JP2004124777A - Link assembly parts for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce weight, to aim at miniaturization, and to effectively reduce the tensile stress to be applied to a thin part. <P>SOLUTION: A lower link 13 is provided with a crank pin bearing body 21 having a nearly cylindrical crank pin bearing part 32, connector pin bearing parts 22 and 23 having connector pin bearing parts 41 and 42, to which connector pins are inserted. A thin part of a central connection part 30, which is projected outward in the radial direction from a central part in the axial direction of the crank pin bearing part 32, crossing between the connector pin bearing part 41 and the crank pin bearing part 32 is partially formed thin in the radial direction. Near this thin part, the predetermined clearance ΔCL is provided between a boss part 50 of the central connection part 30 and bolt abutting surfaces 103 and 104 of the connector pin bearing members 22 and 23, which are fastened together for fixation by a bolt 54 in a direction crossing the shaft. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a link assembly for rotatably supporting a crankpin of an internal combustion engine, and more particularly to an improvement of a link assembly suitable as a lower link of a multiple link variable compression ratio mechanism.
[0002]
[Prior art]
In the field of reciprocating internal combustion engines, various types of variable compression ratio mechanisms that can change the compression ratio have been proposed in order to optimize the compression ratio in accordance with the operating state of the engine. As one of them, Japanese Patent Application Laid-Open No. 2000-73804 describes a multi-link type variable compression ratio mechanism in which a piston and a crankshaft are linked by a plurality of links. Briefly describing this, one end of an upper link is connected to a piston disposed in the cylinder via a piston pin. The other end of the upper link is connected to the lower link via a first connection pin. The lower link is rotatably attached to a crankpin of a crankshaft. One end of the control link is connected to the lower link via a second connection pin. The other end of the control link is swingably attached to an eccentric cam of the control shaft. Therefore, when the control shaft is driven to rotate by a motor or the like in accordance with the operating state of the engine, the position of the support point of the control link including the eccentric cam changes. As a result, the motion constraint condition of the lower link by the control link changes, so that the piston top dead center position and, consequently, the engine compression ratio change.
[0003]
The lower link is divided into a main body and a cap with the crank pin interposed therebetween so that the lower link can be later assembled to the crank pin, and the main body and the cap are connected by bolts. The main body has a first connection pin bearing portion through which the first connection pin passes and a second connection pin bearing portion through which the second connection pin passes. On the other hand, the cylindrical crankpin bearing portion is formed by being divided into a main body and a cap portion. Each connection pin bearing has a bifurcated shape so as to support each connection pin on both sides in the axial direction.
[0004]
[Problems to be solved by the invention]
A link assembly such as the lower link described above is required to be effectively reduced in weight and size and to be effectively improved in strength.
[0005]
In particular, in the lower link of the variable compression ratio mechanism described in the above publication, an input load acting from the upper link or the control link is applied to the lower link crank pin bearing via the first and second connecting pins. Act on At this time, the load tends to concentrate on a portion of the lower link crank pin bearing portion facing the connecting pin bearing portion. In particular, since a load acts directly on the axial end of the crankpin bearing from each of the pair of bifurcated connecting pin bearings, the axial end of the crankpin bearing is largely deformed. The crankpin bearing is a sliding bearing that mainly supports a load with a fluid lubricating film. In such a sliding bearing, the oil film pressure is highest at the axial center, and the oil film pressure is low because the pressure is released at the axial end. Therefore, when the axial end of the cylindrical crankpin bearing is deformed as described above, it cannot be supported by the oil film pressure, and direct contact between the axial end and the outer peripheral surface of the crankpin occurs. However, there is a problem that wear and friction increase.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and has as its main object to provide a novel link assembly for an internal combustion engine capable of effectively improving strength while reducing weight and size. .
