JP2016142137A - Variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsiveness in switching a mechanical compression ratio from a low compression ratio to a high compression ratio in a variable compression ratio internal combustion engine having a variable length connecting rod.SOLUTION: A variable compression ratio internal combustion engine 1 includes a cylinder 15, a piston 5, and a connecting rod 6, and the connecting rod includes a connecting rod body 31 having a large diameter end 31a and a small diameter end 31b, and an eccentric member 32. The eccentric member turns to one direction by upward inertial force acting on a piston pin 21 by reciprocation of the piston, and thereby lifts the piston to the connecting rod body, and turns to the other direction by downward inertial force acting on the piston pin and downward explosive force acting on the piston pin by combustion of air-fuel mixture, and thereby lowers the piston to the connecting rod body. The variable compression ratio internal combustion engine further has energizing springs 16, 17, 18 and 19 which assist the lifting of the piston to the connecting rod body.SELECTED DRAWING: Figure 6

Description

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

  Conventionally, an internal combustion engine having a variable compression ratio mechanism capable of changing the mechanical compression ratio of the internal combustion engine is known. Various types of such variable compression ratio mechanisms have been proposed, and one of them is one that changes the effective length of a connecting rod used in an internal combustion engine (for example, Patent Document 1). Here, the effective length of the connecting rod means the distance between the center of the crank receiving opening for receiving the crank pin and the center of the piston pin receiving opening for receiving the piston pin. Therefore, when the effective length of the connecting rod is increased, the combustion chamber volume when the piston is at the compression top dead center is reduced, and thus the mechanical compression ratio is increased. On the other hand, when the effective length of the connecting rod is shortened, the combustion chamber volume when the piston is at the compression top dead center is increased, and thus the mechanical compression ratio is lowered.

  As a variable-length connecting rod capable of changing the effective length, one having an eccentric member (an eccentric arm or an eccentric sleeve) that is rotatable with respect to the connecting rod body is known at the small-diameter end of the connecting rod body (for example, Patent Document 1). The eccentric member has a piston pin receiving opening for receiving the piston pin, and the piston pin receiving opening is provided eccentric to the rotation axis of the eccentric member. In such a variable length connecting rod, when the rotational position of the eccentric member is changed, the effective length of the connecting rod can be changed accordingly.

  Specifically, the eccentric member lengthens the effective length of the connecting rod by rotating in one direction by an upward inertia force acting on the piston pin by the reciprocation of the piston. As a result, the piston rises with respect to the connecting rod body, and the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. On the other hand, the eccentric member rotates in the other direction by the downward inertial force acting on the piston pin by the reciprocating motion of the piston and the downward explosive force acting on the piston pin by the combustion of the air-fuel mixture. Shorten the length. As a result, the piston descends with respect to the connecting rod body, and the mechanical compression ratio is switched from the high compression ratio to the low compression ratio. Therefore, in a variable compression ratio internal combustion engine having a variable length connecting rod, the mechanical compression ratio is switched from a low compression ratio to a high compression ratio by inertial force, and is switched from a high compression ratio to a low compression ratio by inertial force and explosive force. .

JP 2011-196549 A

  By the way, the inertial force is much smaller than the explosive force. For this reason, it is difficult to obtain sufficient response when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. Further, since the inertial force is proportional to the square of the engine speed of the internal combustion engine, a sufficient inertial force cannot be obtained in the low rotation range of the internal combustion engine, and the responsiveness is further deteriorated.

  Therefore, in view of the above problems, an object of the present invention is to improve responsiveness when a mechanical compression ratio is switched from a low compression ratio to a high compression ratio in a variable compression ratio internal combustion engine having a variable length connecting rod. .

  In order to solve the above problems, a variable compression ratio internal combustion engine capable of changing a mechanical compression ratio, comprising a cylinder, a piston reciprocating in the cylinder, and a connecting rod connected to the piston via a piston pin. The connecting rod receives a piston pin, and a connecting rod body having a large diameter end portion provided with a crank receiving opening for receiving the crank pin and a small diameter end portion located on the piston side opposite to the large diameter end portion. And an eccentric member rotatably attached to the small diameter end portion, the eccentric member being configured such that the axis of the piston pin receiving opening is eccentric from the rotation axis of the eccentric member. The piston is moved upward with respect to the connecting rod body by rotating in one direction by an upward inertia force acting on the piston pin by the reciprocating motion of the piston. The piston is connected to the connecting rod body by rotating in the other direction by a downward inertia force acting on the piston pin by the reciprocating motion of the piston and a downward explosion force acting on the piston pin by the combustion of the air-fuel mixture. The variable compression ratio internal combustion engine is further configured to be lowered with respect to the variable compression ratio internal combustion engine. The variable compression ratio internal combustion engine further includes a biasing spring for assisting the piston to be lifted with respect to the connecting rod body.

  ADVANTAGE OF THE INVENTION According to this invention, in the variable compression ratio internal combustion engine which comprises a variable length connecting rod, the responsiveness when switching a mechanical compression ratio from a low compression ratio to a high compression ratio can be improved.

FIG. 1 is a schematic side sectional view of a variable compression ratio internal combustion engine. FIG. 2 is a perspective view schematically showing a variable length connecting rod according to the present invention. FIG. 3 is a sectional side view schematically showing a variable length connecting rod and a piston according to the present invention. FIG. 4 is a schematic exploded perspective view of the vicinity of the small diameter end of the connecting rod body. FIG. 5 is a schematic exploded perspective view of the vicinity of the small diameter end of the connecting rod body. FIG. 6 is a sectional side view schematically showing a variable length connecting rod and a piston according to the present invention. FIG. 7 is a cross-sectional side view of the connecting rod in which the region where the flow direction switching mechanism is provided is enlarged. 8 is a cross-sectional view of the connecting rod taken along lines VIII-VIII and IX-IX in FIG. FIG. 9 is a schematic diagram for explaining the operation of the flow direction switching mechanism when the hydraulic pressure is supplied from the hydraulic supply source to the switching pin. FIG. 10 is a schematic diagram for explaining the operation of the flow direction switching mechanism when no hydraulic pressure is supplied from the hydraulic supply source to the switching pin. FIG. 11 is an enlarged perspective view of the piston. FIG. 12 is a cross-sectional side view schematically showing a variable length connecting rod and a piston according to the present invention in which the number of auxiliary means is increased.

