JP2008208783A - Bearing structure for link mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of a link having a forked bearing part. <P>SOLUTION: A bearing structure of a link mechanism includes a first link 100 having a forked bearing 110 arranged facing in a forked manner, and a second link 11 having a bearing part 11a placed between the forked bearing part 110. The forked bearing part 110 of the first link 100 and the bearing part 11a of the second link 11 are coupled together with a coupling pin 25. The coupling pin 25 is press fit into the forked bearing part 110 of the first link 100. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bearing structure for a link mechanism.

  A multi-link piston stroke mechanism is known as a mechanism that can change the engine compression ratio of an internal combustion engine according to the operating state (see, for example, Patent Document 1).

In this multi-link type piston stroke mechanism, a first link having a bifurcated bearing portion is rotatably connected to a crank pin, and the bifurcated bearing portion formed at one end of the first link is connected via an upper pin (connecting pin). An upper link (second link) is connected to a bifurcated bearing portion formed at the other end via a control pin (connecting pin) so that the control link (second link) can rotate freely. It is regulated by the control link. Then, by controlling the control link in accordance with the operating state and changing the inclination of the first link, the top dead center position of the piston connected to the other end of the upper link is controlled, and the variable compression ratio mechanism is realized. Is.
JP 2002-061501 A

  However, in the conventional multi-link type piston stroke mechanism described above, the connection method of the upper link / control link (second link) and the first link by the connection pin is that the connection pin is connected to both the second link and the first link. On the other hand, it was a full float system that slides. Therefore, there is a problem that the connecting pin does not act as a strength member on the first link, and the durability of the first link is lowered.

  The present invention has been made paying attention to such conventional problems, and an object thereof is to improve the durability of the first link.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides a first link (100) having a bifurcated bearing portion (110, 120) arranged to face a bifurcated shape, and a bearing portion (11a) arranged between the bifurcated bearing portion (110, 120). , 13a) and a bifurcated bearing portion (110, 120) of the first link (100) and a bearing portion (11a, 13a) of the second link (11, 13). ) Are connected by connecting pins (25, 26), and the connecting pins (25, 26) are press-fitted into the bifurcated bearing portions (110, 120) of the first link (100). It is characterized by that.

  Since the connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first link, the connecting pin acts as a strength member on the first link, and the durability of the first link is improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing an engine 1 having a multi-link type piston stroke mechanism according to an embodiment of the present invention. Hereinafter, an engine equipped with this multi-link piston stroke mechanism is referred to as a “compression ratio variable engine”.

  The variable compression ratio engine 1 connects a piston 22 and a crankshaft 21 with two links (an upper link (second link) 11 and a lower link (first link) 100) and a control link (second link) 13. To control the lower link 100 to change the compression ratio.

  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. On the other hand, the lower end of the upper link 11 is connected to one end of the lower link 100 via the upper pin 25. The other end of the lower link 100 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 100 holds the crankpin 21b of the crankshaft 21 on a crankpin bearing portion 101 formed substantially at the center. The lower link 100 swings around the crank pin 21b as a central axis. The lower link 100 can be divided into two upper and lower members, and is fixed integrally by two bolts 103 and 104.

  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 eccentric from the journal 21a by a predetermined amount, and the lower link 100 is swingably connected thereto.

  The other end of the control link 13 whose one end is connected to the lower link 100 is connected to an eccentric cam portion 15 that is eccentric from the rotation center of the control shaft 14 that is rotatably supported by the engine body. 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).

  When the compression ratio variable engine 1 increases the compression ratio, the compression ratio control actuator is driven to lower the eccentric cam portion 15 of the control shaft 14. Then, the lower link 100 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 100 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 variable compression ratio engine 1, the lower link 100 receives the combustion pressure received by the piston 22 from the upper pin 25 via the upper link 11, and operates like a lever using the control pin 26 as a fulcrum. Force is transmitted to the crankpin 21b. That is, the lower link 100 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 engine. Accordingly, since a large internal force is generated in the lower link 100, the entire lower link needs to have strength and rigidity that can withstand this.

  Therefore, in the present invention, the lower link 100 is connected to the upper pin 25 and the control pin 26 by a press-fit (press-fit) method in which the lower link 100, the upper pin 25 and the control pin 26 do not slide. Improves overall durability. Below, the structure of the pin connection part of the lower link 100, the upper pin 25, and the control pin 26 is demonstrated in detail.

  FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and shows a bearing structure of the upper pin 25. 2 is a diagram at the time of a combustion stroke, and is a diagram in a state in which a downward combustion load is acting on the upper pin 25 via the upper link 11.

