JP2012062796A - Crankshaft of multi-cylinder internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crank shaft for a multi-cylinder internal combustion engine capable of reducing a stress generated at the opening of an oil hole formed in the peripheral surface of a crank pin.SOLUTION: In this internal combustion engine of in-line 4-cylinder type, the crank pin 21d of its fourth cylinder at the tail of the engine 1 is configured so that the opening of the oil hole 25d in the crank pin 21d axial direction is positioned not in the center of the crank pin 21d, but in a position biased toward the engine 1 tail where the stress is low initially. The crank pin 21a of the first cylinder at the forefront of the engine 1 is arranged so that the opening of the oil hole 25a in the crank pin 21a axial direction is positioned not in the center of the crank pin 21a, but in a position biased toward the forefront of the engine 1 where the stress is low initially.

Description

  The present invention relates to a crankshaft of a multi-cylinder internal combustion engine.

  For example, in Patent Document 1, an oil hole opening portion in an oil hole penetrating from a journal portion of a crankshaft to a pin portion is connected to the journal portion and the pin portion as viewed in the axial direction of the crankshaft. A crankshaft formed at a position of 90 ° or −90 ° with respect to the axis K of the crank arm is disclosed.

  In Patent Document 1, the oil hole opening formed on the outer peripheral surface of the pin portion is positioned at 90 ° with respect to the axis K of the pin portion where the generated stress is small, so that the oil in the pin portion is The stress at the hole opening is reduced.

Japanese Patent Laid-Open No. 58-178012

  However, in Patent Document 1, in providing the oil hole opening in the pin portion of the crankshaft, the influence of the adjacent cylinder is not considered, and the pin length direction of the pin portion is relative to the axial direction of the pin portion. The oil hole opening is located at the center of the. Therefore, when the influence from the adjacent cylinder is taken into consideration, the oil hole opening is not in an optimal position, and when the influence of the bending stress increased by the inertia force of the adjacent cylinder is received, There is a problem that the oil hole opening is not located in a portion where the generated stress is minimized.

  Therefore, in the present invention, in the clamp pins at both ends of the crankshaft corresponding to the frontmost cylinder and the rearmost cylinder of the multi-cylinder internal combustion engine, oil holes for supplying lubricating oil from adjacent crank journals are arranged in the length direction of the crankpin. The crank pin is formed so as to be biased toward the crankshaft end side closer to the center than the center.

  In the crankpin located at the front and rear ends of the crankshaft, not by the center of the crankpin, but by the combustion load input to the crankpin at a position deviated from the center of the crankpin to one end side or the other end side of the crankpin. There is a region where the generated stress is reduced. More specifically, in the case of a crankshaft of a multi-cylinder internal combustion engine, the foremost end crankpin located on the most end side of the crankshaft corresponding to the foremost end cylinder is biased toward one end of the crankshaft rather than the center of the foremost end crankpin. There is a region where the stress is reduced at the position where the rearmost crankpin located on the other end side of the crankshaft corresponding to the rearmost cylinder is biased toward the other end of the crankshaft rather than the center of the rearmost crankpin. There is a region where the stress is reduced at a certain position.

  According to the present invention, when the combustion load is input to the crank pin, the oil hole is formed at a position where the stress generated in the crank pin becomes small. can do.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which showed typically schematic structure of the internal combustion engine provided with the crankshaft to which this invention was applied. Explanatory drawing which showed typically the crankshaft in 1st Embodiment of this invention. Explanatory drawing which showed typically the attitude | position of the crankshaft in the timing to which a combustion load is added. Explanatory drawing which showed the direction of the load which acts on each part of the crankshaft of 1st Embodiment in the timing which the combustion load produced in the 4th cylinder. Explanatory drawing which showed the direction of the load which acts on each part of the crankshaft of 1st Embodiment in the timing which the combustion load produced in the 3rd cylinder. Explanatory drawing which showed typically the stress distribution on the crankpin outer peripheral surface in which the oil hole is not formed. Explanatory drawing which showed typically the crankshaft in 2nd Embodiment of this invention. Explanatory drawing which showed the direction of the load which acts on each part of the crankshaft of 2nd Embodiment in the timing which the combustion load produced in the 3rd cylinder. Explanatory drawing which showed the direction of the load which acts on each part of the crankshaft of 2nd Embodiment in the timing which the combustion load produced in the 2nd cylinder.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view schematically showing a schematic configuration of an internal combustion engine including a crankshaft 20 to which the present invention is applied, and shows a posture at a timing when a combustion load (maximum load) is applied.