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

<Variable compression ratio internal combustion engine>
FIG. 1 shows a schematic side sectional view of a variable compression ratio internal combustion engine according to the present invention.
Referring to FIG. 1, reference numeral 1 denotes an internal combustion engine. The internal combustion engine 1 includes a crankcase 2, a cylinder block 3, a cylinder head 4, a piston 5, a variable length connecting rod 6, a combustion chamber 7, a spark plug 8 disposed in the center of the top surface of the combustion chamber 7, an intake valve 9, an intake air A camshaft 10, an intake port 11, an exhaust valve 12, an exhaust camshaft 13, and an exhaust port 14 are provided. The cylinder block 3 defines a cylinder 15. The piston 5 reciprocates in the cylinder 15. The internal combustion engine 1 further includes a variable valve timing mechanism A that can control the valve opening timing and the valve closing timing of the intake valve 9, and a variable valve timing mechanism that can control the valve opening timing and the valve closing timing of the exhaust valve 12. B.

  The variable length connecting rod 6 is connected to the piston 5 via the piston pin 21 at the small diameter end portion thereof, and is connected to the crank pin 22 of the crankshaft at the large diameter end portion thereof. As will be described later, the variable length connecting rod 6 can change the distance from the axis of the piston pin 21 to the axis of the crank pin 22, that is, the effective length.

  When the effective length of the variable length connecting rod 6 is increased, the length from the crank pin 22 to the piston pin 21 is increased, so that the combustion chamber 7 when the piston 5 is at the top dead center as shown by the solid line in the figure. The volume of becomes smaller. On the other hand, even if the effective length of the variable-length connecting rod 6 changes, the stroke length that the piston 5 reciprocates in the cylinder does not change. Therefore, at this time, the mechanical compression ratio in the internal combustion engine 1 is increased.

  On the other hand, if the effective length of the variable-length connecting rod 6 is shortened, the length from the crank pin 22 to the piston pin 21 is shortened, so that the combustion when the piston 5 is at the top dead center as shown by the broken line in the figure. The volume in the chamber 7 is increased. However, as described above, the stroke length of the piston 5 is constant. Therefore, at this time, the mechanical compression ratio in the internal combustion engine 1 becomes small.

<Configuration of variable length connecting rod>
FIG. 2 is a perspective view schematically showing the variable length connecting rod 6 according to the present invention, and FIG. 3 is a sectional side view schematically showing the variable length connecting rod 6 according to the present invention. As shown in FIGS. 2 and 3, the variable length connecting rod 6 includes a connecting rod body 31, an eccentric member 32 rotatably attached to the connecting rod body 31, and a first piston mechanism 33 provided on the connecting rod body 31. And a second piston mechanism 34, and a flow direction switching mechanism 35 for switching the flow of hydraulic oil to both the piston mechanisms 33, 34.

  First, the connecting rod body 31 will be described. The connecting rod body 31 has a crank receiving opening 41 for receiving the crank pin 22 of the crankshaft at one end thereof, and a sleeve receiving opening 42 for receiving a sleeve of an eccentric member 32 described later at the other end. Since the crank receiving opening 41 is larger than the sleeve receiving opening 42, the end of the connecting rod body 31 located on the side where the crank receiving opening 41 is provided (crankshaft side) is referred to as a large diameter end 31a. The end of the connecting rod body 31 located on the side where the opening 42 is provided (piston side) is referred to as a small diameter end 31b.

  In the present specification, the center axis of the crank receiving opening 41 (that is, the axis of the crank pin 22 received in the crank receiving opening 41) and the center axis of the sleeve receiving opening 42 (that is, received in the sleeve receiving opening 42). A line X (FIG. 3) extending to the center of the connecting rod body 31 is referred to as an axis of the connecting rod 6. The length of the connecting rod in the direction perpendicular to the axis X of the connecting rod 6 and perpendicular to the central axis of the crank receiving opening 41 is referred to as the connecting rod width. In addition, the length of the connecting rod in the direction parallel to the central axis of the crank receiving opening 41 is referred to as the connecting rod thickness.

  As can be seen from FIGS. 2 and 3, the width of the connecting rod body 31 is narrowest at the intermediate portion between the large-diameter end portion 31a and the small-diameter end portion 31b. Moreover, the width | variety of the large diameter edge part 31a is wider than the width | variety of the small diameter edge part 31b. On the other hand, the thickness of the connecting rod body 31 is substantially constant except for the region where the piston mechanisms 33 and 34 are provided.

  Next, the eccentric member 32 will be described. 4 and 5 are schematic perspective views of the vicinity of the small-diameter end 31b of the connecting rod body 31. FIG. 4 and 5, the eccentric member 32 is shown in an exploded state. 2 to 5, the eccentric member 32 includes a cylindrical sleeve 32 a that is received in a sleeve receiving opening 42 formed in the connecting rod body 31, and one direction in the width direction of the connecting rod body 31 from the sleeve 32 a. And a pair of second arms 32c extending from the sleeve 32a in the width direction of the connecting rod body 31 in the other direction (a direction generally opposite to the one direction). Since the sleeve 32 a is rotatable in the sleeve receiving opening 42, the eccentric member 32 is attached to the connecting rod body 31 so as to be rotatable in the circumferential direction of the small diameter end portion 31 b at the small diameter end portion 31 b of the connecting rod body 31. become. The rotational axis of the eccentric member 32 coincides with the central axis of the sleeve receiving opening 42.

  The sleeve 32 a of the eccentric member 32 has a piston pin receiving opening 32 d for receiving the piston pin 21. The piston pin receiving opening 32d is formed in a cylindrical shape. The cylindrical piston pin receiving opening 32d is formed so that its axis is parallel to the central axis of the cylindrical outer shape of the sleeve 32a, but not coaxial. Therefore, the axis of the piston pin receiving opening 32d is eccentric from the central axis of the cylindrical outer shape of the sleeve 32a, that is, the rotational axis of the eccentric member 32.

  Thus, in the present embodiment, the central axis of the piston pin receiving opening 32d of the sleeve 32a is eccentric from the rotational axis of the eccentric member 32. For this reason, when the eccentric member 32 rotates, the position of the piston pin receiving opening 32d in the sleeve receiving opening 42 changes. When the position of the piston pin receiving opening 32d is on the large diameter end portion 31a side in the sleeve receiving opening 42, the effective length of the connecting rod is shortened. On the contrary, when the position of the piston pin receiving opening 32d in the sleeve receiving opening 42 is opposite to the large diameter end portion 31a side, that is, on the small diameter end portion 31b side, the effective length of the connecting rod becomes long. Therefore, according to this embodiment, the effective length of the connecting rod 6 changes by rotating the eccentric member.

