JP2012237294A - Spark ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark ignition internal combustion engine that enables adjustment of a magnitude of intake pulsation in an engine intake passage according to an operating condition.SOLUTION: The spark ignition internal combustion engine includes a variable compression ratio mechanism which can change a mechanical compression ratio, and an intake pulsation estimation device for estimating the magnitude of the intake pulsation in the engine intake passage. The position on a downstream vibration edge of the intake pulsation is changed by estimating the magnitude of the intake pulsation in the engine intake passage and by changing the mechanical compression ratio based on the magnitude of the intake pulsation, and thereby the magnitude of the intake pulsation is changed.

Description

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

  In the combustion chamber of the internal combustion engine, the air-fuel mixture is ignited in a compressed state. It is known that the compression ratio when compressing the air-fuel mixture affects the output torque and the fuel consumption. By increasing the compression ratio, the output torque can be increased or the fuel consumption can be reduced. On the other hand, it is known that if the compression ratio is too high, abnormal combustion such as knocking occurs. In the prior art, an internal combustion engine is known that includes a variable compression ratio mechanism that can change the compression ratio during an operation period, and a variable valve timing mechanism that can change the opening / closing timing of the intake valve.

  Japanese Patent Application Laid-Open No. 2004-239146 includes an intake fresh air amount variable mechanism that makes the intake fresh air amount variable, and a variable compression ratio mechanism that makes the compression ratio variable, so that the target engine speed is achieved during idling. An engine that controls the intake fresh air amount variable mechanism to control the intake fresh air amount is disclosed. In this engine intake control device, it is disclosed that the control amount of the intake fresh air amount variable mechanism is corrected based on the actual compression ratio controlled by the variable compression ratio mechanism during idling.

  In Japanese Patent Laid-Open No. 4-140466, an intake pulsation detection sensor provided on the upstream side in the intake path of an internal combustion engine, and a diaphragm disposed on the downstream side of the intake path detection sensor, An intake structure for an internal combustion engine is disclosed that includes a piezoelectric actuator that drives a diaphragm, and detection means that detects a period and amplitude of intake pulsation in response to a signal from a detection sensor. In the intake structure of this internal combustion engine, noise due to intake pulsation is generated by oscillating the piezoelectric actuator with the same amplitude as the detected amplitude by shifting the phase with respect to the detected period when receiving a signal from the detecting means. Preventing is disclosed.

  In Japanese Patent Application Laid-Open No. 2009-270483, a high response type air flow meter whose output changes with good response according to a change in the amount of intake air is installed in the intake pipe so that intake pulsation and backflow can be detected. An engine is disclosed. In this engine, control for closing the intake opening / closing valve in a predetermined period determined in consideration of the relationship between the intake stroke of each cylinder and the intake pulsation timing and opening the intake opening / closing valve in another period is executed. Is disclosed. In this internal combustion engine, it is disclosed that the charging efficiency is reliably improved without being affected by manufacturing variations and changes with time.

  Japanese Patent Application Laid-Open No. 2008-267209 discloses a cylinder filling air amount calculation device for an internal combustion engine that calculates the cylinder filling air amount based on the product of the density in the intake manifold and the cylinder volume. The apparatus for calculating the cylinder charge air amount may calculate a first correction coefficient due to intake pulsation with respect to the effective cylinder volume, and calculate an effective cylinder volume corrected by multiplying the effective cylinder volume by the first correction coefficient. It is disclosed.

JP 2004-239146 A JP-A-4-140466 JP 2009-270483 A JP 2009-257117 A JP 2008-267209 A JP 2009-264258 A

  In the internal combustion engine, the operating state of the internal combustion engine such as the fuel injection amount and the intake air amount is determined in accordance with the required load corresponding to the depression amount of the accelerator pedal. During the operation period of the internal combustion engine, there is an operation state in which the load demanded by the driver is zero. For example, an idling operation state exists as a no-load operation state in which a required load for rotating the wheel is zero. In the idling operation state, for example, the internal combustion engine is controlled so that the engine speed is within a predetermined range.

  In an internal combustion engine having a variable compression ratio mechanism that changes the mechanical compression ratio of the internal combustion engine and a variable valve mechanism that changes the closing timing of the intake valve, the machine is used to improve thermal efficiency during idling operation. It is preferable to increase the compression ratio. In order to reduce the intake loss, it is preferable to reduce the intake air amount by adjusting the closing timing of the intake valve.

  In a normal internal combustion engine in which the intake air amount is controlled only by a throttle valve, intake pulsation hardly occurs during the idling operation period. However, in an internal combustion engine that adjusts the intake air amount according to the closing timing of the intake valve, for example, the intake valve is closed at a timing later than the timing at which the piston is located at the bottom dead center. In the idling operation state, since the engine speed is small, the intake air amount is also set small. The closing timing of the intake valve is set to the most retarded side. There is a period when the intake valve is opened during the period when the piston moves from bottom dead center to top dead center, and blowback occurs to the engine intake passage. For this reason, an internal combustion engine including a variable compression ratio mechanism and a variable valve mechanism has a characteristic that intake pulsation is likely to occur even during an idling operation period.

