JP2012026384A - Connection pin bearing structure of link mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of requiring an improvement in security of lubricity of a connection pin bearing part, though strength and rigidity of a lower link are improved, in a press-fit system for fixing a connection pin to the lower link.SOLUTION: A pin central part 36 relatively rotatably opposed to a second bearing part of an upper link is deformed in a barrel shape of expanding a barrel quantity corresponding to a radial directional increase quantity toward the central part in the axial direction by fixing pin both end parts 35 of the connection pin 25 by press-in to a bifurcated first bearing part of the lower link 12. In the pin central part 36 deformed in this barrel shape, the axis 41A of a hollow hole 41 is made eccentric to the large load position α1 side to the axis 25A of the connection pin 25 so that a barrel quantity B1 in a large load position α1 corresponding to the predetermined load acting direction, becomes larger than a barrel quantity B2 of an opposite side small load position α2.

Description

  The present invention relates to a connection pin bearing structure of a link mechanism, and more particularly to a connection pin bearing structure suitable for a multi-link type piston-crank mechanism of an internal combustion engine.

  As a mechanism capable of changing the engine compression ratio of an internal combustion engine according to the engine operating state, for example, as disclosed in Patent Document 1, a plurality of links connecting pistons and a crankshaft, and the postures of these links are controlled. There are known ones using a multi-link type piston-crank mechanism provided with a link to be operated. Specifically, a lower link is rotatably connected to the crank pin, and an upper link is connected to the lower link through an upper pin, and a control link is connected to the lower link through a control pin. The link operation is restricted. Then, by controlling the control link according to the engine operating state and changing the position of the lower link, that is, the rotational position with respect to the crank pin, the top dead center position of the piston connected to the other end of the upper link is controlled, and the engine It controls the compression ratio.

  In a pin connection portion between the first link member (lower link) and the second link member (upper link, control link) by a connection pin such as an upper pin or a control pin, the first link member has a bifurcated first bearing portion. The first and second bearing portions are disposed on the same axis with a predetermined gap therebetween, and the second bearing portion of the second link member is disposed between the pair of first bearing portions. By inserting the connecting pin into the first and second link members, the first and second link members are connected so as to be relatively rotatable.

JP 2009-180276 A

  As a connecting pin bearing structure of a link mechanism using this type of connecting pin, a press-fit method in which both ends of the connecting pin are fixed to the pair of first bearing portions by press fitting, or the connecting pin is connected to the first and second links. There is known a full float system that can rotate with respect to both the first and second bearing portions of the member. In the press-fit method, compared with the full float method, both ends of the connecting pin are fixed to the first bearing portion of the first link member (lower link), and the connecting pin is used as the strength member of the first link member. In order to function, it is advantageous in terms of durability and reliability of the link member, but on the other hand, the load and sliding speed of the bearing portion between the connecting pin and the second bearing portion that rotate relative to each other increase, and the bearing portion It is difficult to ensure cooling (seizure resistance) and lubricity.

  By the way, in the press-fit method, when both ends of the connecting pin are press-fitted into the bifurcated first bearing portion, the both ends of the pin are deformed in the direction of diameter reduction due to the press-fitting, and is exaggerated in FIG. As shown in the drawing, the radial dimension increases as the pin center portion 3 of the connecting pin that faces and slides relative to the second bearing portion 2 of the second link member moves toward the axial center portion. It transforms into a barrel shape. In this way, the pin central portion 3 is deformed into a barrel shape, so that the inflow / outflow amount of oil (breathing volume) of the lubricating oil from both ends in the axial direction is increased and the lubricity is improved. With respect to the tilting behavior in the axial inclination direction, the so-called one-side contact, in which the pin center portion 3 and the second bearing portion 2 are in strong local contact at the edge portions at both ends in the axial direction, can be suppressed / relieved. In particular, the larger the load on the bearing portion, the easier it is to hit one side. Therefore, the degree of deformation due to the barrel shape, that is, the barrel amount B0 corresponding to the increase in the radial dimension of the pin central portion 3 can be increased. desirable. However, if the barrel-shaped barrel amount becomes too large with respect to the load acting on the bearing portion, conversely, the pin center portion and the second bearing portion locally come into strong contact with each other in the axial center portion, The load concentrates on this part.

