JP2017198073A - Lubrication structure of double link type piston-crank mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve lubrication performance of a wall surface of a cylinder with which a piston slidably contacts during engine start.SOLUTION: A double link type piston-crank mechanism 10 includes: a piston 13 which slides in a cylinder 20; a lower link 12 which is rotatably attached to a crank pin 11A of a crank shaft 11; and an upper link 14 in which one end is rotatably connected with the piston 13 through a piston pin 16 and the other end is rotatably connected with the lower link 12 through a connection pin 17. An oil sump 28, in which lubrication oil is stored during engine stop, is provided at the lower link 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lubrication structure for a multi-link piston-crank mechanism.

  As a device capable of changing the engine compression ratio of an internal combustion engine, a variable compression ratio mechanism using a multi-link type piston-crank mechanism is known as disclosed in Patent Document 1 and the like. The variable compression ratio mechanism includes a lower link rotatably attached to a crank pin of a crankshaft, and an upper link connecting the lower link and the piston, and one end of the control link connected to the lower link. By changing the support position of the other end, the engine compression ratio can be changed with changes in the piston top dead center position and bottom dead center position.

JP 2004-116434 A

  When the piston slides, such as when starting at low temperatures after being left for a long period of time, it is required to ensure the lubrication performance of the cylinder wall surface. Generally, the oil jet is used to inject and supply lubricating oil to the sliding surface. It has become.

  However, the multi-link piston-crank mechanism has a structure in which a large number of parts such as an upper link, a lower link, and a control link are rotatably connected using a connecting pin or the like. In addition, there are a large number of bearing portions around the connecting pins that require lubrication performance. For this reason, it is difficult to supply sufficient lubricating oil to the sliding surface between the piston and the cylinder, particularly at the time of starting the engine, and improvement of the lubricating performance has been desired.

  The present invention has been made in view of such circumstances, and an object thereof is to improve the lubrication performance of the sliding surfaces of the piston and the cylinder at the time of starting the engine in the multi-link type piston-crank mechanism.

  A multi-link piston-crank mechanism according to the present invention includes a piston that slides in a cylinder, a lower link that is rotatably attached to a crankpin of a crankshaft, and one end that is rotatable with the piston via a piston pin. The upper link is connected to the lower link via the connecting pin and is rotatably connected to the lower link. The lower link is provided with an oil reservoir for storing lubricating oil when the engine is stopped. The oil reservoir is disposed in the oil reservoir along with the rotation of the crankshaft when the engine is started from the engine stopped state. The lubricating oil stored in is scattered on the wall surface of the cylinder.

  According to the present invention, the lubricating oil is stored in the oil sump portion of the lower link when the engine is stopped, and the lower link swings with the rotation of the crankshaft when the engine is started, so that the lubricating oil in the oil sump portion is It is scattered by centrifugal force and sprayed onto the cylinder wall where the piston slides. As a result, it is possible to improve the lubrication performance of the cylinder wall surface when the internal combustion engine having the multi-link piston-crank mechanism is started.

Sectional drawing which shows the variable compression ratio mechanism using the multilink type piston-crank mechanism based on 1st Example of this invention. Explanatory drawing which shows the link attitude | position in the vicinity of a piston top dead center (B) and piston bottom dead center (C) at the time of the engine stop in the said multiple link type piston-crank mechanism. Sectional drawing which shows the connection part of the upper link and lower link in the said multiple link type piston-crank mechanism. The perspective view which expands and shows the said connection part. The perspective view which shows the structure by the side of the lower link in the said connection part. The perspective view which fractures | ruptures and shows the structure of the lower link side in the said connection part similarly. The perspective view which shows the structure by the side of the lower link in the connection part of the upper link and lower link which concern on 2nd Example of this invention. The perspective view which shows the structure by the side of the lower link in the connection part of the upper link and lower link which concern on 3rd Example of this invention. The perspective view which partially fractures | ruptures and shows the structure of the lower link side in the connection part of the upper link and lower link which concern on 4th Example of this invention. The perspective view which partially fractures | ruptures and shows the structure of the lower link side in the connection part of the upper link and lower link which concern on 5th Example of this invention.