  Further, when the engine is idling, the engine speed is kept low because the required load is zero. The amount of intake air flowing into the combustion chamber needs to be controlled with high accuracy. In particular, in the idling operation state, high-precision controllability of the output torque is required. For this reason, for example, there is a problem that it is difficult to correct the variation in the intake air amount due to the intake pulsation by adjusting the fuel injection amount.

  As described above, intake pulsation occurs during the idling operation period, which makes it difficult to stabilize the engine speed and the like. The convergence of the engine speed may deteriorate, and noise and vibration may occur. Furthermore, the amount of fresh air flowing into the combustion chamber due to the intake pulsation may be temporarily reduced, and an engine stall may occur. Alternatively, the amount of fresh air flowing into the combustion chamber due to the intake pulsation temporarily increases, and there is a possibility that an overrun in which the engine speed excessively increases occurs.

  On the other hand, it may be preferable for the operating state of the internal combustion engine to increase the amount of fresh air flowing into the combustion chamber. For example, when the required load is large, it is preferable to increase the amount of fresh air supplied to the combustion chamber. That is, it is preferable to increase the filling efficiency. When it is desired to increase the charging efficiency, it is preferable that the amount of fresh air supplied to the combustion chamber can be increased by the intake pulsation.

  It is an object of the present invention to provide a spark ignition type internal combustion engine that includes a variable compression ratio mechanism that can change a mechanical compression ratio and that can adjust the magnitude of intake pulsation in an engine intake passage according to an operating state. .

  The spark ignition internal combustion engine of the present invention includes a variable compression ratio mechanism that can change the mechanical compression ratio, and an intake pulsation estimation device that estimates the magnitude of intake pulsation in the engine intake passage. Estimating the magnitude of intake pulsation in the engine intake passage, and changing the mechanical compression ratio based on the magnitude of intake pulsation changes the position of the downstream vibration end of the intake pulsation, thereby changing the magnitude of the intake pulsation .

  In the above invention, the variable valve mechanism that can change the closing timing of the intake valve is provided, and the closing timing of the intake valve is set so as to reduce the amount of fresh air supplied to the combustion chamber as the required load decreases. It has an operating region that is retarded, and is configured to perform idling control that maintains a predetermined operating state when the required load is zero, and when performing idling control, intake pulsation When the magnitude is estimated and the magnitude of the intake pulsation is larger than a predetermined pulsation determination value, the magnitude of the intake pulsation can be reduced by changing the mechanical compression ratio.

  In the above invention, in the operating state in which the amount of fresh air charged in the combustion chamber is to be increased, the magnitude of the intake pulsation is estimated, and when the magnitude of the intake pulsation is smaller than a predetermined pulsation determination value, The magnitude of the intake pulsation can be increased by changing the mechanical compression ratio.

  In the above invention, the ignition timing adjusting device capable of changing the ignition timing in the combustion chamber is provided, and the position of the downstream vibration end of the intake pulsation can be changed by changing the ignition timing.

  In the above invention, the variable compression ratio mechanism includes a mechanical compression ratio detector that estimates an actual mechanical compression ratio during an operation period, and the intake pulsation estimation device estimates an actual mechanical compression ratio and performs actual mechanical compression. The magnitude of the intake pulsation can be estimated based on the magnitude of the ratio vibration.

  ADVANTAGE OF THE INVENTION According to this invention, a spark ignition internal combustion engine provided with the variable compression ratio mechanism in which the magnitude | size of the intake pulsation of an engine intake passage can be adjusted according to a driving | running state can be supplied.

1 is a schematic overall view of an internal combustion engine in an embodiment. It is a general | schematic exploded perspective view of the variable compression ratio mechanism in embodiment. (A) to (C) is a schematic cross-sectional view of a variable compression ratio mechanism for explaining a change in mechanical compression ratio in the embodiment. It is the schematic explaining the variable valve timing mechanism in embodiment. It is a graph explaining opening and closing timing of the intake valve and the exhaust valve in the embodiment. (A) is explanatory drawing of a mechanical compression ratio, (B) is explanatory drawing of an actual compression ratio, (C) is explanatory drawing of an expansion ratio. It is a graph explaining the relationship between the expansion ratio of an internal combustion engine and theoretical thermal efficiency in embodiment. (A) is explanatory drawing of a normal driving cycle, (B) is explanatory drawing of a super-high expansion ratio cycle. It is a graph of operation control of an internal-combustion engine in an embodiment. (A) is explanatory drawing when intake pulsation becomes large during the period of idling operation, (B) is explanatory drawing when performing the 1st vibration end change control in an embodiment. is there. 4 is a flowchart of control for suppressing intake air pulsation in an idling operation state in the internal combustion engine of the embodiment. It is a time chart explaining the control which estimates the magnitude | size of the intake pulsation in embodiment. It is a time chart explaining the other control which estimates the magnitude | size of the intake pulsation in embodiment. It is a time chart explaining the driving | running state when the intake air pulsation does not arise in a comparative example. (A) is explanatory drawing when intake pulsation becomes large during the period of idling operation, (B) is explanatory drawing when performing the 2nd vibration end change control in an embodiment. . 4 is a graph for explaining a relationship between an ignition timing in a cylinder, an output of an internal combustion engine, and exhaust pressure.

