JP2014173570A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine that has a variable compression ratio mechanism including a clutch and can reduce rotating force supplied to an input shaft of the clutch when lowering a mechanical compression ratio.SOLUTION: An internal combustion engine includes a variable compression ratio mechanism that changes a relative position of a cylinder block to a crankcase. The variable compression ratio mechanism has a drive unit for rotating a shaft including an eccentric shaft. The drive unit has a clutch that is disposed in a driving force transmission path for transmitting rotating force of a motor to the shaft and that cuts off reverse input. In the internal combustion engine, when a mechanical compression ratio is lowered, rotating force applied to an output shaft of the clutch is estimated, and based on the rotating force applied to the output shaft, a displacement angle of the output shaft relative to the input shaft is estimated. Based on the estimated displacement angle, rotating speed of a rotating machine is set.

Description

  The present invention relates to an internal combustion engine.

  In the combustion chamber of the internal combustion engine, the air-fuel mixture is ignited in a compressed state. It is known that the compression ratio when the air-fuel mixture is compressed affects the output and fuel consumption of the internal combustion engine. By increasing the compression ratio, the output torque can be increased and the thermal efficiency can be improved. However, it is known that abnormal combustion such as knocking occurs when the compression ratio is too high. In the prior art, an internal combustion engine that changes the compression ratio during an operation period is known.

  In Japanese Patent Application Laid-Open No. 2009-264258, a mechanical compression ratio changing mechanism capable of changing the compression ratio by changing the volume of the combustion chamber by sliding the cylinder block and the crankcase relative to each other in the axial direction of the cylinder. An internal combustion engine is disclosed. In this internal combustion engine, when the compression ratio is changed to a predetermined target compression ratio, the resistance force acting on the mechanical compression ratio changing mechanism as a resistance to the relative movement of the cylinder block is equal to or less than a predetermined reference value. Further, it is disclosed that a driving force for relatively moving a cylinder block is output to a driving source.

  In Japanese Patent Application Laid-Open No. 2007-239520, a link train that links a piston that reciprocates in a cylinder and a crank pin of a crankshaft, a control shaft that changes a rotational position by a drive unit, and the control shaft and link train There is disclosed a variable compression ratio device for an internal combustion engine that has a control link that links the control shaft and that changes the piston stroke according to the rotational position of the control shaft. In this variable compression ratio device, it is disclosed that a clutch for interrupting reverse input from the control shaft to the drive unit is interposed in a power transmission path from the drive unit to the control shaft.

JP 2009-264258 A JP 2007-239520 A

  As a variable compression ratio mechanism that changes the compression ratio, the compression ratio can be reduced by adopting a mechanism that changes the volume of the combustion chamber when the piston reaches top dead center. In an internal combustion engine equipped with such a variable compression ratio mechanism, when the fuel burns, the pressure in the combustion chamber, that is, the in-cylinder pressure rises. Further, the force acting in the direction in which the volume of the combustion chamber increases with respect to the members constituting the combustion chamber increases, and the force acting on the variable compression ratio mechanism also increases.

  In an internal combustion engine including a variable compression ratio mechanism that moves a cylinder block relative to a crankcase, force acts in a direction in which the cylinder block moves away from the crankcase due to in-cylinder pressure. As a result of this force also acting on the drive device of the variable compression ratio mechanism, there is a possibility that the rotational force is transmitted to the motor of the drive device. For this reason, it is known that a drive unit for a variable compression ratio mechanism is provided with a reverse input blocking clutch that blocks the rotational force due to the in-cylinder pressure between the motor and the shaft that moves the cylinder block. The reverse input cut-off clutch has a lock function that cuts off the rotational force generated by the cylinder pressure from being transmitted to the motor. In particular, the reverse input cut-off clutch can cut off the force in the rotation direction corresponding to the direction of rotation by the in-cylinder pressure, that is, the direction in which the cylinder block moves away from the crankcase.