  Next, the first piston mechanism 33 will be described with reference to FIG. The first piston mechanism 33 seals the first cylinder 33a formed in the connecting rod body 31, the first piston 33b that slides in the first cylinder 33a, and the hydraulic oil supplied to the first cylinder 33a. 1 oil seal 33c. Most or all of the first cylinder 33 a is disposed on the first arm 32 b side with respect to the axis X of the connecting rod 6. In addition, the first cylinder 33a is disposed so as to be inclined with respect to the axis X so as to protrude in the width direction of the connecting rod body 31 as it approaches the small diameter end portion 31b. The first cylinder 33 a communicates with the flow direction switching mechanism 35 via the first piston communication oil passage 51.

  The first piston 33 b is connected to the first arm 32 b of the eccentric member 32 by the first connecting member 45. The first piston 33b is rotatably connected to the first connecting member 45 by a pin. As shown in FIG. 5, the first arm 32 b is rotatably connected to the first connecting member 45 by the first pin 40 at the end opposite to the side coupled to the sleeve 32 a.

  The first oil seal 33c has a ring shape and is attached around the lower end of the first piston 33b. The first oil seal 33c is in contact with the inner surface of the first cylinder 33a, and a frictional force is generated between the first oil seal 33c and the first cylinder 33a.

  Next, the second piston mechanism 34 will be described. The second piston mechanism 34 seals the second cylinder 34a formed in the connecting rod body 31, the second piston 34b sliding in the second cylinder 34a, and the hydraulic oil supplied into the second cylinder 34a. 2 oil seal 34c. Most or all of the second cylinder 34 a is arranged on the second arm 32 c side with respect to the axis X of the connecting rod 6. Further, the second cylinder 34a is disposed so as to be inclined with respect to the axis X so as to protrude in the width direction of the connecting rod body 31 as it approaches the small diameter end portion 31b. Further, the second cylinder 34 a communicates with the flow direction switching mechanism 35 via the second piston communication oil passage 52.

  The second piston 34 b is connected to the second arm 32 c of the eccentric member 32 by the second connecting member 46. The second piston 34b is rotatably connected to the second connecting member 46 by a pin. As shown in FIG. 5, the second arm 32 c is rotatably connected to the second connection member 46 by the second pin 41 at the end opposite to the side connected to the sleeve 32 a.

  The second oil seal 34c has a ring shape and is attached around the lower end of the second piston 34b. The second oil seal 34c is in contact with the inner surface of the second cylinder 34a, and a frictional force is generated between the second oil seal 34c and the second cylinder 34a.

<Operation of variable length connecting rod>
Next, operations of the eccentric member 32, the first piston mechanism 33, and the second piston mechanism 34 thus configured will be described with reference to FIG. FIG. 6A shows a state where hydraulic oil is supplied into the first cylinder 33 a of the first piston mechanism 33 and no hydraulic oil is supplied into the second cylinder 34 a of the second piston mechanism 34. . On the other hand, FIG. 6B shows that hydraulic oil is not supplied into the first cylinder 33 a of the first piston mechanism 33 and hydraulic oil is supplied into the second cylinder 34 a of the second piston mechanism 34. It shows the state.

  Here, as will be described later, the flow direction switching mechanism 35 prohibits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and allows the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. Between the first state that is permitted and the second state that permits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and prohibits the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. It can be switched with.

  When the flow direction switching mechanism 35 is in a first state that prohibits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and permits the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a, As shown in FIG. 6A, the hydraulic oil is supplied into the first cylinder 33a, and the hydraulic oil is discharged from the second cylinder 34a. For this reason, the first piston 33b rises, and the first arm 32b of the eccentric member 32 connected to the first piston 33b also rises. On the other hand, the second piston 34b is lowered, and the second arm 32c connected to the second piston 34b is also lowered. As a result, in the example shown in FIG. 6A, the eccentric member 32 is rotated in the clockwise direction in the drawing, and as a result, the position of the piston pin receiving opening 32d is raised. Therefore, the length between the center of the crank receiving opening 41 and the center of the piston pin receiving opening 32d, that is, the effective length of the connecting rod 6 is increased to L1 in the figure. That is, when the hydraulic oil is supplied into the first cylinder 33a and the hydraulic oil is discharged from the second cylinder 34a, the effective length of the connecting rod 6 is increased.

  On the other hand, the flow direction switching mechanism 35 is in a second state that permits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and prohibits the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. Then, as shown in FIG. 6B, the hydraulic oil is supplied into the second cylinder 34a, and the hydraulic oil is discharged from the first cylinder 33a. For this reason, the second piston 34b rises, and the second arm 32c of the eccentric member 32 connected to the second piston 34b also rises. On the other hand, the first piston 33b is lowered, and the first arm 32b connected to the first piston 33b is also lowered. As a result, in the example shown in FIG. 6B, the eccentric member 32 is rotated in the counterclockwise direction in the drawing, and as a result, the position of the piston pin receiving opening 32d is lowered. Therefore, the length between the center of the crank receiving opening 41 and the center of the piston pin receiving opening 32d, that is, the effective length of the connecting rod 6 is L2 shorter than L1 in the drawing. That is, when the hydraulic oil is supplied into the second cylinder 34a and the hydraulic oil is discharged from the first cylinder 33a, the effective length of the connecting rod 6 is shortened.

  In the connecting rod 6 according to the present embodiment, as described above, the effective length of the connecting rod 6 is switched between L1 and L2 by switching the flow direction switching mechanism 35 between the first state and the second state. be able to. As a result, in the internal combustion engine 1 using the connecting rod 6, the mechanical compression ratio can be changed.

  Here, when the flow direction switching mechanism 35 is in the first state, basically the eccentric member 32 rotates in one direction (clockwise in FIG. 6) without supplying hydraulic oil from the outside, The first piston 33b and the second piston 34b move to the positions shown in FIG. This is because the eccentric member 32 is rotated in the one direction by the upward inertial force acting on the piston pin 21 by the reciprocating motion of the piston 5 in the cylinder of the internal combustion engine 1, thereby causing the second piston 34 b to move. This is because the hydraulic oil in the second cylinder 34a is pushed into the first cylinder 33a. As a result, the effective length of the connecting rod 6 increases, and the piston 5 rises with respect to the connecting rod body 31. On the other hand, when the piston 5 reciprocates in the cylinder of the internal combustion engine 1 and a downward inertia force acts on the piston pin 21, or when the air-fuel mixture burns in the combustion chamber 7 and the downward force is applied to the piston pin 21. When acted, the first piston 33b is pushed in as the eccentric member 32 tries to rotate in the other direction (counterclockwise in FIG. 6). However, since the flow of the hydraulic oil from the first cylinder 33a to the second cylinder 34a is prohibited by the flow direction switching mechanism 35, the hydraulic oil in the first cylinder 33a does not flow out, so the first piston 33b is pushed in. I can't.

