JP4730335B2 - Internal combustion engine compression ratio changing device - Google Patents

Description

  The present invention relates to a compression ratio changing device for an internal combustion engine that changes a compression ratio that is a ratio of a maximum value to a minimum value of a volume of a combustion chamber that changes with movement of a piston.

  Conventionally applied to an internal combustion engine, by moving a cylinder block relative to a crankcase in an axial direction (center axis) of a cylinder bore (hereinafter also referred to as “vertical direction” or “bore central axis direction”), An internal combustion engine compression ratio changing device for changing the compression ratio has been proposed.

  For example, one such compression ratio changing device is a conceptual diagram for explaining the operation of the device, as shown in FIGS. 1A, 1B and 1C, in the direction of the bore center axis. An internal combustion engine compression ratio changing device 930 applied to the internal combustion engine, which includes a cylinder block 910 having a cylinder bore CB penetrating through the cylinder block 910 and a crankcase 920 disposed below the cylinder block 910 and fixed to the vehicle body. is there.

  The compression ratio changing device 930 includes a block-side force receiving portion 931 fixed to the outer wall surface (side wall surface) 911 of the cylinder block 910, a case-side force receiving portion 932 formed on the upper portion of the crankcase 920, and a block-side receiving member. A link mechanism 933 that couples the force portion 931 and the case-side force receiving portion 932 to each other.

  The link mechanism 933 includes a columnar block side rotating member 934, a columnar case side rotating member 935, and a columnar link shaft portion 936.

  The block-side rotating member 934 is disposed in a through hole formed in the block-side force receiving portion 931. The block-side rotating member 934 is supported rotatably about its center axis (block-side force receiving axis) MC.

  The case side rotating member 935 is disposed in a through hole formed in the case side force receiving portion 932. The case-side rotating member 935 is supported so as to be rotatable about its center axis (case-side force receiving axis) FC.

The case side force receiving axis FC is disposed in parallel with the block side force receiving axis MC. The case-side force receiving axis FC is a straight line parallel to the bore central axis direction in a plane orthogonal to the case-side force receiving axis FC and intersects with a straight line passing through the intersection of the same plane and the block-side force receiving axis MC. Has been placed.
The case side rotating member 935 is driven to rotate by a driving device (not shown).

  The link shaft portion 936 has a central axis (link axis) LC that rotates around the case-side force receiving axis FC as the case-side rotating member 935 rotates. The link axis LC is disposed in parallel with the block side force receiving axis MC.

  The link mechanism 933 is configured to be able to rotate and move about the block side force receiving axis MC as the center of rotation while the link axis LC rotates about the case side force receiving axis FC as the center of rotation.

Hereinafter, the operation of the compression ratio changing device 930 will be described.
As shown in FIG. 1A, when the link axis LC is at a position directly above the case-side force receiving axis FC, that is, the link axis LC is located at the uppermost position with respect to the case-side force receiving axis FC. The case-side force receiving axis FC, the link axis LC, and the block-side force receiving axis MC are aligned in this order, and the vertical direction between the case-side force receiving axis FC and the block-side force receiving axis MC. The distance Y at is the longest. Accordingly, the distance in the vertical direction between the crankcase 920 and the cylinder block 910 is also the longest, and the compression ratio is the lowest (lowest ratio).

  In this state, the compression ratio changing device 930 moves the right case-side rotating member 935 in FIG. 1A clockwise (in the direction of the arrow A) and the left case side to increase the compression ratio. The rotating member 935 is driven to rotate counterclockwise (in the direction of arrow B).

  As a result, the right link axis LC rotates in the clockwise direction around the case side force receiving axis FC, and the left link axis LC rotates in the counterclockwise direction around the case side force receiving axis FC. At this time, the block-side rotating member 934 cannot move in the left-right direction due to the rigidity of the cylinder block 910.

  Therefore, the block-side rotating member 934 on the right side rotates counterclockwise in the bearing hole while abutting against the wall surface forming the bearing hole of the block-side force receiving portion 931 to push down the block-side force receiving portion 931. Similarly, the left block-side rotating member 934 also rotates clockwise in the bearing hole of the block-side force receiving portion 931 to push down the block-side force receiving portion 931. Then, by continuing the rotation drive of the case side rotation member 935, the state of the compression ratio changing device 930 is such that the link axis LC is more than the case side force receiving axis FC as shown in FIG. The crankcase 920 is aligned with the case-side force receiving axis FC in the left-right direction at a position outside the crankcase 920.

  In the state shown in FIG. 1B, the distance Y in the vertical direction between the case-side force receiving axis FC and the block-side force receiving axis MC is shorter than that shown in FIG. Therefore, the compression ratio of the internal combustion engine is higher than that shown in FIG.

  Further, by continuing the rotation drive of the case side rotating member 935, the right link axis LC rotates in the clockwise direction around the case side force receiving axis FC, and the left link axis LC moves to the case side force receiving axis FC. Rotate around counterclockwise. As a result, the block-side rotating member 934 on the right side rotates clockwise in the bearing hole of the block-side force receiving portion 931 to push down the block-side force receiving portion 931. Similarly, the left block-side rotating member 934 also rotates counterclockwise in the bearing hole of the block-side force receiving portion 931 and pushes down the block-side force receiving portion 931. Then, the state of the compression ratio changing device 930 reaches the state shown in FIG.

  In the state shown in FIG. 1C, the link axis LC, the case side force receiving axis FC, and the block side force receiving axis MC are arranged on the same straight line in this order, and the case side force receiving axis FC and the block side force receiving force are aligned. The distance Y between the axis MC and the vertical direction is the shortest (that is, shorter than the state shown in FIG. 1A and the state shown in FIG. 1B). Accordingly, since the distance in the vertical direction between the crankcase 920 and the cylinder block 910 is also shortest, the compression ratio of the internal combustion engine is the highest ratio (highest ratio).

  Thus, as the right case-side rotating member 935 rotates clockwise and the left case-side rotating member 935 rotates counterclockwise (the state of the compression ratio changing device 930 is shown in FIG. 1A). The compression ratio of the internal combustion engine increases as it goes from the closed state to the state shown in (C).

  On the other hand, when reducing the compression ratio of the internal combustion engine, the compression ratio changing device 930 drives the case-side rotating member 935 to rotate in the direction opposite to that described above. Thereby, each member operates in the opposite direction to the case described above.

As described above, the conventional compression ratio changing device 930 changes the compression ratio of the internal combustion engine by rotationally driving the case side rotating member 935 so that the link axis LC rotates around the case side force receiving axis FC. (For example, refer to Patent Document 1).
JP 2003-206871 A

  By the way, when the mixed gas burns in the combustion chamber, an extremely high pressure (combustion pressure) is generated in the combustion chamber. With this combustion pressure, a cylinder head (not shown) fixed to the upper part of the cylinder block 910 is pushed upward. That is, the cylinder block 910 is pushed upward. On the other hand, the crankcase 920 is fixed to the vehicle body.

  Therefore, in the state where the compression ratio of the internal combustion engine is a compression ratio between the highest ratio and the lowest ratio (for example, the state shown in FIG. 1B), the right side case side rotating member 935 has a case side rotation. Torque is applied to rotate the member 935 counterclockwise. Further, a torque is applied to the case-side rotating member 935 on the left side so as to drive the case-side rotating member 935 in the clockwise direction.

  The relationship between the torque Tq generated by this combustion pressure and the rotation angle θ that the link axis LC rotates around the case-side force receiving axis FC is obtained as follows.