  In the internal combustion engine 1, a piston pin 3 of a piston 2 and a clamp pin 21 of a crankshaft 20 are connected by a multi-link type piston crank mechanism 4 composed of a plurality of links.

  The multi-link type piston crank mechanism 4 includes an upper link 5 and a lower link 6 that connect the piston 2 and the crankshaft 20, a control link 7 that restricts the movement of the upper link 5 and the lower link 6, and a base of the control link 7. A control shaft 8 having an eccentric shaft portion 9 whose end is slidably connected is generally constituted.

  The piston 2 is slidably disposed in a cylinder 11 formed in the cylinder block 10, and is connected to one end (upper end in FIG. 1) of the upper link 5 via a piston pin 3 so as to be swingable. .

  The other end (the lower end in FIG. 1) of the upper link 5 is rotatably connected to one end of the lower link 6 via the first connecting pin 12.

  The lower link 6 is rotatably attached to the crankpin 21 of the crankshaft 20 at the center thereof.

  One end (upper end in FIG. 1) of the control link 7 that restricts the movement of the lower link 6 is rotatably connected to the other end of the lower link 6 via the second connecting pin 13, and the other end (in FIG. 1). The lower end is supported by a cylinder block 10 which is a part of the internal combustion engine body so as to be swingable. The other end of the control link 7 can be displaced with respect to the internal combustion engine body by the position of the swing fulcrum 14 in order to change the compression ratio of the internal combustion engine. Specifically, a control shaft 8 extending in parallel with the crankshaft 20 is provided, and the other end of the control link 7 is rotatably fitted to an eccentric shaft portion 9 provided eccentric to the control shaft 8.

  An actuator (not shown) is attached to the control shaft 8. By rotating the control shaft 8 with this actuator, the position of the oscillating fulcrum 14 is displaced with respect to the internal combustion engine body, and the piston with respect to the crank angle is displaced. The stroke position of 2 changes, and as a result, the compression ratio is changed.

  FIG. 2 is an explanatory view schematically showing the crankshaft 20 in the first embodiment of the present invention. The crankshaft 20 of the first embodiment is used for an in-line four-cylinder internal combustion engine, and includes four crankpins 21 and a total of five crank journals 22 disposed at both ends of these crankpins 21. A crank arm 23 that connects the crank pin 21 and the crank journal 22, and a counterweight 24 that is formed integrally with a part of the crank arm 23. It is rotatably supported.

  Here, the crankshaft 20 corresponds to the first cylinder in which the leftmost crankpin 21a in FIG. 2 is the front end cylinder of the internal combustion engine 1, and the rightmost crankpin 21d in FIG. The center two crankpins 21b and 21c correspond to the second and third cylinders, which are the intermediate cylinders of the internal combustion engine 1, respectively. The crank pins 21a and 21d are arranged so as to have a phase of 180 ° with respect to the clan pins 21b and 21c.

  The crank journal 22 is 22a, 22b, 22c, 22d, and 22e in order from the front end side of the crankshaft 20 (in order from the left side in FIG. 2).

  The crank arm 23 is 23a, 23b, 23c, 23d, 23e, 23f, 23g, and 23h in order from the front end side of the crankshaft 20 (in order from the left side in FIG. 2).

  The counterweight 24 is formed integrally with the crank arms 23a, 23d, 23e, 23g, and 23h, and sequentially from the front end side of the crankshaft 20 (in order from the left side in FIG. 2), 24a, 24b, 24c, 24d, 24e.

  Each crankpin 21 is supplied with lubricating oil from an adjacent crank journal 22 through an oil hole 25. The oil hole 25 in the first embodiment has one end opened on the outer peripheral surface of the crankpin 21 and the other end opened on the outer peripheral surface of the crank journal 22. Lubricating oil on the outer peripheral surface of the crank journal 22 is supplied to the outer peripheral surface of the crank pin 21 through the oil hole 25. Lubricating oil is supplied to the outer peripheral surface of the crank journal 22 from a main gallery (not shown).

  That is, the lubricating oil is supplied to the crank pin 21a from the crank journal 22a through the oil hole 25a. Lubricating oil is supplied to the crank pin 21b from the crank journal 22b through the oil hole 25b. Lubricating oil is supplied to the crankpin 21c from the crank journal 22c through the oil hole 25c. Lubricating oil is supplied to the crank pin 21d from the crank journal 22d through the oil hole 25d. 2 denotes a flywheel attached to the rear end of the crankshaft 20.

