JP2014114733A - Internal combustion engine having variable compression ratio mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the power consumption of an actuator for removing a roller of an inverse input block clutch when lowering a machine compression ratio, in an internal combustion engine comprising a variable compression ratio mechanism in which an operating shaft is arranged between a cylinder block and a crank case, the cylinder block is relatively moved to the crank case by turning the operating shaft by the actuator, the inverse input block clutch has an outer ring, an input shaft at the actuator side and an output shaft at the operating shaft side, and torque from the input shaft to a lowering direction of the machine compression ratio turns the output shaft after a cage which turns together with the input shaft presses and removes, to the turning direction of the output shaft, the roller fit into a clearance between the output shaft and the outer ring.SOLUTION: The actuator is not operated even if there is a requirement for lowering the machine compression ratio, and the actuator is operated when the in-cylinder pressure of one of air cylinders becomes the maximum (step 104).

Description

  The present invention relates to an internal combustion engine including a variable compression ratio mechanism.

  An internal combustion engine having a variable compression ratio mechanism that varies a mechanical compression ratio by moving a cylinder block relative to a crankcase along a cylinder axis is known. In such a variable compression ratio mechanism, for example, an operating shaft such as an eccentric shaft is disposed between the cylinder block and the crankcase, and the operating shaft is rotated by an actuator, whereby the cylinder block is made relative to the crankcase. It is to be moved.

  In such a variable compression ratio mechanism, when the in-cylinder pressure of any cylinder is high, in order to bring the cylinder block closer to the crankcase in order to increase the mechanical compression ratio, a large torque must be generated by the actuator. The power consumption at the actuator becomes large. Accordingly, in order to suppress power consumption in the actuator, it has been proposed to increase the mechanical compression ratio only when the in-cylinder pressures of all the cylinders are equal to or lower than a set value (see Patent Document 1).

  By the way, the explosive force in the cylinder is relatively large and acts to move the cylinder block away from the crankcase. If nothing is done, the working shaft is rotated in the direction of decreasing the mechanical compression ratio.

  In order to suppress this, when the explosion force in the cylinder acts to move the cylinder block away from the crankcase, a reverse input cutoff clutch that locks the rotation of the working shaft may be disposed between the actuator and the working shaft. Conceivable.

  Such a reverse input cutoff clutch has an outer ring, an input shaft on the actuator side, and an output shaft on the action shaft side, and when a torque in the direction of decreasing the mechanical compression ratio is generated from the output shaft side, the roller is connected to the output shaft and the outer ring. The output shaft is fixed by fitting in between. In such a fixed state of the output shaft (reverse input cutoff state), when torque in the direction of increasing the mechanical compression ratio acts from the input shaft side to the output shaft, the output shaft is easily separated from the roller, and the output shaft is moved by the input shaft. It can be rotated in the direction of increasing the mechanical compression ratio.

  However, when torque in the direction of decreasing the mechanical compression ratio acts from the input shaft side to the output shaft in the fixed state of the output shaft, it is fitted between the output shaft and the outer ring by the cage that rotates together with the input shaft. If the roller is not pressed and removed in the rotation direction of the output shaft, the input shaft cannot be rotated in the mechanical compression ratio decreasing direction by the input shaft.

JP 2009-264258 A JP 2007-239520 A

  In this way, when the variable compression ratio mechanism is provided with the reverse input cutoff clutch, as described above, the control may be performed so that the mechanical compression ratio is increased only when the in-cylinder pressures of all the cylinders are equal to or lower than the set value. If the mechanical compression ratio is arbitrarily reduced, a relatively large torque is required to remove the roller of the reverse input cutoff clutch, which may increase the power consumption of the actuator.

