JP3916146B2 - Machining method of turbocharger turbine blade - Google Patents

Description

[0001]
BACKGROUND 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 obtained by joining turbine blades and a rotor shaft. In this figure, (A) is a completed turbine rotor shaft 1, and (B) is an explanatory view showing the turbine rotor shaft 1 separated into a turbine blade 2 and a rotor shaft 3 at the joint portion. A compressor blade (not shown) is screwed to the right end of the turbine rotor shaft 1 in FIG. Such a turbine rotor shaft 1 is particularly small, and rotates at a high speed of several tens of thousands to several hundred thousand rpm. Therefore, the balance is extremely important. Therefore, the turbine rotor shaft 1 measures the unbalance amount by a dynamic balance test, and adjusts the unbalance by cutting the A and B portions (two places) indicated by hatching in the figure.
[0003]
FIG. 6 is a process diagram of a conventional turbine rotor shaft, and FIG. 7 is a schematic diagram thereof. As shown in FIGS. 6 and 7, first, the precision casting portion of the turbine blade 2 is machined, and the rotor shaft 3 is subjected to intermediate machining leaving a finishing allowance (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 ground and the outer diameter of the turbine blade is ground (D). Finally, an unbalance amount is measured by a dynamic balance test, and a turbine rotor shaft 1 is completed by cutting a part of the turbine blade and adjusting the unbalance.
[0004]
[Problems to be solved by the invention]
FIG. 8 is an explanatory diagram of a process of machining a joint portion of a precision casting product of the turbine blade 2, (A) shows before processing, and (B) shows after processing. As shown in this figure, a boss hole 2a is provided in advance in the joint portion of the precision casting product. In this processing step, the end surface 2b of the joint portion is based on the joint side end surface A and the outer diameter B of the turbine blade. And the inner surface 2c are processed.
[0005]
However, there is a problem that the unbalanced amount of the turbine blade 2 is large due to this conventional processing step. As a result, in the above-described unbalance adjustment in the final process, there is a problem that the unbalance amount is too large, and it takes a long time for correction, or the rate of defective products that cannot be corrected is high.
There were also the following problems.
(1) There is no unbalance measurement standard for a single material.
(2) Unbalance cannot be measured at the machining reference section.
(3) The blades become thin due to weight reduction and cannot be chucked.
[0006]
The present invention has been made to solve such problems. In other words, the object of the present invention is to significantly reduce the amount of unbalance that has been inevitably generated by conventional processing methods, and by providing an unbalance measurement standard for the material, balance management during processing is possible. There is provided a method for processing a turbine blade of a turbocharger that can be processed regardless of the shape and thickness of the blades, thereby shortening the correction time of the unbalance amount and increasing the product yield. There is.
[0007]
[Means for Solving the Problems]
Conventionally, the joint is cut using the blade outer diameter portion of the turbine blade as a processing standard. However, the material of the turbine blade is a precision cast product, but the blade portion used as the processing standard is complicated in shape and thin, and the cooling speed after casting is fast, so it is deformed by the influence of shrinkage stress. large. Therefore, the accuracy considered to be necessary as a processing standard (about ± 0.02 mm) has not been obtained (the actual value is about 0.2 mm). As a result, from the measurement results described later, the center of the joint processed using the blade outer diameter as the processing reference generates a deviation from the balance center of the entire turbine blade, causing an unbalance of the entire turbine rotor shaft. It became clear.
[0008]
On the other hand, the balance center of the turbine blade is considered to be present in the center portion where the mass ratio to the surface area is larger than that of the blade and the cooling rate is low. This is because the influence of shrinkage stress is small and the accuracy can be maintained relatively easily. As a result, it became clear as a result of the measurement that the boss portion of the precision casting adjacent to the center portion substantially coincided with the balance center of the entire turbine blade.
[0009]
This application has been created based on the above-described novel findings. That is, according to the present invention, the cylindrical rotor shaft side boss portion (12) is provided in advance at the joint portion of the turbine blade (2) of the precision casting product with the rotor shaft (3), and the outer peripheral surface B of the boss portion is provided. The tip (14) of the turbine blade (2) is processed into a cylindrical shape with reference to the radial processing reference, and then the rotor shaft side boss is finished with the tip outer peripheral surface C as the radial processing reference. There is provided a method of processing a turbine blade of a supercharger.
[0010]
According to this method of the present invention, the turbine blade has a large deviation with respect to the balance center of the entire turbine blade, and the blade outer diameter portion of the turbine blade which is difficult to be gripped by a chuck or the like is not used as a machining reference in the radial direction. The rotor shaft side boss portion (12) can be finished by using two boss portions (the rotor shaft side and the tip portion) substantially coincident with the center as the processing reference in the radial direction.
Therefore, it is possible to eliminate the unbalance inevitably caused by the finishing process using the blade outer diameter part as a processing standard, and to process the rotor shaft side boss part (12) close to the balance center of the precision casting product.
[0011]