  In addition, when the press-fit method is applied, the connecting pin is fixed to one of the first link members, so that a specific large load caused by combustion pressure or the like repeatedly acts on a specific circumferential position of the connecting pin. It will be. That is, the load in the bearing portion of the pin center portion of the connecting pin that rotates relative to each other and the second bearing portion of the second link member has a different load distribution in the circumferential direction. For this reason, if the connecting pin is deformed into a barrel shape with a substantially uniform barrel amount in the circumferential direction, the circumferential position that receives a large load will cause one end contact at both axial ends due to insufficient barrel amount. On the other hand, at the circumferential position where the load is small, the barrel amount becomes excessive, and the pin central portion and the second bearing portion are likely to come into strong local contact at the axial central portion.

  In particular, in the structure in which the first and second link members are repeatedly reciprocatingly rotated (oscillated) within a predetermined angular range as in the above-described multi-link type piston-crank mechanism, the wedge film effect by the oil film is obtained. In addition, since the variation in load depending on the position in the circumferential direction is large, it is very difficult to ensure cooling performance (seizure resistance) and lubricity.

  The present invention has been made in view of such circumstances, and a first link member in which two first bearing portions are disposed on the same axis with a predetermined gap therebetween, and a second bearing portion having a second bearing portion. The link member, the two first bearing portions, and the second bearing portion disposed between the two first bearing portions are inserted and fixed to the first bearing portion by press-fitting, In a link pin bearing structure of a link mechanism having a link pin that connects the first link member and the second link member in a relatively rotatable manner, a predetermined load is applied to the central portion of the pin that faces the second bearing portion in a relatively rotatable manner. The barrel amount at the first circumferential position corresponding to the action direction is set to be larger than at least the barrel amount at the second circumferential position where only a load smaller than the predetermined load acts. Trying

  The barrel amount corresponds to an increase in the radial dimension, and more specifically, the radius of the connecting pin press-fitted into the first bearing portion and the connecting pin press-fitted into the first bearing portion. This corresponds to the absolute value of the difference between the center line and the distance from the outline of the connecting pin inserted through the second bearing portion.

  By press-fitting the connecting pin into the first bearing portion, the center portion of the pin is deformed into a barrel shape, that is, deformed into a shape in which the barrel amount increases toward the central portion in the axial direction. Here, the barrel amount at the first circumferential position that receives a large load corresponding to a predetermined load acting direction is larger than the barrel amount at the second circumferential position where the load on the opposite side is small. The barrel amount is varied according to the circumferential position. That is, the shape and dimensions of the connecting pin (before press-fitting) are such that the barrel amount at the first circumferential position is larger than the barrel amount at the second circumferential position by deformation into the barrel shape by press-fitting. Is set.

  In this way, by increasing the barrel amount at the first circumferential position that receives a large load in a concentrated manner in the central portion of the connecting pin, the occurrence of per side is suppressed and the acting load is small. By reducing the barrel amount at the second circumferential position, it is possible to suppress or alleviate the load acting on the central portion in the axial direction due to the excessive barrel amount.

  In other words, in the present invention, by optimizing the barrel amount at the center of the pin in a form corresponding to the magnitude of the load acting on the link mechanism having a load distribution that varies in size depending on the circumferential position of the connecting pin, Improve seizure resistance, lubricity, etc. by suppressing or mitigating load concentration (per piece) at both ends in the bearing portion of the central portion and the second bearing portion and load concentration at the central portion in the axial direction. Can do. And since the barrel shape of a connection pin is optimized using the fixation by press injection, an increase in work man-hours is not caused.

  As described above, as an example of the shape before press-fitting of the connecting pin for deforming into a barrel shape having a different barrel amount in the circumferential direction, a hollow hole extending along the axial direction of the connecting pin is formed in the connecting pin. . The shaft center of the hollow hole is decentered toward the first circumferential position with respect to the shaft center of the connecting pin. As a result, in the vicinity of the first circumferential position, the thickness between the outer periphery of the hollow hole and the outer periphery of the connecting pin is reduced, and the rigidity thereof is reduced. Becomes larger. On the other hand, in the vicinity of the second circumferential position, the thickness between the outer periphery of the hollow hole and the outer periphery of the connecting pin is increased, and the rigidity thereof is increased. Get smaller.

