JP6036676B2 - Variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine capable of changing a compression ratio.

  As an internal combustion engine mounted on an automobile or the like, a variable compression ratio device is known in which a compression ratio is variable by providing a cylinder block movably up and down with respect to a crankcase (see Patent Document 1).

  The variable compression ratio device includes a link train that links a piston that reciprocates in a cylinder and a crank pin of a crankshaft, a control shaft that is rotated and changed by a drive unit, and a link that connects the control shaft and the link train. And a control link that changes the piston stroke according to the rotational position of the control shaft. In addition, a reverse input cutoff clutch for interrupting reverse input from the control unit to the drive unit is interposed in the power transmission path from the drive unit to the control shaft, and final deceleration is performed in the power transmission path from the reverse input cutoff clutch to the control shaft. The mechanism is interposed.

JP 2007-239520 A

  In a variable compression ratio internal combustion engine equipped with a supercharger in addition to Patent Document 1, generally, the strength of a piston, a connecting rod, a crankshaft, etc., that is, the strength of a part is increased, so that preignition (also called pre-ignition or preignition) is achieved. )) To prevent damage to the piston and connecting rod.

  However, since such measures involve an increase in the weight of the variable compression ratio internal combustion engine, there is a problem in that fuel consumption is deteriorated and costs are increased.

  Accordingly, the present invention provides a variable compression ratio internal combustion engine capable of preventing damage to a piston, a connecting rod, and the like due to pre-ignition without increasing the component strength and preventing continuous occurrence of pre-ignition. With the goal.

  The present invention provides a reverse input cutoff clutch that can change a mechanical compression ratio by changing a relative position between a movable member and a stationary member by an actuator, and that blocks reverse input from the movable member to the actuator due to in-cylinder pressure. In the variable compression ratio internal combustion engine provided, the allowable in-cylinder pressure of the reverse input cutoff clutch is set lower than the in-cylinder pressure when preignition occurs, so that the reverse input cutoff clutch is damaged when preignition occurs, When the reverse input shut-off clutch is damaged, the movable member is moved by the in-cylinder pressure so that the mechanical compression ratio is reduced to a predetermined low mechanical compression ratio. The reverse input cut-off clutch is damaged and the mechanical compression ratio is reduced to a predetermined low level. When the mechanical compression ratio is lowered, the subsequent change of the mechanical compression ratio is prohibited.

  According to the present invention, it is possible to provide a variable compression ratio internal combustion engine that can prevent a piston, a connecting rod, and the like from being damaged by pre-ignition without increasing component strength, and can prevent the continuous occurrence of pre-ignition. Can do.

1 is a schematic overall view of a variable compression ratio internal combustion engine in an embodiment. It is a general | schematic exploded perspective view of the variable compression ratio mechanism in embodiment. It is a 1st schematic sectional drawing of the variable compression ratio mechanism explaining the change of the mechanical compression ratio in embodiment. It is a 2nd schematic sectional drawing of the variable compression ratio mechanism explaining the change of the mechanical compression ratio in embodiment. It is a 3rd schematic sectional drawing of the variable compression ratio mechanism explaining the change of the mechanical compression ratio in embodiment. It is the 1st schematic sectional view of the clutch in an embodiment. It is a 2nd schematic sectional drawing of the clutch in embodiment. It is the 1st schematic sectional view of a clutch when reducing the mechanical compression ratio in an embodiment. It is a 2nd schematic sectional drawing of a clutch when reducing the mechanical compression ratio in embodiment. It is a 1st schematic sectional drawing of a clutch when raising the mechanical compression ratio in embodiment. It is a figure which shows comparison with embodiment and the conventional allowable cylinder pressure. It is a flowchart of the operation control of the variable compression ratio internal combustion engine which concerns on 1st Embodiment of this invention. It is a flowchart of the operation control of the variable compression ratio internal combustion engine which concerns on 2nd Embodiment of this invention. It is a flowchart of the operation control of the variable compression ratio internal combustion engine which concerns on 3rd Embodiment of this invention. It is a figure which shows the relationship between the engine speed and engine load in the variable compression ratio internal combustion engine which concerns on 4th Embodiment of this invention. It is a flowchart of the operation control of the variable compression ratio internal combustion engine which concerns on 5th Embodiment of this invention.

  A variable compression ratio internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS. This variable compression ratio internal combustion engine includes an engine body 90. The engine body 90 includes a support structure including the crankcase 1. The support structure is formed to support the crankshaft. The engine body 90 includes the cylinder block 2 and the 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. In the present embodiment, the space surrounded by the crown surface of the piston 4, the hole of the cylinder block 2, and the cylinder head 3 at an arbitrary position of the piston 4 is referred to as a combustion chamber.