  Here, when the oil hole 25 is opened on the outer peripheral surface of the crankpin 21, stress concentration occurs in the opening portion. Therefore, the timing at which the combustion load is applied to the crankpin 21, that is, the timing at which the in-cylinder pressure load becomes maximum. It is required to open the oil hole 25 at a position where the stress is low in the stress distribution of the crankpin 21.

  Therefore, the opening position of the outer peripheral surface of the crank pin 21 in the oil hole 25 is determined in consideration of various influences acting on the crank pin 21 at the timing when the combustion load is applied to the crank pin 21.

  In the multi-link type piston crank mechanism 4 of the first embodiment, as shown in FIGS. 1 and 3, the angle of the crank pin 21 is 36 ° after top dead center (ATCD 36 °) is the timing when the combustion load is applied. The direction of the crankpie load at this timing is inclined by 23 ° with respect to the cylinder axis, as indicated by the arrow A in FIGS. Here, the arrow B in FIG. 1 indicates the direction of the load applied to the first connection pin 12 at the timing when the combustion load is applied, and the arrow C in FIG. 1 is the load applied to the second connection pin 12 at the timing when the combustion load is applied. Indicates the direction.

  When a combustion load is applied to the crankpin 21, the crankpin 21 is bent so as to be convex in the direction in which the combustion load is applied, and a compression stress is applied to the crankpin 21 on the side where the combustion load is input. The tensile stress is generated on the side (opposite side) opposite to the side where the combustion load of the crank pin 21 is input, and the position between these becomes the neutral position of the compressive stress and the tensile stress.

  In other words, with respect to the bending deformation of the clamp pin 21 due to the combustion load acting on the crank pin 21, when the crank pin 21 is viewed in the axial direction, stress passes through the center of the crank pin 21 in a direction perpendicular to the input direction of the combustion load. The neutral position, which is a region that becomes smaller, exists.

  Therefore, the opening position in the circumferential direction of the outer peripheral surface of the crank pin 21 of the oil hole 25 passes through the center of the crank pin 21 of the crank pin 21 where the combustion load acts as viewed in the axial direction of the crank shaft 20 and at the timing when the combustion load becomes maximum. It is set to be near the intersection of a straight line orthogonal to the direction of action of the combustion load on the crankpin 21 and the outer peripheral surface of the crankpin 21.

  As described above, by setting the opening position of the oil hole 25 in the circumferential direction of the crank pin at the neutral position of the compressive stress and the tensile stress generated in the crank pin 21 at the timing when the combustion load becomes the maximum, The stress generated in the opening of the oil hole 25 on the outer peripheral surface can be reduced.

  When a combustion load is input to the crankpin 21, a reaction force against the input combustion load is applied to both ends of the crankpin 21. At this time, a large reaction force is applied to both ends of the crankpin 21. That is not the same.

  The arrangement of the crank pins 21, the configuration and shape of the link mechanism such as the lower link 6 and the upper link 5 that link the crank pin 21 and the piston pin 3, the influence of the inertia force generated in the adjacent cylinder at the same timing as this combustion load, etc. However, as a whole, the reaction force acting on the crankpin 21 of the cylinder in which the combustion load is generated is influenced by the other crankpin 21 ( The reaction force acting on both ends of the crankpin 21 of the cylinder in which the combustion load is generated is larger than the reaction force acting on the crankpin 21) of the cylinder in which the combustion load is not generated, and is different from each other.

  4 and 5 show the crankpin of the crankshaft 20 on the basis of the load F acting on the crankpin 21 of the cylinder where the combustion load is generated at the timing when the combustion load is generated, that is, when the cylinder pressure load becomes maximum. 21 is an explanatory diagram schematically showing the direction and magnitude of the load applied to the crank journal 22 and FIG. 4 shows the timing at which the combustion load is generated in the fourth cylinder, which is the cylinder at the rear end of the internal combustion engine 1, FIG. 5 shows the timing when the combustion load is generated in the third cylinder which is the intermediate cylinder of the internal combustion engine 1.

  As shown in FIG. 4, if a load of F acts downward on the crankpin 21 d at the timing when the combustion load is generated in the fourth cylinder at the rear end of the internal combustion engine 1, the cranks of the third cylinder and the second cylinder A load having a magnitude of (1/3) F acts on the pins 21c and 21b, and a load having a magnitude of (1/3) F acts on the crankpin 21a of the first cylinder.

  Further, an upward load (171/448) F acts on the crank journal 22e, and an upward load (387/448) F acts on the crank journal 22d. A load of magnitude (125/448) F acts upward, a load of magnitude (24/448) F acts downward on the crank journal 22b, and a downward load (61 / 448) A load of magnitude F acts.

