JP4514876B2 - Crankshaft of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crankshaft of an internal combustion engine, and more particularly to a rounded surface shape in a fillet portion between a crankpin and other shaft member and a crank arm.
[0002]
[Prior art]
FIG. 1 shows a general crankshaft, in which a crankpin 1 is eccentrically disposed between journals 2, and the journal 2 and the crankpin 1 are integrally coupled by a pair of crank arms 3. The fillet portion (base corner portion) P1 between the crankpin 1 and the crank arm 3 and the fillet portion P2 between the journal 2 and the crank arm 3 are respectively rounded.
[0003]
FIG. 3 shows a conventional single round type fillet portion P1, and the rounded surface 30 is formed in a partial circle (quarter shape) with a single radius of curvature R0, and the surface 1a of the crankpin 1 and the crank arm 3 are formed. Are smoothly connected to the end face 3a.
[0004]
FIG. 4 shows an improved version of the conventional example, showing a two-stage rounded fillet portion P1, a first-stage rounded surface 31a having a large curvature radius R1 smoothly connected to the surface 1a of the crankpin 1, and a crank arm. 3 is combined with a second rounded surface 31b having a small curvature radius R2 smoothly connected to the third end surface 3a.
[0005]
[Problems to be solved by the invention]
Along with the increase in engine output, the crankshaft is also required to have improved strength, and the strength of the fillet portion where stress is concentrated is also required to be improved along with improvements in shaft diameter and material.
[0006]
In the single radius type of FIG. 3, the curvature radius R0 is increased in order to improve the strength. However, since the curvature radius R0 and the axial width L of the radius surface 30 are the same value, the curvature radius R0 The axial width L of the rounded surface 30 also increases in proportion to the increase. Then, the arrangement space of the crankpin bearing metal 10 is narrowed, the axial width of the bearing metal 10 has to be narrowed, the surface pressure of the bearing metal 10 becomes high, and it becomes impossible to cope with high output in this respect. .
[0007]
In order to cope with this, if the crankpin 1 is lengthened to secure the arrangement space for the bearing metal 10, the entire crankshaft becomes longer and the engine becomes larger.
[0008]
In the two-stage round type of FIG. 4, the strength against stress is maintained by setting the radius of curvature R1 on the crankpin surface 1a side to which a large stress is applied to a large curvature radius R1, while the crank arm end surface 3a having a relatively small stress. By setting the radius surface 31b on the side to a small radius of curvature R2, the axial width L of the entire radius surface 31 is made smaller than the large radius of curvature R1, thereby making the axial arrangement space of the crankpin bearing metal 10 small. Sufficiently securing the width of the bearing metal 10 can be prevented.
[0009]
However, since two round surfaces 31a and 31b having different radii of curvature (R1, R2) are joined together to form the entire round surface 31, the stress distribution is divided into two different patterns at the joint A of the round surfaces 31a and 31b. The stress peaks are generated at two locations, and this causes a problem in the strength against the stress.
[0010]
In addition, when forming the rounded radius surface 31 of the two-step round shape, a template is first manufactured as a prototype of the two-step rounded surface, and the surface of the grinding wheel is trimmed to the two-step rounded shape following the template. In addition, every time grinding is performed several times, the grindstone surface must be re-trimmed with a template, which takes time and effort.
[0011]
OBJECT OF THE INVENTION
The object of the present invention is to relieve the stress applied to the fillet portion and improve the strength while securing the axial arrangement space of the bearing metal for high engine output.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 of the present application is a crankshaft in which a journal (2) and a crankpin (1) eccentric from the journal (2) are coupled together by a crank arm (3). , The fillet portion (P1) between the crank pin (1) and the crank arm (3) and the fillet portion (P2) between the journal (2) and the crank arm (3) 6), and each of the round surfaces (5, 6) is formed in a partial elliptical shape based on an ellipse whose major axis is parallel to the crankshaft core, and the basic ellipse of each round surface (5, 6). The ratio of the major axis to the minor axis is 2 : 1.
