JP5218305B2 - Crankshaft of an internal combustion engine having a multi-link type piston-crank mechanism - Google Patents

Description

  The present invention relates to a crankshaft of an internal combustion engine having a multi-link piston-crank mechanism.

  As a main motion system that connects the piston of the internal combustion engine and the crankpin of the crankshaft, a multi-link piston-crank mechanism (hereinafter referred to as “multi-link mechanism”) in which the piston pin of the piston and the crankpin of the crankshaft are connected by a plurality of links. The present applicant is considering the optimization of the piston stroke characteristics and the variable control of the compression ratio.

  Here, as described in Patent Document 1, in a single link type piston-crank mechanism (hereinafter also referred to as “single link mechanism”) in which a piston pin and a crank pin are connected by a single link (connecting rod), The crank throw, which is the distance from the center of rotation of the main journal of the crankshaft to the axis of the crankpin, is half the piston stroke (1) unless the center of rotation of the main journal is offset from the cylinder centerline. / 2) On the other hand, in the multi-link mechanism, the upper link and the lower link act like a lever so that the crank throw can be made shorter than half of the (maximum) piston stroke amount. Become. For this reason, shortening the crank throw can reduce the size, improve engine mounting, or increase the compression ratio.By shortening the crank throw, the main journal and the crank pin approach the eccentric direction of the crank pin. As a result, the overlapping portion in the axial direction is increased, and the rigidity and strength are increased.

  In Patent Document 2, there is a crankshaft in order to relieve stress concentration due to bending deformation of the crankshaft due to the load in the eccentric direction of the crankpin acting on the crank rotation center from the crankpin axis due to combustion pressure and explosive force. A technology that disperses stress by providing a stealing part at the corner of the web (crank arm) with the lower part of the crankpin where stress is concentrated, reducing the rigidity of the part, and allowing some deformation Is described.

JP 2008-2224015 A JP 2001-084443 A

  However, when the crank throw is made shorter than half of the (maximum) piston stroke amount by using a multi-link mechanism as in Patent Document 1, it has been found that the following problems occur. Referring to FIG. 13, the crankshaft of a multi-cylinder internal combustion engine generates a torsional moment (hereinafter also referred to as “torsional torque”) T due to resonance. A load P (inertial force) acts in the crankpin width direction γ perpendicular to both the crankshaft direction α and the crankpin eccentric direction β, and a bending moment M around the crankshaft is generated. Here, when the crank throw is “r”, the torque T and the load P are in a relationship of T = rP. Therefore, as the crank throw r becomes shorter, the load P becomes larger even at the same torque T. Therefore, when compared with equivalent piston stroke amounts, in a multi-link mechanism with a short crank throw, the load P acting on the crank pin is larger than in a single link mechanism with a long crank throw.

  Therefore, in the crankshaft of the internal combustion engine to which the multi-link mechanism is applied, not only the load in the crankpin eccentric direction β caused by the above-described explosion force but also the crankpin width direction γ caused by the torsional torque T is described. The influence of the load P must also be fully taken into consideration. Even if a meat stealing portion set for a load caused by explosive force is applied as in Patent Document 2, the expected stress reduction effect Can't get.

  Referring to FIG. 14, due to the influence of load P in the crankpin width direction γ caused by the torsional torque T, stress tends to concentrate on both sides in the crankpin width direction γ in the vicinity of the crankpin. Here, when the crank throw is shortened using the multi-link mechanism as described above, the portion ΔOL where the main journal and the crank pin overlap in the crank pin eccentric direction β increases in the vicinity of the both side portions. Since the rigidity and strength are locally increased, stress concentration is more likely to occur. In particular, when oil holes for lubrication are formed through the crank pins in the diameter direction along the crank width direction γ, stress tends to concentrate at the oil hole portions.

  FIG. 15 shows a predetermined point inside the oil hole where the stress is highest for the # 4 cylinder closest to the flywheel of the in-line four-cylinder internal combustion engine in which the crank throw is made shorter than half the piston stroke amount by using the multi-link mechanism. The graph shows changes for each crank angle, including stress fluctuation at P, torsional deformation around the crankshaft caused by the torsional torque, and bending deformation caused by the explosive force. As shown in the figure, the stress fluctuation (A) at the point P has a strong correlation with the torsional deformation (B) caused by the torsional torque, and almost no correlation with the bending deformation (C) caused by the explosive force. Absent. This is a phenomenon peculiar to an internal combustion engine having a multi-link mechanism with a short crank throw.