[0007]
[Means for Solving the Problems]
A link assembly according to the present invention includes a crankpin bearing having a substantially cylindrical crankpin bearing through which a crankpin is inserted, and a connecting pin bearing having a connecting pin bearing through which a connecting pin for connecting another link is inserted. And a member. The crankpin bearing body has a central connecting portion projecting radially outward from an axially central portion of the crankpin bearing portion, and the central connecting portion is formed between the connecting pin bearing portion and the crankpin bearing portion. The thin portion crossing the gap is partially reduced in the radial direction. Further, a fixing means for fixing the central connecting portion and the crankpin bearing portion at a plurality of locations around the crankpin bearing portion is provided, and the fixing means is closer to the thinner portion than the central connecting portion in the axial direction. The connecting pin bearing member has a bolt that fastens and fixes the boss portion that protrudes to the connecting pin bearing member in a direction perpendicular to the axis. Further, a predetermined clearance is provided between the bolt mating surfaces of the boss portion and the connecting pin bearing member, which are fastened together by the bolt.
[0008]
Such a link assembly is suitably used as a lower link of a multiple link type variable compression ratio mechanism. This variable compression ratio mechanism has, for example, an upper link having one end connected to a piston via a piston pin, and the other end of the upper link connected via a first connection pin. A lower link rotatably mounted, a control link having one end connected to the lower link via a second connecting pin, and the other end swingably supported with respect to the internal combustion engine body; And a support position changing means for displacing the position of the other end of the control link with respect to the internal combustion engine body when changing.
[0009]
【The invention's effect】
According to the present invention, since the clearance is provided between the boss portion of the crankpin bearing body connected by the bolt and the bolt mating surface of the connection pin bearing member, when the bolt is tightened, the center located near the bolt is located. A strong compressive force can be applied to the thin portion of the connecting portion. Therefore, for example, when a strong tensile force acts on the thin-walled portion due to the load acting on the connecting pin, the force can be effectively canceled out, and the maximum value of the tensile stress can be reduced. The strength can be effectively improved while achieving weight reduction and compactness by reducing the thickness of the device.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a variable compression ratio mechanism of an internal combustion engine to which a lower link as a link assembly component according to the present invention is applied. The piston 1 is slidably disposed in a cylinder 6 formed in the cylinder block 5. One end of an upper link 11 is swingably connected to the piston 1 via a piston pin 2. The other end of the upper link 11 is swingably connected to the lower link 13 via the first connection pin 12. The lower link 13 is a link assembly component rotatably attached to the outer periphery of the crankpin 4 of the crankshaft 3. Piston 1 receives combustion pressure from a combustion chamber defined above it. The crankshaft 3 is rotatably attached to the cylinder block 5 by a crank bearing bracket 7.
[0011]
One end of a control link 15 is swingably connected to the lower link 13 via a second connection pin 14. The other end (support center) 16 of the control link 15 is supported by a cylinder block 5 which is an engine body as a fixed body. Displaced with respect to
[0012]
The support position changing means 17 has a control shaft 18 that is driven to rotate around the axis when the compression ratio is changed, and a circular control cam 19 eccentrically fixed to the control shaft 18. . The other end 16 of the control link 15 is rotatably mounted on the outer periphery of the control cam 19. The control shaft 18 extends in the cylinder row direction in parallel with the crankshaft 3, and is rotatably supported by the crank bearing bracket 7 and the control bearing bracket 8.
[0013]
Therefore, when the control shaft 18 is driven to rotate by an actuator (not shown) or the like at the time of changing the compression ratio, the axial center position of the control cam 19 serving as the support center 16 of the control link 15 moves relative to the engine body. As a result, the motion constraint condition of the lower link 13 by the control link 15 changes, the stroke stroke of the piston 1 with respect to the crank angle changes, and the engine compression ratio changes.
[0014]
2 to 5 show the structure of the lower link 13 according to the first embodiment of the present invention. The lower link 13 includes a crankpin bearing 21 that rotatably supports the crankpin 4, a pair of connecting pin bearing members 22 and 23 that rotatably supports the first connecting pin 12 and the second connecting pin 14, It consists of. The crankpin bearing 21 and the connecting pin bearing members 22 and 23 are connected to each other by a first bolt 26, a pair of second bolts 54 and a pair of third bolts 55, and a crankpin is formed by the connecting pin bearing members 22 and 23. The bearing 21 is fastened and fixed while being sandwiched in the crankpin axial direction.