  At one end of the lower link 100, as shown in FIG. 2, an upper pin bearing portion 110 that supports the upper pin 25 is formed in a bifurcated shape (substantially U-shaped). One of the opposed upper pin bearing portions 110 formed as a fork is an upper pin first bearing portion 110a and the other is an upper pin second bearing portion 110b. Each of the upper pin first and second bearing portions 110a and 110b has a substantially constant thickness, and extends parallel to each other with a space 111 therebetween (hereinafter referred to as “upper pin bearing portion valley”) interposed therebetween.

  A first pin hole 112 and a second pin hole 113 into which the upper pin 25 is press-fitted (press fit) are formed in the upper pin first and second bearing portions 110a and 110b. The first and second pin holes 112 and 113 are coaxially formed and have the same diameter.

  On the other hand, a bearing portion (hereinafter referred to as “upper pin third bearing portion”) 11 a that supports the upper pin 25 is also formed at the lower end portion of the upper link 11. A third pin hole 11b through which the upper pin 25 is inserted is formed in the upper pin third bearing portion 11a. The upper pin third bearing portion 11a has a thickness that can be disposed in an upper pin bearing portion valley 111 formed between the upper pin first and second bearing portions 110a and 110b.

  The upper pin 25 is press-fitted and fixed to the first and second bearing portions 110a and 110b of the upper pin. On the other hand, the upper link 11 and the upper link 11 are slidable with respect to the upper pin third bearing portion 11a disposed therebetween. The lower link 100 is connected.

  The upper pin 25 has a simple cylindrical surface whose outer peripheral surface has no diameter change. In the center of the upper pin 25, a cavity penetrating in the axial direction of the upper pin is formed as an oil hole 25a. Furthermore, one oil hole 25b penetrating from the oil hole 25a to the outer peripheral surface of the upper pin 25 is formed. The oil hole 25b is formed so as to come into contact with the third bearing portion 11a when the upper pin 25 is press-fitted.

  When the upper pin 25 is press-fitted into the first and second bearing portions 110a and 110b, the oil hole 25b is the inner peripheral surface of the third pin hole 11b in the link posture when the combustion load becomes maximum. It fixes so that it may face the surface which does not contact the upper pin 25 among these. Thus, by fixing the oil hole 25b so as to face the side where the combustion load does not act, the lubricating oil can be smoothly supplied to the sliding surface between the upper pin 25 and the upper link 11.

  FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1 and shows a bearing structure of the control pin 26. 3 is a diagram at the time of a combustion stroke, and is a diagram in a state where a downward tensile load by the control link 13 is acting on the control pin 26 in the drawing.

  The bearing structure of the control pin 26 is the same as the bearing structure of the upper pin 25 described in FIG. 2, and the control pin 26 is press-fitted and fixed to the control pin first and second bearing portions 120a and 120b. The control link 13 and the lower link 100 are slidably connected to the control pin third bearing portion 13a disposed therebetween.

  Similar to the upper pin 25, the control pin 26 is formed with an oil hole 26a and an oil hole 26b. The oil hole 26b is formed so as to come into contact with the control pin third bearing portion 13a when the control pin 26 is press-fitted. The control pin 26 is fixed so that the oil hole 26b faces the control shaft 14 side (downward in the figure) when being press-fitted and fixed to the control pin first and second bearing portions 120a and 120b. That is, in the link posture when the combustion load is applied, the oil hole 26b is fixed so as to face the surface of the inner peripheral surface of the third pin hole 13b that does not contact the control pin 26.

  FIG. 4 is a cross-sectional view of the lower link 100 along a plane orthogonal to the crankpin 21b.

  The lower link 100 is divided into two members along a dividing surface 102 that passes through the center of the crankpin bearing portion 101 for ease of assembly to the crankpin. Hereinafter, among the divided members, a member including the upper pin bearing portion 110 is referred to as a lower link upper 100a, and a member including the control pin bearing portion 120 is referred to as a lower link lower 100b. The lower link upper 100a and the lower link lower 100b are integrally fixed by two bolts 103, 104 disposed on both sides of the crankpin bearing portion 101.

  The bolt 103 passes through the bolt insertion hole 105 formed in the lower link lower 100b, and the tip of the bolt 103 is screwed into the female screw portion 106 formed in the lower link upper 100a. The tip of the bolt 103 protrudes into the upper pin bearing section valley 111. Thus, by projecting the tip of the bolt 103 into the upper pin bearing section valley 111, stress concentration in the vicinity of the female screw portion 106 where the tip of the bolt 103 is screwed can be suppressed as compared with the case where the tip of the bolt 103 is not projected.

