JP2012241678A - Double link type piston-crank mechanism for internal combustion engine - Google Patents

Abstract

In a multi-link piston-crank mechanism, support rigidity of a bearing portion of a crankshaft and a support shaft is improved.
A link row composed of a rocker arm 31, a first link 32 and a second link 33 of a multi-link type piston-crank mechanism 30 for linking a piston and a crank pin of a crankshaft 4 is formed in an upward channel shape and a U shape. By adopting the layout, the crankshaft 4 is arranged on the side of the cylinder 6 to reduce the overall height of the engine. Corresponding to the loads F1 and F2 acting on the bearing portions of the shafts 21 and 4, the support shaft bolts 52 are inserted from the lower side of the engine to fix the support shaft cap 51 to the lower surface side of the cylinder block 21, and the crank The shaft bolt 55 is inserted from above the engine so that the crankshaft cap 54 is fixed to the upper surface side of the cylinder block 21.
[Selection] Figure 1

Description

  The present invention relates to an improvement of a multi-link piston-crank mechanism for an internal combustion engine in which a piston and a crank pin of a crankshaft are linked by a plurality of links.

  Patent Document 1 describes a technology that uses a multi-link type piston-crank mechanism to arrange a crankshaft on the side of a cylinder in which a piston is fitted to reduce the vertical dimension of the engine, that is, the overall height of the engine. Has been. In this multi-link type piston-crank mechanism, a rocker arm is swingably attached to a support shaft supported by an engine stationary body such as a cylinder block, and one end of the rocker arm and a piston are connected by a first link. The other end of the rocker arm and the crank pin of the crankshaft are connected by a second link.

JP 2006-52667 A

  In such a multi-link type piston-crank mechanism, with respect to the engine width direction, the axis of the support shaft of the rocker arm is arranged between the axis of the piston pin connecting the piston and the first link and the axis of the crankshaft. The shaft center of the support shaft of the rocker arm is disposed below the shaft center of the piston pin and the shaft shaft of the crankshaft in the vertical direction of the engine. As a result, the link row composed of the rocker arm, the first link, and the second link is formed in an upward channel shape / U shape, and the cylinder and the crankshaft are arranged in the engine width direction above the support shaft and the rocker arm. The arranged layout can be realized.

  However, in the multi-link type piston-crank mechanism having such a layout, an internal combustion engine having a general single-link type piston-crank mechanism in which a piston and a crank pin are connected by a single link such as a connecting rod. Since the input direction of the combustion load acting on the bearing portion of the crankshaft is greatly different, it is necessary to take countermeasures. For example, in the case of a single link type, the combustion load acting downward on the piston acts on the bearing portion of the crankshaft in the same direction, that is, downward, via a single connecting rod. In the link type piston-crank mechanism, a combustion load acting downward on the piston is converted into an upward force by the U-shaped link row and acts on the bearing portion of the crankshaft.

  The present invention has been made in view of such circumstances. That is, the multi-link type piston-crank mechanism for an internal combustion engine according to the present invention is supported by the engine stationary body, the crankshaft rotatably supported by the engine stationary body, and disposed parallel to the crankshaft. A support shaft, a rocker arm that is swingably attached to the support shaft, a first link rotatably connected to the piston via a piston pin, and connecting the piston and one end of the rocker arm; A second link that connects the other end and a crankpin that is eccentrically provided on the crankshaft. The axis of the support shaft is disposed between the axis of the piston pin and the axis of the crankshaft in the engine width direction, and is lower than the axis of the piston pin and the axis of the crankshaft in the engine vertical direction. Is arranged.

  In this way, depending on the layout, the link row consisting of the rocker arm, the first link and the second link is formed into an upward channel shape / U shape, and the cylinder and crankshaft are positioned above the support shaft and the rocker arm. A layout arranged side by side in the direction can be realized. Therefore, it is possible to shorten the vertical dimension of the engine as compared with the conventional internal combustion engine using a single link type piston-crank mechanism, in which the crankshaft is arranged below the cylinder, and the vehicle mounting property is reduced. Can be improved.

  In the multi-link type piston-crank mechanism having such a layout, a downward combustion load acting on the piston acts in the same direction, that is, downward, on the bearing portion of the support shaft to which the rocker arm is attached via the first link. The bearing portion of the crankshaft acts as a force in the opposite direction, that is, upward, via the first link, the rocker arm, and the second link.

