JP2004052616A - Method of machining turbine blade of supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of machining a turbine blade of a supercharger for shortening a time for correcting a degree of unbalance and improving the yield of products by greatly reducing the degree of unbalance being unavoidably produced in a conventional machining method. <P>SOLUTION: A cylindrical boss portion 12 on the side of a rotor shaft is previously provided on a joint portion between the precisely cast turbine blade 2 and the rotor shaft 3. A front end portion 14 of the turbine blade 2 is machined into a cylindrical shape with an outer periphery face B of the boss portion as a machining criterion in the radial direction and then the boss portion on the side of the rotor shaft is finish-machined with an outer periphery face C of the front end portion as a machining criterion in the radial direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for processing a turbine blade of a supercharger.
[0002]
[Prior art]
FIG. 5 is an overall configuration diagram of a turbine rotor shaft in which a turbine blade and a rotor shaft are joined. In this figure, (A) is a completed turbine rotor shaft 1 and (B) is an explanatory diagram showing the turbine rotor shaft 1 separated into a turbine blade 2 and a rotor shaft 3 at a joint portion thereof. A compressor blade (not shown) is screwed to the right end of the turbine rotor shaft 1 shown in FIG. Such a turbine rotor shaft 1 rotates at a high speed of tens of thousands to hundreds of thousands of rpm especially in a small-sized one, so that its balance is extremely important. Therefore, the unbalance amount of the turbine rotor shaft 1 is measured by a dynamic balance test, and the unbalance is adjusted by cutting off portions A and B (two locations) indicated by oblique lines in the figure.
[0003]
FIG. 6 is a process chart of a conventional turbine rotor shaft, and FIG. 7 is a schematic view thereof. As shown in FIGS. 6 and 7, first, the joint of the precision-cast turbine blade 2 is machined, and the rotor shaft 3 is subjected to intermediate machining except for a finishing margin (A) and (B). Next, the turbine rotor shaft 1 is integrated by electron beam welding (C). Next, the rotor shaft portion is finished, the rotor shaft is hardened (nitriding or induction hardening), and the shaft is polished and the outer diameter of the turbine blade is ground (D). Finally, the amount of unbalance is measured by a dynamic balance test, and a part of the turbine blade is cut off to adjust the unbalance, whereby the turbine rotor shaft 1 is completed.
[0004]
[Problems to be solved by the invention]
FIGS. 8A and 8B are explanatory diagrams of a step of machining a joint portion of a precision casting of the turbine blade 2, wherein FIG. 8A shows a state before the processing and FIG. 8B shows a state after the processing. As shown in this drawing, a boss hole 2a is provided in advance at the joint of the precision casting, and in this processing step, the end face 2b of the joint is determined based on the joint side end face A and the outer diameter B of the turbine blade. And the inner surface 2c.
[0005]
However, there is a problem that the unbalance amount of the turbine blade 2 is large due to the conventional processing step. As a result, in the above-described imbalance adjustment in the final step, the imbalance amount is too large, and it takes a long time to correct, or a high rate of defective products cannot be corrected.
There are also the following problems.
(1) There is no unbalance measurement standard for the material alone.
(2) Unbalance cannot be measured at the processing reference portion.
(3) The blades become thin due to weight reduction or the like, and chucking is not possible.
[0006]
The present invention has been made to solve such a problem. That is, an object of the present invention is to significantly reduce the amount of unbalance inevitably generated by the conventional processing method, and it is possible to manage the balance during processing by providing an unbalance measurement reference to the material. Provided is a method of processing a turbine blade of a turbocharger, which can perform processing regardless of the shape and thickness of the blade, thereby shortening the time required to correct the imbalance amount and increasing the product yield. It is in.
[0007]
[Means for Solving the Problems]
Conventionally, the joining portion is cut using the outer diameter portion of the turbine blade as a processing reference. However, although the material of the turbine blade is a precision cast product, the blade part used as a processing standard has a complicated shape, is thin, and has a high cooling rate after casting, so that it is affected by shrinkage stress and deformed. large. Therefore, the accuracy (about ± 0.02 mm) considered necessary as a processing standard is not obtained (the actual value is about 0.2 mm). As a result, from the measurement results described below, it was found that the center of the joint processed using the outer diameter portion of the blade as the processing reference caused a deviation from the balance center of the entire turbine blade, which was a cause of unbalance of the entire turbine rotor shaft. It became clear.
