JP2009024658A - Variable compression ratio internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture at low cost and stably operate a variable compression ratio internal combustion engine so formed that the compression ratio can be changed by moving a cylinder block and a crankcase relative to each other along the center axis of a cylinder. <P>SOLUTION: This internal combustion engine 1 comprises a camshaft 51 and a block side support part 52 and crankcase side support parts 54, 55 for storing the camshaft 51. In the internal combustion engine 1, the compression ratio can be changed by moving the cylinder block 2 and the crankcase 4 relative to each other along the center axis CCA of the cylinder 21 according to the rotational driving of the camshaft 51. In the internal combustion engine 1, the block side support part 52 formed separately from the cylinder block 2 is attachable to the cylinder block 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a variable compression ratio internal combustion engine configured such that a compression ratio can be changed by a relative movement of a cylinder block and a crankcase along a central axis of a cylinder.

  As this type of internal combustion engine, for example, those disclosed in Japanese Patent Application Laid-Open Nos. 2003-206871, 2006-316770, 2007-56837, 2007-64153, and the like are known. ing. In such an internal combustion engine, the crankcase (also referred to as a lower case) and the cylinder block are coupled so as to be relatively movable. The connecting portion is provided with a variable compression ratio mechanism for changing the compression ratio.

  The variable compression ratio mechanism includes a slide mechanism for sliding the cylinder block with respect to the crankcase. This slide mechanism is provided between the cylinder block and the crankcase. Specifically, this slide mechanism is composed of a cam shaft, a cam storage hole, and a bearing storage hole.

  The cam housing hole is provided in a raised portion formed at the lower part on both sides of the cylinder block. The bearing housing hole is provided in a standing wall portion provided so as to protrude outward (upper side) from the upper part of the crankcase.

  The cam shaft includes a shaft portion, a cam portion that is fixed to the shaft portion, and a movable bearing portion that is rotatably attached to the shaft portion. The cam portion is housed in the cam housing hole formed on the cylinder block side. The movable bearing portion is housed in the bearing housing hole formed on the crankcase side.

In the internal combustion engine having such a configuration, the camshaft is rotationally driven according to the operating state, so that the cylinder block slides relative to the crankcase along the central axis of the cylinder. Thereby, the compression ratio is changed. For example, the compression ratio is set low to suppress knocking or the like, or the compression ratio is set high to improve fuel consumption.
JP 2003-206871 A JP 2006-316770 A JP 2007-56837 A JP 2007-64153 A

  In order to realize this type of internal combustion engine at a lower cost so that it can be provided to the market or to operate more stably, a mechanical configuration around the variable compression ratio mechanism (for example, Mechanical structure considering ease of assembling work of the cylinder block and the crankcase including assembly of the variable compression ratio mechanism, rigidity around the variable compression ratio mechanism, smooth operation of the variable compression ratio mechanism There is room for further improvement. The present invention has been made to address such problems.

  The variable compression ratio internal combustion engine of the present invention includes a cylinder block, a crankcase, and a variable compression ratio mechanism.

  A cylinder is formed in the cylinder block. A piston is accommodated in this cylinder so as to be able to reciprocate. The crankcase is a member that rotatably supports the crankshaft. The crankshaft is rotationally driven based on the reciprocating movement of the piston.

  The variable compression ratio mechanism is configured such that the compression ratio can be changed by relatively moving (sliding) the cylinder block and the crankcase. This variable compression ratio mechanism includes a camshaft, a block-side support portion, and a crankcase-side support portion.

  The camshaft includes a columnar journal portion and a cam portion provided so as to protrude from the journal portion.

  The block-side support part is a member formed separately from the cylinder block. The block-side support portion is configured to be attached to the cylinder block. Further, the block side support portion is configured to accommodate one of the cam portion and the journal portion.

  The crankcase side support portion is provided on the crankcase side. The crankcase-side support portion is configured to accommodate the other (one different from the one of the cam portion and the journal portion).

  In this variable compression ratio mechanism, the cylinder block and the crankcase move relative to each other along the central axis of the cylinder (hereinafter referred to as “cylinder central axis”) in accordance with the rotational drive of the camshaft. Thus, the compression ratio can be changed.

  The compression ratio changing operation with such a configuration is as follows. The journal portion is supported by the one of the block side support portion and the crankcase side support portion, and the cam portion is supported by the other. Therefore, when the camshaft is rotationally driven according to the operating state, the relative positional relationship between the journal portion and the cam portion changes. That is, the protruding state of the cam portion from the journal portion changes. Then, the relative positional relationship between the block side support portion and the crankcase side support portion changes. Accordingly, the cylinder block and the crankcase relatively move along the cylinder center axis. Thereby, the compression ratio is changed.

  Here, in the variable compression ratio internal combustion engine of the present invention having such a configuration, as described above, the block side support portion that supports the camshaft on the cylinder block side is separate from the cylinder block. Is formed.

  Therefore, for example, it becomes extremely easy to form the cylinder block and the block side support portion with different materials. Thereby, the characteristics (rigidity, weight, etc.) required for the cylinder block and the characteristics (friction characteristics, wear characteristics, etc.) required for the block-side support part can be well balanced.

  Alternatively, the ease of assembling work between the cylinder block and the crankcase can be improved, for example, the block side support portion does not get in the way when the cylinder block and the crankcase are assembled.

  The variable compression ratio internal combustion engine may be configured such that the block side support portion has a thermal expansion coefficient closer to the camshaft than the cylinder block.