  On the other hand, when the motor of the driving device is driven to move the cylinder block away from the crankcase, it is necessary to release the lock function of the reverse input cutoff clutch. However, a rotational force due to the in-cylinder pressure is applied to the output shaft of the reverse input cutoff clutch. The in-cylinder pressure changes with time, and it may be necessary to increase the rotational force supplied to the input shaft of the reverse input cutoff clutch in order to release the lock function. For this reason, the capacity of the motor of the drive device is set to be large, resulting in an increase in power consumption and an increase in fuel consumption of the internal combustion engine. Furthermore, there has been a problem that the place where the motor of the driving device is arranged becomes large or the place where the motor is arranged is limited.

  An object of the present invention is to provide an internal combustion engine that includes a variable compression ratio mechanism including a clutch and that can reduce the rotational force supplied to the input shaft of the clutch when the mechanical compression ratio is lowered.

  The internal combustion engine of the present invention has a variable structure capable of changing the mechanical compression ratio by changing the relative position of the cylinder block with respect to the support structure including the crankcase, the cylinder block supported by the support structure, and the support structure. A compression ratio mechanism. The variable compression ratio mechanism is interposed between the support structure and the cylinder block, and includes a shaft including an eccentric shaft and a drive device that rotates the shaft. The drive device includes a rotating machine and a clutch disposed in a driving force transmission path that transmits the rotational force of the rotating machine to the shaft. The clutch is formed to block transmission of the rotational force to the input shaft when a rotational force in the rotational direction corresponding to the direction in which the cylinder block moves away from the support structure is applied from the shaft to the output shaft. The internal combustion engine further includes a rotational force estimating means for estimating the rotational force applied to the output shaft of the clutch, and when the mechanical compression ratio is reduced, the output to the input shaft of the clutch is based on the rotational force applied to the output shaft of the clutch. The shaft displacement angle is estimated, the rotation speed of the input shaft of the clutch is set based on the estimated displacement angle, and the rotating machine is driven so that the rotation speed of the input shaft is set.

  In the above invention, when reducing the mechanical compression ratio, the clutch input shaft is rotated at a rotation angle larger than the displacement angle of the output shaft with respect to the input shaft during the period in which the in-cylinder pressure shifts from the maximum point to the minimum point It is preferable to make it.

  According to the present invention, it is possible to provide an internal combustion engine that includes a variable compression ratio mechanism including a clutch and can reduce the rotational force supplied to the input shaft of the clutch when the mechanical compression ratio is lowered.

1 is a schematic overall view of an internal combustion engine in an embodiment. It is a general | schematic exploded perspective view of the variable compression ratio mechanism in embodiment. 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 schematic sectional drawing of a clutch when raising the mechanical compression ratio in embodiment. It is a graph of the in-cylinder pressure with respect to the crank angle of the internal combustion engine in the embodiment. It is an expansion schematic sectional drawing of the clutch explaining a displacement angle. It is a flowchart of the operation control of the internal combustion engine in embodiment. It is a graph of the relationship between the eccentric shaft angle in the cam shaft of a variable compression ratio mechanism, and the angle coefficient regarding the rotational force transmitted in a cam shaft. It is a graph explaining the relationship between the reverse input torque and displacement angle of a clutch in an embodiment. It is a graph explaining the relationship between an engine speed and the rotational speed requested | required of a motor.

  The internal combustion engine in the embodiment will be described with reference to FIGS. In the present embodiment, a spark ignition type internal combustion engine attached to a vehicle will be described as an example. The internal combustion engine in the present embodiment includes a variable compression ratio mechanism that can change the mechanical compression ratio.

  FIG. 1 is a schematic diagram of an internal combustion engine according to an embodiment. The internal combustion engine includes a support structure including the crankcase 1. The support structure is formed to support the crankshaft. The internal combustion engine includes a cylinder block 2 and a cylinder head 3. A piston 4 is disposed in a hole formed in the cylinder block 2. A spark plug 6 is disposed at the center of the top surface of the combustion chamber 5. In the present invention, the space surrounded by the crown surface of the piston 4, the hole of the cylinder block 2, and the cylinder head 3 at the position of the arbitrary piston 4 is referred to as a combustion chamber. Further, an in-cylinder pressure sensor 23 is disposed as an in-cylinder pressure detector that detects the pressure in the combustion chamber 5, that is, the in-cylinder pressure.

