JP2017201131A - Internal combustion engine with variable compression ratio mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve lubricating performance of a journal portion of a control shaft.SOLUTION: An internal combustion engine has a variable compression ratio mechanism which can vary an engine compression ratio in accordance with a rotation position of a control shaft 21. The control shaft 21 is rotatably supported by a main bearing cap 33 and a sub bearing cap 35 in an upper position of an oil pan 37 which stores lubricating oil. The sub bearing cap 35 includes a bearing surface 36B to which the control shaft 21 is rotatably fitted, and an oil passage 40 having one end opened to the bearing surface 36B and the other end opened to an end surface 39 of the sub bearing cap 35. The lubricating oil in the oil pan 37 is sucked into the oil passage 40 by pumping action following the rotation of the control shaft 21, and is supplied to the bearing surface 36B.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an internal combustion engine having a variable compression ratio mechanism, and more particularly to improvement of lubrication performance.

  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 that is rotatably attached to a crankpin of a crankshaft, an upper link that connects the lower link and the piston, an eccentric shaft portion that is eccentrically provided on the control shaft, and a lower link. And the engine compression ratio can be changed with changes in the piston top dead center position and bottom dead center position by changing the rotational position of the control shaft by an actuator such as a motor. .

JP 2004-116434 A

  Similar to the crankshaft, the control shaft is rotatably supported on the cylinder block side as the engine body by a shaft support portion such as a bearing cap. Therefore, it is necessary to lubricate the bearing portion of the journal portion of the control shaft as well as the main journal portion of the crankshaft. For this reason, the supply path of the lubricating oil increases, and there is a concern about an increase in the oil pump capacity and deterioration of engine friction.

  The present invention has been made in view of such circumstances, and in an internal combustion engine equipped with a variable compression ratio mechanism, a novel that can ensure lubrication performance of a bearing surface on which a journal portion of a control shaft is rotatably fitted. It aims to provide a simple lubrication structure.

  An oil passage having a shaft bearing portion formed with a bearing surface on which the control shaft is rotatably fitted, and having one end opened in the bearing surface and the other end opened in the end surface of the shaft support portion is formed. .

  During engine operation, a load in the rotational direction due to combustion pressure is repeatedly applied to the control shaft from the piston side via the upper link, lower link, and control link. Rotating motion that rotates automatically.

  Therefore, by providing an oil passage that connects the bearing surface and the end face of the shaft support portion as in the present invention, the lubricating oil stored in the oil pan is sucked into the oil passage by the pump action accompanying the rotation operation of the control shaft. The lubricating oil can be supplied to the bearing surface via this oil passage to lubricate the bearing surface of the shaft support portion into which the control shaft is rotatably fitted.

  Since there is no need to forcibly feed the lubricating oil using the oil pump in this way, the capacity of the oil pump can be reduced, and the shortest path can be provided through the oil passage provided in the shaft support portion. Since the lubricating oil can be supplied from the oil pan to the bearing surface, the lubricating oil supply path is simplified, and engine friction can be reduced.

  According to the present invention, the lubricating oil in the oil pan can be supplied to the bearing surface of the shaft support portion via the oil passage provided in the shaft support portion by utilizing the rotational motion of the control shaft. Therefore, it is possible to reduce the capacity of the oil pump, simplify the lubricating oil supply path, and reduce engine friction while ensuring the lubricating performance of the control shaft.

1 is a cross-sectional view schematically showing an internal combustion engine provided with a variable compression ratio mechanism according to a first embodiment of the present invention. The perspective view which shows a control link and a control shaft. The disassembled perspective view which similarly shows a control link and a control shaft. Sectional drawing which shows the support structure of a crankshaft and a control shaft. Sectional drawing which shows the support structure of the journal part of the control shaft which concerns on the said 1st Example. Sectional drawing which shows the support structure of the journal part of the control shaft which concerns on 2nd Example of this invention. Sectional drawing which shows the support structure of the journal part of the control shaft which concerns on 3rd Example of this invention. Sectional drawing which shows the support structure of the journal part of the control shaft which concerns on 4th Example of this invention. Sectional drawing which shows the support structure of the journal part of the control shaft which concerns on 5th Example of this invention. Sectional drawing which shows the support structure of the journal part of the control shaft which concerns on 6th 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 eccentric from the rotation center, 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 the drive motor 26 as a variable compression ratio actuator, 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. Along with the change, the engine compression ratio changes. Therefore, by controlling the operation of the drive motor 26 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, a lubricating structure in the vicinity of the control shaft 21 that forms the main part of the first embodiment of the present invention will be described with reference to FIGS. In addition, "upper and lower" in this specification is basically along the vertical direction in the in-vehicle posture.