  According to this configuration, fluctuations in the clearance between the camshaft and the block-side support portion due to the difference in thermal expansion (or contraction) can be suppressed as much as possible. Thereby, generation | occurrence | production of the vibration at the time of high temperature can be suppressed as much as possible.

  The variable compression ratio internal combustion engine may be configured as follows: the cylinder block is made of a material mainly composed of light metal. Further, at least a portion of the camshaft and the block side support portion facing the camshaft is made of a material mainly composed of iron.

  Specifically, the cylinder block can be formed of, for example, an aluminum alloy or a magnesium alloy. The camshaft can be formed of, for example, carbon steel for machine structure or cast iron. For example, at least a portion of the block side support portion facing the camshaft may be formed of bearing steel or the like.

  According to this configuration, the weight of the cylinder block is reduced, and the wear resistance of the block side support portion is improved. In addition, since the thermal expansion coefficient is close between the camshaft and the block side support portion (at least the portion thereof), the variation of the clearance due to the temperature change can be suppressed as much as possible.

  The variable compression ratio internal combustion engine may be configured as follows: The crankcase includes a cylindrical frame. A cylinder block housing portion is formed inside the frame. The cylinder block accommodating portion is a space provided along the cylinder central axis direction so as to accommodate the cylinder block. The cylinder block housing portion may be provided so as to cover from the lower end portion to the upper portion of the cylinder block. The frame is provided with an opening. The opening is formed so that the block-side support portion can pass therethrough. Moreover, this opening part is formed so that the said block side support part can reciprocate inside.

  The variable compression ratio internal combustion engine of the present invention having such a configuration can be assembled as follows. First, the cylinder block is housed in the cylinder block housing portion inside the crankcase. At this time, a predetermined clearance is provided between the inner wall surface of the cylinder block housing portion and the outer wall surface of the cylinder block. The clearance is provided to such an extent that the relative movement between the crankcase and the cylinder block is smoothly performed, and there is no backlash between the two (specifically, whether the crankcase and the cylinder block are touched or not touched). Subsequently, the block-side support portion is attached to the cylinder block through the opening. At this time, the camshaft and the block side support portion may be assembled in advance.

  According to this configuration, since the “closed” cylindrical frame is provided in the crankcase, good rigidity of the crankcase is realized. Further, the ease of assembling work between the cylinder block and the crankcase can be further improved.

  The variable compression ratio internal combustion engine may be configured as follows: the crankcase-side support portion includes a frame-side support portion and a cover portion. The frame side support portion is provided on the frame at a position adjacent to the opening. The cover portion is provided so as to face the frame side support portion with the camshaft interposed therebetween. The cover portion is configured to be able to support the camshaft by being attached to the frame side support portion.

  The variable compression ratio internal combustion engine of the present invention having such a configuration can be assembled as follows. First, the cylinder block is housed in the crankcase (the cylinder block housing portion). On the other hand, the camshaft and the block side support portion are assembled in advance. Next, the block side support portion is attached to the cylinder block through the opening in a state where a portion of the cam shaft that is not accommodated in the block side support portion faces the frame side support portion. The Thereby, the assembly of the camshaft and the block-side support portion is mounted on the cylinder block. Subsequently, the cover part is attached to the frame side support part.

  According to such a configuration, the ease of assembling the cylinder block and the crankcase can be further improved. Moreover, the rigidity of the crankcase can be further improved by mounting the cover portion.

  The variable compression ratio internal combustion engine may be configured as follows: a plurality of the frame-side support portions are arranged along the longitudinal direction of the cylinder block. This longitudinal direction is a direction orthogonal to the cylinder central axis. Moreover, the said cover part corresponding to the said several frame side support part is integrally formed.

  According to such a configuration, the ease of assembling the cylinder block and the crankcase can be further improved. Moreover, the rigidity of the crankcase can be further improved by mounting the integral cover portion having a longitudinal direction along the longitudinal direction on the crankcase.

  The variable compression ratio internal combustion engine may be configured as follows: the journal portion is provided coaxially with the rotation center axis of the camshaft. The rotation center axis is a direction orthogonal to the cylinder center axis. The cam portion is formed of a substantially cylindrical circular cam. The circular cam is provided eccentrically from the rotation center axis and can rotate relative to the journal portion. The said block side support part is comprised so that the said circular cam may be rotatably supported, sliding with the surrounding surface of the said circular cam.

  In this configuration, the journal portion rotates around the rotation center axis when the camshaft is driven to rotate. On the other hand, the circular cam as the cam portion rotates in the block side support portion around an axis different from the rotation center axis while sliding with the block side support portion. And this circular cam rotates relatively with respect to the said journal part. As a result, the relative positional relationship between the journal portion and the circular cam changes.

  According to such a configuration, the compression ratio can be changed smoothly by relative movement between the crankcase and the cylinder block.

  In the block side support portion or the crankcase side support portion (the frame side support portion and the cover portion), a portion facing the camshaft may be coated with a coating for reducing wear or friction. Good.

  According to this configuration, the camshaft can be driven smoothly. In addition, wear of the block side support portion or the crankcase side support portion accompanying the rotational drive of the camshaft can be effectively suppressed.

  In the block side support part or the crankcase side support part (the frame side support part and the cover part), a portion having a higher wear resistance than the other part is attached to the part facing the camshaft. It may be.

  According to such a configuration, wear of the block side support portion or the crankcase side support portion associated with the rotational drive of the camshaft can be effectively suppressed.

  -The surface of the camshaft may be coated with a coating for reducing wear or friction.

  According to this configuration, the camshaft can be driven smoothly. Moreover, the wear accompanying the rotational drive of the camshaft can be effectively suppressed.