[0015]
As shown in FIGS. 2 and 5, the crankpin bearing 21 has a substantially cylindrical crankpin bearing 32 through which the crankpin 4 is inserted. It is divided by a pair of divided members 36 and 37 abutting on a bearing mating surface 35 passing through the center. That is, the crankpin bearing body 21 is composed of a pair of divided members 36 and 37 that are bolt-connected with the crankpin 4 interposed therebetween so that the crankpin bearing body 21 can be assembled to the crankpin 4 later. Therefore, the crankpin bearing portion 32 is also constituted by a pair of semi-cylindrical portions abutting each other on the bearing mating surface 35, and one of the semi-cylindrical portions corresponds to the first divided member 36 and the other corresponds to the second divided member 37. Is formed.
[0016]
The crankpin bearing portion 32 has a central connecting portion 30 that protrudes radially outward from the axial center portion of the crankpin bearing portion 32 and surrounds the crankpin bearing portion 32 in an annular shape. The center connecting portion 30 has a substantially thin plate shape having a constant thickness in the axial direction of the crankpin. In other words, the cylindrical crankpin bearing portion 32 that annularly surrounds the crankpin bearing surface 31 is formed so as to protrude from the center connecting portion 30 to both sides in the axial direction in order to secure bearing strength.
[0017]
The connecting pin bearing members 22 and 23 are plate-like members having substantially similar shapes with the crank pin bearing body 21 interposed therebetween. The connection pin bearing members 22 and 23 are formed with a first connection pin bearing portion 41 through which the first connection pin 12 is inserted and a second connection pin bearing portion 42 through which the second connection pin 14 is inserted, respectively. I have. The connecting pin bearing members 22 and 23 have a substantially U-shaped primary cutout surface 43 for avoiding interference and contact with the crankpin 4. Each primary notch surface 43 is formed with a secondary notch surface 44, which is cut deeper than the primary notch surface 43, in a stepped shape in order to avoid interference and contact with the crankpin bearing portion 32.
[0018]
Bolt through holes 47a and screw holes 47b for the first bolts 26 are formed in the connection pin bearing members 22 and 23 between the connection pin bearing portions 41 and 42. The first bolt 26 axially passes through a bolt through hole 47a formed in one of the connecting pin bearing members 22 and a bolt through hole 39 formed in the first split member 36 of the crankpin bearing body 21. Then, it is screwed into a screw hole 47b formed in the other connecting pin bearing member 22, thereby fixing the two connecting pin bearing members 22 and 23 together in the axial direction with the first divided member 36 interposed therebetween. I have.
[0019]
The four bolts 54 and 55 fasten the second divided member 37 of the crankpin bearing body 21 and the connecting pin bearing members 22 and 23. These bolts 54 and 55 are arranged so that the center line thereof crosses the bearing mating surface 35, more specifically, the bearing mating surface so that a strong compressive force acts on the bearing mating surfaces 35 of the divided members 36 and 37. The dual-purpose bolt is set so as to extend along a direction substantially perpendicular to 35 and has a function of substantially coupling the first divided member 36 and the second divided member 37 together. Corresponding to the bolts 54 and 55, a boss portion 50 for a bolt is formed in the central connecting portion 30 of the second divided member 37 so as to partially protrude in the axial direction, and a bolt hole 51 penetrates each boss portion 50. The connecting pin bearing members 22 and 23 are formed with screw holes 53 (see FIG. 3).