[0008]
On the other hand, it is considered that the balance center of the turbine blade is located at the center where the ratio of mass to the surface area is larger than that of the blade and the cooling rate is slow. This is because the effect of the shrinkage stress is small in this portion, and it is relatively easy to maintain the accuracy. As a result, it became clear from the measurement results that the boss of the precision casting adjacent to the center portion almost coincided with the balance center of the entire turbine blade.
[0009]
The present application has been made based on the above-mentioned new findings. That is, according to the present invention, a cylindrical rotor shaft-side boss portion (12) is provided in advance at the joint of the turbine blade (2) of the precision casting with the rotor shaft (3), and the boss portion outer peripheral surface B is provided. The tip (14) of the turbine blade (2) is machined into a cylindrical shape with the machining reference in the radial direction, and then the rotor shaft side boss is finished with the tip outer peripheral surface C as the machining reference in the radial direction. A method for machining a turbine blade of a supercharger is provided.
[0010]
According to this method of the present invention, the deviation from the center of balance of the entire turbine blade is large, and the outer diameter portion of the turbine blade that is difficult to be gripped by a chuck or the like is not used as a radial machining reference, and the balance of the entire turbine blade is balanced. The two boss portions (the rotor shaft side and the tip portion) which are substantially coincident with the center can be sequentially used as the processing reference in the radial direction to finish the rotor shaft side boss portion (12).
Therefore, the rotor shaft side boss portion (12) close to the balance center of the precision casting can be machined by eliminating the unbalance inevitably generated by the conventional finishing process using the outer diameter portion of the blade.
[0011]
According to a preferred embodiment of the present invention, in processing the tip portion (14), a cylindrical end surface and a root portion are machined with the joint-side end surface A of the turbine blade as an axial machining reference.
In the finishing process, at least the end surface (2b) and the inner surface (2c) of the joint are processed using the outer peripheral surface C and the end surface or the root portion D of the tip portion (14) as a processing reference.
In addition, if the unbalance amount based on the front end of the material is within a certain amount, it is also possible to directly use the processing reference without performing the processing.
[0012]
According to this method, the end face (2b) and the inner face (2c) of the joining portion are machined with reference to the outer peripheral surface of the tip portion machined based on the rotor shaft side boss (12). (2b) and the inner surface (2c) can be formed concentrically close to the balance center of the precision casting, the thickness of the joint with the rotor shaft can be made uniform, and electron beam welding can be performed with higher precision. .
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram of a turbine rotor shaft according to the present invention, and FIG. 2 is a schematic diagram of FIG. As shown in FIG. 1, in the machining method of the present invention, a turbine blade is machined in three steps: precision casting S1a, cylindrical machining S1b at the tip, and finishing S1c at the boss.
[0014]
In the precision casting S1a of the turbine blade, as shown in FIG. 2 (A), a cylindrical rotor shaft side is formed beforehand on the joint of the turbine blade 2 of the precision casting with the rotor shaft 3 and on the rotation center of the turbine blade. A boss 12 is provided. The rotor shaft side boss portion 12 is provided with a cylindrical boss hole 2 a at a joint portion with the rotor shaft 3. Further, another boss portion 14 is provided in advance on the rotation center of the turbine blade 2 at the tip of the turbine blade 2 on the side opposite to the rotor shaft 3.
[0015]
The rotor shaft side boss portion 12 and its boss hole 2a are preferably made as high as possible in precision casting so that one end of the rotor shaft can be fitted with a minimum amount of machining. About 0.01 mm. The boss 14 on the distal end side is also preferably provided in advance in a high-precision cylindrical shape with the same accuracy.
[0016]
The boss 14 on the tip side may be formed in a hexagonal surface or a so-called chrysanthemum seat as in the conventional case. Otherwise, this precision casting S1a is the same as the conventional one.
[0017]
In the cylindrical processing S1b of the tip part, as shown in FIG. 2A, the tip part 14 of the turbine blade 2 is machined into a cylindrical shape using the rotor shaft side boss part 12 as a working reference B in the radial direction. In this processing, the cylindrical end face and the root are machined using the joint-side end face A of the turbine blade as the machining reference in the axial direction.
[0018]
In the finishing process S1c of the boss portion, as shown in FIG. 2B, the rotor shaft side boss portion 12 is finished using the outer peripheral surface of the tip portion 14 as a working reference C in the radial direction. In this processing, the end face of the tip portion 14 or the root D is used as a processing reference in the axial direction.
In this finishing process, at least the end surface 2b and the inner surface 2c of the joint are processed with reference to the outer peripheral surface C and the end surface or the root portion D of the tip portion 14. Further, the outer diameters of the boss hole 2a and the boss portion 12 are preferably finished in this step.
