JPH037609Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crankshaft for an internal combustion engine, and particularly to the shape of a fillet R provided to avoid stress concentration.

[Conventional technology]

In the crankshaft of an internal combustion engine, the crank journal, which is supported by the bearing of the cylinder block, and the crank pin, to which the connecting rod is attached, have a crank web placed between them. A fillet R is provided at the joint portion to alleviate bending stress. However, even if a fillet R is provided, the stress distribution along the curved surface of the fillet R exhibits stress concentration characteristics with a maximum stress point where the stress increases rapidly, so there remains a concern that metal fatigue may be accelerated. It's on. Therefore, in 1983,
- As shown in No. 151519, two fillets R are provided to form a two-step shape, and the two fillets R are joined at the part of the maximum stress that occurs in the case of a single fillet R curved surface. An idea has been made. It has been pointed out that by providing such a fillet R, stress is dispersed and the maximum stress can be reduced.

[Problem that the invention attempts to solve]

Incidentally, the stress distribution along the circumferential direction of the crank journal and crank pin also exhibits stress concentration characteristics, as there is a maximum stress point where the stress increases rapidly, as in the case along the fillet R curved surface. The size of the fillet R is considered in consideration of the stress level that occurs at the point of maximum stress along the circumferential direction, so
Based on the fillet R considered at this time, providing two fillets R uniformly over the entire circumference as described above is better than providing a single fillet R. Large space required. For this reason, there is a problem in that the axial length of the crankshaft must be kept within a predetermined length, and the dimensions of the crank journal and crank pin must be shortened.

Therefore, the technical problem of the present invention is to reduce the fillet R along the circumferential direction of the crank journal and crank pin.
By varying the shape of the fillet R, the maximum stress level generated in the fillet R can be lowered, and the axial length of the crank journal and crank pin can be made longer.

[Means for solving problems]

According to the crankshaft of the present invention, the means taken to solve the above technical problem are as follows:
The purpose is to gradually change the radius of the fillet R by maximizing the portion where the maximum stress is generated among the joint portions provided with the stress.

[Effect]

According to this means, the stress dispersion effect by the fillet R is maximized at the point of maximum stress, and a gentle stress distribution is formed over the entire circumference of the joint portion.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, in a crankshaft 1, a crank web 4 is disposed between a crank journal 2 supported by a bearing portion of a cylinder block 5 and a crank pin 3 to which a connecting rod 6 is attached. Fillets Rr ₁ and r ₂ are provided at the joint portions of the crank journal 2 and the crank pin 3, respectively. The radii of these fillets Rr ₁ and r ₂ gradually change along the circumferential direction of the crank journal 2 and crank pin 3, and are not constant.
Note that 7 and 8 are bearing metals having a width corresponding to the width of the crank journal 2 and the crank pin 3.

Since the method of gradually changing the fillets Rr ₁ and r ₂ is qualitatively the same, only the fillet Rr ₁ provided on the crank pin 3 will be described below.

In FIG. 2, the ranges in which the fillets Rr ₁ are provided are indicated by symbols A ₁ to _{A 9} , and approximately 1/4 of the entire circumference of the crank pin 3 corresponds to this range. This range includes fillets
It includes the point where the bending stress generated at the joint where Rr ₁ is installed is maximum, and is an imaginary line connecting the center O ₁ of the crank pin 3 and the center O ₂ of the crank journal 2 shown in the figure. The intersection point _A5 between l and the outer peripheral edge of the crank pin 3 corresponds to the maximum stress point. With this point A ₅ as a reference, A ₁ to A ₄ and A ₆ to _{A 9} are carved at equal angles from the center O ₁ on the outer circumferential line of the crank pin 3, and the fillet Rr ₁ of each point gradually changes. The method of mounting is as shown in the diagram in FIG. That is, the radius of the fillet Rr ₁ is maximized at the maximum stress point of point A ₅ , and becomes smaller as it goes toward the point A ₁ and _the point A ₉ . Note that the dashed-dotted line shown in FIG. 3 shows the case where a constant fillet Rr ₁ is provided over the entire circumference as in the conventional case. Therefore, in the vicinity of point _A5 , the radius of fillet _Rr1 is larger than before, but in the vicinity of points _A1 to _A3 and points _A7 to
In A ₉ , the radius of the fillet Rr ₁ becomes smaller. On average, the average radius of the fillet Rr ₁ in this embodiment is smaller than the radius of the conventional constant fillet R. Here, gradually changed fillet
To provide Rr ₁ , as shown in FIG. 4, the peripheral edge of the disc-shaped roller 9 is rounded in accordance with the diagram in FIG. 3, and the roller 9 is pressed against the fillet Rr ₁ . is provided.

The results of measuring the stress generated at the joint of the fillet Rr ₁ as described above are shown in Figure 5, and when compared with the conventional stress distribution given by the dashed-dotted line, the maximum stress at point A ₅ is shown. Stress is reduced. This is because, conventionally, the stress that increases rapidly near the point _A5 is dispersed to other points by providing the fillet _Rr1 having a large radius. Therefore, at points A ₁ to _{A 3} and points A ₇ to _{A 9} , the stress is slightly larger than before, but on the other hand, the maximum stress, which has a large effect on metal fatigue, is significantly reduced. Fatigue strength is improved.

Furthermore, in order to improve the fatigue strength, in this embodiment, the radius of the fillet Rr ₁ is set small except for the vicinity where the maximum stress occurs at the joint part of the fillet Rr ₁ , and the radius of the fillet Rr 1 is set small, and Since there is a fillet Rr ₁ that gradually changes only in approximately 1/4 of the point, and a fillet R that is equivalent to point A ₁ and A is provided in the remaining approximately 3/4, the actual axial length of the crank pin 3 is large. can. This ensures a large lubricating oil level between the bearing metal 8 and the crank pin 3.

[Effect of idea]

In this way, according to the present invention, the radius of the fillet R is gradually changed by setting the maximum radius at the point where the maximum stress occurs among the joint parts where the fillet R is provided, so that the radius of the fillet R is gradually changed. It forms a gentle stress distribution over the circumference and lowers the maximum stress level, so it is possible to improve the margin of fatigue strength. Further, as a result of gradually changing the fillet R, a joint portion with a small fillet R can be formed, and the axial length of the crankshaft and crank pin can be increased. This increases the lubricating oil level and reduces wear on the bearing metal on the crankshaft and crankpin.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an engine equipped with a crankshaft according to an embodiment of the present invention, and FIG.
Fig. 1 is a cross-sectional view showing the distribution of the fillet R, Fig. 3 is a diagram showing the course of gradual change in the radius of the fillet R, and Fig. 4 is a diagram showing the gradual change of the radius of the fillet R. FIG. 5, which is a diagram showing the provision of the modified fillet R, is a diagram showing the stress distribution of the fillet R when the crankshaft according to the embodiment of the present invention is used. 1... Crankshaft, 2... Crank journal, 3... Crank pin, 4... Crank web, r ₁ , r ₂ ... Fillet R.

Claims (1)

[Scope of utility model registration request] In a crankshaft in which a fillet R is provided at the joint portion between the crank journal, the crank pin, and the crank web, the portion where the maximum stress is generated is maximized among the joint portions provided with the fillet R, and the fillet R is A crankshaft characterized by gradually changing the radius of R.