  Accordingly, an object of the present invention is to provide a variable compression ratio mechanism that moves the cylinder block relative to the crankcase by disposing the operating shaft between the cylinder block and the crankcase and rotating the operating shaft by the actuator. The reverse input cutoff clutch is arranged between the actuator and the working shaft, and the reverse input cutoff clutch has an outer ring, an input shaft on the actuator side, and an output shaft on the working shaft side. The torque in the direction of decreasing the mechanical compression ratio from the shaft is blocked by the roller being fitted between the outer ring and the output shaft, fixing the output shaft, and the torque in the decreasing direction of the mechanical compression ratio from the input shaft is An internal combustion engine provided with a variable compression ratio mechanism for rotating the output shaft after the rotating retainer is pressed between the output shaft and the outer ring in a rotating direction of the output shaft and removed. Oite is to inhibit the actuator power consumption to remove the rollers of the reverse input blocking clutch in reducing the mechanical compression ratio.

  An internal combustion engine comprising the variable compression ratio mechanism according to claim 1 of the present invention is configured such that an operating shaft is disposed between a cylinder block and a crankcase, and the operating shaft is rotated by an actuator, whereby the cylinder block is An internal combustion engine including a variable compression ratio mechanism that moves relative to a crankcase, wherein a reverse input cutoff clutch is disposed between the actuator and the operating shaft, and the reverse input cutoff clutch is connected to an outer ring and an actuator side. The torque of the mechanical compression ratio decreasing direction from the output shaft is fixed between the outer ring and the output shaft so that the output shaft is fixed. For the torque in the direction of decreasing the mechanical compression ratio from the input shaft, a cage that rotates together with the input shaft is fitted between the output shaft and the outer ring. In an internal combustion engine having a variable compression ratio mechanism for rotating the output shaft after pressing the roller in the rotational direction of the output shaft, the actuator is operated immediately even when there is a request to lower the mechanical compression ratio. The actuator is operated when the in-cylinder pressure of any cylinder becomes maximum.

  An internal combustion engine provided with the variable compression ratio mechanism according to claim 2 of the present invention is an internal combustion engine provided with the variable compression ratio mechanism according to claim 1, wherein the mechanical compression ratio is set when the engine speed is equal to or less than a set speed. The actuator is actuated as soon as there is a request to reduce it.

  According to the internal combustion engine including the variable compression ratio mechanism according to the first aspect of the present invention, the operating shaft is disposed between the cylinder block and the crankcase, and the operating shaft is rotated by the actuator, whereby the cylinder block is moved. An internal combustion engine having a variable compression ratio mechanism that is moved relative to a crankcase, wherein the internal compression engine has a variable compression ratio mechanism in which a reverse input cutoff clutch is disposed between an actuator and a working shaft. Even if there is a request to reduce the ratio, the actuator is not actuated immediately, and the actuator is actuated when the in-cylinder pressure of any cylinder becomes maximum.

  The reverse input shut-off clutch has an outer ring, an input shaft on the actuator side, and an output shaft on the working shaft side. The torque in the direction of decreasing the mechanical compression ratio from the output shaft is fitted between the outer ring and the output shaft. The output shaft is fixed and shut off, and the torque from the input shaft in the direction of decreasing the mechanical compression ratio is applied to the rotation of the output shaft by the roller that rotates with the input shaft is fitted between the output shaft and the outer ring. The output shaft is rotated after being pushed and removed in the moving direction. When the in-cylinder pressure of any of the cylinders becomes maximum, a large torque acts in the direction of decreasing the mechanical compression ratio from the output shaft to act on the outer ring. The roller fitted between the output shaft and the output shaft moves to the mechanical compression ratio lowering side. That is, the roller moves to a narrower side in the portion formed by the outer ring and the output shaft. As a result, even if there is a request to reduce the mechanical compression ratio, the actuator does not immediately operate, and when the in-cylinder pressure of any cylinder becomes maximum, the actuator rotates to move the moving roller. The roller is pressed in the direction, and the roller can be removed with a relatively small torque. Thus, it is possible to suppress the power consumption of the actuator for removing the roller of the reverse input cutoff clutch when the mechanical compression ratio is lowered.