  Therefore, in the present invention, a support shaft cap, a support shaft bolt for fixing the support shaft cap to the engine fixed body with the support shaft interposed therebetween so as to support the support shaft on the engine fixed body side, and a crankshaft And a crankshaft bolt for fixing the crankshaft cap to the engine stationary body with the crankshaft interposed therebetween so as to rotatably support the crankshaft on the engine stationary body side, and the support shaft. The cap for the crankshaft is disposed on the engine lower side of the support shaft, and the crankshaft cap is disposed on the engine upper side of the crankshaft.

  With such a configuration, when a large downward combustion load acts on the piston, a downward load acts on the bearing portion of the support shaft via the first link and the rocker arm. The support shaft cap is disposed in the same direction as the direction of the load. Similarly, an upward load acts on the bearing portion of the crankshaft via the first link, the rocker arm, and the second link. The crankshaft cap is disposed in the same direction as the direction of application of the load so as to face the load. Therefore, it is possible to effectively improve the support rigidity against the load in the bearing portions of the support shaft and the crankshaft.

  For the support shaft located on the lower side of the engine, the cap for the support shaft is attached from the lower side of the engine, and for the crankshaft located on the lower side of the engine, the cap for the crankshaft is mounted on the upper side of the engine. Since it is attached from the side, operations such as assembly and fastening of caps and bolts can be easily performed.

  Specifically, on the support shaft side provided at the lower part of the engine solid body, the support shaft bolt is configured to be inserted from the engine lower side which is the open side, and on the crankshaft side provided at the upper part of the engine fixed body, By configuring the crankshaft bolt to be inserted from the engine upper side, which is the open side, tools such as a box wrench and nutrunner used for tightening the bolt can be easily mounted and inserted into the bolt head. In addition, the screw engagement portion between each bolt and the engine stationary body is arranged on the side opposite to the input direction of the combustion load acting on the bearing portion, that is, the screw engagement in the input direction of the combustion load. Since this is not set, the strength of the screw engagement portion is improved.

  As described above, according to the present invention, by arranging the crankshaft on the side of the piston or cylinder, the overall engine height of the internal combustion engine can be suppressed to be low, and the engine mountability can be improved. In the multi-link type piston-crank mechanism that realizes the layout, the support rigidity of the bearing portions of the crankshaft and the support shaft is improved by optimizing the arrangement of the caps and bolts used in the bearing portions of the crankshaft and the support shaft. be able to.

1 is a cross-sectional view showing a multi-link piston-crank mechanism of an internal combustion engine according to a first embodiment of the present invention. Explanatory drawing which projected the water jacket around a cylinder and the bolt for support shafts on the cross section orthogonal to a cylinder axial direction. (A1) is an explanatory diagram in which a water jacket and a support shaft bolt around the cylinder according to the first reference example are projected on a cross section orthogonal to the cylinder axial direction, and (A2) exaggerates the cylinder bore deformation of the first reference example. (B1) is an explanatory diagram in which the water jacket and the support shaft bolt around the cylinder according to the second reference example are projected on a cross section perpendicular to the cylinder axial direction, (B2) is the first reference example. Explanatory drawing which exaggerates and shows a cylinder bore deformation | transformation. FIG. 9 is a cross-sectional view showing a multi-link piston-crank mechanism for an internal combustion engine according to a second embodiment of the present invention. FIG. 9 is a cross-sectional view showing a multi-link piston-crank mechanism for an internal combustion engine according to a third embodiment of the present invention. Sectional drawing which shows the basic composition of the multiple link type piston-crank mechanism which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 6, in this specification, the direction along the axial direction 6A of the cylinder 6 (vertical direction in the figure) is called the engine vertical direction Fh, the piston top dead center side is “up”, and the piston bottom The dead point side is “down”. The axial direction of the crankshaft 4, that is, the cylinder row direction (direction orthogonal to the drawing sheet) is called the engine longitudinal direction Fl, and the thrust of the piston 3 orthogonal to both the engine vertical direction Fh and the engine longitudinal direction Fl The anti-thrust direction (the left-right direction in the figure) is called the engine width direction Fb.

  First, the basic configuration of the multi-link piston-crank mechanism 30 in the reciprocating internal combustion engine will be described with reference to FIG. The basic configuration of the piston-crank mechanism 30 is known as described in the above Japanese Patent Laid-Open No. 2006-52667.