  -The surface which opposes the other in at least one of the said cylinder block and the said crankcase may be provided with the coating for wear or friction reduction. That is, the coating may be applied to one or both of a surface of the cylinder block that faces the crankcase and a surface of the crankcase that faces the cylinder block.

  According to such a configuration, the compression ratio can be changed smoothly by relative movement between the crankcase and the cylinder block.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings.

  In addition, the description about the following embodiment is specific to the extent possible, merely an example of the embodiment of the present invention in order to satisfy the description requirement (description requirement / practicability requirement) of the specification required by law. It is only what is described in. Therefore, as will be described later, it is quite natural that the present invention is not limited to the specific configurations of the embodiments described below. The various modifications that can be made to this embodiment are described together at the end because they would interfere with the understanding of a consistent embodiment description if inserted during the description of the embodiment. Yes.

<Schematic Configuration of Variable Compression Ratio Internal Combustion Engine of Embodiment>
FIG.1 and FIG.2 is a sectional side view which shows schematic structure of the engine 1 of this embodiment. FIG. 3 is an exploded perspective view of the engine 1 shown in FIGS. 1 and 2. 1 corresponds to a cross-sectional view taken along the line II in FIG. 2 corresponds to a cross-sectional view taken along the line II-II in FIG. Hereinafter, the schematic configuration of the engine 1 will be described with reference to FIGS. 1 to 3.

  Referring to FIG. 1, the engine 1 includes a cylinder block 2, a cylinder head 3, a crankcase 4, and a variable compression ratio mechanism 5. The engine 1 is configured such that the compression ratio can be changed by moving (sliding) the cylinder block 2 along the cylinder center axis CCA relative to the crankcase 4 by the variable compression ratio mechanism 5.

  In the present embodiment, the cylinder block 2 is made of an aluminum alloy and has a substantially rectangular parallelepiped shape. A cylinder 21 is formed inside the cylinder block 2. The cylinder 21 is a substantially cylindrical through hole. A piston 22 is accommodated in the cylinder 21 so as to be capable of reciprocating along the cylinder center axis CCA.

  Referring to FIG. 3, in the present embodiment, four cylinders 21 are provided in a line along the cylinder arrangement direction AD. That is, the cylinder block 2 is formed to have a longitudinal direction parallel to the cylinder arrangement direction AD.

  Referring to FIG. 1, the cylinder head 3 is joined to the upper end of the cylinder block 2 (the end on the top dead center side of the piston 22). The cylinder head 3 is fixed to the upper end portion of the cylinder block 2 with a bolt or the like so as not to move relative to the cylinder block 2.

  The crankcase 4 includes a cylindrical frame 41. In the present embodiment, the crankcase 4 (frame 41) is integrally formed of an aluminum alloy.

  The frame 41 is formed to have a longitudinal direction parallel to the cylinder arrangement direction AD. The frame 41 is formed in a shape that surrounds the outer surface of the cylinder block 2 with a predetermined clearance. This clearance is set to such an extent that the relative movement between the cylinder block 2 and the crankcase 4 is performed smoothly, and there is no backlash between the two (the degree of touching or not touching: for example, about several millimeters). ing.

  Specifically, a cylinder block housing portion 41 a that is a space in which the cylinder block 2 can be housed is formed inside the frame 41. The cylinder block accommodating portion 41a is provided along the cylinder center axis CCA. Moreover, the cylinder block accommodating part 41a is provided so that it may open toward upper direction in the figure so that the cylinder block 2 can be inserted from upper direction in the figure. The inner wall surface of the cylinder block housing portion 41a is formed so as to provide the above-described predetermined clearance with the outer wall surface of the cylinder block 2 in a state in which the cylinder block 2 is housed.

  In the present embodiment, the frame 41 (cylinder block accommodating portion 41a) is formed so as to cover from the lower end portion to the upper portion of the cylinder block 2. Note that the upper end portion of the cylinder block 2 is provided so as to protrude above the frame 41 for joining with the cylinder head 3.

  A crankshaft 42 is rotatably supported on the lower end of the crankcase 4 via a bearing. The crankshaft 42 is disposed in parallel with the cylinder arrangement direction AD. The crankshaft 42 is driven to rotate based on the reciprocating movement of the piston (see FIG. 1) along the cylinder center axis CCA.

<Detailed Configuration of Variable Compression Ratio Mechanism of Embodiment>
Hereinafter, a detailed configuration of the variable compression ratio mechanism 5 of the present embodiment will be described with reference to FIGS. 1 to 3 and other drawings as necessary.

  With reference to FIGS. 1 to 3, in the present embodiment, a pair of variable compression ratio mechanisms 5 are provided on both side walls and in the vicinity thereof along the cylinder arrangement direction AD of the frame 41. Further, one variable compression ratio mechanism 5 and the other variable compression ratio mechanism 5 are arranged and configured substantially symmetrically with respect to a plane through which the cylinder center axis CCA of all the cylinders 21 passes.

<< Camshaft >>
The variable compression ratio mechanism 5 is configured to be able to relatively move (slide) the cylinder block 2 and the crankcase 4 along the cylinder center axis CCA by the rotational drive of the camshaft 51. The cam shaft 51 is made of carbon steel for mechanical structure (S45C or the like), and includes a journal portion 51a, a circular cam portion 51b, an eccentric shaft portion 51c, and a worm wheel 51d.