  Now, it is orthogonal to the link axis LC of the right block side force receiving axis MC, right link axis LC and right case side force receiving axis FC shown in FIGS. As schematically shown in FIG. 2 showing the positional relationship in the plane, an upward force F0 is applied to the block-side force receiving axis MC by the pressure (combustion pressure) generated by the combustion of the mixed gas in the combustion chamber. Assuming that Further, the block-side force receiving axis MC and the link axis LC are connected by a virtual member that does not generate shear stress, and the case-side force receiving axis FC and the link axis LC are connected by the same member. Assume that

In this state, the force applied to the link axis LC is the force F0, the component force F1a in the direction along the line segment L1 connecting the block side force receiving axis MC and the link axis LC, and the block side force receiving axis MC and A component force F1a in a direction along the line segment L1 when disassembled into a component force F1b in a direction perpendicular to the line segment L2 connecting the case-side force receiving axis FC. Accordingly, the force F1a is obtained by the following equation (1).
F1a ＝ F0 ・ 1 / cosψ (1)

  Here, ψ is a rotation angle with the block side force receiving axis MC as the center of rotation, and represents a rotation angle in the clockwise direction from the line segment L1 to the line segment L2. Further, the rotation angle θ (ie, the rotation angle of the case side rotating member 935) θ that the link axis LC rotates about the case side force receiving axis FC is a rotation angle with the case side force receiving axis FC as the center of rotation. The rotation angle in the clockwise direction from the line segment L2 to the line segment L3 connecting the case-side force receiving axis FC and the link axis line LC.

Therefore, the relationship between the rotation angle θ and the rotation angle ψ is that the distance (the length of the line segment L3) between the case side force receiving axis FC and the link axis LC is set to D1, and the block side force receiving axis MC and the link are linked. If the distance from the axis LC (the length of the line segment L1) is set as D2, it is expressed as the following equation (2).
ψ = sin ⁻¹ (D1 / D2 / sinθ) (2)

The torque Tq applied to the case-side force receiving axis FC in the direction to rotate the case-side force receiving axis FC in the counterclockwise direction is obtained by applying the force F1a applied to the link axis LC along the line segment L3. Between the component force Ft in the direction orthogonal to the line segment L3 and the case-side force receiving axis FC and the link axis LC when the component force Fp in the selected direction is broken down into the component force Ft in the direction orthogonal to the line segment L3. And the distance D1. Therefore, the torque Tq is obtained by the following equation (3).
Tq ＝ D1 ・ Ft ＝ D1 ・ F1a ・ cosγ (3)

Here, γ is a rotation angle with the link axis LC as the center of rotation, and represents a rotation angle in the clockwise direction from the line segment L1 to the line segment L4. The line segment L4 is a line segment obtained by rotating the line segment L3 by 90 ° clockwise with the link axis LC as the center of rotation. The rotation angle γ has the relationship shown in the following equation (4) with the rotation angle θ and the rotation angle ψ. Therefore, by substituting the following equation (4) into the above equation (3), the torque Tq is expressed as the following equation (5).
γ = θ + ψ−π / 2 (4)
Tq ＝ D1 ・ F0 ・ sin (θ ＋ ψ) / cosψ (5)

  Therefore, the relationship between the torque Tq and the rotation angle θ can be obtained from the above equation (2) and the above equation (5). For example, the relationship between the torque Tq and the rotation angle θ when the distance D1 is 3 mm and the distance D2 is 5 mm is obtained as shown by a curve C1 in FIG.

  In this case, the torque Tq is a positive value in the angle range A where the rotation angle θ is 0 ° to 180 °. That is, when the rotation angle θ is in the angle range A, the torque Tq is a torque for rotating the case-side force receiving axis FC in a direction in which the rotation angle θ decreases.

  By the way, when the rotation angle θ is 0 ° or 360 ° (see FIG. 1A), the distance Y between the case-side force receiving axis FC and the block-side force receiving axis MC is the longest. The compression ratio of the internal combustion engine is the lowest ratio. On the other hand, when the rotation angle θ is 180 ° (see FIG. 1C), the distance Y between the case-side force receiving axis FC and the block-side force receiving axis MC becomes the shortest. The compression ratio is the highest.

  Accordingly, when the rotation angle θ is in the angle range A, the rotation angle θ increases from 0 ° to 180 °, that is, the case-side rotation member 935 on the right side in FIG. 1 is driven to rotate clockwise. As a result, the compression ratio of the internal combustion engine is increased. Therefore, it can be said that the torque Tq is a torque in a direction to reduce the compression ratio of the internal combustion engine.

  On the other hand, the torque Tq takes a negative value in the angle range B where the rotation angle θ is 180 ° to 360 °. That is, when the rotation angle θ is in the angle range B, the torque Tq is a torque that attempts to rotate the case-side force receiving axis FC in the direction in which the rotation angle θ increases.

  As described above, when the rotation angle θ is in the angle range B, the rotation angle θ decreases from 360 ° to 180 °, that is, the case-side rotation member 935 on the right side in FIG. By being driven to rotate, the compression ratio of the internal combustion engine is increased. Therefore, it can be said that the torque Tq is a torque in a direction to reduce the compression ratio of the internal combustion engine.

  The magnitude | Tq | of the torque Tq has a maximum value | Tq0 | when the rotation angle θ is approximately 65 ° when the rotation angle θ is in the angle range A. On the other hand, when the rotation angle θ is in the angle range B, the magnitude | Tq | of the torque Tq becomes the maximum value | Tq0 | when the rotation angle θ is approximately 295 °.

  Therefore, in the conventional compression ratio changing device, a relatively large torque (that is, a torque larger than the maximum value | Tq0 | of the magnitude of the torque generated by the combustion pressure) is not applied to the case-side rotating member 935. Since the link axis LC cannot be rotationally moved within a relatively large angle range, there is a problem that the link mechanism becomes large and / or a torque necessary to drive the link mechanism becomes excessive. It was.

  The present invention has been made to address the above-described problems, and an object of the present invention is to provide a compression ratio changing device for an internal combustion engine that can reduce torque for driving a link mechanism.

In order to achieve this object, an internal combustion engine compression ratio changing device according to the present invention is a piston reciprocating internal combustion engine, and a crankcase that rotatably supports a crankshaft and a cylinder block that reciprocally accommodates a piston. Are applied to an internal combustion engine configured to be able to move relative to each other in the direction of the central axis of the cylinder bore.
That is, the compression ratio changing device for an internal combustion engine according to the present invention is:
A cylinder bore, which is a cylindrical hole penetrating in a predetermined bore central axis direction, is formed, and is fixed to the cylinder block so as to cover one of the cylinder block housing the piston in the cylinder bore and the opening portion of the cylinder bore. The cylinder head is disposed on the opposite side of the cylinder head with respect to the cylinder block, and is movable relative to the cylinder block in the bore central axis direction, and the crankshaft connected to the piston is rotatable. The present invention is applied to an internal combustion engine that includes a crankcase that is supported by the internal combustion engine.

An internal combustion engine compression ratio changing device according to the present invention includes:
A block side force receiving portion provided in the cylinder block;
A case-side force receiving portion provided in the crankcase;
A link mechanism that connects the block-side force receiving portion and the case-side force receiving portion, wherein a predetermined link axis in the link mechanism is parallel to the link axis, and the case-side force in the case-side force receiving portion A link mechanism configured to be able to rotate about the block side force receiving axis in the block side force receiving portion parallel to the link axis while rotating about the axis as the center of rotation;
Link mechanism driving means for driving the link mechanism so as to rotate and move the link axis within a predetermined set angle range with the case side force receiving axis as the center of rotation,
When the link mechanism is driven by the link mechanism driving unit, the compression ratio is changed by changing the distance in the bore central axis direction between the crankcase and the cylinder block.

