JPS6029840B2 - Impeller manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method for manufacturing impellers used in centrifugal compressors, radial turbines, and the like.

PRIOR ART This type of impeller is generally formed by integrally fixing the blades 2 to a shroud, as shown in FIG.
There are various types, ranging from those that are oriented linearly along the axis of rotation of the shroud to those that are oriented curved in the direction of rotation or the opposite direction.

Also, the inlet end (front green) 2A and outlet end (trailing edge) of the blade 2
In 2B, in order to obtain the required inflow and outflow angles, the shroud line at that part is bent more strongly,
Some are formed into so-called inducers and exducers. Here, the shroud line means a connecting line between the blade 2 and the shroud 1. In general, methods for manufacturing an impeller in which the shroud and blades are integrally formed include a method of carving out the shroud 1 and blades 2 from a block material, and a method of joining the blades 2 manufactured separately to the shroud 1. Methods of forging or casting are known.

Among these methods, in the method of manufacturing an impeller by casting, it is often impossible to manufacture the impeller by die-casting using a split mold because of the bendable shape of the blades.

Here, curvature generally refers to the three-dimensional bending of the blade.
This includes bending of the vane base (shroud line bending) in the shroud plane with respect to the direction of rotation (including both in-rotation and counter-rotation directions). In general, the blades can be considered to be formed on the shroud surface as a continuous part of minute width that stands upright in the radial direction with respect to the axis of rotation, so the bending of the blade base with respect to the rotational direction changes the upright direction of the blade, and as a result, As such, the feather will be married as a whole. These tears give the blade a three-dimensional curved shape. In the following description, the bending in the direction of rotation with respect to the shroud surface will be referred to as "bending", and the three-dimensional bending due to the engagement of the blades will be referred to as "harp bending". In cases where impellers cannot be manufactured by die casting, plaster molds, sand molds, lost wax molds, etc. must be used in place of metal molds.

This is not only because there is no die-cutting bolt or no mold, but also because it is generally known that bending a cast product is undesirable in terms of strength. This is because the curved shape of the blade had to be obtained at the casting stage to achieve the completed shape. Casting using these molds has very poor workability and productivity compared to die casting, resulting in high costs, and is also very disadvantageous because the dimensional accuracy and surface area of the product are also poor. OBJECTS OF THE INVENTION As described above, an object of the present invention is to provide a method for manufacturing an impeller having a shape that is terticast, that is, a shape that cannot be pressure cast, using pressure casting.

In particular, the present invention provides a manufacturing method that allows correction of curvature of the shroud line after pressure casting. Structure of the Invention The present invention is a manufacturing method that has become possible through the development of an aluminum alloy that maintains its strength even when subjected to mechanical processing such as bending after casting. Impellers that cannot be pressure cast with a mold due to their curves are first pressure cast into a shape that can be pressure cast close to the finished shape, and then mechanical processing such as bending is performed on this to make the impeller into the finished shape. The main focus is on finishing.

More specifically, a built-up part is integrally formed on one side of the blade base where the shroud line is to be corrected and pressure cast, a cut is formed on the opposite side of the built-up part, and the built-up part and the cut are connected. The part in between is raised in the height direction of the blade to form a blade base that can be displaced in the direction of the built-up part by the corresponding part, thereby completing the required shroud line, and then bending the blade to form the blade base. It is characterized by being molded into a shape.

As mentioned above, it has been difficult to perform such machining after pressure casting with commonly known aluminum alloy materials, but AI-Si-
Fe-Mg-Mn alloy (disclosed in Tokokukan Sho 51-86011 and commercially available under the trademark "Dx30 alloy"), to which 0.5 to 1.5% by weight of copper was added. N-Sj-Cu-Mg-Mn alloy (commercially available under the trademarks "Dx31 alloy" and "Dx31 alloy")
, and N-Mg-Zn alloys (Tokukan Sho 45-3280
It has been confirmed that the material (disclosed in Publication No. 8 and commercially available under the trademark "Dx2A alloy") can be sufficiently heat treated and machined, and that the manufacturing method of the present invention can be realized by using this material. It was. DESCRIPTION OF EMBODIMENTS The manufacturing method of the present invention will be explained below with reference to FIGS. 2 to 6.

Fig. 2 illustrates the features of the manufacturing method of the present invention, and if it is desired to correct the juraud line obtained by die casting, the blade 2 in the relevant range during die casting can be modified as shown in Fig. 2A. A built-up portion 10 of a predetermined size is formed on one side of the base.

Further, as shown in FIG. 1B, a notch 11 is formed on the opposite side of the built-up portion 10. This cut 11 can be formed at the same time as the built-up part 10 at the die-casting stage, but it can also be formed after die-casting. This cut 11 is formed so as to leave a required thickness of the blade 2 along the surface 10A of the built-up portion 10. Although the notch 11 is shown as an acute angle in the drawing, it can be made into a smooth concave shape. Thereafter, the blade 2 is raised in the height direction as shown in FIG. This occurrence means that the portion between the surface 10A of the built-up portion 10 and the notch 11 will become the new base of the blade 2. Therefore, the blade 2 can be raised by pulling it in the height direction, or it can be raised by generating the tensile force when bending the blade 2 (not shown). As a result, the position of the base of the portion of the blade 2 is displaced by a distance corresponding to the cutting depth S in the direction of the built-up portion 10 (in the direction of rotation or in the opposite direction). Also, depth of cut 11
By making the oblique portion formed in the thickness of the blade 2 into a substantially upright shape, the height of the blade increases. That is, feather 2
When the blade is pulled in the height direction, the blade is deformed from the state shown by the solid line in Fig. 3 to the state shown by the dashed line, and this part is displaced in the circumferential direction (towards the built-up part) along the shroud. Moreover, the height increases. Therefore, this corrects the bending of the shroud line of the blade 2 and simultaneously increases the height of the blade. Examples of impellers based on the above basics will be described with reference to FIGS. 4 to 6.

