JPH06270006A - Working of arcuate root groove of turbine moving blade - Google Patents

Abstract

(57) [Summary] [Purpose] Highly efficient and highly accurate cutting of circular arc root grooves of turbine blades. [Structure] The surface of the turbine rotor blade 1 of the arc root groove 2 after rough machining is divided into 4 sections, and the cutting tool 3 is divided into 2 sections.
The cutting direction is the combined direction of the radial direction of the arc of the arc root groove to be cut and the axial direction of the turbine rotor blade 1. The cutting direction is set to be different for each cutting process, that is, the upper left direction 9, the lower left direction 10, the upper right direction 11, and the lower right direction 12. For example, the to-be-cut portion 13 shows a cutting finish portion by the upper cutting edge 7 located above the axial center line when the cutting direction is the upper left direction 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for machining an arc root groove of a turbine rotor blade, which is provided to combine a root portion of a turbine rotor blade with an outer peripheral groove of a turbine disk by cutting and finishing an arc root groove of the root portion of the turbine rotor blade. Regarding

[0002]

2. Description of the Related Art A conventional turbine blade arc root groove machining method will be described with reference to FIGS.

FIG. 5 is an explanatory view of a combination of an outer peripheral groove of a turbine disk and an arc root groove of a turbine rotor blade. In FIG. 5, (a) of FIG. 5 is a perspective view of a turbine rotor, and FIG. (B) is an enlarged view of part A of (a) of FIG. 5, (c) of FIG.
FIG. 6 is a sectional view taken along line BB in FIG.

FIG. 6 is an explanatory view of a conventional turbine blade arc root groove processing device and processing tool.
6B is a plan view and a side view, FIG. 6C is an enlarged view of a main part of FIG. 6B, and FIG. 6D is an arrow view of FIG. 6C.

As shown in FIG. 5, the turbine rotor blade 1 has a rotor disk 41 fixed to a rotor shaft 40.
The disk outer peripheral groove 42 and the circular arc root groove 43 provided at the root of the turbine rotor blade 1 are combined to be integrated with the rotor shaft 40.

While the rotor shaft 40 is rotating, a centrifugal force is applied to the turbine rotor blade 1. In this case, the centrifugal force is entirely applied to the surface where the disk outer peripheral groove 42 and the circular arc root groove 43 contact each other, that is, the disk outer peripheral groove and the circular arc. Received at the contact surface 44 with the root groove,
A force of several tens of tons per turbine moving blade 1 is applied to the contact surface 44 between the disk outer peripheral groove and the arc root groove for a long period of time.

Therefore, strict quality control is performed on each material of the rotor shaft 40 and the turbine rotor blade 1 and the accuracy of the arc root groove 43.

In particular, in order to equalize the distribution of the stress generated in the contact surface 44 between the disk outer peripheral groove and the arc root groove, the contact surface 44 between the disk outer peripheral groove and the arc root groove is formed between the adjacent contact surfaces. The dimensions, that is, the pitch and the arc of the arc root groove 43 must be machined with an accuracy of the order of microns.

Conventionally, as shown in FIG. 6, a turbine rotor blade 1 mounted on an arc feed table 47 provided at the tip of an arm 48 which reciprocates around a center of reciprocation with respect to a general-purpose end mill 45. The arc root groove 43 is cut depending on whether the arc feed is performed or the spindle head 46 to which the shaping end mill 45 is attached is fed to the turbine rotor blade 1 in the arc.

In addition, in FIG. 6C, the form end mill 45 is shown.
In the figure, 49 represents the minimum diameter of the cutting edge, and 50 represents the maximum diameter of the cutting edge. Also, FIG. 6 (d)
Shows the shape of the cutting edge when the general-purpose end mill 45 is viewed from the other direction.