  The internal combustion engine in the embodiment will be described with reference to FIGS. The internal combustion engine in the present embodiment includes a variable compression ratio mechanism that can change the mechanical compression ratio and a variable valve mechanism that can change the closing timing of the intake valve, and increases the expansion ratio in a low load region. Super high expansion ratio control.

  FIG. 1 is a schematic overall view of an internal combustion engine in the present embodiment. The internal combustion engine in the present embodiment includes a crankcase 1, a cylinder block 2, and a cylinder head 3. A piston 4 is disposed in a hole formed in the cylinder block 2. A spark plug 6 is disposed at the center of the top surface of the combustion chamber 5 surrounded by the top surface of the piston 4 and the cylinder head 3. An intake port 8 and an exhaust port 10 are formed in the cylinder head 3. An intake valve 7 is disposed at the end of the intake port 8. An exhaust valve 9 is disposed at the end of the exhaust port 10. The intake port 8 is connected to a surge tank 12 via an intake branch pipe 11. Each intake branch pipe 11 is provided with a fuel injection valve 13 for injecting fuel into the corresponding intake port 8. Instead of being attached to each intake branch pipe 11, the fuel injection valve 13 may be arranged so as to inject fuel directly into each combustion chamber 5.

  The surge tank 12 is connected to an air cleaner 15 via an intake duct 14. A throttle valve 17 driven by an actuator 16 is disposed in the intake duct 14. Further, an intake air amount detector 18 using, for example, heat rays is disposed in the intake duct 14. On the other hand, the exhaust port 10 is connected through an exhaust manifold 19 to a catalyst device 20 containing, for example, a three-way catalyst. An air-fuel ratio sensor 21 is disposed in the exhaust manifold 19.

  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. A variable compression ratio mechanism A that can change the volume of the combustion chamber 5 at the time is provided. Furthermore, an actual compression action start timing changing mechanism B that can change the actual compression action start timing is provided. The actual compression operation start timing changing mechanism B in the present embodiment includes a variable valve timing mechanism as a variable valve mechanism that can control the closing timing of the intake valve 7.

  A relative position sensor 22 for detecting the relative positional relationship between the crankcase 1 and the cylinder block 2 is attached to the crankcase 1 and the cylinder block 2. The relative position sensor 22 outputs an output signal indicating a change in the distance between the crankcase 1 and the cylinder block 2. The variable valve timing mechanism B is attached with a valve timing sensor 23 that generates an output signal indicating the closing timing of the intake valve 7. A throttle opening sensor 24 for generating an output signal indicating the throttle valve opening is attached to the actuator 16 for driving the throttle valve.

  The control device for the internal combustion engine in the present embodiment includes an electronic control unit 30. Electronic control unit 30 in the present embodiment includes a digital computer. The digital computer includes 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 connected to each other by a bidirectional bus 31. Output signals of the intake air amount detector 18, the air-fuel ratio sensor 21, the relative position sensor 22, the valve timing sensor 23, and the throttle opening sensor 24 are input to the input port 35 via the corresponding AD converters 37. 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. The required load can be detected from the output of the load sensor 41. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 °. The engine speed can be detected from the output of the crank angle sensor 42.

  On the other hand, the output port 36 is connected to the spark plug 6, the fuel injection valve 13, the actuator 16 for driving the throttle valve, the variable compression ratio mechanism A, and the variable valve timing mechanism B through a corresponding drive circuit 38. These devices are controlled by the electronic control unit 30.

  FIG. 2 is an exploded perspective view of the variable compression ratio mechanism shown in FIG. FIG. 3 shows a schematic sectional view of the internal combustion engine for explaining the operation of the variable compression ratio mechanism. Referring to FIG. 2, a plurality of protrusions 50 are formed below the both side walls of the cylinder block 2 so as to be spaced apart from each other. A cam insertion hole 51 having a circular cross section is formed in each protrusion 50. 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 at intervals. Each of these protrusions 52 is also formed with a cam insertion hole 53 having a circular cross section.

  The variable compression ratio mechanism in the present embodiment includes a pair of camshafts 54 and 55. On each of the camshafts 54 and 55, a circular cam 58 that is rotatably inserted into each of the cam insertion holes 53 is fixed. These circular cams 58 are coaxial with the rotational axes of the camshafts 54 and 55. On the other hand, on both sides of each circular cam 58, as shown in FIG. 3, eccentric shafts 57 that are eccentrically arranged with respect to the rotation axes of the cam shafts 54 and 55 extend. Another circular cam 56 is eccentrically mounted on the eccentric shaft 57 so as to be 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. A cam rotation angle sensor 25 that generates an output signal representing the rotation angle of the cam shaft 55 is attached to the cam shaft 55. The output of the cam rotation angle sensor 25 is input to the electronic control unit 30.

