JP5205991B2 - Link mechanism bearing structure - Google Patents

Description

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

  As a mechanism capable of changing the engine compression ratio of the internal combustion engine according to the operating state, for example, a link connecting a piston and a crankshaft as described in Patent Document 1, and a link for controlling the attitude of these links There is known a multi-link type piston stroke mechanism comprising: Specifically, a lower link having a bifurcated bearing portion is rotatably connected to the crank pin, and an upper link is connected to the bifurcated bearing portion integrally formed with the lower link via an upper pin (connection pin). A control link is rotatably connected to the bifurcated bearing portion formed at the end via a control pin (connection pin), and the operation of the lower link is restricted by this control link. And, by controlling the control link according to the operating condition and changing the inclination of the lower 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. It is.

  Here, since the connecting pin is a full float type that slides with respect to both of the links to be connected, it is necessary to provide a region for processing a locking groove at both ends in the axial direction of the pin boss provided in the bifurcated bearing portion. In other words, the length of the connecting pin must be shortened compared to the total length of the pin boss. Therefore, there is a problem that the contact area with the pin boss portion at both ends of the connecting pin is reduced, the surface pressure is increased accordingly, and the stress condition becomes severe.

In order to solve this problem, a connecting pin having a small diameter portion at both ends is used, and a separate collar member is press-fitted into the bifurcated bearing portion in a state where the small diameter portion is arranged. Patent Document 2 discloses a full-float connection structure that increases a contact area with pin bosses at both ends.
JP 2002-061501 A JP 2003-247524 A

  However, in the connection structure of Patent Document 2, the boss portion of the bifurcated bearing is deformed when the collar member is press-fitted, and the center axis of the press-fit portion is displaced with respect to the press-fitting load direction. If the surface becomes non-uniform in the circumferential direction and a combustion load or the like is applied, there is a possibility that the portion with a high contact pressure cannot withstand the stress.

  On the other hand, when the press-fitting allowance is reduced, the deformation of the boss portion can be suppressed, but problems such as the inversion and dropping of the collar member occur.

  In addition, since the connecting pin is a full float system that slides with respect to both the collar member (bifurcated bearing) and the link member to be connected, the connecting pin does not act as a strength member of the link having the bifurcated bearing. There is also a problem that the durability of the resin is lowered.

  The present invention has been made paying attention to the problems described above, and aims to suppress the deformation of the bifurcated bearing portion and improve the durability of the link member having the bifurcated bearing in the bearing structure of the link mechanism. And

The bearing structure of the link mechanism of the present invention includes a first member having a bifurcated bearing portion in which two bearing portions are arranged to face each other in a bifurcated manner, and a second member having a bearing portion disposed between the bifurcated bearing portions. with the door, Ru bearing structure der link mechanism connecting bifurcated bearing portion of the first member and a bearing portion of the second member by a connecting pin. The connecting pin has a double structure in which the inner connecting pin and the outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape. In addition, the outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side while being inserted into the bearing portion of the first member, and the diameter expanding. It has become. Furthermore, the press-fitting allowance of the inner connecting pin to the outer connecting pin is a press-fitting allowance at a position corresponding to the outer side surface of the bearing portion of the first member when the inner connecting pin and the outer connecting pin are press-fitted into the bifurcated bearing portion of the first member. Rb, and Rb is a press-fitting allowance at a position corresponding to the approximate center of each bearing portion of the first member, and Rb is a press-fit allowance at a position corresponding to the inner side surface of the bearing portion of the first member. >Rc> Ra.

  According to the present invention, the outer connecting pin is in a state where the inner connecting pin is press-fitted to increase the diameter and is press-fitted and fixed to the bifurcated bearing portion. That is, when the inner connecting pin is not press-fitted, the bifurcated bearing portion is not deformed when the outer connecting pin is inserted into the bifurcated bearing portion. In addition, when the inner connecting pin is press-fitted, the outer connecting pin already inserted functions as a strength member of the bifurcated bearing portion, so that deformation of the bifurcated bearing portion can be suppressed.

  After the inner connecting pin is press-fitted, the connecting pin composed of the inner connecting pin and the outer connecting pin is press-fitted and fixed to the first link, and functions as a strength member of the bifurcated bearing portion. There is no problem of such durability degradation.

  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 the piston 22 and the crankshaft 21 with two links (an upper link (second member) 11 and a lower link (first member) 100), and a control link (second member) 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. As will be described later, the control pin 26 has a double structure including an inner control pin (inner connection pin) 26a and an outer control pin (outer connection pin) 26b.

  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 main body of the engine 1. 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 1. 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. Hereinafter, the structure of the pin connecting portion between the lower link 100 and the control pin 26 will be described in detail.

  2A and 2B are views showing the bearing structure of the control pin 26, where FIG. 2A is an enlarged view around the connecting portion between the lower link 100 and the control pin 26, and FIG. 2B is a cross section taken along the line II-II in FIG. FIG.

  At one end of the lower link 100, a control pin bearing portion 120 that supports the control pin 26 is formed in a bifurcated shape as shown in FIG. One of the opposed control pin bearing portions 120 formed in a bifurcated shape is a first control pin bearing portion 120a, and the other is a second control pin bearing portion 120b. The first and second control pin bearing portions 120a and 120b each have a substantially constant thickness, and extend in parallel with each other with a space 121 (hereinafter referred to as “control pin bearing portion valley”) therebetween.

