JP2014194208A - Lubrication structure of variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubrication structure of a variable compression ratio internal combustion engine which is improved.SOLUTION: A lubrication structure of a variable compression ratio internal combustion engine includes a variable compression ratio mechanism which can change an engine compression ratio in accordance with a rotational position of a control shaft 14. By using a main bearing cap 31 and a sub bearing cap 32 fixed to a cap attachment part 30 of an engine main body by means of two fixing bolts 33, both of a crank shaft 4 and the control shaft 14 are rotatably supported. A first oil path 48 which couples a main bearing part 35 of the crank shaft 4 with a bolt penetration hole 41A penetrated by the fixing bolt 33 and a second oil path 49 which couples the bolt penetration hole 41A with a sub bearing part 37 of the control shaft 14 are formed on the main bearing cap 31 and lubricant supplied to the main bearing part 35 is supplied to the sub bearing part 37 via the first oil path 48, the bolt penetration hole 41A and the second oil path 49.

Description

  The present invention relates to a variable compression ratio internal combustion engine including a variable compression ratio mechanism capable of changing an engine compression ratio, and more particularly, to an improvement in its lubricating structure.

  Patent Document 1 describes a variable compression ratio mechanism that can change an engine compression ratio by using a multi-link type piston-crank mechanism. In this variable compression ratio mechanism, a piston and a crankshaft are connected by an upper link and a lower link, and an upper link or a lower link and a control shaft are connected by a control link, and a rotational position of the control shaft by an actuator such as a motor. By changing the engine, the engine compression ratio is changed and controlled in accordance with the engine operating state.

JP 2004-257254 A

  The control shaft of such a variable compression ratio mechanism is supported rotatably on the engine body via a bearing cap or the like because a large combustion load or inertia load repeatedly acts through the upper link, lower link and control link. It is necessary to reliably supply lubricating oil to the bearing portion.

  The present invention provides a novel lubricating structure for supplying lubricating oil to a sub-bearing portion of a control shaft in a variable compression ratio internal combustion engine having such a variable compression ratio mechanism.

  That is, the variable compression ratio internal combustion engine according to the present invention is a variable compression ratio mechanism capable of changing the engine compression ratio according to the rotational position of the control shaft, a cap mounting portion provided in the engine body, a main bearing cap, A secondary bearing cap. A main bearing portion having a semi-cylindrical surface shape for rotatably supporting a crankshaft of the internal combustion engine is formed on a main mating surface formed by a lower surface of the cap mounting portion and an upper surface of the main bearing cap. In addition, a sub-cylindrical sub-bearing portion that rotatably supports the control shaft is formed on a sub-mating surface composed of a lower surface of the main bearing cap and an upper surface of the sub-bearing cap. A fixing bolt for fixing both the sub bearing cap and the main bearing cap to the cap mounting portion penetrates the sub bearing cap and the main bearing cap in the cylinder axial direction and is screwed into the cap mounting portion. Lubricating oil is supplied to the main bearing portion of the crankshaft by an oil pump or the like.

  Then, a first oil passage connecting the main bearing cap and the bolt through-hole through which the fixing bolt passes, and a second oil passage connecting the bolt through-hole and the auxiliary bearing portion to the main bearing cap, The lubricating oil supplied to the main bearing portion is supplied to the sub-bearing portion through the first oil passage, the bolt through hole, and the second oil passage.

  According to the present invention, a structure in which both the crankshaft and the control shaft are rotatably supported on the engine body side using the main bearing cap and the sub-bearing cap, and the configuration is simplified by sharing the bearing cap. On the other hand, the first oil passage, the bolt through hole, and the second oil passage are formed as an oil passage for supplying lubricating oil to the main bearing cap from the main bearing portion to the sub-bearing portion, thereby lubricating the sub-bearing portion of the control shaft. Oil can be supplied. In addition, by using a bolt through hole through which a fixing bolt for fixing the bearing cap to the engine body passes as an oil passage, there is no need to separately form an oil passage corresponding to this bolt through hole, and an oil passage structure Can be simplified.