  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. The intake valve 7 opens and closes as the intake cam 49 rotates. An exhaust valve 9 is disposed at the end of the exhaust port 10. The intake port 8 is connected to a surging tank 12 via an intake branch pipe 11.

  A fuel injection valve 13 for injecting fuel into the corresponding intake port 8 is arranged in each intake branch pipe 11. Instead of being attached to the intake branch pipe 11, the fuel injection valve 13 may be arranged to inject fuel directly into each combustion chamber 5.

  The surging tank 12 is connected to an air cleaner 15 via an intake duct 14. Inside the intake duct 14, for example, an intake air amount detector 18 using heat rays is arranged. 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.

  The variable compression ratio internal combustion engine in the present embodiment includes a variable compression ratio mechanism A that can change the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center. The variable compression ratio mechanism A is formed so as to change the relative position in the cylinder axial direction of a movable member such as the cylinder block 2 with respect to a stationary member such as the crankcase 1. A lift spring 65 as an urging member is disposed between the crankcase 1 and the cylinder block 2.

  The lift spring 65 is formed so as to bias the cylinder block 2 in a direction away from the crankcase 1. The urging member is not limited to this form, and any member that urges the cylinder block 2 in a direction away from the crankcase 1 can be employed.

  A relative position sensor 22 for detecting the relative position of the cylinder block 2 with respect to the crankcase 1 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 interval between the crankcase 1 and the cylinder block 2. A throttle opening degree sensor 24 that generates an output signal indicating the opening degree of the throttle valve 17 is attached to the actuator 16 for driving the throttle valve.

  The control device for the variable compression ratio 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, 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 amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40.

  The output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. 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 °. From the output of the crank angle sensor 42, the crank angle and the engine speed can be detected.

  On the other hand, the output port 36 is connected to the ignition plug 6, the fuel injection valve 13, the actuator 16 for driving the throttle valve, and the variable compression ratio mechanism A 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 internal combustion engine in the present embodiment. FIG. 3 shows a first schematic cross-sectional view of the variable compression ratio internal combustion engine in the present embodiment. Referring to FIGS. 2 and 3, a plurality of protrusions 50 spaced from each other are formed below both side walls of cylinder block 2.

  Each protrusion 50 is formed with a cam insertion hole 51 having a circular cross section. On the other hand, the upper wall of the crankcase 1 is formed with a plurality of protrusions 52 that are fitted between the protrusions 50 at intervals. These protrusions 52 are also formed with cam insertion holes 53 having a circular cross section.

  The variable compression ratio internal combustion engine in the present embodiment includes a pair of camshafts 54 and 55. The camshafts 54 and 55 are interposed between the crankcase 1 and the cylinder block 2. On each of the cam shafts 54 and 55, circular cams 58 that are rotatably inserted into the respective cam insertion holes 53 are arranged. 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, eccentric shafts 57 arranged eccentrically with respect to the rotational axes of the respective cam shafts 54, 55 extend as shown in FIG. Another circular cam 56 is eccentrically attached to the eccentric shaft 57 so as to be rotatable. As shown in FIG. 2, the circular cams 56 are disposed on both sides of each circular cam 58.

  These circular cams 56 are rotatably inserted into the corresponding cam insertion holes 51. The cylinder block 2 is supported by the crankcase 1 via camshafts 54 and 55 including an eccentric shaft 57.

  FIG. 4 shows a second schematic cross-sectional view of the variable compression ratio mechanism in the present embodiment. FIG. 5 shows a third schematic cross-sectional view of the variable compression ratio mechanism in the present embodiment. 3 to 5 are cross-sectional views illustrating the function of the variable compression ratio mechanism when changing the mechanical compression ratio in normal operation.

  When the circular cams 58 arranged on the camshafts 54 and 55 are rotated in opposite directions from the state shown in FIG. 3, the eccentric shafts 57 move in directions toward each other.

  The eccentric shaft 57 rotates around the rotation axis of the respective camshafts 54 and 55. The cylinder block 2 moves away from the crankcase 1 as indicated by an arrow 99. At this time, the circular cam 56 rotates in the opposite direction to the circular cam 58 in the cam insertion hole 51, and the eccentric shaft 57 changes from a low position to an intermediate height position as shown in FIG.

  Next, when the circular cam 58 is further rotated in the direction indicated by the arrow 68, the cylinder block 2 further moves away from the crankcase 1 as indicated by the arrow 99. As a result, the eccentric shaft 57 is at the highest position as shown in FIG.

