JP2010133312A - Internal combustion engine with double-link piston crank mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent poor lubrication caused by deformation of a crankpin bearing part 21 of a lower link 4. <P>SOLUTION: In the lower link 4, the crankpin bearing part 21 to which a crankpin 2 is fitted and which is disposed at an approximately the center, a pin boss part 22 for upper pin disposed at one end part, and a pin boss part 23 for control pin disposed at the other end are expanded from a thin-plate-like base plate part 26 to both sides in an axial direction. The base plate part 26 is extended to a circumference of the crankpin bearing part 21 including a direction of a maximum crankpin load F2 received by the crank pin during operation of an engine. A rib 41 axially extended from both side faces of the base plate part 26 in an axial direction of the crank pin is disposed. The rib 41 includes one end connected to the crankpin bearing 21, and disposed upstream in a direction opposite to a crankpin rotational direction R with respect to the lower link 4, with respect to a direction of the crankpin load F2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston crank mechanism of a reciprocating internal combustion engine, and more particularly to an internal combustion engine having a multi-link type piston crank mechanism.

  As a prior art in which a piston pin and a crank pin of a reciprocating internal combustion engine are connected by a multi-link type piston crank mechanism, Patent Document 1 previously proposed by the present applicant is known. This includes an upper link connected to the piston pin of the piston, a lower link connecting the upper link and the crank pin of the crankshaft, one end supported to be swingable to the engine body side, and the other end to the lower link. A control link coupled to the link. The upper link and the lower link are rotatably connected to each other via an upper pin, and the control link and the lower link are rotatably connected to each other via a control pin.

  In such a multi-link type piston crank mechanism, the lower link receives the combustion pressure received by the piston from the upper pin via the upper link, and moves to the crank pin by a kind of “lever” operation with the control pin as a fulcrum. Transmit power.

On the other hand, since the lower link needs to ensure assemblability with respect to the crankshaft, in Patent Document 1, two halves, that is, the lower link upper and the lower link along the dividing surface passing through the center of the crankpin bearing portion. The lower link lower and the lower link lower are configured to be fastened to each other with a plurality of bolts. In particular, a plurality of bolts are inserted from below, that is, from the lower link lower side, and screwed into the female screw on the lower link upper side.
JP 2004-1224776 A

  A large maximum combustion pressure received by the piston near the top dead center of the piston is input from the upper pin bearing portion to the lower link as described above via the piston pin, the upper link, and the upper pin. At the same time, a load is also generated in the crank pin bearing portion and the control pin bearing portion so that the load and the inertial force are balanced. Accordingly, the surface pressure of each bearing portion is stricter than that of a general single link type reciprocating engine, and it is required to maintain a sufficient lubrication state in order to prevent wear and seizure. In particular, a portion of the crankpin bearing that receives a predetermined crankpin load from the crankpin side, typically the maximum crankpin load at the top dead center of the piston (or its vicinity) where the maximum combustion pressure is generated, The film thickness of the lubricating oil film becomes the smallest, so that the lubricating oil film tends to disappear and wear and seizure easily occur.

  Referring to FIG. 5, the film thickness of the lubricating oil film at the crankpin bearing portion (21) is the smallest at the portion (point C) that receives the crankpin load, and increases as the distance from this portion increases. Here, in the crankpin bearing portion, the lubricating oil flows in the rotation direction (R) of the crankpin relative to the lower link so as to be dragged / wound by the rotation of the crankpin, and at the portion receiving the crankpin load (point C), Oil film pressure is generated and developed by the so-called wedge effect of the lubricating oil flowing from the upstream side in the rotational direction.

  However, if the rigidity and strength at the upstream portion (point D) in the rotational direction are weak, the film thickness becomes too large due to deformation caused by the crankpin load, so that the lubricating oil leaks from both sides in the axial direction. This causes leakage, and the oil film pressure described above is not sufficiently generated / developed, and there is a concern that the lubricity may deteriorate at the crankpin load portion (point C).

  Further, among the crankpin bearing portions, there is a concern that the lubricating oil film disappears at both ends in the axial direction and a so-called edge contact with the crankpin occurs.