  At the timing when the combustion load is generated in the fourth cylinder at the rear end of the internal combustion engine 1, upward loads are applied to both ends of the crank pin 21d from the crank journals 22d and 22e on both sides. A load having a magnitude of (387/448) F is applied upward from the crank journal 22d to the end of the internal combustion engine 1 that is one end of the crankpin 21d at this time, and the internal combustion engine that is the other end of the crankpin 21d. A load having a magnitude of (171/448) F acts upwardly from the crank journal 22e at the end on the rear end side of the engine 1. Thus, the load acting on both ends of the crank pin 21d is not uniform, and the load acting on the end portion on the front end side of the internal combustion engine 1 becomes relatively large. Therefore, at the timing when the combustion load is generated in the fourth cylinder. On the outer peripheral surface of the crank pin 21d, there is a region where the stress is reduced not at the center of the crank pin 21d but at a position biased toward the other end side (right side in FIG. 2) of the crank pin 21d.

  FIG. 6 shows a crank pin 21d that does not have an oil hole 25d and intersects a plane that is orthogonal to the direction of combustion load acting on the crank pin 21d and that includes the center axis of the crank pin 21d. The vertical axis represents the stress level and the horizontal axis represents the position along the axial direction of the crankpin 21. As is apparent from FIG. 6, the load acting on both ends of the crank pin 21d in this way is orthogonal to the direction of action of the combustion load acting on the crank pin 21d and includes the central axis of the crank pin 21d. On the outer peripheral surface of the crankpin 21d that intersects the flat surface, there is a region where the stress is reduced not at the center of the crankpin 21d but at a position biased toward the other end of the crankpin 21d.

  Therefore, in the crank pin 21d corresponding to the fourth cylinder of the in-line four-cylinder internal combustion engine, in addition to the setting of the opening position of the oil hole 25 in the circumferential direction of the crank pin, the stress is not originally in the center of the crank pin 21d. By setting the opening position in the axial direction of the crank pin 21d of the oil hole 25d at a position biased toward the rear end side of the low internal combustion engine 1, the stress concentration generated in the opening of the oil hole 25d can be alleviated. Further, since stress concentration at the opening of the oil hole 25d can be alleviated, the crank pin 21d can be reduced in weight by reducing the shaft diameter of the crank pin 21d, or the combustion load acting on the crank pin 21d can be set large. It becomes possible to do.

  In the in-line four-cylinder internal combustion engine 1, the overall shape of the crankshaft 20 is generally symmetrical. Therefore, the crankpin 21a corresponding to the first cylinder tends to be the crankpin 21d corresponding to the fourth cylinder described above. Is reversed.

  That is, at the timing when the combustion load is generated in the first cylinder at the front end of the internal combustion engine 1, a load having an upward magnitude acts from the crank journal 22a on the end portion of the front end side of the internal combustion engine 1 which is one end of the crank pin 21a. A load is applied upward from the crank journal 22b to the end of the internal combustion engine 1 that is the other end of the crankpin 21a. However, the load applied from the crank journal 22b to the other end of the crankpin 21a It becomes relatively larger than the load acting on one end of the pin 21a from the crank journal 22a.

  Therefore, due to the load acting on both ends of the crankpin 21a, there is a region on the outer peripheral surface of the crankpin 21a where stress is reduced not at the center of the crankpin 21a but at a position biased toward one end of the crankpin 21a.

  More specifically, the outer peripheral surface of the crankpin 21a intersects with the plane including the central axis of the crankpin 21a and is orthogonal to the direction of the combustion load acting on the crankpin 21a due to the load acting on both ends of the crankpin 21a. Above, there is a region where the stress is reduced not at the center of the crankpin 21a but at a position biased toward one end of the crankpin 21a.

  Therefore, in the crank pin 21a corresponding to the first cylinder of the in-line four-cylinder internal combustion engine, in addition to the setting of the opening position of the oil hole 25 in the circumferential direction of the crank pin, the stress is not originally in the center of the crank pin 21a. What is necessary is just to set the opening position in the crankpin 21a axial direction of the oil hole 25a in the position biased to the low internal combustion engine 1 front end side.

  Next, the crankpin 21c corresponding to the third cylinder which is an intermediate cylinder of the in-line four-cylinder internal combustion engine 1 will be described.