  3 to 5 show the positional relationship between the center b of the circular cam 58 and the center c of the circular cam 56 in each state. As can be seen by comparing FIGS. 3 to 5, the relative positions of the crankcase 1 and the cylinder block 2 are determined by the distance between the center a of the circular cam 58 and the center c of the circular cam 56.

  As the distance between the center a of the circular cam 58 and the center c of the circular cam 56 increases, the cylinder block 2 moves away from the crankcase 1. That is, in the variable compression ratio mechanism A, the relative position between the crankcase 1 and the cylinder block 2 is changed by a link mechanism using a rotating cam.

  When the cylinder block 2 is separated from the crankcase 1, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center increases. As the cylinder block 2 approaches the crankcase 1, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center is reduced. Therefore, the volume of the combustion chamber 5 when the piston 4 is positioned at the compression top dead center can be changed by rotating the camshafts 54 and 55.

  The variable compression ratio mechanism in the present embodiment includes a drive device that rotates an eccentric shaft 57 for changing the volume of the combustion chamber 5. As shown in FIG. 2, the drive device includes an actuator, for example, a motor 59 as a rotating machine, a reverse input cutoff clutch (hereinafter also referred to as a clutch) 70, worms 61 and 62, worm wheels 63 and 64, and the like.

  A pair of worms 61 and 62 having opposite spiral directions are attached to the rotating shaft 60 so that the cam shafts 54 and 55 are rotated in opposite directions. 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. The rotating machine of the driving device is not limited to the motor 59, and any device that can rotate the input shaft of the clutch 70 can be employed.

  In the present embodiment, by driving the motor 59, the volume of the combustion chamber 5 when the piston 4 is positioned at the compression top dead center can be changed over a wide range. The variable compression ratio mechanism is controlled by the electronic control unit 30, and the motor 59 that rotates the camshafts 54 and 55 is connected to the output port 36 via the corresponding drive circuit 38.

  As described above, the variable compression ratio mechanism according to the present embodiment has a variable volume of the combustion chamber 5 when the piston reaches the top dead center by moving the cylinder block 2 relative to the crankcase 1. Is formed.

  In the present embodiment, the compression ratio determined only from the stroke volume of the piston from the bottom dead center to the top dead center and the volume of the combustion chamber when the piston reaches the top dead center is referred to as a mechanical compression ratio ε. This mechanical compression ratio ε does not depend on the intake valve closing timing or the like, and (mechanical compression ratio ε) = (volume of the combustion chamber when the piston reaches top dead center + stroke volume of the piston) / ( The volume of the combustion chamber when the piston reaches top dead center).

  In the state shown in FIG. 3, the volume of the combustion chamber 5 is small and the mechanical compression ratio is high. When the intake air amount is always constant, the actual compression ratio becomes high. On the other hand, in the state shown in FIG. 5, the volume of the combustion chamber 5 is large and the mechanical compression ratio is low. When the intake air amount is always constant, the actual compression ratio is low.

  The internal combustion engine in the present embodiment can change the actual compression ratio by changing the mechanical compression ratio during the operation period. Therefore, the mechanical compression ratio may be changed by the variable compression ratio mechanism according to the operating state of the internal combustion engine. For example, as the required load increases, the amount of intake air increases and abnormal combustion such as knocking tends to occur. In this case, in a predetermined operation region, control may be performed to reduce the mechanical compression ratio as the required load increases.

  Referring to FIGS. 3 to 5, eccentric shaft 57 rotates around the rotation shaft of cam shafts 54, 55, that is, the rotation shaft of circular cam 58. In order to reduce the mechanical compression ratio, the eccentric shaft 57 is rotated in the direction indicated by the arrow 68. In order to increase the mechanical compression ratio, the eccentric shaft 57 is rotated in the direction indicated by the arrow 69.

  In the present embodiment, the rotation direction of the eccentric shaft when the cylinder block 2 is moved relative to the crankcase 1 in the direction of separating the cylinder block 2 is referred to as one rotation direction. Further, the rotation direction of the eccentric shaft 57 when the cylinder block 2 is relatively moved with respect to the crankcase 1 is referred to as the other rotation direction. In the present embodiment, arrow 68 is one rotation direction, and arrow 69 is the other rotation direction.

  Referring to FIG. 2, the variable compression ratio mechanism in the present embodiment includes a reverse input cutoff clutch 70 disposed in a driving force transmission path that transmits the rotational force (torque) of motor 59 to camshafts 54 and 55. Including. In the reverse input cut-off clutch 70 in the present embodiment, the input side is connected to a rotary shaft 66 that transmits the rotational force of the motor 59, and the output shaft is connected to a rotary shaft 60 that supports the worms 61 and 62.