  As described above, according to the present invention, the second bearing portion of the other second link member is adopted while adopting the press-fit method in which the connecting pin is fixed to the two first bearing portions of the first link member by press-fitting. At the pin center part of the connecting pin that is in sliding contact with the shaft, both ends in the axial direction are optimized by optimizing the barrel amount of the pin center part that is deformed into a barrel shape by press-fitting in a shape corresponding to the load that varies depending on the circumferential position. It is possible to suppress or alleviate the load concentration (per piece) and the load concentration at the central portion in the axial direction, and improve seizure resistance, lubricity and the like.

Sectional drawing which shows the multiple link type piston-crank mechanism of the internal combustion engine which is an example of the link mechanism which concerns on this invention. The perspective view which shows the lower link and connecting pin of the said multiple link type piston-crank mechanism. Sectional drawing which shows the connection pin bearing part of the said lower link. The load diagram (A) of the upper pin bearing part of a lower link (C), and the load diagram (B) of a control pin bearing part. Sectional drawing which shows the connection pin bearing part which concerns on a comparative example (A) and 1st Example (B) of this invention. Sectional drawing which shows a control pin bearing part (A) and an upper pin bearing part (B). Sectional drawing which shows the connection pin bearing part which concerns on 1st Example (A) and 2nd Example (B) of this invention. Explanatory drawing (B) which expand | deployed the pin center part (A) of the connection pin which concerns on 3rd Example of this invention, and its outer peripheral surface in planar shape. FIG. 9 is an enlarged cross-sectional view showing the vicinity of the dimple in FIG. 8. Explanatory drawing which shows the dimple formation position of the lower link which concerns on 4th Example of this invention. Explanatory drawing which shows distribution of PV (maximum) value of the connection pin bearing part of the lower link of FIG. The cross-sectional view which shows the lower link and upper pin in which the splash channel | path which concerns on 5th Example of this invention was formed. Explanatory drawing which exaggerates and shows the aspect which the pin center part of a connection pin deform | transforms into a barrel shape.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a multi-link piston-crank mechanism 1 of an internal combustion engine as an example of a link mechanism according to the present invention. This multi-link type piston-crank mechanism 1 connects a piston 22 and a crankshaft 21 by two link members, that is, an upper link (second link member) 11 and a lower link (first link member) 12. At the same time, the control link (second link member) 13 is used to control the posture of the lower link 12 so that the piston top dead center position, and hence the engine compression ratio (geometric compression ratio) can be changed. is there.

  The piston 22 receives the combustion pressure and reciprocates in the cylinder 20. The upper end of the upper link 11 is connected to the piston 22 via a piston pin 24. The lower end of the upper link 11 is connected to one end of the lower link 12 via the upper pin 25. The other end of the lower link 12 whose one end is connected to the upper link 11 is connected to the control link 13 via the control pin 26.

  The lower link 12 is a crankpin bearing portion 101 formed substantially at the center, is rotatably mounted on the crankpin 21b of the crankshaft 21, and swings about the crankpin 21b as a central axis. The lower link 12 is divided into two divided members 105 and 106 sandwiching the crank pin 21b so that the lower link 12 can be assembled to the crank pin 21b. These divided members 105 and 106 are composed of two bolts. 103 and 104 are fastened together with the crank pin 21b interposed therebetween.

  The crankshaft 21 includes a plurality of journals 21a and a crankpin 21b. The journal 21 a is rotatably supported by the cylinder block 23 and the ladder frame 28. The crank pin 21b is provided for each cylinder and is eccentric from the journal 21a by a predetermined amount, and the lower link 12 is swingably attached thereto.