  As shown in FIG. 5, if a load of F acts downward on the crankpin 21c at the timing when the combustion load is generated in the third cylinder of the internal combustion engine 1, the crankpins 21a of the first cylinder and the fourth cylinder are applied. , 21d, a load of (1/3) F acts downward, and a load of (1/3) F acts on the crank pin 21b of the second cylinder upward.

  Further, an upward load (23/448) F acts on the crank journal 22e, and an upward load (387/448) F acts on the crank journal 22d. A load of magnitude (133/448) F acts upward, a load of magnitude (136/448) F acts upward on the crank journal 22b, and upward (57 / 448) A load of magnitude F acts.

  At the timing when the combustion load is generated in the third cylinder of the internal combustion engine 1, upward loads are applied to both ends of the crank pin 21c from the crank journals 22c and 22d on both sides. A load having a magnitude of (133/448) F is applied upward from the crank journal 22c to the end of the internal combustion engine 1 which is one end of the crankpin 21c at this time, and the internal combustion engine which is the other end of the crankpin 21c. A load having a magnitude of (387/448) F acts on the end portion on the rear end side of the engine 1 upward from the crank journal 22d. Thus, the load acting on both ends of the crankpin 21c is not uniform, and the load acting on the end portion on the rear end side of the internal combustion engine 1 is relatively large, so the timing at which the combustion load is generated in the third cylinder. In the outer peripheral surface of the crankpin 21c, there is a region where the stress is reduced not at the center of the crankpin 21c but at a position biased to one end side (left side in FIG. 2) of the crankpin 21c.

  More specifically, the outer peripheral surface of the crank pin 21c intersects with the plane including the central axis of the crank pin 21c and is orthogonal to the direction of the combustion load acting on the crank pin 21c due to the load acting on both ends of the crank pin 21c. Above, there is a region where stress is reduced not at the center of the crankpin 21c but at a position biased toward one end of the crankpin 21c.

  Therefore, in the crankpin 21c corresponding to the third cylinder of the in-line four-cylinder internal combustion engine 1, in addition to the setting of the opening position of the oil hole 25 in the circumferential direction of the crankpin, it is not the center of the crankpin 21c but originally. By setting the opening position of the oil hole 25c in the axial direction of the crank pin 21c at a position biased toward the front end side of the internal combustion engine 1 where the stress is low, the stress concentration generated in the opening of the oil hole 25c can be alleviated.

  In the in-line four-cylinder internal combustion engine 1, the overall shape of the crankshaft 20 is generally symmetrical, so that the crankpin 21 b corresponding to the second cylinder tends to be the crankpin 21 c corresponding to the third cylinder described above. Is reversed.

  That is, at the timing when the combustion load is generated in the second cylinder of the internal combustion engine, an upward load from the crank journal 22b acts on the front end side of the internal combustion engine 1 which is one end of the crankpin 21b. A load is applied upward from the crank journal 22c to the end on the rear end side of the internal combustion engine 1, which is the other end of 21b. It becomes relatively larger than the load acting on the other end from the crank journal 22c.

  Therefore, due to the load acting on both ends of the crankpin 21b, stress is applied to the outer peripheral surface of the crankpin 21b not at the center of the crankpin 21b but at a position biased to the other end side (left side in FIG. 2) of the crankpin 21b. There is a region that becomes smaller.

  More specifically, the outer peripheral surface of the crank pin 21b intersects with the plane including the central axis of the crank pin 21b and is orthogonal to the direction of the combustion load acting on the crank pin 21b due to the load acting on both ends of the crank pin 21b. Above, there is a region where the stress is reduced not at the center of the crank pin 21b but at a position biased toward the other end of the crank pin 21b.

  Therefore, in the crank pin 21b corresponding to the second cylinder of the in-line four-cylinder internal combustion engine 1, in addition to the setting of the opening position of the oil hole 25 in the circumferential direction of the crank pin, the crank pin 21b is not located at the center but originally What is necessary is just to set the opening position in the crankpin 21b axial direction of the oil hole 25b in the position biased to the rear end side of the internal combustion engine 1 with low stress.

  In the first embodiment, since the piston pin 3 and the crank pin 21 are connected by the multi-link type piston crank mechanism 4, the single link type piston crank in which the piston pin and the crank pin are connected by a connecting rod. Compared with the internal combustion engine of the mechanism, the combustion load increases due to the lever ratio, so that the stress concentration at the opening of the oil hole can be effectively reduced at the timing when the combustion load becomes maximum.