  Similarly, the bolt 104 also passes through the bolt insertion hole 107 formed in the lower link upper 100a, and the tip thereof is screwed into the female screw portion 108 formed in the lower link lower 100b. In order to suppress the stress concentration at the portion where the tip of the bolt 104 is screwed, the tip of the bolt 104 protrudes into the control pin bearing section valley 121.

FIG. 5 is a diagram illustrating the input load received by the three bearing portions 101, 110, 120 of the lower link 100 during the combustion stroke. An arrow F _upper in the figure represents an input load received by the _upper pin bearing portion 110 from the _upper pin 25 and its direction. An arrow F _control in the figure represents an input load received by the control pin bearing portion 120 from the control pin 26 and its direction. An arrow F _crank in the figure represents an input load received by the crankpin bearing portion 101 from the crankpin 21b and its direction.

  As indicated by arrows in FIG. 5, the bearing portions 101, 110, 120 of the lower link 100 receive a large input load from the connection pins 21 b, 25, 26. Thereby, the upper pin bearing portion 110 and the control pin bearing portion 120 formed in a bifurcated shape are deformed as shown in FIGS. 6 and 8.

6 is a cross-sectional view taken along the line VI-VI in FIG. 5 and shows the _upper pin bearing portion 110 deformed by the input load F _upper . As a comparison, FIG. 10 shows a diagram of the _upper pin bearing portion 110 deformed by the input load F _upper when the pin connection method is a conventional connection method, that is, a full float method in which the _upper pin slides with respect to the lower link. Show. In order to prevent the drawing from being complicated, the oil holes formed in the upper pin 25 are not shown in FIGS.

The upper pin 25 receives a load F _upper from the upper link during the combustion stroke. Due to the load F _upper , the bifurcated upper pin bearing portion 110 formed in parallel so as to face the bearing central axis is compressed and deformed outward with respect to the bearing central axis. At this time, due to the deformation of the upper pin bearing portion 110, a tensile stress is generated in the vicinity of the female screw portion 106 corresponding to the base portion of the bifurcated upper pin bearing portion 110.

  Further, a large axial force is applied to the bolt 103 in advance so that the lower link upper and the lower link lower are not separated. Due to the bolt axial force, a tensile stress is generated on the lower link lower side (downward in the figure) in the female thread portion 106 into which the bolt 103 is screwed.

  Thus, in the vicinity of the female thread portion 106 into which the bolt 103 is screwed, in addition to the tensile stress due to the bolt axial force, the compressive stress input from the upper link via the upper pin 25 and the tensile stress due to the deformation of the upper pin bearing portion 110. As a result, stress amplitude is generated. Therefore, the vicinity of the female screw portion 106 is likely to be a starting point of fatigue failure.

  In order to prevent fatigue failure in the vicinity of the female thread portion 106, it is effective to reduce the stress amplitude, and it is effective to reduce the tensile stress due to the deformation of the upper pin bearing portion 110.

  Therefore, in the present invention, the upper pin 25 is press-fitted and fixed to the lower link 100 to reduce the tensile stress due to the deformation of the upper pin bearing portion 110.

  That is, in FIG. 10 showing the conventional example, the upper pin 25 slides with respect to the lower link 100, and thus does not act as a strength member. On the other hand, in FIG. 6 showing the present invention, the upper pin 25 acts as a strength member on the lower link 100 because the upper pin 25 is press-fitted and fixed to the upper pin bearing portion 110 of the lower link 100. Therefore, as compared with FIG. 10, the deformation of the upper pin bearing portion 110 is reduced, and the tensile stress generated in the vicinity of the female screw portion 106 is also reduced.

  FIG. 7 is a diagram comparing the stress amplitude generated in the vicinity of the female thread portion 106 between the conventional example and the present invention.

  According to the present invention, since the upper pin 25 is press-fitted and fixed to the upper pin bearing portion 110 of the lower link 100, the upper pin 25 acts as a strength member on the lower link 100. Therefore, as compared with the conventional example in which the upper pin 25 does not act as a strength member, the deformation of the upper pin bearing portion 110 can be suppressed, and at the same time, the tensile stress near the female screw portion 106 generated by the deformation can be reduced. Can do. Thereby, the stress amplitude generated in the vicinity of the female screw portion 106 can be reduced.

FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. 5 and shows the control pin bearing 120 that is deformed by the input load F _control . As a comparison, the control pin bearing portion 120 deformed by the input load F _control when the pin connection method shown in FIG. 11 is the connection method according to the conventional example, that is, when the control pin 26 is a full float system that slides with respect to the lower link 100. The figure of is shown. In order to prevent the drawing from being complicated, the description of the oil holes formed in the control pin 26 is omitted in FIGS.

The control pin 26 receives a load F _control from the control link during the combustion stroke. By this load F _control , the bifurcated control pin bearing portion 120 formed in parallel so as to face the bearing center axis is pulled and deformed inward with respect to the bearing center axis. At this time, due to the deformation of the control pin bearing portion 120, a compressive stress is generated in the vicinity of the female screw portion 108 corresponding to the base portion of the bifurcated control pin bearing portion 120.

  Also, a large axial force is applied to the bolt 104 in advance so that the lower link upper and the lower link lower are not separated. Due to the bolt axial force, a tensile stress is generated on the lower link upper side (upward in the figure) in the female thread portion 108 into which the bolt 104 is screwed.

  Thus, in addition to the tensile stress caused by the bolt axial force, the female screw portion 108 into which the bolt 104 is screwed is compressed by the tensile stress input from the control link via the control pin 26 and the deformation of the control pin bearing portion 120. Since stress acts, a stress amplitude is generated. Therefore, the internal thread portion 108 is likely to be a starting point for fatigue failure.

  In order to prevent fatigue failure in the female thread portion 108, it is effective to reduce the stress amplitude, and it is effective to reduce the compressive stress due to the deformation of the control pin bearing portion 120.

  Therefore, in the present invention, the tensile stress due to the deformation of the control pin bearing portion 120 is reduced by press-fitting and fixing the control pin 26 to the lower link 100.

  That is, in FIG. 11 showing the conventional example, the control pin 26 slides with respect to the lower link 100, and thus does not act as a strength member. On the other hand, in FIG. 8 showing the present invention, since the control pin 26 is press-fitted and fixed to the control pin bearing portion 120 of the lower link 100, the control pin 26 acts as a strength member on the lower link 100. Therefore, as compared with FIG. 11, the deformation of the control pin bearing portion 120 is reduced, and the compressive stress generated in the vicinity of the female screw portion 108 is also reduced.

  FIG. 9 is a diagram comparing the stress amplitude generated in the female screw portion 108 between the conventional example and the present invention.

  According to the present invention, since the control pin 26 is press-fitted and fixed to the control pin bearing portion 120 of the lower link 100, the control pin 26 acts as a strength member on the lower link 100. Therefore, compared to the conventional example in which the control pin 26 does not act as a strength member, the deformation of the control pin bearing portion 120 can be suppressed, and at the same time, the compressive stress generated in the vicinity of the female screw portion 108 can be reduced. Can do. Thereby, the stress amplitude generated in the vicinity of the female screw portion 108 can be reduced.

  According to this embodiment described above, the pin connection method is a press-fit method in which the upper pin 25 and the control pin 26 are press-fitted and fixed to the lower link 100.

  Thereby, since the upper pin 25 and the control pin 26 act as a strength member with respect to the lower link 100, the deformation of the bearing portions 110 and 120 can be suppressed. By suppressing this deformation, it is possible to improve the durability of the lower link 100 by suppressing the stress amplitude in the vicinity of the female screw portions 106 and 108 where stress concentration occurs.

  Moreover, since the upper pin 25 and the control pin 26 and the lower link 100 do not slide by being press-fitted and fixed, the thickness of the bearing portions 110 and 120 in the crank width direction can be reduced, and the crank shaft of the lower link itself can be reduced. The thickness in the direction can be reduced.

  Further, by press-fitting and fixing, a pin retaining mechanism is not required, and the thickness of the lower link itself in the crankshaft direction can be further reduced.

  Further, since the axial thickness of the lower link itself can be reduced, it is possible to prevent the upper pin bearing portion 110 from interfering with the lower end of the cylinder 20 when the lower link 100 swings up and down.