  The present invention has been made in view of such problems. That is, the present invention includes an upper link having one end connected to the piston via a piston pin, a lower link connected to the other end of the upper link via an upper pin, and connected to the crank pin of the crankshaft. An internal combustion engine having a piston crank mechanism, one end of which is swingably supported on the engine body side and the other end of which is connected to the lower link via a control pin. An improved link.

  The lower link includes a base plate portion that is the main body of the lower link, and projects from the base plate portion to the both sides in the axial direction of the crank pin in the approximate center of the lower link. Crank pin bearing that receives the crank pin load from the base plate, and projects from the both sides of the base plate in the crank pin axial direction, and one end is connected to the crank pin bearing and extends linearly in the crank pin radial direction And a rib. The rib is disposed on the upstream side in the crankpin rotation direction with respect to the crankpin bearing portion in the vicinity of the crankpin bearing portion that receives a predetermined crankpin load during engine operation.

  The “predetermined crankpin load” is typically a crankpin load that is maximized during engine operation, and is generally a piston top dead center at which the maximum combustion gas pressure is generated or a crank angle in the vicinity thereof. It is the load at.

  According to such a configuration, the rib increases the rigidity and strength in the direction opposite to the crankpin rotation direction than the portion receiving the crankpin load, that is, the upstream portion in the lubricating oil flow direction. By suppressing the oil pressure, it is possible to prevent the oil film thickness from becoming excessively large, and to sufficiently generate and develop the oil film pressure to the portion receiving the crankpin load described above.

  In addition, since the base plate portion has a short axial length, the crank pin load mainly acts on the central portion of the axial length of the crank pin bearing portion from the base plate portion, and on both end portions of the crank pin bearing portion. The acting load becomes smaller. Therefore, deformation of both ends of the crankpin bearing portion can be suppressed, so-called edge contact with the crankpin can be avoided, and a load can be reliably supported at the axially central portion where the oil film pressure is high.

  In another aspect of the present invention, the crank pin bearing portion, which is substantially in the center to which the crank pin is fitted, the upper pin pin boss portion at one end holding the upper pin, and the crank pin bearing portion and the upper pin pin boss portion. A crank plate axial width is short and has at least a base plate portion extending around the crank pin bearing portion, and ribs projecting from both side surfaces of the base plate portion in the crank pin axial direction, and the rib is The crank pin bearing portion and the upper pin bearing portion are stretched linearly.

  According to the other invention, by arranging the rib at an appropriate position, that is, on the upstream side of the crankpin load direction with respect to the crankpin load direction, in addition to obtaining the above-described operational effects, the crankpin bearing portion By connecting the pin boss part for the upper pin with the rib, while securing the rigidity of this part, the distance between the centers of the crank pin bearing part and the pin boss part for the upper pin is shortened, and thus the entire lower link is reduced in size. be able to.

  According to this invention, it is possible to satisfactorily hold the lubricating oil film in the crank pin bearing portion of the lower link and prevent wear and seizure.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, an outline of a piston crank mechanism in which the lower link of the following embodiment is used will be described. FIG. 1 is a configuration explanatory view showing a configuration example in which this multi-link type piston crank mechanism is configured as a variable compression ratio mechanism. This mechanism includes a multi-link type piston crank mechanism mainly composed of a lower link 4, an upper link 5 and a control link 10.

  The crankshaft 1 includes a plurality of journal portions 2 and a crankpin 3, and the journal portion 2 is rotatably supported by a main bearing of the cylinder block 18. The crank pin 3 is eccentric from the journal portion 2 by a predetermined amount, and a lower link 4 is rotatably connected thereto. The counterweight 15 extends from the crank web connecting the journal portion 2 and the crankpin 3 to the opposite side of the crankpin 3. The lower link 4 is configured to be divided into two members as will be described later, and the crank pin 3 is fitted to a crank pin bearing portion at a substantially center.

  The upper link 5 has a lower end side rotatably connected to one end of the lower link 4 by an upper pin 6 and an upper end side rotatably connected to a piston 8 by a piston pin 7. The piston 8 receives combustion pressure and reciprocates in the cylinder 19 of the cylinder block 18.