1 is a configuration diagram showing a variable compression ratio internal combustion engine to which a lubricating structure according to a first embodiment of the present invention is applied. Sectional drawing which shows the vicinity of the bearing part of the crankshaft and control shaft of the said 1st Example. Sectional drawing which shows the main bearing cap of the said 1st Example alone. Sectional drawing which shows the main bearing cap by which the lubricating structure which concerns on 2nd Example of this invention was applied alone. Sectional drawing which shows the main bearing cap with which the lubrication structure concerning the comparative example was applied alone.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, a variable compression ratio mechanism 10 using a multi-link type piston-crank mechanism will be described with reference to FIG. Since this mechanism 10 is known as described in Japanese Patent Application Laid-Open No. 2004-257254, etc., only a simple description will be given.

  A piston 3 of each cylinder is slidably fitted in a cylinder 2 and a crankshaft 4 is rotatably supported on a cylinder block 1 constituting a part of an engine body of the internal combustion engine. The variable compression ratio mechanism 10 includes a lower link 11 rotatably attached to the crankpin 5 of the crankshaft 4, an upper link 12 connecting the lower link 11 and the piston 3, and the engine body side such as the cylinder block 1. A control shaft 14 rotatably supported, an eccentric shaft portion 15 provided eccentric to the control shaft 14, and a control link 13 connecting the eccentric shaft portion 15 and the lower link 11 (or the upper link 12). ,have. The piston 3 and the upper end of the upper link 12 are connected via a piston pin 16 so as to be relatively rotatable, and the lower end of the upper link 12 and the lower link 11 are connected via an upper link side connecting pin 17 so as to be relatively rotatable, The upper end of the control link 13 and the lower link 11 are connected to each other via a control link side connecting pin 18 so as to be relatively rotatable, and the lower end of the control link 13 is rotatably attached to the eccentric shaft portion 15.

  A motor 19 as an actuator of the variable compression ratio mechanism 10 is connected to the control shaft 14 via a connecting mechanism 20 having a speed reducer (not shown). By changing the rotational position (angle) of the control shaft 14 by the motor 19, the piston stroke characteristics including the piston top dead center position and the piston bottom dead center position change as the posture of the lower link 11 changes. The engine compression ratio changes. Therefore, the engine compression ratio can be controlled according to the engine operating state by controlling the motor 19 to be driven by the control unit 21. The actuator is not limited to the electric motor 19 and may be a hydraulic drive actuator.

  The control shaft 14 is rotatably supported inside an oil pan 6 that is provided below the cylinder block 1 and stores lubricating oil. The oil pan 6 includes an oil pan upper 6A fixed to the lower side of the cylinder block 1 and an oil pan lower 6B fixed to the lower side of the oil pan upper 6A so as to close the lower surface opening of the oil pan upper 6A. And is composed of. On the other hand, the motor 19 is disposed outside the engine body, and more specifically, is attached to the intake side wall (hereinafter referred to as “oil pan side wall”) 7 of the oil pan upper 6A constituting a part of the engine body. The housing 22 is attached to the rear side of the engine.

  The reduction gear described above is a device that reduces the rotation of the output shaft of the motor 19 and transmits it to the control shaft 14. For example, a structure using a wave gear mechanism is used. The speed reducer is not limited to a structure using such a wave gear mechanism, and other types of speed reducers such as a cyclo speed reducer can be used.

  The coupling mechanism 20 is provided with an auxiliary shaft 23 that is formed integrally with the output shaft of the speed reducer. Note that the output shaft of the speed reducer and the auxiliary shaft 23 may be separated and connected so that both rotate in conjunction with each other.

  The auxiliary shaft 23 is rotatably accommodated in a housing 22 placed on the side of the oil pan side wall 7 and extends along the oil pan side wall 7 in the longitudinal direction of the engine (that is, in a direction parallel to the control shaft 14). Exist. The control shaft 14 disposed inside the engine body where the lubricating oil scatters and the auxiliary shaft 23 provided outside the engine body are mechanically connected by a lever 24 penetrating the oil pan side wall 7. Both 14 and 23 rotate in conjunction with each other. The oil pan side wall 7 and the housing 22 are formed with a slit 24A through which the lever 24 is inserted, and the housing 22 is liquid-tightly attached to the oil pan side wall 7 so as to close the periphery of the slit 24A. .