  2 and 3, the control link 15 includes a cylindrical small end portion 15A in which the control pin 18 is rotatably fitted, and a cylinder in which the eccentric shaft portion 21A of the control shaft 21 is rotatably fitted. And a rod portion 15C connecting the small end portion 15A and the large end portion 15B. The large end portion 15B is formed in a halved shape with the eccentric shaft portion 21A interposed therebetween, and one control link cap 15D is fixed to the rod portion 15C side by two bolts 15E. The rod portion 15C of the control link 15 includes a bearing portion of the small end portion 15A in which the control pin 18 is rotatably fitted and a bearing portion of the large end portion 15B in which the eccentric shaft portion 21A is rotatably fitted. A connecting rod internal oil passage 15F is formed.

  An axial oil passage 27 extending in the axial direction is formed in the control shaft 21, and the outer periphery of the eccentric shaft portion 21 </ b> A and the axial oil passage 27 are connected to the eccentric shaft portion 21 </ b> A into which the control link 15 is rotatably fitted. Is formed, and a journal portion 21B, which will be described later, is formed with a second radial oil passage 29 that connects the outer periphery of the journal portion 21B and the axial oil passage 27. Yes.

  As shown in FIG. 4, the main journal portion 11 </ b> B of the crankshaft 11 includes a plate-shaped bulkhead 31 provided integrally with the cylinder block 19, and two fixing bolts ( In the drawing, the fixing bolt is omitted, and only the bolt hole 32 through which the fixing bolt is inserted is drawn), and the main bearing cap 33 is fastened and fixed between both of the main bearing cap 33 and the main bearing cap 33. . On the lower surface side of the bulkhead 31, a bearing surface 34A having a semicircular cross section in which the upper half of the main journal portion 11B is rotatably fitted is recessed, and on the upper surface side of the main bearing cap 33, the main journal portion 11B. A bearing surface 34B having a semicircular cross section in which the lower half is rotatably fitted is recessed.

  The journal portion 21B of the control shaft 21 is sandwiched between the main bearing cap 33 and the auxiliary bearing cap 35 fastened and fixed to the lower surface side of the main bearing cap 33 using the two fixing bolts. Is supported rotatably. On the lower surface side of the main bearing cap 33, a bearing surface 36A having a semicircular cross section in which the upper half of the journal portion 21B is rotatably fitted is recessed, and on the upper surface side of the auxiliary bearing cap 35, the journal portion 21B is provided. A bearing surface 36B having a semicircular cross section in which the lower half is rotatably fitted is recessed.

  The bulkhead 31, the main bearing cap 33, and the sub bearing cap 35 constitute a shaft support portion that rotatably supports the crankshaft 11 and the control shaft 21. The two fixing bolts have a function of fastening the bulkhead 31 and the main bearing cap 33 and a function of fastening the main bearing cap 33 and the auxiliary bearing cap 35, and the configuration is simplified. Yes. The control shaft 21 is disposed substantially vertically below the crankshaft 11 in a vehicle-mounted state. Accordingly, the journal portion 21B of the control shaft 21 and the main journal portion 11B of the crankshaft 11 are both disposed between the two fixing bolts (bolt holes 32).

  An oil pan 37 for storing lubricating oil is provided below the control shaft 21, that is, below the internal combustion engine. That is, the control shaft 21 is disposed by effectively using the space below the crankshaft 11 and above the oil pan 37. Therefore, in the engine operation state, a part of the auxiliary bearing cap 35 located below the control shaft 21 is located at least below the oil level 38 of the lubricating oil stored in the oil pan 37, The oil is immersed in the lubricating oil in the oil pan 37.

