculated using the valve closing timing estimation model M10 regardless of whether or not the valve timing sensor 23 has failed, and the calculated valve closing timing estimation model M10 is calculated. When the calculated value of the above and the intake valve closing timing detected by the valve timing sensor 23 are greatly different from each other by a predetermined value or more, it is determined that the valve timing sensor 23 has failed.

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 3 Cylinder head 4 Piston 5 Combustion chamber 7 Intake valve 17 Throttle valve 18 Air flow meter 22 Relative position sensor 23 Valve timing sensor 24 Throttle opening sensor A Variable compression ratio mechanism B Variable valve timing mechanism

Claims (7)

A variable compression ratio mechanism that can change the mechanical compression ratio, a variable valve timing mechanism that can control the closing timing of the intake valve, a mechanical compression ratio detection device that can detect the mechanical compression ratio, and a torque fluctuation that detects torque fluctuation And the variable compression ratio mechanism is controlled so that the mechanical compression ratio detected by the mechanical compression ratio detection device becomes a target mechanical compression ratio set according to the engine operating state, and the intake valve is closed. In the spark ignition internal combustion engine, in which the variable valve timing mechanism is controlled so that the timing becomes a target valve closing timing set according to the engine operating state,
When the mechanical compression ratio detection device fails, when the engine load increases, the spark compression internal combustion engine is designed so that the mechanical compression ratio is first lowered within a range in which the torque fluctuation more than the reference torque fluctuation is not detected by the torque fluctuation detecting means. organ.   When the mechanical compression ratio detection device fails, when the engine load increases, the torque fluctuation detecting means reaches the lowest mechanical compression ratio within a range in which no torque fluctuation more than the reference torque fluctuation is detected, or the mechanism of the variable compression ratio mechanism The spark ignition type internal combustion engine according to claim 1, wherein the change of the closing timing of the intake valve is started after reaching a minimum mechanical compression ratio at which the mechanical compression ratio cannot be further reduced.   The mechanical compression ratio is increased within a range in which torque fluctuation more than the reference torque fluctuation does not occur first by the torque fluctuation detecting means when the engine load is reduced when the mechanical compression ratio detecting device fails. 2. The spark ignition internal combustion engine according to 2.   When the mechanical compression ratio detecting device fails, when the engine load decreases, the torque fluctuation detecting means reaches the highest mechanical compression ratio within a range where no torque fluctuation exceeding the reference torque fluctuation is detected, or the mechanism of the variable compression ratio mechanism 4. The spark ignition type internal combustion engine according to claim 3, wherein the change of the closing timing of the intake valve is started after reaching a maximum limit mechanical compression ratio at which the mechanical compression ratio cannot be further increased.   During normal operation of the internal combustion engine, the mechanical compression ratio and the closing timing of the intake valve are controlled by the torque fluctuation detection means so that the torque fluctuation more than the reference torque fluctuation does not occur, and the reference torque is detected by the torque fluctuation detection means during operation of the internal combustion engine. The spark ignition internal combustion engine according to any one of claims 1 to 4, wherein it is determined that the mechanical compression ratio detection device is out of order when a torque fluctuation greater than the fluctuation is detected. A valve closing timing detecting device capable of detecting the valve closing timing of the intake valve; and an intake air amount detecting device for detecting a flow rate of the air flowing through the intake passage, the intake valve being detected by the valve closing timing detecting device. The variable valve timing mechanism is controlled so that the valve closing timing becomes a target valve closing timing set according to the engine operating state,
The valve closing timing of the intake valve is estimated based on the flow rate of air flowing through the intake passage detected by the intake air amount detection device when the valve closing timing detection device fails. 2. The spark ignition internal combustion engine according to item 1.   When an intrusion prohibited region is set for the operating point indicating the combination of the mechanical compression ratio and the intake valve closing timing, and the mechanical compression ratio detection device is not malfunctioning, when the required intake air amount changes The target operating point that can be reached after a certain time without entering the intrusion prohibited area from the current operating point to the operating point that satisfies the required intake air amount is calculated, and the mechanical compression ratio and intake valve closing timing are targeted. The spark ignition type internal combustion engine according to any one of claims 1 to 6, wherein the internal combustion engine is changed toward an operating point.

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