  Further, the block side force receiving portion, the case side force receiving portion, and the link mechanism are straight lines parallel to the bore central axis direction in a plane orthogonal to the link axis, and the same plane and the block side force receiving force. A first straight line that is a straight line passing through the intersection with the axis, and a second straight line that is parallel to the bore central axis direction in the same plane and that passes through the intersection between the same plane and the case-side force receiving axis. Are separated by a predetermined distance.

  In addition, the link mechanism driving means is provided in the same case from the state where the distance in the bore central axis direction between the block side force receiving axis and the case side force receiving axis is longest to the state where the distance is shortest. When the link axis is rotated and moved in one direction with the side force receiving axis as the center of rotation, the angle range that the rotation angle of the link axis around the case force receiving axis takes is the same from the state where the distance is the longest. The angle range that the rotation angle takes when rotating the link axis in the direction opposite to the one direction with the case side force receiving axis as the center of rotation until the distance becomes the shortest. Among them, the pressure is generated by the pressure generated by the combustion of the mixed gas in the combustion chamber formed by the bore wall surface forming the cylinder bore, the lower surface of the cylinder head, and the top surface of the piston. A predetermined angle within an angle range in which the maximum value of the magnitude of the torque applied to the link mechanism is smaller so that the link axis is rotationally moved about the case side force receiving axis as the center of rotation. A range is adopted as the set angle range.

According to this, the first straight line and the second straight line are separated by a predetermined distance. Therefore, as in FIG. 2, the positional relationship among the block-side force receiving axis MC, the link axis LC, and the case-side force receiving axis FC in a plane orthogonal to the link axis LC can be understood from FIG. The relationship between the rotation angle θ and the rotation angle ψ is expressed by the following equation (6).
ψ = sin ⁻¹ (D1 / D2 / sinθ + e / D2) (6)

  Here, ψ is a rotation angle with the block side force receiving axis MC as the center of rotation, and is parallel to the bore center axis direction from the line segment L1 connecting the block side force receiving axis MC and the link axis LC, and the block The rotation angle in the clockwise direction to the straight line (first straight line) L2a passing through the side force receiving axis MC is represented. The rotation angle θ of the link axis LC is a rotation angle with the case side force receiving axis FC as the center of rotation, and is a straight line (second line) parallel to the bore center axis direction and passing through the case side force receiving axis FC. Straight line) This represents a clockwise rotation angle from L2b to a line segment L3 connecting the case-side force receiving axis FC and the link axis LC.

  Furthermore, e represents the distance between the first straight line L2a and the second straight line L2b. The distance e has a positive value when the first straight line L2a is located on the inner side of the cylinder block with respect to the second straight line L2b, and the first straight line L2a is more outward of the cylinder block than the second straight line L2b. It has a negative value when located on the side.

  Therefore, as in the case where the first straight line and the second straight line coincide with each other (when e = 0), the case-side force is received by the combustion pressure by the above formula (2) and the above formula (6). The relationship between the torque Tq applied to the link mechanism and the rotation angle θ so as to rotate the link axis LC around the axis FC can be obtained. For example, the relationship between the torque Tq and the rotation angle θ when the distance D1 is 3 mm, the distance D2 is 5 mm, and the distance e is 1 mm is obtained as shown by a curve C2 in FIG.

  In this case, the torque Tq becomes a positive value in an angle range C in which the rotation angle θ is approximately −7 ° to approximately 150 °. That is, when the rotation angle θ is in the angle range C, the torque Tq is a torque that attempts to rotate the case-side force receiving axis FC in a direction in which the rotation angle θ decreases.

  By the way, when the rotation angle θ is approximately −7 ° or approximately 353 °, the case-side force receiving axis FC, the link axis LC, and the block-side force receiving axis MC are arranged on the same straight line in this order. The distance between the FC and the block-side force receiving axis MC in the bore central axis direction is the longest. Therefore, the compression ratio of the internal combustion engine is the lowest ratio. On the other hand, when the rotation angle θ is approximately 150 °, the link axis LC, the case side force receiving axis FC, and the block side force receiving axis MC are arranged on the same straight line in this order. The distance in the bore central axis direction from the force axis MC is the shortest. Therefore, the compression ratio of the internal combustion engine is the highest ratio.

  Therefore, when the rotation angle θ is in the angle range C, the compression angle of the internal combustion engine is increased by increasing the rotation angle θ from approximately −7 ° to approximately 150 °. Therefore, it can be said that the torque Tq is a torque in a direction to reduce the compression ratio of the internal combustion engine.

  On the other hand, the torque Tq takes a negative value in the angle range D in which the rotation angle θ is approximately 150 ° to approximately 353 °. That is, when the rotation angle θ is in the angle range D, the torque Tq is a torque that attempts to rotate the case-side force receiving axis FC in a direction in which the rotation angle θ increases.

  As described above, when the rotation angle θ is in the angle range D, the compression angle of the internal combustion engine is increased by decreasing the rotation angle θ from approximately 353 ° to approximately 150 °. Therefore, it can be said that the torque Tq is a torque in a direction to reduce the compression ratio of the internal combustion engine.

  The magnitude | Tq | of the torque Tq becomes the maximum value | Tq1 | when the rotation angle θ is approximately 61 ° when the rotation angle θ is in the angle range C. This maximum value | Tq1 | is larger than the maximum value | Tq0 | of the magnitude | Tq | of the torque Tq when the first straight line and the second straight line coincide with each other (when e = 0). On the other hand, the magnitude | Tq | of the torque Tq becomes the maximum value | Tq2 | when the rotation angle θ is approximately 288 ° when the rotation angle θ is in the angle range D. This maximum value | Tq2 | is smaller than the maximum value | Tq0 | of the magnitude | Tq | of the torque Tq when the first straight line and the second straight line are coincident (when e = 0).

  Therefore, as in the above configuration, the first straight line L2a and the second straight line L2b are separated by a predetermined distance e, and the torque generated by the combustion pressure is the link axis LC with the case side force receiving axis FC as the center of rotation. The link mechanism is driven so that the link axis LC rotates in a predetermined angle range within the angle range D in which the maximum value of the magnitude | Tq | of the torque Tq applied to the link mechanism to be rotated is smaller. Thus, even if the angle range includes the rotation angle at which the magnitude | Tq | of the torque Tq becomes the maximum value, the maximum value of the magnitude | Tq | of the torque Tq can be made smaller than | Tq0 |. it can. Therefore, the link axis LC can be rotated and moved within a relatively large angle range without increasing the torque for driving the link mechanism in order to increase the compression ratio of the internal combustion engine. As a result, the link mechanism can be miniaturized and / or the torque required to drive the link mechanism can be reduced.

In this case, the block side force receiving portion is provided so as to extend outward from the outer wall surface of the cylinder block.
The block-side force receiving portion, the case-side force receiving portion, and the link mechanism are preferably configured such that the first straight line is located on the inner side of the cylinder block with respect to the second straight line. .

  As described above, a force for separating the cylinder block and the crankcase is generated by the combustion pressure. By this force, a force directed toward the opposite side of the crankcase (to the cylinder head) is applied to the cylinder block via the cylinder head. On the other hand, a force directed toward the crankcase is applied to the block side force receiving portion via the link mechanism.

  Accordingly, when the block-side force receiving portion is provided so as to extend from the outer wall surface of the cylinder block to the outside of the cylinder block, the cylinder block is moved toward the crankcase at both ends of the cylinder block due to the combustion pressure. A direction force is applied, and a force toward the opposite side of the crankcase is applied at a portion other than both ends of the cylinder block.

  That is, a force (bending stress) for bending the cylinder block is applied to the cylinder block. Therefore, as in the above configuration, the first straight line is positioned on the outer side of the cylinder block than the second straight line by positioning the first straight line on the inner side of the cylinder block. In comparison, the amount of deformation of the cylinder block due to the bending stress can be reduced.