  The present invention has been made in view of such circumstances. In the crankshaft of an internal combustion engine in which the crank throw is made shorter than half of the (maximum) piston stroke amount by using a multi-link mechanism, the stress concentration is appropriately adjusted. The main purpose is to reduce or reduce the energy consumption.

  An internal combustion engine to which the present invention is applied includes an upper link whose one end is connected to a piston via a piston pin, and is connected to the other end of the upper link via an upper pin and is connected to a crank pin of a crankshaft. A multi-link type piston-crank mechanism having a lower link and an auxiliary link having one end pivotably supported on the engine body side and the other end connected to the lower link via an auxiliary pin. . A crankshaft of an internal combustion engine according to the present invention includes a main journal rotatably supported on the engine body side, a crank web connecting an axial end portion of the main journal and an axial end portion of the crankpin. The crank throw from the rotation center of the main journal to the axis of the crankpin is set to be shorter than half the piston stroke amount.

  By shortening the crank throw using the multiple link mechanism in this way, it is possible to reduce the size and increase the compression ratio as described above, but the crank pin and the main journal overlap when viewed from the crankshaft direction. Since the portion increases and the rigidity and strength of this portion increase locally, stress concentration tends to be caused with respect to the load caused by the torsional torque around the crankshaft described above.

  Therefore, in the present invention, when the crank web is viewed in a predetermined cross section perpendicular to the axis, the outermost diameter of the crank web at a portion where the main journal and the crank pin overlap in the eccentric direction of the crank pin from the outer periphery of the crank pin. The distance to the line is shorter than the distance from the outer periphery of the crank pin to the outermost diameter line of the crank web in the crank pin eccentric direction.

  According to the present invention, the rigidity of the overlapping portion is reduced by shortening the distance from the outer periphery of the crank pin to the outermost diameter line of the crank web in the overlapping portion in the predetermined cross section perpendicular to the axis. By adopting a structure that allows a certain degree of deformation, it is possible to disperse the stress at the overlap portion caused by the torsional torque around the crankshaft and reduce or alleviate the stress concentration.

The front corresponding view of the crankshaft which shows typically the formation range of the crevice in the crankshaft direction view concerning the 1st example of the present invention. The perspective view which shows the principal part of the crankshaft which concerns on the said 1st Example. The side view which shows the principal part of the crankshaft which concerns on the said 1st Example. Sectional drawing which shows the crankshaft which concerns on the said 1st Example. The perspective view which shows the principal part of the crankshaft which concerns on 2nd Example of this invention. The side view which shows the principal part of the crankshaft which concerns on the said 2nd Example. The perspective view which shows the principal part of the crankshaft which concerns on 3rd Example of this invention. The side view which shows the principal part of the crankshaft which concerns on the said 3rd Example. The perspective view which shows the principal part of the crankshaft which concerns on 4th Example of this invention. The side view which shows the principal part of the crankshaft which concerns on the said 4th Example. The side view which shows the crankshaft which concerns on 5th Example of this invention. The block diagram which shows typically an example of the multilink type piston-crank mechanism which concerns on this invention. Explanatory drawing which shows the relationship between the load which acts on a crankpin resulting from torsion torque, and a crank throw. The front corresponding | compatible figure of the crankshaft by which the oil hole was penetrated and formed in the width direction of the crankpin. Explanatory drawing which shows the stress fluctuation | variation (A), torsion deformation (B), and bending deformation (C) in the point P inside the oil hole of a crankpin.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 12 is a block diagram schematically showing an example of a multi-link piston-crank mechanism (multi-link mechanism) of an internal combustion engine to which the crankshaft of the present invention is applied. A plurality of cylinders (cylinders) 2 into which the pistons 3 are slidably fitted are formed in the cylinder block 1, and a main journal 15 of the crankshaft 4 is rotatably supported.