  In this embodiment, the auxiliary bearing cap 35 as a shaft support portion is formed with an oil passage 40 having one end opened to the bearing surface 36B and the other end opened to the end surface 39 of the auxiliary bearing cap 35. That is, the oil passage 40 extends straight downward from the lower end portion of the bearing surface 36 </ b> B in the in-vehicle state, and opens to the end surface 39 of the auxiliary bearing cap 35.

  During engine operation, the control shaft 21 is driven or held by the drive motor 26 so as to have a predetermined engine compression ratio according to the engine operation state. Even in an operating state in which the rotation angle should be maintained, a large load in the rotational direction due to the combustion pressure acting on the piston 13 is applied to the control shaft 21 via the upper link 14, the lower link 12 and the control link 15. Thus, the control shaft 21 inevitably rotates in the forward and reverse directions within a predetermined rotation range.

  In the present embodiment, the control shaft 21 inevitably rotates while the engine is operating, and the auxiliary bearing cap 35 serving as the shaft support portion is immersed in the lubricating oil stored in the oil pan 37. Focusing on the fact that the oil passage 40 is formed, the oil passage 40 is formed. Since the other end of the oil passage 40 is immersed in the lubricating oil in the oil pan 37, if the engine is in an operating state, the lubricating oil in the oil pan 37 is moved by the pump action accompanying the rotational movement of the control shaft 21. The journal portion 21B of the control shaft 21 is supplied to the bearing surface 36B that is rotatably fitted via the oil passage 40, and the bearing surface 36B and the upper bearing connected to the bearing surface 36B. The lubrication performance of the journal portion 21B of the control shaft 21 supported by the surface 36 can be ensured satisfactorily.

  Thus, since the lubricating oil can be supplied to the bearing surface 36B by utilizing the pump action accompanying the rotational movement of the control shaft 21, it is not necessary to forcibly feed the lubricating oil by the oil pump, and the energy corresponding thereto. Since the consumption is suppressed, the capacity of the oil pump can be reduced. Further, since the lubricating oil can be supplied from the oil pan 37 to the bearing surface 36B through the oil passage 40 through the shortest path, the lubricating oil supply path can be shortened and simplified, and the engine friction can be reduced. it can.

  During engine operation, the control link 15 performs a so-called swinging motion that swings around the eccentric shaft portion 21A that is rotatably fitted at the large end portion 15B. The lubricating oil supplied to the bearing surface 36B for the control shaft 21 through the oil passage 40 passes through the second radial oil passage 29, the axial oil passage 27, and the first radial oil passage 28 of the control shaft 21 described above. , Can be supplied to the bearing surface 36B of the eccentric shaft portion 21A that is rotatably fitted to the large end portion 15B of the control link 15, and via the oil passage 15F in the rod formed in the control link 15, The control pin 18 can also be supplied to the bearing portion of the small end portion 15A in which the control pin 18 is rotatably fitted. As a result, the capacity of the oil pump can be further reduced, the lubricating oil supply path can be simplified, and the engine friction can be reduced.

  In the embodiments described below, the same components as those in the above-described embodiments are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  FIG. 6 shows a second embodiment. In the second embodiment, a tapered portion 41 that gradually increases in diameter downward is formed at the other end of the oil passage 40. As a result, the oil passage 40 has the largest cross-sectional area (opening area) at the portion opened to the end surface 39 of the sub bearing cap 35. In such a 2nd Example, since the taper part 41 diameter-expanded toward the downward direction is provided in the oil channel 40, the lubricating oil stored in the oil pan 37 is attracted more effectively in the oil channel 40. It is possible to improve the lubricating performance by securing the amount of lubricating oil.

  FIG. 7 shows a third embodiment, and FIG. 8 shows a fourth embodiment. In the first embodiment, the oil passage 40 is formed to extend downward from the lower end of the bearing surface 36B along the vertical direction to form the oil passage 40 at the shortest distance. The portion directly below the journal portion 21B has the thinnest thickness, and a load caused by the combustion pressure is also likely to act. Therefore, in the third and fourth embodiments, the bearing surface 36B and the end surface 39 of the auxiliary bearing cap 35 are located at the lowest end of the bearing surface 36B, that is, at a position shifted to the left and right from the position directly below the journal portion 21B of the control shaft 21. Oil passages 40A and 40B are formed. In particular, in the third and fourth embodiments, oil passages 40A and 40B are formed at positions corresponding to both ends of the rotation range of the control shaft 21, respectively. As a result, in addition to obtaining substantially the same operational effects as those of the first embodiment described above, it is possible to suppress load concentration and improve reliability and durability.