  The control link 10 that restricts the movement of the lower link 4 is connected to the other end of the lower link 4 by a control pin 11 so as to be rotatable, and the lower end side is a cylinder block that becomes a part of the engine body via the control shaft 12. The lower part of 18 is rotatably connected. Specifically, the control shaft 12 is rotatably supported by the engine body and has an eccentric cam portion 12a that is eccentric from the center of rotation, and the lower end portion of the control link 10 is rotatable on the eccentric cam portion 12a. Is fitted. The rotation position of the control shaft 12 is controlled by a compression ratio control actuator (not shown) that operates based on a control signal from an engine control unit (not shown). Here, as shown in the figure, the cylinder 19 is arranged such that its center line m is relatively largely offset to the opposite side of the control pin 11 with respect to the rotation center of the crankshaft 1.

  In the variable compression ratio mechanism using the multi-link type piston crank mechanism as described above, when the control shaft 12 is rotated by the compression ratio control actuator, the center position of the eccentric cam portion 12a, particularly the cylinder block 18 and the like. The relative position with respect to the engine body changes. Thereby, the rocking | fluctuation support position of the lower end of the control link 10 changes. When the swing support position of the control link 10 changes, the stroke of the piston 8 changes, and the position of the piston 8 at the piston top dead center (TDC) becomes higher or lower. This makes it possible to change the engine compression ratio.

  Next, a first embodiment of the lower link 4 will be described with reference to FIGS. 2 is a front view showing the lower link, FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, and FIG. 4 is a cross-sectional view taken along line BB in FIG.

  The lower link 4 includes a crank pin bearing portion 21 at the substantially center where the crank pin 3 is fitted, an upper pin pin boss portion 22 for holding the upper pin 6, and the other end portion for holding the control pin 11. The control pin pin boss part 23 is provided. For assembly to the crank pin 3, the lower link upper 31 including the upper pin pin boss part 22 and the control pin pin boss part along the split surface 24 passing through the center of the crank pin bearing part 21. And a lower link lower 32 including 23, which are integrally fastened by two bolts 33 and 34 (see FIG. 1) respectively disposed on both sides of the crankpin bearing portion 21. If the cylinder 19 is arranged in the vertical direction, the lower link upper 31 is located on the upper side and the lower link lower 32 is located on the lower side in the crankcase, and the bolts 33 and 34 are both crankcases. It can be tightened from below. The crank pin 3 is rotatably supported in the pin hole 22 a of the crank pin bearing portion 21 via a bearing metal 25.

  As shown in FIG. 3, the pin hole 22 a of the upper pin pin boss portion 22 has a bifurcated shape. Both ends of the upper pin 6 in the axial direction are fixed by press-fitting, and one end of the upper link 5 is located inside the bifurcated portion. The pin bosses are combined in a rotatable manner. Similarly, the control pin pin boss portion 23 having a pin hole 23a into which the control pin 11 is rotatably inserted is formed in a bifurcated shape, and the pin boss portion at one end of the control link 10 is rotated inside the bifurcated portion. Can be combined.

  Each of the two bolts 33 and 34 passes through a bolt insertion hole (not shown) on the lower link lower 32 side, and the tip part is screwed into a female screw part (not shown) formed in the lower link upper 31. Match.

  The lower link 4 mainly includes a thin plate-like base plate portion 26, and the bearing portion 21 and the pin boss portions 22 and 23 protrude from the base plate portion on both sides in the axial direction. That is, the base plate portion 26 has a thickness (wall thickness) D1 in the crank pin axis direction shorter than the bearing portion 21 and the pin boss portions 22 and 23, and the axial direction of the bearing portion 21 and the pin boss portions 22 and 23 is set. Connected to the center. Therefore, as shown in FIG. 3, the thinned base plate portion 26 has a recess between the upper pin pin boss portion 22 and the crank pin bearing portion 21 so as to separate both axial ends. 35 is formed. Similarly, a recess 36 is also formed between the crank pin bearing portion 21 and the control pin pin boss portion 23. Further, the outer peripheral edge portion 27 of the lower link 4 extends in a flange shape on both sides in the crankpin axial direction from the base plate portion 26 over the entire periphery, and the outer peripheral edge portion 27 is configured to transmit a load.