  Hereinafter, the present invention will be described with reference to illustrated embodiments. First, a variable compression ratio mechanism 10 using a multi-link type piston-crank mechanism will be described with reference to FIG.

  The variable compression ratio mechanism 10 has a lower link 12 rotatably attached to a crankpin 11A of a crankshaft 11 of an internal combustion engine, an upper link 14 that connects the piston 13 and the lower link 12, and one end of the lower link 12. And a control link 15 that is rotatably mounted. The piston 13 and the upper link 14 are rotatably connected by a piston pin 16 that passes through the piston 13 and the upper link 14, and the upper link 14 and the lower link 12 are rotatably connected by a connecting pin 17 that passes through both the control link 15. And the lower link 12 are rotatably connected by a control pin 18 that is inserted therethrough.

  The piston 13 is disposed in the cylinder 20 of the cylinder block 19 so as to be movable up and down, and slides in the cylinder 20 in the cylinder axial direction. A control shaft 21 is rotatably supported on the cylinder block 19 in parallel with the crankshaft 11. The control shaft 21 is provided with an eccentric shaft portion 21A that is eccentric from the center of rotation, and the other end of the lower link 12 is rotatably attached to the eccentric shaft portion 21A.

  By changing the rotational position of the control shaft 21 by a variable compression ratio actuator such as a motor (not shown), the constraint condition of the lower link 12 by the control link 15 is changed, and the top dead center position and the bottom dead center position of the piston 13 are changed. With this change, the engine compression ratio changes. Therefore, by controlling the operation of the variable compression ratio actuator by a control unit (not shown), the engine compression ratio can be controlled according to the engine operating state.

  An oil jet 22 is provided in the cylinder block 19 in the vicinity of the lower end portion of the cylinder 20. The oil jet 22 injects and supplies the lubricating oil supplied from the main gallery 23 that is a lubricating oil passage formed inside the cylinder block 19 toward the back side of the crown surface of the piston 13, thereby When the engine speed is about 2000 rpm or more, the built-in valve is opened and lubricating oil is always injected. The injection nozzle 24 of the oil jet 22 has a shape extending from the oil jet main body to the side and then upward so as not to interfere with the skirt portion 13A of the piston 13.

  Next, with reference to FIGS. 2-6, the lubricating structure of the connection part of the upper link 14 and the lower link 12 by the connection pin 17 which comprises the principal part of 1st Example of this invention is demonstrated. In FIG. 2, the oil jet is omitted.

  As shown in FIG. 3, a cylindrical first pin boss portion 25 through which the connecting pin 17 passes is integrally formed at the lower end portion of the metal upper link 14. On the other hand, the metal lower link 12 is similarly formed with a through hole 26 </ b> A through which the connecting pin 17 passes, and the thin plate-like second pin boss part 26 arranged parallel to each other on both axial sides of the first pin boss part 25. Are integrally formed. That is, the pair of second pin boss portions 26 sandwiches the first pin boss portion 25 in the axial direction.

  And the opposing surface of a pair of 2nd pin boss | hub parts 26 which oppose on both sides of the said 1st pin boss | hub part 25, and the circular-arc-shaped bottom face 27 which connects the edge parts of the root part of the opposing surface of these 2nd pin boss | hub parts 26, Thus, an oil sump 28 forming the main part of the present embodiment is defined. The oil reservoir portion 28 has an arcuate shape so as to avoid interference with the other end of the swinging upper link 14.

  The lower link 12 is composed of a pair of divided members 12A and 12B (see FIG. 1) that sandwich the crankpin 11A, and a pair of bolts 29 for fastening the pair of divided members 12A and 12B to the bottom surface 27. One tip of is exposed. The lower link 12 is formed with an oil passage 30 that connects the bearing surface 31 of the crankpin 11A and the bottom surface 27. Through this oil passage 30, the lubricating oil in the oil reservoir 28 is transferred to the crankpin. The crank pin bearing surface 31 of the lower link 12 that is in sliding contact with the outer peripheral surface of 11A is supplied.