  FIG. 4 is a perspective view showing a part of the camshaft 51 shown in FIGS. 1 to 3 in an exploded manner. Hereinafter, referring to FIGS. 1 to 4, the journal portion 51 a is a cylindrical member, and is a rotation center axis of the camshaft 51 (this is parallel to the cylinder arrangement direction AD, that is, orthogonal to the cylinder center axis CCA, This is provided coaxially with the dot-dash line in FIG.

  The surface 51a1 of the journal part 51a is formed in a cylindrical surface shape. In the present embodiment, the surface 51a1 is provided with a coating for reducing friction and wear. Specifically, in the present embodiment, the surface 51a1 is coated with DLC (diamond-like carbon).

  The circular cam portion 51b is provided eccentric from the rotation center axis. The circular cam portion 51b is a cylindrical member having a diameter larger than that of the journal portion 51a, and is provided according to the number of cylinders. That is, the same number (4 in the present embodiment) of circular cam portions 51b as the number of cylinders is provided for one camshaft 51. Each circular cam portion 51b is disposed at a position corresponding to the cylinder center axis CCA. Journal portions 51 a are provided between the adjacent circular cam portions 51 b and at both ends of the camshaft 51.

  A surface 51b1 of the circular cam portion 51b is formed in a cylindrical surface shape. In the present embodiment, the surface 51b1 is also provided with a coating for reducing friction and wear, like the surface 51a1 of the journal portion 51a.

  The eccentric shaft portion 51c is a round bar-like member having a longitudinal direction along the cylinder arrangement direction AD, and a worm wheel 51d is provided at substantially the center thereof. The worm wheel 51d is formed integrally with the eccentric shaft portion 51c. The worm wheel 51d is provided such that its central axis is coaxial with the rotation central axis. The worm wheel 51d is driven to rotate by being engaged with a worm W that is a cylindrical gear mounted on a rotation drive shaft of the motor M (which is orthogonal to the rotation center axis and the cylinder center axis CCA). It has become.

  The eccentric shaft portion 51c is provided so as to be inserted at a position eccentric from the central axis of the journal portion 51a and the central axis of the circular cam portion 51b. That is, as shown in FIGS. 1 and 4, the eccentric shaft portion 51c is in a state where one end (lower end in the drawing) of the journal portion 51a and one end (lower end in the drawing) coincide with each other. The journal part 51a and the circular cam part 51b are provided so as to be inserted at a position near the one end (lower part).

  In the present embodiment, the journal portion 51a is fixed to the eccentric shaft portion 51c so as not to rotate around the eccentric shaft portion 51c. That is, the journal portion 51a can be driven to rotate integrally with the worm wheel 51d around the rotation center axis as the worm wheel 51d rotates.

  On the other hand, the circular cam portion 51b can freely rotate around the eccentric shaft portion 51c. That is, the circular cam portion 51b can be rotated relative to the journal portion 51a.

<< Block side support part >>
1 to 3 again, the circular cam portion 51b is rotatably supported by the block-side support portion 52. In other words, the block-side support portion 52 is configured to rotatably support the circular cam portion 51b while sliding with the peripheral surface of the circular cam portion 51b.

  In the present embodiment, the block-side support portion 52 is a block-shaped member and is integrally (seamlessly) formed of bearing steel. That is, in the present embodiment, the block-side support portion 52 is configured so that the thermal expansion coefficient is closer to the carbon steel that constitutes the camshaft than the aluminum alloy that constitutes the cylinder block 2.

  A bearing hole 52 a is formed in the block side support portion 52. The bearing hole 52a is a through hole having an inner diameter corresponding to the outer diameter of the circular cam portion 51b (so that it can slide with the peripheral surface of the circular cam portion 51b).

  FIG. 5 is a perspective view showing the cylinder block 2 and the block support 52 shown in FIG. FIG. 6 is an exploded perspective view of the cylinder block 2 and the block-side support portion 52 shown in FIG. 3 to 6, the block-side support portion 52 is formed separately from the cylinder block 2 and is configured to be attached to the cylinder block 2 using bolts. The block support 52 is provided at a position corresponding to the cylinder center axis CCA.

  Referring to FIGS. 1 to 3 again, the frame 41 is provided with a plurality of openings 53 as many as the block side support portions 52. The opening 53 is a through-hole, and is provided so that the block-side support 52 can penetrate. The opening 53 is larger than the height dimension of the block-side support 52 (the dimension in the direction along the cylinder center axis CCA) so that the block-side support 52 can reciprocate along the cylinder center axis CCA. It is formed to a height dimension.

<< Crankcase side support part >>
A plurality of frame side support portions 54 are formed on the frame 41. Each frame side support portion 54 is provided so as to be adjacent to the opening portion 53. In other words, the plurality of frame side support portions 54 are provided on both sides of each opening 53 and are arranged along the cylinder arrangement direction AD.

  The frame side support portion 54 is provided with a journal support recess 54a. The journal support recess 54a is a semi-cylindrical recess having an inner diameter corresponding to the outer diameter of the journal portion 51a.

  7A and 7B are enlarged side sectional views of the periphery of the frame side support portion 54 shown in FIG. Referring to FIGS. 7A and 7B, a liner 54b is provided in a portion of the journal support recess 54a that faces the journal portion 51a. The liner 54b is made of a bearing steel having a higher wear resistance than the other portion (aluminum alloy) in the frame side support portion 54, and is formed in a semi-cylindrical shape.

  Referring to FIG. 2, a cover portion 55 is attached to the frame 41. The cover portion 55 is made of an aluminum alloy, and is provided so as to face the frame-side support portion 54 with the camshaft 51 (journal portion 51a) interposed therebetween. The cover portion 55 is configured to be rotatably attached to the camshaft 51 (journal portion 51a) together with the frame side support portion 54 by being attached to the frame side support portion 54.

