JPS6213811A - Serration connecting part of connecting rod for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent cracking by forming the inner circumferential surface of the opening of a bolt fitting hole with a taper surface so as to suppress the stress concentration at the serration part. CONSTITUTION:The inner circumferential surface of a bolt inserting hole 6 at the cap 2 side end part is formed with a taper surface 10, and the part continuing to the taper surface 10 is formed with a cylindrical surface 11 of a given diameter and further a female thread part 12 is formed so as to be continued to the cylindrical surface 11. The cylindrical surface 11 extends in parallel with the center line of the bolt, and the taper surface 10 is sloped by the angle B of 30 deg. with regard to the center line of the bolt, and the diameter of end part at the tooth crest 15 side of a serration tooth 8 is larger than that of the tooth bottom 16 side of the serration tooth 8. The depth D of the taper surface 10 is somewhat longer than the height H of the serration tooth 8. Thus, the serration part nearest to the bolt is eliminated, and the part most liable to subject to stress concentration can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a connecting rod of an internal combustion engine, and relates to the structure of a serration joint for fixing a metal cap to a large end of a connecting rod.

(Prior Art) For example, as described in Japanese Patent Application Laid-open No. 57-94120, a structure in which a connecting rod and a metal break are connected using serrations has a structure in which the connecting surface (mating surface) is along the longitudinal direction of the connecting rod. It is often used when the surface is inclined to the direction.

In such a structure, stress due to inertia force or the like during operation is applied to the serrations, so there is a risk that cracks may occur in the tooth bottoms of the serrations.

Conventionally, as a countermeasure to this problem, a method has been generally adopted in which the edges of the serration teeth facing the bolt mounting hole are chamfered, thereby alleviating the concentration of stress on the serrations in the vicinity of the bolt. .

Furthermore, as a countermeasure against cracks, the above publication describes a technique of reducing the height of one of the serration teeth.

Furthermore, as a technique for solving the same problem, Japanese Patent Publication No. 26-6354 discloses that no serrations are provided near the bolt mounting holes on the mating surface of the connecting rod and the metal cap; A technique is described in which serrations are provided only in the portions that are separated from each other.

(Problems to be Solved by the Invention) However, simply by chamfering the edges of the serration teeth as described above, stress concentration on the serration portions cannot be sufficiently avoided. Moreover, since thread chamfering must be finished by hand, there are problems such as low work efficiency and low finishing accuracy.

Further, when the height of the serration teeth is reduced as in the above-mentioned Japanese Patent Application Laid-Open No. 57-94120, the meshing area between the teeth is reduced, resulting in a reduction in bonding strength.

Furthermore, as in Japanese Patent Publication No. 26-6354, in order to provide serrations and flat portions on the mating surfaces, it is essential that the entire area of the mating surfaces be sufficiently wide. is not possible to employ such technology. In other words, since the area of the serrations becomes narrow, it is difficult to obtain sufficient bonding strength with small or medium-sized connecting rods.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a method for solving problems near the end surface (mating surface) of the inner circumferential surface of the bolt insertion hole provided in the large end of the connecting rod and the metal cap. The inner circumferential surface of the frontage is formed by a tapered surface with a larger diameter at the opening side end, and the length of the tapered surface in the direction of the center line of the bolt mounting hole is set to be greater than the height of the teeth of the serrations. .

(Function) According to the above structure, by forming the inner circumferential surface of the opening of the bolt mounting hole with a tapered surface, the stress that exists in the serration portion close to the bolt, that is, in the conventional structure, is most likely to be concentrated. part ceases to exist.

Also, since the end face of the serration teeth facing the bolt mounting hole is formed by the above-mentioned tapered surface, the distance from the bolt center line to the engagement point of the ends of the serration teeth! ! ! l (distance 11 in the bolt radial direction) is long. Therefore, an extremely large force is not applied to the +lj1 junction point of the serration tooth end group, and extremely large stress is not concentrated on the bottom of the serration tooth end.