  The control pin 26 first inserts the hollow cylindrical outer control pin 26b into the control pin first and second control pin bearing portions 120a and 120b. Here, a value obtained by subtracting the inner diameters of the first and second control pin bearing portions 120a and 120b from the outer diameter of the outer control pin 26b (hereinafter referred to as press-fitting allowance) is substantially zero. Then, with the outer control pin 26b inserted, the inner control pin 26a is press-fitted inside the outer control pin 26b.

  Thus, since the press-fitting allowance with respect to the first and second control pin bearing portions 120a and 120b of the outer control pin 26b is substantially zero, the outer control pin does not cause deformation of the first and second control pin bearing portions 120a and 120b. 26b can be inserted (a state in which the press-fitting allowance is almost zero is referred to as light press-fitting). Then, by press-fitting the inner control pin 26a into the outer control pin 26b, the diameter of the outer control pin 26b is expanded, and the press-fitting allowance for the first and second control pin bearing portions 120a and 120b of the outer control pin 26b is increased. As a result, the press-fit effect is increased, and there is no risk of the outer control pin 26b rotating or dropping off. Further, since the inner control pin 26a is press-fitted while the outer control pin 26b is lightly press-fitted, the outer control pin 26b functions as a strength member for the first and second control pin bearing portions 120a and 120b, and the inner control pin 26a. The deformation of the first and second control pin bearing portions 120a and 120b when press-fitting can be suppressed.

  By the way, as shown in FIG. 3, the press-fitting allowance of the inner control pin 26a to the outer control pin 26b is A, which is the portion corresponding to the outer side surface of the first and second control pin bearing portions 120a, 120b after insertion. B is the portion corresponding to the inner side, C is the portion corresponding to the inner side surface, D is the portion corresponding to both side surfaces of the control pin bearing portion 13a, and E is the portion corresponding to the central portion. , Rb, Rc, Rd, Re, Rb> Rc> Ra and Re> Rd. Then, the outer diameter of the inner control pin 26a is set so that the size of the press-fitting allowance has such a relationship. The reason why the press-fitting allowance is adjusted by the outer diameter of the inner control pin 26a is that the processing of the outer diameter of the inner control pin 26a is easier than the processing of the inner diameter of the outer control pin 26b. It can also be adjusted by machining the inner diameter of the outer control pin 26b. FIG. 3 is a view similar to FIG.

  At the time of press-fitting, the stress in the vicinity of the connecting portion end face (A and C portions) in FIG. 3 tends to be higher than that at the central portion (B portion), but by setting the press-fitting allowance to Rb> Rc> Ra, And the durability reliability of the connecting portion is improved.

  In general, when a pin is press-fitted into a bifurcated bearing portion such as the first and second control pin bearing portions 120a and 120b, the diameter of the pin is reduced at the press-fitted portion, and the central portion has a maximum diameter between the bearing portions. It transforms into a barrel shape. This deformation causes a one-sided contact or the like.

  On the other hand, in the connecting portion by the connecting pin, the oil film pressure of the lubricating oil becomes maximum near the center of the connecting portion, and decreases as the end portion is approached.

  Therefore, by making the press-fit allowance Re> Rd, the deformation to the barrel shape is increased, and the surface pressure due to the contact between the outer control pin 26b and the control link 13 is increased in the vicinity of the center where a sufficient oil film pressure can be secured. The surface pressure is lowered at the end face (D portion) where the pressure is lowered.

  Thereby, problems such as one-sided contact can be avoided, the sliding characteristics between the control pin 26 (outer control pin 26b) and the control link 13 can be improved, and effects such as reduction of friction and prevention of burn-in can be obtained.

  The connecting portion between the lower link 100 and the upper link 11 also has the same configuration and press-fit allowance distribution as those in FIGS. 2 and 3 described above. That is, the upper pin 25 has a double structure composed of the inner upper pin 25a and the outer upper pin 25b. The distribution of the press-fitting allowance of the inner upper pin 25a with respect to the outer upper pin 25b in the major axis direction is also the outer control pin of the inner control pin 26a of the control pin 26. The distribution is the same as the press fitting allowance for 26b.

  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. These input loads are mainly those in which the combustion load is transmitted via the piston 22, the upper link 11, or the like. FIG. 6 is an enlarged view around the control pin bearing portion 120 of FIG.

  Since the load input from the control pin 26 is in the lower right direction in the figure, the portion of the control pin bearing portion 120 in the load direction with respect to the central axis of the inner control pin 26a (enclosed by a broken line in FIG. 5) A high load is applied to the region L). That is, this region L is subjected to such a combustion load in addition to the stress generated by press-fitting the inner control pin 26a. Therefore, higher strength is required than other regions.

  However, the region L must be thinner than the other regions in order to avoid interference with other parts during engine operation. Therefore, it is difficult to ensure strength by increasing the wall thickness.

Therefore, in the region Lin in the vicinity of the intersection between the outer periphery of the inner control pin 26a and the F _control direction, the press-fitting allowance of the inner control pin 26a with respect to the outer control pin 26b is made smaller than other regions. Thereby, the stress generated by press-fitting the inner control pin 26a in the region Lin is reduced, and the total load acting on the region L when the combustion load is applied is reduced. Therefore, even if the area | region L is thin, sufficient intensity | strength can be ensured with respect to the load which acts.