  One end of the lever 24 and the tip end of the first arm portion 25 extending radially outward from the center of the control shaft 14 are connected via a first connecting pin 26 so as to be relatively rotatable. The other end of the lever 24 and the tip end of the second arm portion 27 extending radially outward from the center of the auxiliary shaft 23 are connected via a second connecting pin 28 so as to be relatively rotatable.

  With such a link structure, when the control shaft 14 rotates, the engine compression ratio changes and the postures of the first arm portion 25, the second arm portion 27, and the lever 24 change. The reduction ratio of the rotational power transmission path to the vehicle also changes.

  Referring to FIG. 2, the main journal portion 4A of the crankshaft 4 and the journal portion 14A of the control shaft 14 are fixed to a thin plate-like cap mounting portion 30 formed in the cylinder block 1 as the engine body. A bearing cap 31 and a sub bearing cap 32 are used to be rotatably supported on the engine body side. The main bearing cap 31 and the sub bearing cap 32 are fastened and fixed to the lower surface side of the cap mounting portion 30 by using two fixing bolts 33 (33A, 33B).

  A main bearing surface 35 constituted by the lower surface of the cap mounting portion 30 and the upper surface of the main bearing cap 31 is provided with a semi-cylindrical surface main bearing portion 35, and the two main bearing portions 35 are combined. The main journal portion 4A of the crankshaft 4 is rotatably supported in the cylindrical surface space. Similarly, a sub-cylindrical sub-bearing portion 37 is formed in a sub-joining surface 36 constituted by the lower surface of the main bearing cap 31 and the upper surface of the sub-bearing cap 32, and both sub-bearing portions are provided. The journal portion 14 </ b> A of the control shaft 14 is rotatably supported in a cylindrical surface space including the 37.

Two fixing bolts 33 (33A, 33B) are disposed on both sides of the main bearing portion 35 and the sub bearing portion 37 in the thrust-anti-thrust direction. Each fixing bolt 33 has a bolt head 38 formed on the base end side (lower end in FIG. 2) and a male screw 40 formed on the outer peripheral surface on the tip end side (upper side in FIG. 2) of the bolt shaft portion 39. .
The main bearing cap 31 is formed with a bolt through hole 41 penetrating in the cylinder axial direction (vertical direction in FIG. 2), and the auxiliary bearing cap 32 is also in the cylinder axial direction (vertical direction in FIG. 2). A penetrating bolt through hole 42 (42A, 42B) is formed through. Further, the cap mounting portion 30 is formed with a bolt screwing hole 43 extending in the cylinder axial direction, in which a female screw 44 is formed on the inner peripheral surface. Then, the corresponding bolt through holes 41 and 42 and the bolt screw holes 43 are aligned on the same line, and the fixing bolt 33 is inserted into the bolt through holes 41 and 42 from the lower side of FIG. The main bearing cap 31 and the auxiliary bearing cap 32 are fastened and fixed together between the bolt head portion 38 and the cap mounting portion 30 by screwing 40 into the female screw 44 of the bolt screwing hole 43 and tightening.

  Here, in consideration of workability at the time of fastening the bolt, the diameters of the bolt through holes 41 and 42 are formed larger than the diameter of the bolt shaft portion 39 of the fixing bolt 33, and a cylindrical gap is formed between the two. 45 is secured. In this embodiment, the cylindrical gap 45 is used as part of oil passages 48 and 49 described later. Therefore, in this embodiment, the gap 45 between the bolt through hole 42 and the bolt shaft portion 39 is sufficiently large so that the bolt through hole 42 (42B) also functions as an oil passage.

  Next, the lubrication structure that forms the main part of the present embodiment will be described. In the following description, with respect to the thrust-anti-thrust direction (left-right direction in FIG. 1), the upstream side (left side in FIG. 1) of the rotation direction R of the crankshaft 4 is referred to as the first direction DA. The downstream side is referred to as a second direction DB. Further, if necessary, the components located in the first direction DA are appended with “A” after the reference symbol, and the components located in the second direction DB are appended with “B” after the reference symbol. Is added. For example, when distinguishing the two fixing bolts 33 positioned on both sides of the bearing portions 35 and 37 in the thrust-anti-thrust direction, the fixing bolt positioned in the first direction DA is referred to as a fixing bolt 33A, and the second direction The fixing bolt located at DB is referred to as fixing bolt 33B.

