JPH01210182A - Press-in joining method for cast parts - Google Patents

Abstract

PURPOSE:To facilitate joining cast iron parts which are hardly welded by providing a periodical uneven shape as cast on the fitting surface of one part at least to subject these to fit-in joining at the time of subjecting two parts to fit-in joining. CONSTITUTION:The periodical uneven shape is provided on the black surface of the fitting surface of one part at least. At the time of pressing-in, even if a projection part is easily sheared or crushed and dimensional accuracy of the black surface is low slightly, stable joining strength is obtained. It is easy for manufacturing a casting model to cast a thread shape of a triangular crest as the periodical uneven shape. The external surface to be fitted is machined and a screw thread with the prescribed height is cast on the internal surface to be fitted which are subjected to fit-in joining. In addition, the fitting surface between both is made to black as cast and the cast screw thread with the prescribed height on the internal surface is subjected to press-in joining thereto. By this method, variance on both pressing-in load and torsional strength is reduced and stable joining strength is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to press-fit joining of two parts, and particularly to a method of press-fit joining of cast parts.

[Conventional technology and problems]

Normally, when two parts are press-fitted together, a method is generally used in which both fitting surfaces are machined with an appropriate interference, and then the two parts are press-fitted together.

Although this method has excellent accuracy and is widely adopted, it increases the number of man-hours for each machining process, which is a major negative factor in terms of cost.

Therefore, it is conceivable to press-fit the mating surfaces of one or both of these joining parts with the black skin surface, but in this case, the variation in the press-in force will become large due to the variation in the dimensions of the black skin surface. As a result, the desired bonding strength cannot be stably obtained, and in fact it is rarely used.

In particular, cast iron materials that are widely used as cast parts, such as spheroidal graphite cast iron, have insufficient welding strength, so they have to rely on a joining method that involves some kind of mechanical processing, and their uses are limited.

The present invention was made in order to eliminate the drawbacks of the prior art described above, and it significantly reduces the number of machining steps, and
The object of the present invention is to provide a press-fit joining method for cast parts that can obtain stable joining strength.

[Means for solving problems]

The press-fit joining method of cast parts of the present invention is characterized in that when two parts are press-fitted together, a periodic uneven shape is formed by casting on the fitting surface of at least one of the parts, and the press-fit joining is performed. .

〔Example〕

Embodiments of the present invention will be described in more detail based on FIGS. 1 to 7.

Normally, when press-fitting two parts together, in order to obtain stable joint strength, both fitting surfaces are machined with an appropriate degree of precision, with an appropriate tightening allowance as shown in Figure 1. . This requires considerable machining costs.

Next, in the case of Fig. 2, where this is press-fitted with black leather, the dimensional accuracy of the casting material is, for example, about 100 mm in diameter, and even high precision is 0.2 to 0.5 mm, and usually 0.5 to 0.5 mm. 1
．． It is quite large at 0 mm, and stable strength cannot be obtained.

Therefore, in the present invention, by molding a periodic uneven shape on the fitting surface of at least one of the parts, sufficiently stable joint strength can be obtained with a certain degree of surface accuracy.

The advantage of the present invention compared to conventional press-fit joining using a black surface is that in conventional press-fit joining using a black surface, the entire fitting surface is affected by dimensional accuracy, resulting in large variations in press-in force. As a result, stable bonding strength cannot be obtained.In contrast, in the present invention, the black surface of the mating surface of at least one of the parts has a periodic uneven shape, so that the protrusions are easily sheared or crushed during press-fitting. Therefore, stable bonding strength can be obtained even if the dimensional accuracy of the black surface is somewhat low.

Various types of periodic uneven shapes can be considered, but in general, it is convenient to create a threaded shape of a triangular ridge in order to produce a casting model.

The present invention will be specifically explained in detail below.

Table 1 shows the results obtained in order to clarify the effects of the present invention.
This shows the experimental conditions for each species. The details of each experimental condition are shown in Figures 3 to 6.6 Table 1 Figure 3 shows an example of the present invention (A), in which the male fitting surface is machined and the female fitting surface is machined. This is an example in which a screw thread with a height of 1 mm is spun and press-fitted.

Figure 4 also shows an embodiment of the present invention (B).
Both mating surfaces are made of as-cast black skin, and the female surface is made of the present invention (
This is an example in which a flanged screw thread with a height of 1 mm was press-fitted as in A).

FIG. 5 shows a conventional example (1), which is the most common example in which both fitting surfaces are machined and press-fitted.

FIG. 6 shows a conventional example (2) in which the male surface is machined and the female surface is made of as-cast black skin and press-fitted.

However, this example has large variations in bonding strength and is practically not used.

Five test pieces were prepared for each of the above four joining methods, and the average value and standard deviation value of the variation were examined for the press-fit load and the torsional strength after press-fit.6 The results are shown in Table 2.

Table 2 From Table 2, the present invention (A) and (B) have significantly smaller variations in press-fit load and torsion strength than the conventional example (2) machined surface-black skin surface joint, resulting in stable joints. It can be seen that strength can be obtained. Also, a conventional example (1) which is commonly used
) The variation in press-fit load and torsion strength is slightly larger than that of the conventional example (1
It can be seen that stable bonding strength close to ) can be obtained.

Incidentally, as the periodic uneven shape, in the present invention (A) and (B), a screw-like uneven shape is used on the cylindrical surface, but the invention is not limited to this. The same effect can be obtained even if it is applied in any direction.

〔Effect of the invention〕

As described above, the method for press-fitting cast parts of the present invention is as follows. Conventionally, when joining cast parts, both parts are machined and press-fitted, or the flange surfaces are machined and bolted. However, according to the present invention, it is now possible to press-fit one or both of the two surfaces with the black skin surface, thereby making it possible to significantly reduce the number of machining steps. Therefore, the present invention facilitates the joining of cast iron parts, which are particularly difficult to weld, and dramatically expands the field of application thereof.

[Brief explanation of the drawing]

1-7 are cross-sectional views of the mating parts. Figure 1, Figure 2, Figure 3, = φ72±0.05 (Saijin HA machining) D2=ψ
70.7 ± 0.5 (high 1 m 乍i, the highest rank, L 9th time) 4th
Figure 5 Figure 6 D7” ψ72 soil 0.05 (Manyu λ (processing) Da = ψ7
1.3±065 (view pL)

Claims (1)

[Claims] 1. A method for press-fitting cast parts, characterized in that when two parts are press-fitted together, a periodic uneven shape is formed by casting on the fitting surface of at least one of the parts.