  As shown in FIG. 2, in such a lower link 4, an upper pin load (vector) F1 is applied from the upper pin 6 side to the upper pin pin boss portion 22 due to a large maximum combustion pressure received by the piston 8, and the like. It is input via the link 5 and the upper pin 6. At the same time, a crankpin load F2 is generated from the crankpin 3 side to the crankpin bearing portion 21 side, and a control pin load F3 is generated from the control pin 11 side to the control pin pin boss portion 23 side so that the load F1 and the inertial force are balanced. To do. That is, the crankpin bearing portion 21 receives the crankpin load F2 from the crankpin during engine operation. FIG. 2 shows loads (vectors) F1 to F3 in the link geometry at the crank angle at the piston top dead center (or the vicinity thereof) where the maximum combustion pressure is generated.

  In this embodiment, the lower link upper 31 is provided with ribs 41 (41 </ b> A) projecting from both side surfaces of the base plate portion 26 in the crankpin axis direction. The rib 41 has one end connected to the crankpin bearing portion 21 and a predetermined crankpin load received by the crankpin bearing portion 21, more specifically, as shown in FIG. With respect to the direction of the maximum crankpin load F2 generated at the crank angle of the piston top dead center (or the vicinity thereof) generated, the piston is disposed in the direction opposite to the crankpin rotation direction R with respect to the lower link 4 and upstream.

  That is, the rib 41 (41A) is a crankpin in the vicinity of a crankpin bearing that receives a crankpin load at or near the piston top dead center where the maximum combustion pressure is generated, which is a predetermined crankpin load during engine operation. It arrange | positions in the upstream of the crankpin rotation direction with respect to a bearing part. The rib 41 extends linearly from the crankpin bearing portion 21 in the radial direction, and forms a predetermined acute angle α in a direction opposite to the crankpin rotation direction R with respect to the direction of the maximum crankpin load F2. . In particular, in the first embodiment, the rib 41A is more than the upper pin pin boss part 22 because the extension line F2 'of the crank pin load F2 is set to intersect / overlap the upper pin pin boss part 22. At a position deviating in the opposite direction / upstream side of the rotation direction R (clockwise direction in FIG. 2), it is stretched linearly between the crankpin bearing portion 21 and the outer peripheral edge portion 27.

  In the other second to fourth embodiments shown in FIG. 6B and FIGS. 7 to 9, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted as appropriate. ing. However, regarding the rib 41, “A to D” is appropriately added after the reference sign “41” when it is necessary to distinguish each of the embodiments.

  In the second embodiment shown in FIG. 6B, the upper link center extension line F1 ′ passing through the piston pin 7 and the upper pin 6 at the piston top dead center at which the loads F1 to F3 are maximum, that is, the maximum upper pin load F1. The link geometry is set so that the direction F1 ′ of the crankshaft bearing portion 21 does not intersect the crankpin bearing portion 21. The rib 41B is located upstream of the maximum crank pin load F2 in the rotational direction R and at a position disengaged closer to the rotational direction R than the upper pin pin boss portion 22, and the crank pin bearing portion 21 and the outer peripheral edge portion 27 It is stretched in a straight line.

  In the third embodiment shown in FIG. 7, the rib 41 </ b> C is spanned between the crank pin bearing portion 21 and the upper pin pin boss portion 22. That is, the rib 41 </ b> C connects the two 21 and 22. In the fourth embodiment shown in FIGS. 8 and 9, the width of the rib 41D is enlarged as compared with the third embodiment. As a result, as will be described later, the crank pin bearing portion 21 and the pin boss for the upper pin are used. It is possible to achieve compactness by shortening the center-to-center distance L4 from the portion 22, and further to improve the strength and rigidity against the shear stress F4 in the vicinity of the female thread portion 37 of the bolt 33 on the upper pin side.

  Next, characteristic configurations and operational effects of the present invention will be listed with reference to the above embodiments.

