JPH04200925A - Method for correcting roundness of hollow part of metallic made material to be formed having circular hollow part - Google Patents

Abstract

PURPOSE:To correct the hollow part of material to be formed with high roundness by inserting the correcting member which has a coefficient of linear expansion smaller than the material to be corrected and whose diameter is somewhat smaller than the hollow part of the material to be formed, in the hollow part of the material to be formed, and cooling the both. CONSTITUTION:As a correcting member 2, an iron core of complete roundness whose coefficient of linear expansion is smaller than the extrusion material 1 to be formed for a motor case and whose diameter is formed somewhat smaller than the diameter of the hollow part 1a of the material 1 to be formed. The correcting member 2 is inserted and arranged in the hollow part 1a of the material 1 to be formed, and the both are cooled by immersing them in the liquid nitrogen, etc. By cooling, the larger shrinkage of the material 1 to be formed is generated compared with the correcting member 2, total of the hollow part 1a of the material 1 to be formed comes in close contact with the outer circumferential surface of the correcting member 2, the out-of- roundness of the shaped material 1 is corrected. Both the material 1 to be formed and the correcting member 2 are left in the air, after restored to the normal temperature, the correcting member 2 is pulled out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to molded materials made of metal such as aluminum having a circular hollow portion, such as molded materials for motor cases, molded materials for cylinders, various circular tubes, various circumferentially irregularly shaped tubes, etc. The present invention relates to a method for correcting the roundness of a hollow part.

Prior Art In a circular hollow part, for example, 0. When manufacturing hollow metal products that require a high roundness of 2 or less ((maximum diameter - minimum diameter)/2), such as aluminum motor cases, aluminum cylinders, etc., Generally, it is difficult to achieve high roundness by extrusion molding alone, so the roundness of the hollow part of the mold material is corrected after extrusion.

Conventionally, this correction has been sometimes performed by an internal cutting method in which the inner surface of the hollow part of the extruded material is cut, but since this cutting method is disadvantageous in terms of cost, multiple The mainstream method is to expand the tube by synchronously displacing outer circumferential arc-shaped tube expansion pieces radially outward within the hollow portion of the mold to expand the tube.

Problems to be Solved by the Invention However, as described above, the tube expansion method corrects the roundness of the hollow portion by displacing a plurality of tube expansion pieces in a divided configuration radially outward. Since the tube expands discontinuously in the circumferential direction with gaps between the pieces, there is a limit to the degree of roundness that can be corrected.

Further, there was also the problem that lines were likely to be formed on the inner surface of the hollow portion due to the gaps existing between the tube expansion pieces.

The present invention solves the above-mentioned conventional drawbacks, makes it possible to straighten a circular hollow part to a higher degree of roundness than before at a low cost, and also prevents lines from being formed on the inner surface of the hollow part after correction. It is an object of the present invention to provide a method for correcting the roundness of a hollow part of a metal mold material having a circular hollow part.

Means for Solving the Problems To achieve the above object, the present invention provides a metal material having a perfect circular cross section, which has a coefficient of linear expansion smaller than that of the metal shape material to be straightened, and whose diameter is slightly smaller than the circular hollow part of the shape material. Using a manufactured roundness correction member, = 3- With the correction member inserted into the circular hollow part of the mold material, both of them are cooled so that the entire circumferential direction of the inner peripheral surface of the hollow part of the mold material is aligned with the outer peripheral surface of the correction member. The gist of the present invention is a method for correcting the roundness of a hollow part of a metal mold material having a circular hollow part, which is characterized by correcting the roundness of the circular hollow part of the mold material by bringing it into close contact with the mold material.

Note that by performing a step of returning both of these members to room temperature after cooling, the straightening member can be pulled out.

Effect In the above method, the inner surface of the circular hollow part of the mold material is deformed along the circumferentially continuous outer circumferential surface of the roundness correction member due to the difference in heat shrinkage between the mold material and the straightening member. Roundness correction is performed.

Therefore, the circular hollow portion is corrected to a high degree of roundness, and the formation of streaks on the inner surface of the hollow portion does not occur.

Example Next, the present invention will be explained in detail.

The shape material to be straightened according to the method of this embodiment is made of aluminum with a diameter of 20 mm made of A606B as shown in FIG.
This is an extruded material (1) for a motor case with a thickness of about 0 mm.

The mold material (1) was manufactured by extrusion molding with the aim of meeting the design dimensions of the motor case to be manufactured.

On the other hand, the straightening member (2) has a coefficient of linear expansion of 11.0X which is smaller than 16.0XIO-6/°C, which is the coefficient of linear expansion of the mold material (1). 7
An iron core according to 5KD-61 with a linear expansion coefficient of X 10'/'C is used.

This correction member (2) is formed with a perfect circle in cross section,
Its diameter is the hollow part (1) of the motor case profile (1).
The diameter is slightly smaller than the diameter of a).