  The other end of the control link 13 whose one end is connected to the lower link 12 is an eccentric cam portion that is eccentric from the center of rotation of the control shaft 14 that is rotatably supported by the engine body (a fixed body such as a cylinder block or an oil pan). 15 is connected. The control link 13 swings around the eccentric cam portion 15. The eccentric cam portion 15 moves when the control shaft 14 is rotated by a compression ratio control actuator (not shown).

  In such a multi-link piston-crank mechanism 1, when the compression ratio is increased, the compression ratio control actuator is driven to lower the eccentric cam portion 15 of the control shaft 14. Then, the lower link 12 moves clockwise, the upper pin 25 is raised, and the position of the top dead center of the piston 22 is raised. When the compression ratio is lowered, the eccentric cam portion 15 of the control shaft 14 is raised by driving the compression ratio control actuator. Then, the lower link 12 moves counterclockwise, the upper pin 25 is lowered, and the position of the top dead center of the piston 22 is lowered. It should be noted that the compression ratio can be continuously changed between them.

  By the way, in such a multi-link type piston-crank mechanism 1, the lower link 12 receives the combustion pressure received by the piston 22 from the upper pin 25 through the upper link 11, and looks like a lever having the control pin 26 as a fulcrum. The force is transmitted to the crankpin 21b with a simple operation. That is, the lower link 12 receives large loads in different directions from the crank pin 21b, the upper pin 25, and the control pin 26 in each stroke of the internal combustion engine. Accordingly, since a large internal force is repeatedly generated in the lower link 12, the lower link as a whole needs to have strength and rigidity that can withstand this.

  Therefore, the lower link 12 and the upper pin 25 and the control pin 26 (hereinafter collectively referred to as “connecting pin”) are connected to each other without causing the lower link 12 and the connecting pin to rotate or slide relative to each other. By adopting a press-fit (press-fit) method in which both are fixed integrally, the durability of the entire lower link is improved.

  With reference to FIG.2 and FIG.3, the pin connection structure of such a lower link 12 is demonstrated here taking the connection structure by the side of the upper pin 25 as an example. One split member 105 of the lower link 12 has a pair of bifurcated piece portions 31 integrally standing in a bifurcated manner from the root portion 32 with a predetermined gap therebetween, and each bifurcated piece portion 31 has a cylindrical surface. The 1st bearing part 33 which makes is formed by penetration. The pair of first bearing portions 33 are arranged on the same axis with a predetermined gap therebetween. On the other hand, a second bearing portion 34 having a cylindrical surface is formed through the lower end portion of the upper link 11. And in the state which has arrange | positioned the 2nd bearing part 34 between a pair of 1st bearing parts 33, the pin of the upper pin 25 is inserted by pressing the upper pin 25 into these 1st, 2nd bearing parts 34 from one side. Both end portions 35 are fixed to the pair of first bearing portions 33 by press fitting, and the pin center portion 36 of the upper pin 25 faces the inner periphery of the second bearing portion 34 so as to be relatively rotatable with a slight gap therebetween. . That is, the first bearing portion 33 is set to have a diameter smaller than that of the upper pin 25 before press-fitting so that the upper pin 25 is fixed by press-fitting, and the second bearing portion 34 is inserted so that the upper pin 25 is relatively rotatable. Thus, the diameter is set larger than the upper pin 25 before press-fitting.

  In addition, since the connection structure by the side of the control pin 26 provided in the other division member 106 of the lower link 12 is the same as the connection structure by the side of the upper pin 25 mentioned above, it attaches | subjects the same referential mark and overlaps. Description is omitted.

  Referring to FIG. 4, (A) shows a load diagram of the bearing portion of the upper pin 25, (B) shows a load diagram of the bearing portion of the control pin 26, and each of the connecting pin shaft centers shown in (C). The magnitude and direction (circumferential position) of the load in the XY coordinate system with the origin as the origin are shown. As shown in FIGS. 4A and 4C, the largest load is applied to the upper pin bearing portion in the vicinity of the combustion TDC (compression top dead center) on which the combustion pressure acts, and this maximum load direction A is met. At a predetermined large load position (first circumferential direction position) α1, the maximum contact load between the pin center portion 36 of the upper pin 25 and the second bearing portion 34 of the upper link 11 (the pin center portion 36 and the second bearing). A load in a direction in which the portion 34 approaches each other). Further, as shown in FIGS. 4B and 4C, the largest load is applied to the control pin bearing portion in the vicinity of the combustion TDC (compression top dead center) where the combustion pressure acts. At a predetermined large load position (first circumferential position) α1 along B, the maximum contact load acts between the pin center portion 36 of the control pin 26 and the second bearing portion 34 of the control link 13.