Furthermore, since the tapered surface is formed deeper than the tooth bottom of the serration, the tooth bottom surface and the inner surface of the bolt mounting hole (cheaper surface) intersect at an obtuse angle, and the bolt mounting larger side of the tooth bottom surface The end is located away from the outer circumference of the bolt. Therefore, stress is effectively dispersed at the end of the tooth bottom on the bolt mounting hole side.

(Embodiment) In FIG. 2, the large end of the connecting rod 1 and the metal cap 2 are each provided with serrations 3.4 on their end faces. The connecting rod 1 has a bolt insertion hole 6 (a female threaded hole) into which the bolt 5 is screwed, and the gap 2 has a bolt insertion hole 7 into which the bolt 5 is inserted. The connecting rod 1 and the kit ship 2 are connected by bolts 5 with the serrations 3.4 engaged.

The connecting surface M (virtual plane) of the serrations 3.4 includes the crank pin center flP, and the longitudinal center line R of the connecting rod 1
For example, it is inclined at an angle A of 30°. bolt 5
The center line S (the center line of the bolt insertion hole 6.7) is the joining surface M
extends at right angles to.

As shown in FIG. 3, which is a partial view from the ■-■ arrow in FIG. . Although not clearly shown, #i19 of Seret Shicon 4 in Fig. 2 also extends parallel to the crank pin center line P.
The key 11 is provided on the entire mating surface of the knob 2.

As shown in FIG. 1, which corresponds to the enlarged schematic view of FIG.
0, one continuous portion of the tapered surface 10 is formed of a cylindrical surface 11 of a constant diameter, and a female threaded portion 12 is formed continuous with the cylindrical surface 11.

The cylindrical surface 11 extends parallel to the bolt center line S, and its diameter is somewhat larger than the root diameter of the female threaded portion 12.

The tapered surface 10 is inclined at an angle B of, for example, 30° with respect to the bolt center line S, and the tooth tip surface 15 of the serration tooth 8
The diameter of the side end portion is larger than the diameter of the tooth bottom surface 16 side of the serration tooth 8. The depth D (length in the direction parallel to the bolt center line S) of the tapered surface 10 is slightly longer (for example, by 0.5 to 0.7) than the height H of the serrations 6F+8. Therefore, the small diameter end portion 17 of the tapered surface 10 is located between the root surface 16 and the cylindrical surface 11, and the portion 17 is inclined with respect to the cylindrical surface 11 at an obtuse angle C of 150°.

The inner peripheral surface of the bolt insertion hole 7 of the cap 2 is generally entirely formed of a cylindrical surface with a constant diameter, and a tapered surface 20 is formed at the end on the contact rod 1 side.

The tapered surface 20 also has the same dimensions and shape as the tapered surface 10, and is inclined at an angle of, for example, 30'' with respect to the bolt center line S, and the diameter of the end on the top side of the serration tooth 9 is equal to the bottom surface. It is larger than the diameter of the side.Also, the tapered surface 2
The depth of 0 is slightly longer (for example, by 0.5 to 0.7 m) than the height of the serration teeth 9.

When the engine is in operation, a particularly large force is applied to the serrations near the bolt 5 due to inertia and the like. However, as shown in FIG. 4, which is a schematic diagram of the IV-IV rJA plane of FIG.
There is no portion 25 (portion indicated by double-dashed line hatching in FIG. 4) where stress tends to concentrate.

Furthermore, since the end surface of the serration tooth 8 facing the bolt insertion hole 6 is formed by a tapered surface 10, the bolt center line S
The distance L (distance in the bolt radial direction) from the serration tooth end to the engagement point m is good.

Therefore, an extremely large force is not applied to the engagement point m of the serration tooth end, and a large stress is not concentrated on the tooth bottom end 26 adjacent to the tapered surface 10.