  [1] As shown in FIG. 2, the crankshaft 4 is formed with an axial oil passage 46 extending in the axial direction at the center of the main shaft, and an axial oil passage 46 is formed in the main journal portion 4A. A radial oil passage 47 penetrating in the radial direction while intersecting is formed. Via these axial oil passages 46 and radial oil passages 47, lubricating oil pumped by an oil pump (not shown) is supplied to the main bearing portion 35, and the main bearing portion 35 is lubricated. (Lubricating oil supply means).

  In the present embodiment, the first oil passage 48 connecting the main bearing cap 31 to the bolt through hole 41 (41A) through which the main bearing portion 35 and the fixing bolt 33 pass, and the bolt through hole 41 (41A) and the sub-hole 41 A second oil passage 49 connecting the bearing portion 37, and the lubricating oil supplied to the main bearing portion 35 via the first oil passage 48, the bolt through hole 42, and the second oil passage 49. Is supplied to the auxiliary bearing portion 37.

  As described above, in this embodiment, the bearing cap 31 is configured such that both the crankshaft 4 and the control shaft 14 are rotatably supported on the engine body side by using the main bearing cap 31 and the auxiliary bearing cap 32. , 32 can be simplified, and the lubricating oil can be supplied to the auxiliary bearing portion 37 of the control shaft 14 with a simple oil passage structure using the main bearing cap 31.

  In addition, by using the bolt through hole 41 (41A) through which the fixing bolt 33 that fixes the bearing caps 31 and 32 to the engine body side passes as an oil passage, an oil passage corresponding to the bolt through hole 41 (41A) is provided. There is no need to form it separately, and the oil passage structure can be further simplified.

  FIG. 5 is a cross-sectional view showing a main bearing cap 31A to which a lubricating structure according to a comparative example is applied. In this comparative example, lubricating oil is directly supplied from the cylinder block side to the auxiliary bearing portion 37 via the oil passage 60, and one end (upper end) of the oil passage 60 is a cap mounting portion of the cylinder block. An opening is formed in the upper main mating surface 34 fixed to 30 (see FIG. 1), and the other end (lower end) of the oil passage 60 is opened in the auxiliary bearing portion 37. In such a structure of the comparative example, since one end of the oil passage 60 is opened on the main mating surface 34, the cap width increases, the weight and size of the main bearing cap 31A increase, and the cap width increases. Due to the increase, the surface pressure of the main mating surface 34 decreases, and mouth opening and fretting are likely to occur.

  On the other hand, in the present embodiment, the oil passage (60) for drawing the lubricating oil directly from the cylinder block side to the auxiliary bearing portion 37 as in the comparative example can be eliminated, so that the machining cost correspondingly is reduced. In addition to the reduction, since it is not necessary to open one end of the oil passage (60) in the main mating surface 34, the cap width can be shortened, and the main bearing cap 31 can be reduced in weight and size, and By reducing the cap width, the surface pressure of the main mating surface 34 can be improved, and the occurrence of mouth opening and fretting can be effectively suppressed.

  Although not shown, in order to align the shaft centers of the bolt through holes 41 and 42 of the main and sub bearing caps 31 and 32, cylindrical collars are provided in the bolt through holes 41 and 42 in the vicinity of the sub mating surface 36. When interposing, the second oil passage 49 is also formed through this collar.

  [2] Referring to FIG. 1, in the variable compression ratio mechanism 10 of the present embodiment, the center 3A of the piston 3 is offset from the main shaft center 4B of the crankshaft 4 in the first direction DA. In addition, the center 15A of the eccentric shaft portion 15 of the control shaft 14 is arranged offset in the second direction DB on the opposite side. In this relationship, when a large load including the maximum combustion load is applied, a diagonally downward force F1 that is inclined in the second direction DB from the main journal portion 4A of the crankshaft 4 is applied to the main bearing cap 31. At the same time, a diagonally upward force F2 is applied which is inclined in the first direction DA from the journal portion 14A of the control shaft 14. Due to the relationship between these forces F1 and F2, the main bearing cap 31 is shaped to receive a moment in the same direction as the crank rotation direction R, and the mating surfaces 34 and 36 have high adhesion in the first direction DA, and the second The adhesion becomes weaker in the direction DB. That is, on the first direction DA side, the adhesion is improved, so that the load burden on the bolt fastening portion is reduced compared to the second direction DB side, and durability and reliability are improved. It has a structure that can afford.