  An alternate long and short dash line 32 </ b> A in the drawing indicates the shape of the bottom surface according to the comparative example when the bottom surface 27 is formed as a substantially flat surface. In contrast to such a comparative example, in this embodiment, the protruding portion 32 in the vicinity of the outer edge of the lower link 12 is protruded toward the upper link 14 to form an oil reservoir portion 28 that can store lubricating oil when the engine is stopped. Yes.

  FIG. 2A shows the engine stopped state, FIG. 2B shows the link posture of the multi-link piston-crank mechanism in the vicinity of the piston top dead center, and FIG.

  For example, in the case of an in-line four-cylinder internal combustion engine, the link posture when the rotation of the crankshaft 11 is completely stopped is high in the vicinity of the top dead center of the piston. Near the middle of the piston stroke excluding the vicinity of the dead center and the bottom dead center of the piston. Even in an internal combustion engine having other number of cylinders such as a V-type 6 cylinder, the link posture when the engine is stopped is generally near the middle of the piston stroke excluding the vicinity of the piston top dead center and the vicinity of the piston bottom dead center.

  Therefore, when the engine is next started, the lower link 12 swings as the crankshaft rotates, so that the oil is stored in the oil reservoir 28 near the top dead center of the piston as indicated by the arrow in FIG. The lubricating oil that has been used is scattered by centrifugal force along the bottom surface 27 of the oil reservoir 28 and sprayed toward the wall surface of the cylinder 20, that is, toward the sliding surface with the piston 13. . Accordingly, when the engine is started in the multi-link type piston-crank mechanism in which the lubricating oil is likely to be insufficient, the lubricating oil stored in the oil reservoir 28 is used to apply the lubricating oil to the wall surface of the cylinder 20 that is in sliding contact with the piston 13. Sufficient supply can improve lubrication performance.

  Here, in this multi-link type piston-crank mechanism, the inclination direction of the upper link 14 oscillating with the rotation of the crankshaft 11 with respect to the cylinder axis is one inclination direction, and in FIG. It is set to the inclination direction toward the anti-thrust direction (left side of the figure). For this reason, the direction of the load in the thrust-anti-thrust direction acting on the piston via the upper link 14 is limited to the anti-thrust direction, so that the so-called swing movement of the piston 13 is suppressed.

  In the present embodiment, when the engine is started from the engine stopped state, an oil pool is applied to the wall surface 20A of the cylinder 20 on one side in which the load in the thrust-anti-thrust direction acts, that is, the side crossing the anti-thrust direction. The lubricating oil stored in the portion 28 is sprayed. Thus, the cylinder wall surface 20A on which a load in the thrust-anti-thrust direction acts can be intensively lubricated.

  In addition, the bottom surface 27 constituting a part of the oil reservoir 28 has an arc shape so as to avoid interference with the other end of the swinging upper link 14. That is, the oil sump portion 28 is formed by effectively using a space that avoids interference with the upper link 14.

  Referring to FIGS. 4 to 6, the end of the bottom surface 27 of the oil reservoir 28 on the side where the lubricant is scattered guides the scattering of the lubricant toward the wall surface 20 </ b> A of the cylinder 20 on both sides in the axial direction. A pair of guide oil passages 33 are formed. The guide oil passage 33 is recessed in a groove shape having a predetermined length extending from the edge of the bottom surface 27 in the circumferential direction. By such a guide oil passage 33, the upper link 14 located at the center in the axial direction of the oil reservoir 28 is bypassed, and the lubricating oil is scattered well toward the wall surface of the cylinder 20 from both axial sides of the upper link 14. Can be made.

  In the embodiments described below, the same parts as those in the above-described embodiments are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate.

  FIG. 7 shows a second embodiment. In this second embodiment, the guide oil passage 34 is common to the first embodiment in that it is provided on both sides in the axial direction of the end portion of the bottom surface 27, but penetrates the inside of the lower link 12 in the circumferential direction. This is different from the first embodiment in that it is configured as an extending through hole. One end of the guide oil passage 34 opens to the oil reservoir 28, and the other end opens to the outer surface of the lower link 12. Even in the case where such a guide oil passage 34 is provided, the same operational effects as those of the first embodiment can be obtained.