  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 surge 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. The fuel injection valve 13 may be arranged so as to inject fuel directly into each combustion chamber 5 instead of being attached to the intake branch pipe 11.

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

  The 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 of the cylinder block 2 with respect to the crankcase 1 in the cylinder axial direction. A spring 65 as an urging member is disposed between the crankcase 1 and the cylinder block 2. The spring 65 is formed so as to bias the cylinder block 2 in a direction away from the crankcase 1.

  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 sensor 24 for generating an output signal indicating the throttle valve opening is attached to the actuator 16 for driving the throttle valve.

  The control device for the internal combustion engine in the present embodiment includes an electronic control unit 30. Electronic control unit 30 in the present embodiment includes a digital computer. The digital computer includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36 connected to each other by a bidirectional bus 31.

  Output signals of the intake air amount detector 18, the air-fuel ratio sensor 21, the relative position sensor 22, the in-cylinder pressure sensor 23, and the throttle opening degree 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 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 mechanism in the present embodiment. FIG. 3 shows a first schematic cross-sectional view of the variable compression ratio mechanism 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 mechanism 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 position of the eccentric shaft 57 is changed from a high 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 a of the circular cam 58, the center b of the eccentric shaft 57, and the center c of the circular cam 56 in each state. 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.

  As shown in FIG. 2, a pair of worms 61 and 62 having a spiral direction opposite to each other are attached to the rotating shaft 60 so that the camshafts 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. In this embodiment, by driving the motor 59, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center can be changed over a wide range. The variable compression ratio mechanism 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. The mechanical compression ratio does not depend on the closing timing of the intake valve, etc., (mechanical compression ratio) = (combustion chamber volume when piston reaches top dead center + piston stroke volume) / (combustion chamber volume) Volume).

  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. For example, the mechanical compression ratio can be changed by a variable compression ratio mechanism according to the operating state of the internal combustion engine.

  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 57 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 clutch 70 disposed in a driving force transmission path for transmitting the rotational force of motor 59 to camshafts 54 and 55. In the present embodiment, the clutch 70 has an input side connected to a rotary shaft 66 that transmits the rotational force of the motor 59, and an output side connected to a rotary shaft 60 that supports the worms 61 and 62.

  The clutch 70 in the present embodiment is a so-called reverse input cutoff clutch. The reverse input cutoff clutch in the present embodiment is configured 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 clutch 70 transmits the rotational force of the rotary shaft 66 transmitted from the motor 59 to the worms 61 and 62, and interrupts the rotational force of the rotary shaft 60 transmitted from the worms 61 and 62 and transmits it to the motor 59. It has a structure that does not.

  In FIG. 6, the 1st schematic sectional drawing of the clutch 70 in this Embodiment is shown. In FIG. 7, the 2nd schematic sectional drawing of the clutch 70 in this Embodiment is shown. FIG. 7 is a schematic cross-sectional view taken along line X in FIG.

  Referring to FIGS. 6 and 7, 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 clutch 70 is driven. The 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 clutch 70 includes an input shaft 71. 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 diameter 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 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.

  Next, the operation of the clutch 70 in the present embodiment will be described. Clutch 70 in the present embodiment transmits this rotational force to output shaft 74 when the rotational force of motor 59 is input to input shaft 71. On the other hand, when the rotational force from the camshafts 54 and 55 is transmitted to the output shaft 74, the clutch 70 is locked and interrupts the rotational force. In particular, the clutch 70 cuts off the rotational force 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.