  When the circular cams 58 fixed on the camshafts 54 and 55 are rotated in opposite directions as shown by arrows in FIG. 3A from the state shown in FIG. The circular cam 56 rotates in a direction opposite to the circular cam 58 in the cam insertion hole 51 so as to move away from each other, and as shown in FIG. Position. 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. The cylinder block 2 moves away from the crankcase 1 as the distance between the center a of the cylinder and the center c of the circular cam 56 increases. 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 positioned 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 that mesh with the worms 61 and 62 are fixed to the ends 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.

  The variable compression ratio mechanism in the present embodiment moves the cylinder block relative to the lower structure including the crankcase. However, the variable compression ratio mechanism is not limited to this form. Any mechanism that can change the ratio can be employed.

  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. The variable valve timing mechanism B in the present embodiment 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, and an intake valve drive A rotating shaft 73 that rotates together with the camshaft 70 and is rotatable relative to the cylindrical housing 72; 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; A vane 75 extending from the outer peripheral surface of the rotary shaft 73 to the inner peripheral surface of the cylindrical housing 72 is provided between the partition walls 74, and an advance hydraulic chamber 76 and a retard angle are provided on both sides of each vane 75, respectively. A 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 for controlling communication 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 angular 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. And the hydraulic oil in the advance hydraulic chamber 76 is discharged from the drain port 83. 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 rotating shaft 73 is rotating relative to the cylindrical housing 72, the relative rotating operation of the rotating shaft 73 is stopped. Is held at the relative rotational position. Therefore, the variable valve timing mechanism B can advance or 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. Therefore, the closing timing of the intake valve 7 can also be set to an arbitrary crank angle within the range indicated by the arrow C in FIG.

  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. 6 (A), (B), and (C) 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 operation is not performed while the intake valve is open, and the actual compression is performed from the time when the intake valve is closed. The action begins. Therefore, the actual compression ratio is expressed as described 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 as well, the combustion chamber volume is set to 50 ml, and the stroke volume of the piston is set to 500 ml, similarly to the example 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, it is only necessary to increase the actual compression ratio. 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. Has 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. The increase in the theoretical thermal efficiency when the expansion ratio is increased while maintaining the actual compression ratio ε at a low value, and the theoretical thermal efficiency when the actual compression ratio increases 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 high engine load operation, the normal cycle shown in FIG. 8A is used.

Next, an example of operation control in the present embodiment will be described with reference to FIG. FIG. 9 is a graph schematically illustrating general operation control of the super-high expansion ratio control. FIG. 9 shows changes in required intake air amount, intake valve closing timing, expansion ratio (mechanical compression ratio), actual compression ratio, and throttle valve opening according to the engine load at a certain engine speed. ing. Incidentally, FIG. 9, unburned HC, the average air-fuel ratio output signal of the air-fuel ratio sensor 21 in the combustion chamber 5 so as to be able to reduce at the same time CO and NO _X in the exhaust gas by the three-way catalyst in the catalytic device 20 This shows a case where feedback control is performed to the theoretical 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, at this time, the mechanical compression ratio is lowered, so the expansion ratio is low, and the closing timing of the intake valve 7 is advanced as shown by the solid line in FIG. 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, when the engine load becomes low, the closing timing of the intake valve 7 is delayed so as to reduce the intake air amount. At this time, the mechanical compression ratio is increased as the engine load is reduced so that the actual compression ratio is maintained substantially constant. Therefore, the expansion ratio increases as the engine load decreases. At this time, the throttle valve 17 is kept fully open, and 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. ing.

  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 of 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.

  As the engine load is further reduced, the mechanical compression ratio further increases. In the internal combustion engine shown in FIG. 9, the mechanical compression ratio reaches a limit mechanical compression ratio (upper limit mechanical compression ratio) that becomes the structural limit of the combustion chamber 5 when the engine load is reduced to the medium load L1 that is slightly close to the low load. When the mechanical compression ratio reaches the limit mechanical compression ratio, the mechanical compression ratio is held at the limit mechanical compression ratio in a region where the load is lower than the engine load L1 when the mechanical compression ratio reaches the limit mechanical compression ratio. Accordingly, 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, at 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 L1, 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 is reduced in a region where the load is lower than the engine load L1 when the closing timing of the intake valve 7 reaches the closing timing. It is held at the limit 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 L1 when the closing timing of the intake valve 7 reaches the limit closing timing, the throttle valve 17 enters the combustion chamber 5. The amount of intake air to be supplied is controlled, and the opening degree of the throttle valve 17 is made smaller as the engine load becomes lower.

  In the embodiment according to the present invention, the closing timing of the intake valve 7 moves away from the intake bottom dead center BDC until the limit closing timing at which the amount of intake air supplied into the combustion chamber can be controlled as the engine load decreases. Will be.

  As described above, the expansion ratio is 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 this embodiment, the variable compression ratio mechanism A is formed so that the expansion ratio is 20 or more.

  The internal combustion engine in the present embodiment is configured to perform idling control for maintaining a predetermined driving state when the load required by the driver is zero. In the idling control, for example, control is performed so as to maintain a predetermined engine speed.

