JP2618159B2 - Hollow torsion bar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow torsion bar used for, for example, a vehicle suspension mechanism.

[0002]

2. Description of the Related Art A torsion bar has an effective portion having a predetermined length and a pair of terminal grips located at both ends of the effective portion. A torsional load is applied to the effective portion via the terminal grip. It is supposed to be. A detent part such as a serration is provided in the terminal grip part. The outer diameter of the terminal grip is larger than the outer diameter of the effective part, and a tapered part is formed between the effective part and the terminal grip.

Conventionally, solid torsion bars have been used in suspension mechanisms for passenger cars, trucks, industrial vehicles, and the like. Although the solid torsion bar has a good track record of use, it is disadvantageous in reducing the weight of the suspension mechanism due to its heavy weight. Therefore, adoption of a hollow torsion bar is desired.

[0004]

SUMMARY OF THE INVENTION From such a demand,
Studies have been made on hollow torsion bars made of steel hollow material. However, since the hollow torsion bar has severer conditions than a solid torsion bar with respect to fatigue fracture and corrosion, it cannot be used at all simply by using a hollow material.

[0005] In particular, in the case of a hollow torsion bar in which a terminal grip portion and a tapered portion are formed at the end of a hollow material by hot upset processing, in a durability test, there was a case where the terminal grip portion and the tapered portion were damaged from the vicinity. The cause is considered to be minute internal flaws, decarburization, scale, etc. generated during upset processing. Seamless pipes and ERW pipes are known as hollow materials, and it is often thought that seamless pipes do not have breaks because they do not have welds. However, it is problematic to use a spring member, such as a torsion bar, to which a large torsional load is applied. On the other hand, the electric resistance welded pipe or the electric resistance welded drawn pipe can extremely reduce the damage on the inner surface other than the welded seam portion, but in many cases, the welded seam portion is a starting point of fatigue and breaks early. For this reason, conventionally,
Severe stress conditions used in suspension mechanisms, etc.
It is not practical to use an electric resistance welded tube for the material of the shock bar
Was thought to be.

In putting a hollow torsion bar into practical use, it is necessary to provide a durability comparable to a solid torsion bar by avoiding breakage near the end and breakage from a weld seam portion on the inner surface as described above. There is. Accordingly, an object of the present invention is to provide a hollow torsion bar having excellent durability and corrosion resistance.

[0007]

SUMMARY OF THE INVENTION The present invention, which has been developed to achieve the above object, comprises an effective portion to which a torsional load is applied during use, and an end located at the end of the effective portion and having a greater thickness than the effective portion. It is made of a steel hollow material having a terminal grip portion and a tapered portion located between the effective portion and the terminal grip portion.
A straight tubular hollow torsion bar, wherein a steel straight tubular ERW pipe or an ERW pipe is used for the hollow material, and the inside of the hollow material extends along its axial direction and has the terminal grip portion. A through hole that opens at the end face is provided, an inner surface shot peening is applied to a weld seam portion along an axial direction of an inner surface of the through hole, and a coating for rust prevention is applied to an inner surface of the through hole. It is characterized by having. The inner surface shot peening as referred to in this specification may be a sand blast using non-metal particles or a liquid honing using glass beads, in addition to a normal peening treatment using a steel shot.

[0008]