  Referring to FIG. 1, in the present embodiment, cylinder block 2 is urged by 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 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, whenever 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 due to 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 clutch 70 via the camshafts 54 and 55, the worm wheels 63 and 64, and the worms 61 and 62. With reference 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 manner, the clutch 70 can block the rotational force from the output side corresponding to the direction in which the cylinder block 2 is separated 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. In the clutch 70, when the motor 59 is not driven, the rollers 80 a and 80 b are locked to the locking portions 86 a and 86 b to lock the output shaft 74.

  FIG. 8 is a first schematic cross-sectional view of the 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 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 unlocked 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 lock 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, the output shaft 74 rotates in a direction in which the roller 80a moves away from the engaging portion 86a, so that the lock by the roller 80a is also released. Thus, the rotational force of the input shaft 71 can be transmitted to the output shaft 74.

  FIG. 11 is a graph illustrating the relationship between the crank angle and the in-cylinder pressure in the internal combustion engine of the present embodiment. The internal combustion engine in the present embodiment has a plurality of cylinders. In the present embodiment, four cylinders are formed. Each cylinder is supplied with a mixture of fuel and air, and when ignited, the fuel burns and the in-cylinder pressure rises. FIG. 11 shows the in-cylinder pressures of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder in the order of ignition. The crank angle on the horizontal axis corresponds to time. The in-cylinder pressure on the vertical axis corresponds to the force acting on the cylinder block 2 via the cylinder head 3. In the in-cylinder pressure, there are a maximum point 91 at which the maximum is obtained by combustion of fuel and a minimum point 92 at which the in-cylinder pressure is minimized.

  Referring to FIG. 10, a rotational force is applied to output shaft 74 in the direction indicated by arrow 100 by the in-cylinder pressure and the urging force of spring 65. That is, reverse input torque is applied to the output shaft 74. When increasing the mechanical compression ratio, the input shaft 71 rotates in the direction indicated by the arrow 102. In the engaging portion 86a that locks the reverse input torque, the input shaft 71 rotates in a direction in which the roller 80a is detached from the engaging 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.

  Referring to FIGS. 8 and 9, when reducing the mechanical compression ratio, input shaft 71 rotates in the direction indicated by arrow 101. The rotational direction of the input shaft 71 is the same as the rotational direction of the rotational force applied to the output shaft 74 indicated by the arrow 100. The rotational force applied to the output shaft 74 depends on the in-cylinder pressure. When the in-cylinder pressure increases, the rotational force applied to the output shaft 74 also increases.

  FIG. 12 shows an enlarged schematic cross-sectional view of the clutch in the present embodiment. FIG. 12 illustrates the operation state of the clutch when the mechanical compression ratio is kept constant. The outer edges of the output shaft 74 and the roller 80a when the rotational force applied to the output shaft 74 is small are indicated by solid lines. The outer edges of the output shaft 74 and the roller 80a when the rotational force applied to the output shaft 74 is large are indicated by broken lines.

  As the rotational force applied to the output shaft 74 increases, the output shaft 74 slightly deforms in the direction indicated by the arrow 100 with respect to the input shaft 71. Thereafter, when the rotational force applied to the output shaft 74 decreases, the output shaft 74 returns to the original state. Thus, the output shaft 74 is elastically deformed, and the roller 80a bites into the engaging portion 86a. As a result, the displacement angle θ1 around the center axis of the output shaft 74 with respect to the input shaft 71 changes. The displacement angle θ1 changes elastically according to the magnitude of the rotational force applied to the output shaft 74. The displacement angle θ1 includes a displacement angle θ11 that rotates when the roller 80a bites into the engaging portion 86a, and a displacement angle θ12 that is generated by the deformation of the output shaft 74 itself. That is, the displacement angle θ1 is the sum of the displacement angle θ11 and the displacement angle θ12.

  Referring to FIG. 11, for example, when the in-cylinder pressures at reference crank angles CAa and CAb are compared, the in-cylinder pressure at crank angle CAb is higher than the in-cylinder pressure at crank angle CAa. The in-cylinder pressure rises from the crank angle CAa toward the crank angle CAb. Referring to FIG. 12, when the in-cylinder pressure increases, the displacement angle θ1 increases. That is, the roller 80a has an increased amount of biting into the engaging portion 86a, and further has an increased amount of deformation of the output shaft 74 itself. At this time, in order to reduce the mechanical compression ratio, a large force is required even if the roller 80a is pressed by the holding portion 73 to release the lock of the roller 80a.