FIG. 7 is a diagram illustrating the input load received by the three bearing portions 101, 110, 120 of the lower link 100 during the exhaust stroke. The arrow F _upper , arrow F _control , and arrow F _crank in the figure are the same as those in FIG. These input loads are mainly due to inertia loads of the piston 22 and the upper link 11 and the like. FIG. 8 is an enlarged view around the upper pin 25 of FIG.

  The load input from the upper pin 25 is at the upper right in the figure, and a high load is applied to the region U surrounded by the broken line of the upper pin bearing portion 110. That is, in addition to the stress generated by press-fitting the inner upper pin 25a, this region U is further subjected to such an inertial load. Therefore, higher strength is required than other regions. However, similarly to the region L, the region U must be thinner than other regions in order to avoid interference with other parts.

Therefore, in the region Uin in the vicinity of the intersection between the outer periphery of the inner _upper pin 25a and the F _upper direction, the press-fitting allowance of the inner pin 265a with respect to the outer upper pin 25b is made smaller than other regions. Thereby, similarly to the region L described above, the region U can ensure sufficient strength against the applied load even if the wall thickness is thin.

  The outer upper pin 25b is formed of a material having a smaller elastic coefficient than the inner upper pin 25a and the upper pin bearing portion 110. Since the inner upper pin 25a and the upper pin bearing portion 110 have a dimensional deviation or misalignment within a tolerance range, the inner upper pin 25a is press-fitted into the upper pin bearing portion 110 without the outer upper pin 25b. The surface pressure becomes uneven. When the surface pressure becomes non-uniform in this way, there arises a problem that stress is concentrated on a portion where the surface pressure is high.

  However, if the elastic coefficient of the outer upper pin 25b is made lower than that of the inner upper pin 25a and the upper pin bearing portion 110 as described above, and the outer upper pin 25b is interposed between the inner upper pin 25a and the upper pin bearing portion 110, the outer Since the deformation amount of the upper pin 25b is larger than the deformation amount of the inner upper pin 25a and the upper pin bearing portion 110, the dimensional deviation between the inner upper pin 25a and the upper pin bearing portion 110 can be absorbed and the surface pressure can be made close to uniform.

As described above, in the present embodiment, the following effects can be obtained.
(1) A bearing disposed between the lower link 100 having the first and second control pin bearing portions 120a and 120b disposed in a bifurcated manner and the first and second control pin bearing portions 120a and 120b. A control link 13 having a portion 13a, a bearing structure of a link mechanism for connecting the first and second control pin bearing portions 120a, 120b and the bearing portion 13a of the control link 13 with a control pin 26, The control pin 26 has a double structure in which the inner control pin 26a and the outer control pin 26b are coaxially arranged on at least one of the first and second control pin bearing portions 120a and 120b, and the outer control pin 26b. Are the first and second control pin bearing portions 120a of the lower link 100, Since the inner control pin 26a is press-fitted to the inner peripheral side in the state inserted through 20b and the diameter is expanded, the first and second control pin bearing portions 120a and 120b are press-fitted and fixed. When the outer control pin 26b is lightly press-fitted into the first and second control pin bearing portions 120a and 120b, the first and second control pin bearing portions 120a and 120b are not deformed. Further, when the inner control pin 26a is press-fitted, the outer control pin 26b that has already been lightly press-fitted functions as a strength member, so that deformation of the first and second control pin bearing portions 120a and 120b can be suppressed. . After the inner control pin 26a is press-fitted, the control pin 26 including the inner control pin 26a and the outer control pin 26b is press-fitted and fixed to the lower link 100, and the first and second control pin bearing portions 120a, Since it functions as a 120b strength member, there is no problem of lowering durability as in the full float method.
(2) The press-fitting allowance of the inner control pin 26a to the outer control pin 26b is the outer side surface of the bearing portion when the inner control pin 26a and the outer control pin 26b are press-fitted into the first and second control pin bearing portions 120a and 120b. The press-fitting allowance at a position corresponding to is Ra, the press-fitting allowance at a position corresponding to approximately the center of the bearing portion is Rb, and the press-fitting allowance at a position corresponding to the inner side surface of the bearing portion 13a of the lower link 100 is Rc. Sometimes, since Rb>Rc> Ra, it is possible to reduce the stress at the center portion where the stress tends to be high.
(3) By changing the outer diameter of the inner control pin 26a in accordance with the position of the inner control pin in the central axis direction, the size relationship of the press-fitting allowance of the inner control pin 26a with respect to the outer control pin 26b is realized. Processing is easier than processing the inner circumference of 26b to realize the magnitude relationship.
(4) Out of the periphery of the bearing portion of the lower link 100, the region L in the vicinity of the portion in the direction of the action of the load input to the lower link 100 via the control pin 26 near the combustion top dead center position In comparison, since the press-fitting allowance of the inner control pin 26a to the outer control pin 26b is small, the stress generated by press-fitting the inner control pin 26a in the region L is reduced, and the total force acting on the region L when a combustion load is applied. The load is reduced. Therefore, even if the area | region L is thin, sufficient intensity | strength can be ensured with respect to the load which acts.
(5) Of the peripheral edge of the bearing portion of the lower link 100, the region U in the vicinity of the portion in the direction of the action of the load input to the lower link 100 via the upper pin 11 near the exhaust top dead center position is compared with other portions. Since the press-fitting allowance of the inner upper pin 25a to the outer upper pin 25b is small, the total load acting on the region U when the inertial load is applied is reduced. Therefore, even if the region U is thin, sufficient strength can be secured against the acting load.