  As shown in FIG. 9, in the internal combustion engine of the present embodiment, when performing idling operation, the mechanical compression ratio is maintained at a predetermined high mechanical compression ratio. The closing timing of the intake valve is maintained at a predetermined most retarded timing. The intake air amount is adjusted by adjusting the opening of the throttle valve.

  During the idling operation, the closing timing of the intake valve is set later than the timing when the piston is located at the bottom dead center. There is a period when the intake valve is open even when the piston is rising toward the top dead center, and a part of the fresh air once flowing into the cylinder may flow back into the engine intake passage. For this reason, intake air pulsation is likely to occur in the engine intake passage, the amount of intake air charged in the combustion chamber may become unstable, and the operating state may become unstable.

  The internal combustion engine of the present embodiment is provided with an intake pulsation estimation device that estimates the magnitude of intake pulsation in the engine intake passage. The internal combustion engine estimates the magnitude of the intake pulsation in the engine intake passage, and changes the position of the downstream vibration end of the intake pulsation by changing the mechanical compression ratio based on the estimated magnitude of the intake pulsation. By changing the position of the downstream vibration end, vibration end change control for changing the magnitude of intake pulsation can be performed. The internal combustion engine can change the magnitude of the intake pulsation according to the operating state.

  During the idling operation of the present embodiment, when the magnitude of the intake pulsation is larger than a predetermined pulsation judgment value, the downstream vibration end of the intake pulsation is changed by changing the mechanical compression ratio. And reduce the magnitude of the intake pulsation. First vibration end change control for suppressing intake pulsation is performed.

  FIG. 10 is an explanatory diagram of a state before and after performing the first vibration end change control for suppressing the intake pulsation in the present embodiment. FIG. 10A is an explanatory diagram when intake air pulsation occurs when the internal combustion engine is idling. FIG. 10B is an explanatory diagram when the first vibration end change control is performed in the present embodiment.

  Referring to FIG. 10A, in the idling operation state, the mechanical compression ratio is maintained at a high compression ratio. The left end is the upstream vibration end of the intake pulsation, and corresponds to the position of the air cleaner in the present embodiment. On the downstream side, a top dead center and a bottom dead center when the piston moves are shown. The piston moves within a movement range R between the top dead center and the bottom dead center. The movement range R corresponds to the stroke volume of the piston. The position of the intake valve corresponds to the entrance of the combustion chamber. The area between the position of the intake valve and the top dead center of the piston corresponds to the combustion chamber.

  In the example shown in FIG. 10 (A), intake pulsation occurs with the upstream vibration end as a vibration node. The downstream vibration end of the intake pulsation is, for example, a crown surface of a piston, and FIG. 10 shows the position of the cycle average downstream vibration end averaged in the combustion cycle. In FIG. 10A, the position of the downstream vibration end coincides with the position of the node of the intake pulsation. The distance between the upstream vibration end and the downstream vibration end is an integral multiple of the intake pulsation wavelength. In such a case, the intake pulsation increases, for example, the amplitude of the intake pulsation increases.

  Examples of the position that becomes the downstream vibration end of the cycle average include a substantially intermediate position between the top dead center and the bottom dead center that are the moving ends of the piston. Alternatively, for example, the downstream vibration end can be determined as a function of the in-cylinder pressure, the opening / closing timing of the intake valve, and the opening / closing timing of the exhaust valve.

  In the internal combustion engine of the present embodiment, in the idling operation state, it is detected that the magnitude of the intake pulsation is larger than a predetermined pulsation judgment value, and the vibration that moves the downstream vibration end Perform edge change control. The vibration end change control of the present embodiment includes control for changing the mechanical compression ratio.

  Referring to FIG. 10B, in the present embodiment, control for lowering the mechanical compression ratio is performed. The positions of the top dead center and the bottom dead center of the piston move away from the air cleaner. The downstream vibration end moves in a direction away from the upstream vibration end as indicated by an arrow 111. For this reason, the downstream vibration end can be separated from the position of the node of the intake pulsation, and the magnitude of the intake pulsation can be reduced. For example, the amplitude of the intake pulsation can be reduced.

  In the present embodiment, the mechanical compression ratio is decreased from the high compression ratio, but the present invention is not limited to this form, and the mechanical compression ratio may be increased. For example, the idling operation may be performed at a compression ratio lower than the limit mechanical compression ratio in consideration of a margin for the achievable limit mechanical compression ratio of the variable compression ratio mechanism. In such a case, the mechanical compression ratio can be further increased even in the idling operation state. That is, the vibration end change control can also be performed by increasing the mechanical compression ratio.

  FIG. 11 shows a flowchart of the first vibration end change control in the present embodiment. The control shown in FIG. 11 can be repeatedly performed at predetermined time intervals during the operation period, for example.

  In step 101, it is determined whether or not the internal combustion engine is idling. In step 101, when the internal combustion engine is not performing idling control, this control is terminated. In step 101, when the internal combustion engine is performing idling control, the routine proceeds to step 102.

  In step 102, the magnitude of intake pulsation in the engine intake passage is estimated. In step 103, it is determined whether or not the magnitude of the intake pulsation is greater than a predetermined pulsation determination value. It is determined whether or not the intake pulsation is large.