  On the other hand, when the in-cylinder pressure decreases, the displacement angle θ1 decreases. The roller 80a is relatively moved in a direction away from the locking portion 86a. At this time, when the roller 80a is pressed by the holding portion 73, the detachment of the roller 80a from the locking portion 86a is promoted, and the locking of the roller 80a can be released with a small force.

  Referring to FIG. 11, for example, in a period S from crank angle CA1 to crank angle CA2, the in-cylinder pressure decreases and the displacement angle θ1 decreases. In order to reduce the mechanical compression ratio, in the period S in which the in-cylinder pressure is shifted from the maximum point 91 to the minimum point 92, the roller 80a can be released with a small force by starting to press the roller 80a. it can. In the present embodiment, the operation of the motor 59 of the driving device is started at the maximum point 91 of the in-cylinder pressure.

  By the way, when the period S elapses, the in-cylinder pressure rises again. The increase in the in-cylinder pressure acts in the direction in which the displacement angle θ1 increases. For this reason, it is preferable that the separation of the roller 80a from the locking portion 86a is completed within the period S in which the in-cylinder pressure decreases. That is, it is preferable that the roller 80a is separated from the locking portion 86a within the period S.

  The internal combustion engine of the present embodiment includes a rotational force estimating means for estimating the rotational force applied to the output shaft 74 of the clutch 70 during the operation period. In the present embodiment, the electronic control unit 30 functions as a rotational force estimating means. When reducing the mechanical compression ratio, the internal combustion engine estimates the displacement angle θ1 of the output shaft 74 of the clutch 70 based on the rotational force estimated by the rotational force estimating means. Based on the estimated displacement angle θ1, the rotational speed of the input shaft 71 of the clutch 70 is set, and the motor 59 is driven so that the set rotational speed of the input shaft 71 is obtained. In the present embodiment, during the period S, the input shaft 71 is controlled to rotate at a rotation angle larger than the displacement angle θ1.

  FIG. 13 shows a flowchart of the operation control of the internal combustion engine in the present embodiment. In the present embodiment, the engine speed is detected by the crank angle sensor 42 at every predetermined time interval, the relative position of the cylinder block 2 with respect to the crankcase 1 is detected by the relative position sensor 22, and the cylinder The in-cylinder pressure is detected by the internal pressure sensor 23, and these detected values are stored in the electronic control unit 30.

  In step 121, it is determined whether there is a request for changing the mechanical compression ratio. The mechanical compression ratio is selected based on the operating state of the internal combustion engine, and the target mechanical compression ratio is set. The mechanical compression ratio is set as a function of, for example, the engine speed and the fuel injection amount. In step 121, when there is no request for changing the mechanical compression ratio, this control is terminated. If there is a request to change the mechanical compression ratio in step 121, the process proceeds to step 122.

  In step 122, it is determined whether or not the target mechanical compression ratio is smaller than the current mechanical compression ratio. That is, it is determined whether or not to reduce the mechanical compression ratio. In step 122, when the target mechanical compression ratio is larger than the current mechanical compression ratio, the routine proceeds to step 130.

  In step 130, the motor 59 of the variable compression ratio mechanism driving device is operated. For example, a predetermined value can be adopted as the rotation speed of the motor 59 when the mechanical compression ratio is increased.

  Next, in step 131, it is determined whether or not the current mechanical compression ratio has reached the target mechanical compression ratio. When increasing the mechanical compression ratio, it is determined whether or not the current mechanical compression ratio is equal to or higher than the target mechanical compression ratio. In step 131, when the current mechanical compression ratio has not reached the target mechanical compression ratio, the process returns to step 130 and the operation of the motor 59 is continued. In step 131, when the current mechanical compression ratio reaches the target mechanical compression ratio, the routine proceeds to step 132. In step 132, the motor 59 is stopped.