  The multi-link type piston-crank mechanism is known from the above-mentioned Japanese Patent Application Laid-Open No. 2008-222015. Briefly described, an upper link 6 having one end connected to the piston 3 via a piston pin 5 and the upper link 6 The lower link 9 is connected to the other end of the link 6 via an upper pin 7 and is rotatably attached to the crankpin 8 of the crankshaft 4, and one end (lower end) is connected to the cylinder block 1 as an internal combustion engine body. And an auxiliary link 11 supported at the other end (upper end) and connected to the lower link 9 via an auxiliary pin 10.

  Such a multi-link mechanism has a higher degree of freedom in setting piston stroke characteristics than a single link mechanism in which the piston pin 5 and the crank pin 8 are connected by a single link. By using a thing (for example, characteristics close to simple vibration), it is possible to significantly reduce vibration and noise.

  The crank throw r from the axis of the main journal 15 to the axis of the crankpin 8 is set to be shorter than half of the (maximum) piston stroke amount. As a result, the crank throw r is shortened while maintaining the same engine compression ratio as compared with a general single link mechanism in which the crank throw r is half the piston stroke amount, thereby improving rigidity and strength and reducing the size. Or a high compression ratio can be achieved while maintaining an equivalent crank throw r.

  Further, an auxiliary shaft 13 that is continuous to multiple cylinders is rotatably supported on the cylinder block 1 by a cylinder member 1 via a support member (not shown). The auxiliary shaft 13 has an eccentric shaft portion for each cylinder. 12, and the other end of the auxiliary link 11 is rotatably attached to each eccentric shaft portion 12. Therefore, by changing the rotational position of the auxiliary shaft 13 according to the engine operating state by an actuator (not shown), the position of the eccentric shaft portion 12 that becomes the swing support position of the auxiliary link 11 is changed, and the lower by the auxiliary link 11 is changed. The engine compression ratio changes (variable compression ratio means) in accordance with the change in the motion constraint condition of the link 9. Thus, variable control of the engine compression ratio can be easily realized by using the multi-link type piston-crank mechanism.

  Next, the structure of the crankshaft 4 constituting the main part of the present invention will be described with reference to the first embodiment of FIGS. 1 to 4 show a structure around one crankpin among a plurality of crankpins provided on the crankshaft. Further, in FIG. 1, the shape is simplified for the sake of clarity as compared with FIGS. 2 to 4.

  The crankshaft 4 is provided with a crankpin 8 that is eccentric from the rotation center (axial center / crank rotation center) of the main journal 15 for each cylinder, and the axial end of each crankpin 8 and the axial end of the main journal 15 are provided. The parts are integrally connected by a thin crank web 16. Further, a counterweight 17 is formed to extend from the crank web 16 on the opposite side of the crank pin 8 across the crank rotation center, and each crank web 16 is radially outward from the connecting portion with the crank pin 8. A thrust receiving portion 18 having a predetermined radial width ΔD protruding in a flange shape is provided. The thrust receiving portion 18 has an annular shape having a plane opposite to both axial end surfaces of the lower link 9, receives a thrust load in the crank shaft direction α from the lower link 9, and receives the crank of the lower link 9 with respect to the clamp pin 8. Restricts / prevents movement in the axial direction α. The thrust receiving portion 18 is inserted radially inward from the outer periphery of the crank web 16 at the time of processing.

  Further, the crank web 16 is provided with an interference avoiding recess 19 recessed in the axial direction so as to avoid interference with the lower link 9 on the lower side of the crank pin connecting portion.

  The crankpin 8 is formed with an oil hole 20 extending in a diametrical direction along a crankpin width direction γ that is orthogonal to both the crankpin axial direction α and the crankpin eccentric direction β. Lubricating oil is supplied to the inside of the crankshaft 4 from the cylinder block side via the journal side oil hole 21 opened in the main journal 15, and is supplied to the crankpin bearing portion through the oil hole 20 of the crankpin 8.