  The reverse input cutoff clutch 70 in the present embodiment is formed to transmit the rotational force from the input shaft to the output shaft and to block the rotational force from the output shaft. That is, the reverse input cutoff clutch 70 transmits the rotational force of the rotary shaft 66 transmitted from the motor 59 to the worms 61, 62, and the rotational force of the rotary shaft 60 transmitted from the worms 61, 62 is interrupted. It has a structure that does not transmit to

  FIG. 6 shows a first schematic cross-sectional view of the reverse input cutoff clutch 70 in the present embodiment. FIG. 7 shows a second schematic cross-sectional view of the reverse input cutoff clutch 70 in the present embodiment. FIG. 7 is a schematic cross-sectional view taken along line X in FIG.

  Referring to FIGS. 6 and 7, reverse input cutoff clutch 70 of the present embodiment includes an outer ring 77. The outer ring 77 is fixed to the housing 78 by screws 85. The outer ring 77 is fixed without moving during the period in which the reverse input cutoff clutch 70 is driven. The reverse input cutoff clutch 70 has an output shaft 74.

  The output shaft 74 is connected to the rotating shaft 60 to which the worms 61 and 62 are fixed. The output shaft 74 rotates about the rotation center shaft 88 as a rotation center. The output shaft 74 has a hole 75. A plurality of holes 75 are formed along the circumferential direction in which the output shaft 74 rotates. The output shaft 74 in the present embodiment has a polygonal cross section. In the example shown in FIG. 6, the output shaft 74 has a regular octagonal cross-sectional shape.

  The reverse input cutoff clutch 70 includes an input shaft 71 as shown in FIG. The input shaft 71 rotates about the rotation center shaft 88 as a rotation center. The input shaft 71 is connected to a rotating shaft 66 that transmits the rotational force of the motor 59. The input shaft 71 has an insertion part 72 and a holding part 73. The insertion part 72 and the holding part 73 rotate integrally.

  The plurality of insertion portions 72 are formed at positions corresponding to the plurality of hole portions 75 of the output shaft 74. The insertion portion 72 is inserted into the hole 75 of the output shaft 74. The inner diameter of the hole portion 75 is formed to be larger than the outer shape of the insertion portion 72. A gap is formed between the insertion portion 72 and the hole 75. The plurality of holding portions 73 are disposed between the outer ring 77 and the output shaft 74.

  The holding portion 73 faces the rollers 80a and 80b. When the input shaft 71 rotates in the direction in which the eccentric shaft 57 rotates in one rotation direction, the roller 80a is pressed, and the eccentric shaft 57 moves in the other rotation direction. When the input shaft 71 rotates in the rotating direction, the roller 80b is pressed.

  Rollers 80 a and 80 b are arranged in the space between the output shaft 74 and the outer ring 77. The rollers 80a and 80b in the present embodiment are formed in a cylindrical shape. A spring 81 is disposed between the rollers 80a and 80b. The spring 81 urges the rollers 80a and 80b in a direction away from each other.

  The output shaft 74 and the outer ring 77 form locking portions 86a and 86b for locking the rollers 80a and 80b. The engaging portions 86a and 86b have portions where the distance between the end surface of the output shaft 74 and the inner surface of the outer ring 77 is gradually reduced along the direction in which the rollers 80a and 80b are urged.

  The locking portions 86a and 86b are portions where the distance between the end surface of the output shaft 74 and the inner surface of the outer ring 77 is gradually reduced along the direction in which the rollers 80a and 80b are urged. The locking portions 86a and 86b are formed narrow so that the rollers 80a and 80b do not pass through. The outer ring 77 is formed in a cylindrical shape, and the output shaft 74 is formed in a prismatic shape (an octagonal prismatic shape in the illustrated example).

  Referring to FIG. 2, reverse input cutoff clutch 70 in the present embodiment is disposed between motor 59 and worm 62, but is not limited to this configuration, and the rotational force of motor 59 is applied to camshaft 54, The driving force transmission path for transmitting to 55 can be arranged. For example, the reverse input cutoff clutch 70 may be disposed between the worm wheels 63 and 64 and the camshafts 54 and 55. In this case, a clutch can be arranged for each of the camshafts 54 and 55.

  Next, the operation of the reverse input cutoff clutch 70 in the present embodiment will be described. When the rotational force of the motor 59 is input to the input shaft 71 (see FIG. 7), the reverse input cutoff clutch 70 in the present embodiment transmits this rotational force to the output shaft 74.