  In the first embodiment, the amount of offset from the center of the crank pins 21b, 21c of the oil holes 25b, 25c opened in the crank pins 21b, 21c corresponding to the intermediate cylinders is the same for the front end cylinder and the rear end cylinder. The oil holes 25a and 25d opening in the corresponding crank pins 21a and 21d are smaller than the offset amount from the center of the crank pins 21a and 21d. This is because the difference in reaction force acting on both ends of the crankpin 21 corresponding to the intermediate cylinder where the combustion load is generated is the crankpin of the frontmost cylinder where the combustion load is generated or the crankpin of the last cylinder where the combustion load is generated. This is because the difference in reaction force acting on both ends of 21 becomes relatively larger.

  Next, a second embodiment of the present invention will be described. In the second embodiment, the present invention is applied to an in-line three-cylinder internal combustion engine.

  FIG. 7 is an explanatory view schematically showing the crankshaft 30 when applied to an in-line three-cylinder internal combustion engine.

  The crankshaft 30 includes three crankpins 31, a total of four crank journals 32 disposed at both ends of these crankpins 31, a crank arm 33 that connects the crankpin 31 and the crank journal 32, and a crank arm And a counterweight 34 formed integrally with the cylinder block 10. The crank journals 32 are rotatably supported by the cylinder block 10.

  The lower link 6 of the multi-link piston crank mechanism 4 is rotatably attached to the crank pin 31 as in the first embodiment described above.

  Here, the crankshaft 30 corresponds to the first cylinder in which the leftmost crankpin 31a in FIG. 7 is the front end cylinder of the internal combustion engine, and the rightmost crankpin 31c in FIG. This corresponds to the third cylinder which is the end cylinder, and the center crankpin 31b corresponds to the second cylinder which is the intermediate cylinder of the internal combustion engine. Further, the crank pins 31a, 31b, 31c are arranged so as to have a phase of 120 °.

  The crank journal 32 is 32a, 32b, 32c, 32d in order from the front end side of the crankshaft 30 (in order from the left side in FIG. 7).

  The crank arm 33 is 33a, 33b, 33c, 33d, 33e, 33f in order from the front end side of the crankshaft 30 (in order from the left side in FIG. 7).

  The counterweight 34 is integrally formed with respect to all the crank arms 33 and becomes 34a, 34b, 34c, 34d, 34e, 34f in order from the front end side of the crankshaft 30 (in order from the left side in FIG. 7). Yes.

  Each crankpin 31 is supplied with lubricating oil from an adjacent crank journal 32 through an oil hole 35. The oil hole 35 in the second embodiment also has one end opened on the outer peripheral surface of the crankpin 31 and the other end opened on the outer peripheral surface of the crank journal 32. Lubricating oil on the outer peripheral surface of the crank journal 32 is supplied to the outer peripheral surface of the crank pin 31 through the oil hole 35. Lubricating oil is supplied to the outer peripheral surface of the crank journal 32 from a main gallery (not shown).

  That is, the lubricating oil is supplied to the crank pin 31a from the crank journal 32a through the oil hole 35a. Lubricating oil is supplied to the crank pin 31b from the crank journal 32b through the oil hole 35b. Lubricating oil is supplied to the crank pin 31c from the crank journal 32c through the oil hole 35c. Note that reference numeral 36 in FIG. 7 denotes a flywheel attached to the rear end of the crankshaft 30.

  Also in the second embodiment, the opening position in the circumferential direction of the outer peripheral surface of the crank pin 31 of the oil hole 35 is subjected to a combustion load as viewed in the axial direction of the crankshaft 30 for the same reason as in the first embodiment described above. The crankpin 31 is set so that it passes through the center of the crankpin 31 and is near the intersection of a straight line perpendicular to the direction of action of the combustion load on the crankpin 31 and the outer peripheral surface of the crankpin 31 at the timing when the combustion load becomes maximum. .

  8 and 9 show the crankpin of the crankshaft 30 based on the load F acting on the crankpin 31 of the cylinder where the combustion load is generated at the timing when the combustion load is generated, that is, when the cylinder pressure load becomes maximum. FIG. 8 is an explanatory view schematically showing the direction and magnitude of the load applied to the crank journal 31 and the crank journal 32. FIG. 8 shows the timing at which the combustion load is generated in the third cylinder which is the rear end cylinder of the internal combustion engine. Reference numeral 9 denotes a timing at which a combustion load is generated in the second cylinder which is an intermediate cylinder of the internal combustion engine.

  As shown in FIG. 8, when a combustion load is generated in the third cylinder at the rear end of the internal combustion engine and a large F load is applied to the crankpin 31c, the crankpins of the second and first cylinders are applied. A load having a size of (1/6) F acts on 2b and 21a downward.