  When the mechanical rotation speed is less than or equal to the set rotation speed, a relatively long time may elapse after the request to reduce the mechanical compression ratio is reached until the in-cylinder pressure of one of the cylinders reaches a maximum. If not operated, the responsiveness of changing the mechanical compression ratio deteriorates. Therefore, in the internal combustion engine provided with the variable compression ratio mechanism according to claim 2 according to the present invention, when the engine speed is equal to or lower than the set speed, the mechanical compression ratio is reduced. As soon as there is a request to reduce the actuator, the actuator is operated.

1 is an overall view of an 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 for demonstrating the operation | movement to the mechanical compression ratio increase side of the reverse input interruption | blocking clutch arrange | positioned at the variable compression ratio mechanism. It is a figure for demonstrating the operation | movement to the mechanical compression ratio fall side of the reverse input interruption | blocking clutch arrange | positioned at the variable compression ratio mechanism. It is a flowchart for controlling the actuator of a variable compression ratio mechanism. It is a time chart which shows the torque which acts from the output-shaft side of a reverse input interruption | blocking clutch. It is another time chart which shows the torque which acts from the output-shaft side of a reverse input interruption | blocking clutch.

  FIG. 1 is a side sectional view of an internal combustion engine having a variable compression ratio mechanism according to the present invention. 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 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 intake air amount detector 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 catalyst device 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.

  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 action 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.

  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 intake air amount detector 18, air-fuel ratio sensor 21, relative position sensor 22, valve timing sensor 23, and throttle opening sensor 24 are input to the input port 35 via 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. 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. 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.

  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 protrusions 50 spaced apart from each other, that is, cylinder block side supports, are formed below both side walls of the cylinder block 2, and each protrusion 50 has a circular cross section. The cam insertion hole 51 is formed. On the other hand, on the upper wall surface of the crankcase 1, there are formed a plurality of protrusions 52 that are fitted between the corresponding protrusions 50 spaced apart from each other, that is, the crankcase side support. A cam insertion hole 53 having a circular cross section is also formed in each protrusion 52.

  As shown in FIG. 2, a pair of camshafts 54, 55 are provided, and on each camshaft 54, 55, a concentric portion 58 is rotatably inserted into each cam insertion hole 53. positioned. Each concentric portion 58 is coaxial with the rotational axis of each camshaft 54, 55. On the other hand, as shown in FIG. 3, eccentric portions 57 that are eccentrically arranged with respect to the rotation axes of the camshafts 54 and 55 are positioned on both sides of each concentric portion 58. A cam 56 is eccentrically mounted for rotation. That is, the eccentric portion 57 is fitted into an eccentric hole formed in the circular cam 56, and the circular cam 56 rotates around the eccentric portion 57 around the eccentric hole. As shown in FIG. 2, the circular cams 56 are disposed on both sides of each concentric portion 58, and the 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 concentric portions 58 of the camshafts 54 and 55 are rotated in opposite directions as shown by arrows in FIG. 3A from the state shown in FIG. 3A, the eccentric portions 57 move in directions away from each other. Therefore, the circular cam 56 rotates in the direction opposite to the concentric portion 58 in the cam insertion hole 51, and the position of the eccentric portion 57 is changed from a high position to an intermediate height position as shown in FIG. Next, when the concentric portion 58 is further rotated in the direction indicated by the arrow, the eccentric portion 57 is at the lowest position as shown in FIG.

  3A, 3B, and 3C show the positional relationship between the center a of the concentric portion 58, the center b of the eccentric portion 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 concentric portion 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. A reverse input cutoff clutch 90 is disposed between the drive motor 59 and the worm 62.

