JP3661897B2 - Edge processing method for air port on curved surface - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an edge processing method for an air port that is provided on a curved surface and requires a predetermined flow rate of air.
[0002]
[Prior art]
In an aeronautical gas turbine engine or the like, an opening is formed in a curved plate and air for cooling or the like is taken in to cool a high temperature portion. FIG. 1 is a longitudinal section showing a configuration of a cone shaft that supports a low-pressure turbine blade of a jet engine. The rear end of the rotary shaft 1 is a shaft rear end cone 1a with the axis C as the central axis. The first cone 2 and the second cone 3 are connected to the shaft rear end cone 1a and the axis C is the center. The shafts are provided in opposite directions. A low-pressure turbine blade 4 is coupled to the rear end of the first cone 2, and this rotational force is transmitted to the rotary shaft 1.
[0003]
The first cone 2 is provided with a first air port 5, and the second cone 3 is provided with a second air port 6, which is used for cooling by flowing air at a predetermined flow rate. In order to accurately estimate the flow rate of air flowing through the air ports 5 and 6, it is necessary to determine the flow coefficient of each air port 5 and 6. Further, stress concentration tends to occur around such an opening, and the fatigue strength is reduced and the life is shortened. Therefore, the shape of the stress must be reduced. For this reason, conventionally, the edge of the front surface of the opening is made to be a circular arc uniformly around the entire circumference (referred to as R). When the opening is provided in a flat plate, it is easy to take R uniformly around the entire circumference, but in the case of an opening provided in a curved plate, it is difficult to take R, so R-taking is performed by a multi-axis NC machine. It was.
[0004]
FIGS. 6A and 6B are diagrams showing R-removal by a multi-axis NC machine. FIG. 6A is a cross-sectional view, and FIG. The curved plate 10 is provided with an opening 11 having a diameter d, and the front edge portion 12 on the air inflow side is rounded by a rotary hole drilling tool 14 controlled by multi-axis NC control. The position of the R stop 13 is a concentric circle separated by t from the outer periphery of the opening. Note that R at the rear edge may be small, and the flow coefficient is not significantly affected, so that it can be easily performed manually.
[0005]
[Problems to be solved by the invention]
In this way, in order to perform R rounding uniformly on the entire circumference, a multi-axis, for example, 5-axis NC machine is required, the processing machines are limited, and the machine occupation time is long. In addition, even NC machines, the drilling tool (rotary drilling tool 14) moves stepwise, so that chattering marks (polyhedral machining traces) of the drilling tool are created on the machined surface, and finally smoothed by hand finishing. I was doing. For this reason, the cost was high, and quality and processing time varied depending on the finisher. In order to determine the flow coefficient and reduce stress concentration, it is not necessary to make the entire circumference of the opening uniform R, and it is only necessary that the distribution of R be smooth. I understand. However, since many of the same products are often produced to some extent, the same opening needs to have the same distribution of R shapes.
[0006]
The present invention has been made in view of the above-described problems, and is an air provided on a curved surface that mechanically simplifies the processing method and eliminates manual work so that the same opening has the same distribution of R shapes. An object of the present invention is to provide a mouth edge processing method.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, the front edge portion of the air port provided on the curved surface requiring a predetermined flow rate of air is set on the same axis as the air port. The rotating hole drilling tool is smoothly processed to make the edge processing range almost elliptical.
[0008]
If the rotary hole drilling tool is set on the same axis as the axis of the air port, the feed margin is set, the curved surface shape, the size of the air port, and the shape of the rotary hole drilling tool are the same, the distribution of R at the front edge portion The shape is the same. Since the machining with the rotary hole drilling tool only needs to be fed in the axial direction, the work is simple and the machining time can be reduced. Further, the processing is uniform because no hand finishing is performed.
[0009]
According to a second aspect of the present invention, the rotary hole drilling tool has a cylindrical body having a diameter larger than that of the air port, and a machining side tip has a diameter smaller than that of the air port. At least one end has a shape in which a tangent to the arc is connected.
[0010]
If the tip of the rotary hole drilling tool has a large R, only R is used. If it is slightly smaller, the R tangent is connected to one end of R, and if it is smaller, the R tangent is connected to both ends of R. Thereby, the shape of the designated R can be formed, and a rotary hole drilling tool with good cutting performance can be obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal section showing a configuration of a cone shaft that supports a low-pressure turbine blade of a jet engine. The rear end of the rotary shaft 1 is a shaft rear end cone 1a with the axis C as the central axis. The first cone 2 and the second cone 3 are connected to the shaft rear end cone 1a and the axis C is the center. The shafts are provided in opposite directions. A low-pressure turbine blade 4 is coupled to the rear end of the first cone 2, and this rotational force is transmitted to the rotary shaft 1.
[0012]
The first cone 2 is provided with a first air port 5, and the second cone 3 is provided with a second air port 6, which is used for cooling by flowing air at a predetermined flow rate. Further, a large stress is generated around these air ports 5 and 6. In order to obtain a predetermined flow coefficient and to relieve stress concentration, to increase fatigue strength and to prolong the service life, a large R is taken at the opening edge of the air inflow surface and a small R is taken at the rear opening edge of the outlet side. It is done. Since a small R can be easily removed by hand, the following description will be made on the R of the edge of the air inflow side.
[0013]