  Referring to FIG. 3, the cover portions 55 corresponding to the plurality of frame side support portions 54 (all the frame side support portions 54 in one variable compression ratio mechanism 5) have a longitudinal direction along the cylinder arrangement direction AD. Moreover, it is formed integrally (seamless). The cover portion 55 is formed with a journal support recess 55a, a bearing housing portion 55b, and a gear housing portion 55c.

  The journal support recess 55a is provided at a position facing the journal support recess 54a of the frame side support 54. The journal support recess 55a is a semi-cylindrical recess symmetrical to the journal support recess 54a and has an inner diameter corresponding to the outer diameter of the journal portion 51a. That is, the cover part 55 is configured in a substantially arch shape along the cylinder center axis CCA in a side sectional view.

  The bearing housing portion 55 b is a concave portion provided at a position facing the block side support portion 52. The bearing accommodating portion 55b is formed so as to accommodate the block-side support portion 52 protruding from the opening 53 to the outside of the frame 41 so as to be reciprocally movable along the cylinder center axis CCA.

  The gear accommodating portion 55c is a recess provided at a position facing the worm wheel 51d. The gear accommodating portion 55c is formed so as to accommodate the worm wheel 51d protruding to the outside of the frame 41.

  Referring to FIGS. 7A and 7B, a liner 55d is provided in a portion of the journal support recess 55a that faces the journal portion 51a. The liner 55d is made of a bearing steel having a higher wear resistance than other portions (aluminum alloy) in the cover portion 55, and is formed in a semi-cylindrical shape.

  As shown in FIG. 7B, the cover portion 55 is fixed to the frame side support portion 54 by the bolt 56, and the liner 55d is joined to the liner 54b, so that the journal portion 51a is placed inside these joined bodies. A bearing hole for rotatably supporting the shaft is formed. That is, the frame-side support portion 54 and the cover portion 55 constitute the crankcase-side support portion of the present invention that accommodates the journal portion 51a.

<Description of Operation of Variable Compression Ratio Mechanism of Embodiment>
8 to 10 are diagrams showing how the compression ratio changes in the engine 1 shown in FIG. Hereinafter, the compression ratio changing operation by the variable compression ratio mechanism 5 will be briefly described with reference to these drawings.

  When the camshaft 51 is rotationally driven, the journal portion 51a slides between the inner surfaces of the liners 54b and 55d, and the frame side support portion 54 and the cover portion 55 are centered on the rotation center axis of the camshaft 51. It rotates inside the bearing hole formed therebetween. At this time, the eccentric shaft portion 51 c rotates around the rotation center axis of the camshaft 51. That is, the eccentric shaft part 51c rotates integrally with the journal part 51a.

  On the other hand, the circular cam portion 51b rotates inside the block-side support portion 52 around an axis different from the rotation center axis while sliding with the inner surface of the bearing hole 52a. Moreover, the circular cam part 51b rotates relatively with respect to the eccentric shaft part 51c. That is, the circular cam portion 51b rotates relative to the journal portion 51a around the central axis of the eccentric shaft portion 51c. Thereby, the relative position with respect to the journal part 51a of the circular cam part 51b changes.

  At this time, the movement of the circular cam portion 51b in the engine width direction (the longitudinal direction and the direction orthogonal to the cylinder center axis CCA: the left-right direction in FIGS. 8 to 10) is restricted by the block-side support portion 52. . Further, the position of the journal portion 51a is unchanged. Therefore, when the camshaft 51 is driven to rotate, as shown in FIGS. 8 to 10, the circular cam portion 51b moves up and down as the eccentric shaft portion 51c moves up and down due to the rotation around the rotation center axis. Move.

  In the state where the compression ratio of the engine 1 is the highest, as shown in FIG. 8, the eccentric shaft portion 51c is located at the lowest position. In this case, the circular cam portion 51b is also located at the lowest position.

  From the state shown in FIG. 8, the camshaft 51 is rotationally driven as indicated by the arrows in the figure (the camshaft 51 on the right side in the figure is driven to rotate clockwise and the camshaft on the left side in the figure) 51 is rotated counterclockwise). As a result, the eccentric shaft portion 51c rises from the position shown in FIG. 8, and the circular cam portion 51b rises.

  Therefore, as shown in FIG. 9, the block-side support portion 52 rises as the circular cam portion 51 b rises due to the rotation of the camshaft 51. As a result, the cylinder block 2 rises relative to the crankcase 4. When the cylinder head 3 is separated from the crankcase 4 by the rising of the cylinder block 2, the distance between the top dead center position of the piston 22 and the lower end surface of the cylinder head 3 is extended. That is, the compression ratio of the engine 1 is reduced.

  As shown in FIG. 9, when the position of the eccentric shaft portion 51c is intermediate between the uppermost and lowermost positions, the compression ratio is also intermediate between the highest value and the lowest value. As shown in FIG. 10, when the position of the eccentric shaft portion 51c reaches the uppermost position, the compression ratio becomes the lowest.

  When the compression ratio is increased from the state shown in FIG. 10 where the compression ratio of the engine 1 is the lowest, the camshaft 51 is further driven to rotate in the same direction as described above, or the camshaft 51 is reversed from the above. It is rotationally driven in the direction.

<Effects of Configuration of Embodiment>
Hereinafter, effects of the configuration of the present embodiment will be described with reference to the drawings.