  A second embodiment will be described.

  The basic configuration of this embodiment is the same as that of FIGS. 1 and 2, but the press-fitting allowance of the inner control pin 26a to the outer control pin 26b is different. Here, it is assumed that the press-fit allowance between the E part and the D part shown in FIG. 3 is Re <Rd.

  As described above, when a connecting pin is press-fitted into a bifurcated bearing portion, the connecting pin has a characteristic of deforming into a barrel shape between the bearing portions. Therefore, the difference between Re and Rd is set so that the outer diameter distribution of the outer control pin 26b between the first and second control pin bearing portions 120a and 120b becomes substantially constant after press-fitting.

  The difference between Re and Rd varies depending on the material and diameter of the inner and outer pins 26a and 26b used, the distance between the first and second control pin bearing portions 120a and 120b, and the like.

  As described above, by setting the press-fitting allowances Re and Rd as Re <Rd, the outer diameter of the outer control pin 26b after press-fitting becomes substantially constant, so that both ends of the sliding portion of the outer control pin 26b are uniform. The load will be applied. Thereby, the deterioration of sliding characteristics can be suppressed.

  A third embodiment will be described.

  FIG. 9 is a view showing the bearing structure of the control pin 26 of the present embodiment, and is a cross-sectional view taken along the line II-II of FIG. 1 as in FIG.

  This embodiment is different from the first embodiment in that the inner control pin 26a is divided into two parts. The lengths in the center axis direction of the two inner control pins 26a are substantially equal to the lengths in the center axis direction of the first and second control pin bearing portions 120a and 120b, respectively.

  The inner control pins 26a are press-fitted from the left side in the drawing on the first control pin bearing portion 120a side and from the right side in the drawing on the second control pin bearing portion 120b side, that is, from the outer end surface of the bearing portion, respectively. To do.

  After the inner control pin 26a is press-fitted, the outer control pin 26b is press-fitted in the first and second control pin bearing portions 120a and 120b, and there is no risk of rotation or dropping. Further, the inner control pin 26a is lighter by the amount corresponding to the absence of the control pin bearing valley 121 portion. Furthermore, since the inner control pin 26a is press-fitted independently by the first and second control pin bearing portions 120a and 120b, the press-fitting work is facilitated.

  A fourth embodiment will be described.

  FIG. 10 is a diagram schematically showing a multi-link type piston stroke mechanism to which the present embodiment is applied. The configuration in which the piston 22 and the crankshaft 21 are connected via the upper link 11 and the lower link 100 and the inclination of the lower link 100 is controlled via the control link 13 is the same as that shown in FIG.

  However, the rotation axis of the crankshaft 21 is offset from the center of the cylinder bore, and the counterweight outermost diameter portion of the crankshaft 21 intersects the extension line in the axial direction of the piston pin central axis in the vicinity of the bottom dead center. As shown in FIG. 12, the dimensions of the links 11, 13, 100 are such that the trajectory of the upper pin 25 when the shaft rotates is an ellipse that is long in the cylinder axis direction on the crankshaft rotation axis side with respect to the cylinder bore center. Set.

  FIG. 11 is a view of the state when the piston 22 is located at the bottom dead center in the double link type piston stroke mechanism of FIG. 10 as viewed from the engine side.

  By offsetting the rotation shaft of the crankshaft 21 from the center of the cylinder bore, the lowest point of the locus of the upper pin 25 is lowered to almost the same as the lowest point of the locus of the crankpin 21b as shown in FIG. In this case, when the shape of the skirt 22a of the piston 22 is a general shape as shown in FIG. 1, the counterweight of the crankshaft 21 and the skirt 22a of the piston 22 interfere with each other near the bottom dead center. Therefore, in order to avoid interference with the counterweight, the width of the skirt 22a of the piston 22 in the crankshaft rotation axis direction is narrowed as shown in FIG. Further, since the extension line in the axial direction of the central axis of the piston pin intersects the outermost diameter portion of the counterweight 21c in the vicinity of the bottom dead center, the axial length of the piston pin 24 is compared with a general piston shape. shorten. That is, the distance between the first piston pin bearing portion 130a and the second piston pin bearing portion 130b is smaller than that in the case of a general piston shape, and is provided at a position near the center of the piston 22.

  Since the trajectory of the upper pin 25 is offset from the center of the cylinder bore, the thrust force acting on the piston 22 does not reverse according to the rotation of the crankshaft 21 and is in one direction.

  FIG. 13 is a view showing the bearing portion of the upper pin 25 as in FIG. Similar to the control pin 26, the upper pin 25 has a double structure comprising an inner upper pin 25a and an outer upper pin 25b. After the outer upper pin 25b is lightly press-fitted into the first and second upper pin bearing portions 110a and 110b, the inner upper pin 25 The upper pin 25 is press-fitted and fixed to the first and second upper pin bearing portions 110a and 110b by press-fitting 25a into the outer upper pin 25b.