  On the other hand, when the rotational force from the camshafts 54 and 55 is transmitted to the output shaft 74, the reverse input cutoff clutch 70 is locked and cuts off this rotational force. In particular, when the rotational force is transmitted from the worms 61 and 62 in the direction in which the eccentric shaft 57 rotates in one rotational direction, the reverse input cutoff clutch 70 interrupts the rotational force.

  Referring to FIG. 1, in the present embodiment, cylinder block 2 is biased by lift spring 65 in a direction away from crankcase 1. During the operation period of the internal combustion engine, a force acts in a direction in which the cylinder block 2 approaches the crankcase 1 due to the influence of gravity or the negative pressure of the combustion chamber 5 in the intake stroke of the combustion cycle.

  However, by arranging the lift spring 65, the cylinder block 2 is always urged in the direction away from the crankcase 1, and the occurrence of vibration or the like in the cylinder block 2 can be suppressed. Further, every time fuel is burned in the combustion chamber 5, a force acts in a direction in which the cylinder block 2 is separated from the crankcase 1 by the in-cylinder pressure.

  The rotational force in the direction in which the cylinder block 2 moves away from the crankcase 1 is transmitted to the reverse input cutoff clutch 70 via the camshafts 54 and 55, the worm wheels 63 and 64, and the worms 61 and 62. Referring to FIG. 6, an arrow 100 is a direction corresponding to a direction in which the cylinder block 2 moves up with respect to the crankcase 1.

  That is, the rotation direction in which the combustion chamber 5 becomes large when the mechanical compression ratio becomes small and the piston 4 reaches top dead center is shown. A force is always applied to the cylinder block 2 in a direction away from the crankcase 1, and a force is applied to the output shaft 74 in the direction indicated by the arrow 100.

  The roller 80a is pressed by the spring 81 and is in contact with the locking portion 86a. For this reason, a wedge effect is generated in the roller 80a, the rotation of the output shaft 74 with respect to the outer ring 77 is prevented, and the output shaft 74 is locked. In this way, the reverse input cutoff clutch 70 can cut off the rotational force from the output shaft corresponding to the direction in which the cylinder block 2 moves away from the crankcase 1.

  Similarly, when a rotational force in the direction opposite to the arrow 100 is applied to the output shaft 74, the roller 80b comes into contact with the locking portion 86b and the output shaft 74 is locked. Thus, in the reverse input cutoff clutch 70, when the motor 59 is not driven, the rollers 80a and 80b are locked to the locking portions 86a and 86b to lock the output shaft 74.

  FIG. 8 is a first schematic cross-sectional view of the reverse input cutoff clutch 70 for explaining the operation when the mechanical compression ratio is lowered. When lowering the mechanical compression ratio, the cylinder block 2 is moved away from the crankcase 1. By driving the motor 59, the insertion portion 72 of the input shaft 71 rotates in the direction indicated by the arrow 101. Before the insertion part 72 contacts the inner surface of the hole 75, the holding part 73 contacts the roller 80a.

  FIG. 9 is a second schematic cross-sectional view of the reverse input cutoff clutch 70 for explaining the operation when the mechanical compression ratio is lowered. By further rotating the input shaft 71, the holding portion 73 presses the roller 80a. The roller 80a is separated from the locking portion 86a. That is, the wedge effect of the roller 80a disappears.

  Therefore, the output shaft 74 is released from the locked state and can rotate in the direction indicated by the arrow 101 with respect to the outer ring 77. When the insertion portion 72 of the input shaft 71 rotates in the direction indicated by the arrow 101, the insertion portion 72 can press the hole 75 of the output shaft 74 and rotate the output shaft 74. At this time, since the output shaft 74 rotates in a direction in which the roller 80b moves away from the engaging portion 86b, the locked state by the roller 80b is also released.

  FIG. 10 is a schematic cross-sectional view of the clutch 70 for explaining the operation when raising the mechanical compression ratio. In order to increase the mechanical compression ratio, the cylinder block 2 is moved in a direction closer to the crankcase 1. By driving the motor 59, the insertion portion 72 and the holding portion 73 of the input shaft 71 are rotated in the direction indicated by the arrow 102.

  By rotating the insertion portion 72 and the holding portion 73 of the input shaft 71 in the direction indicated by the arrow 102, the holding portion 73 presses the roller 80b. The roller 80b is detached from the locking portion 86b, and the wedge effect of the roller 80b disappears. Next, when the insertion portion 72 of the input shaft 71 presses the hole 75 of the output shaft 74, the rotational force of the input shaft 71 can be transmitted to the output shaft 74.