  In the engine 1 of the present embodiment, the block side support portion 52 that supports the camshaft 51 by accommodating the journal portion 51 a on the cylinder block 2 side is formed separately from the cylinder block 2. The cylindrical frame 41 is provided with an opening 53 so as to correspond to the block side support portion 52. Further, a crankcase side support portion that supports the camshaft 51 on the crankcase 4 side is constituted by a frame side support portion 54 and a cover portion 55. The camshaft 51 is supported by the crankcase 4 by attaching the cover portion 55 to the frame side support portion 54.

  The assembly of the engine 1 having such a configuration can be performed as follows.

  First, the cylinder block 2 is accommodated in the crankcase 4 by inserting the cylinder block 2 into the cylinder block accommodating portion 41a. At this time, since the block-side support portion 52 is not yet mounted on the cylinder block 2, the cylinder block 2 is accommodated in the crankcase 4 relatively smoothly.

  On the other hand, four block-side support portions 52 are assembled at positions corresponding to the circular cam portions 51 b of one camshaft 51. That is, an assembly of the camshaft 51 and the block side support portion 52 is formed. Two sets of this assembly are prepared.

  Next, each block-side support portion 52 is inserted into each opening 53 and comes into contact with the cylinder block 2. Then, each block side support part 52 is fixed to the cylinder block 2 with a bolt. At this time, the journal part 51 a faces the journal support recessed part 54 a in the frame side support part 54.

  Subsequently, the cover portion 55 is attached to the frame side support portion 54 so as to cover the assembly of the camshaft 51 and the block side support portion 52. Thereby, the journal part 51a is rotatably supported by the frame side support part 54 and the cover part 55.

  In this manner, the assembly of the camshaft 51 and the block side support portion 52 is attached to the cylinder block 2 and the crankcase 4 in a very simple process. Therefore, according to the present embodiment, the ease of assembling work between the cylinder block 2 and the crankcase 4 is improved.

  -In this embodiment, the block side support part 52 is integrally formed by bearing steel (seamlessly). Therefore, the circular cam portion 51b can be stably held even if it receives stress during the rotation and movement of the circular cam portion 51b or during combustion. That is, the rigidity of the bearing portion of the circular cam portion 51b is improved.

  -In this embodiment, the cylinder block 2 is comprised from the material which has a light metal as a main component, and the camshaft 51 and the block side support part 52 are comprised from the material which has iron as a main component.

  According to this configuration, the weight of the engine 1 can be reduced well, and the wear of the block-side support portion 52 accompanying the rotational drive of the camshaft 51 can be suppressed as much as possible.

  Further, according to such a configuration, the thermal expansion coefficient of the block side support portion 52 is closer to that of the camshaft 51 than the cylinder block 2.

  Therefore, the fluctuation | variation of the clearance of the journal part 51a and the bearing hole 52a by the difference in the thermal expansion (or shrinkage | contraction) amount of the cam shaft 51 and the block side support part 52 can be suppressed as much as possible. Thereby, the occurrence of vibration at high temperatures can be suppressed as much as possible. Moreover, the fluctuation | variation of the sliding state with the journal part 51a and the bearing hole 52a accompanying a temperature change is suppressed. Thereby, the compression ratio changing operation can be performed smoothly and reliably.

  In the present embodiment, the crankcase 4 includes a cylindrical frame 41 that is “closed” in plan view. In addition, an arch-shaped cover portion 55 along the vertical direction is attached to the frame 41. Thereby, the rigidity of the crankcase 4 is improved.

  In the present embodiment, the plurality of frame side support portions 54 are arranged along the longitudinal direction of the cylinder block 2. Moreover, the cover part 55 corresponding to the some frame side support part 54 is integrally formed (seamlessly).

  According to such a configuration, the ease of assembling work between the cylinder block 2 and the crankcase 4 can be further improved. Moreover, the rigidity of the crankcase 4 is further improved by attaching the integral cover portion 55 having a longitudinal direction along the longitudinal direction of the cylinder block 2 and the crankcase 4 to the crankcase 4.

  In the present embodiment, the journal portion 51 a is provided coaxially with the rotation center axis of the camshaft 51. In addition, the circular cam portion 51b is provided eccentrically from the rotation center axis, and can rotate relative to the journal portion 51a. Furthermore, the block-side support portion 52 supports the circular cam portion 51b so as to be rotatable while sliding with the peripheral surface of the circular cam portion 51b.

  According to such a configuration, the compression ratio can be changed smoothly by relative movement between the cylinder block 2 and the crankcase 4.

  In the present embodiment, the crankcase 4 and the main body portion of the cover portion 55 are made of a material mainly composed of light metal, and iron-based liners 54b and 55d are provided in the bearing portion.

  According to such a configuration, the engine 1 can be reduced in weight well, and wear of the crankcase 4 accompanying the rotational drive of the camshaft 51 can be suppressed as much as possible.

  In the present embodiment, the surface of the camshaft 51 (the surface 51a1 of the journal portion 51a and the surface 51b1 of the circular cam portion 51b) is coated to reduce wear and friction.

  According to such a configuration, the rotational drive of the camshaft 51 can be performed smoothly. Moreover, the wear accompanying the rotational drive of the camshaft 51 can be effectively suppressed. As a result, the compression ratio changing operation can be performed more smoothly and reliably (especially when starting or when the engine is stopped, which tends to be insufficient in the amount of lubricating oil).

<List of examples of modification>
Note that, as described above, the above-described embodiment is merely an example of a specific configuration of the present invention considered to be the best by the applicant at the time of filing of the present application. It should not be limited at all by the embodiment. Therefore, it goes without saying that various modifications can be made to the specific configurations shown in the above-described embodiments within a range that does not change the essential part of the present invention.