  The engine fixed body of the internal combustion engine E is composed of a cylinder block 21, a cylinder head 8, and the like. A plurality of cylinders 6 are formed in the cylinder block 21 along the cylinder row direction Fl, and a piston 3 is provided in each cylinder 6. Are slidably fitted. A cylinder head 8 is fixed to the upper surface of the cylinder block 21 so as to cover the upper surface of the cylinder 6, and a pent roof type defining a combustion chamber 22 between the lower surface of the cylinder head 8 and the upper surface of the piston 3. The combustion chamber 22 is formed. A head cover 23 that rotatably supports the intake camshaft 9I and the exhaust camshaft 9E together with the cylinder head 8 is fixed to the upper surface of the cylinder head 8. The cylinder head 8 is formed with an intake port 24I and an exhaust port 24E that are connected to the combustion chamber 22. An internal passage communicating with the exhaust port 24E is formed in the exhaust manifold 25E attached to the side surface of the cylinder head 8. An oil pan 26 that receives and stores the lubricating oil is attached to the lower surface of the cylinder block 21.

  The multi-link type piston-crank mechanism 30 mechanically links the piston 3 and the crankpin 5 of the crankshaft 4 to convert the reciprocating linear motion of the piston 3 in the cylinder 6 into the rotational motion of the crankshaft 4. In particular, it has a multi-link configuration in which the piston 3 and the crankpin 5 are linked by a plurality of links.

  The multi-link piston-crank mechanism 30 includes a crankshaft 4 that is rotatably supported by the cylinder block 21, a support shaft 41 that is rotatably supported by the cylinder block 21 in parallel with the crankshaft 4, and the support A rocker arm 31 that is swingably attached to an eccentric shaft portion 42 that is eccentrically provided on the shaft 41, a first link 32 that connects one end of the rocker arm 31 and the piston 3, the other end of the rocker arm 31, and the crankshaft 4 And a second link 33 connecting the crankpin 5. The piston 3 and the upper end of the first link 32 are connected by a piston pin 34 so as to be relatively rotatable. The lower end of the first link 32 and one end of the rocker arm 31 are connected to each other by a first connecting pin 35 so as to be relatively rotatable. The other end of the rocker arm 31 and the lower end of the second link 33 are connected by a second connecting pin 36 so as to be relatively rotatable.

  The multi-link type piston-crank mechanism 30 changes the rotational position of the support shaft 41 so that the shaft center of the eccentric shaft portion 42 that becomes the rocking fulcrum 1 of the rocker arm 31 is fixed to the engine stationary body such as the cylinder block 21. Thus, it has variable compression ratio means for continuously changing the stroke characteristics of the piston 3 and the engine compression ratio by being displaced, that is, it is configured as a variable compression ratio mechanism that makes the engine compression ratio variable. This variable compression ratio means has a support shaft 41 extending in the cylinder row direction Fl in parallel with the crankshaft 4 and a plurality of eccentric shaft portions 42 provided eccentrically to the support shaft 41 corresponding to each cylinder 6. doing. A central portion of the rocker arm 31 is swingably attached to the circular outer peripheral surface of each eccentric shaft portion 42. Therefore, the rocker arm 31 can swing about the axis of the eccentric shaft portion 42 as the fulcrum 1. By changing the rotation position of the support shaft 41, the position of the rocking fulcrum 1 of the rocker arm 31 is displaced, and the engine compression ratio is changed. The rotational position of the support shaft 41 is changed and held by a variable compression ratio actuator 43 such as an electric type or a hydraulic type. The operation of the variable compression ratio actuator 43 is controlled by a control signal output from the engine control unit 44 according to engine operating conditions such as engine load and engine speed.

  Next, a specific embodiment of the multi-link piston-crank mechanism according to the present invention will be described with reference to FIGS. The multi-link type piston-crank mechanism 30 shown in FIGS. 1, 4 and 5 is basically the same as that shown in FIG. 1, and a specific configuration is not shown. On the other hand, the cylinder head 8 fixed to the upper part of the cylinder block 21 is miniaturized in the vicinity of the upper part of the cylinder 6 on the left side of the drawing, and the crankshaft is located on the right upper part of the cylinder block 21 where the cylinder head 8 is omitted. A block cover 37 having a large upper part 4 is attached. Above the block cover 37, an intake manifold 25 </ b> I attached to the side wall on the intake side of the cylinder head 8 is disposed.

