JPH05329513A - Manufacture of steel tube for rack bar - Google Patents

Abstract

(57) [Summary] [Purpose] To manufacture steel pipes for rack bars at high yield and at low cost. [Structure] In drawing and rolling a steel pipe by a three-roll type stretch reducer, only the final stand of the stretch reducer is a two-roll type, and a roll in which a part of the caliber is flatly raised is used for this two-roll type roll. Method for manufacturing a steel pipe for a rack bar, in which a steel pipe is rolled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a steel pipe for a rack bar incorporated in a rack and pinion type steering device of an automobile.

[0002]

2. Description of the Related Art A steel pipe for a rack bar incorporated in a rack and pinion type steering device of an automobile is provided with a rack portion 22 having a certain length in a part of a steel pipe 21 as shown in a perspective view of FIG. It is a thing.

As a conventional method for manufacturing the above-mentioned rack bar steel pipe 21, there is the following method. (1) As disclosed in JP-A-59-209421, a method of cold-pressing a rack forming portion of a steel pipe to form a flat portion, and then forming a rack on this flat portion. (2) A method of forming a rack portion by carving out from a thick steel pipe. (3) A method in which a stretch reducer (three-roll method) described in Japanese Patent Application No. 4-107472 is used as a final stand roll having a flat caliber roll.

[0004]

However, the above-mentioned conventional method for manufacturing a steel pipe for a rack bar has the following problems. (1) Manufacturing method based on Japanese Patent Application Laid-Open No. 59-209421 The manufacturing cost is high in addition to the labor required. (2) Manufacturing method of cutting from thick-walled steel pipe The weight of the product becomes heavy.

(3) Method described in Japanese Patent Application No. 4-107472 As shown in FIG. 3 (a), a roll diameter of a roll 23a in which a part of a caliber is raised to form a flat surface portion for a rack on a steel pipe. Is not the same as the diameters of the other rolls 23b and 23c, the rack bar steel pipe 21 having the flat portion 21a as shown in FIG. 3B cannot be obtained. Then, in the long steel pipe 24 shown in FIG. 4A, a cross-section 24a in which a circular part is cut away as shown in FIG. 4B which is a view taken along the line AA of FIG. 4 (a), which is a view taken along the line BB in FIG. 4 (c), is alternately formed with a perfect circular cross section (24b) as shown in FIG. If the rack length of the rack of the bar steel pipe 21 l ₁ and a circular portion and a length l ₂ will be uniquely determined, since the length of the total of both L also becomes constant, in some cases The circular cross section is cut off to some extent for use, and the yield is reduced.

The present invention has been made in order to solve the above-mentioned problems of the prior art. Since it does not take time and effort, the manufacturing cost is low, the product weight is light, and the yield does not decrease. It is an object of the present invention to provide a method for manufacturing a steel pipe for a rack bar.

[0007]

A method for manufacturing a steel pipe for a rack bar according to the present invention is such that, in the drawing and rolling of a steel pipe by a 3-roll type stretch reducer, only the final stand of the stretch reducer is a 2-roll type, and The steel pipe is rolled using a roll of a two-roll system in which a part of the caliber is flatly raised.

[0008]

In the method of manufacturing a steel pipe for a rack bar according to the present invention, only the final stand of the three roll type stretch reducer is of the two roll type, and part of the caliber is flatly raised to the two roll type roll. In this way, when the steel pipe is squeezed and rolled, the long steel pipe that came out of the final stand of the stretch reducer has a notch having a circular cross section and a straight part for forming a rack in a large portion that is mostly circular. The cross section and the cross section are formed alternately. Then, a plurality of rack bar steel pipes can be obtained by cutting this long steel pipe into a continuous body of adjacent circular cross-sections and cutout cross-sections as one unit.

When it is necessary to manufacture steel pipes for rack bars, which have the same length of the notched cross-sections that form the rack of the steel pipe for rack bars but have different circular cross-sections, part of the caliber is flattened. By appropriately changing the roll diameter of the raised roll, the target steel pipe for rack bar can be obtained, so that unnecessary parts are not cut off and the yield does not decrease.

[0010]

EXAMPLE A method for manufacturing a rack bar steel pipe according to an example of the present invention will be described with reference to FIG. In the method for manufacturing a steel pipe for a rack bar according to one embodiment of the present invention, as shown in the perspective view of FIG. 1 (a), only the final stand 2 of the stretch reducer 1 is of the two roll type. And FIG.
As shown in the front view of the roll in (b), a flatly raised portion 3b is formed on a part of the semicircular caliber 3a of the upper roll 3. Then, a steel pipe is passed between the upper roll 3 and the lower roll 4 composed of only the ordinary circular caliber 4a, and a circular notch cross section as shown in the transverse sectional view of FIG. Steel bar for rack bar 21
To roll.