  FIG. 12 shows a time chart for explaining the estimation of the magnitude of intake pulsation in the present embodiment. FIG. 12 illustrates an operating state in which the intake pulsation gradually increases. The intake pulsation estimation device of this embodiment estimates the magnitude of intake pulsation based on the output of the intake air amount detector 18 disposed in the engine intake passage.

  In the present embodiment, the intake air flow rate is detected, and the median value at each time is calculated from the detected change in the intake air flow rate. Further, a value obtained by adding or subtracting a predetermined criterion value is set with respect to the median value. A value obtained by subtracting the determination reference value from the median value is referred to as a lower limit value, and a value obtained by adding the determination reference value from the median value is referred to as an upper limit value.

  In the present embodiment, the magnitude of the amplitude of the intake pulsation is estimated, and when the magnitude of the amplitude is within a predetermined amplitude determination value, the magnitude of the intake pulsation is determined as a predetermined pulsation. It is determined that it is within the value. As the amplitude determination value, for example, a value obtained by subtracting the lower limit value from the upper limit value of the intake air flow rate (determination reference value × 2) can be employed.

  At time ta1, time ta5, etc., intake pulsation occurs within a range between an upper limit value (median value + determination value reference value) and a lower limit value (median value−determination reference value). The amplitude of the intake air flow rate is equal to or less than the amplitude determination value, and it can be determined that the magnitude of the intake pulsation is within the pulsation determination value. The magnitude of the amplitude can be estimated by subtracting the value at time ta4 when the intake air flow rate is small from the value at time ta1 when the intake air flow rate is high. The magnitude of the amplitude can be compared with the amplitude determination value.

  On the other hand, after time tb1, the amplitude of the intake pulsation increases. For example, the magnitude of the amplitude can be estimated by subtracting the value at time tb1 when the intake air flow rate is small from the value at time tb3 when the intake air flow rate is high. At time tb1, the intake air flow rate is smaller than the lower limit value. At time tb3, the intake air flow rate is larger than the upper limit value. For this reason, the amplitude of the intake air flow rate exceeds a predetermined amplitude determination value. For this reason, it can be determined that the magnitude of the intake pulsation is greater than a predetermined pulsation determination value.

  Referring to FIG. 11, in step 103, when the magnitude of the intake pulsation is equal to or smaller than a predetermined pulsation determination value, this control is terminated. When the magnitude of the intake pulsation is larger than a predetermined pulsation determination value, the routine proceeds to step 104.

  In step 104, vibration end change control is performed. In the vibration end change control of the present embodiment, referring to FIG. 10, the distance between the upstream vibration end and the downstream vibration end (the length of cycle-average vibration ends) is changed. In the first vibration end change control, control is performed to reduce the mechanical compression ratio so as to avoid that the length of the cycle average vibration ends is an integral multiple of the intake pulsation wavelength. For example, a predetermined amount can be adopted as the change amount of the mechanical compression ratio. Alternatively, the amount of change in the mechanical compression ratio can be determined by estimating the wavelength of intake pulsation or the period of intake pulsation in the region between the vibration ends.

  In the present embodiment, the magnitude of the intake pulsation is estimated during the idling control period, and the mechanical compression ratio is changed when the magnitude of the intake pulsation is larger than a predetermined pulsation judgment value. Thus, intake pulsation can be suppressed.

  The method for determining the magnitude of the intake pulsation is not limited to the above-described method for estimating the amplitude of the intake air flow rate, and any method capable of determining the magnitude of the intake pulsation can be employed. For example, when the intake air flow rate exceeds at least one of the lower limit value and the upper limit value, it can be determined that the magnitude of the intake pulsation exceeds the pulsation determination value. In addition, the magnitude of the intake pulsation is not limited to the amplitude of the intake air flow rate described above, and for example, the acceleration of vibration of the intake air flow rate can be employed.

  FIG. 13 shows a time chart in another intake pulsation estimation device of the present embodiment. In another intake pulsation estimation device, an actual mechanical compression ratio is estimated, and the magnitude of the intake pulsation is estimated based on a change in the actual mechanical compression ratio. FIG. 13 shows the supply voltage to the drive motor 59 of the variable compression ratio mechanism, the pressure in the cylinder (cycle average value), and the value of the actually estimated mechanical compression ratio.

  The variable compression ratio mechanism in the present embodiment includes a mechanical compression ratio detector that estimates an actual mechanical compression ratio during an operation period. The mechanical compression ratio detector in the present embodiment includes a relative position sensor 22 that detects a relative position between the crankcase 1 and the cylinder block 2. The actual mechanical compression ratio can be estimated from the output of the relative position sensor 22 (see FIG. 1).

  Until the time tx, the mechanical compression ratio is maintained substantially constant. The variable compression ratio mechanism in the present embodiment includes a mechanical compression ratio fixing mechanism (not shown). For this reason, during the period in which the mechanical compression ratio is kept constant, the actual mechanical compression ratio is maintained at a substantially constant value without vibration. At time tx, the fixing of the mechanical compression ratio by the fixing mechanism is released. At time tx, the voltage supplied to the drive motor of the variable compression ratio mechanism is increased. In the present embodiment, control for gradually increasing the actual mechanical compression ratio is performed.