  First, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the shaft center 41A of the support shaft 41 rotates in the engine width direction Fb toward the shaft center 34A of the piston pin 34 and the shaft center 4A of the crankshaft 4, more specifically to the cylinder block 21 side. It is arranged between the axial center 4A of the crank journal part that is supported, and is arranged below the axial center 34A of the piston pin 34 and the axial center 4A of the crankshaft 4 in the engine vertical direction Fh. Yes. As a result, as shown by the broken link line in FIG. 1, the link row composed of the rocker arm 31 and the first link 32 and the second link 33 connected to both sides thereof forms an upward channel shape / U shape, In the layout, the cylinder 6 into which the piston 3 is fitted and the crankshaft 4 are arranged in parallel in the engine width direction obliquely above the rocker arm 31 attached to the support shaft 41.

  Therefore, compared to a general internal combustion engine having a single link type piston-crank mechanism, in which the crankshaft is disposed below the cylinder, the overall height of the engine is suppressed and the vehicle mountability is improved. be able to. Further, according to such a configuration of the link row, the posture of the first link 32 connected to the piston 3 (see FIG. 1) is relatively along the cylinder axial direction 6A as compared with the single link mechanism, and the cylinder Since the inclination with respect to the axial direction 6A is suppressed, the thrust-anti-thrust load in the engine width direction Fb due to the combustion load or the like can be significantly suppressed.

  As a configuration in which the support shaft 41 is rotatably supported on the lower surface side of the cylinder block 21, a support shaft cap 51 as a bearing cap and each support shaft cap 51 are fastened and fixed to the cylinder block 21 with the support shaft 41 interposed therebetween. A pair of support shaft bolts 52 (52A, 52B) are provided, and the support shaft 41 is rotatably supported on the upper surface of the support shaft cap 51 and the lower surface of the cylinder block 21, which serve as mating surfaces. A half-shaped bearing surface 53 is recessed.

  Similarly, the crankshaft 4 is rotatably supported on the upper surface side of the cylinder block 21, and a crankshaft cap 54 as a bearing cap and each crankshaft cap 54 sandwiched between the crankshafts 4 are attached to the cylinder block 21. A pair of crankshaft bolts 55 (55A, 55B) to be fixed are provided, and the crankshaft 4 can be rotated on the lower surface of the crankshaft cap 54 and the upper surface of the cylinder block 21 as the mating surfaces. A half-shaped bearing surface 56 to be supported is recessed.

  Here, in the layout of the link row (31, 32, 33) having the upward channel shape / U shape as described above, as shown in FIG. 1, the largest load acting on this link row is the piston. When a combustion load F0 is applied to the piston near the top dead center, a downward load F1, which is the same direction, acts on the bearing portion of the support shaft 41 via the first link 32 and the rocker arm 31, and the crankshaft The upward load F <b> 2, which is the reverse direction, acts on the bearing portion 4 via the first link, the rocker arm 31, and the second link 33.

  In this embodiment, with respect to the downward load F1 to the bearing portion of the support shaft 41, the support shaft cap 51 is disposed on the engine lower side of the support shaft 41 so as to face the load F1, that is, It is configured to be mounted on the lower surface of the cylinder block 21 from the lower side of the engine. A pair of support shaft bolts 52 positioned on both sides of the support shaft 41 in the engine width direction are inserted through the support shaft cap 51 from the lower side of the engine, and a male screw portion at the tip is formed in the bolt hole of the cylinder block 21. The support shaft 41 is interposed between the cylinder block 21 and the head portion 57 of the bolt 52 seated on the lower surface of the support shaft cap 51 in a state where the support shaft 41 is rotatably sandwiched by the female screw portion. The cap 51 is securely fastened together.

  Thus, the support shaft cap 51 is mounted on the cylinder block 21 from the same direction (downward) as the input direction of the load F1 so as to face the input direction (downward) of the maximum load F1. The support rigidity for the maximum load F1 can be effectively improved. Further, the support shaft bolt 52 is inserted in an upward direction opposite to the input direction of the load F1, and the screw engagement portion between the tip of the bolt 52 and the cylinder block 21 is opposite to the input direction of the load F1. Since it is set at a certain upper side, the support rigidity by the bolt 52 is further improved, and stress concentration on the screw meshing portion can be suppressed / avoided.

  Further, since the support shaft cap 51 and the support shaft bolt 52 are assembled to the lower surface of the cylinder block 21 from the lower side of the cylinder block 21 that is largely open, the assembly work is easy to assemble. Excellent workability. In particular, it is easy to assemble and insert tools used for tightening the bolts 52, specifically, tools such as a cylindrical box wrench and a nut runner fitted to the bolt head 57.