  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 formed by press-fitting the inner upper pin 25a into the outer upper pin 25b in a state where the outer upper pin 25b is lightly press-fitted into the first and second bearing portions 110a and 110b, thereby the upper pin first and second bearing portions 110a. , 110b is press-fitted and fixed. On the other hand, the upper link 11 and the lower link 100 are slidably connected to the upper pin third bearing portion 11a disposed therebetween.

  As described above, the swing angle of the upper link 11 is reduced by making the locus of the upper pin 25 into a substantially oval shape long in the cylinder direction. That is, the angular velocity when the upper pin 25 swings is reduced.

  The combustion load acting on the piston 22 becomes maximum at about 10 to 20 degrees after the top dead center, and continues to act until the in-cylinder pressure becomes sufficiently low. If the locus of the upper pin 25 is substantially oval as described above while the combustion load is applied, the upper link 11 receives the combustion load with almost no angle change, so that the piston pin 24 and the upper link 11 slide. The speed is substantially zero and the lubrication characteristics are improved. Therefore, although the piston pin 24 is press-fitted into the piston (insertion coupling configuration), it is possible to suppress the occurrence of scuffing or the like in the sliding portion of the piston pin 24.

  FIG. 14 is a view showing the bearing portion of the piston pin 24. This is basically the same as the bearing structure of the upper pin 25. Similarly to the upper pin 25, the piston pin 24 has a double structure comprising an inner piston pin 24a and an outer piston pin 24b. With the outer piston pin 24b lightly press-fitted into the first and second piston pin bearing portions 130a and 130b, The inner piston pin 24a is press-fitted and fixed by press-fitting the outer piston pin 24b. The outer piston pin 24b is divided into two parts and is fixed to the first and second piston pin bearing portions 130a and 130b, respectively.

  In this manner, the piston pin 24 is press-fitted and fixed to the first and second piston pin bearing portions 130a and 130b, whereby the piston pin 24 acts as a reinforcing member for the first and second piston pin bearing portions 130a and 130b.

  By the way, as described above, the interval between the first and second piston pin bearing portions 130a and 130b is shorter than that in the case of a general piston shape, and each is provided at a position close to the center. In this case, the piston is supported at a position closer to the center of the piston than the piston having a general shape, and the deformation of the piston crown surface is increased, that is, the rigidity against the combustion load is reduced. Further, when the piston pin is supported by the full float method, an increase in the piston weight will be caused if an attempt is made to ensure rigidity.

  However, since the piston pin 24 acts as a reinforcing member when the piston pin 24 is press-fitted and fixed to the piston 22, a decrease in rigidity can be suppressed without increasing the piston weight.

  A cavity penetrating in the axial direction of the piston pin is formed as an oil hole 24c in the center of the inner piston pin 24a. In addition, a single oil hole 24d that penetrates from the substantially central portion in the axial direction of the oil hole 24c to the outer peripheral surface of the inner piston pin 24a is formed. The inner piston pin 24a is press-fitted so that the oil hole 24d faces upward in the cylinder bore central axis direction.

  Since the combustion load acts downward on the center axis of the cylinder bore with respect to the piston 22, the contact stress of the lower portion in the drawing becomes high on the sliding surface between the inner piston pin 24 a and the upper link 11. Therefore, the lubricating oil can be smoothly supplied from the oil hole 24d to the sliding surface between the inner piston pin 24a and the upper link 11. The lubricating oil supplied from the oil hole 24d is supplied from the oil hole 24c. Lubricating oil ejected from an oil hole provided in a crankshaft in a general engine is supplied to the oil hole 24c by the same action as that naturally supplied to an oil hole provided at the upper end of a connecting rod small end. The

  Note that the outer piston pin 24b may be integrated in the same manner as the outer control pin 26b of FIG. In this case, it is necessary to provide the outer piston pin 24b also with an oil hole communicating with the oil hole 24d, and press-fit the inner piston pin 24a so that these oil holes communicate with each other.

  FIG. 15 is a diagram illustrating an example of another configuration of the piston pin 24. As shown in FIG. 15, the outer piston pin 24b is disposed only in one of the first and second piston pin bearing portions 130a and 130b, and the inner piston pin 24a is connected to the first piston pin bearing portion 130a or the second piston pin 24a. You may make it press-fit directly in either of the 2 piston pin bearing parts 130b. According to this, it is possible to suppress deformation of the piston 22 when the piston pin 24 is press-fitted while reducing the number of parts.

  FIG. 16 is a diagram showing an example of another configuration of the outer piston pin 24b. When the outer piston pin 24b is divided into two as in FIG. 14, the outer piston pin 24b is arranged on the outer periphery of the outer piston pin 24b as shown in FIG. The taper angle is provided so that the thickness in the radial direction is increased. Accordingly, when the outer piston pin 24b is inserted from the right side in FIG. 16, the positioning of the piston pin 24 in the central axis direction is facilitated and workability is improved.

  17A is a view of the piston 22 as viewed from below, and FIG. 17B is a cross-sectional view taken along line xvi-xvi of FIG.