Although only one blade 2 in the shroud is shown and described in these drawings, the same applies to other blades (not shown).

In addition, A, B, and C in each figure correspond to each other, and A indicates the state of the intermediate product after die casting, C indicates the state of the finished wing, and B indicates the state of the wing at an intermediate stage. ing. In this example, the bending of the shroud line near inducer 2A and exducer 2B is strong in the completed shape, and
In the vicinity, the shroud surface is nearly parallel to the rotational axis, so the curvature of the blade 2 becomes noticeable. Such an impeller is first die-cast to a die-castable shape as shown in each figure A.

In other words, when die-casting the finished product in the shape of a finished product, the mold cannot be separated (mold-cutting), which makes die-casting practically impossible. It is first die-cast. At this stage, only the part of the blade 2 near the exducer 2B is formed into the required curved state, and the remaining part of the blade is formed parallel to the rotational axis direction of the impeller in order to enable release of the die-cast mold. It is made into an elongated shape. Also, the base of the remaining blade portion is formed as close as possible to the shroud line in the finished shape. However, if the shroud line near inducer 2A cannot be die-cast with the desired bend,
According to the features of the present invention, the build-up portion 10 as described above is integrally formed on the side of the blade in the direction of displacement, and a notch 11 is formed on the other side of the blade base near the inducer 2A, which cannot be die-cast into a desired curved shape. It will be done.

It is possible to die-cast such a built-up part. On the other hand, if the notches 11 can be formed at the same time by die-casting, they are processed at the time of die-casting, and if they cannot be formed at the same time by die-casting, they are processed later. This portion of the blade is then pulled in the direction of blade height as shown by the arrow in Figure 6B.

Thereby, as described above, the base of the blade 2 near the inducer 2A is corrected so as to follow the predetermined shroud line. At this time, for example, a tensioning tongue (not shown) may be integrally formed with the blade in advance, and the tongue may be removed after the blade is pulled up. By this raising, the height b of the blade near the inducer 2A can be made higher than the height b' in the central portion as desired, as shown in FIG. 6B.
In this way, a shape in which the height b of the front green of the inducer 2A is higher than the height of the central part cannot be formed by die casting in the previous stage, and this is also one of the reasons why impellers cannot be die cast as finished products. But there was. Thereafter, the blade portion of the inducer 2A is bent to obtain the desired inflow angle to form the required curved shape shown in each figure C. Here, the tension for raising and the bending process have been described as separate processes, but it is also possible to perform both processes simultaneously in the same process by generating the required tensile force through the bending process.

Through the above steps, an impeller having a desired shape is manufactured.

Needless to say, correction of the bending of the shroud line and correction of the curvature of the blade can be carried out at any point on the blade, and the built-up portion 10 and the notch 11 can be formed to correct the bending of the shroud line. Good. It is also desirable to perform heat treatment as necessary during bending. For example, solution treatment (480-5300C), quenching followed by temperature bending, and then aging effect (1
40 to 20,000), it is possible to facilitate the bending process and increase the strength of the product. As explained above, in the method of the present invention, a built-up part and a notch are formed in advance, and the blade is raised so that the built-up part becomes the base of the blade, thereby correcting the shroud line and adjusting the height of the blade. The blades are made taller and the curvature of the blades is finished by bending, so the following effects can be obtained. Effects ■ Impellers that cannot be pressure cast as a finished shape can be easily manufactured using a method that employs pressure casting.

■ Compared to conventional manufacturing methods that use plaster molds, it is possible to create products with a more delicate and healthy internal structure.

■ The strength is higher than that of conventional cast products, and it is possible to manufacture products with extremely good weight balance, which is important for impellers that rotate at high speed.

(2) Since tensile and bending processes are used as processing after pressure casting, products can be manufactured easily and inexpensively, and with high dimensional accuracy, compared to other mechanical processes such as press forming.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of an impeller manufactured according to the present invention. FIG. 2 is a step-by-step explanatory diagram illustrating the features of the manufacturing method of the present invention. FIG. 3 is a perspective view showing changes in shape according to the stages shown in FIG. FIG. 4 is a perspective explanatory view showing a step of modifying the blade shape of an impeller according to an embodiment of the manufacturing method of the present invention. Fifth
The figures are step-by-step explanatory diagrams of the blades seen from the top surface corresponding to FIG. 4, respectively. FIG. 6 is a cross-sectional view corresponding to FIG. 4. 1...Shroud, 2...Blade, 2A...
・Inducer part, 2B... Exducer part, 10... Overlay part, 11... Cutting depth. Figure 1 Figure 3 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. A method for manufacturing an impeller in which a plurality of blades are integrally formed in a shroud, which method includes integrally forming a built-up part on one side of a blade base whose shroud line is to be corrected. Die-cast,
A notch is formed on the opposite side of the built-up part, and a part between the built-up part and the notch is raised in the height direction of the blade to form a blade base that is displaced in the direction toward the built-up part by the corresponding part. This completes the required shroud line,
A method for manufacturing an impeller, which comprises bending blades and forming them into a desired shape. 2. The impeller manufacturing method according to claim 1, wherein the notch is formed simultaneously with the overlay during the pressure casting step of the intermediate product.