Further, the tooth root surface 16 and the tapered surface 10 intersect at an obtuse angle C, and the tooth root end 26 is also located further away from the bolt center line S than the cylindrical surface 11. Therefore, the root end 2
At 6 the stress is effectively distributed.

Moreover, a cylindrical surface 11 is provided between the tapered surface 10 and the female threaded portion 12.
is provided, and since the tapered surface 10 is separated from the female threaded portion 12, the tightening of the female threaded portion 12 from the bolt 5 [
The force is also regulated when it is intensively transmitted to the bottom end portion 26 of the tooth.

In this way, stress is prevented from concentrating on the serrations 3 (particularly on the tooth bottom end 26) in the vicinity of the bolt insertion hole 6, so that cracks do not occur in the tooth bottom end 26 and the like.

The serrations 4 of the cap 2 are also prevented from cracking for the same reason.

(Effects of the Invention) As explained above, according to the present invention, the inner surface of the end portion of the bolt insertion hole 6 adjacent to the serrated seam joint portion is formed into a tapered surface 10.
Moreover, since the depth D of the tapered surface 10 is made larger than the serration tooth height H, it is possible to suppress concentration of stress on the serration joint part around the bolt insertion hole 6 and prevent cracks in this part. Can be done.

Moreover, the present applicant has developed a tool suitable for machining the tapered surface 10, and by using this tool, the machining of the tapered surface 10 can be mechanized, so that work efficiency and machining accuracy can be sufficiently increased.

In addition, according to the present invention, there is no need to lower the height of the serration teeth or provide a wide flat part on the joint surface as in the past, so the joint strength of the serrations 3.4 can be sufficiently increased, and small or medium-sized It is possible to obtain a connecting structure that can be used without any problem for the connecting rod 1.

(Other Embodiments) It is also possible to install the tapered surface 10 only in the bolt insertion hole 6 of the connecting rod 1.

Further, the dimensions, angle, etc. of the tapered surface 10 can be varied. Note that the diameter of the large diameter part of the tapered surface 10 and the angle B1
If the depth D is set large, the stress dispersion effect on the serrations 3 can be enhanced, but on the other hand, the area of the serration joint (effective area of the serrations 3.4)
may decrease, resulting in a decrease in bond strength. Therefore, it is generally preferable that the dimensions and angle of the tapered surface 10 be set as large as possible within a range that can provide a predetermined bonding strength of 1q at the serration bonding portion.

[Brief explanation of the drawing]

Fig. 1 is a schematic enlarged cross-sectional view of an embodiment of the present invention, Fig. 2 is a partially cutaway front partial view of an embodiment of the invention, Fig. 3 is a partial view taken along the ■-■ arrow in Fig. 3, and Fig. 4. is a partial schematic cross-sectional view taken along line IV-IV in FIG. 1; 1... Connecting rod, 2... Metal cap, 3.4...
・Serration, 5... Bolt, 6.7... Bolt mounting hole, 8.9... Serration tooth, 10.20.
...Tapered surface, D...Tapered surface depth, H...Height of serration tooth

Claims (2)

[Claims] (1) Connect the end face of the large end of the connecting rod and the end face of the metal cap with serrations, fix the metal cap to the large end with a bolt installed in the bolt mounting hole that passes through the serration joint, and Among the inner peripheral surfaces of the mounting hole, the inner peripheral surface of the opening near the end face is formed by a tapered surface with a larger diameter at the opening side end, and the length of the tapered surface in the direction of the center line of the bolt mounting hole is equal to the tooth of the serration. A serration joint of a connecting rod for an internal combustion engine, characterized in that the height is set larger than the height of the connecting rod. (2) The internal combustion engine according to claim 1, wherein a cylindrical surface with a constant diameter is provided between the female thread of the bolt mounting hole of the large end of the connecting rod and the inner peripheral surface of the opening formed by the tapered surface. serration joint of connecting rod.