  FIG. 14 shows a time chart of a comparative example in which intake air pulsation does not occur in the engine intake passage. At time tx, the supply voltage to the drive motor is increased. Until the time tx, the cylinder pressure is substantially constant, and the actual mechanical compression ratio is also substantially constant. By supplying electric power to the drive motor of the variable compression ratio mechanism at time tx, the pressure in the cylinder and the mechanical compression ratio gradually increase. The pressure in the cylinder and the mechanical compression ratio rise linearly at a substantially constant rate.

  Referring to FIG. 13, when an intake pulsation occurs in the engine intake passage, the cylinder pressure vibrates even after time tx. The pressure in the cylinder gradually increases while vibrating. By the way, when the pressure in the cylinder vibrates, for example, the size of the combustion chamber when the piston reaches top dead center also changes. Since the wall surface in the cylinder is pressed by the pressure in the cylinder, the volume in the cylinder slightly changes. In the present embodiment, the relative position of the cylinder block with respect to the crankcase changes slightly. The relative position sensor in the present embodiment is formed so as to detect such a small change. When the cylinder pressure increases due to vibration, the mechanical compression ratio decreases. Thus, when the intake pulsation occurs and the cylinder pressure pulsates, the actual mechanical compression ratio also rises while oscillating.

  In another intake pulsation estimation device of the present embodiment, the actual mechanical compression ratio is estimated, and the magnitude of the intake pulsation is estimated based on the magnitude of vibration of the actual mechanical compression ratio. When the actual magnitude of vibration of the mechanical compression ratio is larger than a predetermined vibration determination value, it is determined that the magnitude of the intake pulsation is larger than the predetermined pulsation determination value. In the operation example of FIG. 13, a median value during a period in which the mechanical compression ratio is increasing is calculated, and values obtained by adding or subtracting a predetermined criterion value to the median value are used as an upper limit value and a lower limit value.

  For example, at time td1, the actual mechanical compression ratio exceeds the upper limit value. At time td2, the actual mechanical compression ratio is less than the lower limit value. It can be determined that the actual amplitude of the mechanical compression ratio is larger than the amplitude determination value. In this case, it can be determined that the magnitude of the intake pulsation is larger than a predetermined pulsation determination value.

  In another intake pulsation estimation device of the present embodiment, the mechanical compression ratio is slowly changed to such an extent that the intake pulsation is not substantially affected. In the control for estimating the magnitude of intake pulsation, the fixed mechanism of the variable compression ratio mechanism may be released, and the magnitude of vibration of the actual mechanical compression ratio may be estimated while the mechanical compression ratio is substantially constant. .

  In the present embodiment, the position of the downstream vibration end of the intake pulsation is changed by changing the mechanical compression ratio. However, the position of the downstream vibration end is not limited to this form and is determined by an arbitrary method. Can be changed. Next, second vibration end change control for changing the position of the downstream vibration end by changing the ignition timing in the combustion chamber will be described.

  FIG. 15 is an explanatory diagram of a state before and after performing the second vibration end change control in the present embodiment. FIG. 15A is a schematic view when intake pulsation occurs in the idling state. The position of the downstream vibration end and the position of the node of the intake pulsation overlap. Inspiratory pulsation is increasing.

  FIG. 16 is a graph illustrating the relationship between the ignition timing of the internal combustion engine, the output (torque) of the internal combustion engine, and the exhaust pressure in the present embodiment. The output of the internal combustion engine changes according to the ignition timing. The internal combustion engine has an ignition timing MBT (Minimum Advance for Best Torque) at which the output becomes maximum. In the present embodiment, as indicated by an arrow 112, control is performed to retard the ignition timing θ1 to the ignition timing θ2. By shifting from the ignition timing θ1 to the ignition timing θ2, the output torque can be maintained substantially the same. That is, even if the ignition timing is retarded, the engine speed can be kept substantially constant.

  On the other hand, the exhaust pressure can be lowered by delaying the ignition timing. By reducing the exhaust pressure, the amount (external EGR amount) in which the exhaust gas of the previous combustion cycle exists in the combustion chamber can be reduced. As a result, the cylinder pressure (cycle average) can be lowered. Since the air in the cylinder becomes soft, the distance between the vibration ends of the upstream vibration end and the downstream vibration end can be increased.

  FIG. 15B is a schematic diagram when the second vibration end change control is performed. FIG. 15B is an explanatory diagram when the ignition timing in the combustion chamber is shifted from the ignition timing θ1 to the ignition timing θ2. By changing the ignition timing, the downstream vibration end can be moved away from the upstream vibration end as indicated by an arrow 113. The position of the downstream vibration end can be removed from the position of the vibration pulsation node. As a result, intake pulsation can be suppressed. In the second vibration end change control, the ignition timing is retarded. However, the present invention is not limited to this mode, and the ignition timing may be advanced.