[0019]
FIG. 3 is a measurement result showing an unbalance amount during processing according to the present invention. In this figure, (A) shows the unbalance amount of the precision casting (material) obtained by the precision casting S1a, and (B) shows the unbalance after the cylindrical processing S1b at the tip (after the tip processing). Quantity. In each figure, the unbalance amount is indicated by the direction of the eccentricity (0 to 360 °) and the eccentricity (μm). Also, the numbers and black dots (●) in the figure are the actually measured values of different materials, and white circles (○) are the average values.
The imbalance amount of the precision casting (material) of (A) can be adjusted to some extent by modifying the casting mold.
[0020]
In FIG. 3A, the average unbalance amount is 23.72 μm (approximately 0.02 mm) in the direction of 34.86 °, and 15 points (No. 11 is a missing number) of the precision cast product (material) It can be seen that it is concentrated near the average position.
This indicates that the precision casting (raw material) of the turbine blade as a whole has an accuracy close to the accuracy (approximately ± 0.02 mm) considered necessary as a processing standard.
[0021]
However, the blade portion of the turbine blade has a complicated shape, is thin, and has a high cooling rate after casting. On the other hand, in the central portion of the turbine blade, the ratio of mass to the surface area is larger than that of the blade, and the cooling rate is slow. Therefore, the influence of shrinkage stress is small, and accuracy is relatively easily maintained. Therefore, it can be said that the boss portion of the precision casting adjacent to the center portion has higher accuracy than the average of the entire material, and substantially matches the balance center of the entire turbine blade.
[0022]
FIG. 3B shows the amount of unbalance after processing of the tip, and the average amount of unbalance is 17.51 μm (about 0.02 mm) in the direction of 58.57 °. From this, it can be seen that the 15 points (No. 11 is a missing number) after the processing of the tip are also concentrated near the average position of the precision casting (material) before the processing.
[0023]
From the comparison between (A) and (B) in FIG. 3, it can be seen that the direction of imbalance and the amount of eccentricity are very similar between the raw material (A) and the processed end portion (B). From this, it is understood that the cylindrical processing S1b at the tip is performed at least in a direction that does not increase the imbalance, and the processing reference B in the radial direction is appropriate.
[0024]
FIG. 4 is a measurement result showing the unbalance amount after the finish processing according to the present invention and the conventional example. In this figure, (A) shows the unbalance amount of the turbine blade 2 according to the method of the present invention in which the boss portion finishing process S1c is performed after the tip end cylindrical process S1b, and (B) is the conventional method. Is the amount of unbalance of the turbine blade 2 due to In each figure, the unbalance amount is indicated by the direction of the eccentricity (0 to 360 °) and the eccentricity (μm). Also, the numbers and black dots (●) in the figure are the actually measured values of different materials, and white circles (○) are the average values.
[0025]
In FIG. 4A, the average unbalance amount is 21.76 μm (about 0.02 mm) in the direction of 76.43 °, and seven processed products (turbine blades 2) concentrate near this average position. You can see that it is.
From this, the turbine blade of the present invention can maintain the unbalance tendency of the precision casting (material) as it is, and can obtain an accuracy close to the accuracy (about ± 0.02 mm) considered necessary as a processing standard. Understand.
[0026]
On the other hand, in the conventional example of FIG. 4B, the average amount of unbalance is 63.92 μm (about 0.06 mm) in the direction of 27.71 °, and the processed product (turbine blade 2) that the direction and the amount of eccentricity vary greatly.
This is due to processing based on the outer diameter of the turbine blade, which has a large amount of unbalance.As a result, the amount of unbalance is too large in the unbalance adjustment in the final process, and it takes a long time to correct it, or it can be corrected. It can be seen that the rate of defective products becomes higher without any change.
[0027]
According to the method of the present invention described above, the deviation is large with respect to the balance center of the entire turbine blade, and the outer diameter portion of the turbine blade that is difficult to be gripped by a chuck or the like is not used as a processing reference. The rotor shaft side boss portion 12 can be finish-processed by using two boss portions (the rotor shaft side and the tip portion) that are substantially coincident with each other in order as a processing reference.
Therefore, it is possible to eliminate the unbalance inevitably generated by the conventional finishing process based on the outer diameter portion of the blade, and to process the rotor shaft side boss portion 12 close to the balance center of the precision casting.
[0028]
In addition, since the end surface 2b and the inner surface 2c of the joining portion are machined based on the outer peripheral surface of the tip portion machined based on the rotor shaft side boss portion 12 having the boss hole 2a, the boss hole 2a is machined with the unmachined boss hole 2a. The end face 2b and the inner face 2c can be formed concentrically near the balance center of the precision casting, the thickness of the joint with the rotor shaft can be made uniform, and electron beam welding can be performed with higher precision.