[0020]
When assembling the lower link 13, first, a part (semi-circular arc portion) of the bearing surface 31 formed on the first divided member 36 and the substantially U-shaped cutout surfaces 43 and 44 of the connecting pin bearing members 22 and 23. Are opened in the same direction, and the first divided member 36 and the connecting pin bearing members 22 and 23 are temporarily fixed as an intermediate assembly by the first bolt 26 described above. Next, after the intermediate assembly and the second divided member 37 are abutted on the bearing mating surface 35 with the crank pin 4 interposed therebetween, the above-described bolts 54 and 55 may be fastened, and the assembling workability is excellent. . By tightening the bolts 54 and 55 in this manner, the second divided member 37 is fixed to the connecting pin bearing members 22 and 23, and the first divided member 36 and the first divided member 36 fixed to the connecting pin bearing members 22 and 23 are fixed. A strong compressive force acts on the bearing mating surface 35 with the two split members 37, and these split members 36 and 37 are firmly joined at the bearing mating surface 35.
[0021]
As shown in FIG. 4A, a second bolt 54 and a third bolt 55 are provided on both sides of the crankpin bearing surface 31 for each of the connecting pin bearing members 22 and 23 when viewed in the crankpin axial direction. The bolts 54 and 55 and the first bolt 26 are disposed so as to surround the crankpin bearing 32 in a triangular shape. Therefore, the rigidity around the crankpin bearing 32 can be effectively improved.
[0022]
The first connection pin bearing portion 41 is disposed between one of the second bolts 54 substantially close to the first connection pin bearing portion 41 and the first bolt 26 in the above-described crankpin axial direction. The three points 41, 54, 26 are arranged so as to form a triangle. Accordingly, the load applied from the first connecting pin 12 can be effectively supported mainly by the first bolt 26 and the second bolt 54, and an excessive moment does not act on the third bolt 55 on the opposite side. Similarly, the second connecting pin bearing portion 42 is disposed substantially between the first bolt 26 and the third bolt 55, and these three points are disposed so as to form a triangle. Can be effectively supported mainly by the first bolt 26 and the third bolt 55, and no excessive moment acts on the second bolt 54 on the opposite side.
[0023]
In an assembled state in which the crankpin bearing member 21 and the connecting pin bearing members 22 and 23 are fastened by the bolts 54 and 55, the connecting pin bearing members 22 and 23 and the crankpin bearing member 21 are connected to the bolt joint portion and Only the opposing surfaces in the axial direction are in contact with each other, and there is substantially no contact except in this portion. That is, both are kept substantially in a non-contact state in the direction perpendicular to the axis. More specifically, there is no contact between the outer periphery of the crankpin 4 and the primary notch surface 43 and between the crankpin bearing portion 32 and the secondary notch surface 44 even if some deformation occurs due to the load. In addition, a predetermined clearance is secured.
[0024]
In order to achieve both improvement of the assembling workability and improvement of the strength, the positions of the bolts 54 and 55 for connecting the crankpin bearing body 21 and the connecting pin bearing members 22 and 23 are determined in the axial direction of the crankpin. And the connecting pin bearings 41 and 42 are arranged away from the formation position. In other words, the crankpin bearing 21 and the connecting pin bearing members 22 and 23 are connected at positions away from the connecting pin bearings 41 and 42. More specifically, when viewed in the axial direction, the third bolt 55 is disposed on the substantially opposite side of the first connection pin bearing portion 41 with respect to the axis of the crankpin bearing surface 31, and the second connection pin bearing portion 42 A second bolt 54 is disposed substantially on the opposite side of the second bolt 54.
[0025]
In addition, the two connecting pin bearings 41 and 42 are arranged on the same side with respect to the bearing mating surface 35 and form a triangular shape with the crankpin bearing 32 so that the bearing mating surface 35 has a triangular shape. It is located closer to one end, specifically, on the side (upper side in FIG. 2) where the primary U-shaped notch surface 43 is not open. In this relation, the two bolts 54 and 55 are opposite to the connecting pin bearings 41 and 42 with respect to the bearing mating surface 35, that is, near the opening of the substantially U-shaped primary cutout surface 43 (the lower side in FIG. 2). ).