  The output shaft 74 rotates in the direction indicated by the arrow 102. At this time, since the output shaft 74 rotates in a direction in which the roller 80a is separated from the engaging portion 86a, the locked state by the roller 80a is also released. Thus, the rotational force of the input shaft 71 can be transmitted to the output shaft 74.

  By the way, during the operation period of the engine main body 90, the in-cylinder pressure due to the combustion occurring in the combustion chamber 5 acts on the cylinder head 3. Therefore, in-cylinder pressure is applied to the cylinder block 2 in addition to the urging force of the lift spring 65 during the operation period of the engine body 90.

  With reference to FIGS. 8 and 9, when the mechanical compression ratio is decreased, the insertion portion 72 of the input shaft 71 rotates in the direction indicated by the arrow 101. The rotational force applied to the output shaft 74 indicated by the arrow 100 depends on the in-cylinder pressure. As the in-cylinder pressure increases, the rotational force applied to the output shaft 74 also increases, and the wedge effect at the locking portion 86a that locks the reverse input torque also increases. However, since the in-cylinder pressure vibrates, when the roller 80a is pressed by the holding portion 73 during the period in which the in-cylinder pressure decreases, the roller 80a can be separated from the locking portion 86b with a relatively small force.

  Referring to FIG. 10, when increasing the mechanical compression ratio, input shaft 71 rotates in the direction indicated by arrow 102. In the locking portion 86a, the input shaft 71 rotates in a direction in which the roller 80a is detached from the locking portion 86a. In the locking portion 86a, the input shaft 71 rotates in a direction in which the roller 80a is detached from the locking portion 86a. Since the holding portion 73 presses the roller 80b of the locking portion 86b on the side where the reverse input torque is not interrupted, the roller 80b can be easily detached from the locking portion 86b.

  When the reverse input acting on the reverse input cutoff clutch 70 exceeds the allowable in-cylinder pressure of the reverse input cutoff clutch 70, for example, the rollers 80a and 80b of the input cutoff clutch 70 are deformed or destroyed, and therefore the reverse input cutoff clutch 70 is fall into disrepair.

  In particular, in the variable compression ratio engine of the present embodiment, as shown in FIG. 11, the allowable in-cylinder pressure of the reverse input cutoff clutch 70 is higher than the maximum in-cylinder pressure at the normal time and lower than the in-cylinder pressure at the time of occurrence of pre-ignition. Is set. Therefore, the reverse input cutoff clutch 70 is not damaged during normal operation, and the reverse input cutoff clutch 70 is damaged when pre-ignition occurs. When the reverse input cutoff clutch 70 is damaged, the cylinder head 3 moves in a direction away from the cylinder block 1 due to the in-cylinder pressure acting on the cylinder head 3. As a result, the mechanical compression ratio is reduced to a predetermined low mechanical compression ratio. In the present embodiment, the predetermined low mechanical compression ratio is the lowest mechanical compression ratio that the variable compression ratio mechanism can take. Thereafter, changing the mechanical compression ratio is prohibited. As a result, continuous generation of pre-ignition can be prevented.

  Here, conventionally, the allowable in-cylinder pressure of other parts such as the piston, the connecting rod, and the crankshaft has been set higher than the in-cylinder pressure at the time of occurrence of pre-ignition. On the other hand, in the present embodiment, the allowable in-cylinder pressure of other components can be lowered to a value lower than the in-cylinder pressure when preignition occurs.

  In addition, in the first embodiment of the present invention, as shown in FIG. 12, a drive command is issued to the motor 59 so that the actual mechanical compression ratio (actual ε) becomes the target mechanical compression ratio (target ε). (S1). It is determined whether or not the actual ε has reached the target ε (S2). When the actual ε has not reached the target ε, the process returns to S1. When the actual ε reaches the target ε, a stop command for the motor 59 is issued (S3). Next, it is determined whether or not the actual ε is maintained at the target ε (S4). When the actual ε is maintained at the target ε, the processing cycle is ended. When the actual ε is not maintained at the target ε, it is determined that the reverse input cutoff clutch 70 is broken (S5), and a warning signal (for example, a warning lamp ON) is output (S6). At this time, the mechanical compression ratio is lowered to a predetermined low mechanical compression ratio by the in-cylinder pressure. Therefore, switching to the low compression ratio operation mode and subsequent change of the mechanical compression ratio are prohibited (S7). In the low compression ratio operation mode, engine operation control is performed based on the intake air amount, the fuel injection timing, the fuel injection amount, the ignition timing, and the like suitable when the mechanical compression ratio is a predetermined low mechanical compression ratio. .