  FIG. 8 shows a third embodiment. In the third embodiment, a guide oil passage 35 is formed at the axially central portion at the end of the bottom surface 27. As in the second embodiment, the guide oil passage 35 is configured as a through hole that extends through the interior of the lower link 12 in the circumferential direction. For example, when the upper link 14 is formed in a bifurcated shape, the scattered oil can pass through the central portion in the axial direction of the upper link 14, and the guide oil passage 35 is provided as in the third embodiment. It is good also as a structure provided in an axial direction center part.

  FIG. 9 shows a fourth embodiment. The guide oil passage 36 of the fourth embodiment is provided in the central portion in the axial direction at the end portion of the bottom surface 27, and is recessed in a substantially triangular pyramid shape that gradually decreases in the axial width toward the end edge of the bottom surface 27. Has been. In this case, it is possible to enhance the flow velocity and momentum of the lubricating oil scattered from the oil reservoir 28 to the cylinder 20 side, and to make the lubricating oil reach the cylinder 20 side satisfactorily.

  FIG. 10 shows a fifth embodiment. In the fifth embodiment, the guide oil passage as in the first to fourth embodiments is omitted, and the bottom surface 27 has a simple structure without the guide oil passage.

As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, even in the configuration without the oil jet 22, there is no problem in applying the present invention.
Further, the oil reservoir provided in the lower link may be provided in any part of the lower link as long as it is configured to store the lubricating oil when the engine is stopped and to be scattered on the wall surface of the cylinder when the engine is started. Further, the present invention can be applied not only in series but also to an internal combustion engine such as a V type or a horizontally opposed type, and the location and shape of the oil reservoir provided in the lower link can be appropriately set according to the type of the internal combustion engine.

10 ... Variable compression ratio mechanism (double-link piston-crank mechanism)
DESCRIPTION OF SYMBOLS 12 ... Lower link 14 ... Upper link 15 ... Control link 17 ... Connection pin 22 ... Oil jet 25 ... 1st pin boss | hub part 26 ... 2nd pin boss | hub part 27 ... Bottom 28 ... Oil reservoir part 33-36 ... Guide oil path

Claims (5)

A piston sliding in the cylinder;
A lower link rotatably attached to the crank pin of the crankshaft;
A multi-link type piston-crank mechanism having one end rotatably connected to the piston via a piston pin and the other end rotatably connected to the lower link via a connecting pin. In the lubrication structure,
The lower link is provided with an oil reservoir for storing lubricating oil when the engine is stopped,
The oil reservoir portion is configured so that the lubricating oil stored in the oil reservoir portion is scattered on the wall surface of the cylinder as the crankshaft rotates when the engine is started from an engine stop state. A lubrication structure for a multi-link piston-crank mechanism.
In the multi-link piston-crank mechanism, an inclination direction with respect to a cylinder axis of the upper link that swings with rotation of the crankshaft is set as one inclination direction,
When the engine is started from an engine stopped state, the lubricating oil stored in the oil reservoir is scattered on the wall surface of the cylinder on the side crossing the one inclination direction as the crankshaft rotates. The lubrication structure for a multi-link type piston-crank mechanism according to claim 1, wherein the structure is lubricated. A first pin boss provided in the upper link and through which the connecting pin passes;
A pair of second pin boss portions provided in the lower link, through which the connecting pin passes, and arranged in parallel to each other on both axial sides of the first pin boss portion;
The oil sump part is defined by an opposing surface of the pair of second pin boss parts and a bottom surface that connects ends of the opposing surfaces. The lubrication structure of the double link type piston-crank mechanism as described.   4. The lubrication structure for a multi-link piston-crank mechanism according to claim 3, wherein the bottom surface has an arc shape so as to avoid interference with the other end of the swinging upper link.   The guide oil passage which guides the scattering of the lubricating oil toward the wall surface of the cylinder is formed at both ends in the axial direction at the end of the bottom surface where the lubricating oil scatters. 5. A lubrication structure for a multi-link piston-crank mechanism according to 3 or 4.

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