In this case, the outer wall surface of the cylinder block is formed with a notch that opens toward the outside of the cylinder block.
The link mechanism is configured to rotate and move the link axis around the case-side force receiving axis by being rotationally driven, and is disposed coaxially with the case-side force receiving axis and a part of the notch A worm wheel arranged to be housed in the section,
The link mechanism driving means is preferably configured to rotationally drive the worm wheel of the link mechanism.

  According to this, when the structure in which the link mechanism is driven using the worm wheel is adopted, the outer side of the cylinder block is compared with the case where the first straight line is positioned on the outer side of the cylinder block with respect to the second straight line. The depth of the notch formed in the wall surface can be reduced. As a result, the rigidity of the cylinder block can be increased.

<Configuration>
Embodiments of an internal combustion engine to which a compression ratio changing device for an internal combustion engine according to the present invention is applied will be described below with reference to the drawings. As shown in FIG. 6, the internal combustion engine 10 includes a cylinder block 20 and a crankcase 30.

<< Cylinder block >>
As shown in FIGS. 6 to 8, the cylinder block 20 has a substantially rectangular upper surface 20a and a lower surface 20b having short sides and long sides, and two side surfaces perpendicular to the short side direction (in this specification, “ It is also referred to as an “outer wall surface” or “side wall surface.”) 20 c. Hereinafter, in this specification, a direction from the upper surface 20a of the cylinder block 20 toward the lower surface 20b is referred to as a downward direction, and a direction from the lower surface 20b of the cylinder block 20 to the upper surface 20a is referred to as an upward direction.

  The cylinder block 20 is formed with four cylindrical through holes penetrating in a direction orthogonal to the upper surface 20a and the lower surface 20b (that is, the vertical direction, also referred to as the bore central axis direction). These through holes are linearly arranged in the long side direction (cylinder arrangement direction) of the cylinder block 20. This through hole is referred to as a cylinder bore 21.

  On both side wall surfaces 20c of the cylinder block 20, a notch 20c1 is formed one by one that is open toward the outside of the cylinder block 20 at a central portion in the cylinder arrangement direction and including a lower end of the cylinder block 20. ing.

  As shown in FIG. 9, which is a cross-sectional view of the internal combustion engine 10 taken along a plane including 9-9 line passing through the central axis (bore central axis) BC of the cylinder bore 21 shown in FIG. 6 and orthogonal to the cylinder arrangement direction. In addition, one cylindrical piston 22 is accommodated in each cylinder bore 21.

<< Crankcase >>
The crankcase 30 is fixed to the vehicle body. As shown in FIG. 6, the crankcase 30 rotatably supports the crankshaft 31 and accommodates the crankshaft 31. The crankcase 30 is disposed below the cylinder block 20 so that the axial direction of the crankshaft 31 coincides with the cylinder arrangement direction. Each piston 22 is connected to the crankshaft 31 via a connecting rod 32 shown in FIG. With such a configuration, the reciprocating motion of each piston 22 is converted into the rotational motion of the crankshaft 31.

<< Cylinder head >>
Further, the internal combustion engine 10 includes a 10-10 line passing between two cylinder bores 21 and 21 adjacent to each other shown in FIGS. 9 and 6 and cuts the internal combustion engine 10 along a plane orthogonal to the cylinder arrangement direction. As shown in FIG. 10 which is a sectional view, a cylinder head 40 is provided. The cylinder head 40 is fixed to the upper surface 20 a of the cylinder block 20 (that is, the side opposite to the crankcase 30 with respect to the cylinder block 20) so as not to move with respect to the cylinder block 20. That is, the cylinder head 40 is fixed to the cylinder block 20 so as to cover one (upper side) of the opening portion of the cylinder bore 21.

  As shown in FIG. 9, the cylinder head 40 includes a plurality of recesses 40 a 1 that open to the cylinder block 20 side surface (the lower surface of the cylinder head 40) 40 a of the cylinder head 40 and correspond to each of the cylinder bores 21. Is formed. Each recess 40a1 is connected to a wall surface (bore wall surface) forming one cylinder bore 21 corresponding to each recess 40a1 in a state where the cylinder head 40 is fixed to the cylinder block 20. The recess 40a1 of the lower surface 40a of the cylinder head 40, the bore wall surface, and the surface of the piston 22 on the cylinder head 40 side (the top surface of the piston 22) form a combustion chamber 41 for each cylinder bore 21 (for each cylinder). .

  As shown in FIG. 9, an intake port 42 that communicates with the combustion chamber 41 and an exhaust port 43 that communicates with the combustion chamber 41 are formed in the cylinder head 40 for each cylinder. In the cylinder head 40, an intake valve 42 a that opens and closes the intake port 42, an exhaust valve 43 a that opens and closes the exhaust port 43, and a spark plug 44 that generates a spark in the combustion chamber 41 are disposed for each cylinder. Yes.

  In addition, the internal combustion engine 10 includes fuel injection means (not shown). By injecting fuel by the fuel injection means, a mixed gas containing fuel and air is introduced into the combustion chamber 41 via the intake port 42. It comes to supply.

<< Compression ratio changing device >>
Furthermore, the internal combustion engine 10 includes a compression ratio changing device 50 as shown in FIGS.
As shown in FIG. 6, the compression ratio changing device 50 includes a case-side force receiving portion 51, a block-side force receiving portion 52, and a link mechanism 53 provided in the vicinity of each side wall surface 20 c of the cylinder block 20. And a link mechanism driving unit 54 as a link mechanism driving means.

  Case side force receiving portion 51, block side force receiving portion 52 and link mechanism 53 on one side wall surface 20c, Case side force receiving portion 51, block side force receiving portion 52 and link mechanism 53 on the other side wall surface 20c, Is symmetric with respect to the bore center axis arrangement plane including the bore center axis BC of all cylinders. Therefore, regarding the case side force receiving portion 51, the block side force receiving portion 52, and the link mechanism 53, only the case side force receiving portion 51, the block side force receiving portion 52, and the link mechanism 53 provided on one side wall surface 20c. explain.

<Case side force receiving part>
The case side force receiving portion 51 is provided in the crankcase 30. The case-side force receiving portion 51 includes a flat plate-like vertical wall portion 51a and a plurality of cap portions 51b.
The vertical wall portion 51 a constitutes the upper side wall of the crankcase 30. The vertical wall 51a faces the side wall surface 20c of the cylinder block 20 and covers a part of the side wall surface 20c in a state where the cylinder block 20 is disposed on the crankcase 30.

  A plurality of (four in this example) corresponding to each of the cylinder bores 21 in a state where the vertical wall portion 51a penetrates in the thickness direction and the cylinder block 20 is disposed on the crankcase 30. Through-hole 51a1 is formed. The vertical wall 51a is cut at a position between two adjacent through-holes 51a1 and 51a1 formed in the vertical wall 51a by a flat surface that is open outward and orthogonal to the cylinder arrangement direction. A recessed portion 51a2 having a semicircular shape is formed in the cross section. The center of the semicircle of each recessed part 51a2 is arrange | positioned coaxially. Furthermore, a through hole 51a3 that penetrates in the thickness direction at the center in the cylinder arrangement direction is formed in the vertical wall 51a.

  One cap 51b corresponds to each of the recesses 51a2 of the vertical wall 51a. Each cap 51b is fixed to the vertical wall 51a so as to cover one corresponding recess 51a2 of the vertical wall 51a. In each cap portion 51b, in a state where the cap portion 51b is fixed to the vertical wall portion 51a, the cap portion 51b is cut by a plane that is a recess that opens toward the vertical wall portion 51a and that is orthogonal to the cylinder arrangement direction. A recess 51b1 having a semicircular shape in the cross section is formed. The semicircular diameter of the recess 51b1 is the same as the semicircular diameter of the recess 51a2.