When the hollow torsion bar is used, as in the case of the solid torsion bar, a torsional load is applied to the effective portion via the terminal grip. The hollow torsion bar of the present invention is modified by the inner surface shot peening performed on the inner surface of the through hole, which is effective for improving the durability. For example, in the case of a hollow torsion bar made of an electric resistance welded pipe, the inner surface shot peening is performed near the weld seam, so that it is more durable than the conventional electric resistance welded pipe or the hollow torsion bar using the electric resistance welded pipe Is greatly improved. In addition, improvement of durability can be recognized by performing shot peening on the inner surface of the region including the end grip portion and the tapered portion. This hollow torsion bar can be 30% to 50% lighter than a solid torsion bar.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The hollow torsion bar 10 shown in FIG. 1 has an effective portion (main body portion) 11 having a length L1 to which a torsional load is applied at the time of use, and terminal grip portions 12 and 13 located at both ends of the effective portion 11. Tapered part 1 located between each end gripping part 12, 13 and effective part 11
4, 15 are provided. This hollow torsion bar 10
Is an integral member made of a steel hollow member 20. Hollow material 20
One example is a SAE4130 electro-drawing tube with an outer diameter of 34 m.
m, a thickness of 6 mm and a hardness of _HRC 50 ± 2 were used, but the outer diameter, thickness, hardness, etc. shall be appropriately selected as necessary. The hollow torsion bar 10 is used, for example, as a component of a suspension mechanism of an automobile.

[0010] Inside the hollow torsion bar 10, a through hole 21 is provided along the axial direction. Both ends of the through hole 21 are open at the end faces 22 and 23 of the end grips 12 and 13. Reference numerals 25 and 26 in the figure indicate through holes 21.
Are shown.

As shown in FIG. 2 representatively of one end of the hollow torsion bar 10, the outer diameter D2 of the terminal grip 12 is shown.
Is larger than the outer diameter D1 of the effective portion 11. Also, the inner diameter D4 of the terminal grip 12 is larger than the inner diameter D3 of the effective part 11. The thickness T2 of the terminal grip portion 12 is larger than the thickness T1 of the effective portion 11. Therefore, the thickness of the tapered portion 14 is changed from the thickness T1 on the effective portion 11 side to the thickness T1 on the end grip portion 12 side.
It gradually increases to 2. The other end of the hollow torsion bar 10 is also formed into a similar end shape.

The end grips 12 and 13 and the tapered portions 14 and 15 having the above-described shapes are formed by performing hot upset processing on both ends of the hollow member 20. In the hot upset process, the end of the hollow material 20 is heated,
A molding die is set at the end of the hollow member 20, and the hollow member 20 is set.
By applying a load to the end of the hollow member 20 from the axial direction, the end of the hollow member 20 is plastically deformed into a shape corresponding to the mold.

[0013] As shown in FIG.
Serrations 30 (only some of them are shown) are provided on the outer peripheral portions of 2 and 13. The serrations 30 may be formed by rolling. Instead of the serrations 30, splines may be provided by gear cutting such as cutting.

As shown in FIG. 6, upsetting may be performed so that the inner diameter D4 of the terminal grip 12 is smaller than the inner diameter D3 of the effective portion 11. In this case, after the terminal grip portion 12 is solidified by upset processing, a portion having an inner diameter D4 may be perforated by machining such as a drill. Further, as in the case of a terminal grip 35 shown in FIG.

The outer peripheral surface of the above-mentioned hollow torsion bar 10 is subjected to shot peening using a well-known shot peening apparatus. 4 is provided on the inner surface 31 of the through hole 21.
The inner shot peening is performed using the inner shot peening apparatus 40 as shown in FIG.

An inner surface shot peening apparatus 40 shown in FIG. 4 includes a shot projection nozzle 41 inserted into one open end 25 of the hollow member 20 and a shot reflection member provided at a position facing the nozzle 41. 42. A large number of shots are supplied to the nozzle 41 by a shot supply device (not shown), and the shots are ejected toward the shot reflecting member 42 together with the airflow.

The nozzle 41 is inserted into the open end 25 of the hollow member 20 so as to be substantially in close contact with the entire periphery thereof, so that the shot does not fly out of the open end 25. A shot collecting device (not shown) is connected to the other open end 26 of the hollow member 20 so that shots after projection are collected and sent to the shot supplying device again.

The shot reflecting member 42 is attached to the tip of a rod 45 inserted into the hollow member 20.
The rod 45 can be moved in the axial direction of the hollow member 20 by a drive mechanism (not shown).