  Therefore, in the present embodiment, of the two bolt through holes 41A and 41B located on both sides in the thrust-anti-thrust direction of the bearing portions 35 and 37, the bolt through hole 41A located in the first direction DA having high adhesion is used. Only the first oil passage 48 and the second oil passage 49 are communicated. Thus, the 1st oil path 48 and the 2nd oil path 49 are formed in the 1st direction DA side where the load burden of a bolt fastening part is low, and the 1st oil path 48 in the 2nd direction DB side is formed. And compared with the case where the 2nd oil path 49 is formed, durability and reliability with respect to big loads, such as a maximum combustion load, can mainly be improved.

  [3] FIG. 3 shows a cross-sectional view of the main bearing cap 31 cut along a plane orthogonal to the crankshaft axial direction. The first oil passage 48 has a groove shape that is recessed in a semicircular arc shape or a channel shape in the axial central portion of the upper surface constituting the main mating surface 34 of the main bearing cap 31. For this reason, it is easy to process, and as compared with the case where the first oil passage is formed through the inside of the main bearing cap 31 as in the second embodiment to be described later, the stress concentration portion is reduced and the reliability is improved. Property and durability can be improved.

  [4] Similarly, the second oil passage 49 also has a groove shape recessed in the shape of a semicircular arc or a channel in the center in the axial direction of the lower surface constituting the auxiliary mating surface 36 of the main bearing cap 31. Yes. For this reason, processing is easy, and the stress concentration site is reduced and reliable as compared with the case where the second oil passage is formed through the main bearing cap 31 as in the second embodiment described later. Property and durability can be improved.

  [5] FIG. 4 is a sectional view showing a main bearing cap 31 to which a lubricating structure according to a second embodiment of the present invention is applied. In the second embodiment, contrary to the first embodiment, the first oil passage 50 and the second oil passage 51 are communicated only with the bolt through holes 41B located in the second direction DB. In this way, by forming the first oil passage 50 and the second oil passage 51 on the second direction DB side where the adhesiveness is low and the generated stress is small, the first direction DA in the first direction DA as in the first embodiment. Compared with the case where the first oil passage and the second oil passage are formed on the side, durability and reliability against fatigue damage mainly due to stress concentration can be improved.

  [6] Further, in the first embodiment, the first and second oil passages 48 and 49 are recessed in the mating surfaces 34 and 36. The oil passage 51 is formed as an oil hole that penetrates the inside of the main bearing cap 31 instead of the mating surfaces 34 and 36. Specifically, the first oil passage 50 is formed as a straight oil hole extending obliquely downward from the main bearing portion 35 to the bolt through hole 41B, and the second oil passage 51 is similarly formed as the bolt through hole 41B. Is formed as a linear oil passage extending obliquely downward from the auxiliary bearing portion 37 to the auxiliary bearing portion 37. Thus, by forming the first and second oil passages 50 and 51 as oil holes, the positions of the oil passages 50 and 51 and their openings can be arbitrarily set, and therefore the degree of freedom in layout. Since the oil passages 50 and 51 are formed while avoiding stress concentration sites, the durability and reliability can be improved, and the positions of the openings of the oil passages 50 and 51 with respect to the bearing portions 35 and 37 are increased. By optimizing the above, it is possible to improve the lubricity.

  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, in the above embodiment, the first and second oil passages are communicated with one of the two bolt through holes, but the first and second oil passages are communicated with both bolt through holes. May be. Alternatively, one of the first and second oil passages may be recessed in the mating surface, and the other may be formed as an oil hole penetrating through the main bearing cap.