  Further, the oil hole 25b of the upper pin 25 and the oil hole 26b of the control pin 26 are fixed so that the upper pin 25 and the control pin 26 face the side opposite to the surface receiving the load from the upper link 11 and the control link 13 during the combustion stroke. can do. As a result, sufficient lubrication oil can be supplied to the sliding surfaces of the upper link 11 and the upper pin 25, and the control link 13 and the control pin 26, which tend to be insufficient, and the slidability is improved.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

It is a figure which shows the engine provided with the multi-link type piston stroke mechanism by one Embodiment of this invention. It is sectional drawing which follows the II-II line | wire of FIG. 1, and is a figure which shows the bearing structure of an upper pin. It is sectional drawing which follows the III-III line | wire of FIG. 1, and is a figure which shows the bearing structure of a control pin. It is sectional drawing of the lower link along the surface orthogonal to a crankpin. It is a figure explaining the input load which three bearing parts of a lower link receive at the time of a combustion stroke. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5, showing an _upper pin bearing portion deformed by an input load F _upper . It is the figure which compared the stress amplitude which generate | occur | produces in the internal thread part vicinity with a prior art example and this invention. FIG. 6 is a cross-sectional view taken along the line VIII-VIII in FIG. 5, showing a control pin bearing portion deformed by an input load F _control . It is the figure which compared the stress amplitude which generate | occur | produces in an internal thread part with a prior art example and this invention. It is the figure which showed the _upper pin bearing part which deform | transformed with the input load Fupper when it was set as the connection method by a prior art example. It is the figure which showed the control pin bearing part deform _| transformed with the input load _Fcontrol when it was set as the connection method by a prior art example.

Explanation of symbols

11 Upper link (second link)
11a Upper pin bearing part (bearing part)
13 Control link (second link)
13a Control pin bearing part (bearing part)
21 Crankshaft 21b Crankpin 22 Piston 24 Piston pin 25 Upper pin 25a Oil hole (first oil hole)
25b Oil hole (second oil hole)
26 Control pin 25a Oil hole (first oil hole)
25b Oil hole (second oil hole)
100 Lower link (first link)
100a Lower link upper 100b Lower link lower 101 Crank pin bearing portion 102 Dividing surface 103 Bolt (first bolt)
104 bolt (second bolt)
105 Bolt insertion hole 106 Female thread (screw hole)
107 Bolt insertion hole 108 Female thread (screw hole)
110 Upper pin bearing (bifurcated bearing)
111 Upper pin bearing valley (valley of bifurcated bearing)
120 Control pin bearing (bifurcated bearing)

Claims (4)

A first link having a bifurcated bearing portion disposed to face the bifurcated shape;
A second link having a bearing portion disposed between the bifurcated bearing portions,
A bearing structure of a link mechanism that connects the bifurcated bearing portion of the first link and the bearing portion of the second link with a connecting pin,
A bearing structure for a link mechanism, wherein the connecting pin is press-fitted into a bifurcated bearing portion of the first link. The link mechanism includes an upper link coupled to a piston via a piston pin, a lower link rotatably coupled to a crank pin of a crankshaft and coupled to the upper link via an upper pin, and the lower link A multi-link type piston stroke mechanism of an internal combustion engine capable of changing an engine compression ratio, comprising a control link coupled to the link via a control pin,
The first link is a lower link;
The second link is an upper link or a control link;
The link mechanism bearing structure according to claim 1, wherein the connecting pin is an upper pin or a control pin. The lower link includes a crankpin bearing portion into which the crankpin is fitted at substantially the center, and the lower link upper including the bifurcated bearing portion along a split surface passing through the center of the crankpin bearing portion. Divided into a lower link lower having a bifurcated bearing,
The lower link upper and the lower link lower are integrally fixed by two bolts arranged on both sides of the crank pin bearing portion,
The two bolts are
A first bolt that is inserted into a bolt insertion hole that passes through the lower link lower substantially perpendicularly to the split surface and that is screwed into a screw hole that passes through the lower link upper from the split surface toward the valley of the bifurcated bearing portion. When,
A second bolt that is inserted into a bolt insertion hole that is formed on the split surface and passes through the lower link upper and that is screwed into a screw hole that passes through the lower link lower from the split surface toward the valley of the bifurcated bearing portion. The bearing structure for a link mechanism according to claim 2. The connecting pin is
A first oil hole penetrating the central portion of the connecting pin in the connecting pin axial direction;
When the connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first link, the outer periphery of the connecting pin from the first oil hole is in contact with the inner peripheral surface of the pin hole of the bearing portion of the second link. A second oil hole penetrating toward the surface,
In the link posture when the combustion load acting on the link mechanism is maximized, the second oil hole faces the surface of the inner peripheral surface of the pin hole of the bearing portion of the first link that does not contact the connecting pin. The bearing structure for a link mechanism according to claim 2 or 3, wherein the connecting pin is press-fitted and fixed to a bifurcated bearing portion of the first link.

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