The shot reflecting member 42 in the illustrated example has a conical reflecting surface 46. This reflection surface 46 is
The angle is set so that the shot projected from No. 1 can be hit toward the inner surface 31 of the through-hole 21 from a direction almost perpendicular to the shot. As shown by the arrow A in FIG. 4, the shot bounced off the reflection surface 46 is the inner surface 3 of the through hole 21.
By being hit at a high speed, a compressive residual stress is generated in the surface layer of the inner surface 31.

The above-described inner surface shot peening is desirably performed over the entire length of the inner surface 31 of the through hole 21. However, both end portions of the hollow member 20, that is, mainly the inner surfaces of the end grip portions 12, 13 and the tapered portions 14, 15, are preferably formed. There is a considerable effect even if it is implemented. In this case, at least the length H of the terminal grips 12 and 13 extends from the end faces 22 and 23 of the terminal grips 12 and 13 to the tapered portions 14 and 15.
The inner surface shot peening may be performed in a region ranging from about 1.5 times to 2.0 times of the above.

FIG. 5 shows the hollow torsion bar 10 of the present embodiment.
Is shown. In the material cutting step 50, by cutting the above-described electric-resistance-drawn tube,
A hollow member 20 having a predetermined length is obtained. In the end pipe expansion step 51,
Both ends of the hollow member 20 are expanded by plastic working.
After the end of the hollow member 20 is heated in the heating step 52, the end of the hollow member 20 is subjected to the upset step 53 so that the above-described thick pattern (the shape shown in FIG. 2 or FIG. 6) is obtained. Molding.

The serrated molding step 54 is performed on the hollow material 20 after the upset, so that the terminal grip 1
After serrations are formed on the outer peripheral portions of the hollow members 2 and 13 and a quenching step 55 and a tempering step 56 are performed, shot peening is performed on the outer surface of the hollow member 20 in an outer surface shot peening step 57. After that, the setting process 5
In step 8, by applying a setting load larger than the working load and performing the setting for a predetermined time, a permanent strain is given, and the set resistance is improved.

Next, an inner surface shot peening step 59
After performing the above-described inner surface shot peening on the inner surface of the hollow member 20, a low-temperature annealing step 60 is performed, and a coating film for rust prevention is applied to the outer and inner surfaces of the hollow member 20 in a coating step 61. This coating is performed over the entire length of the hollow member 20 to improve the corrosion resistance of the inner surface and the outer surface.

When an electric resistance welded tube is used for the hollow member 20, a welded seam portion 65 as shown schematically in FIG. This weld seam 6
The above-described inner surface shot peening may be intensively performed in a region including the region No. 5.

When the inner surface shot peening is performed in the vicinity of the weld seam portion 65, as shown in FIG.
The shot reflecting member 42 having a reflecting surface 66 that reflects light toward the light source 5 may be used. In this case, by projecting a shot while moving the shot reflecting member 42 in the axial direction of the hollow member 20, the welding seam portion 6
5 is subjected to inner shot peening over the entire length.

FIG. 10 shows the number of repetitions of breakage of the conventional hollow torsion bar (sample No. 1) and the hollow torsion bar (sample N) subjected to shot peening on the inner surface according to the present embodiment.
It is an experimental result of examining the number of repetitions of fracture of o.2 to No.4).
Sample No. 2 was a hollow torsion bar 10 using an electric resistance welded tube.
In this case, the inner surface is shot peened mainly over the entire length of the weld seam portion 65. In the case of this sample No. 2, the number of breakage repetitions is about twice that of the conventional hollow torsion bar.

Sample No. 3 in FIG. 10 is obtained by performing inner surface shot peening on the end of the hollow torsion bar, that is, the inner surface of the region including the end grips 12 and 13 and the tapered portions 14 and 15. . In this case, the terminal grips 12, 1 are connected to the end faces 22, 23 of the terminal grips 12, 13.
By performing inner surface shot peening to a range of about 1.5 times to 2.0 times the length H of No. 3, it was confirmed that the durability was significantly improved as compared with the conventional hollow torsion bar.