  Similarly, with respect to the upward load F2 to the bearing portion of the crankshaft 4, in the present embodiment, the crankshaft cap 54 is disposed on the engine upper side of the crankshaft 4 so as to face the load F2, that is, It is configured to be mounted on the upper surface side of the cylinder block 21 from the upper side of the engine. The pair of crankshaft bolts 55 located on both sides of the crankshaft 4 in the engine width direction are inserted through the crankshaft cap 54 from the upper side of the engine, and the male thread portion at the tip is formed in the bolt hole of the cylinder block 21. The crankshaft 4 is clamped between the cylinder block 21 and the head 58 of the bolt 55 seated on the upper surface of the crankshaft cap 54 with the crankshaft 4 being rotatably sandwiched by being tightened to the female screw portion. The shaft cap 54 is firmly fixed together.

  Thus, the crankshaft cap 54 is mounted on the cylinder block 21 from the same direction (upward) as the input direction of the load F2 so as to face the input direction (upward direction) of the maximum load F2. The support rigidity with respect to the maximum load F2 can be effectively improved. Further, the crankshaft bolt 55 is inserted in a downward direction opposite to the input direction of the load F2, and the screw engagement portion between the tip of the bolt 55 and the cylinder block 21 is opposite to the input direction of the load F2. Since it is set to a certain upper side, the support rigidity by the bolt 55 is further improved, and stress concentration on the screw meshing portion can be suppressed / avoided.

  Furthermore, since the crankshaft cap 54 and the crankshaft bolt 55 are assembled to the upper surface of the cylinder block 21 from the upper side of the cylinder block 21 that is largely open, the assembling work becomes easy and the assembling workability is improved. Are better. In particular, it is easy to assemble / insert a tool used when tightening the bolt 55, specifically, a tool such as a cylindrical box wrench or a nut runner fitted to the bolt head 58.

  Next, the positional relationship between the water jacket 59 formed around the cylinder 6 through which the cooling water circulates and the support shaft bolt 52 will be described with reference to FIGS. 2 and 3 (A1), (B1) show the water jacket 59 and the support shaft bolt 52 (and their bolt holes) in a cross section along the line AA in FIG. 1 orthogonal to the cylinder axial direction 6A. It is explanatory drawing which projected. FIG. 2 shows the layout of this embodiment. As shown in FIG. 2, in this embodiment, a pair of support shafts for each support shaft cap 51 when projected onto a cross section orthogonal to the cylinder axial direction 6A. Both of the bolts 52 for use are arranged on the same side (the lower side in the figure) with respect to the cylinder 6, and all the support shaft bolts 52 and the water jacket 59 are arranged at different positions without overlapping. Has been. That is, the water jacket 59 and the support shaft bolt 52A close to the cylinder are arranged at positions separated from each other by a predetermined distance D1 when viewed in the cylinder axial direction.

  3A1 shows a first reference example in which bolts 52 (support shaft bolts or crankshaft bolts) are arranged on both sides of the cylinder 6 in the engine width direction when projected onto a cross section orthogonal to the cylinder axial direction 6A. Shows the layout. Further, in the second reference example of FIG. 3 (B1), when projected onto a cross section orthogonal to the cylinder axial direction 6A, a pair of support shaft bolts 52 (52A, 52B) is connected to the cylinder 6 as in the present embodiment. However, the present embodiment is different from the present embodiment in that the support shaft bolt 52A near the cylinder and a part of the water jacket 59 overlap each other.

  3 (A2) and 3 (B2) exaggerate the deformation mode of the cylinder 6 caused by the bolt fastening load and the like in the first and second reference examples, respectively, and the cylinder outer diameter after the deformation is represented by a thick line. ing. When the pair of support shaft bolts 52 are disposed on the same side with respect to the cylinder 6 as in the second reference example, the pair of bolts 52 are disposed on both sides in the engine width direction of the cylinder 6 as compared with the first reference example. Thus, as exaggeratedly drawn by the solid line α1 in FIG. 3 (B2), the load is concentrated on the side where the bolt 52 is arranged, and the deformation of the cylinder 6 increases, and the roundness of the cylinder 6 deteriorates. There is a problem that problems such as an increase in oil consumption and an increase in blow-by gas occur. In particular, as in the second reference example, when the water jacket 59 and the bolt 52 overlap when viewed in the cylinder axial direction, stress is concentrated at the screw meshing portion at the tip of the bolt 52 that overlaps with the water jacket 59. At the same time, the stress amplitude increases, and the cylinder bore tends to be deformed.