  In the following, with reference to the illustrated embodiment, the characteristic configuration and the operation and effect of the connecting pin bearing structure of the link mechanism will be listed. In the following description, the upper pins 25 and the control pins 26 are collectively referred to as “connecting pins” unless the upper pins 25 and the control pins 26 need to be distinguished. Further, in FIG. 5 and the like, the deformation of the pin central portion 36 into a barrel shape is exaggerated from the actual one for easy understanding.

  (1) FIG. 5B shows a pin connection structure according to the first embodiment of the present invention, and FIG. 5A shows a pin connection structure according to a comparative example. The coupling pin 25 is fixed to the first bearing portion 33 by press-fitting, so that the barrel amount of the pin central portion 36 that faces the second bearing portion 34 so as to be relatively rotatable is increased toward the axial central portion. It bulges and deforms into a barrel shape. Here, the barrel amounts B1 and B2 correspond to an increase in the radial dimension due to the press-fitting of the connecting pin 25. Specifically, the radius L0 of the connecting pin 25 press-fitted into the first bearing portion 33, and The absolute value (L1-L0, L2-L0) of the difference between the distances L1 and L2 from the center line of the connecting pin press-fitted into the first bearing portion to the outline of the connecting pin inserted into the second bearing portion Equivalent to.

  In this embodiment, as shown in FIG. 5 (B), the pin center portion 36 deformed into the barrel shape has a large load position (see FIG. 4 (C)) corresponding to a predetermined load acting direction A (see FIG. 4 (C)). First barrel position) The maximum barrel amount B1 at α1 is a position where at least a load smaller than a predetermined large load is applied, for example, a position opposite to the large load position with respect to the axis of the connecting pin 25A. Is set to be larger than the barrel amount B2 of the small load position (second circumferential position) α2. In other words, the shape and dimensions of the connecting pin 25 before press-fitting are set so that the barrel amount B1 at the large load position α1 is larger than the barrel amount B2 at the small load position α2.

  Thus, by increasing the barrel amount B1 at the large load position α1 that receives a large load in a concentrated manner in the pin center portion 36 of the connecting pin 25, the load concentration (at one side) at both ends in the axial direction is increased. In addition, by reducing the barrel amount B2 at the small load position α2 where the load is small, it is possible to prevent the load from acting on the central portion in the axial direction due to the excessive barrel amount. In this way, by optimizing the barrel amount in the pin central portion 36 of the connecting pin in a form corresponding to the circumferential distribution of the load, the load concentration (per piece) at both axial ends of the pin central portion 36 is achieved. In addition, it is possible to improve the seizure resistance, lubricity and the like by suppressing the concentration of the load at the central portion in the axial direction. And since the barrel shape of a connection pin is optimized using the fixation by press injection, an increase in work man-hours is not caused. However, in the present embodiment, when the connecting pin is press-fitted, it is necessary to align the first bearing portion on the lower link side and the connecting pin in the circumferential direction by a technique such as marking.

  (2) As described above, as an example of the shape before press-fitting of the connecting pin for obtaining the barrel shape having different barrel amounts, in the first embodiment shown in FIG. A hollow hole 41 extending along the axial direction of 25 is formed through the entire length of the connecting pin 25. The shaft center (center) 41A of the hollow hole 41 is decentered by a predetermined amount ΔH1 toward the large load position α1 with respect to the center of the outer peripheral surface of the connection pin 25, that is, the shaft center 25A of the connection pin. That is, the position of the center of gravity of the cross-section in the direction perpendicular to the axis of the hollow hole 41 (in the example of FIG. 5, the position of the axis 41A) is unevenly distributed in the load acting direction A with respect to the center line 25A of the press-fitted connecting pin 25. It has been shifted to. As a result, in the vicinity of the heavy load position α1, the thickness between the outer periphery of the hollow hole 41 and the outer periphery of the connecting pin 25 is reduced, and the rigidity thereof is reduced. B1 increases. On the other hand, in the vicinity of the light load position α2 on the opposite side, the thickness of the outer periphery of the hollow hole 41 and the outer periphery of the connecting pin 25 is increased, and the rigidity thereof is increased. B2 becomes smaller. Thus, by forming the eccentric hollow hole 41 in the connecting pin 25, it is possible to easily obtain the connecting pin 25 in which the barrel amount after deformation by press-fitting differs in the circumferential direction.