  Thus, in the variable compression ratio mechanism A of the present embodiment, the drive motor 59 as an actuator rotates the camshafts 54 and 55 disposed between the cylinder block 2 and the crankcase 1 as the operating shaft. The cylinder block 2 is moved relative to the crankcase 1. The drive motor 59 rotates worm wheels 63 and 64 fixed to the end portions of the camshafts 54 and 55 as working shaft side gears by a pair of worms 61 and 62 attached to the rotating shaft as actuator side gears. The reverse input cut-off clutch 90 is positioned on the actuator side of the rotation shaft of the drive motor 59 with respect to the pair of worms 61 and 62, and is disposed between the drive motor 59 and the pair of camshafts 54 and 55.

  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 a vane 75 extending from the outer peripheral surface of the rotating shaft 73 to the inner peripheral surface of the cylindrical housing 72 between the partition walls 74, and an advance hydraulic chamber 76 on each side 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 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 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. 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. 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 high engine 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 catalyst 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. Accordingly, 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 regardless of 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 decreased in proportion to the decrease 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 a medium load L1 slightly close to the low load, the mechanical compression ratio becomes a limit mechanical compression ratio (upper limit mechanical compression) that becomes a structural limit of the combustion chamber Ratio). 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 valve closing timing of the intake valve 7 reaches the limit valve closing timing, the intake valve 7 is supplied into the combustion chamber 5 by the throttle valve 17. 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. Accordingly, when expressing the case shown in FIG. 9 so as to include both the case indicated by the solid line and the case indicated by the broken line, in the embodiment according to the present invention, the valve closing timing of the intake valve 7 becomes smaller as the engine load becomes lower. It is moved in a direction away from the intake bottom dead center BDC until the limit valve closing timing L1 at which the intake air amount supplied into the combustion chamber can be controlled. Thus, 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.

  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.

  By the way, the explosive force in the cylinder is relatively large and acts so as to move the cylinder block 2 away from the crankcase 1. If nothing is done, the camshafts 54 and 55 together with the rotating shaft of the drive motor 59 are lowered in the mechanical compression ratio. It will turn in the direction.

  The reverse input cutoff clutch 90 disposed on the rotation shaft of the drive motor 59 is provided to suppress such rotation of the camshafts 54 and 55. As shown in FIGS. 10 and 11, the reverse input cutoff clutch 90 includes a non-moving outer ring 91, an input shaft on the drive motor 59 side, and an output shaft 92 on the camshafts 54 and 55 side. Reference numeral 93 denotes a cage that rotates together with the input shaft, and 94 denotes an engaging portion of the input shaft with the output shaft 92.

  FIG. 10A shows a reverse input cutoff state in which the output shaft 92 of the reverse input cutoff clutch 90 is fixed. In such a reverse input cut-off state, even if a torque in the direction of decreasing the mechanical compression ratio indicated by the dotted arrow is applied from the camshafts 54 and 55 side to the output shaft 92 in the explosion of each cylinder, the roller 95 remains on the output shaft 92. It fits between the contact portion 92a and the stationary outer ring 91. The contact portion 92a of the output shaft 92 is formed such that the distance from the outer ring 91 gradually decreases along the circumferential direction. The roller 95 is locked to the portion between the contact portion 92a and the outer ring 91, whereby a wedge effect is generated, and the output shaft 92 is prevented from rotating in the direction of decreasing the mechanical compression ratio.

  However, as shown in FIG. 10B, when the torque in the direction of increasing the mechanical compression ratio indicated by the solid line arrow is applied from the drive motor 59 side to the input shaft in the reverse input cut-off state, the input shaft engaging portion 94 outputs. Engage with shaft 92. Next, as shown in FIG. 10C, the output shaft 92 is easily separated from the roller 95, and the output shaft 92 rotates in the direction of increasing the mechanical compression ratio indicated by the solid line arrow through the engaging portion 94 of the input shaft. can do. When the output shaft 92 is separated from the roller 95, the roller 95 is returned to the direction of the solid arrow by the spring 96.