  In order to deal with such a problem, in this embodiment, since the support shaft bolt 52 is disposed away from the water jacket 59, the screw engagement portion at the tip of the bolt 52 is compared with the second reference example. As shown by the one-dot chain line α2 in FIG. 3 (B2), the stress concentration and the increase in the stress amplitude are suppressed, the deformation of the cylinder 6 is greatly suppressed, the roundness is improved, the oil consumption is increased and the blow-by is increased. An increase in the amount of gas can be suppressed.

  Further, as shown in FIG. 1, the bolt head portion 58 of the crankshaft bolt 55 seated on the upper surface of the crankshaft cap 54 has an engine more than the upper surface of the cylinder block 21 in which the cylinder 6 is formed, that is, the top deck surface 61. It is arranged on the upper side. In particular, in this embodiment, for the purpose of weight reduction and compactness, the upper surface 62 on the crankshaft side to which the crankshaft cap 54 is fixed is lower than the top deck surface 61 on the cylinder side. In spite of being located, the bolt head 58 is arranged on the engine upper side than the top deck surface 61 by interposing the crankshaft cap 54. By disposing the bolt head 58 above the top deck surface 61 in this way, it becomes easier to mount and insert a tool used during bolt tightening, and the assembly workability is further improved.

  FIG. 4 shows a multi-link type piston-crank mechanism according to a second embodiment of the present invention. In the following description of the embodiments, descriptions overlapping with those of the first embodiment will be omitted as appropriate, and differences from the first embodiment will be mainly described.

  In the second embodiment, when projected onto a cross section orthogonal to the cylinder axial direction 6A, at least a part of the support shaft bolt 52B near the crankshaft and the crankshaft bolt 55A near the support shaft are partially provided. It is set to overlap. That is, the two bolts 52B are arranged on substantially the same line along the cylinder axial direction 6A. In particular, in this embodiment, the two bolts 52B and 55A are completely arranged on the same line along the cylinder axial direction 6A. Yes. Thus, by arranging the support shaft bolt 52 and the crankshaft bolt 55 on the same line along the cylinder axial direction 6A or in the vicinity thereof, the shear load generated between them can be eliminated and suppressed. The strength of the fastening portion can be further improved.

  In the second embodiment, of the pair of support shaft bolts 52, the support shaft bolt 52A adjacent to the cylinder 6 is extended to the axial height position where the water jacket 59 around the cylinder 6 exists. In other words, the support shaft bolt 52 and the water jacket 59 near the cylinder are partially overlapped by a predetermined distance D2 in the cylinder axial direction, and the support shaft bolt 52 and the water jacket 59 are It is separated by a predetermined distance D3.

  In this way, the support shaft bolt 52A closer to the cylinder is extended to improve rigidity and strength, and at the tip of the bolt 52A that overlaps the water jacket 59 in the cylinder axial direction, Due to the space, it is possible to block the load input input from the bolt side from being transmitted to the cylinder 6 side, and to suppress the deformation of the cylinder bore.

  FIG. 5 shows a multi-link piston-crank mechanism according to a third embodiment of the present invention. In the third embodiment, the support shaft bolt near the crankshaft and the crankshaft bolt near the support shaft are configured as one common bolt 63. In this embodiment, the common bolt 63 is inserted from the lower side of the engine, passes through the support shaft cap 51 and the cylinder block 21, and is inserted into the crankshaft cap 54. Are fastened to the female thread portion formed in the bolt hole of the crankshaft cap 54, so that both the support shaft cap 51 and the crankshaft cap 54 are fastened and fixed to the cylinder block 21 together.

  As described above, the supporting shaft bolt and the crankshaft bolt are constituted by the single common bolt 63, so that the number of parts is reduced and the number of assembling steps is reduced. Similarly to the second embodiment, the supporting shaft The bolts for the crankshaft and the bolts for the crankshaft can be more surely arranged on the same line, so that the shearing load can be eliminated and the strength of the bolt fastening portion can be improved.

  As a bolt fastening method, a nut may be fastened to the tip of the bolt 63 protruding upward from the upper crankshaft cap 54. Further, the common bolt 63 is inserted from the lower side of the engine, but may be inserted from the upper side of the engine.