  Further, the second vibration end change control in the present embodiment can be combined with the first vibration end change control in the present embodiment. That is, when the magnitude of the intake pulsation in the engine intake passage is estimated and the magnitude of the intake pulsation is greater than a predetermined pulsation determination value, the mechanical compression ratio is changed and the ignition timing is changed. Can do.

  By the way, in the above-described embodiment, the vibration end change control that suppresses the intake pulsation in the idling operation state has been described. However, the present invention is not limited to this form. It is possible to perform vibration end change control for increasing the value. In an operating state in which the amount of fresh air charged in the combustion chamber should be increased, the intake pulsation can be increased to increase the amount of fresh air flowing into the combustion chamber. For example, when the required load by the driver and the required intake air amount are substantially maximum, it is preferable to increase the charging efficiency in the combustion chamber.

  In the internal combustion engine of the present embodiment, the magnitude of intake pulsation in the engine intake passage is estimated and the magnitude of intake pulsation is predetermined in an operating state in which the amount of fresh air charged into the combustion chamber is to be increased. When it is smaller than the pulsation determination value, the third vibration end change control for increasing the magnitude of the intake pulsation can be performed. In the third vibration end change control, for example, a control for increasing the magnitude of the intake pulsation can be performed by changing the mechanical compression ratio. It is possible to control the position of the node of the intake pulsation at the downstream vibration end. In this case, it is preferable to have an estimation device that estimates the period and wavelength of the intake pulsation generated in the engine intake passage.

  The period and wavelength of the intake pulsation can be estimated from, for example, the intake air flow rate, the engine speed, the valve overlap amount between the intake valve and the exhaust valve, the opening of the throttle valve (the opening area of the throttle valve), and the like. it can. By such a known method, it is possible to estimate the period and wavelength of the intake pulsation and move the downstream vibration end toward a position that becomes a node of the intake pulsation, thereby performing control to increase the intake pulsation. By performing this control, a lot of fresh air can be filled in the combustion chamber. Also, when performing control to increase intake pulsation, the magnitude of intake pulsation can be increased by changing the ignition timing in the combustion chamber.

  In the present embodiment, the internal combustion engine including the variable compression ratio mechanism and the variable valve mechanism has been described as an example. However, the present invention is not limited to this form, and the internal combustion engine that does not have the variable valve mechanism is also described. The present invention can be applied.

  In the present embodiment, the internal combustion engine attached to the vehicle has been described as an example. However, the present invention is not limited to this embodiment, and the present invention is applied to an internal combustion engine disposed in an arbitrary device or facility. be able to.

  Furthermore, the above embodiments can be appropriately combined. In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. In the embodiment, the change shown in a claim is included.

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 4 Piston 5 Combustion chamber 7 Intake valve 15 Air cleaner 17 Throttle valve 18 Intake air amount detector 22 Relative position sensor 23 Valve timing sensor 30 Electronic control unit 51 Insertion hole 53 Insertion hole 53 Camshaft 56 Circular cam 57 Eccentric shaft 58 Circular cam 59 Drive motor 76 Advance hydraulic chamber 77 Delay hydraulic chamber 78 Hydraulic oil supply control valve A Variable compression ratio mechanism B Variable valve timing mechanism

Claims (5)

A variable compression ratio mechanism capable of changing the mechanical compression ratio, and an intake pulsation estimation device for estimating the magnitude of intake pulsation in the engine intake passage,
Estimate the magnitude of the intake pulsation in the engine intake passage, and change the mechanical compression ratio based on the magnitude of the intake pulsation, thereby changing the position of the downstream vibration end of the intake pulsation and changing the magnitude of the intake pulsation A spark ignition internal combustion engine characterized by the above. Equipped with a variable valve mechanism that can change the closing timing of the intake valve,
It has an operating range in which the closing timing of the intake valve is retarded so that the amount of fresh air supplied to the combustion chamber decreases as the required load decreases.
It is configured to perform idling control that maintains a predetermined operating state when the required load is zero,
When the idling control is performed, the magnitude of the intake pulsation is estimated, and when the magnitude of the intake pulsation is larger than a predetermined pulsation judgment value, the magnitude of the intake pulsation is changed by changing the mechanical compression ratio. The spark ignition type internal combustion engine according to claim 1, wherein the spark ignition type internal combustion engine is reduced.   In the operating state where the amount of fresh air to be filled in the combustion chamber should be increased, the magnitude of intake pulsation is estimated, and the mechanical compression ratio is changed when the magnitude of intake pulsation is smaller than a predetermined pulsation judgment value. 2. The spark ignition type internal combustion engine according to claim 1, wherein the magnitude of the intake pulsation is increased. Equipped with an ignition timing adjustment device that can change the ignition timing in the combustion chamber,
The spark ignition internal combustion engine according to any one of claims 1 to 3, wherein the position of the downstream vibration end of the intake pulsation is changed by changing the ignition timing. The variable compression ratio mechanism includes a mechanical compression ratio detector that estimates the actual mechanical compression ratio during operation,
The intake pulsation estimation device estimates an actual mechanical compression ratio, and estimates the magnitude of the intake pulsation based on the magnitude of vibration of the actual mechanical compression ratio. The spark ignition internal combustion engine according to one item.

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