  On the other hand, even when the flow direction switching mechanism 35 is in the second state, the eccentric member 32 basically rotates in the other direction (counterclockwise in FIG. 6) without supplying hydraulic fluid from the outside. The first piston 33b and the second piston 34b move to the positions shown in FIG. This is because the downward inertial force acting on the piston pin 21 by the reciprocating motion of the piston 5 in the cylinder of the internal combustion engine 1 and the downward explosive force acting on the piston 5 by the combustion of the air-fuel mixture in the combustion chamber 7. This causes the eccentric member 32 to rotate in the other direction, whereby the first piston 33b is pushed in, and the hydraulic oil in the first cylinder 33a moves to the second cylinder 34a. As a result, the effective length of the connecting rod 6 is shortened, and the piston 5 is lowered with respect to the connecting rod body 31. On the other hand, when the piston 5 reciprocates in the cylinder of the internal combustion engine 1 and an upward inertial force acts on the piston 5, the eccentric member 32 tries to rotate in the one direction (clockwise in FIG. 6). The piston 34b is about to be pushed in. However, since the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a is prohibited by the flow direction switching mechanism 35, the hydraulic oil in the second cylinder 34a does not flow out, and therefore the second piston 34b is pushed in. I can't.

  Therefore, in the internal combustion engine 1, the mechanical compression ratio is switched from a low compression ratio to a high compression ratio by inertial force, and is switched from a high compression ratio to a low compression ratio by inertial force and explosive force.

<Configuration of flow direction switching mechanism>
Next, the configuration of the flow direction switching mechanism 35 will be described with reference to FIGS. FIG. 7 is a cross-sectional side view of the connecting rod in which the region where the flow direction switching mechanism 35 is provided is enlarged. 8A is a cross-sectional view of the connecting rod taken along line VIII-VIII in FIG. 7, and FIG. 8B is a cross-sectional view of the connecting rod taken along line IX-IX in FIG. 7. As described above, the flow direction switching mechanism 35 prohibits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and permits the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. Switching between one state and a second state that permits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and prohibits the flow of hydraulic oil from the second cylinder 34a to the first cylinder 33a. It is a mechanism to perform.

  As shown in FIG. 7, the flow direction switching mechanism 35 includes two switching pins 61 and 62 and one check valve 63. The two switching pins 61 and 62 and the check valve 63 are disposed between the first cylinder 33 a and the second cylinder 34 a and the crank receiving opening 41 in the axis X direction of the connecting rod body 31. The check valve 63 is disposed closer to the crank receiving opening 41 than the two switching pins 61 and 62 in the direction of the axis X of the connecting rod body 31.

  Further, the two switching pins 61 and 62 are provided on both sides with respect to the axis X of the connecting rod body 31 and the check valve 63 is provided on the axis X. Thereby, it can suppress that the weight balance of the right and left of the connecting rod main body 31 falls by providing the switching pins 61 and 62 and the check valve 63 in the connecting rod main body 31.

  The two switching pins 61 and 62 are housed in cylindrical pin housing spaces 64 and 65, respectively. In the present embodiment, the pin accommodating spaces 64 and 65 are formed such that the axis thereof extends in parallel with the central axis of the crank receiving opening 41. The switching pins 61 and 62 are slidable in the direction in which the pin accommodating space 64 extends in the pin accommodating spaces 64 and 65. That is, the switching pins 61 and 62 are disposed in the connecting rod body 31 so that the operating direction thereof is parallel to the central axis of the crank receiving opening 41.

  Moreover, the 1st pin accommodation space 64 which accommodates the 1st switching pin 61 among the two pin accommodation spaces 64 and 65 is open with respect to one side surface of the connecting rod main body 31, as shown to FIG. 8 (A). And a pin receiving hole which is closed with respect to the other side surface of the connecting rod body 31. In addition, the second pin accommodating space 65 that accommodates the second switching pin 62 out of the two pin accommodating spaces 64 and 65 corresponds to the other side surface of the connecting rod body 31 as shown in FIG. And is formed as a pin receiving hole that is open and closed with respect to the one side surface.

  The first switching pin 61 has two circumferential grooves 61a and 61b extending in the circumferential direction. These circumferential grooves 61 a and 61 b are communicated with each other by a communication path 61 c formed in the first switching pin 61. A first urging spring 67 is accommodated in the first pin accommodating space 64, and the first switching pin 61 is urged in a direction parallel to the central axis of the crank receiving opening 41 by the first urging spring 67. It is energized. In particular, in the example illustrated in FIG. 8A, the first switching pin 61 is urged toward the closed end of the first pin accommodating space 64.

  Similarly, the second switching pin 62 also has two circumferential grooves 62a and 62b extending in the circumferential direction. These circumferential grooves 62 a and 62 b are communicated with each other by a communication path 62 c formed in the second switching pin 62. A second urging spring 68 is accommodated in the second pin accommodating space 65, and the second urging spring 68 causes the second switching pin 62 to be applied in a direction parallel to the central axis of the crank receiving opening 41. It is energized. In particular, in the example illustrated in FIG. 8A, the second switching pin 62 is urged toward the closed end of the second pin housing space 65. As a result, the second switching pin 62 is biased in the opposite direction to the first switching pin 61.

  In addition, the first switching pin 61 and the second switching pin 62 are disposed in opposite directions in a direction parallel to the central axis of the crank receiving opening 41. In addition, the second switching pin 62 is urged in the opposite direction to the first switching pin 61. For this reason, in this embodiment, when hydraulic pressure is supplied to the first switching pin and the second switching pin 62, the operating directions of the first switching pin 61 and the second switching pin 62 are opposite to each other.

  The check valve 63 is accommodated in a cylindrical check valve accommodation space 66. In the present embodiment, the check valve accommodating space 66 is also formed so as to extend in parallel with the central axis of the crank receiving opening 41. The check valve 63 can move in the direction in which the check valve accommodation space 66 extends in the check valve accommodation space 66. Therefore, the check valve 63 is disposed in the connecting rod body 31 so that the operating direction thereof is parallel to the central axis of the crank receiving opening 41. The check valve accommodation space 66 is formed as a check valve accommodation hole that is open to one side surface of the connecting rod body 31 and is closed to the other side surface of the connecting rod body 31.

  The check valve 63 permits the flow from the primary side (upper side in FIG. 8B) to the secondary side (lower side in FIG. 8B) and prohibits the flow from the secondary side to the primary side. Configured as follows.