3 ... Piston 4 ... Crankshaft 10 ... Variable compression ratio mechanism 14 ... Control shaft 30 ... Cap mounting portion 31 ... Main bearing cap 32 ... Sub bearing cap 33 ... Fixing bolt 34 ... Main mating surface 35 ... Main bearing portion 36 ... Sub mating Surface 37 ... sub bearing portion 41 (41A, 41B) ... bolt through holes 48, 50 ... first oil passages 49, 51 ... second oil passages

Claims (6)

A variable compression ratio mechanism capable of changing the engine compression ratio according to the rotational position of the control shaft;
A cap mounting portion provided on the engine body;
A main bearing cap;
A secondary bearing cap,
A semi-cylindrical main bearing portion that rotatably supports the crankshaft of the internal combustion engine is formed on the main mating surface composed of the lower surface of the cap mounting portion and the upper surface of the main bearing cap,
A sub-cylindrical sub-bearing portion for rotatably supporting the control shaft is formed on a sub-mating surface composed of a lower surface of the main bearing cap and an upper surface of the sub-bearing cap,
And the fixing bolt which fixes both the said sub bearing cap and the main bearing cap to a cap attaching part by penetrating the said auxiliary bearing cap and the main bearing cap to a cylinder axial direction, and screwing together to the said cap attaching part. A variable compression ratio internal combustion engine lubrication structure having
While having a lubricating oil supply means for supplying lubricating oil to the main bearing portion,
A first oil passage connecting the main bearing portion and a bolt through-hole through which the fixing bolt penetrates, and a second oil passage connecting the bolt through-hole and the auxiliary bearing portion are formed in the main bearing cap. ,
The lubricating oil supplied to the main bearing portion is supplied to the auxiliary bearing portion via the first oil passage, the bolt through hole, and the second oil passage. Lubrication structure of a variable compression ratio internal combustion engine. The variable compression ratio mechanism includes a lower link rotatably attached to the crankshaft, an upper link connecting the lower link and the piston, and an eccentric shaft provided eccentric to the lower link or the upper link and the control shaft. A control link connecting the parts,
Further, the variable compression ratio mechanism is arranged with the center of the piston offset from the center of the main shaft of the crankshaft in a first direction which is upstream in the rotation direction of the crankshaft in the thrust-anti-thrust direction. In addition, the center of the eccentric shaft portion of the control shaft is offset from the center of the crankshaft main shaft in the second direction, which is the downstream side in the rotation direction of the crankshaft in the thrust-anti-thrust direction,
Of the two bolt through holes arranged on both sides of the main bearing portion and the sub bearing portion in the thrust-anti-thrust direction, only the first oil passage and the bolt through hole located in the first direction are provided. The lubricating structure for a variable compression ratio internal combustion engine according to claim 1, wherein the second oil passage is in communication.   The lubricating structure for a variable compression ratio internal combustion engine according to claim 1 or 2, wherein the first oil passage is recessed in an upper surface of the main bearing cap.   The lubricating structure for a variable compression ratio internal combustion engine according to any one of claims 1 to 3, wherein the second oil passage is recessed in a lower surface of the main bearing cap. The variable compression ratio mechanism includes a lower link rotatably attached to the crankshaft, an upper link connecting the lower link and the piston, and an eccentric shaft provided eccentric to the lower link or the upper link and the control shaft. A control link connecting the parts,
Further, the variable compression ratio mechanism is arranged with the center of the piston offset from the center of the main shaft of the crankshaft in a first direction which is upstream in the rotation direction of the crankshaft in the thrust-anti-thrust direction. In addition, the center of the eccentric shaft portion of the control shaft is offset from the center of the crankshaft main shaft in the second direction, which is the downstream side in the rotation direction of the crankshaft in the thrust-anti-thrust direction,
Of the two bolt through holes disposed on both sides of the main bearing portion and the sub bearing portion in the thrust-anti-thrust direction, only the first oil passage and the bolt through hole located in the second direction are provided. The lubricating structure for a variable compression ratio internal combustion engine according to claim 1, wherein the second oil passage is in communication.   6. The variable compression ratio internal combustion engine according to claim 1, wherein at least one of the first oil passage and the second oil passage is formed so as to penetrate inside the bearing cap. Lubrication structure.

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