  A hole for press-fitting the piston pin 24 of the first and second piston pin bearing portions 130a and 130b is a piston pin hole 131, and a thrust force acting direction line passing through the central axis 131a of the piston pin hole 131 is TH. When the distance from the center axis 131a to the intersection of the thrust force acting direction line TH on the side where the thrust force is input and the first and second piston pin bearing portions 130a, 130b is L1, the other distance is L2. In addition, the periphery of the piston pin hole 131 of the first and second piston pin bearing portions 130a and 130b is formed so that L1> L2. That is, the thickness of the periphery of the piston pin hole 131 on the side where the thrust force is input with respect to the central shaft 131a is made thicker than the thickness on the opposite side.

  FIG. 18 is a diagram showing a state of deformation of the first and second piston pin bearing portions 130a and 130b when a thrust force is input to the piston 22, and FIG. When the thickness is equal, (b) is a diagram showing a case where the thickness on the side where the thrust force is input is made thicker than the thickness on the opposite side.

  Comparing (a) and (b) of FIG. 18, the case where the wall thickness on the side where the thrust force is input is relatively thicker than the case where the wall thickness around the piston pin hole 131 is equal, The deformation of the piston pin hole 131 due to the thrust force is small. That is, even when a thrust force is input, the piston pin hole 131 can be maintained in a nearly circular state. This is because the rigidity on the side where the thrust force is input is increased by increasing the thickness.

  When the piston pin hole 131 is deformed each time a thrust force is input, slight wear occurs between the piston pin hole 131 and the piston pin 24 press-fitted and fixed thereto. However, as described above, the minute wear can be suppressed by relatively increasing the thickness of the peripheral edge of the piston pin hole 131 on the side where the thrust force is input to suppress the deformation. Durability can be improved.

  In addition, as shown in FIG. 19, the thrust force input side can also be reduced by making the piston pin bearing portion interval S1 on the side where the thrust force is input smaller than the piston pin bearing portion interval S2 on the opposite side. The rigidity can be increased and the same effect can be obtained.

As described above, in the present embodiment, the following effects can be obtained.
(1) Connect each link so that the cylinder bore center axis and the crankshaft rotation axis are offset, and the outermost diameter portion of the counterweight 21c intersects the extension line in the axial direction of the piston pin 24 near the bottom dead center. In the arranged link mechanism, since the piston pin 24 is press-fitted and fixed to the first and second piston pin bearing portions 130a and 130b, the piston pin 24 acts as a rigid member, thereby increasing the weight of the piston 22. The deformation of the crown surface can be suppressed without incurring.
(2) When viewed from the front of the engine, the upper link 11 swings in the left or right range with respect to the center axis of the cylinder bore as the crankshaft 21 rotates, so that the thrust force input direction is constant. The thickness of the periphery of the bearing portion of the piston 22 is thicker on the opposite side to the range where the upper link 11 swings with respect to the center axis of the cylinder bore than on the same side. The deformation of the pin hole 131 can be suppressed and kept in a substantially circular shape, thereby preventing the internal rotation of the piston pin 24.
(3) The length of the first and second piston pin bearing portions 130a and 130b in the direction of the piston pin central axis is opposite to the range in which the upper link 11 swings with respect to the cylinder bore central axis from the same side. Therefore, the deformation of the first and second piston pin bearing portions 130a and 130b when the inner piston pin 24a is press-fitted can be suppressed and kept in a substantially circular shape. This facilitates press-fitting work.
(4) The press-fitting allowance of the inner piston pin 24a to the outer piston pin 24b is the vicinity of the portion in the direction of the action of the load input to the upper link 11 via the piston pin 24 near the combustion top dead center position. Therefore, the press-fitting allowance of the portion where the stress tends to be high when subjected to a combustion load is small. Thereby, stress can be reduced and durability can be improved.
(5) The outer piston pin 24b is divided into two in the direction of the central axis of the outer piston pin, and only the first and second piston pin bearing portions 130a and 130b have a double structure, and the outer peripheral surface of each outer piston pin 24b is Since the outer piston pin 24b is tapered such that the radial thickness of the outer piston pin 24b is larger on the outer peripheral side than on the piston center side, the outer piston pin 24b is easily positioned.
(6) Since the piston pin 24 has oil holes 24c and 24d formed of a cavity penetrating in the axial direction and a cavity penetrating from a substantially central portion in the axial direction of the cavity to the outer peripheral surface in the piston crown surface direction. When the combustion load is applied, the portion where the contact stress increases and the opening of the oil hole 24d do not overlap. Therefore, even when a combustion load is applied, the lubricating oil can be reliably supplied to the sliding portion.
(7) Since the outer piston pin 24b has a smaller elastic coefficient than the inner piston pin 24a and the first and second piston pin bearing portions 130a, 130b, it is possible to make the stress generated when press-fitted and fixed uniformly approach. The internal rotation of the piston pin 24 can be prevented.

  A fifth embodiment will be described.

  This embodiment is basically the same configuration as the fourth embodiment, and the shape of the piston 22 is different.

  20A is a view of the piston 22 as viewed from below, and FIG. 20B is a cross-sectional view along the xviii-xviii line of FIG. 20A, in which a thrust force is input from the central shaft 131a. The distance L1 to the intersection of the thrust force acting direction line TH and the first and second piston pin bearing portions 130a, 130b is greater than the other distance L2.