  With this configuration, the case-side force receiving portion 51 is arranged in the cylinder arrangement direction by the concave portion 51a2 of the vertical wall portion 51a and the concave portion 51b1 of the cap portion 51b in a state where the cap portion 51b is fixed to the vertical wall portion 51a. A plurality of cylindrical bearing holes 51c that penetrates and are arranged coaxially are formed (see FIG. 10). The center axis FC of the bearing hole 51c is also referred to as a case side force receiving axis FC in the present specification.

<Block side force receiving part>
The block-side force receiving portion 52 includes a plurality of members (four in this example) corresponding to each of the through holes 51a1 of the vertical wall portion 51a. Each member of the block side force receiving portion 52 is fixed to the lower end portion of the side wall surface 20c of the cylinder block 20 in a state of being inserted into the through hole 51a1 of the vertical wall portion 51a corresponding to the member. That is, the block-side force receiving portion 52 is provided in the cylinder block 20 so as to extend from the side wall surface 20 c of the cylinder block 20 to the outside of the cylinder block 20.

  The vertical length of the block side force receiving portion 52 is shorter than the vertical length of the through hole 51a1 of the vertical wall portion 51a. With such a configuration, the block-side force receiving portion 52 is movable in the vertical direction within the through hole 51a1 of the vertical wall portion 51a. That is, the cylinder block 20 is movable relative to the crankcase 30 in the vertical direction (bore central axis direction).

  Each member of the block-side force receiving portion 52 is formed with a cylindrical bearing hole 52a penetrating in the cylinder arrangement direction. The diameter of each bearing hole 52a is larger than the diameter of the bearing hole 51c. Each bearing hole 52a is arranged coaxially. The center axis MC of the bearing hole 52a is also referred to as a block side force receiving axis MC in the present specification.

  As shown in FIGS. 9 and 10, the block-side force receiving axis MC is a straight line parallel to the bore central axis direction in a plane orthogonal to the block-side force receiving axis MC, and the same plane and the block-side force receiving axis A first straight line LL1 that is a straight line passing through the intersection with MC is a straight line that is parallel to the bore central axis direction in the same plane and that passes through the intersection between the same plane and the case-side force receiving axis FC. It is arranged so as to be located on the inner side of the cylinder block 20 by a distance e from LL2. That is, the first straight line LL1 and the second straight line LL2 are separated by a distance e (1 mm in this example).

<Link mechanism>
As shown in FIGS. 6, 9, and 10, the link mechanism 53 includes a plurality of fixed cam portions each corresponding to a rod-shaped eccentric shaft portion 53 a and a bearing hole 51 c of the case side force receiving portion 51. 53b, a plurality of movable cam portions 53c corresponding to each of the bearing holes 52a of the block side force receiving portion 52, and a worm wheel 53d. The central axis LC of the eccentric shaft portion 53a is also referred to as a link axis LC in this specification.

  Each fixed cam portion 53b is a columnar member having substantially the same diameter as the bearing hole 51c of the case side force receiving portion 51. The length in the axial direction of each fixed cam portion 53 b is substantially the same as the length in the axial direction of one corresponding bearing hole 51 c of the case side force receiving portion 51. As shown in FIG. 11A, which is a front view of the fixed cam portion 53b, each fixed cam portion 53b has a through-hole penetrating in the axial direction at a position deviated (eccentric) from the center axis FC. In addition, a cylindrical through hole HF having substantially the same diameter as the eccentric shaft portion 53a is formed.

  Each movable cam portion 53c is a cylindrical member having substantially the same diameter as the bearing hole 52a of the block side force receiving portion 52. The length in the axial direction of each movable cam portion 53 c is substantially the same as the length in the axial direction of one corresponding bearing hole 52 a of the block side force receiving portion 52. As shown in FIG. 11B, which is a front view of the movable cam portion 53c, each movable cam portion 53c has a through-hole penetrating in the axial direction at a position that is deviated (eccentric) from its central axis MC. In addition, a cylindrical through hole HM having substantially the same diameter as the eccentric shaft portion 53a is formed.

  In this example, the through hole HF of the fixed cam portion 53b is disposed such that the distance D1 between the central axis FC of the fixed cam portion 53b and the central axis LC of the through hole HF is 3 mm. Furthermore, the through hole HM of the movable cam portion 53c is arranged such that the distance D2 between the central axis MC of the movable cam portion 53c and the central axis LC of the through hole HM is 5 mm. That is, the ratio of the distance D2 to the distance D1 is set to 5/3. The ratio of the distance e to the distance D1 is set to 1/3.

  The fixed cam portion 53b and the movable cam portion 53c are alternately arranged with the fixed cam portions 53b and the movable cam portions 53c one by one, and the through holes HF of the fixed cam portions 53b and the through holes HM of the movable cam portions 53c are coaxial. And is attached to the eccentric shaft portion 53a in a state where the eccentric shaft portion 53a is passed through the through holes HF and HM. Screw holes (not shown) are formed in the fixed cam portion 53b and the eccentric shaft portion 53a. The fixed cam portion 53b and the eccentric shaft portion 53a are arranged so that the respective fixed cam portions 53b do not rotate with respect to the eccentric shaft portion 53a, and all the fixed cam portions 53b are arranged coaxially. It is fixed by a screw (not shown) that is inserted through. On the other hand, the movable cam portion 53c is rotatable with respect to the eccentric shaft portion 53a.

  In the link mechanism 53, each fixed cam portion 53b is accommodated in one corresponding bearing hole 51c of the case side force receiving portion 51 and rotates in the bearing hole 51c while abutting against a wall surface forming the bearing hole 51c. Each movable cam portion 53c is accommodated in one corresponding bearing hole 52a of the block-side force receiving portion 52 and is in contact with the wall surface forming the bearing hole 52a so as to be possible. Is supported by the case-side force receiving portion 51 and the block-side force receiving portion 52 so as to be rotatable.

  With such a configuration, the link mechanism 53 connects the case-side force receiving portion 51 and the block-side force receiving portion 52 to each other. Further, the link axis LC of the link mechanism 53 rotates around the block side force receiving axis MC parallel to the link axis LC while rotating about the case side force receiving axis FC parallel to the link axis LC. It is possible to move.

  The worm wheel 53d is a bevel gear. The worm wheel 53d is fixed to the fixed cam portion 53b so as to be coaxial with the fixed cam portion 53b and not to rotate with respect to the fixed cam portion 53b. The worm wheel 53d is disposed so as to be inserted into the through hole 51a3 and a part thereof is accommodated in the notch 20c1. With such a configuration, the worm wheel 53d is rotationally driven to rotate the link axis LC around the case-side force receiving axis FC.

  The link mechanism drive unit 54 includes an electric motor 54a, a drive shaft 54b, and two worms 54c corresponding to each of the two worm wheels 53d. The drive shaft 54b is rotatably supported by the crankcase 30. The axis of the drive shaft 54b extends along a direction orthogonal to the cylinder arrangement direction. The drive shaft 54b is disposed so as to pass directly below the worm wheel 53d. The drive shaft 54b is rotationally driven in one direction and the opposite direction to the one direction by the electric motor 54a.

  Each worm 54c is fixed to the drive shaft 54b at a position directly below one worm wheel 53d corresponding to each worm 54c. Each worm 54c is a screw gear that meshes (engages) with one worm wheel 53d corresponding to each worm 54c. The two worms 54c rotate integrally with the drive shaft 54b, thereby rotating the two worm wheels 53d in different directions. Each worm 54c changes the rotation direction of one worm wheel 53d corresponding to each worm 54c by changing the rotation direction.

  With such a configuration, the link mechanism driving unit 54 drives the link mechanism 53 so as to rotate and move the link axis LC in a predetermined set angle range with the case side force receiving axis FC as the center of rotation.