  When the increase of the mechanical compression ratio to the target mechanical compression ratio is completed and the drive motor 59 stops, the roller 95, the input shaft engaging portion 94, and the output shaft 92 are in the positional relationship shown in FIG. It has become. In the positional relationship of each member shown in FIG. 10C, when the torque in the direction of decreasing the mechanical compression ratio indicated by the dotted arrow is applied from the camshafts 54 and 55 side to the output shaft 92 due to the explosion of each cylinder, the output shaft 92 slightly changes. Then, the reverse input blocking state shown in FIG. 10A is established, and the roller 95 is fitted between the contact portion 92a of the output shaft 92 and the stationary outer ring 91. The rotation of the output shaft 92 in the direction of decreasing the mechanical compression ratio is prevented.

  In the reverse input blocking state, the roller 95 is fitted between the abutting portion 92a of the output shaft 92 and the outer ring 91. However, when the torque in the direction of decreasing the mechanical compression ratio from the output shaft 92 side increases, The shaft 92 is twisted and elastically deformed, and the roller 95 bites into the back of the gradually narrowing portion constituted by the contact portion 92 a and the outer ring 91. The roller 95 moves to a narrow portion of the portion formed by the contact portion 92a and the outer ring 91. The output shaft 92 rotates most toward the lower mechanical compression ratio in a slight rotation range. On the other hand, when the torque in the direction of decreasing the mechanical compression ratio from the output shaft 92 side decreases, the roller 95 is gradually narrowed by the reaction portion of the elastic deformation of the output shaft 92 and is configured by the contact portion 92a and the outer ring 91. Return to the original position from the back of the part. The roller 95 moves from a narrow part to a wide part among the parts formed by the contact part 92a and the outer ring 91. The output shaft 92 rotates to the most mechanical compression ratio increase side within a slight rotation range. Thus, in the reverse input blocking state, the roller 95 is in a state of being fitted between the contact portion 92a of the output shaft 92 and the outer ring 91. However, the roller 95 is slightly changed depending on the magnitude of the torque from the output shaft 92 side. It will reciprocate in the rotation range.

  FIG. 11A also shows the same reverse input blocking state as FIG. 10A, and the output shaft 92 rotates in the mechanical compression ratio decreasing direction indicated by the dotted arrow by the torque from the camshafts 54 and 55 side. Is prevented. As shown in FIG. 11B, when the torque in the direction of decreasing the mechanical compression ratio indicated by the solid line arrow acts on the input shaft from the drive motor 59 side in the reverse input cut-off state, the engaging portion 94 of the input shaft becomes the output shaft 92. The retainer 93 that engages with the input shaft and rotates with the input shaft contacts the roller 95.

  Next, using the torque of the input shaft, the retainer 93 presses the rollers 95 in the direction of decreasing the mechanical compression ratio, and the rollers fitted between the output shaft 92 and the outer ring 91 are rotated in the rotation direction of the output shaft 92. Remove. As a result, as shown in FIG. 11C, the output shaft 92 can be rotated in the mechanical compression ratio decreasing direction via the engaging portion 94 of the input shaft.

  When the reduction of the mechanical compression ratio to the target mechanical compression ratio is completed and the drive motor 59 stops, the roller 95, the input shaft engaging portion 94, and the output shaft 92 are in the positional relationship shown in FIG. It has become. In the positional relationship of each member shown in FIG. 11C, if the torque in the direction of decreasing the mechanical compression ratio indicated by the dotted arrow is applied from the camshafts 54 and 55 side to the output shaft 92 due to the explosion of each cylinder, the output shaft 92 slightly changes. Then, the reverse input blocking state shown in FIG. 11A is established, and the roller 95 is fitted between the contact portion 92a of the output shaft 92 and the stationary outer ring 91. The rotation of the output shaft 92 in the direction of decreasing the mechanical compression ratio is prevented.

  Thus, in the case where the variable compression ratio mechanism A is provided with the reverse input cutoff clutch 90, when the mechanical compression ratio is increased, so much torque is not necessary, but when the mechanical compression ratio is decreased, nothing must be done. For example, a relatively large torque is required to remove the roller 95 fitted between the output shaft 92 and the outer ring 91 by the retainer 93, and the power consumption of the drive motor 59 is increased.