  (1) The piston crank mechanism 1 for an internal combustion engine according to the present invention is connected to an upper link 5 having one end connected to a piston 8 via a piston pin 7 and to the other end of the upper link 5 via an upper pin 6. And a lower link 4 connected to the crankpin 3 of the crankshaft 1, a control link having one end pivotably supported on the engine body side and the other end connected to the lower link 4 via a control pin 11. 10. In such a multi-link type piston crank mechanism 1, the piston stroke characteristics and the upper link lower end (upper pin 6) trajectory are set as compared with the single link type piston crank mechanism in which the piston pin and the crank pin are connected by a single link. Since there is a degree of freedom, etc., making the setting appropriate makes it possible to improve the durability and reliability of the piston 8 and cylinder 19 by increasing the piston stroke and reducing the thrust-anti-thrust load. Can be achieved.

  The lower link 4 protrudes to both sides of the base plate portion 26 and the crank plate axial direction from the base plate portion 26, and the crank pin bearing portion 21 at the substantially center where the crank pin 3 is fitted, and both sides of the base plate portion 26. Ribs 41 (41A to 41D) projecting from the surface in the direction of the crankpin axis. The base plate portion 26 extends around the crankpin bearing portion 21 including the direction of a predetermined crankpin load F2 received from the crankpin 3 side during engine operation. One end of the rib 41 is connected to the crankpin bearing portion 21 and is disposed on the upstream side in the direction opposite to the crankpin rotation direction R with respect to the lower link 4 with respect to the direction of the crankpin load F2. ing.

  In this way, by extending the axially thin base plate portion 26 around the crankpin bearing portion 21 including the direction of the crankpin load F2, the upper pin pin boss portion 22 has a bifurcated shape as shown in FIG. Even in this case, the load mainly acts on the central portion of the axial length of the crankpin bearing portion 21 via the base plate portion 26, and the load acting on both ends of the crankpin bearing portion 21 is Get smaller. Therefore, deformation at both ends of the crankpin bearing portion 21 is suppressed, so-called edge contact with the crankpin 3 is avoided, and a load can be reliably supported at the axially central portion where the oil film pressure is high.

  And the said rib 41 can suppress the bearing deformation | transformation in the entrainment site | part of a lubricating oil film, and can develop a lubricating oil film favorably. This point will be described with reference to FIG. FIG. 5B is a developed view of the outer peripheral shaft surface 3a of the crankpin 3 and the inner peripheral bearing surface 21a of the crankpin bearing portion 21 shown in FIG. Further, the bearing surface 21a 'in (b) is a reference example when there is no rib. As shown in the figure, in the portion C that receives the crankpin load F2, the film thickness of the shaft surface 3a and the bearing surface 21a 'is minimized, and the film thickness increases as the distance from the portion C increases. Here, in the portion C that receives the crankpin load F2, the lubricating oil flows from the upstream portion in the rotational direction R of the crankpin 3 with respect to the lower link 4 so as to be dragged / involved by the rotation of the crankpin 3, Oil film pressure is generated and developed by the wedge effect.

  However, since the periphery of the crankpin bearing portion 21 is thinned by the base plate portion 26 as described above, the rigidity and strength at the portion D on the upstream side in the rotational direction are sufficiently ensured in the reference example without ribs. The film thickness becomes too large due to the deformation of the bearing surface 21a ′ caused by the crankpin load F2, and so-called side leakage that the lubricating oil leaks from both sides in the axial direction is likely to occur. For this reason, the oil film pressure to the portion C receiving the crankpin load cannot be sufficiently generated and developed, and there is a risk of causing wear and seizure.

  On the other hand, by providing the rib 41 in the portion D on the upstream side in the rotational direction R from the portion C that receives the crankpin load F2, the portion on the upstream side in the rotational direction R compared to the reference example in which no rib is provided. The rigidity of D can be increased, the deformation of the bearing surface 21 can be suppressed, and the increase in the oil film thickness can be suppressed. That is, the oil film thickness of the upstream portion in the rotational direction R leading to the portion C receiving the crankpin load F2 can be made uniform. As a result, the amount of side leakage is suppressed, the oil film pressure is sufficiently generated and developed in the portion C that receives the crankpin load F2, the contact between the shaft surface 3a and the bearing surface 21a is relaxed, and the bearing load resistance is increased. The performance can be improved, and the bearing structure in the lower link can be simplified and made compact.