  The fifth embodiment shown in FIG. 9 is a combination of the third and fourth embodiments, that is, oil passages are respectively provided at two locations corresponding to both ends of the rotation range of the control shaft 21. 40 is formed. In this way, a plurality of oil passages 40 may be formed. In this case, in addition to obtaining the same effects as those of the second and third embodiments, the oil passage 40 is supplied to the bearing surface 36B via the oil passage 40. The amount of lubricating oil produced can be increased and the lubricating performance can be further improved.

  FIG. 10 shows a sixth embodiment. In this embodiment, three oil passages 40C, 40D, 40F are formed radially from the lowest end of the bearing surface 36B (portion vertically downward from the center of the control shaft 21) downward. As in the first embodiment, the central oil passage 40C extends straight from the lowermost end of the bearing surface 36B vertically downward, and the two oil passages 40D and 40E on both sides are connected to the sub bearing cap 35. The end surface 39 extends obliquely downward toward positions corresponding to both ends of the rotation range of the control shaft 21.

  In this way, the plurality of oil passages 40C, 40D, and 40E may be configured to merge and intersect. In the sixth embodiment as well, the same operation as in the first and fifth embodiments is performed. An effect can be obtained.

  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, although the oil passage is formed in a straight line in the above embodiment, the oil passage may have a bent portion or a bent portion. In the above-described embodiment, the bulkhead 31, the main bearing cap 33, and the auxiliary bearing cap 35 are used as the shaft support portion. However, the shape of the shaft support portion is not limited to this, for example, a ladder frame type shaft support. May be part. The internal combustion engine to which the present invention is applied can be applied not only in series but also to a V-type or horizontally opposed internal combustion engine.

DESCRIPTION OF SYMBOLS 10 ... Variable compression ratio mechanism 11 ... Crankshaft 11B ... Main journal part 12 ... Lower link 14 ... Upper link 15 ... Control link 17 ... Connection pin 18 ... Control pin 21 ... Control shaft 21A ... Eccentric shaft part 21B ... Journal part 26 ... Drive motor (actuator)
35 ... Secondary bearing cap (shaft support)
37 ... Oil pan 40 (40A-40E) ... Oil passage

Claims (5)

A lower link rotatably attached to the crank pin of the crankshaft;
An upper link connecting the lower link and the piston;
A control shaft rotated by an actuator;
A control link connecting the control shaft and the lower link;
In an internal combustion engine including a variable compression ratio mechanism configured to change an engine compression ratio according to a rotational position of the control shaft,
An oil pan for storing lubricating oil is disposed below the control shaft,
The internal combustion engine has a shaft support portion formed with a bearing surface on which the control shaft is rotatably fitted. One end of the shaft support portion is open to the bearing surface, and the other end is the shaft support portion. An oil passage opening at the end face of the
An internal combustion engine provided with a variable compression ratio mechanism, wherein an end surface of the shaft support portion where the oil passage opens is submerged in lubricating oil of the oil pan.   2. The structure according to claim 1, wherein the lubricating oil in the oil pump is supplied to the bearing surface via the oil passage by a pump action accompanying rotation of the control shaft. An internal combustion engine having a variable compression ratio mechanism.   3. The variable compression ratio mechanism according to claim 1, wherein a tapered portion whose opening area gradually increases toward an end face of the shaft support portion is formed at the other end portion of the oil passage. Internal combustion engine equipped with.   The internal combustion engine having a variable compression ratio mechanism according to claim 1 or 2, wherein the oil passage is provided at a position corresponding to an end of a rotation range of the control shaft that rotates.   The control shaft includes an axial oil passage extending in the axial direction in the control shaft, a first radial oil passage connecting the outer periphery of the eccentric shaft portion and the axial oil passage, and the outer periphery and shaft of the journal portion. An internal combustion engine comprising the variable compression ratio mechanism according to any one of claims 1 to 4, further comprising a second radial oil passage that connects the directional oil passage.

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