<Operation of compression ratio change device>
Next, the operation of the compression ratio changing device 50 configured as described above will be described.
In the compression ratio changing device 50, the link axis LC is within an angle range D (see FIGS. 4 and 5) in which the rotation angle θ of the link axis LC is an angle between about 150 ° and about 353 °. By driving the link mechanism 53 so as to rotate around the case-side force receiving axis FC, the distance in the vertical direction between the crankcase 30 and the cylinder block 20 is changed to change the compression ratio of the internal combustion engine 10. . That is, the link mechanism driving unit 54 employs the angle range D as the set angle range.

First, the case where the compression ratio changing device 50 changes the compression ratio of the internal combustion engine 10 from the lowest ratio (lowest ratio) to the highest ratio (highest ratio) will be described.
In the state where the compression ratio of the internal combustion engine 10 is the lowest ratio, as shown in FIG. 12, the case side force receiving axis FC, the link axis LC, and the block side force receiving axis MC are arranged on the same straight line in this order. The distance Y in the vertical direction between the side force receiving axis FC and the block side force receiving axis MC is the longest. Therefore, since the distance Z in the vertical direction between the crankcase 30 and the cylinder block 20 is also the longest, the compression ratio of the internal combustion engine 10 is the lowest ratio.

  In this state, the compression ratio changing device 50 moves the worm wheel 53d constituting the right link mechanism 53 in FIG. 12 in the counterclockwise direction (direction of arrow A) and the worm wheel 53d constituting the left link mechanism 53. Is driven in a clockwise direction (in the direction of arrow B). As a result, the right link axis LC rotates counterclockwise about the case side force receiving axis FC (around the case side force receiving axis FC), and the left link axis LC moves to the case side force receiving axis FC. Rotate clockwise around FC. At this time, all the movable cam portions 53c cannot move in the left-right direction due to the rigidity of the cylinder block 20.

  Therefore, the right movable cam portion 53c rotates clockwise in the bearing hole 52a while abutting against the wall surface forming the bearing hole 52a of the block-side force receiving portion 52, and pushes down the block-side force receiving portion 52. Furthermore, the left movable cam portion 53 c rotates counterclockwise in the bearing hole 52 a while pressing against the wall surface forming the bearing hole 52 a of the block-side force receiving portion 52, and pushes down the block-side force receiving portion 52. Then, by continuing the rotational drive of the worm wheel 53d, the compression ratio changing device 50 is in a state where the link axis LC is more inward of the crankcase 30 than the case side force receiving axis FC, as shown in FIG. It reaches a state where it is aligned with the case-side force receiving axis FC in the left-right direction at the position on the side.

  In the state shown in FIG. 13, the distance Y between the case-side force receiving axis FC and the block-side force receiving axis MC in the vertical direction is shorter than that shown in FIG. Accordingly, the distance Z between the crankcase 30 and the cylinder block 20 in the vertical direction is also shortened. That is, the compression ratio of the internal combustion engine 10 is higher than that shown in FIG.

  Further, by continuing the rotational drive of the worm wheel 53d, the right link axis LC rotates counterclockwise around the case side force receiving axis FC, and the left link axis LC moves around the case side force receiving axis FC. Rotate clockwise. As a result, the right movable cam portion 53c rotates counterclockwise in the bearing hole 52a while abutting against the wall surface forming the bearing hole 52a of the block-side force receiving portion 52, and pushes down the block-side force receiving portion 52. . Further, the left movable cam portion 53c rotates clockwise in the bearing hole 52a while abutting against the wall surface forming the bearing hole 52a of the block-side force receiving portion 52, and pushes down the block-side force receiving portion 52. The state of the compression ratio changing device 50 reaches the state shown in FIG.

  In the state shown in FIG. 14, the link axis LC, the case side force receiving axis FC, and the block side force receiving axis MC are arranged on the same straight line in this order, and the case side force receiving axis FC and the block side force receiving axis MC are The distance Y in the vertical direction is the shortest (that is, shorter than the state shown in FIG. 12 and the state shown in FIG. 13). Therefore, since the distance Z in the vertical direction between the crankcase 30 and the cylinder block 20 is also the shortest, the compression ratio of the internal combustion engine 10 is the highest ratio.

  FIG. 15A shows a plane perpendicular to the link axis LC of the case side force receiving axis FC, the block side force receiving axis MC, and the link axis LC of the link mechanism 53 on the right side of FIGS. It is a figure which represents the change of a position notionally. As can be understood from FIG. 15A, the compression ratio changing device 50 has a rotation angle around the case-side force receiving axis FC of the link axis LC on the right side of FIGS. Changes from the rotation angle θr2 (approximately 353 ° in this example) to the rotation angle θr1 (approximately 150 ° in this example) from the state in which is positioned directly above the case-side force receiving axis FC. Thus, the right worm wheel 53d is driven to rotate counterclockwise. In other words, the link axis LC on the right side has the case side force receiving axis FC as the center of rotation in the angle range D in which the rotation angle θr is an angle between the rotation angle θr1 and the rotation angle θr2 (case side force receiving axis line). It can be rotated counterclockwise (around FC).

  Similarly, FIG. 15B is orthogonal to the link axis LC of the case side force receiving axis FC, the block side force receiving axis MC and the link axis LC of the left side link mechanism 53 of FIGS. It is a figure showing notionally the change of the position in the plane to do. As can be understood from FIG. 15B, the compression ratio changing device 50 is the rotation angle around the case-side force receiving axis FC of the link axis LC on the left side of FIGS. Of the counterclockwise direction from a state in which is positioned directly above the case-side force receiving axis FC from the rotation angle θl2 (approximately 353 ° in this example) to the rotation angle θl1 (approximately 150 ° in this example). The left worm wheel 53d is driven to rotate clockwise so as to change. In other words, the link axis LC on the left side has the case-side force receiving axis FC as the center of rotation in the angle range D in which the rotation angle θl is an angle between the rotation angle θl1 and the rotation angle θl2 (case-side force receiving axis). It can be rotated clockwise (around FC).

  As a result, the distance Z between the crankcase 30 and the cylinder block 20 in the vertical direction (bore central axis direction) is shortened. As a result, the compression ratio of the internal combustion engine 10 changes from the lowest ratio to the highest ratio.

  Next, a case where the compression ratio changing device 50 changes the compression ratio of the internal combustion engine 10 from the highest ratio to the lowest ratio will be described.

  In this case, in the state shown in FIG. 14, the compression ratio changing device 50 rotates the worm wheel 53d constituting the right link mechanism 53 clockwise and the worm wheel 53d constituting the left link mechanism 53 counterclockwise. The electric motor 54a is driven so as to rotate in the direction. As a result, the right link axis LC rotates in the clockwise direction around the case side force receiving axis FC, and the left link axis LC rotates in the counterclockwise direction around the case side force receiving axis FC.

  Therefore, the right movable cam portion 53c rotates clockwise in the bearing hole 52a while abutting against the wall surface forming the bearing hole 52a of the block-side force receiving portion 52, and pushes up the block-side force receiving portion 52. Further, the left movable cam portion 53 c rotates in the bearing hole 52 a counterclockwise while abutting against the wall surface forming the bearing hole 52 a of the block-side force receiving portion 52 to push up the block-side force receiving portion 52.

  Therefore, by continuing the rotational drive of the worm wheel 53d, the state of the compression ratio changing device 50 reaches the state shown in FIG. 13, and further continues to the state shown in FIG.