[0026]
The characteristic configuration of the present invention will be described with reference to FIGS. The central connecting portion 30 of the crankpin bearing body 21 is fixed to the connecting pin bearing members 22 and 23 at three locations around the crankpin bearing portion 32 by bolts 26, 54 and 55 (fixing means). Is partially projected in the radial direction, and has a substantially triangular shape surrounding the crankpin bearing portion 32. In other words, a portion 101 of the central connecting portion 30 between the first bolt 26 and the second bolt 54, that is, a portion 101 crossing the crankpin bearing portion 32 and the first connecting pin bearing portion 41, A portion between the bolt 26 and the third bolt 55, that is, a portion 102 crossing the crankpin bearing portion 32 and the second connecting pin bearing portion 42 is partially radially thinned (shorter in radial dimension). It has become. As described above, the thin portions 101 and 102 have a thin shape along the outer periphery of the crankpin bearing portion 32, thereby avoiding interference with the connecting pins 12, 14 and the upper link 11 and the control link 15, and In addition, while the weight and the size are reduced, the structure is relatively fragile. In particular, the first thin portion 101 located near the first connecting pin bearing portion 41 on which the compressive load from the combustion chamber acts via the piston 1 and the upper link 11, that is, the first connecting pin bearing portion 41 and the crankpin bearing Since a strong tensile force acts on the first thin portion 101 that crosses the space between the first thin portion 101 and the first thin portion 101, a countermeasure is required.
[0027]
Therefore, a predetermined space is provided between the bolt mating surface 103 of the boss 50 and the bolt mating surface 104 of the connection pin bearing members 22 and 23, which are fixed together by the second bolt 54 near the first thin portion 101. The clearance ΔCL is set. By using the clearance ΔCL to strongly tighten the boss portion 50 and the connecting pin bearing members 22 and 23 in the direction approaching each other with the bolt 54, a strong compressive force acts on the first thin portion 101. Even when a strong tensile force acts on the first thin portion 101, the force can be effectively canceled and the maximum value of the tensile stress can be reduced. Accordingly, by reducing the thickness of the first thin portion 101 in the radial direction, the weight of the first thin portion 101 is reduced, and the strength of the first thin portion 101 with respect to the tensile force is effectively improved. Opening can be reliably prevented.
[0028]
In addition, a clearance is similarly set between the bolt butting surfaces of the boss portion 50 and the connecting pin bearing members 22 and 23 which are fastened and fixed together by the third bolt 55 located near the other second thin portion 102. May be.
[0029]
Another operation and effect of the first embodiment will be described in comparison with a comparative example shown in FIGS. 6 and 7A. Most of the operations and effects described here are common to the second and third embodiments described later.
[0030]
The lower link 60 of the comparative example is divided into a pair of divided members 63 and 64 along a mating surface 62 passing through the axis of the crankpin bearing 61, and the two divided members 63 and 64 are bolted with the crankpin interposed therebetween. The structure is fixed by 67. Each of the divided members 63 and 64 is formed with one of the bearing portions 65 and 66 through which the connecting pin is inserted and a half of the crank pin bearing portion 61, respectively.
[0031]
In this comparative example, the axial length of the connecting portion 68 between the crankpin bearing portion 61 and the connecting pin bearing portion 65 (66) is not short, and both axial end portions of both 61 and 65 (66) are not reduced. Are directly connected by the connecting portion 68. Accordingly, since the load applied to both ends in the axial direction of the connecting pin bearing 65 directly acts on both ends in the axial direction of the crank pin bearing 61 via the connecting part 68, the imaginary line in FIG. As shown, both ends in the axial direction of the crankpin bearing 61 are locally largely deformed, so that the crankpin bearing 61 easily comes into contact with the crankpin 4.