Further, by finishing the outer diameters of the boss hole 2a and the boss portion 12 in this step, the entire rotor shaft side boss portion 12 can be formed concentrically close to the balance center of the precision cast product. The thickness of the joining portion with the metal can be made uniform, and electron beam welding can be performed with higher accuracy.
[0029]
Next, a method of processing a portion other than the turbine blade will be described.
In FIG. 1, in the processing step of the present invention, further, finishing processing S2 of the rotor shaft, hardening processing S3a of the rotor shaft, polishing S3b of the rotor shaft, electron beam welding S4, outer diameter grinding S5 of the turbine blade, and dynamic balance. It has each step of adjustment S5.
[0030]
The finishing process S2 of the rotor shaft is preferably performed by the rotor shaft alone to the final finish, omitting the intermediate processing. Further, in the subsequent rotor shaft hardening treatment S3a, necessary nitriding treatment or induction hardening is performed, and the surface is polished in the rotor shaft polishing S3b.
[0031]
In the electron beam welding S4, one end 3a of the rotor shaft 3 finished in advance by the finishing process S2 of the rotor shaft is fitted into the boss hole 2a machined in the finishing process S1c of the turbine blade, and the joined portion is subjected to electron beam welding.
[0032]
In the outer diameter grinding S5 of the turbine blade, the turbine blade 2 is processed based on the outer diameter C and the end face E of the rotor shaft 3 finished in the finishing process S2 of the rotor shaft. Alternatively, machining is performed using the center hole D of the rotor shaft 3 and the center hole 2d of the blade as a machining reference.
[0033]
Finally, the amount of unbalance is measured by dynamic balance adjustment S6, and a part of the turbine blade is cut to adjust the unbalance, thereby completing the turbine rotor shaft 1.
[0034]
It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the processing of the turbine rotor shaft of the supercharger, particularly the joining of the turbine blade 2 and the rotor shaft 3 has been described. However, the method of the present invention can be applied to the field of vacuum components, aerospace components, and the like. The same applies to a case where a plurality of members are coaxially welded to each other.
[0035]
【The invention's effect】
As described above, the method of processing a turbine blade of a turbocharger according to the present invention can significantly reduce the amount of unbalance that has been inevitably generated by a conventional processing method. By providing, it is possible to control the balance at the time of processing, it is possible to process regardless of the shape and thickness of the blade, thereby shortening the time required to correct the unbalance amount, it is possible to increase the product yield, And various other excellent effects.
[Brief description of the drawings]
FIG. 1 is a process diagram of a turbine rotor shaft according to the present invention.
FIG. 2 is a schematic diagram of FIG.
FIG. 3 is a measurement result showing an unbalance amount during processing according to the present invention.
FIG. 4 is a measurement result showing an unbalance amount after finish working according to the present invention and a conventional example.
FIG. 5 is an overall configuration diagram of a turbine rotor shaft in which a turbine blade and a rotor shaft are joined.
FIG. 6 is a process chart of a conventional turbine rotor shaft.
FIG. 7 is a schematic view of FIG. 6;
[Explanation of symbols]
1 turbine rotor shaft, 2 turbine blades, 2a boss hole, 2b end face,
2c joint inner surface, 2d center hole, 3 rotor shaft, 3a joint end,
4 welding jigs, 5 balls, 6 heads, 7 welding beads,
12 Boss on rotor shaft side, 14 Tip

Claims (3)

A cylindrical rotor shaft-side boss portion (12) is provided in advance at the joint of the turbine blade (2) of the precision casting with the rotor shaft (3), and the outer peripheral surface B of the boss portion is used as a working reference in the radial direction. A turbocharger characterized in that the tip (14) of the turbine blade (2) is machined into a cylindrical shape, and then the rotor shaft side boss is finished with the tip outer peripheral surface C being used as a machining reference in the radial direction. Method of processing turbine blades. 2. The turbocharger according to claim 1, wherein, in the processing of the tip portion, a cylindrical end surface and a root portion are processed with the joint-side end surface A of the turbine blade as a processing reference in the axial direction. 3. Method of processing turbine blades. 3. The finishing process according to claim 2, wherein at least the end surface (2b) and the inner surface (2c) of the joint are processed with reference to the outer peripheral surface C and the end surface or the root portion D of the tip portion (14). 3. The method for processing a turbine blade of a turbocharger according to claim 1.

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