According to a preferred embodiment of the present invention, in the processing of the tip portion (14), the cylindrical end surface and the base portion are processed using the joining side end surface A of the turbine blade as the processing reference in the axial direction.
Further, in the finishing process, at least the end face (2b) and the inner face (2c) of the joint part are processed using the outer peripheral surface C and the end face or the root part D of the tip part (14) as a processing reference.
If the amount of unbalance with respect to the tip of the material is within a certain amount, it is possible to directly set the processing reference without processing.
[0012]
By this method, the end surface (2b) and the inner surface (2c) of the joint portion are processed on the basis of the outer peripheral surface of the tip portion processed with the rotor shaft side boss portion (12) as a reference, so that the boss portion (12), end surface (2b) and the inner surface (2c) can be formed concentrically close to the balance center of the precision casting, the thickness of the joint portion with the rotor shaft can be made uniform, and electron beam welding can be performed with higher accuracy. .
[0013]
DETAILED DESCRIPTION OF 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 processing method of the present invention, the turbine blade is processed in three steps: precision casting S1a, cylindrical processing S1b at the tip portion, and finishing processing S1c at the boss portion.
[0014]
In the turbine blade precision casting S1a, as shown in FIG. 2 (A), a cylindrical rotor shaft side in advance at the junction with the rotor shaft 3 of the turbine blade 2 of the precision casting product and on the rotation center of the turbine blade. A boss portion 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 at the tip of the turbine blade 2 opposite to the rotor shaft 3.
[0015]
The rotor shaft side boss portion 12 and its boss hole 2a should be as accurate as possible within precision casting so that one end of the rotor shaft can be fitted with a minimum of machining, for example, ± 0. About 01 mm. Also, the tip-side boss portion 14 is preferably provided in advance in a highly accurate cylindrical shape with the same accuracy.
[0016]
In addition, you may form the boss | hub part 14 of the front end side in a hexagonal surface or what is called a chrysanthemum like the past. In other respects, this precision casting S1a is the same as the conventional one.
[0017]
In the cylindrical processing S1b of the tip end, as shown in FIG. 2A, the tip end portion 14 of the turbine blade 2 is processed into a cylindrical shape using the rotor shaft side boss portion 12 as the processing reference B in the radial direction. In this processing, the cylindrical end surface and the root portion are processed using the joining side end surface A of the turbine blade as the processing reference in the axial direction.
[0018]
In the boss part finishing process S1c, as shown in FIG. 2B, the rotor shaft side boss part 12 is finished with the outer peripheral surface of the tip part 14 as the processing reference C in the radial direction. In this processing, the axial direction uses the end surface or the root portion D of the tip portion 14 as a processing reference. Further, in this finishing process, at least the end surface 2b and the inner surface 2c of the joint portion 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. Further, the outer diameter of the boss hole 2a and the boss portion 12 is 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) is an unbalance amount of a precision casting product (material) obtained by precision casting S1a, and (B) is an unbalance after cylindrical processing S1b of the tip portion (after tip portion processing). Amount. In each figure, the unbalance amount is indicated by the direction of the eccentric center of gravity (0 to 360 °) and the amount of eccentricity (μm). The numbers and black dots (●) in the figure are actually measured values of different materials, and white circles (○) are the average values.
The unbalance amount of the precision cast product (material) in (A) can be adjusted to some extent by correcting the casting mold.
[0020]
In FIG. 3A, the average unbalance amount is 23.72 μm (about 0.02 mm) in the direction of 34.86 °, and 15 points (No. 11 is a missing number) precision cast product (material) is this. It can be seen that the concentration is in the vicinity of the average position.
From this, it can be seen that the precision casting product (material) of the turbine blade can obtain an accuracy close to the accuracy (about ± 0.02 mm) considered necessary as a processing standard as a whole.
[0021]
However, the blade portion of the turbine blade is complicated in shape and thin, and since the cooling rate after casting is high, the blade portion is greatly deformed due to the influence of shrinkage stress. On the other hand, the ratio of the mass to the surface area of the central portion of the turbine blade is larger than that of the blade, and the cooling rate is slow. Therefore, the influence of shrinkage stress is small, and the accuracy can be easily maintained. Accordingly, 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 whole material, and substantially coincides with the balance center of the entire turbine blade.
[0022]
FIG. 3B shows an unbalance amount after processing the tip portion, and the average unbalance amount is 17.51 μm (about 0.02 mm) in the direction of 58.57 °. From this, it can be seen that 15 points (No. 11 is a missing number) after the tip end portion are concentrated in the vicinity of the average position of the precision cast product (material) before processing.
[0023]
From the comparison between (A) and (B) in FIG. 3, it can be seen that the unbalance direction and the amount of eccentricity are very similar between the material (A) and the tip processed (B). From this, it can be seen that the cylindrical processing S1b of the tip portion is performed at least in a direction that does not increase the unbalance, and the processing reference B in the radial direction is appropriate.
[0024]