  On the other hand, when the target mechanical compression ratio is less than the current mechanical compression ratio at step 122, the routine proceeds to step 123. That is, when reducing the mechanical compression ratio, the routine proceeds to step 123.

  In step 123, the rotational force applied to the output shaft 74 of the clutch 70 by the in-cylinder pressure and the spring 65, that is, the reverse input torque of the clutch 70 is estimated. Referring to FIGS. 1, 2, and 4, force is applied to cylinder block 2 in a direction away from crankcase 1 by in-cylinder pressure and spring 65. The force applied to the cylinder block 2 becomes a rotational force at the camshafts 54 and 55 and is transmitted to the output shaft 74 of the clutch 70 via the worm wheels 63 and 64 and the worms 61 and 62. At this time, the rotational force transmitted by the camshafts 54 and 55 varies depending on the position of the eccentric shaft 57.

  Referring to FIG. 4, in the present invention, a straight line connecting center a of circular cam 58 and center c of circular cam 56 and a straight line connecting center a of circular cam 58 and center b of eccentric shaft 57 are defined. The angle formed is referred to as the eccentric shaft angle θe. The position of the eccentric shaft 57 can be represented by an eccentric shaft angle θe.

  FIG. 14 shows a graph of the angle coefficient with respect to the eccentric shaft angle. The angle coefficient r is a coefficient by which the force applied to the cylinder block 2 is multiplied when the rotational force applied to the output shaft 74 of the clutch 70 is calculated. The angle coefficient r depends on the eccentric shaft angle θe. Even if the force applied to the cylinder block 2 is the same, the rotational force transmitted to the output shaft 74 increases as the angle coefficient r increases.

  The force applied to the cylinder block 2 by the in-cylinder pressure can be estimated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 23. Referring to FIG. 11, for example, the force applied to the cylinder block 2 can be estimated using the maximum point 91 of the immediately preceding cylinder pressure among the cylinder pressures in the plurality of cylinders. The force applied to the cylinder block 2 by the spring 65 can be estimated based on the amount of contraction of the spring 65. The amount of contraction of the spring 65 can be estimated based on, for example, the relative position of the cylinder block 2 with respect to the crankcase 1 detected by the relative position sensor 22.

  By adding the urging force due to the in-cylinder pressure and the urging force due to the spring 65, the force applied to the cylinder block 2 can be estimated. Multiplying the urging force applied to the cylinder block 2 by an angle coefficient r, and further estimating the rotational force applied to the output shaft 74 of the clutch 70 based on the gear ratio between the worms 61 and 62 and the worm wheels 63 and 64 Can do.

  Referring to FIG. 13, in step 124, displacement angle θ <b> 1 is estimated based on the rotational force applied to output shaft 74 of clutch 70. As the displacement angle θ1, a displacement angle from when the rotational force applied to the output shaft 74 is zero to when the in-cylinder pressure reaches the maximum point can be employed. Alternatively, the displacement angle when the in-cylinder pressure changes from the minimum point to the maximum point may be adopted.

  FIG. 15 is a graph illustrating the relationship between the reverse input torque T of the clutch 70 and the displacement angle θ1. As the reverse input torque T increases, the displacement angle θ1 of the output shaft 74 of the clutch 70 increases. For example, the relationship shown in FIG. 15 can be stored in the electronic control unit 30 in advance. When the rotational force applied to the output shaft 74 of the clutch 70 is the reverse input torque Tx, the displacement angle θ1x can be estimated.