  As shown in FIG. 20 (a), in the piston 22 of the present embodiment, one skirt 22a (left side in the figure) is wider in the circumferential direction than the other skirt 22a (right side in the figure). For example, when the offset amount between the rotation axis of the crankshaft 21 and the center of the cylinder bore is larger than in the case of FIG. 17 and the interference with the counterweight 21c is only one skirt 22a, such a skirt shape can be formed. it can. The skirt 22a on the side where the thrust force is input is made wider.

  FIG. 21 is a view showing a state of deformation of the first and second piston pin bearing portions 130a and 130b when the piston pin 24 is press-fitted. FIG. In this case, (b) is a diagram showing a case where the thickness of the skirt 22a on the wide circumferential side is thicker than the narrow side.

  When the thickness of the periphery of the piston pin hole 131 is uniform as shown in FIG. 21A, the rigidity of the periphery of the piston pin hole 131 is lower on the wide side of the skirt 22a than on the narrow side. For this reason, when the piston pin 24 is press-fitted, the tensile deformation is increased on the side having low rigidity, and the press-fitting operation becomes difficult.

  On the other hand, when the thickness of the periphery of the piston pin hole 131 having the wider circumferential width of the skirt 22a is relatively thick as shown in FIG. 21B, the rigidity of the thickened portion is increased. Therefore, deformation at the time of press-fitting can be suppressed. Thereby, press fitting can be made easy.

  As shown in FIG. 22, the circumferential width of the skirt 22a can also be reduced by making the piston pin bearing portion interval S1 on the side of the skirt 22a wider in the circumferential direction smaller than the piston pin bearing portion interval S2 on the narrower side. The rigidity of the periphery of the piston pin hole 131 on the wide side can be increased, and the same effect can be obtained.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a figure which shows the engine provided with the multi-link type piston stroke mechanism by 1st Embodiment. It is a figure which shows the connection part of a control link and a lower link, (a) is the figure seen from the engine front, (b) is the figure seen from the engine side. It is a figure for demonstrating a press fitting allowance. 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. It is a figure for demonstrating the press injection allowance of a control pin bearing part. It is a figure explaining the input load which three bearing parts of a lower link receive at the time of an exhaust stroke. It is a figure for demonstrating the press fitting allowance of an upper pin bearing part. It is a figure which shows another example of the connection part of a control link and a lower link. It is a figure which shows the engine provided with the multi-link multi-link type piston stroke mechanism of 2nd Embodiment. It is a figure which shows the relationship between the piston and counterweight in a bottom dead center. It is a figure for demonstrating the locus | trajectory of an upper pin. It is a figure which shows the connection part of an upper link and a lower link. It is sectional drawing of the connection part of a piston and an upper pin. It is sectional drawing which shows the other example of the connection part of a piston and an upper pin. It is a figure for demonstrating the shape of an outer side piston pin. It is the figure (the 1) for demonstrating the shape of a piston pin bearing part, (a) is the figure seen from the downward | lower direction, (b) is sectional drawing which follows the XVI-XVI line of (a). It is a figure for demonstrating a deformation | transformation of the piston pin bearing part when thrust force acts, (a) is the case where the thickness of a periphery is constant, (b) is the thickness of the part into which thrust force is input. It is a figure which shows the case where it is hot. It is FIG. (2) for demonstrating the shape of a piston pin bearing part. It is a figure (the 3) for demonstrating the shape of a piston pin bearing part, (a) is the figure seen from the downward | lower direction, (b) is sectional drawing which follows the XVIII-XVIII line of (a). It is a figure for demonstrating a deformation | transformation of the piston pin bearing part at the time of press-fitting an inner side piston pin, (a) is the thickness of the periphery, and (b) is the thickness of the part into which thrust force is input It is a figure which shows the case where is hot. It is FIG. (4) for demonstrating the shape of a piston pin bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Upper link 11a Upper pin bearing part 13 Control link 13a Control pin bearing part 21 Crankshaft 22 Piston 24 Piston pin 25 Upper pin 26 Control pin 100 Lower link 110 Upper pin bearing part 111 Upper pin bearing part Valley 120 Control pin bearing part 130 Piston pin bearing part

Claims (17)