FIG. 4 is a measurement result showing an unbalance amount after finishing according to the present invention and the conventional example. In this figure, (A) is the unbalanced amount of the turbine blade 2 according to the method of the present invention in which the boss portion finishing processing S1c is performed after the tip end cylindrical processing S1b, and (B) is a conventional method. The unbalance amount of the turbine blade 2 due to In each figure, the unbalance amount is indicated by the direction of the eccentric center of gravity (0 to 360 °) and the amount of eccentricity (μm). The numbers and black dots (●) in the figure are 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 workpieces (turbine blade 2) are concentrated in the vicinity of this average position. You can see that
From this, the turbine blade of the present invention can maintain the unbalance tendency of the precision casting product (raw material) as it is and can obtain an accuracy close to the accuracy considered to be necessary as a processing standard (about ± 0.02 mm). Recognize.
[0026]
On the other hand, in the conventional example shown in FIG. 4B, the average unbalance amount is 63.92 μm (about 0.06 mm) in the direction of 27.71 °, and the processed product (turbine blade) has 7 points. 2) shows that this direction and the amount of eccentricity vary greatly.
This is because the machining is based on the outer diameter of the turbine blade with a large unbalance amount.As a result, the unbalance amount in the final process is too large, and it can take a long time to correct. It can be seen that the rate of defective products increases.
[0027]
According to the method of the present invention described above, the blade outer diameter portion of the turbine blade that is largely misaligned with respect to the balance center of the entire turbine blade and is difficult to be gripped by a chuck or the like is not used as a processing standard, and the balance center of the entire turbine blade is maintained. The rotor shaft side boss portion 12 can be finished by using two boss portions (the rotor shaft side and the tip portion) that are substantially coincident with each other as a processing reference in order.
Therefore, it is possible to eliminate the unbalance inevitably generated by the finishing process using the blade outer diameter part as a processing standard, and to process the rotor shaft side boss part 12 close to the balance center of the precision casting product.
[0028]
Further, since the end surface 2b and the inner surface 2c of the joint portion are processed on the basis of the outer peripheral surface of the tip portion processed based on the rotor shaft side boss portion 12 having the boss hole 2a, the processed boss hole 2a is processed. The end surface 2b and the inner surface 2c can be formed concentrically close to the balance center of the precision casting product, the thickness of the joint portion with the rotor shaft can be made uniform, and electron beam welding can be performed with higher accuracy.
Further, by finishing the outer diameter 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 near the balance center of the precision casting product. The thickness of the joint portion can be made uniform, and electron beam welding can be performed with higher accuracy.
[0029]
Next, a method for processing parts other than the turbine blade will be described.
In FIG. 1, in the machining process of the present invention, the rotor shaft finishing process S2, the rotor shaft hardening process S3a, the rotor shaft polishing S3b, the electron beam welding S4, the turbine blade outer diameter grinding S5, and the dynamic balance Each step of adjustment S5 is included.
[0030]
The rotor shaft finishing process S2 is preferably performed to the final finishing with the rotor shaft alone without 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 processing S2 of the rotor shaft is fitted into the boss hole 2a processed in the finishing processing S1c of the turbine blade, and the joint portion is electron beam welded.
[0032]
In turbine blade outer diameter grinding S5, the turbine blade 2 is machined using the outer diameter C and end face E of the rotor shaft 3 finished in the rotor shaft finishing machining S2 as machining standards. 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 unbalance amount is measured by dynamic balance adjustment S6, and a portion of the turbine blade is shaved to adjust the unbalance to complete the turbine rotor shaft 1.
[0034]
It should be noted that the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist of the present invention. For example, in the above-described embodiment, the processing of the turbine rotor shaft of the turbocharger, 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 in the field of vacuum parts, aerospace parts, and the like. The same applies to a case where a plurality of members are welded coaxially to each other.
[0035]
【The invention's effect】
As described above, the turbocharger turbine blade machining method of the present invention can significantly reduce the amount of unbalance that was inevitably generated by the conventional machining method, and the material has an unbalance measurement standard. It is possible to manage the balance at the time of processing, and processing is possible regardless of the shape and thickness of the blade, which can shorten the correction time of the unbalance amount and increase the yield of the product. It has various excellent effects such as.
[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. 1;
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 finishing according to the present invention and a conventional example.
FIG. 5 is an overall configuration diagram of a turbine rotor shaft obtained by joining turbine blades and a rotor shaft.
FIG. 6 is a process diagram of a conventional turbine rotor shaft.
7 is a schematic diagram of FIG. 6. FIG. 8 is a process explanatory diagram for machining a joint portion of a precision casting of the turbine blade 2. FIG.
[Explanation of symbols]
1 turbine rotor shaft, 2 turbine blades, 2a boss hole, 2b end face,
2c inner surface of joint, 2d center hole, 3 rotor shaft, 3a joint end,
4 welding jig, 5 balls, 6 heads, 7 welding beads,
12 Rotor shaft side boss, 14 Tip

Claims (3)

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

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