  (2) The specific shape of the rib 41 extends linearly from the crankpin bearing 21 in the radial direction and is opposite to the crankpin rotation direction R with respect to the direction of the crankpin load F2. Has an acute angle α. As a result, the rib 41 has a simple linear shape while effectively increasing the rigidity of the upstream portion D (FIG. 5) in the direction of the crankpin load F2 in the crankpin bearing portion 21, so that stress concentration is hardly caused. Processing and manufacturing are also easy.

  (3) The upper pin pin boss portion 22 at one end holding the upper pin 6 protrudes from the base plate portion 26 on both sides in the crank pin axial direction, that is, is thickened in the axial direction. In the third and fourth embodiments shown in FIGS. 7 to 9, the ribs 41 </ b> C and 41 </ b> D are spanned between the crank pin bearing portion 21 and the upper pin pin boss portion 22.

  Here, as in the first embodiment, if the link geometry is set such that the direction of the crank pin load F2 of the crank pin bearing portion 21 intersects the upper pin pin boss portion 22, the rib and the upper pin pin boss portion are When the pin bearing portion is connected, the rigidity at this portion becomes excessively high, and the edge contact at the crank pin bearing portion is likely to occur, and the bearing durability may be reduced. Therefore, as shown in FIGS. 7 and 9, when the crank pin bearing portion 21 and the upper pin pin boss portion 22 are connected by the ribs 41C and 41D, the ribs 41C and 41D rotate with respect to the crank pin load F2. The link geometry is set so as to be the upstream position in the direction R.

  Thus, by connecting the crank pin bearing portion 21 and the upper pin pin boss portion 22 with the ribs 41C and 41D, the concave portion 35 (see FIG. 2) between the two 21 and 22 can be eliminated or omitted. The rigidity is increased, and as shown in FIG. 8, the center-to-center distance L4 between the crank pin bearing portion 21 and the upper pin pin boss portion 22 can be shortened, and as a result, the entire lower link can be reduced in size. . In addition, when the concave portion is provided, the shortening of the center distance L4 is limited due to the processing of the concave portion, but such a limitation is not caused by the omission of the concave portion. realizable.

  (4) The outer peripheral edge portion 27 of the lower link 4 protrudes on both sides in the crank pin axial direction from the base plate portion 26, that is, is thicker in the axial direction than the base plate portion 26. In the first and second embodiments shown in FIGS. 2 to 6, the ribs 41 </ b> A and 41 </ b> B are spanned between the crankpin bearing portion 21 and the outer peripheral edge portion 27. As a result, the rigidity of the crankpin bearing portion 21 is improved, and the crankpin load F2 can be satisfactorily transmitted to the outer peripheral edge portion 27 via the ribs 41A and 41B.

  (5) In the second to fourth embodiments of FIG. 6B and FIGS. 7 to 9, the upper link center extension line F1 ′ passing through the piston pin 7 and the upper pin 6 at the top dead center of the piston, that is, the upper pin 6 side. The link geometry is set so that the direction of the upper pin load F <b> 1 acting on the upper pin pin boss portion 22 does not intersect with the crank pin bearing portion 21. When the upper link center extension line F1 ′ intersects the crankpin bearing portion 21 as in the first embodiment shown in FIG. 6A, the crankpin bearing portion 21 is deformed by the upper pin load F1 from the upper pin. As shown in an exaggerated manner by the broken line 21b, it becomes large, and the crankpin load F2 from the crankpin acts on a portion where the amount of deformation is large. On the other hand, as shown in FIG. 6B, the upper link center extension line F1 ′ does not intersect the crankpin bearing portion 21, that is, the upper pin load F1 from the upper pin is not directed toward the crankpin bearing portion 21. As shown in an exaggerated manner by the broken line 21c, the deformation of the crankpin bearing portion 21 is reduced, and the crankpin load F2 acts in a direction in which the oil film thickness decreases in a portion away from the deformation portion. The deformation of the crank pin bearing portion 21 is suppressed, the lubricating oil film is satisfactorily retained, and the contact of the bearing portion is alleviated.