  Further, an upward load (175/448) F acts on the crank journal 32d, and an upward load (360/448) F acts on the crank journal 32c. A load having a magnitude of (20/448) F acts upward, and a load having a magnitude of (37/448) F acts on the crank journal 32a upward.

  At the timing when the combustion load is generated in the third cylinder at the rear end of the internal combustion engine, upward loads are applied to both ends of the crank pin 31c from the crank journals 32c and 32d on both sides. At this time, a load having a magnitude of (360/448) F acts on the end of the internal combustion engine, which is one end of the crankpin 31c, upward from the crank journal 32c, and the internal combustion engine is the other end of the crankpin 31c. A load having a magnitude of (175/448) F acts on the rear end portion upward from the crank journal 32d. Thus, the load acting on both ends of the crankpin 21d is not uniform, and the load acting on the end portion on the front end side of the internal combustion engine 1 is relatively large. Therefore, at the timing when the combustion load is generated in the third cylinder. On the outer peripheral surface of the crankpin 31c, there is a region where the stress is reduced not at the center of the crankpin 31c but at a position biased toward the other end side (right side in FIG. 7) of the crankpin 31c.

  More specifically, on the outer peripheral surface of the crankpin 31c that intersects with the plane including the central axis of the crankpin 31ac and is orthogonal to the direction of the combustion load acting on the crankpin 31c due to the load acting on both ends of the crankpin 31c. Has a region where the stress is reduced not at the center of the crankpin 31c but at a position biased toward the other end of the crankpin 31c.

  Therefore, in the crank pin 31c corresponding to the third cylinder of the in-line three-cylinder internal combustion engine, in addition to the setting of the opening position of the oil hole 35 in the crank pin circumferential direction described above, not the center of the crank pin 31c but originally the stress. By setting the opening position of the oil hole 35c in the axial direction of the crank pin 31c at a position biased toward the rear end side of the low internal combustion engine, stress concentration generated at the opening of the oil hole 35c can be reduced. Further, since stress concentration at the opening of the oil hole 35c can be alleviated, the crank pin 31c can be reduced in weight by reducing the shaft diameter of the crank pin 31c, or the combustion load acting on the crank pin 31c can be set large. It becomes possible to do.

  Even in an in-line three-cylinder internal combustion engine, the overall shape of the crankshaft 30 is generally bilaterally symmetric, so that the crankpin 31a corresponding to the first cylinder tends to be the same as the crankpin 31c corresponding to the third cylinder described above. Vice versa.

  That is, at the timing when the combustion load is generated in the first cylinder at the front end of the internal combustion engine, an upward load from the crank journal 32a acts on the end of the internal combustion engine at the front end side which is one end of the crankpin 31a. A load is applied upward from the crank journal 32b to the end on the rear end side of the internal combustion engine, which is the other end of 31a, but the load applied from the crank journal 32b to the other end of the crankpin 31a is greater than that of the crankpin 31a. It becomes relatively larger than the load acting from one end of the crank journal 32a.

  Therefore, due to the load acting on both ends of the crank pin 31a, there is a region where the stress is reduced on the outer peripheral surface of the crank pin 31a not at the center of the crank pin 31a but at a position biased to one end side of the crank pin 31a.

  More specifically, the outer peripheral surface of the crankpin 31a intersects with the plane including the central axis of the crankpin 31a perpendicular to the direction of the combustion load acting on the crankpin 31a by the load acting on both ends of the crankpin 31a. Above, there is a region where stress is reduced not at the center of the crankpin 31a but at a position biased toward one end of the crankpin 31a.

  Therefore, in the crankpin 31a corresponding to the first cylinder of the in-line three-cylinder internal combustion engine, in addition to the setting of the opening position of the oil hole 35 in the circumferential direction of the crankpin, not the center of the crankpin 31a but originally the stress. What is necessary is just to set the opening position in the crankpin 31a axial direction of the oil hole 35a in the position biased to the low internal combustion engine front end side.

  Next, the crankpin 31b corresponding to the second cylinder which is an intermediate cylinder of the inline three-cylinder internal combustion engine will be described.

  As shown in FIG. 9, when a load of F acts downward on the crankpin 31b at the timing when the combustion load is generated in the second cylinder of the internal combustion engine, the crankpins 31a of the first cylinder and the third cylinder, A load having a magnitude of (1/6) F acts on 31c downward.

  Further, an upward load (300/448) F acts on the crank journal 32c, and an upward load (214/448) F acts on the crank journal 32b. A load having a magnitude of (94/448) F acts downward, and a load having a magnitude of (1/448) F acts downward on the crank journal 32d.