  Further, in the above embodiment, the present invention is applied to a multi-link type piston-crank mechanism in which the engine compression ratio can be changed. However, the multi-link type piston not having such a function of changing the engine compression ratio. It is also possible to apply the present invention to a crank mechanism. In this case, the support shaft may be configured to be non-rotatably supported by an engine stationary body such as a cylinder block.

DESCRIPTION OF SYMBOLS 3 ... Piston 4 ... Crankshaft 5 ... Crankpin 6 ... Cylinder 8 ... Cylinder head 30 ... Piston-crank mechanism 31 ... Rocker arm 32 ... 1st link 33 ... 2nd link 41 ... Support shaft 51 ... Support shaft cap 52 ... Support Bolt for shaft 54 ... Cap for crankshaft 55 ... Bolt for crankshaft 59 ... Water jacket 63 ... Common bolt

Claims (9)

A crankshaft rotatably supported by the engine stationary body;
A support shaft disposed in parallel with the crankshaft and supported by the engine stationary body;
A rocker arm swingably attached to the support shaft;
A first link rotatably connected to the piston via a piston pin and connecting the piston and one end of the rocker arm;
A second link connecting the other end of the rocker arm and a crank pin provided eccentric to the crankshaft,
The axis of the support shaft is disposed between the axis of the piston pin and the axis of the crankshaft in the engine width direction, and is below the axis of the piston pin and the axis of the crankshaft in the engine vertical direction. In the double-link type piston-crank mechanism of the internal combustion engine disposed in
A support shaft cap;
A support shaft bolt for fixing the support shaft cap to the engine fixed body with the support shaft interposed therebetween so as to support the support shaft on the engine fixed body side;
A crankshaft cap;
A crankshaft bolt for fixing the crankshaft cap to the engine stationary body with the crankshaft interposed therebetween so as to rotatably support the crankshaft on the engine stationary body side,
A multi-link piston-crank mechanism for an internal combustion engine, wherein the support shaft cap is disposed on an engine lower side of the support shaft, and the crank shaft cap is disposed on an engine upper side of the crank shaft. The support shaft bolt is fixed to the engine fixed body by inserting the support shaft cap from the lower side of the engine.
2. The multi-link piston-crank mechanism for an internal combustion engine according to claim 1, wherein the crankshaft bolt is fixed to the engine stationary body through the crankshaft cap from above the engine.   When the support shaft bolt and the water jacket formed around the cylinder are projected on a cross section orthogonal to the cylinder axial direction, the support shaft bolt and the water jacket are not in an overlapping position. The multi-link type piston-crank mechanism for an internal combustion engine according to claim 1 or 2, characterized in that it is arranged.   When the support shaft bolt and the crankshaft bolt are projected on a cross section orthogonal to the cylinder axis direction, at least a part of the support shaft bolt and the crankshaft bolt is set to overlap. The multi-link type piston-crank mechanism for an internal combustion engine according to any one of claims 1 to 3.   The multi-link type piston for an internal combustion engine according to any one of claims 1 to 4, wherein the support shaft bolt and the crankshaft bolt are arranged on the same line along the cylinder axial direction. -Crank mechanism.   6. The multi-link piston-crank mechanism for an internal combustion engine according to claim 1, wherein the support shaft bolt and the crankshaft bolt are constituted by the same common bolt. . The crankshaft bolt is inserted through the crankshaft cap from the upper side of the engine and fixed to the engine stationary body,
The bolt head of a crankshaft bolt seated on the upper surface of the crankshaft cap is disposed above the engine on the upper side of the cylinder block on which the cylinder is formed. A double link type piston-crank mechanism for an internal combustion engine according to any one of the above. The support shaft bolt is fixed to the engine fixing body by inserting the support shaft cap from the lower side of the engine.
The upper end of the support shaft bolt having a screw-engaging portion with the engine stationary body side and the lower end of the water jacket formed around the cylinder partially overlap in the cylinder axial direction. The multi-link type piston-crank mechanism for an internal combustion engine according to any one of claims 1 to 7. The rocker arm is rotatably attached to an eccentric shaft provided eccentric to the support shaft;
9. A variable compression ratio means capable of changing the engine compression ratio with a change in piston stroke characteristics by changing the rotational position of the support shaft. The double-link type piston-crank mechanism of the internal combustion engine.

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