FIG. 2 is a diagram showing an air port edge processing method according to the present embodiment. The curved plate 10 has many curved surfaces having a unidirectional curve, such as a cylindrical surface or a conical surface, but there is also a double curved surface having a bi-directional curve, and this processing method is applied to any curved surface. The opening 11 has a diameter d. The front edge portion 12 is an edge portion on the air inflow side and is where the R removal is performed by the processing method of the present invention. Reference numeral 13 denotes an R stop that represents a range where the front surface is rounded. The rotating hole drilling tool 14 is a cylindrical body, and the diameter D1 of the main body 14a is larger than the opening diameter d, and the diameter D2 of the tip 14b is smaller than d. D1 and D2 are connected by an arc or a tangent to the arc. The shape of the front edge portion 12 processed by the rotary hole drilling tool 14 having this shape is an arc shape indicated by R, or an arc shape indicated by R, and a planar shape indicated by FLAT.
[0014]
FIG. 3 is a diagram showing the shape of the tip of the rotary hole drilling tool. A connection shape between the main body 14a and the tip 14b is shown, (a) shows a shape connected by a large radius R, and (b) shows a shape where a slightly smaller radius R and a tangent S of this R are connected to one end. (C) shows a shape in which a smaller radius R and a tangent S of R are connected to both ends. Which of these is used is determined by the shape of R provided on the front edge portion 12. A rotary cutter or rotary grindstone is used as the rotary hole drilling tool.
[0015]
The R edge of the front edge portion 12 may be sent by a predetermined feed allowance by aligning the axis of the opening 11 with the rotation axis of the rotary hole drilling tool 14 and rotating the rotary hole drilling tool 14. The shape of R to be machined is determined by the shape and feed allowance of the tip of the drilling tool shown in FIG. These can be calculated in advance based on the shape of the curved plate 10 and the size of the opening 11. Since the processing method is simple as described above, if the curved plates 10 having the same shape are provided with the openings 11 having the same diameter, it is possible to easily perform R-removal having the same shape.
[0016]
In determining the shape and distribution of R of the front edge portion 12, an analysis is performed so that the flow coefficient becomes a predetermined value and the fatigue strength due to stress concentration becomes a predetermined value. As a result of the analysis, it has been found that a large decrease in the flow coefficient and a large decrease in fatigue strength do not occur even if the entire circumference is not set to the same R as in the prior art.
[0017]
4 shows the first air port 5 shown in FIG. 1, (a) is a view taken along the line AA in FIG. 1, (b) is a sectional view taken along the line DD in (a), and (c) is (a). It is EE sectional drawing of. In the case of a cone, the ridge line is a straight line, but in the case of the first air port 5, it is a curved line as shown in (b), and the surrounding curved surface of the first air port 5 is a double curved surface. Since the curvature of the conical surface with respect to the central axis C changes along the ridgeline, the distance from the outer periphery of the opening to the R stop 13 is different from t1 on the lower side and t2 on the upper side. Since the left and right sides of the DD cross section are the same curved surface, the distance from the outer periphery of the opening to the R stop 13 is t3. For this reason, the shape of the R stop is symmetrical, but the top and bottom are different and are deformed ellipses. In this case, the rounded shape around the position indicated by the length t1 is a shape connecting R and a straight line. D1 indicates the diameter of the first air port 5.
[0018]
FIG. 5 shows the second air port 6 shown in FIG. 1, (a) is a view taken along arrow BB in FIG. 1, (b) is a sectional view taken along line FF in (a), and (c) is (a). It is GG sectional drawing of. Since the surrounding curved surface of the second air port 6 is a simple cone, the FF cross section is a straight line. Further, the GG section is symmetric with respect to the FF section. Even if it is a simple cone, the curvature of the conical surface with respect to the central axis C changes along the ridgeline. Therefore, the distance from the outer periphery of the opening to the R stop 13 differs between the lower side and the upper side, but the R stop 13 becomes a deformed ellipse. When the size of the opening d2 indicating the diameter of the second air port 6 is small, the distance from the outer periphery of the opening to the R stop 13 may be the same if the manufacturing allowance value is considered on the lower side and the upper side. In the case of the present embodiment, the second air port 6 is smaller than the first air port 5. For this reason, as shown in (a), the R stop 13 is an ellipse, and the distance from the outer periphery of the opening to the R stop 13 is t4 in the top and bottom in the FF section and t5 in both the left and right in the GG section.
[0019]
【The invention's effect】
As is clear from the above description, the present invention provides a predetermined flow rate by setting the edge of the air port provided on the curved surface to the same axis as the axis of the air hole, and feeding a predetermined flow rate. R-removal having a coefficient and fatigue strength can be performed. Since this method is simple and does not require hand finishing, it can be mass-produced with the same finished shape and requires less machining time.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a low-pressure turbine cone shaft showing an embodiment of the present invention.
FIG. 2 is a diagram showing a processing method of the present embodiment.
FIG. 3 is a diagram showing the shape of the tip of a rotary hole drilling tool.
4 is an AA arrow view of FIG. 1;
FIG. 5 is a view taken along arrow BB in FIG. 1;
FIG. 6 is a diagram for explaining a conventional processing method of an air port provided on a curved surface.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotating shaft 1a Shaft rear end cone 2 1st cone 3 2nd cone 4 Low pressure turbine rotor blade 5 1st air port 6 2nd air port 10 Curved plate 11 Opening 12 Front edge part 13 R stop 14 Rotating hole opening tool 14a Main body Tip of part 14b

Claims (2)

The front edge part of the air port provided on the curved surface that requires a predetermined flow rate of air is smoothly machined by a rotary hole drilling tool with the rotation axis set on the same axis as the air port, and the edge machining range An edge processing method for an air port provided on a curved surface, wherein The rotary hole drilling tool has a cylindrical body having a diameter larger than that of the air port, and a tip on the processing side has a diameter smaller than that of the air port. The connection shape between the tip and the main body is an arc or an arc and at least one end thereof. 2. A method for processing an edge of an air port provided on a curved surface according to claim 1, wherein a tangent to the arc is connected.

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