JPS5852087B2 - Bolts and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bolt, particularly the structure of a four-piece connecting rod bolt, and a method for manufacturing the same.

A specially designed connecting rod bolt is normally used at the end of the connecting rod in a heat engine fc, and is considered an important component in engine-related applications.

In other words, complex forces such as the intense vertical inertia of the connecting rod, the twisting of the crankshaft, and bending stress act on the inner and outer points of the mating surfaces of the large end of the connecting rod and the cap, and they tend to open from each other. Therefore, the outer diameter of the bolt shaft is constantly affected by micro-movement contact.

For this reason, so-called stress erosion and corrosion (fretting) occur.
(rrosion) Phenomenon 1: It is crowded.

In order to avoid interference due to stress corrosion corrosion, connecting rod bolts as shown in FIGS. 1 and 2 have been conventionally used as typical examples.

That is, in FIG. 1, reference numeral 1' indicates an elliptical head, and since the head moves vertically within a cylinder, the elliptical head is generally restricted in many cases.

After polishing, the shaft 2 is finished to dimensions within strict tolerances, and the lower neck 3 is slightly undercut to avoid interference with the wall of the mating hole.

On the other hand, in FIG. 2, 1'' is a head, and shaft portion 2' is a helical groove having a locking element with a lead in the direction opposite to the lead of the screw, which is an example of a connecting rod bolt driven into a mating hole.

In addition, all 4 are tightening screws. However, recent automobile engines have become more diverse and tend to be faster.

Naturally, with this increase in speed, the momentum of the connecting rod itself also increases,
It is exposed to severe high-speed motion due to the reciprocating inertia and centrifugal force of the connecting rod itself, as well as other complex high-order synthetic stresses such as bending and torsion of the rough shaft.

Therefore, since connecting rod bolts are used under the above-mentioned severe conditions, maintaining and guaranteeing their mechanical quality must always be at its best.

First of all, every possible precaution is taken, such as using alloy steel for the material, requiring a large number of manufacturing steps, and using a special thread grade for threads.

In response to these demands, connecting rod bolts such as those shown in FIGS. 1 and 2 have been provided, but they are not perfect, and have a polished shaft finish and a high undercut under the neck.

The present invention aims to provide a connecting rod bolt and a method for manufacturing the same which eliminates such conventional drawbacks, and the present invention will be explained in detail below using one embodiment.

FIG. 3 is a front view of the connecting rod bolt in the present invention.

In the figure, 5 is an elliptical head, and 6 is the first part after correction processing of length L-1 of the uneven notches (narrations) formed in the axial direction over a length L from the neck. As shown in FIG. 4, it is firmly temporarily fixed by driving or press-fitting into the hole 10 provided in the large end portion 9 of the connecting rod.

That is, the diameter of the first notch 6 is made larger than the inner diameter d0 of the hole 10 to enable the press-fitting and fixing.

This situation is shown by dotted line 11 (see Figure 4). Naturally, this connecting rod bolt is properly tightened with a nut 12 during final assembly, but the press-fitting and driving fixation 1 ensures that it is prevented from loosening and turning, which contributes to preventing engine trouble.

Then, the second notch 7 of length l (however, L/2 or more) which is straightened in the same phase following the first notch 6 is cold straightened and the diameter d is a constant value (however, the hole diameter d1 (corresponding) are uniformly corrected, and d is fitted into dl with tight tolerances in a non-fitting state.

Of course, there is no play or tight fit between this length l.

In this way, a two-way fitted state is formed between L-1 of the first notch 6 and press-fitting by press-fitting and driving, and one part of the second notch 7 is a blind fit.

FIG. 5 shows an expanded enlarged view of increments 6 and 7.

However, the dimensions are not comparable to other countries.

That is, as shown in FIG. 6, the first notch 6 has n teeth (diameter D) that bite into the mating hole 10 (see FIG. 4) at the top of the notch (width = t).

This tooth is followed by a second notch 7 as shown in FIG.
After undergoing cold straightening for length l, the peak width T is slightly flattened, the diameter d of notch 7 is smaller than the diameter of notch 6, and it is fit into the mating hole 10 (diameter d1) with severe dimensions and tolerances. They are mated.

Note that the joining line between the large end 9 of the connecting rod and the cap 13 shown in FIG. 4 is a line where stress corrosion corrosion is likely to occur.
As shown in the figure, there is a slight clearance 1 to avoid interference.
It is recommended to provide 4.