  Referring to FIG. 13, next, in step 125, the rotational speed of input shaft 71 of clutch 70, that is, the rotational speed is set based on displacement angle θ <b> 1. Referring to FIG. 11, in the present embodiment, since the in-cylinder pressure of each cylinder is continuously detected, the crank in the period S from the local maximum point 91 to the local minimum point 92 in an arbitrary cylinder is determined. The width ΔCA (ΔCA = CA2−CA1) of the angle CA can be detected. Further, the engine speed at each time is detected. Based on the crank angle width ΔCA and the engine speed, the time length ts of the period S from the maximum point 91 to the minimum point 92 can be estimated. In the present embodiment, driving of the motor 59 is started at the maximum point 91 of the in-cylinder pressure. For this reason, the time length ts is set as a required time for removing the roller 80a from the locking portion 86a.

  In the present embodiment, it is preferable that the input shaft 71 of the clutch 70 rotates more than the displacement angle θ1 during the time length ts. That is, the rotational speed ω of the input shaft 71 is preferably larger than the value obtained by dividing the displacement angle θ1 by the time length ts (ω> θ1 / ts).

  FIG. 16 is a graph for explaining the relationship between the engine speed Ne and the rotational speed required for the input shaft 71 of the clutch 70. As described above, the time length ts of the period S from the maximum point 91 to the minimum point 92 is a function of the engine speed Ne. The time length ts decreases as the engine speed Ne increases. For this reason, the rotational speed ω is set higher as the engine speed Ne increases.

  Referring to FIG. 13, next, at step 126, the rotational speed of motor 59 is set. The rotational speed of the motor 59 can be set based on the rotational speed ω of the input shaft 71 of the clutch 70.

  Next, in step 127, the crank angle at which the in-cylinder pressure becomes the maximum point 91 is estimated. Referring to FIG. 11, in the present embodiment, the crank in which the first in-cylinder pressure generated in the future becomes maximum point 91 based on the crank angle, the in-cylinder pressure, and the engine speed stored in electronic control unit 30. The angle CA1 can be estimated.

  Next, at step 128, the current crank angle CA is detected. In step 129, it is determined whether or not the in-cylinder pressure has reached a crank angle CA1 at which the maximum point 91 is reached. If the current crank angle CA has not reached the crank angle CA1 at which the in-cylinder pressure becomes maximum, the process returns to step 128. In step 129, when the current crank angle CA has reached the crank angle CA1 at which the in-cylinder pressure is maximized, the routine proceeds to step 130.

  In step 130, the motor 59 of the variable compression ratio mechanism driving device is operated. When the in-cylinder pressure of any one of the plurality of cylinders reaches the maximum point 91, the operation of the motor 59 is started. The roller 80a can be detached from the locking portion 86a within a period in which the in-cylinder pressure drops from the maximum point 91 to the minimum point 92. Furthermore, the mechanical compression ratio can be reduced. The rotational speed of the motor 59 can be adjusted by any method. For example, when the motor 59 is controlled by duty control, the rotational speed can be changed by changing the duty ratio.

  Next, in step 131, it is determined whether or not the current mechanical compression ratio has reached the target mechanical compression ratio. When lowering the mechanical compression ratio, it is determined whether or not the current mechanical compression ratio is less than or equal to the target mechanical compression ratio. In step 131, when the current mechanical compression ratio has not reached the target mechanical compression ratio, the process returns to step 130 and the drive of the motor 59 is continued. In step 131, when the current mechanical compression ratio reaches the target mechanical compression ratio, the routine proceeds to step 132. In step 132, the motor 59 is stopped.

  Thus, in the internal combustion engine of the present embodiment, when the mechanical compression ratio is reduced, the displacement angle θ1 of the output shaft 74 is estimated based on the rotational force applied to the output shaft 74 of the clutch 70, and the displacement angle Based on θ1, the rotational speed of the input shaft 71 of the clutch 70 is set, and the motor 59 is driven so that the set rotational speed of the input shaft 71 is obtained. With this configuration, the rotational speed of the motor 59 can be adjusted according to the magnitude of the in-cylinder pressure, and the release of the clutch 70 during the period in which the in-cylinder pressure is rising can be suppressed. For this reason, the lock of the clutch 70 can be released with a small force, and the capacity of the motor 59 can be reduced. Alternatively, the motor 59 can be reduced in size. Alternatively, the power consumption of the drive device that drives the variable compression ratio mechanism can be reduced.