  Hereinafter, some modifications will be exemplified. Here, in the following description of the modified example, components having the same configurations and functions as the components in the above-described embodiment are given the same name and the same reference numerals in the modified example. And And about description of the said component, description in the above-mentioned embodiment shall be suitably used in the range which is not inconsistent.

  However, it goes without saying that the modified examples are not limited to the following. The limited interpretation of the present invention based on the description of the above-described embodiment and the following modifications unfairly harms the interests of the applicant (especially rushing the application under the principle of prior application), but improperly imitates the imitator. It is good and not allowed.

  Further, it goes without saying that the configuration of the above-described embodiment and the configuration described in each of the following modifications can be applied in an appropriate combination within a technically consistent range.

  (1) The present invention is applicable to gasoline engines, diesel engines, methanol engines, bioethanol engines, and any other types of internal combustion engines. The number of cylinders and the cylinder arrangement method (in-line, V-type, horizontally opposed) are not particularly limited.

  (2) The configuration of the journal portion 51a, the circular cam portion 51b, the block-side support portion 52, and the frame-side support portion 54, and their corresponding relationships can be changed from the above-described embodiment.

  That is, for example, contrary to the above-described embodiment, the variable compression ratio mechanism 5 is configured such that the journal portion 51 a is accommodated in the block-side support portion 52 and the circular cam portion 51 b is accommodated in the frame-side support portion 54. Can be configured. Or contrary to the case of the above-mentioned embodiment, while the journal part 51a can rotate relatively with respect to the eccentric shaft part 51c, the circular cam part 51b may be fixed to the eccentric shaft part 51c.

  (3) It is not an essential requirement of the present invention that the entire block side support portion 52 is made of the same material as in the above-described embodiment.

  Therefore, for example, if the portion of the block-side support portion 52 that faces the camshaft 51 is made of an iron-based material, the material of the other portions is not particularly limited. As a specific example, the portion of the block-side support 52 that faces the camshaft 51 is made of a liner made of a wear-resistant material (for example, bearing steel), like the crankcase-side support in the above-described embodiment. It may be provided. In this case, the portion other than the liner of the block side support portion 52 can be made of the same or similar material as the crankcase 4 or the cylinder block 2.

  (4) The configuration and material of the liner in the crankcase side support portion (the frame side support portion 54 and the cover portion 55 in the above embodiment) are not limited to those in the above embodiment.

  Further, like the frame side support portion 54 and the cover portion 55, a liner may be attached to the block side support portion 52.

Furthermore, instead of the liner, an iron-based coating such as a coating containing iron silicide (Fe-Si based material: Fe ₃ Si, FeSi, FeSi ₂ , etc.) as a main component may be used. In this case, the crankcase 4 and the cover portion 55 may be made of cast iron in consideration of affinity with the coating layer and the like.

  Even when a liner is used, the crankcase 4 and the cover portion 55 can be made of an iron-based material such as cast iron in order to bring the thermal expansion coefficient close to that of the liner.

  (5) The cover portion 55 may be divided into a number corresponding to the plurality of frame side support portions 54. At this time, the cover housing 55 may not be provided with the bearing housing portion 55b or the gear housing portion 55c.

  (6) At least one of the coating on the surface 51a1 of the journal portion 51a and the coating on the surface 51b1 of the circular cam portion 51b may be omitted. Specifically, for example, the coating is applied only to those with more severe sliding conditions (in the above-described embodiment, the circular cam portion 51b that applies relatively large pressure in the vertical and horizontal directions as well as sliding). It may be.

  (7) The coating applied to the camshaft 51 is a member that supports the camshaft 51 in a rotatable manner together with the camshaft 51 or in place of the camshaft 51 (the block-side support portion 52 and / or the main shaft 51). It may be provided on the frame side support part 54 and the cover part 55) constituting the crankcase side support part of the invention. That is, the coating as described above may be applied to a portion of the member facing the camshaft 51.

  (8) Even if the coating as described above is applied to the surface of at least one of the cylinder block 2 and the crankcase 4 in the portion where the cylinder block 2 and the crankcase 4 (frame 41) face each other. Good.

  For example, as shown in FIG. 11, the coating 201 may be provided over the entire outer peripheral surface accommodated in the frame 41 (see FIG. 3) in the cylinder block 2.

  Alternatively, as shown in FIG. 12, the coating 201 may be provided only on the upper end portion of the outer peripheral surface and the portion that can slide with the inner wall surface of the frame 41 (see FIG. 3). .

  Alternatively, as shown in FIG. 13, the coating 201 may be provided only on the upper end portion, which can receive a load due to the combustion pressure.

  According to such a configuration, the compression ratio can be changed smoothly by relative movement between the cylinder block 2 and the crankcase 4.

  (9) If the coating applied to the camshaft 51 or the like is provided for the purpose of reducing either friction or wear, a predetermined effect of smooth operation or wear reduction can be obtained.

  From this point of view, the material used for coating is not limited to DLC. For example, a solid lubricating film such as a ceramic coating mainly composed of chromium oxide, molybdenum disulfide, or hard chromium carbide plating can be used favorably.

  (10) Other modifications not specifically mentioned are naturally included in the technical scope of the present invention within the scope not changing the essential part of the present invention. For example, the material can be changed as appropriate. Moreover, what was one piece (one piece) can be made into another body (two piece), and vice versa.

  In addition, in each element constituting the means for solving the problems of the present invention, elements expressed functionally and functionally include the specific structures disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function.