  As a result, there is no need to increase the strength of the conventional reciprocating rotating parts that support preignition, and therefore fuel efficiency and performance can be improved, and costs can be reduced. Further, when the clutch is broken, the cylinder block 2 is automatically moved to the low compression ratio side by the in-cylinder pressure, and the mechanical compression ratio is kept low, so that subsequent preignition can be avoided.

  Therefore, according to the present embodiment, it is possible to prevent the continuous occurrence of pre-ignition without increasing the strength of parts such as pistons and connecting rods, and without accompanying an increase in weight, thereby improving fuel consumption and reducing costs. It is possible to provide a variable compression ratio internal combustion engine capable of achieving the above.

  The present invention is not limited to the above-described embodiment, and can be applied to the embodiments shown in FIGS. 13 to 15, for example. The second embodiment shown in FIG. 13 is an example in which in-cylinder pressure sensors (CPS) are attached to all cylinders. In FIG. 13, actual ε is an actual measurement value of the mechanical compression ratio, and target ε is a target value of the mechanical compression ratio.

  In the second embodiment, it is determined by the in-cylinder pressure sensor (CPS) whether or not pre-ignition has occurred in each cylinder, that is, whether or not the CPS actual measurement value is lower than the threshold value (S1). When CPS actual measurement value ≧ threshold value, that is, when pre-ignition occurs, it is determined whether or not actual ε = target ε (S2). When actual ε = target ε, the process returns to S1. When the actual ε is not equal to the target ε, it is determined that the reverse input cutoff clutch 70 has failed (broken) (S5), a warning signal (for example, a warning lamp ON) is output (S6), and the operation mode is switched to the low compression ratio operation mode. At the same time, the subsequent change in the mechanical compression ratio is prohibited (S7). When the measured CPS value <threshold value in S1, that is, when pre-ignition has not occurred, it is determined whether or not actual ε = target ε (S2 ′). When actual ε = target ε, the process returns to S1. When the actual ε is not equal to the target ε, it is determined that the transmission system parts such as the camshafts 54 and 55, the worms 61 and 62, and the rotating shaft 60 have failed (damaged) (S5 ′), and a warning signal (for example, a warning) Lamp ON) is output (S6). At this time, the mechanical compression ratio is lowered to a predetermined low mechanical compression ratio by the in-cylinder pressure. Therefore, switching to the low compression ratio operation mode and subsequent change of the mechanical compression ratio are prohibited (S7).

  The third embodiment shown in FIG. 14 is another example of detecting the holding current of the motor 59. That is, in the third embodiment, the motor 59 is driven so that the actual ε is held at the target ε. When the current supplied to the motor 59 at this time is referred to as a holding current, the holding current is normally 0, but when the relative position of the cylinder block 2 and the crankcase 1 is changed by vibration or the like, that is, the actual ε is the target ε. When the motor 59 is driven to shift the actual ε to the target ε, a holding current is generated (the target ε instruction is not changed). In this case, the absolute value of the holding current increases as the deviation of the actual ε from the target ε increases. Therefore, when the absolute value of the holding current is equal to or greater than the threshold value, it can be determined that the reverse input cutoff clutch 70 is damaged.

  Referring to FIG. 14, a drive command is issued to the motor 59 so that the actual mechanical compression ratio (actual ε) becomes the target mechanical compression ratio (target ε) (S1). It is determined whether or not the actual ε has reached the target ε (S2). When the actual ε has not reached the target ε, the process returns to S1. When the actual ε reaches the target ε, a command for holding the target ε is issued (S3). It is determined whether or not the absolute value of the holding current is smaller than a threshold value (S4). When the absolute value of the holding current is smaller than the threshold value, the processing cycle is ended. When the absolute value of the holding current is equal to or greater than the threshold value, it is determined that the reverse input cutoff clutch 70 is broken (S5), and a warning signal (for example, warning lamp ON) is output (S6). Further, the motor 59 is driven so that the actual ε becomes the minimum ε (S6a). In this way, the actual ε is quickly changed to the minimum ε. Even if the reverse input cutoff clutch 70 is damaged, the mechanical compression ratio ε can be changed by the engagement between the input shaft 71 and the output shaft 74. Next, the operation mode is switched to the low compression ratio operation mode and the subsequent change of the mechanical compression ratio is prohibited (S7).