  (3) Further, by adjusting the amount of eccentricity of the hollow hole 41, the barrel amount can be adjusted in a form corresponding to the magnitude of the load. For example, in the case shown in FIG. 4, since the maximum load acting on the upper pin 25 is larger than the maximum load acting on the control pin 26, the eccentric amount ΔH1 of the hollow hole 41 of the upper pin 25 is set as shown in FIG. The eccentric amount ΔH2 of the hollow hole 41 of the control pin 26 is set larger. As a result, the barrel amount B1a on the upper pin 25 side with a relatively large load increases, and the barrel amount B1b on the control pin 26 side with a relatively small load decreases, and an appropriate barrel amount according to the magnitude of the load. Can be obtained.

  It should be noted that the magnitude of the load acting on the pin central portion 36 is such that the ratio of the distance from the center of the crank pin bearing portion 101 of the lower link 12 to the center of each connecting pin 25, 26 (lever ratio) or the like. Depending on the dimensions and layout, as described above, the upper pin 25 does not necessarily have a larger maximum load. Therefore, if the control pin 26 has a larger maximum load, the barrel amount on the control pin 26 side may be relatively increased.

  (4) In the first embodiment, the hollow hole 41 is formed through the entire length in the axial direction of the connecting pin 25 as shown in FIG. 7A, but as in the second embodiment shown in FIG. 7B. In addition, hollow holes 42 having a predetermined axial depth ΔD may be provided in each of both end faces of the connecting pin 25. In this case, by adjusting the depth ΔD of the hollow hole 42, it is possible to adjust the sliding surface shape of the outer peripheral surface of the pin center portion 36 curved into a barrel shape. Specifically, as the depth ΔD of the hollow hole 42 is shortened, the barrel amount (overhang amount) of the axial central portion in which the hollow hole 42 does not exist in the pin central portion 36 is suppressed. In other words, the flat portion 36a remains in a relatively wide range. As a result, local contact at the central portion in the axial direction can be further suppressed / relieved, the load holding force by the lubricating oil film can be increased, and the lubricity can be further improved.

  Moreover, the shape of the hollow holes 41 and 42 is not limited to the cylindrical shape as in the above-described embodiment, but may be, for example, a conical shape that tapers toward the center in the axial direction, and the cross-sectional shape thereof is elliptical. It may be in a shape.

  (5) As shown in FIGS. 4A and 4C, on the upper pin 25 side, the load acting direction A is set in a direction from the root portion 32 to the first bearing portion 33 in the bifurcated piece portion 31, The barrel amount of the circumferential position (first circumferential position) α1 on the distal end side far from the root portion 32 in the pin central portion of the connecting pin 25 press-fitted into one bearing portion is the circumferential direction on the root portion 32 side. It is larger than the barrel amount at the position (second circumferential position) α2. That is, the large load position α1 is located on the tip end side opposite to the root portion 32 across the first bearing portion 33 in the bifurcated piece portion 31. Here, the rigidity of the thick base portion 32 side is higher than that of the tip end side of the bifurcated piece portion 31. Therefore, as in the comparative example shown in FIG. 5A, the axial center 41A of the hollow hole 41 is decentered with respect to the axial center 25A of the connecting pin 25 without considering the circumferential load distribution. However, when the connecting pins 25 are set on the same line, the pressing load on the root side having high rigidity is increased when the connecting pin 25 is press-fitted, and the barrel amount B2 ′ on the root side is the barrel amount on the tip side of the bifurcated piece 31. It becomes larger than B1 ′. Accordingly, the barrel amount B1 ′ at the large load position α1 is relatively small and it is easy to cause a single contact due to load concentration at both ends, and the barrel amount B2 ′ at the small load position α2 is relatively large to be axially increased. It tends to cause load concentration at the center.