  At the timing when the combustion load is generated in the second cylinder of the internal combustion engine 1, upward loads are applied to both ends of the crank pin 31b from the crank journals 32b and 32c on both sides. A load of (214/448) F is applied upward from the crank journal 32b to the end of the internal combustion engine, which is one end of the crank pin 31b at this time, and the internal combustion engine is the other end of the crank pin 31b. A load having a magnitude of (300/448) F acts on the rear end side upward from the crank journal 32c. Thus, the load acting on both ends of the crankpin 31b is not uniform, and the load acting on the end portion on the rear end side of the internal combustion engine becomes relatively large. Therefore, at the timing when the combustion load is generated in the second cylinder. On the outer peripheral surface of the crankpin 31b, there is a region where the stress is reduced not at the center of the crankpin 31b but at a position biased to one end side (left side in FIG. 7) of the crankpin 31b.

  More specifically, the outer peripheral surface of the crankpin 31b intersects with the plane including the central axis of the crankpin 31b and is orthogonal to the direction of the combustion load acting on the crankpin 31b due to the load acting on both ends of the crankpin 31b. Above, there is a region where stress is reduced not at the center of the crank pin 31b but at a position biased toward one end of the crank pin 31b.

  Therefore, in the crankpin 31b corresponding to the second cylinder of the in-line three-cylinder internal combustion engine, in addition to the setting of the opening position of the oil hole 35 in the circumferential direction of the crankpin, the stress is originally not the center of the crankpin 31b. By setting the opening position of the oil hole 35b in the axial direction of the crank pin 31b at a position biased toward the front end side of the low internal combustion engine, the stress concentration generated at the opening of the oil hole 35b can be alleviated.

  In the case of the inline three-cylinder crankshaft 30, since the arrangement of the crankpins 31 is 120 ° apart, the combustion acting on the crankpin 31b at the timing when the combustion load is generated in the second cylinder serving as the intermediate cylinder. On the outer peripheral surface of the crankpin 31b that is orthogonal to the direction in which the load is applied and intersects the plane including the central axis of the crankpin 31b, the stress is theoretically reduced to a position that is biased toward one end of the crankpin 31b. Although there is a region, the offset amount from the center of the crankpin 31b is smaller than the offset amount in the crankpins 31a and 31c, and can be substantially regarded as the center of the crankpin 31b.

  Moreover, in each embodiment mentioned above, although the application example to an inline 4 cylinder internal combustion engine and an inline 3 cylinder internal combustion engine was shown, it is also possible to apply to an inline 8 cylinder internal combustion engine or an inline 6 cylinder internal combustion engine.

20 ... Crankshaft 21 ... Crankpin 22 ... Crank journal 25 ... Oil hole

Claims (4)

A crankshaft of a multi-cylinder internal combustion engine in which crank journals are arranged at both ends of each crankpin,
In a crankshaft of a multi-cylinder internal combustion engine having an oil hole for supplying lubricating oil from an adjacent crank journal to the clamp pin, the oil hole opening on an outer peripheral surface of the crank pin,
In the crankpins at both ends of the crankshaft corresponding to the foremost end cylinder and the rearmost end cylinder of the multi-cylinder internal combustion engine, the oil hole is at the end of the crankshaft where the crankpin is closer than the center in the length direction of the crankpin A crankshaft of a multi-cylinder internal combustion engine, wherein the crankshaft is formed so as to be offset toward each side.   The crankshaft is a crankshaft of an in-line four-cylinder internal combustion engine, and in the intermediate position crankpin corresponding to the cylinder located between the rearmost cylinder and the frontmost cylinder, the length direction of the intermediate position crankpin 2. The crankshaft of a multi-cylinder internal combustion engine according to claim 1, wherein the oil hole is formed so as to open at a position that is biased toward an intermediate position crankpin adjacent to the center.   A straight line that passes through the center of the crankpin of the crankpin to which the combustion load is applied and is orthogonal to the direction of action of the combustion load at the timing when the combustion load that acts on the crankpin is maximized when viewed from the crankshaft axial direction; The crankshaft of a multi-cylinder internal combustion engine according to claim 1 or 2, wherein an opening position of the oil hole in the circumferential direction of the crankpin is set in the vicinity of an intersection with the outer peripheral surface of the cylinder.   The multi-cylinder internal combustion engine according to any one of claims 1 to 3, wherein the crank pin is connected to a piston pin of a piston via a multi-link type piston crank mechanism including a plurality of links. Crankshaft.

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