[0032]
On the other hand, in the present embodiment, as shown in FIG. 7B, in the portion where the crankpin bearing portion 32 and the connection pin bearing portions 41 and 42 face each other, the connection portion 30 having a short axial length is provided. At the side of the connecting portion 30, both axial ends of the crankpin bearing portion 32 and the axial ends of the connecting pin bearing portions 41 and 42 are in a non-contact state. Therefore, the load from the connecting pin bearings 41 and 42 acts on the central portion in the axial direction of the crankpin bearing 32 via the connecting portion 30. For this reason, the load does not concentrate locally on both ends in the axial direction of the crankpin bearing portion 32, and deformation of both ends in the axial direction is sufficiently suppressed as indicated by the phantom line. As a result, direct contact with the crankpin 4 is suppressed, and the resulting friction and wear are suppressed. The load acting on the central portion in the axial direction of the crankpin bearing portion 32 can be effectively supported by the oil film pressure which is largest at the central portion in the axial direction.
[0033]
In the present embodiment, the crankpin bearing body 21 in which the crankpin bearing portion 32 is formed and the connecting pin bearing members 22 and 23 in which the connecting pin bearing portions 41 and 42 are formed are separate bodies. The bearing distance between the bearing portion 32 and the connecting pin bearing portions 41 and 42 can be made sufficiently small so as not to be in contact with each other due to deformation, and both can be brought close enough. Therefore, the size and weight of the lower link 13 can be reduced.
[0034]
In the comparative example, the connecting pin bearings 65 and 66 are integrally formed with the divided members 63 and 64 having the mating surfaces 62 formed thereon, and the central portions of the shafts of the divided members 63 and 64 are fixed by one bolt 67. Because of the coupling, a force in the bending direction is likely to act on the mating surface 62 of the divided members 63 and 64, and to prevent the mating surface 62 from opening, stiffness against the force in the bending direction is also required. In order to secure the rigidity, the weight tends to further increase. On the other hand, in the present embodiment, the divided members 36 and 37 in which the bearing mating surface 35 is formed and the connecting pin bearing members 22 and 23 in which the connecting pin bearing portions 41 and 42 are formed are separate bodies, and are bolted. Since the load is transmitted and acts from the connecting pin bearings 41 and 42 to the bearing mating surface 35 via the joints, deviation in the load input direction with respect to the bolt axis (force in the bending direction acting on the bearing mating surface 35) is extremely small. Small. Therefore, the rigidity is easily secured, and the weight can be reduced as compared with the comparative example.
[0035]
In the present embodiment, since the pair of connecting pin bearing members 22 and 23 are formed in a plate shape having substantially the same shape as each other, processing and preparation are easy, and cost reduction can be achieved. In addition, by forming each of the connecting pin bearing members 22 and 23 by forging a steel material (steel plate), it is possible to maintain a sufficient hardness and to create a light weight. The crankpin bearing body 21 is formed of a sintered alloy or cast iron, although the strength is lower than that of steel material because the structural rigidity of the crankpin bearing surface needs to be secured more than the strength of the material itself. It is desirable. As described above, in the present embodiment, the degree of freedom of the shape is high, and it is possible to reduce the size and weight while securing the desired rigidity.
[0036]
8 to 10 show a second embodiment. In the following embodiments, portions different from those of the first embodiment will be mainly described, and the same portions will be denoted by the same reference numerals and redundant description will be appropriately omitted.
[0037]
Four bosses 50 fixed to the connecting pin bearing members 22 and 23 by bolts 54 and 55 are formed in the second divided member 37. Further, an extension boss portion 56 is formed on the first divided member 36. The extension boss portion 56 has a bolt hole 56a through which the second bolt 54 closer to the first connection pin bearing portion 41 is inserted, and the second bolt 54 and the boss portion 50a of the second divided member 37 are used together with the connection pin. They are fixed to the bearing members 22 and 23 together. As shown in FIG. 10C, an extension 57 extending in the circumferential direction beyond the bearing mating surface 35 is formed at the center connecting portion 30 of the first divided member 36. The above-mentioned extension boss portion 56 is formed. The second divided member 37 has a cutout 58 into which the extension 57 is fitted.