The method of this embodiment is carried out using the correction member (2) according to the procedure shown in FIG.

That is, as shown in (a) and (b) of the same figure, the correction member (2) is inserted into the hollow part (1a
).

Then, both are cooled in the arranged state. Various cooling methods can be considered, but both (1) and (2)
) is generally immersed in liquid nitrogen. Note that the cooling is performed to a temperature of -100 to -150°C for about 0 minutes, for example.

By cooling, the motor case mold material (]) becomes the straightening member (2).
), and as a result, as shown in Figure 1 (c), the hollow inner surface (1
b) The entire part comes into close contact with the outer peripheral surface of the roundness correction member (2), thereby correcting the roundness of the hollow part (1a).

After that, the correction member (2) is pulled out. For extraction, mold material (1
) and the straightening member (2) are generally left to stand and return to room temperature before performing the straightening. This allows for smooth extraction. Figure 1 (D) shows the condition returned to room temperature, and Figure 1 (E)
2 shows the state in which the correction member (2) is pulled out. The hollow part (1a) of the mold material (1) after being extracted is corrected to a high degree of roundness by having the outer circumferential surface corrected using the circumferentially continuous correction member (2) as described above. .

In addition, the cooling temperature, the material of the straightening member (2), the same member (
It goes without saying that there is a correlation between the diameters of 2), but these are the same as those of the hollow part (1) of type tA' (1).
The hollow part (
It is desirable to determine such that only the roundness of 1a) is corrected. That is, for example, if the linear expansion coefficient of the straightening member (2) is too small, its diameter is too large, and the cooling temperature is too low, the circularity of the hollow part (1a) of the molding member (1) will certainly be Although it is straightened, the mold material (1
This is because the diameter of the hollow portion (1a) of ) may be unintentionally enlarged from its initial diameter, resulting in various problems.

However, this consideration may not be necessary in cases where there is no particular inconvenience in causing diameter expansion, or in cases where correction is performed in anticipation of tube expansion.

Note that the method of the present invention is applicable to the motor case (1) as described above.
), as well as the cylinder mold +4' shown in Figure 2.
(4) A hollow profile with a rectangular outer circumference as shown in Figure 3 (
5) For straightening the circular hollow portion of various metal shapes having a circular hollow portion, including various circular pipes (6) as shown in Fig. 4, or semi-hollow shapes such as rodless cylinder shapes. Needless to say, it can be widely applied.

In addition, the shape material is not limited to aluminum or its alloy, and the coefficient of linear expansion of the straightening member (2) may be relatively small in relation to the shape material, and various materials other than iron may be used. Metal materials may be used.

Effects of the Invention As described above, the roundness correction method of the present invention uses a cross section formed with a coefficient of linear expansion smaller than that of the metal mold to be corrected and slightly smaller in diameter than the circular hollow part of the mold. Using a perfect circular metal roundness correction member, with the correction member inserted into the circular hollow part of the mold material, both are cooled and the entire circumferential direction of the inner peripheral surface of the hollow part of the mold material is adjusted to the outer periphery of the correction member. Since this method corrects the roundness of the circular hollow part of the mold material by bringing it into close contact with the surface, it is possible to correct the hollow part to a higher roundness than with the conventional tube expansion method. The inconvenience of streaks forming on the inner surface of the hollow portion does not occur. Therefore, the roundness of the hollow portion of a mold material for a motor case or a mold material for a cylinder, for example, which is particularly susceptible to streaks on the inner surface, can be properly corrected.

In addition, the roundness can be corrected in a highly follow-on manner without incurring the cost disadvantages of the cutting method.

[Brief explanation of the drawing]

FIG. 1 shows a method according to an embodiment of the present invention. FIG. The figure (c) is a cross-sectional view showing a state in which the mold material and the straightening member have contracted due to cooling and the roundness of the hollow part of the mold material has been corrected, and the figure (d) is a cross-sectional view showing the state in which the mold material has been returned to room temperature. The sectional view shown in FIG. FIG. 2 is a cross-sectional view of a cylinder mold, FIG. 3 is a cross-sectional view of a hollow mold with a rectangular outer circumference, and FIG. 4 is a cross-sectional view of a circular tube mold. (1) Extruded material for motor case (metal hollow material), (1a) Hollow portion, (2) Metal roundness correction member. Above (D) 4 Figure 2 (E) Figure 1

Claims (1)

[Scope of Claims] Using a metal roundness correction member having a linear expansion coefficient smaller than that of the metal shape material to be corrected and having a diameter slightly smaller than the circular hollow part of the shape material and having a perfect circle in cross section, With the straightening member inserted into the circular hollow part of the mold material, both of them are cooled so that the entire inner peripheral surface of the hollow part of the mold material is in close contact with the outer peripheral surface of the straightening member in the circumferential direction. A method for correcting the roundness of a hollow part in a metal mold material having a circular hollow part, the method comprising correcting the roundness.