  (6) The lower link 4 includes an upper pin pin boss portion 22 at one end holding the upper pin 6 and a control pin pin boss portion 23 at the other end holding the control pin 11 and is assembled to the crankshaft 1. In order to ensure the performance, the lower link upper 31 including the upper pin pin boss portion 22 and the lower link lower 32 including the control pin pin boss portion 23 are divided along the dividing surface 24 passing through the center of the crank pin bearing portion 21. The lower link upper 31 and the lower link lower 32 are fastened by at least two bolts 33 and 34 that are configured and arranged on both sides of the crankpin bearing portion 21.

  In such a configuration, it is difficult to ensure the strength and rigidity against the shearing stress F4 and the like generated in the vicinity of the female thread portion 37 while securing the bolt fastening force, and the size of the lower link is inevitably increased. In particular, as shown in FIG. 9, when the upper pin loads F1 and F2 are inclined with respect to the direction orthogonal to the dividing surface 24, the component in the direction to be displaced along the dividing surface 24 becomes large. It is difficult to ensure the strength and rigidity in the vicinity of the female screw portion 37.

  Therefore, as shown in FIG. 9, the rib 41 is formed in the lower link upper 31, and at least the bolt 34 near the pin boss portion 22 for the upper pin passes through the lower link lower 32 among the two bolts 33 and 34. Suppose that it is screwed into the female thread portion 37 formed in the lower link upper 31. That is, the female thread portion 37 is set in the vicinity of the rib 41 provided on the lower link upper 31, and in particular, in the fourth embodiment of FIG. 9, the female thread portion 37 extends toward the rib 41D and its tip. The link geometry is set and the size of the rib 41D is increased so that the portion reaches the rib 41D. With such a configuration, it is possible to improve the strength and rigidity of the distal end portion of the female thread portion 37 where the shear stress F4 is generated, and to achieve both the securing of the bolt fastening force and the downsizing of the lower link.

  (7) As shown in FIG. 3, the pin boss portion 22 for the upper pin has a bifurcated shape in which both end portions of the upper pin 6 are fixed by press-fitting. Thus, by fixing both ends of the upper pin 6 to the upper pin pin boss portion 22 by press-fitting, the lower link can be made compact in the axial direction because there is no sliding surface, and the strength can be improved by improving the link rigidity. it can. Further, by fixing both ends of the upper pin 6 to the upper pin pin boss part 22, it is difficult to cause relative rotation of the upper pin 6 with respect to the lower link 4, that is, inward rotation. The same applies to the pin boss portion 23 side for the control pin.

  Further, in the fourth embodiment shown in FIG. 9, the distance L4 between the centers of the crank pin bearing portion 21 and the upper pin pin boss portion 22 is shortened. The center-to-center distance L2 with the pin boss portion 23 can be made equal, and the crank pin bearing portion 21, the upper pin pin boss portion 22 and the control pin pin boss portion 23 are arranged on the same line, and the lower link is Since the structure is substantially symmetrical, stress concentration on the upper pin pin boss portion 22 and the control pin pin boss portion 23 is reduced with respect to the loads F1 to F3. Therefore, the upper pin 6 and the control pin 11 Therefore, the axial dimension of the lower link can be shortened.

  (8) Further, by using the control shaft 12 provided with the eccentric cam portion 12a and the like, the swing fulcrum position of the control link 10 on the engine body side is changed, so that the piston crank mechanism 1 can be easily used as a variable compression ratio mechanism. Can be configured.