[0013]
The invention according to claim 2 is the crankshaft of the internal combustion engine according to claim 1, wherein a half value of the major axis of the base ellipse of the radius surface is set to 0 with respect to the shaft diameter of the crankpin or journal connected to the fillet portion. .05 times.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, although partially overlapping with the above description, the general structure of the entire crankshaft will be described first. In the crankshaft, the crankpin 1 is eccentrically disposed between the journals 2, and the journal 2 and the crankpin 1 are integrally coupled by a pair of crank arms 3.
[0016]
The journal 2 is rotatably supported by a main bearing 11 formed in a crankcase or the like via a main bearing metal 12, and the crankpin 1 is attached to a crankpin receiver 15 formed on the large end side of the connecting rod 14. The bearing metal 10 is rotatably connected.
[0017]
Round surfaces 5 and 6 are formed on the fillet portion (root corner portion) P1 between the crankpin 1 and the crank arm 3 and the fillet portion P2 between the journal 2 and the crank arm 3, respectively.
[0018]
FIG. 2 shows an example in which the present invention is applied to the fillet portion P1 between the crankpin 1 and the crank arm 3, and the rounded surface 5 has a partially elliptical shape. The ellipse C0 which is the basis of the rounded surface 5 has a major axis 2X direction parallel to the crankshaft core O1 (FIG. 1), and the rounded surface 5 is formed by utilizing 1/4 of the elliptical C0. .
[0019]
Therefore, the portion with the largest radius of curvature of the rounded surface 5 is smoothly connected to the surface 1 a of the crankpin 1, and the radius of curvature of the rounded surface 5 is the largest with respect to the end surface 3 a of the crank arm 3. Are smoothly connected to each other, and the entire round surface 5 is continuous without having a seam on the way. Further, since ¼ of the ellipse C0 is used, the axial width L of the rounded surface 5 is a half (that is, X) of the major axis 2X of the basic ellipse C0, and the radial width W of the rounded surface 5 is obtained. Is one half (ie, Y) of the minor axis 2Y of the basic ellipse C0.
[0020]
The ratio of the major axis 2X to the minor axis 2Y of the basic ellipse C0, in other words, the ratio of the axial width L to the radial width W of the rounded surface 5 is approximately 2: 1. The axial width L is set larger than the thickness t1 of the bearing metal 10.
[0021]
The relationship between the shaft diameter D1 of the crankpin 1 and the major axis 2X of the rounded surface 5 is preferably set so that one half (ie, X) of the major axis 2X is about 0.05 times the crankpin shaft diameter D1. When the ratio is within the range in which the strength against stress can be maintained, an increase in the axial width L of the rounded surface 5 can be suppressed as much as possible. As a specific example, the rounded surface 5 is formed on the basis of an ellipse of about X = 5 mm with respect to the crankpin 1 having a shaft diameter D1 of about 100 mm.
[0022]
When the ratio of the major axis 2X to the minor axis 2Y is set to about 2: 1, the maximum curvature radius on the crank pin surface 1a side and the crank arm end surface 3a are reduced while the axial width L of the rounded surface 5 is made as short as possible. It is possible to prevent the difference from the minimum curvature radius on the side from becoming extremely large.
[0023]
In addition, when the half of the major axis 2X (that is, X) is larger than about 0.05 times the crankpin shaft diameter D1, the strength against stress increases, but the axial width of the crankpin bearing metal 10 is increased. Will begin to be sacrificed. On the other hand, when half of the major axis 2X (that is, X) is smaller than about 0.05 times the crankpin shaft diameter D1, the strength against stress is lowered.
[0024]
2, the fillet portion P1 between the crankpin 1 and the crank arm 3 has been described. However, the present invention can be applied to the rounded surface 6 of the fillet portion P2 between the journal 2 and the crank arm 3 in FIG. As in the case of 2, a round surface based on an ellipse can be formed.
[0025]
However, when comparing the crankpin 1 and the journal 2, one crankpin 1 for one cylinder corresponds to the in-cylinder pressure, and two journals correspond. Since the crankpin 1 is manufactured with a diameter smaller than that of the journal 2, the effect of the partial elliptical rounded surface applied to the crankpin is more conspicuous for higher engine output.
[0026]
[Other Embodiments]
(1) The ratio of the major axis 2X to the minor axis 2Y of the ellipse is not limited to 2: 1 and can be changed according to the stress distribution applied to the fillet portion depending on the type of engine.