  In the fourth embodiment, in each of the embodiments described so far, the link angle (θ in FIGS. 4 and 5) of the eccentric shaft 57 is in the vicinity of 90 ° in the load rotation region where pre-ignition is likely to occur. Is set to According to the present embodiment, since the reverse input torque due to the in-cylinder pressure becomes larger than when the link angle is other angles, the continuous occurrence of pre-ignition is prevented without increasing the strength of the piston 4, the connecting rod, and the crank. Therefore, compared with the embodiment shown in FIG. 12, for example, the performance and fuel consumption can be further improved, and the cost can be further reduced. A load rotation region in which pre-ignition is likely to occur is indicated by A in FIG.

  The fifth embodiment shown in FIG. 16 is another example of detecting the remaining amount of fuel in the fuel tank. A drive command is issued to the motor 59 so that the actual mechanical compression ratio (actual ε) becomes the target mechanical compression ratio (target ε) (S1). It is determined whether or not the actual ε has reached the target ε (S2). When the actual ε has not reached the target ε, the process returns to S1. When the actual ε reaches the target ε, a stop command for the motor 59 is issued (S3). Next, it is determined whether or not the actual ε is maintained at the target ε (S4). When the actual ε is maintained at the target ε, the processing cycle is ended. When the actual ε is not maintained at the target ε, it is determined that the reverse input cutoff clutch 70 is damaged (S5). Next, it is determined whether or not the remaining amount of fuel is OK, that is, whether or not the remaining amount of fuel is greater than a predetermined value (S5a). When the remaining amount of fuel is greater than a predetermined value, a warning signal (for example, a low ε operation warning lamp indicating that the engine is operating in the low mechanical compression ratio mode) is output (S6a), and the low compression The mode is switched to the specific operation mode and the subsequent change of the mechanical compression ratio is prohibited (S7a). That is, in this case, the mechanical compression ratio is lowered to a predetermined low mechanical compression ratio by the in-cylinder pressure or the motor 59. On the other hand, when the remaining amount of fuel is less than a predetermined value, a warning signal (for example, a high ε driving warning lamp indicating that the engine is operating in the low mechanical compression ratio mode) is output (S6b). ) And switch to the high compression ratio operation mode (S7b). That is, in this case, the mechanical compression ratio is increased to a predetermined high compression ratio by the motor 59. In the present embodiment, the predetermined high compression ratio is the highest mechanical compression ratio. In the high compression ratio operation mode, the engine operation control is performed based on the intake air amount, the fuel injection timing, the fuel injection amount, the ignition timing, and the like suitable when the mechanical compression ratio is a predetermined high mechanical compression ratio. .

  Here, in the high compression ratio operation mode, in order to suppress the occurrence of pre-ignition, the engine output is suppressed as compared with the normal operation in which the reverse input cutoff clutch 70 is not damaged. As a result, the amount of fuel consumption is suppressed, and therefore, long-distance travel is possible even when the fuel remaining in the fuel tank is small. On the other hand, in the low compression ratio operation mode, since the mechanical compression ratio is low, pre-ignition is unlikely to occur, and therefore it is not necessary to suppress the engine output.

  When the mechanical compression ratio is the maximum compression ratio, the link angle (θ in FIGS. 4 and 5) of the eccentric shaft 57 is zero. For this reason, when the mechanical compression ratio is controlled to the maximum compression ratio, the mechanical compression ratio is maintained at the maximum compression ratio even if the cylinder pressure acts on the cylinder head. As a result, the holding current of the motor 59 for maintaining the mechanical compression ratio at the maximum compression ratio is not required.

A Variable compressor mechanism 2 Cylinder block 3 Cylinder head 4 Piston 5 Combustion chamber 59 Motor 60 Rotating shaft 70 Reverse input shutoff clutch 80a, 80b Roller 90 Engine body

Claims (1)

  Variable compression with a reverse input shut-off clutch that can change the mechanical compression ratio by changing the relative position between the movable member and the stationary member by an actuator, and shuts off the reverse input from the movable member to the actuator due to in-cylinder pressure. In a specific internal combustion engine, the allowable in-cylinder pressure of the reverse input shut-off clutch is set lower than the in-cylinder pressure when pre-ignition occurs, so that the reverse input cut-off clutch is damaged when pre-ignition occurs. If the cylinder is damaged, the movable member is moved by the in-cylinder pressure so that the mechanical compression ratio is reduced to a predetermined low mechanical compression ratio. The reverse input cutoff clutch is damaged and the mechanical compression ratio is reduced to the predetermined low mechanical compression ratio. A variable compression ratio internal combustion engine which, when lowered, prohibits subsequent changes in the mechanical compression ratio.

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