A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member and the diameter thereof being increased. and it has become a state,
The press-fitting allowance of the inner connecting pin to the outer connecting pin is a position corresponding to the outer side surface of the bearing portion of the first member when the inner connecting pin and the outer connecting pin are press-fitted into the bifurcated bearing portion of the first member. The press-fitting allowance at the position corresponding to the inner side of the bearing portion of the first member is Rb, and the press-fit allowance at the position corresponding to the inner side surface of the bearing portion of the first member is Rc. Sometimes, the bearing structure of the link mechanism , wherein Rb>Rc> Ra . A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member and the diameter thereof being increased. and it has become a state,
The press-fitting allowance of the inner connecting pin to the outer connecting pin is a press-fitting allowance at a position corresponding to the end of the sliding surface between the outer connecting pin and the second member, and a position corresponding to the substantially central portion of the sliding surface. A bearing structure for a link mechanism , wherein Rd> Re, where Re is a press-fitting allowance in A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member and the diameter thereof being increased. and it has become a state,
The press-fitting allowance of the inner connecting pin to the outer connecting pin is a press-fitting allowance at a position corresponding to the end of the sliding surface between the outer connecting pin and the second member, and a position corresponding to the substantially central portion of the sliding surface. A bearing structure for a link mechanism , wherein Re> Rd, where Re is a press-fitting allowance . 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 a 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 stroke mechanism for an internal combustion engine comprising:
The first member and the second member are a lower link, an upper link, or a control link, respectively.
The bearing structure for a link mechanism according to any one of claims 1 to 3, wherein the connecting pin is an upper pin or a control pin. The inner connecting pin is divided into two in the inner connecting pin central axis direction, and only the two bearing portions of the first member have a double structure,
The bearing part structure of a link mechanism according to any one of claims 1 to 4 , wherein each inner connecting pin is press-fitted into the outer connecting pin from an outer side surface direction of two bearing parts of the first member. By varying the outer diameter of the inner coupling pin according to the position of the inner coupling pin central axis, we claim 1, characterized in that to realize the magnitude of press-fitting margin relative to the outer coupling pins of the inner coupling pin To 5. The link mechanism bearing structure according to any one of items 1 to 5 . The first member is the lower link;
The second member is the upper link or the control link;
Bearing structure of the link mechanism according to any one of claims 1 to 6, characterized in that said connecting pin is in the upper pin or the control pin. A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member and the diameter thereof being increased. It is in a state that
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 a crankshaft and is connected to the upper link via an upper pin;
A control link connected to the lower link via a control pin;
With
The first member is the lower link;
The second member is the control link;
The connecting pin is an upper pin or the control pin;
Of the bearing portion periphery of the lower link, the vicinity of the portion in the direction of the action of the load input to the lower link via the control pin near the combustion top dead center position is closer to the inner connection pin than other portions. A bearing structure for a link mechanism , wherein a press-fitting allowance for the outer connecting pin is small . A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member and the diameter thereof being increased. It is in a state that
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 a crankshaft and is connected to the upper link via an upper pin;
A control link connected to the lower link via a control pin;
With
The first member is the lower link;
The second member is the upper link;
Of the bearing periphery of the lower link, the vicinity of the portion in the direction of action of the load input to the lower link via the upper pin near the exhaust top dead center position is closer to the inner connecting pin than the other portions. A bearing structure for a link mechanism, wherein a press-fitting allowance for the outer connecting pin is small . A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin is press-fitted and fixed to the bifurcated bearing portion of the first member by the inner connecting pin being press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member and the diameter thereof being increased. It is in a state that
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 a crankshaft and is connected to the upper link via an upper pin;
A control link connected to the lower link via a control pin;
With
The links are arranged such that the cylinder bore center axis and the crankshaft rotation axis are offset, and the counterweight outermost diameter portion of the crankshaft intersects the extension line in the axial direction of the piston pin near the bottom dead center And
When viewed from the front of the engine, the upper link swings in the left or right range with respect to the center axis of the cylinder bore as the crankshaft rotates. The double link type piston stroke mechanism of the internal combustion engine on the opposite side to the range where the upper link swings with respect to the shaft is thicker than the same side,
The first member is a piston;
The second member is an upper link;
A bearing structure for a link mechanism, wherein the connecting pin is a piston pin . Circumferential length of the skirt portion of the piston, the range in which the upper link with respect to the cylinder bore center axis swings towards the opposite side, according to claim 10, wherein longer than the same side Link mechanism bearing structure. Piston pin length in the central axial direction of the bearing portion of said piston, according to claim 10 and a range where the upper link with respect to the cylinder bore center axis swings towards the opposite side, characterized in longer than the same side Or the bearing structure of the link mechanism of 11 . The press-fitting allowance of the inner connecting pin to the outer connecting pin is such that the vicinity of the portion in the direction of action of the load input to the upper link via the piston pin near the combustion top dead center position is compared to the other portions. The bearing structure for a link mechanism according to any one of claims 10 to 12 , wherein the bearing structure is small. The outer connecting pin is divided into two in the outer connecting pin central axis direction, and only two bearing portions of the first member have a double structure,
13. The outer peripheral surface of each outer connecting pin is tapered so that the radial thickness of the outer connecting pin is larger on the outer peripheral side than on the piston center side. The bearing structure of the link mechanism as described in one. The connecting pin is a piston pin, and has an oil hole formed of a cavity penetrating in the axial direction and a cavity penetrating from a substantially central portion in the axial direction of the cavity to the outer peripheral surface in the piston crown surface direction. The bearing structure for a link mechanism according to any one of claims 10 to 14 . A first member having a bifurcated bearing portion in which two bearing portions are arranged to be bifurcated, and
A second member 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 member and the bearing portion of the second member with a connecting pin,
The connecting pin has a double structure in which an inner connecting pin and an outer connecting pin are coaxially arranged on at least one of the bearing portions arranged in a bifurcated shape,
The outer connecting pin has a smaller elastic coefficient than the inner connecting pin and the bearing portion, and the inner connecting pin is press-fitted to the inner peripheral side in a state where the outer connecting pin is inserted into the bearing portion of the first member, thereby increasing the diameter. Thus, the bearing structure of the link mechanism is in a state of being press-fitted and fixed to the bifurcated bearing portion of the first member . The link mechanism is claimed in claim 4 or 10, wherein the control by the link posture changing a variable compression ratio mechanism able to change the engine compression ratio by controlling the piston top dead center position Link mechanism bearing structure.

Images