  On the other hand, in the connection pin bearing structure in the first embodiment shown in FIG. 5B, the large load position α1 is positioned on the distal end side of the bifurcated piece portion 31 having low rigidity as described above. Thus, by decentering the hollow hole 41 in the direction of the large load position α1, the barrel amount B1 at the large load position α1 is relatively increased while the barrel amount B2 at the small load position α2 is relatively decreased. The load concentration as in the comparative example can be effectively suppressed and avoided.

  (6) FIG. 8B is an explanatory view in which the outer peripheral surface of the pin center portion 36 of the connecting pin 25 shown in FIG. In the third embodiment shown in FIGS. 8 and 9, a plurality of oil sump portions that are partially recessed with respect to the outer peripheral surface are provided in the axial central portion of the pin central portion 36 of the connecting pin 25 having a barrel shape. The dimples 44 are intermittently formed in the circumferential direction.

  Accordingly, as shown in FIG. 9, the second bearing portion 34 of the second link member (upper link 11 or control link 13) moves in the bearing sliding direction with respect to the pin center portion 36 of the connecting pin 25 during actual engine operation. When rotating, as shown by the arrow Y1 in FIG. 9, the lubricating oil in the dimple 44 flows out from the dimple 44 in the bearing sliding direction due to the shear stress due to viscosity, and lubricates the central portion in the axial direction where the oil amount and oil film are likely to be insufficient. Since oil is appropriately supplied, the lubricity and cooling performance at the axially central portion can be further improved.

  (7) Here, as the sliding speed of the bearing portion between the second bearing portion 34 and the pin central portion 36 increases, the amount of oil flowing out of the dimple 44 increases. Further, as the load acting on the bearing portion increases, a larger amount of lubricating oil is required. Therefore, in the case where the dimple 44 is provided in a part of the circumferential direction in order to suppress the decrease in strength and rigidity due to the formation of the dimple 44, the load and the sliding speed are reduced as in the fourth embodiment shown in FIG. The dimples 44 may be disposed only in the large high PV regions 45 and 46. Here, the PV (maximum) value is an index value according to the sliding speed and the load, and increases as the sliding speed increases and increases as the load increases. As shown in FIG. 11, in this embodiment, in the upper pin side (U side) bearing portion, the vicinity of the exhaust top dead center is the high PV region 45, and in the control pin side (C side) bearing portion. The vicinity of the combustion top dead center (compression top dead center) is the high PV region 46.

  (8) The lower link 12 in the multi-link type piston-crank mechanism 1 is not only required to have high strength and rigidity to satisfy the durability and reliability as the main motion system parts, but also combustion during actual engine operation. Due to the pressure and inertia force, a large load of the same level as that of the crank pin bearing 101 is repeatedly applied to the connecting pin bearings of the upper pin and the control pin. Therefore, the application of the present invention to the connecting pin bearing portion in this lower link is extremely effective.

  (9) In the fifth embodiment shown in FIG. 12, the lubricating oil is supplied to the bearing portion of the connecting pin 25 in order to secure the amount of lubricating oil to the connecting pin bearing portion and further improve the lubricity. Splash passages 47 and 48 are formed. The first splash passage 47 is formed in the lower link 12 and has one end opened to the crankpin bearing portion 101 and the other end opened to the root portion 32 connecting the pair of forked pieces 31. Lubricating oil is injected and supplied from the portion 101 toward the upper pin 25 side. The second splash passage 48 is formed in the inner and outer periphery of the cylindrical portion 34A that rotatably supports the connecting pin 25 at the lower end of the upper pin 11, and one end opens on the outer peripheral surface of the cylindrical portion 34A and the other end is the connecting pin. Opening in the inner peripheral surface of the cylindrical portion 34 </ b> A that is in sliding contact with 25, the lubricating oil is supplied to the bearing portion of the connecting pin 25. Similarly, a splash passage may be provided on the control pin 26 side.