Structure explanatory drawing which shows the example of the piston crank mechanism in which a lower link is used. The front view which shows 1st Example of the lower link which concerns on this invention. Sectional drawing which follows the AA line of FIG. Sectional drawing which follows the BB line of FIG. Explanatory drawing which shows the bearing part (a) of a crankpin, and its expansion | deployment figure (b). Explanatory drawing which exaggerates and shows a deformation | transformation of the crankpin bearing part which concerns on 1st Example (a) and 2nd Example (b). The front view which shows the lower link which concerns on 3rd Example. The front view which shows the lower link which concerns on 4th Example. The front view which similarly shows the lower link which concerns on 4th Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 ... Lower link 21 ... Crank pin bearing part 22 ... Upper pin pin boss part 23 ... Control pin pin boss part 24 ... Dividing surface 26 ... Base plate part 27 ... Outer peripheral edge part 31 ... Lower link upper 32 ... Lower link lower 41 (41A-41D) …rib

Claims (9)

An upper link having one end connected to the piston via a piston pin, a lower link connected to the other end of the upper link via an upper pin, and connected to the crank pin of the crankshaft, and one end on the engine body side An internal combustion engine comprising: a control link supported so as to be swingable and having the other end connected to the lower link via a control pin;
The lower link is
A base plate that is the main part of the lower link;
A crankpin bearing portion that protrudes to both sides in the crankpin axial direction from the base plate portion at substantially the center of the lower link front view, and receives the crankpin load from the crankpin when the crankpin is fitted and the engine is operating,
A rib projecting from the both side surfaces of the base plate portion in the crankpin axial direction, one end connected to the crankpin bearing portion, and a rib extending linearly in the crankpin radial direction;
The internal combustion engine according to claim 1, wherein the rib is disposed upstream of the crankpin bearing portion in the crankpin rotation direction in the vicinity of the crankpin bearing portion that receives a predetermined crankpin load during engine operation.   2. The internal combustion engine according to claim 1, wherein the rib has an acute angle with respect to a direction of the predetermined crankpin load in a direction opposite to the crankpin rotation direction. The lower link has an upper pin boss portion that protrudes from the base plate portion on both sides in the crank pin axial direction and holds the upper pin.
The internal combustion engine according to claim 1 or 2, wherein the rib is stretched over the crank pin bearing portion and the upper pin pin boss portion. The lower link has an outer peripheral edge portion projecting on both sides in the crankpin axial direction from the base plate portion in the vicinity of the outer periphery in front view,
The internal combustion engine according to claim 1 or 2, wherein the rib is stretched between the crank pin bearing portion and an outer peripheral edge portion.   The link geometry is set so that the upper link center extension line passing through the piston pin and the upper pin at the time of piston top dead center does not intersect with the crankpin bearing portion. Internal combustion engine. The lower link includes an upper pin pin boss part at one end holding the upper pin, and a control pin pin boss part at the other end holding the control pin.
A lower link upper including the upper pin pin boss part and a lower link lower including the control pin pin boss part are configured to be divided along a split surface passing through the center of the crank pin bearing part.
The lower link upper and the lower link lower are fastened by at least two bolts arranged on both sides of the crankpin bearing portion,
The rib is formed on the lower link upper,
Further, of the two bolts, at least a bolt near the pin boss portion for the upper pin passes through the lower link lower and is screwed into a female screw portion formed in the lower link upper. Item 6. The internal combustion engine according to any one of Items 1 to 5.   7. An upper pin pin boss portion for holding the upper pin, and the upper pin pin boss portion has a bifurcated shape in which both end portions of the upper pin are fixed by press-fitting. The internal combustion engine described in 1.   The internal combustion engine according to any one of claims 1 to 7, wherein the piston crank mechanism constitutes a variable compression ratio mechanism by changing a swing fulcrum position of the control link on the engine body side. An upper link having one end connected to the piston via a piston pin, a lower link connected to the other end of the upper link via an upper pin, and connected to the crank pin of the crankshaft, and one end on the engine body side An internal combustion engine comprising: a control link supported so as to be swingable and having the other end connected to the lower link via a control pin;
The lower link is
Lower link front view substantially center crankpin bearing portion to which the crankpin is fitted,
An upper pin pin boss portion at one end holding the upper pin;
A base plate portion having a shorter crank pin axial width than the crank pin bearing portion and the upper pin pin boss portion, and extending at least around the crank pin bearing portion;
Ribs projecting in the direction of the crankpin axis from both side surfaces of the base plate portion,
An internal combustion engine characterized in that the rib is stretched linearly between the crank pin bearing portion and the upper pin bearing portion.

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