  In this way, as shown in FIG. 15A, the compression ratio changing device 50 changes the rotation angle θr from the rotation angle θr1 (approximately 150 ° in this example) to the rotation angle θr2 (approximately in this example). Worm wheel 53d constituting the link mechanism 53 on the right side of FIGS. 12 to 14 is driven to rotate clockwise so that the angle changes to 353 °. In other words, the right link axis LC is rotated clockwise around the case-side force receiving axis FC as the center of rotation in an angle range D in which the rotation angle θr is an angle between the rotation angle θr1 and the rotation angle θr2. It is done.

  Further, as shown in FIG. 15B, the compression ratio changing device 50 is configured such that the rotation angle θl is changed from the rotation angle θl1 (approximately 150 ° in this example) to the rotation angle θl2 (approximately 353 ° in this example). ), The worm wheel 53d constituting the link mechanism 53 on the left side of FIGS. 12 to 14 is rotationally driven in the counterclockwise direction. In other words, the left link axis LC rotates counterclockwise around the case-side force receiving axis FC as the center of rotation in an angle range D in which the rotation angle θl is an angle between the rotation angles θl1 and θl2. Be made.

  As a result, the distance Z between the crankcase 30 and the cylinder block 20 in the vertical direction (bore central axis direction) is lengthened. As a result, the compression ratio of the internal combustion engine 10 changes from the highest ratio to the lowest ratio.

  In the internal combustion engine 10 according to the embodiment configured as described above, when the mixed gas formed in the combustion chamber 41 burns, the pressure (combustion pressure) of the gas in the combustion chamber 41 becomes extremely high. With this combustion pressure, as shown in FIG. 16, the lower surface 40a of the cylinder head 40 is pushed upward by a force Fx0. Thereby, an upward force Fx1 is applied to the cylinder block 20 to which the cylinder head 40 is fixed. On the other hand, the crankcase 30 is fixed to the vehicle body.

  Accordingly, an upward force F0 is applied to the movable cam portion 53c. With this force F0, it can be considered that the same force (same force as the force Ft in FIG. 4) as described with reference to FIGS. 4 and 5 is applied to the link mechanism 53. Therefore, when the compression ratio of the internal combustion engine 10 is a compression ratio between the highest ratio and the lowest ratio (for example, the state shown in FIG. 16), the fixed cam portion 53b of the right link mechanism 53 has an eccentric shaft portion. Torque Tq is applied to rotate the fixed cam portion 53b in the clockwise direction via 53a. Furthermore, torque Tq is applied to the fixed cam portion 53b of the left link mechanism 53 through the eccentric shaft portion 53a so as to drive the fixed cam portion 53b to rotate counterclockwise. This torque Tq changes according to the rotation angles θr (= θ) and θl (= θ) of the link axis LC according to the above equations (2) and (6) (see FIG. 5 above).

  In the present embodiment, as described above, the first straight line that is parallel to the bore central axis direction in the plane orthogonal to the link axis LC and that passes through the intersection of the same plane and the block-side force receiving axis MC. The straight line LL1 is separated from the second straight line LL2, which is a straight line parallel to the bore central axis direction in the same plane and passing through the intersection of the same plane and the case-side force receiving axis FC, by a distance e. .

  Further, in the present embodiment, the link mechanism is configured to rotate and move the link axis LC around the case-side force receiving axis FC in an angle range D in which the rotation angle θ is an angle between approximately 150 ° and approximately 353 °. 53 is driven (see FIG. 15).

  This angle range D indicates that the case-side force-receiving axis FC is changed from a state in which the distance in the bore central axis direction between the block-side force-receiving axis MC and the case-side force-receiving axis FC is longest to a state in which the distance is shortest. When rotating the link axis LC as the center of rotation, the magnitude of the torque Tq out of the two angular ranges C and D that can be taken by the rotation angle θ around the case-side force receiving axis FC of the link axis LC | Tq The angle range is such that the maximum value of | is smaller (see FIGS. 5 and 15).

  As a result, the maximum value of the magnitude | Tq | of the torque Tq generated by the combustion pressure is the maximum value | Tq0 | when the first straight line LL1 and the second straight line LL2 match (when e = 0). Can be made smaller. As a result, the link axis LC can be rotated and moved within a relatively large angle range without increasing the torque for driving the link mechanism 53 in order to increase the compression ratio of the internal combustion engine 10. As a result, the link mechanism 53 can be reduced in size and / or the torque required to drive the link mechanism 53 can be reduced.

  Further, in the internal combustion engine 10 according to the embodiment configured as described above, as described above, a force for separating the cylinder block 20 and the crankcase 30 is generated by the combustion pressure. Due to this force, a force Fx <b> 1 directed toward the opposite side (upward) of the crankcase 30 (to the cylinder head 40) is applied to the cylinder block 20 via the cylinder head 40. On the other hand, a force Fy directed toward the crankcase 30 is applied to the block side force receiving portion 52 via the link mechanism 53.

  Therefore, due to the combustion pressure, a force Fy directed toward the crankcase 30 is applied to the cylinder block 20 at both ends of the cylinder block 20 and is opposite to the crankcase 30 at portions other than both ends of the cylinder block 20. A force Fx1 directed toward the side is applied. That is, a force (bending stress) for bending the cylinder block 20 is applied to the cylinder block 20.

  In the present embodiment, as described above, the first straight line LL1 is located on the inner side of the cylinder block 20 than the second straight line LL2. Therefore, the amount of deformation of the cylinder block 20 due to the bending stress can be reduced as compared with the case where the first straight line LL1 is positioned on the outer side of the cylinder block 20 than the second straight line LL2.

  In addition, according to the present embodiment, the cutting formed on the outer wall surface 20c of the cylinder block 20 compared to the case where the first straight line LL1 is positioned on the outer side of the cylinder block 20 with respect to the second straight line LL2. The depth of the notch 20c1 can be reduced. As a result, the rigidity of the cylinder block 20 can be increased.

  Furthermore, according to the present embodiment, the internal combustion engine 10 is determined from the distance in the bore central axis direction between the block side force receiving axis MC and the case side force receiving axis FC in a state where the compression ratio of the internal combustion engine 10 is the lowest ratio. The length of the internal combustion engine 10 from the state in which the compression ratio is the maximum ratio reduced (i.e., from the state in which the cylinder block 20 is located at the uppermost position to the state in which the cylinder block 20 is located at the lowermost position). The maximum movement distance, which is the distance that the cylinder block 20 moves when the distance is changed, is longer than when the first straight line LL1 and the second straight line LL2 coincide (when e = 0). it can. Therefore, the compression ratio of the internal combustion engine 10 can be changed in a wider range.

  Further, the present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the first straight line LL1 and the second straight line LL2 coincide with each other (when e = 0), the distance D1 is 3 mm, and the distance D2 is 5 mm. Each of the distance D1 and the distance D2 may be set to a shorter distance so that the compression ratio of the internal combustion engine 10 is changed in the same range.

  A change in the magnitude | Tq | of the torque Tq with respect to the compression ratio of the internal combustion engine 10 in this case is shown in FIG. 17 in comparison with the case where the first straight line LL1 and the second straight line LL2 coincide. Here, in the state where the diameter (bore diameter) of the cylinder bore 21 is 86 mm, the distance (stroke length) that the piston 22 moves from the bottom dead center to the top dead center is 86 mm, and the compression ratio is the lowest ratio. It is assumed that the volume of the combustion chamber 41 (top dead center volume) when the piston 22 is at top dead center is 55.5 cc.

  A curve C1 in FIG. 17 shows a case where the distance D1 is set to 2.90 mm, the distance D2 is set to 4.84 mm, and the distance e is set to 0.97 mm. In this case, the ratio of the distance D2 to the distance D1 is 5/3. Further, the ratio of the distance e to the distance D1 is 1/3. On the other hand, a curve C2 in FIG. 17 shows a case where the distance D1 is set to 3 mm, the distance D2 is set to 5 mm, and the distance e is set to 0 mm.