  FIG. 12 is a flowchart showing control for suppressing power consumption of the drive motor 59 of the variable compression ratio mechanism, and is implemented by the electronic control unit 30. First, in step 101, a new target mechanical compression ratio Et is set based on a change in the engine operating state (or engine load) or the like, and it is determined whether or not there is a request for changing the target mechanical compression ratio Et. When this determination is negative, it is not necessary to change the mechanical compression ratio, and the process ends.

  However, when the determination in step 101 is affirmative, it is determined whether or not the newly set target mechanical compression ratio Et is smaller than the current mechanical compression ratio E detected by the relative position sensor 22. When this determination is negative, the mechanical compression ratio is increased. At this time, a very large torque is not required, and in step 105, the actuator (drive motor 59) is made to realize a new target mechanical compression ratio Et. Operate.

  Next, at step 106, it is determined whether or not the current mechanical compression ratio E detected by the relative position sensor 22 matches the new target mechanical compression ratio Et set at step 101, and this determination is affirmed. Until step 105, the actuator is continuously operated. If the determination in step 106 is affirmative, the actuator is stopped in step 107.

  On the other hand, when the determination in step 102 is affirmed, the mechanical compression ratio is reduced. In this case, in step 103, the current engine speed N detected by the crank angle sensor 42 is less than or equal to the set speed N1. It is determined whether or not there is. When this determination is negative, in step 104, the crank angle CAPM at which the in-cylinder pressure immediately after the ignition timing becomes the maximum in the cylinder in which the current crank angle CA detected by the crank angle sensor 42 is the shortest ignition timing from the present time. It is determined whether or not it has become, and this determination is repeated until affirmative. Such a crank angle CAPM can be set in advance as a function of the ignition timing, for example.

  If the determination in step 104 is affirmative, in step 105, the actuator is operated to achieve a new target mechanical compression ratio Et. Next, at step 106, it is determined whether or not the current mechanical compression ratio E detected by the relative position sensor 22 matches the new target mechanical compression ratio Et set at step 101, and this determination is affirmed. Until step 105, the actuator is continuously operated. If the determination in step 106 is affirmative, the actuator is stopped in step 107.

  FIG. 13 is a time chart showing torque acting from the output shaft side of the reverse input cutoff clutch, and the in-cylinder pressure of each cylinder becomes maximum at times t1 ′, t1, t2, t3 immediately after the ignition timing of each cylinder, and the reverse The torque acting from the output shaft of the input cutoff clutch 90 is also maximized. For example, when there is a request for changing the target mechanical compression ratio Et to reduce the mechanical compression ratio at time t0 between time t1 'and t1, if the actuator is operated immediately, the rotation that rotates together with the input shaft is held. A relatively large torque is required to press and remove the roller 95 in the reverse input blocking state fitted between the output shaft 92 and the outer ring 91 in the rotating direction of the output shaft 92 by the device 93, and the power of the actuator It will make consumption worse.

  On the other hand, in the control of the flowchart of FIG. 12, the actuator is operated after the crank angle CAPM at which the in-cylinder pressure immediately after the ignition timing becomes the maximum in the cylinder where the current crank angle CA is the shortest ignition timing from the present. It is like that. That is, the actuator is operated when time t1 is reached.

  As described above, in the reverse input blocking state, the roller 95 is in a state of being fitted between the contact portion 92a of the output shaft 92 and the outer ring 91, but is reciprocating in a slight rotation range. When the in-cylinder pressure of any of the cylinders reaches a maximum, the cylinder is reliably moved in the direction of decreasing the mechanical compression ratio. In other words, the roller 95 is in a state of being bitten into the gradually narrowed portion constituted by the contact portion 92a and the outer ring 91. At this time, if the actuator is operated, the retainer 93 that rotates together with the input shaft rotates the roller 95 that moves so as to come out from the gradually narrowed portion constituted by the contact portion 92a and the outer ring 91. The roller 95 is pressed in the moving direction, and the roller 95 can be removed with a relatively small torque. Thus, according to the control of FIG. 12, it is possible to suppress the power consumption of the actuator for removing the roller 95 of the reverse input cutoff clutch 90 when the mechanical compression ratio is lowered.