  The first pin accommodating space 64 that accommodates the first switching pin 61 is communicated with the first cylinder 33 a via the first piston communication oil passage 51. As shown in FIG. 8A, the first piston communication oil passage 51 is communicated with the first pin housing space 64 in the vicinity of the center of the connecting rod body 31 in the thickness direction. The second pin housing space 65 that houses the second switching pin 62 is communicated with the second cylinder 34 a via the second piston communication oil passage 52. As shown in FIG. 8A, the second piston communication oil passage 52 is also connected to the second pin housing space 65 in the vicinity of the center of the connecting rod body 31 in the thickness direction.

  The first piston communication oil passage 51 and the second piston communication oil passage 52 are formed by cutting from the crank receiving opening 41 with a drill or the like. Therefore, on the crank receiving opening 41 side of the first piston communication oil passage 51 and the second piston communication oil passage 52, the first extension oil passage 51a and the second extension oil passage 52a that are coaxial with the piston communication oil passages 51, 52 are provided. Is formed. In other words, the first piston communication oil passage 51 and the second piston communication oil passage 52 are formed such that the crank receiving opening 41 is positioned on the extension line. The first extension oil passage 51a and the second extension oil passage 52a are closed by a bearing metal 71 provided in the crank receiving opening 41, for example.

  The first pin accommodation space 64 that accommodates the first switching pin 61 is communicated with the check valve accommodation space 66 via the two space communication oil passages 53 and 54. Among these, as shown in FIG. 8 (A), one of the first space communication oil passages 53 is on one side surface side (lower side in FIG. 8 (B)) from the center in the thickness direction of the connecting rod body 31. The first pin accommodating space 64 and the check valve accommodating space 66 are communicated with the secondary side. The other second space communication oil passage 54 has a first pin accommodation space 64 and a check valve accommodation space 66 on the other side surface side (upper side in FIG. 8B) than the center in the thickness direction of the connecting rod body 31. To the primary side. In addition, the first space communication oil passage 53 and the second space communication oil passage 54 are configured such that the distance between the first space communication oil passage 53 and the first piston communication oil passage 51 in the connecting rod main body thickness direction and the second space communication oil passage 53 are the same. The distance in the connecting rod body thickness direction between the oil passage 54 and the first piston communication oil path 51 is arranged to be equal to the distance in the connecting rod body thickness direction between the circumferential grooves 61a and 61b.

  The second pin housing space 65 that houses the second switching pin 62 is communicated with the check valve housing space 66 through the two space communication oil passages 55 and 56. Among these, as shown in FIG. 8 (A), one third space communication oil passage 55 is on one side surface side (lower side in FIG. 8 (B)) from the center in the thickness direction of the connecting rod body 31. The first pin accommodating space 64 and the check valve accommodating space 66 are communicated with the secondary side. The other fourth space communication oil passage 56 has a first pin accommodation space 64 and a check valve accommodation space 66 on the other side surface side (upper side in FIG. 8B) than the center in the thickness direction of the connecting rod body 31. To the primary side. In addition, the third space communication oil passage 55 and the fourth space communication oil passage 56 are configured such that the distance in the connecting rod body thickness direction between the third space communication oil passage 55 and the second piston communication oil passage 52 and the fourth space communication The distance in the connecting rod body thickness direction between the oil passage 56 and the second piston communication oil path 52 is arranged to be equal to the distance in the connecting rod body thickness direction between the circumferential grooves 62a and 62b.

  These space communication oil passages 53 to 56 are formed by cutting from the crank receiving opening 41 with a drill or the like. Accordingly, extended oil passages 53a to 56a coaxial with the space communication oil passages 53 to 56 are formed on the side of the crank receiving opening 41 of the space communication oil passages 53 to 56. In other words, each of the space communication oil passages 53 to 56 is formed such that the crank receiving opening 41 is located on the extension line. These extension oil passages 53a to 56a are closed by a bearing metal 71, for example.

  As described above, the extension oil passages 51 a to 56 a are all closed by the bearing metal 71. For this reason, the extension oil passages 51a to 56a can be closed by only assembling the connecting rod 6 to the crank pin 22 using the bearing metal 71 without any additional processing for closing the extension oil passages 51a to 56a.

  In the connecting rod body 31, a first control oil passage 57 for supplying hydraulic pressure to the first switching pin 61 and a second control oil passage 58 for supplying hydraulic pressure to the second switching pin 62 are provided. Is formed. The first control oil passage 57 is communicated with the first pin housing space 64 at the end opposite to the end where the first biasing spring 67 is provided. The second control oil passage 58 is communicated with the second pin housing space 65 at the end opposite to the end where the second urging spring 68 is provided. These control oil passages 57 and 58 are formed so as to communicate with the crank receiving opening 41 and communicate with an external hydraulic supply source via an oil passage (not shown) formed in the crank pin 22. The

  Therefore, when the hydraulic pressure is not supplied from the external hydraulic pressure supply source, the first switching pin 61 and the second switching pin 62 are biased by the first biasing spring 67 and the second biasing spring 68, respectively, and FIG. As shown to (A), it will be located in the closed edge part side in the pin accommodation space 64,65. On the other hand, when the hydraulic pressure is supplied from an external hydraulic pressure supply source, the first switching pin 61 and the second switching pin 62 move against the biasing by the first biasing spring 67 and the second biasing spring 68, respectively. It will be located and will be located in the open edge part side in the pin accommodating spaces 64 and 65, respectively.

  Further, a refilling oil passage 59 is formed in the connecting rod body 31 for replenishing hydraulic oil to the primary side of the check valve 63 in the check valve housing space 66 in which the check valve 63 is housed. One end of the refilling oil passage 59 is communicated with the check valve accommodating space 66 on the primary side of the check valve 63. The other end of the refilling oil passage 59 is communicated with the crank receiving opening 41. Further, a through hole 71 a is formed in the bearing metal 71 in accordance with the supplementary oil passage 59. The replenishment oil passage 59 is communicated with an external hydraulic oil supply source through the through hole 71 a and an oil passage (not shown) formed in the crank pin 22. Therefore, the primary side of the check valve 63 communicates with the hydraulic oil supply source at all times or regularly according to the rotation of the crankshaft by the supplementary oil passage 59. In the present embodiment, the hydraulic oil supply source is a lubricating oil supply source that supplies lubricating oil to the connecting rod 6 and the like.