  Further, in the internal combustion engine of the present embodiment, when the mechanical compression ratio is lowered, the displacement angle θ1 of the output shaft 74 of the clutch 70 is determined within the period S in which the in-cylinder pressure shifts from the maximum point 91 to the minimum point 92. The motor 59 is driven so as to rotate the input shaft 71 of the clutch 70 at a large rotation angle. By performing this control, the unlocking of the clutch 70 can be reliably ended during the period in which the in-cylinder pressure is decreasing.

  In the present embodiment, the value of the maximum point 91 of the immediately preceding in-cylinder pressure is adopted as the in-cylinder pressure for calculating the force applied to the cylinder block 2. With this control, the rotational speed of the motor 59 can be set using a state in which the displacement angle θ1 is large, and it is possible to avoid delaying the separation of the roller 80a from the locking portion 86a. The in-cylinder pressure for calculating the force applied to the cylinder block 2 is not limited to this form, and any in-cylinder pressure can be employed.

  The drive device in the present embodiment employs the motor 59 as a rotating machine, but is not limited to this form, and any rotating machine that rotates the input shaft 71 of the clutch 70 can be employed.

  The clutch 70 in the present embodiment is disposed between the motor 59 and the worm 62, but is not limited to this form, and is disposed in a driving force transmission path that transmits the rotational force of the motor 59 to the eccentric shaft 57. be able to. For example, the clutch 70 may be disposed between the worm wheels 63 and 64 and the cam shafts 54 and 55. In this case, a clutch is arranged for each of the camshafts 54 and 55.

  The clutch in the present embodiment transmits the rotational force from the input shaft in both the rotational direction in which the mechanical compression ratio increases and the rotational direction in which the mechanical compression ratio decreases to the output shaft, and the rotational force in both directions from the output shaft is transmitted. It is formed to block. The clutch is not limited to this configuration, and may be configured to transmit the rotational force in both directions from the input shaft to the output side and to block the rotational force from the output shaft in the direction in which the mechanical compression ratio decreases. Absent.

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

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

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 4 Piston 5 Combustion chamber 22 Relative position sensor 23 In-cylinder pressure sensor 30 Electronic control unit 42 Crank angle sensor 54,55 Camshaft 56,58 Circular cam 57 Eccentric shaft 59 Motor 65 Spring 70 Clutch 71 Input shaft 73 Holding portion 74 Output shaft 80a, 80b Roller 86a, 86b Locking portion 91 Maximum point 92 Minimum point A Variable compression ratio mechanism

Claims (2)

A support structure including a crankcase;
A cylinder block supported by the support structure;
A variable compression ratio mechanism capable of changing the mechanical compression ratio by changing the relative position of the cylinder block with respect to the support structure;
The variable compression ratio mechanism includes a shaft that is interposed between the support structure and the cylinder block and includes an eccentric shaft, and a drive device that rotates the shaft.
The drive device includes a rotating machine, and a clutch disposed in a driving force transmission path that transmits the rotational force of the rotating machine to the shaft,
The clutch is configured to block transmission of the rotational force to the input shaft when a rotational force in a rotational direction corresponding to a direction in which the cylinder block moves away from the support structure is applied from the shaft to the output shaft. And
A rotation force estimating means for estimating a rotation force applied to the output shaft of the clutch;
When reducing the mechanical compression ratio, based on the rotational force applied to the output shaft of the clutch, the displacement angle of the output shaft with respect to the input shaft of the clutch is estimated, and based on the estimated displacement angle, the An internal combustion engine, wherein a rotational speed of the input shaft of the clutch is set, and the rotating machine is driven so as to reach the set rotational speed of the input shaft.   When the mechanical compression ratio is reduced, the input shaft of the clutch is rotated at a rotation angle larger than the displacement angle of the output shaft with respect to the input shaft during a period in which the in-cylinder pressure shifts from the maximum point to the minimum point. The internal combustion engine according to claim 1, wherein

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