[0027]
(2) The magnification of the half of the major axis 2X (ie, X) with respect to the shaft diameter D1 of the crankpin 1 etc. is not limited to the above-mentioned 0.05 times, and depending on the type of engine, It is possible to change according to such stress distribution.
[0028]
As explained above, according to the present invention,
(1) Since the rounded surface 5 (or 6) formed in the fillet portion P1 (or P2) of the crankshaft has a partially elliptical shape based on an ellipse C0 whose major axis 2X is parallel to the crankshaft core O1, The radius of curvature of the surface 5 smoothly changes from a large value to a small value as it goes from the crankpin surface 1a side to the crank arm end surface 3a side. As a result, the crank pin surface 1a side portion to which a large stress is applied maintains the strength against the stress due to the large radius of curvature, whereas the crank arm end surface 3a side portion to which a relatively small stress is applied has a small curvature radius to the axis of the round surface 5. The axial width of the bearing metal 10 can be secured by keeping the direction width L small, and the surface pressure of the bearing metal 10 can be kept low without increasing the length of the crankshaft.
That is, it is possible to keep the strength against the stress applied to the fillet portion P1 while suppressing an increase in the crankshaft length by suppressing an increase in the axial width L of the rounded surface 5.
[0029]
(2) Since the rounded surface 5 has a partially elliptical shape that smoothly connects from the surface of the crank pin surface 1a and the like shaft member to the crank arm end surface 3a, a rounded surface seam is formed in the middle as in the two-stage rounded shape of FIG. Does not occur, resulting in a stress distribution in which stress peaks are separated.
That is, the stress distribution can be relaxed to a gentle distribution, and the strength against stress can be stabilized.
[0030]
(3) Since the rounded surface 5 has a partially elliptical shape, it is not necessary to trim the grindstone using a template as in the two-stage rounded shape of FIG. Can be easily processed.
[0031]
(4) When the basic ellipse C0 of the rounded surface 5 formed in the fillet portion P1 is an ellipse having a ratio of the major axis 2X to the minor axis 2Y of approximately 2: 1 as in the invention of the second aspect, the rounded surface 5 While preventing the axial width L of the shaft from being reduced as much as possible, it is possible to prevent the difference between the maximum curvature radius on the crankpin surface 1a side (the shaft member surface side) and the minimum curvature radius on the crank arm end surface 3a side from becoming extremely large. it can.
[0032]
(5) As in the third aspect of the invention, a half of the major axis 2X of the basic ellipse C0 of the rounded surface 5 formed in the fillet portion P1 is equal to the shaft diameter D1 of the crankpin 1 etc. connected to the fillet portion P1. When it is about 0.05 times, the axial width L of the rounded surface 5 can be sufficiently suppressed while maintaining the strength against stress.
[Brief description of the drawings]
FIG. 1 is a front view of a general crankshaft.
FIG. 2 is an enlarged front view of a fillet portion to which the present invention is applied.
FIG. 3 is an enlarged front view of a fillet portion of a conventional example.
FIG. 4 is an enlarged front view of a fillet portion of another conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crank pin 2 Journal 3 Crank arm 5, 6 R-surface 10 Crank pin bearing metal 12 Main bearing metal

Claims (2)

In a crankshaft in which a journal (2) and a crankpin (1) eccentric from the journal (2) are coupled together by a crank arm (3),
The fillet portion (P1) between the crankpin (1) and the crank arm (3) and the fillet portion (P2) between the journal (2) and the crank arm (3) are respectively provided with rounded surfaces (5, 6). )
Each of the round surfaces (5, 6) is formed in a partial ellipse shape whose major axis is based on an ellipse parallel to the crankshaft core, and the basic ellipse of each round surface (5, 6) has a major axis and a minor axis. The crankshaft of the internal combustion engine, characterized in that the ratio is 2 : 1. The crankshaft of the internal combustion engine according to claim 1,
A crankshaft of an internal combustion engine, wherein a half value of a major diameter of a base ellipse of a rounded surface is about 0.05 times a shaft diameter of a crankpin or a journal connected to a fillet portion.

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