<Operation of flow direction switching mechanism>
Next, the operation of the flow direction switching mechanism 35 will be described with reference to FIGS. 9 and 10. FIG. 9 is a schematic diagram for explaining the operation of the flow direction switching mechanism 35 when the hydraulic pressure is supplied from the hydraulic pressure supply source 75 to the switching pins 61 and 62. FIG. 10 is a schematic diagram for explaining the operation of the flow direction switching mechanism 35 when the hydraulic pressure is not supplied from the hydraulic pressure supply source 75 to the switching pins 61 and 62. 9 and 10, the hydraulic pressure supply sources 75 that supply hydraulic pressure to the first switching pin 61 and the second switching pin 62 are depicted separately, but in this embodiment, the hydraulic pressure is supplied from the same hydraulic pressure supply source. Supplied.

  As shown in FIG. 9, when the hydraulic pressure is supplied from the hydraulic pressure supply source 75, the switching pins 61 and 62 are located at the first positions moved against the biasing force by the biasing springs 67 and 68, respectively. To do. As a result, the first piston communication oil passage 51 and the first space communication oil passage 53 are communicated by the communication passage 61 c of the first switching pin 61, and the second piston communication oil passage is communicated by the communication passage 62 c of the second switching pin 62. 52 and the fourth space communication oil passage 56 are communicated with each other. Accordingly, the first cylinder 33 a is connected to the secondary side of the check valve 63, and the second cylinder 34 a is connected to the primary side of the check valve 63.

  Here, the check valve 63 is configured such that the first space communication oil path 53 and the third space communication oil path 55 communicate with each other from the primary side where the second space communication oil path 54 and the fourth space communication oil path 56 communicate with each other. The flow of hydraulic oil to the side is allowed, but the reverse flow is prohibited. Therefore, in the state shown in FIG. 9, hydraulic oil flows from the fourth space communication oil path 56 to the first space communication oil path 53, but conversely, no hydraulic oil flows.

  As a result, in the state shown in FIG. 9, the hydraulic oil in the second cylinder 34 a flows into the second piston communication oil path 52, the fourth space communication oil path 56, the first space communication oil path 53, and the first piston communication oil. The oil can be supplied to the first cylinder 33a through the oil passage in the order of the passage 51. However, the hydraulic oil in the first cylinder 33a cannot be supplied to the second cylinder 34a. Therefore, when hydraulic pressure is supplied from the hydraulic pressure supply source 75, the flow direction switching mechanism 35 prohibits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and from the second cylinder 34a to the first cylinder 33a. It can be said that it is in the 1st state which permits the flow of hydraulic fluid to. As a result, as described above, the first piston 33b is raised and the second piston 34b is lowered, so that the effective length of the connecting rod 6 becomes longer as indicated by L1 in FIG. 6 (A).

  On the other hand, as shown in FIG. 10, when the hydraulic pressure is not supplied from the hydraulic pressure supply source 75, the switching pins 61 and 62 are located at the second positions urged by the urging springs 67 and 68, respectively. As a result, the first piston communication oil path 51 and the second space communication oil path 54 communicating with the first piston mechanism 33 are communicated with each other by the communication path 61 c of the first switching pin 61. In addition, the second piston communication oil passage 52 and the third space communication oil passage 55 communicated with the second piston mechanism 34 are communicated with each other by the communication passage 62 c of the second switching pin 62. Accordingly, the first cylinder 33 a is connected to the primary side of the check valve 63, and the second cylinder 34 a is connected to the secondary side of the check valve 63.

  Due to the action of the check valve 63 described above, in the state shown in FIG. 10, the hydraulic oil in the first cylinder 33 a is transferred to the first piston communication oil passage 51, the second space communication oil passage 54, and the third space communication oil passage. 55 and the second piston communication oil passage 52 can be supplied to the second cylinder 34a through the oil passage. However, the hydraulic oil in the second cylinder 34a cannot be supplied to the first cylinder 33a. Therefore, when the hydraulic pressure is not supplied from the hydraulic pressure supply source 75, the flow direction switching mechanism 35 permits the flow of hydraulic oil from the first cylinder 33a to the second cylinder 34a and from the second cylinder 34a to the first cylinder 33a. It can be said that it is in the 2nd state which prohibits the flow of the hydraulic oil to. As a result, as described above, the second piston 34b is raised and the first piston 33b is lowered, so that the effective length of the connecting rod 6 is shortened as indicated by L2 in FIG. 6 (A).

  In the present embodiment, as described above, the hydraulic oil moves back and forth between the first cylinder 33a of the first piston mechanism 33 and the second cylinder 34a of the second piston mechanism 34. For this reason, basically, it is not necessary to supply hydraulic oil from the outside of the first piston mechanism 33, the second piston mechanism 34, and the flow direction switching mechanism 35. However, there is a possibility that hydraulic oil leaks to the outside from the oil seals 33c, 34c, etc. provided in these mechanisms 33, 34, 35, and if such hydraulic oil leaks, it is replenished from outside. Is required.

  In the present embodiment, the replenishment oil passage 59 communicates with the primary side of the check valve 63, whereby the primary side of the check valve 63 communicates with the hydraulic oil supply source 76 constantly or periodically. Therefore, even if the hydraulic oil leaks from the mechanisms 33, 34, 35, etc., the hydraulic oil can be replenished.

  Furthermore, in this embodiment, the flow direction switching mechanism 35 is in the first state when the hydraulic pressure is supplied from the hydraulic pressure supply source 75 to the switching pins 61 and 62, and the effective length of the connecting rod 6 is increased. When the hydraulic pressure is not supplied from the supply source 75 to the switching pins 61 and 62, the second state is established, and the effective length of the connecting rod 6 is shortened. Thereby, for example, when the hydraulic pressure cannot be supplied due to a failure in the hydraulic supply source 75 or the like, the effective length of the connecting rod 6 can be kept short, and thus the mechanical compression ratio is kept low. Will be able to.

  By the way, when the mechanical compression ratio is increased, the distance between the top surface of the piston 5 and the intake valve 9 and the exhaust valve 12 when the piston 5 is at the top dead center is larger than when the mechanical compression ratio is decreased. Shorter. For this reason, if the mechanical compression ratio is kept high when the hydraulic pressure cannot be supplied, the piston 5 and the intake valve 9 or the exhaust valve 12 may collide. For example, when the opening timing of the intake valve 9 is advanced by controlling the variable valve timing mechanism A, or when the closing timing of the intake valve 9 is retarded by controlling the variable valve timing mechanism A The piston 5 and the intake valve 9 may collide with each other. However, in this embodiment, when the hydraulic pressure cannot be supplied, the collision between the piston 5 and the intake valve 9 or the exhaust valve 12 can be prevented by keeping the mechanical compression ratio low.