[0038]
As described above, by fixing the extension boss portion 56 of the first divided member 36 to the connection pin bearing members 22 and 23 together with the boss portion 50a of the second divided member 37 by the second bolt 54, the first boss portion on the bearing mating surface 35 is formed. The joining force between the dividing member 36 and the second dividing member 37 can be further increased, and the opening of the dividing members 36 and 37 can be more reliably prevented.
[0039]
In this embodiment, the first bolt 26 is disposed closer to the second connection pin bearing portion 42 in order to mainly avoid interference with the upper link 11, and is relatively far from the first connection pin bearing portion 41. In this relation, the first divided member 36 is located at a portion 101 close to the first connecting pin bearing portion 41, that is, at a portion crossing the crankpin bearing portion 32 and the first connecting pin bearing portion 41, and is partially thin. It is difficult to further secure the rigidity of the reduced first thin portion 101, and the first thin portion 101 is easily deformed. Therefore, the above-mentioned extended boss portion 56 is formed only on the side close to the first thin portion 101 where rigidity is particularly required.
[0040]
Then, as shown in FIG. 9, a predetermined surface is provided between the abutting surface 103 of the extension boss portion 56 which is abutted and fastened by the second bolt 54 and the abutting surface 104 which is the end surface of the connecting pin bearing members 22 and 23. Is set. Therefore, when the bolt 54 is tightened, the boss portion 50 and the extended boss portion 56 and the connection pin bearing members 22 and 23 are strongly tightened in a direction approaching each other by using the clearance ΔCL. Since a strong compressive force acts on the thin portion 101, even when a strong tensile force acts on the first thin portion 101, the force can be effectively canceled and the maximum value of the tensile stress can be reduced. Can be. Accordingly, by reducing the thickness of the first thin portion 101 in the radial direction, the weight of the first thin portion 101 with respect to the tensile force is effectively improved while the weight and the size of the link are reduced, and the bearing mating surface 35 is improved. Opening can be reliably prevented.
[0041]
11 to 14 show a third embodiment of the present invention. In this embodiment, the first connection pin bearing 41 that is relatively close to the crankpin bearing 32 is formed as a separate member from the crankpin bearing 21A, while being relatively far from the crankpin bearing 32. The second connecting pin bearing portion 42A is formed integrally with one of the second divided members 37A of the crankpin bearing body 21A.
[0042]
More specifically, the connecting pin bearing members 22A and 23A have a shape in which substantially half of the connecting pin bearing members 22 and 23 of the first and second embodiments including the second connecting pin bearing portion 42 is cut out. As in the first embodiment, the pair of second bolts 54 fasten the second divided member 37A and the connecting pin bearing members 22A and 23A in a direction perpendicular to the axis with the first divided member 36A interposed therebetween. On the other hand, one third bolt 55A directly couples the first divided member 36A and the second divided member 37A in the direction orthogonal to the axis. That is, the number of the third bolts 55A can be reduced as compared with the first embodiment.
[0043]
In addition, a predetermined clearance ΔCL is set between the butting surface 103 of the boss portion 50 which is butted and fastened by the second bolt 54 and the butting surface 104 which is the end surface of the connecting pin bearing members 22 and 23. . Therefore, when the bolt 54 is tightened, the boss portion 50 and the connecting pin bearing members 22 and 23 are strongly tightened in a direction approaching each other by utilizing the clearance ΔCL described above, so that the first thin portion 101 is strong. Since a compressive force acts, even when a strong tensile force acts on the first thin portion 101, the force can be effectively canceled and the maximum value of the tensile stress can be reduced. Therefore, by reducing the thickness of the first thin portion 101 in the radial direction, the weight of the first thin portion 101 is reduced, and the strength of the first thin portion 101 with respect to the tensile force is effectively improved. 35 can be reliably prevented from opening.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a variable compression ratio mechanism of an internal combustion engine to which a lower link as a link assembly component according to the present invention is applied.
FIG. 2 is an exploded perspective view showing the lower link of the first embodiment.