It is a sectional side view (II sectional drawing in FIG. 3) which shows schematic structure of the engine which is one Embodiment of this invention. It is a sectional side view (II-II sectional view in Drawing 3) showing a schematic structure of an engine which is one embodiment of the present invention. FIG. 3 is an exploded perspective view of the engine shown in FIGS. 1 and 2. FIG. 4 is a perspective view showing a part of the camshaft shown in FIGS. 1 to 3 in an exploded manner. It is a perspective view which takes out and shows the cylinder block and block side support part which are shown by FIG. It is a disassembled perspective view of the cylinder block and block side support part which are shown by FIG. FIG. 3 is an enlarged side sectional view of a periphery of a frame side support portion shown in FIG. 2. FIG. 3 is an enlarged side sectional view of a periphery of a frame side support portion shown in FIG. 2. It is a figure which shows the mode of the compression ratio change in the engine shown by FIG. It is a figure which shows the mode of the compression ratio change in the engine shown by FIG. It is a figure which shows the mode of the compression ratio change in the engine shown by FIG. It is a perspective view which shows the modification of the cylinder block shown by FIG. It is a perspective view which shows the other modification of the cylinder block shown by FIG. FIG. 10 is a perspective view showing still another modification of the cylinder block shown in FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Cylinder block 21 ... Cylinder 22 ... Piston 3 ... Cylinder head 4 ... Crankcase 41 ... Frame 41a ... Cylinder block accommodating part 5 ... Variable compression ratio mechanism 51 ... Camshaft 51a ... Journal part 51a1 ... Surface 51b ... Circular Cam part 51b1 ... Surface 51c ... Eccentric shaft part 51d ... Worm wheel 52 ... Block side support part 52a ... Bearing hole 53 ... Opening part 54 ... Frame side support part 54b ... Liner 55 ... Cover part 55b ... Bearing accommodation part 55c ... Gear accommodation 55d ... Liner 56 ... Bolt 201 ... Coating AD ... Cylinder arrangement direction CCA ... Cylinder center axis
M ... Motor W ... Warm

Claims (11)

A cylinder block formed with a cylinder for reciprocally moving the piston;
A crankcase that rotatably supports a crankshaft that is rotationally driven based on the reciprocating movement of the piston; and
A camshaft comprising a columnar journal portion and a cam portion provided so as to protrude from the journal portion;
A block-side support portion separate from the cylinder block, configured to accommodate one of the cam portion and the journal portion, and configured to be attached to the cylinder block;
A crankcase-side support portion configured to accommodate the other, provided on the crankcase side;
With
Variable compression characterized in that the compression ratio can be changed by the relative movement of the cylinder block and the crankcase along the central axis of the cylinder in accordance with the rotational drive of the camshaft. Specific internal combustion engine. The variable compression ratio internal combustion engine according to claim 1,
The variable compression ratio internal combustion engine, wherein the block side support portion is configured to have a thermal expansion coefficient closer to that of the camshaft than the cylinder block. A variable compression ratio internal combustion engine according to claim 2,
The cylinder block is made of a material whose main component is light metal,
The variable compression ratio internal combustion engine, wherein at least a portion of the camshaft and the block side support portion facing the camshaft is made of a material mainly composed of iron. A variable compression ratio internal combustion engine according to any one of claims 1 to 3,
The crankcase is
A cylinder frame containing a cylinder block housing portion, which is a space provided along the central axis direction so as to accommodate the cylinder block;
The variable compression ratio internal combustion engine, wherein the frame is provided with an opening through which the block-side support portion can reciprocate. A variable compression ratio internal combustion engine according to claim 4,
The crankcase side support part is
A frame-side support provided on the frame at a position adjacent to the opening;
A cover portion provided so as to face the frame side support portion with the camshaft interposed therebetween, and configured to be able to support the camshaft by being attached to the frame side support portion;
A variable compression ratio internal combustion engine comprising: The variable compression ratio internal combustion engine according to claim 5,
A plurality of the frame side support portions are arranged along the longitudinal direction of the cylinder block perpendicular to the central axis,
The variable compression ratio internal combustion engine, wherein the cover portions corresponding to the plurality of frame side support portions are integrally formed. A variable compression ratio internal combustion engine according to any one of claims 1 to 6,
The journal portion is provided coaxially with a rotation center axis of the camshaft orthogonal to the center axis,
The cam portion is formed of a circular cam that is provided eccentrically from the rotation center axis and can rotate relative to the journal portion;
The variable compression ratio internal combustion engine, wherein the block side support portion is configured to rotatably support the circular cam while sliding on a peripheral surface of the circular cam. A variable compression ratio internal combustion engine according to any one of claims 1 to 7,
The variable compression ratio internal combustion engine, wherein a coating for reducing wear or friction is applied to a portion of the crankcase side support portion or the block side support portion that faces the camshaft. A variable compression ratio internal combustion engine according to any one of claims 1 to 8,
A variable compression ratio internal combustion engine, wherein a portion of the crankcase side support portion or the block side support portion facing the camshaft is provided with a liner having higher wear resistance than other portions. organ. A variable compression ratio internal combustion engine according to any one of claims 1 to 9,
A variable compression ratio internal combustion engine characterized in that a coating for reducing wear or friction is applied to a surface of the camshaft. A variable compression ratio internal combustion engine according to any one of claims 1 to 10,
A variable compression ratio internal combustion engine, characterized in that a surface of at least one of the cylinder block and the crankcase facing the other is coated with a coating for reducing wear or friction.

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