  As shown in FIG. 1, each crank web 16 has a recess recessed inward corresponding to a portion 22 where the main journal 15 and the crankpin 8 overlap in the crankpin eccentric direction β when viewed in the crankshaft direction. 23 is formed. That is, most of the recess 23 is formed in the overlap portion 22, extends in the crankpin eccentric direction β so as to cross the side of the oil hole 20, and has a predetermined radial width ΔD. It is greatly recessed inward so as to enter the inner side of the thrust receiving portion 18. That is, the thrust receiving portion 18 is partially cut out at the concave portions 23 on both sides of the crank web 16 around the crankpin 8. Further, the recess 23 is in contact with the (virtual) common tangent line 24 connecting the outer periphery of the crankpin 8 and the outer periphery of the main journal 15, that is, both the outer periphery of the crankpin 8 and the outer periphery of the main journal 15 as viewed in the crankshaft direction. It is greatly recessed inward so as to enter further inside than the common tangent line 24.

  That is, by forming such a recess 23, the main journal 15 and the crankpin 8 are cranked from the outer periphery of the crankpin 8 when the crank web 16 is viewed in a predetermined cross section perpendicular to the axis where the recess 23 is formed. The (shortest) distance R1 to the outermost diameter line of the crank web 16 at the portion 22 overlapping in the pin eccentric direction β is from the outer periphery of the crankpin 8 to the outermost diameter line of the crank web 16 in the crankpin eccentric direction β. Distance R0, that is, the distance R0 of the portion along the crankpin eccentric direction β that is generally the shortest width around the crankpin 8. In this embodiment, as shown in FIG. 1, the concave portion 23 enters the inside of the crank pin 8 at the overlap portion 22 so that the distance R1 is substantially 0 (zero).

  As described above, in the multi-link mechanism, the overlap portion 22 is increased by shortening the crank throw r and the strength and rigidity are improved. On the other hand, the rigidity against the load in the crank pin width direction γ acting by the torsional moment is locally increased. Therefore, stress concentration tends to be caused, and in particular, stress tends to concentrate inside the oil hole 20 formed penetrating in the crank pin width direction γ. In the present embodiment, the concave portion 23 is formed and the distance R1 at the overlap portion 22 is shortened, thereby reducing the strength of the overlap portion 22 and allowing the deformation thereof. The stress concentration can be reduced / relieved, and the recess 23 can reduce the weight.

  In particular, in this embodiment, since the recess 23 is inserted into the common tangent 24, the load along the common tangent 24 is not transmitted, and the rigidity and strength of the overlap portion 22 can be greatly reduced. . Further, in the crank web 16, the thrust receiving portions 18 facing the axial end surfaces of the lower links 9 fitted to the crank pins 8 remain on the upper and lower portions of the crank pins 8 except for the concave portions 23 on both sides. Thereby, the bending rigidity with respect to an explosive force is ensured, and the original function of the thrust receiving part which opposes a thrust load can be ensured.

  Of the plurality of crankpins provided on the crankshaft, the crankpin of the cylinder closest to the flywheel (not shown) is most susceptible to the torsional moment. Therefore, the recess 23 may be formed only in the crank web connected to the crank pin of the cylinder closest to the flywheel. In this case, with respect to the cylinder closest to the flywheel, the stress concentration is reduced and the weight is reduced by the concave portion 23 described above, and the remaining cylinders are not provided with the concave portion 23. A decrease in strength can be avoided.

  Further, the concave portion 23 may be formed only on the crank web closer to the flywheel that is easily affected by the torsional moment, out of the two crank webs located on both sides in the axial direction of the crankpin. In this case, with respect to the crank web on the flywheel side, the stress concentration is reduced and the weight is reduced by the recess 23 described above, and the recess 23 is not provided on the crank web on the anti-flywheel side, thereby forming the recess 23. It is possible to avoid a decrease in rigidity / strength due to.

  In the embodiments described below, the same reference numerals are given to the same components as those in the above-described embodiments, and overlapping description will be omitted as appropriate, and different parts from the above-described embodiments will be mainly described.