This relief 14 is made to be wider than the valley diameter of the notch 7.

Note that 8 is generally a portion equal to the root diameter of the screw 84.

In this way, the present invention only constitutes grooves in the axial direction that are continuous on the shaft in the same phase of the driving part and the blind fitting part, so the machining can be simplified, mass production can be achieved, and costs can be reduced. can be measured.

Each notch firmly bites into the mating hole, has an excellent locking effect, and can withstand high-speed engine rotation.
Accidents due to loosening will be completely eliminated.

In addition, since the second continuous notch undergoes cold straightening on the outer periphery by l length, the outer diameter is uniformly controlled within severe dimensions and can be used safely in accordance with the large end hole of the connecting rod. Also, since it has a serrated outer diameter, it has a strong ability to resist bending force.

Next, the manufacturing method will be described.

First, as shown in FIG. 9, a shaft part 15 having a predetermined outer diameter for forming a head 5, a first notch, and a second notch and a threaded part are formed by ordinary cold heading from a round steel material. Using a bolt material having a shaft portion 16 that forms a
A straightening die 1 having a tapered convex ring 17 for straightening at the center is formed by forming uneven notches on the outer diameter in the axial direction by rolling or the like over the length, as shown in FIG. 10.
8, it is driven so that the outer diameter becomes the outer diameter d1ζ over the length l, or cold straightening is performed by press-fitting, etc., and the shape of each tooth tip is amplified from the width t in Fig. 6 to the width T in Fig. 7. do.

In this way, cold work hardening, equalization of surface roughness, and other harmful surface defects are removed.

Therefore, very effective results can be obtained in controlling the outer diameter of the connecting bolt and maintaining the overall quality.

Furthermore, since the straightening die 18 guarantees roundness,
Even if the first notch 6 is eccentrically formed, the convex ring 17 of the die 18 allows constant cold straightening, and connecting rod bolts can be mass-produced within a certain tolerance with little variation in quality control.

Further, since each portion of the second notch 7 and the peak portion T are both subjected to cold working, the surface strength is high and the influence of so-called stress erosion corrosion is extremely small.

As explained above, according to the manufacturing method of the present invention, the cutting process under the neck radius and the polishing process of the shaft can be omitted, so the economical effect is significant. Since continuous axial grooves are constructed, the machining process can be simplified, leading to mass production and cost reduction.

In addition, the outer circumference of the second continuous notch is cold straightened by a length l, so the outer diameter is uniformly controlled within strict dimensions, and can be used with confidence by matching the connecting rod wide end hole. can.

Furthermore, each notch is in the same direction as the axial center of the bolt, and instead of cutting across the metal fibers and weakening them, they are subjected to cold straightening over a length l, which increases the strength in the axial direction. The unique surface hardening property makes it resistant to external forces such as bending.

However, it has a much stronger effect on stress corrosion corrosion.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing a conventional general connecting rod bolt, Figure 3 is a diagram showing a connecting rod bolt of the present invention, and Figure 4 is a diagram showing a connecting rod bolt of the present invention.
The figure shows the state in which the bolt of the present invention is used in the connecting rod of an internally twisted engine, Figure 5 is an expanded enlarged view of the notches, Figures 6 and 7 are cross-sectional views showing the tops of the notches, and Figure 8 9 is a diagram showing another embodiment of the bolt of the present invention, FIG. 9 is a diagram showing the material of the bolt of the present invention, and FIG. 10 is a sectional view showing a straightening die. 5... Head, 6... First notch, 7.
...Second notch, 9...Big end of connecting rod,
10...hole, 14...escape, 17...
...Convex ring, 18...° straightening die.

Claims (1)

[Claims] 1. When a bolt is inserted into a hole pre-drilled in a member to be fastened and fastened, first and second irregularities of a certain length are formed on the circumference of the shaft from the neck of the bolt. The shape of the notch is set in stages,
The first notch is a press-fit fit, and the second notch is a lock-fit fit. 2. The bolt according to claim 1, wherein a relief portion of a certain length is provided in the center of the second uneven notch. 3. Roll a concave-convex notch with a length L from the lower part of the neck of the bolt material, press fit or drive it into a straightening tool that has a built-in hole diameter smaller than the outer diameter of this notch, and make it shorter than the initial notch length L. is a bolt in which the first notch of L-7 and the second notch of length l are formed by cold straightening the notched outer diameter to a constant value for length l of L/2 or more. manufacturing method.