  As described above, when reducing the mechanical compression ratio, if the actuator is operated when the in-cylinder pressure of any of the cylinders becomes maximum, the power consumption of the actuator can be suppressed. If the cylinder pressure immediately after the ignition timing becomes maximum in the cylinder that has the ignition timing in the shortest time from when there is a request to lower the mechanical compression ratio as in the control, the mechanical compression ratio can be achieved by operating the actuator. This is advantageous for responsiveness when lowering.

  Regardless of the current engine speed N, when there is a request for changing the target mechanical compression ratio Et to reduce the mechanical compression ratio, the ignition timing in the cylinder where the current crank angle CA is the shortest ignition timing from the present. Although the actuator may be operated after the crank angle CAPM at which the in-cylinder pressure immediately after reaches the maximum, in the flowchart of FIG. 12, when the current engine speed N is equal to or less than the set speed N1, that is, When the engine speed is low, the determination at step 103 is affirmative, and when there is a request for changing the target mechanical compression ratio Et for lowering the mechanical compression ratio, the actuator is immediately operated at step 105.

  When the mechanical rotational speed N is equal to or lower than the set rotational speed N1, as shown in FIG. 14, a comparison is made by the time t1 when the in-cylinder pressure of one of the cylinders becomes maximum after a request to reduce the mechanical compression ratio at the time t0. If the actuator is not operated until then, the response of changing the mechanical compression ratio is deteriorated. As a result, when the engine speed N is equal to or lower than the set speed N1, the actuator is actuated as soon as there is a request to lower the mechanical compression ratio so that the responsiveness of changing the engine compression ratio does not deteriorate.

  When the mechanical compression ratio is lowered, the power consumption of the actuator after removing the roller 95 of the reverse input cutoff clutch 90 decreases as the pressure in the cylinder increases. Accordingly, a request to lower the mechanical compression ratio only when the engine speed N is equal to or less than the set speed N1, the engine load detected by the load sensor 41 is equal to or greater than the set load, and the overall pressure in the cylinder is high. The actuator may be actuated as soon as possible. Accordingly, it is possible to suppress the deterioration of the response of the engine compression ratio change without increasing the overall power consumption of the actuator so much.

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 54,55 Camshaft 59 Drive motor 90 Reverse input interruption | blocking clutch A Variable compression ratio mechanism

Claims (2)

  An internal combustion engine comprising a variable compression ratio mechanism that displaces the cylinder block relative to the crankcase by disposing an operating shaft between the cylinder block and the crankcase and rotating the operating shaft by an actuator. A reverse input cutoff clutch is disposed between the actuator and the working shaft, and the reverse input cutoff clutch includes an outer ring, an actuator-side input shaft, and a working shaft-side output shaft. The torque in the direction of decreasing the mechanical compression ratio is blocked by a roller fitted between the outer ring and the output shaft, fixing the output shaft, and the torque in the direction of decreasing the mechanical compression ratio from the input shaft is A retainer that rotates together with the input shaft presses the roller fitted between the output shaft and the outer ring in the direction of rotation of the output shaft, and then removes the output shaft. In an internal combustion engine having a variable compression ratio mechanism to be operated, the actuator is not operated immediately even when there is a request to reduce the mechanical compression ratio, and the actuator is operated when the in-cylinder pressure of any cylinder becomes maximum. An internal combustion engine comprising a variable compression ratio mechanism characterized by the above.   2. The internal combustion engine having a variable compression ratio mechanism according to claim 1, wherein when the engine speed is equal to or lower than a set speed, the actuator is operated as soon as there is a request to lower the mechanical compression ratio.

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