The diameter D ₂ of the upper roll 3 shown in FIG.
The length l ₁ of the rack portion and the length l _{2 of the} circular portion shown in FIG.
And the diameter D ₀ of the semicircular caliber 3a (that is, the outer diameter of the steel pipe to be rolled), it is obtained as follows. Assuming that the roll diameter at the caliber bottom is D _2n , the roll diameter D ₂ and the caliber diameter D ₀ have the relationship of the equation (1). D ₂ = D _2n + D ₀ (1) Further, l ₁ , l ₂ and D _2n have the relationship of the equation (2). l ₁ + l ₂ = πD _2n (2) From equations (1) and (2), D ₂ can be represented by equation (3). D ₂ = {(l ₁ + l ₂ ) / π} + D ₀ ………… (3)

That is, a roll for rolling the flat surface for rack formation of a steel pipe for rack bar {upper roll in FIG. 1 (b)}
The diameter is determined from the required length l _{1 of} the flat portion for rack formation of the steel pipe for rack bar, the length l ₂ of the circular cross-section portion and the outer diameter D _{0 of the} steel pipe to be rolled.

As described above, if the roll diameter of the roll for rolling the rack forming flat portion of the rack bar steel pipe is changed, the rack bar steel pipes of various lengths (L) are continuously formed on the long steel pipe. However, it is not necessary to change the roll diameter on the side on which the flat surface for rack formation is not rolled. Then, the roll diameters of the upper and lower rolls may be different, and the peripheral speed of the rolls may be different, causing the steel pipe to slip. However, as shown in the drive mechanism of the roll, the roll diameter does not fluctuate. The lower roll 4 may be driven by the drive shaft 5, and the driving force may be transmitted to the upper roll via the pinion 6 having a diameter of d ₁ and the gear 7 having a diameter of d ₂ . By doing so, by setting the diameters d ₁ and d _{2 of} the pinion 6 and the gear 7 as shown in formula (4), the peripheral speeds of the upper and lower rolls can be made the same, and slippage will not occur. Absent. D ₁ × d ₁ = D ₂ × d ₂ ………… (4)

Example 1 A steel pipe having an outer diameter of 30 mm, a flat portion having a length of 180 mm, an upper roll diameter (flat portion rolling) 300 mm, and a lower roll diameter 300
It was rolled in mm. Overall length of the obtained steel pipe for rack bar = 850 mm Pinion diameter: Gear = 1: 1

Example 2 A steel pipe having an outer diameter of 30 mm, a flat portion having a length of 180 mm, an upper roll diameter (flat portion rolling) 200 mm, and a lower roll diameter 300
It was rolled in mm. The total length of the obtained steel pipe for rack bar = 534 mm Pinion diameter: Gear = 2: 3

[0016]

According to the present invention, steel pipes for rack bars having different lengths can be manufactured with good yield and at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory view of a method for manufacturing a rack bar steel pipe according to an embodiment of the present invention, in which (a) is a perspective view showing an installation location of a 2-roll stand, (b) is a front view of a roll, and (c) is ) Is a cross-sectional view of the roll.

FIG. 2 is a perspective view of a steel pipe for a rack bar.

FIG. 3 is an explanatory view of a conventional method for manufacturing a steel pipe for a rack bar, (a) is a perspective view showing a configuration of a three-roll stand,
(B) is a cross-sectional view of the roll.

FIG. 4 is an explanatory view showing a state where a rack bar steel pipe is formed on a long steel pipe, (a) is a longitudinal sectional view of the long steel pipe,
(B) is a view of the A-A arrow of (a), (c) is a B- of (a).
FIG.

[Explanation of symbols]

 1 Stretch reducer 2 Final stand 3 Upper roll 4 Lower roll 5 Drive shaft 6 Pinion 7 Gear

Claims (1)

[Claims] 1. In the drawing and rolling of a steel pipe by a three-roll type stretch reducer, only the final stand of the stretch reducer is a two-roll type, and a roll in which a part of the caliber is flatly raised is added to the two-roll type roll. A method for producing a steel pipe for a rack bar, which comprises rolling the steel pipe using the steel pipe.