  In the second embodiment shown in FIGS. 5 and 6, the recess 23 is inserted to a position corresponding to the inside of the crankpin 8 as viewed in the crankshaft direction, and the axial end surface 8 </ b> A of the crankpin 8 is formed at this recess 23. A part of is exposed. Moreover, the recessed part 23 has entered the innermost side at a position corresponding to the oil hole 20 so as to more appropriately relieve stress concentration in the oil hole 20. That is, the recess 23 is recessed in a circular arc shape that is deepest at a portion along the center line in the width direction of the crankpin 8. The concave portion 23 is provided only in a portion near the crank pin in the axial direction of the crank web 16, and the concave portion 23 is provided in a portion near the main journal 15 in the axial direction of the crank web 16 in order to ensure rigidity and strength. A portion 25 of the thin-walled crank web 16 having no gap remains in a form including a common tangent line 24 (see FIG. 1) that smoothly connects the outer periphery of the main journal 15 and the outer periphery of the crank pin 8.

  Accordingly, when the crank web 16 is viewed in a predetermined cross-section perpendicular to the axis where the concave portion 23 is formed by the concave portion 23 as in the first embodiment, the crank web at the overlap portion 22 extends from the outer periphery of the crank pin 8. 16 (the shortest) distance R1 to the outermost diameter line is further shorter than the distance R0 from the outer periphery of the crankpin 8 to the outermost diameter line of the crank web 16 in the crankpin eccentric direction β. The strength of the crank web is improved by allowing the portion 25 of the thin-walled crank web 16 to remain while reducing the weight and reducing the weight by the recess 23.

  Referring to the third embodiment shown in FIGS. 7 and 8, a communication oil hole that communicates an oil hole 20 that penetrates the crank pin 8 in the radial direction and a journal side oil hole 21 that penetrates the main journal 15 in the radial direction. 26 is formed in the crank web 16 on both sides of the crankpin 8 at an angle from the opening 26A of the crank web 16 opposite to the journal-side oil hole 21 by machining, and the opening 26A is a cap. It is blocked by (not shown).

  In this case, of the crank webs 16A and 16B on both sides of the crankpin 8, the recess 23A of the crank web 16A in which the opening 26A is formed is made smaller than the recess 23B of the crank web 16B in which the opening 26A is not formed. . Specifically, for the crank web 16A on the opening 26A side, a recess 23B is formed over the entire length in the axial direction, whereas for the crank web 16B without the opening 26A, the recess is only in the portion near the crankpin in the axial direction. 23A is formed, and a portion 25A of the crank web 16A remains in a portion near the main journal in the axial direction. Thereby, it is possible to prevent the rigidity and strength of the crank web 16A in which the opening 26A is formed from being excessively lowered.

  In the fourth embodiment shown in FIGS. 9 and 10, a slit-like recess 23C that is recessed inward is formed in the axial center of the side surface in the width direction of the wide crank web 16 including the common tangent line 24 (see FIG. 1). An opening is formed on the side surface. Like the above-described embodiment, the recess 23C can relieve stress concentration and reduce the weight, and the thrust receiving portion 18 can remain over the entire circumference, so that the bending rigidity against the explosive force and the strength against the thrust load can be improved. It will be excellent.

  When the recesses 23 (23A to 23C) are formed as in the first to fourth embodiments described above, a portion of high stress generated in the oil hole 20 of the crankpin 8 opens to the outer periphery of the crankpin 8. Move closer to the opening of the hole. For this reason, the processing for improving the fatigue strength with respect to the oil hole 20, such as induction hardening, polishing, and roller burnishing, may be performed only in the vicinity of the opening. Thereby, productivity can be improved and processing costs can be reduced.

  In the fifth embodiment shown in FIG. 11, the stress concentration caused by the torsional torque is effectively reduced and avoided without using the recess. That is, in the fifth embodiment, among the four crankpins 8 provided on the crankshaft 4, the # 4 cylinder crankpin closest to the flywheel (not shown) and most affected by the torsional moment is provided. 8 is designed so that the bending rigidity around the crankpin eccentric direction β is lower than the bending rigidity of the crankpins 8 of the other cylinders # 1 to # 3. Specifically, the axial length ΔCP1 of the crankpin 8 of the # 4 cylinder is made longer than the axial length ΔCP0 of the crankpin 8 of the other # 1 to # 3 cylinders.