  Further, when the internal combustion engine 1 is stopped in a state where the mechanical compression ratio is high and the internal combustion engine 1 is restarted in a high temperature state, knocking may occur if the mechanical compression ratio is kept high. However, in this embodiment, since the hydraulic pressure is not supplied when the internal combustion engine 1 is stopped, the internal combustion engine 1 is restarted in a state where the mechanical compression ratio is lowered. For this reason, in this embodiment, generation | occurrence | production of knocking at the time of high temperature restart can be suppressed.

  However, in a low load range where the required torque is small, it is desirable to increase the mechanical compression ratio in order to improve fuel efficiency. Therefore, when the internal combustion engine 1 is restarted, it may be required to quickly switch the mechanical compression ratio from the low compression ratio to the high compression ratio. In some cases, it is required to quickly switch the mechanical compression ratio from a low compression ratio to a high compression ratio in a low rotation range such as an idling state.

  However, as described above, in the internal combustion engine 1, the mechanical compression ratio is switched from the low compression ratio to the high compression ratio by the inertial force, and is switched from the high compression ratio to the low compression ratio by the inertial force and the explosion force. The inertial force is much smaller than the explosive force. For this reason, it is difficult to obtain sufficient response when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. Further, since the inertial force is proportional to the square of the engine speed of the internal combustion engine 1, a sufficient inertial force cannot be obtained in the low rotational speed region of the internal combustion engine 1, and the response is further deteriorated.

<Configuration of auxiliary means>
Therefore, in this embodiment, the internal combustion engine 1 further includes auxiliary means for assisting the raising of the piston 5 relative to the connecting rod body 31 in order to improve the response when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. Have. In this embodiment, as well shown in FIGS. 3 and 6, the auxiliary means are the third biasing spring 16 and the fourth biasing spring 17, and the third biasing spring 16 and the fourth biasing spring 17 are It is a coil spring.

  The third urging spring 16 urges the eccentric member 32 to rotate in the one direction (clockwise in FIG. 6) via the first connecting member 45 connected to the eccentric member 32. A disc-shaped third biasing spring support member 33d is attached to the opening end of the first cylinder 33a on the piston 5 side. In the center of the third biasing spring support member 33d, a hole through which the first connecting member 45 passes is provided. Moreover, the 1st connection member 45 has the disk-shaped 3rd biasing spring contact part 45a fixed to the position spaced apart to the piston 5 side from the opening edge part of the 1st cylinder 33a. The third biasing spring 16 is disposed between the third biasing spring support member 33d and the third biasing spring contact portion 45a so as to surround the first connecting member 45.

  As shown in FIG. 6, when the mechanical compression ratio is switched between a low compression ratio (see FIG. 6B) and a high compression ratio (see FIG. 6A), the eccentric member 32 rotates. Thus, the distance between the third biasing spring support member 33d and the third biasing spring contact portion 45a changes. As a result, the third biasing spring 16 expands and contracts between the third biasing spring support member 33d and the third biasing spring contact portion 45a. The natural length of the third urging spring 16 is longer than the length between the third urging spring support member 33d and the third urging spring contact portion 45a. Therefore, the third biasing spring 16 biases the eccentric member 32 to rotate in the one direction (clockwise in FIG. 6) while the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. In addition, it is possible to assist the raising of the piston 5 with respect to the connecting rod body 31. This improves the responsiveness when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio.

  Further, the force required to raise the piston 5 with respect to the connecting rod body 31 is maximized when the piston 5 starts to rise, that is, in the low compression ratio state shown in FIG. This is because static frictional force is generated between the first cylinder 33a and the first oil seal 33c of the first piston mechanism 33 and between the second cylinder 34a and the second oil seal 34c of the second piston mechanism 34 at this time. This is because it occurs. As shown in FIG. 6, the amount of compression of the third biasing spring 16 is maximum in the low compression ratio state and minimum in the high compression ratio state. For this reason, the urging force of the third urging spring 16 is maximum in the low compression ratio state and is minimum in the high compression ratio state. Therefore, the third urging spring 16 can generate the maximum urging force when the force necessary to raise the piston 5 with respect to the connecting rod body 31 is maximized. It can effectively assist the rise.

  The fourth urging spring 17 urges the piston 5 upward with respect to the connecting rod body 31. FIG. 11 is an enlarged perspective view of the piston 5. As shown in FIG. 11, the piston 5 has a fourth biasing spring holding portion 5a on the inner surface thereof. The fourth urging spring holding portion 5a is a cylindrical groove. Further, as shown in FIGS. 3 and 6, a lifter 50 is disposed between the small diameter end portion 31 b of the connecting rod body 31 and the piston 5. The lifter 50 has a cylindrical shape. The fourth urging spring 17 is received by the fourth urging spring holding portion 5 a and abuts against the inner surface of the lifter 50. For this reason, the lifter 50 is biased to the small diameter end portion 31 b of the connecting rod body 31 by the fourth biasing spring 17. When the connecting rod 6 swings as the piston 5 reciprocates in the cylinder 15, the small diameter end portion 31 b of the connecting rod 6 slides on the outer surface of the lifter 50.

  As shown in FIG. 6, when the mechanical compression ratio is switched between the low compression ratio and the high compression ratio, the piston 5 moves up and down with respect to the connecting rod body 31, so that the piston 5 and the small diameter of the connecting rod body 31 The distance between the lifter 50 disposed on the end 31b changes. As a result, the fourth biasing spring 17 expands and contracts between the piston 5 and the lifter 50. The natural length of the fourth urging spring 17 is such that the fourth urging spring holding portion 5a (the portion that supports the fourth urging spring 17) and the lifter 50 (the portion where the fourth urging spring 17 abuts). Longer than the length between. Therefore, the fourth urging spring 17 can urge the piston 5 upward while the mechanical compression ratio is switched from the low compression ratio to the high compression ratio, and can assist the piston 5 to rise relative to the connecting rod body 31. . This improves the responsiveness when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio.

  Further, as shown in FIG. 6, the compression amount of the fourth urging spring 17 is maximum in the low compression ratio state and minimum in the high compression ratio state. For this reason, the urging force of the fourth urging spring 17 is maximum in the low compression ratio state and is minimum in the high compression ratio state. Therefore, the fourth urging spring 17 can generate the maximum urging force when the force necessary to raise the piston 5 with respect to the connecting rod body 31 is maximized. It can effectively assist the rise.

  FIG. 12 is a cross-sectional side view schematically showing the variable length connecting rod 6 and the piston 5 according to the present invention in which the number of auxiliary means is increased. In the example shown in FIG. 12, a fifth biasing spring 18 and a sixth biasing spring 19 are added as auxiliary means in addition to the third biasing spring 16 and the fourth biasing spring 17. In the present embodiment, the fifth biasing spring 18 is a torsion spring, and the sixth biasing spring 19 is a coil spring.