  (10) Further, the shape of the inner peripheral surface / bearing surface of the second bearing portion 34 of the second link member that is in sliding contact with the pin central portion 36 of the connecting pin 25 is not an elliptical shape according to the circumferential distribution of the load. A circular shape may be used.

11 ... Upper link (second link member)
12 ... Lower link (first link member)
13 ... Control link (second link member)
21 ... Crankshaft 25 ... Upper pin (connection pin)
26 ... Control pin (connecting pin)
31 ... forked part 31
32 ... Root part 33 ... 1st bearing part 34 ... 2nd bearing part 35 ... Pin both ends 36 ... Pin center part 41, 42 ... Hollow hole 44 ... Dimple 47, 48 ... Splash passage

Claims (7)

A first link member in which two first bearing portions are disposed on the same axis with a predetermined gap therebetween;
A second link member having a second bearing portion;
The two first bearing portions and the second bearing portion disposed between the two first bearing portions are inserted and fixed to the first bearing portion by press fitting, and the first link member and A connection pin bearing structure of a link mechanism having a connection pin for connecting the second link member to be relatively rotatable,
The difference between the radius of the connecting pin press-fitted into the first bearing part and the distance from the center line of the connecting pin press-fitted into the first bearing part to the outline of the connecting pin inserted through the second bearing part When the absolute value of is determined as the barrel amount,
In the central portion of the pin that faces the second bearing portion so as to be relatively rotatable, the barrel amount at the first circumferential position corresponding to the predetermined load application direction acts at least a load smaller than the predetermined load. A connecting pin bearing structure for a link mechanism, wherein the connecting pin bearing structure is set so as to be larger than a barrel amount at a circumferential position. A hollow hole extending along the axial direction of the connecting pin is formed in the connecting pin,
The axial center of the hollow hole is decentered toward the first circumferential position with respect to the axial center of the connection pin so that the thickness of the connection pin at the first circumferential position is reduced. The connection pin bearing structure of the link mechanism according to claim 1. A first link member in which two first bearing portions are disposed on the same axis with a predetermined gap therebetween;
A second link member having a second bearing portion;
The two first bearing portions and the second bearing portion disposed between the two first bearing portions are inserted, and the first link member and the second link member are connected to be rotatable relative to each other. In a connection pin bearing structure of a link mechanism having a connection pin,
The connecting pin is fixed to the first bearing portion by press fitting, and a hollow hole extending in the axial direction is formed,
The coupling pin bearing structure for a link mechanism, wherein the hollow hole is provided so as to be unevenly distributed in a predetermined load acting direction with respect to a center line of the coupling pin press-fitted into the first bearing portion.   The connection pin bearing structure for a link mechanism according to claim 2 or 3, wherein the hollow hole having a predetermined depth is recessed in each of both end faces of the connection pin. In the first link member, a pair of bifurcated piece portions through which the first bearing portion is formed are erected from a root portion with a predetermined gap therebetween,
The load acting direction is set in a direction from the root portion to the first bearing portion in the bifurcated piece portion,
Of the pin central portion of the connecting pin press-fitted into the first bearing portion, the barrel amount at the circumferential position on the side far from the root portion is larger than the barrel amount at the circumferential position on the root portion side. The connection pin bearing structure of the link mechanism according to any one of claims 1 to 4.   The dimple is formed in the axial direction center part of the outer peripheral surface of the pin center part which makes the said barrel shape, The connection pin bearing structure of the link mechanism in any one of Claims 1-5 characterized by the above-mentioned. The link mechanism is
An upper link connected to the piston via a piston pin;
A lower link that is rotatably mounted on a crankpin of the crankshaft and is connected to the upper link via an upper pin;
A control link connected to the lower link via a control pin;
A multi-link piston-crank mechanism of an internal combustion engine comprising:
The lower link is the first link member;
At least one of the upper link and the control link is the second link member,
The link pin bearing structure for a link mechanism according to claim 1, wherein at least one of the upper pin and the control pin is the link pin.

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