  In this embodiment, the axial length ΔCP1 of the crankpin 8 of the # 4 cylinder is increased so as not to change the center position of the crankpin 8 in the width direction, that is, the pitch between the bores of adjacent cylinders. Therefore, the axial length ΔCW1 of the two crank webs 16 of the # 4 cylinder is made shorter than the axial length ΔCW0 of the crank webs of the other # 1 to # 3 cylinders.

  In this way, the # 4 cylinder crankpin 8 closest to the flywheel is made relatively long to reduce its bending rigidity, resulting in torsional torque peculiar to the multi-link mechanism having a short crank throw r. The stress concentration in the oil hole 20 can be effectively reduced / relieved.

DESCRIPTION OF SYMBOLS 3 ... Piston 4 ... Crankshaft 5 ... Piston pin 6 ... Upper link 7 ... Upper pin 8 ... Crank pin 9 ... Lower link 10 ... Auxiliary pin 11 ... Auxiliary link 15 ... Main journal 16 ... Crank web 20 ... Oil hole 23 ... Concave

Claims (8)

An upper link whose one end is 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 A crankshaft of an internal combustion engine having a multi-link type piston-crank mechanism having an auxiliary link that is pivotally supported by the other end and connected to the lower link via an auxiliary pin.
A main journal rotatably supported on the engine body side, and a crank web connecting the axial end of the main journal and the axial end of the crankpin;
The crank throw from the rotation center of the main journal to the axis of the crankpin is set to be shorter than half of the piston stroke amount.
And, when the crank web is viewed in a predetermined cross section perpendicular to the axis, the outer circumference of the crank pin extends from the outer diameter of the crank web at the portion where the main journal and the crank pin overlap in the eccentric direction of the crank pin. A crankshaft of an internal combustion engine provided with a multi-link type piston-crank mechanism, characterized in that the distance is shorter than the distance from the outer periphery of the crankpin to the outermost diameter line of the crank web in the eccentric direction of the crankpin.   2. The multi-link piston-crank mechanism according to claim 1, wherein an oil hole is formed through the crank pin along a crank pin width direction orthogonal to a crank pin eccentric direction and an axial direction. Crankshaft of internal combustion engine.   When the crank web is viewed in a predetermined cross section orthogonal to the axis, a concave portion is formed in the crank web so as to enter inside a common tangent line connecting the outer periphery of the crank pin and the outer periphery of the main journal. A crankshaft of an internal combustion engine comprising the multi-link type piston-crank mechanism according to claim 1 or 2. A thrust receiving portion having a predetermined width is formed in the crank pin radial direction at the crank pin connecting portion of the crank web facing the axial end surface of the lower link,
The crank web is formed with a recess that enters the inside of the thrust receiving portion,
The multi-link type piston-crank mechanism according to any one of claims 1 to 3, wherein the thrust receiving portion remains at a position corresponding to an upper portion and a lower portion of a crank pin excluding concave portions on both sides. A crankshaft of an internal combustion engine provided.   5. The multi-link piston according to claim 3, wherein the recess is formed only in a crank web connected to a crank pin closest to the flywheel among a plurality of crank pins provided on the crank shaft. A crankshaft of an internal combustion engine provided with a crank mechanism.   The double link according to any one of claims 3 to 5, wherein the concave portion is formed only in a crank web closer to the flywheel among two crank webs positioned on both sides in the axial direction of the crankpin. A crankshaft of an internal combustion engine having a piston-crank mechanism. An upper link whose one end is 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 A crankshaft of an internal combustion engine having a multi-link type piston-crank mechanism having an auxiliary link that is pivotally supported by the other end and connected to the lower link via an auxiliary pin.
A main journal rotatably supported on the engine body side, and a crank web connecting the axial end of the main journal and the axial end of the crankpin;
The crank throw from the rotation center of the main journal to the axis of the crankpin is set to be shorter than half of the piston stroke amount.
And the crankshaft of the internal combustion engine characterized by setting the bending rigidity of the crankpin closest to the flywheel among the plurality of crankpins provided on the crankshaft to be lower than the bending rigidity of other crankpins.   The axial length of the crank pin closest to the flywheel among the plurality of crank pins provided on the clan shaft is set longer than the axial length of the other crank pins. Crankshaft of internal combustion engine.

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