  The fifth biasing spring 18 is applied to rotate the eccentric member 32 in the one direction (clockwise in FIG. 12) via the first pin 40 that connects the eccentric member 32 and the first connecting member 45. Rush. The connecting rod body 31 has a fifth urging spring support portion 31d between the large diameter end portion 31a and the small diameter end portion 31b. The fifth biasing spring support portion 31 d has a cylindrical shape and protrudes in the thickness direction of the connecting rod 6. The center of the fifth urging spring support portion 31 d is located on the second arm 32 c side with respect to the axis X of the connecting rod 6. The fifth biasing spring 18 is wound around the sleeve 32 a of the eccentric member 32, one end thereof is supported by the fifth biasing spring support portion 31 d, and the other end abuts on the first pin 40.

  The fifth biasing spring 18 is disposed so as to be always bent from the low compression ratio state to the high compression ratio state. For this reason, the fifth biasing spring 18 biases the eccentric member 32 to rotate in the one direction (clockwise in FIG. 12) while the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. In addition, it is possible to assist the raising of the piston 5 with respect to the connecting rod body 31. This improves the responsiveness when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio.

  Also, as shown in FIG. 12, when the mechanical compression ratio is switched between the low compression ratio and the high compression ratio, the eccentric member 32, and hence the first pin 40, rotates, so that the fifth biasing spring 18 is rotated. The amount of deflection changes. The amount of deflection of the fifth biasing spring 18 is maximum in the low compression ratio state and minimum in the high compression ratio state. For this reason, the urging force of the fifth urging spring 18 is maximum in the low compression ratio state and is minimum in the high compression ratio state. Therefore, the fifth biasing spring 18 can generate the maximum biasing force when the force necessary to raise the piston 5 with respect to the connecting rod body 31 is maximized. It can effectively assist the rise.

  The sixth urging spring 19 urges the eccentric member 32 to rotate in the one direction (clockwise in FIG. 12) via the second connecting member 46 connected to the eccentric member 32, and the piston Energize 5 upwards. The piston 5 has a sixth biasing spring holding portion 5b on its inner surface. The sixth biasing spring holding part 5b has the same shape as the fourth biasing spring holding part 5a. The sixth urging spring 19 is received by the sixth urging spring holding portion 5b and abuts on the end of the second connecting member 46 on the piston 5 side.

  As shown in FIG. 12, when the mechanical compression ratio is switched between the low compression ratio and the high compression ratio, the eccentric member 32 rotates and the piston 5 moves up and down with respect to the connecting rod body 31. The distance between 5 and the second connecting member 46 changes. As a result, the sixth biasing spring 19 expands and contracts between the piston 5 and the second connecting member 46. In addition, the natural length of the sixth biasing spring 19 is longer than the length between the sixth biasing spring holding portion 5 b (the portion that supports the sixth biasing spring 19) and the second connecting member 46. Therefore, the sixth urging spring 19 urges the eccentric member 32 to rotate in the one direction (clockwise in FIG. 12) while the mechanical compression ratio is switched from the low compression ratio to the high compression ratio. At the same time, the piston 5 can be urged upward to assist the raising of the piston 5 relative to the connecting rod body 31. This improves the responsiveness when the mechanical compression ratio is switched from the low compression ratio to the high compression ratio.

  On the other hand, when the mechanical compression ratio is switched from the high compression ratio to the low compression ratio, that is, when the piston 5 is lowered with respect to the connecting rod body 31, the urging force by the urging springs 16, 17, 18, 19 becomes a resistance force. However, when the mechanical compression ratio is switched from the high compression ratio to the low compression ratio, an explosion force acts on the eccentric member 32 in addition to the inertial force. For this reason, sufficient responsiveness can be ensured irrespective of the resistance force by the biasing springs 16, 17, 18, and 19.

  Further, the force required to lower the piston 5 with respect to the connecting rod body 31 becomes maximum when the piston 5 starts to descend, that is, in the high compression ratio state shown in FIG. This is because static frictional force is generated between the first cylinder 33a of the first piston mechanism 33 and the first oil seal 33c and between the second cylinder 34a of the second piston mechanism 34 and the second oil seal. Because it does. As described above, the urging force of the urging springs 16, 17, 18, and 19 is minimized in the high compression ratio state. Therefore, the resistance force by the urging springs 16, 17, 18, 19 is minimized when the force necessary for lowering the piston 5 relative to the connecting rod body 31 is maximized. For this reason, it can suppress that the responsiveness at the time of switching a mechanical compression ratio from a high compression ratio to a low compression ratio by the resistance force by the urging | biasing springs 16, 17, 18, and 19 can be suppressed.

  The preferred embodiments according to the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. For example, the auxiliary means may be any one of the urging springs 16, 17, 18, 19 or any combination of the urging springs 16, 17, 18, 19. Further, the auxiliary means may have any shape or arrangement as long as it is an urging spring that can assist the raising of the piston 5 with respect to the connecting rod body 31. The number of piston mechanisms may be one.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Piston 6 Connecting rod 15 Cylinder 16 3rd biasing spring 17 4th biasing spring 18 5th biasing spring 19 6th biasing spring 21 Piston pin 22 Crankpin 31 Connecting rod main body 32 Eccentric member 33 1st piston mechanism 34 Second piston mechanism 35 Flow direction switching mechanism

Claims (1)

A variable compression ratio internal combustion engine capable of changing a mechanical compression ratio,
A cylinder, a piston reciprocating in the cylinder, and a connecting rod connected to the piston via a piston pin;
The connecting rod is
A connecting rod body having a large-diameter end portion provided with a crank receiving opening for receiving a crankpin, and a small-diameter end portion located on the piston side opposite to the large-diameter end portion;
An eccentric member having a piston pin receiving opening for receiving the piston pin and pivotally attached to the small diameter end,
The eccentric member is configured such that an axis of the piston pin receiving opening is eccentric from a rotation axis of the eccentric member, and one direction is generated by an upward inertia force acting on the piston pin by the reciprocation of the piston. The piston is lifted with respect to the connecting rod body by rotating to the downward direction, and the downward inertia force acting on the piston pin by the reciprocating motion of the piston and the downward force acting on the piston pin by combustion of the air-fuel mixture The piston is lowered with respect to the connecting rod body by rotating in the other direction by the explosion force of
The variable compression ratio internal combustion engine is further provided with a biasing spring that assists the raising of the piston with respect to the connecting rod body.

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