Sample No. 4 was obtained by performing shot peening on the entire inner surface of the hollow torsion bar, and it was confirmed that the durability was significantly improved as compared with the conventional hollow torsion bar.

[0029]

According to the present invention, the number of repetitions of breakage is increased about twice and the durability is greatly improved as compared with a hollow torsion bar for an experiment using a normal electric resistance welded tube. It becomes practically possible to use an ERW pipe or an ERW pipe that can be obtained at a lower cost as a spring member having severe stress conditions such as a torsion bar. Since the weld seam of the straight tubular ERW tube extends straight in the axial direction of the tube, the torsion bar can be twisted in any direction. ERW pipes can be manufactured with smoother inner surfaces than welded seams compared to seamless pipes, so there are fewer defects such as inner surface flaws, and shot peening is performed along the pipe axis.
Since the process is performed on the welded seam along the direction, the time required for shot peening can be shortened and the shot amount can be reduced, so that the productivity is high and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a hollow torsion bar showing a first embodiment of the present invention.

FIG. 2 is a sectional view of an end of the hollow torsion bar shown in FIG. 1;

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a cross-sectional view of a part of an apparatus for performing inner surface shot peening on a hollow material.

FIG. 5 is a view showing a manufacturing process of the hollow torsion bar shown in FIG. 1;

FIG. 6 is a sectional view of an end of a hollow torsion bar showing a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing another embodiment in which the terminal grip portion has a hexagonal shape.

FIG. 8 is a sectional view showing a welded seam portion of the electric resistance welded tube.

FIG. 9 is a cross-sectional view of a part of an apparatus for performing internal shot peening on a weld seam portion of an ERW pipe or an ERW pipe.

FIG. 10 is a view showing the durability of a conventional hollow torsion bar and a hollow torsion bar subjected to inner surface shot peening.

[Explanation of symbols]

10: hollow torsion bar, 11: effective part, 12, 13
... Terminal gripping parts, 14, 15 ... Tapered part, 20 ... Hollow material, 21 ... Through hole, 31 ... Inner surface, 40 ... Shot peening device, 41 ... Shot projection nozzle, 42 ... Shot reflecting member.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Koyama 3-10-10 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Within Japan Hakko Co., Ltd. (56) References JP-A-54-47839 (JP, A) JP-A-63 JP-A-312070 (JP, A) JP-A-53-5492 (JP, A) JP-A-3-79271 (JP, A) JP-A-50-39665 (JP, A) JP-A-49-90649 (JP, A) JP-A-47-35753 (JP, A) JP-A-59-2901 (JP, A) JP-A-64-111848 (JP, A) JP-A-63-222862 (JP, A) 90137 (JP, A) JP-A-3-249127 (JP, A) JP-A-63-139668 (JP, A) JP-A-62-107832 (JP, A) JP-A-61-88994 (JP, A) JP-A-62-246636 (JP, A) JP-A-58-188531 (JP, A) JP-A-63-17765 (JP, U) JP 58-50127 (JP, Y2) spring Technology Research Society "spring" second revised edition (Akira 45-1-15) Maruzen, P. 390-392

Claims (1)

(57) [Claims] An effective portion to which a torsional load is applied during use, a terminal grip located at an end of the effective portion and having a greater thickness than the effective portion, and a position between the effective portion and the terminal grip. A straight tubular hollow torsion bar made of a hollow material having a tapered portion, wherein a steel straight tubular electric resistance welded tube or an electric resistance drawn tube is used for the hollow material. Inside the material is provided a through-hole that opens in the axial direction and at the end face of the end grip portion, and the inner surface of the through-hole is subjected to inner shot peening at the weld seam portion along the axial direction. A hollow torsion bar, wherein a coating for rust prevention is applied to the inner surface of the through hole.