FIG. 3 is a front view (a), a rear view (b), and a bottom view (c) showing a pair of connecting pin bearing members of the first embodiment.
FIG. 4 is a front view (a), a top view (b), a left side view (c), and a right side view (d) showing the lower link of the first embodiment.
FIGS. 5A and 5B are a front view and a right side view showing a crankpin bearing member of the first embodiment.
FIG. 6 is a front view (a) and a top view (b) showing a lower link according to a comparative example.
FIG. 7 is an explanatory diagram of an operation of a lower link according to a comparative example (a) and the present invention (b).
FIG. 8 is an exploded perspective view showing a lower link according to a second embodiment of the present invention.
FIG. 9 is a front view (a), a top view (b), a left side view (c), and a right side view (d) showing the lower link of the second embodiment.
FIG. 10 is a front view (a), a right side view (b), and an exploded front view (c) showing a crankpin bearing member of a second embodiment.
FIG. 11 is an exploded perspective view showing a lower link according to a third embodiment of the present invention.
FIG. 12 is a front view showing a lower link according to a third embodiment;
FIG. 13 is a front view (a) and a right side view (b) showing a crankpin bearing body of a third embodiment.
FIG. 14 is a front view (a), a rear view (b), and a bottom view (c) showing a pair of connecting pin bearing members of the third embodiment.
[Explanation of symbols]
4 Crank pin 11 Upper link 12 First connection pin 13 Lower link 14 Second connection pin 15 Control link 17 Support position varying means 21 Crank pin bearing bodies 22 and 23 Connection pin bearing member 30 Central connecting part 32 ... Crank pin bearing part 36 ... First divided member 37 ... Second divided member 41 ... First connecting pin bearing part 42 ... Second connecting pin bearing part 54 ... Second bolt 101 ... First thin part

Claims (5)

A link for an internal combustion engine comprising: a crankpin bearing body having a substantially cylindrical crankpin bearing portion through which a crankpin is inserted; and a connecting pin bearing member having a connecting pin bearing portion through which a connecting pin connecting another link is inserted. In assembly parts,
The crankpin bearing body has a central connecting portion projecting radially outward from an axially central portion of the crankpin bearing portion, and the central connecting portion is formed between the connecting pin bearing portion and the crankpin bearing portion. The thin part that crosses the space is partially thinned in the radial direction,
And, at a plurality of locations around the crankpin bearing, there are fixing means for fixing the center connecting part and the crankpin bearing at a plurality of places, and the fixing means is provided near the thin part in the center connecting part. A boss that protrudes more in the axial direction and the connecting pin bearing member have bolts that fasten together in the direction perpendicular to the axis, and
A link assembly part for an internal combustion engine, wherein a predetermined clearance is provided between bolt-coupling surfaces of the boss portion and the connecting pin bearing member that are fastened together by the bolt. The internal combustion engine has an upper link having one end connected to the piston via a piston pin, and the other end of the upper link connected via a first connection pin, and is rotatably attached to a crankpin of a crankshaft. A lower link, a control link having one end connected to the lower link via a second connecting pin, and the other end swingably supported with respect to the internal combustion engine body. A support position variable means for displacing the position of the other end of the control link with respect to the internal combustion engine body, and a variable compression ratio mechanism having
The link assembly according to claim 1, wherein the lower link is a link assembly. The link assembly according to claim 2, wherein the other link is an upper link. The said connection pin bearing member is couple | bonded with the crankpin bearing body only in the said center connection part, It is non-contact with the said crankpin bearing part, The Claim 1 characterized by the above-mentioned. A link assembly for an internal combustion engine as described. The crankpin bearing body is constituted by a pair of divided members divided into two by a bearing mating surface along the axis of the crankpin bearing portion,
5. The internal combustion engine according to claim 1, wherein the bolt extends in a direction crossing the bearing mating surface, and also has a function of connecting the pair of split members with the bearing mating surface. 6. Engine link assembly.

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