  Thus, according to the present invention, even when the distance D1, the distance D2, and the distance e are set so that the range of the compression ratio of the internal combustion engine 10 that can be set by the compression ratio changing device 50 is equal, the torque Tq The maximum value of | Tq | can be made smaller than | Tq0 |.

  Furthermore, in the above-described embodiment, “the through hole formed in the movable cam portion 53c” with respect to “the distance D1 between the central axis line of the through hole HF formed in the fixed cam portion 53b and the central axis line FC of the fixed cam portion 53b”. The ratio of the distance D2 "between the central axis of the HM and the central axis MC of the movable cam portion 53c" may be a ratio other than 5/3.

  In the above-described embodiment, the “first straight line LL1 and the second straight line LL2” with respect to “the distance D1 between the central axis of the through hole HF formed in the fixed cam portion 53b and the central axis FC of the fixed cam portion 53b” The distance e ”may be a ratio other than 1/3.

  In addition, the above embodiment may be configured such that the first straight line LL1 is positioned on the outer side of the cylinder block 20 with respect to the second straight line LL2. Moreover, the said embodiment may employ | adopt a part of angle range D as a setting angle range.

It is the figure which showed typically the change of the compression ratio by the conventional compression ratio changing apparatus being driven. FIG. 2 is a diagram schematically showing a force applied to a compression ratio changing device when combustion occurs in the internal combustion engine shown in FIG. 1. It is the graph which showed the relationship between the torque around the case side receiving force axis line which generate | occur | produces with combustion pressure in the conventional compression ratio changing apparatus, and the rotation angle of a link axis line. It is the figure which showed typically the force applied to a compression ratio change apparatus, when combustion generate | occur | produces in the internal combustion engine to which the compression ratio change apparatus which concerns on this invention was applied. It is the graph which showed the relationship between the torque around the case side force receiving axis generated by the combustion pressure and the rotation angle of the link axis in the compression ratio changing device according to the present invention. 1 is a schematic perspective view of an internal combustion engine including a compression ratio changing device according to an embodiment of the present invention. FIG. 7 is a perspective view from above of the cylinder block shown in FIG. 6. FIG. 7 is a perspective view from below of the cylinder block shown in FIG. 6. It is sectional drawing which cut | disconnected the internal combustion engine in the plane in alignment with line 9-9 of FIG. It is sectional drawing which cut | disconnected the internal combustion engine in the plane in alignment with line 10-10 in FIG. It is a front view of the fixed cam part and movable cam part which were shown in FIG. FIG. 7 is a cross-sectional view of the internal combustion engine of FIG. 6 in which the compression ratio of the internal combustion engine is set to the lowest compression ratio. FIG. 7 is a cross-sectional view of the internal combustion engine of FIG. 6 in which the compression ratio of the internal combustion engine is set to a compression ratio between the lowest compression ratio and the highest compression ratio. FIG. 7 is a cross-sectional view of the internal combustion engine of FIG. 6 in which the compression ratio of the internal combustion engine is set to the highest compression ratio. It is the figure which showed typically the change of the position of the case side receiving force axis line, block side receiving force axis line, and link axis line accompanying the change of the compression ratio of the internal combustion engine by the compression ratio changing apparatus which concerns on embodiment of this invention. It is the figure which showed typically the force applied to a compression ratio change apparatus when combustion generate | occur | produces in the combustion chamber shown in FIG. It is the graph which showed the change with respect to the compression ratio of an internal combustion engine of the magnitude | size of the torque around the case side receiving force axis line which generate | occur | produces with combustion pressure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Cylinder block, 20c ... Side wall surface, 20c1 ... Notch part, 21 ... Cylinder bore, 22 ... Piston, 30 ... Crankcase, 31 ... Crankshaft, 40 ... Cylinder head, 41 ... Combustion chamber, 50 ... compression ratio changing device, 51 ... case side force receiving portion, 51a ... vertical wall portion, 51b ... cap portion, 51c ... bearing hole, 52 ... block side force receiving portion, 52a ... bearing hole, 53 ... link mechanism, 53a ... Eccentric shaft part, 53b ... Fixed cam part, 53c ... Movable cam part, 53d ... Worm wheel, 54 ... Link mechanism drive part, 54c ... Worm, MC ... Block side force receiving axis, FC ... Case side force receiving axis, LC ... Link axis, LL1 ... first straight line, LL2 ... second straight line.

Claims (3)

A cylinder bore, which is a cylindrical hole penetrating in a predetermined bore central axis direction, is formed, and is fixed to the cylinder block so as to cover one of the cylinder block housing the piston in the cylinder bore and the opening portion of the cylinder bore. The cylinder head is disposed on the opposite side of the cylinder head with respect to the cylinder block, and is movable relative to the cylinder block in the bore central axis direction, and the crankshaft connected to the piston is rotatable. A crankcase that is supported by the internal combustion engine,
A block side force receiving portion provided in the cylinder block;
A case-side force receiving portion provided in the crankcase;
A link mechanism that connects the block-side force receiving portion and the case-side force receiving portion, wherein a predetermined link axis in the link mechanism is parallel to the link axis, and the case-side force in the case-side force receiving portion A link mechanism configured to be able to rotate about the block side force receiving axis in the block side force receiving portion parallel to the link axis while rotating about the axis as the center of rotation;
Link mechanism driving means for driving the link mechanism so as to rotate and move the link axis within a predetermined set angle range with the case side force receiving axis as the center of rotation,
An internal combustion engine configured to change the compression ratio by changing the distance in the bore central axis direction between the crankcase and the cylinder block when the link mechanism is driven by the link mechanism driving means. In the compression ratio changing device,
The block side force receiving portion, the case side force receiving portion, and the link mechanism are straight lines parallel to the bore central axis direction in a plane orthogonal to the link axis, and the same plane and the block side force receiving axis A first line that is a straight line that passes through the intersection of the first and second straight lines that are parallel to the bore central axis direction in the same plane and that pass through the intersection of the same plane and the case-side force receiving axis; Are configured to be separated by a predetermined distance,
The link mechanism driving means is configured to receive the case side force from the state where the distance in the bore central axis direction between the block side force receiving axis and the case side force receiving axis is the longest to the state where the distance is the shortest. When the link axis is rotated in one direction with the axis as the center of rotation, the angle range that the rotation angle of the link axis around the force-receiving axis on the case side takes, and the distance is the shortest from the state where the distance is the longest Of the two angle ranges, the angle range that the same rotation angle takes when rotating the link axis in the direction opposite to the one direction with the case side force-receiving axis as the center of rotation until the state becomes Torr generated by pressure generated by combustion of mixed gas in a combustion chamber formed by a bore wall surface forming the cylinder bore, a lower surface of the cylinder head, and a top surface of the piston And a predetermined angular range within an angular range in which the maximum value of the magnitude of torque applied to the link mechanism is reduced so that the link axis is rotationally moved around the case side force receiving axis as the center of rotation. The compression ratio changing device employed as the set angle range. In the compression ratio changing device according to claim 1,
The block side force receiving portion is provided so as to extend outward from the outer wall surface of the cylinder block.
The block-side force receiving portion, the case-side force receiving portion, and the link mechanism are compression ratio changing devices configured such that the first straight line is located on the inner side of the cylinder block with respect to the second straight line. In the compression ratio changing device according to claim 2,
The outer wall surface of the cylinder block is formed with a notch that opens toward the outside of the cylinder block,
The link mechanism is configured to rotate and move the link axis around the case-side force receiving axis by being rotationally driven, and is disposed coaxially with the case-side force receiving axis and a part of the notch A worm wheel arranged to be housed in the section,
The link mechanism driving means is a compression ratio changing device configured to rotationally drive the worm wheel of the link mechanism.

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