[0011]

However, in the case of cutting the arc root groove of the turbine rotor blade by such a method,
There were the following problems. That is, (1) the ratio between the maximum diameter and the minimum diameter of the cutting edge of the general-purpose end mill is about 4, and this ratio is a large value, so it is not possible to obtain appropriate cutting conditions common to all the cutting edges. Therefore, the cutting efficiency has to be reduced because the cutting conditions have to be adjusted according to the optimum cutting conditions on the low cutting specification side.

(2) Since the general-purpose end mill processing is one-pass processing with only the forward cutting stroke, the cutting resistance becomes excessive and cutting vibration is likely to occur. In addition, in order to maintain the machining accuracy, when the minute cutting feed is used, the machining efficiency is significantly reduced.

The present invention has been made in view of the above situation, in which an arc root groove after rough machining in a turbine rotor blade is
The purpose is to obtain a method for cutting and finishing with high processing accuracy and high processing efficiency.

[0014]

The above object can be achieved as follows.

(1) Rough machining in a turbine blade arc root groove machining method for cutting an arc root groove provided in a root portion of a turbine rotor blade in order to combine a root portion of the turbine rotor blade with an outer peripheral groove of the turbine disk. A cutting tool equipped with a cutting edge that cuts the surface to be cut of the subsequent arc root groove in the forward stroke and a cutting edge that cuts in the return stroke in opposite directions reciprocates on the arc trajectory of the arc root groove. Can be mounted on a tool post of a device that can adjust the position in the radial direction of the circular arc and the axial direction of the turbine moving blade, and for each of the forward stroke and the return stroke, the radial direction of the circular arc and the turbine moving blade. Adjust the position of the tool and the axial direction to give a cut to the cutting tool and finish the cutting of the arc root groove.

(2) In (1), the surface to be cut of the arc root groove after rough machining is divided into four sections, and each section of the four sections is for each of the forward stroke and the return stroke of the cutting tool. And then reciprocating the cutting tool twice on the circular arc path.

(3) In a method for machining a circular arc root groove of a turbine rotor blade, the arc root groove provided in the root portion of the turbine rotor blade is cut to combine the outer peripheral groove of the turbine disk with the root portion of the turbine rotor blade. Prepare a cutting tool (A) and a cutting tool (B) that are diagonally provided with a cutting edge that cuts in the forward stroke and a cutting edge that cuts in the return stroke on the surface to be cut of the subsequent arc root groove. A tool rest of a device capable of reciprocating both the tool (A) and the cutting tool (B) on the circular arc trajectory of the circular arc root groove and adjusting the position in the radial direction of the circular arc and the axial direction of the turbine blade. The cutting tool (A) adjusts the radial position of the circular arc and the cutting tool (B) adjusts the axial position of the turbine rotor blade to make a cut for each forward stroke and return stroke. Cutting finish of arc root groove after rough machining It is carried out.

(4) In (3), the surface to be cut of the arc root groove after rough machining is divided into four sections, and each of the four sections is divided into a cutting tool (A) and a cutting tool (B). Cutting is performed for each of the forward stroke and the return stroke, and the cutting tool (A) and the cutting tool (B) are reciprocated once each on the circular orbit.

[0019]

In the present invention, the surface to be cut of the arc root groove after rough machining is divided into four sections, and each section is
Adjusting the radial direction of the arc root groove and the axial position of the turbine blade, and making a cut in the combined direction of the radial direction of the arc and the axial direction of the turbine blade, each stroke of the forward stroke and the return stroke. Each section is cut, and the cutting tool is reciprocated twice to finish the arc root groove after rough machining.

As described above, the cut surface of the arc root groove after the rough machining is sequentially provided with the different incisions in the above-described four synthetic directions, and the arc root groove is cut and finished under a small cutting resistance. Therefore, cutting vibration is not generated, high processing accuracy can be maintained, and cutting finishing efficiency is improved.

Further, by using two kinds of cutting tools, the surface to be cut divided into four sections of the arc root groove after rough machining is provided, and in one cutting tool, a cut is made only in the radial direction of the arc of the arc root groove. Then, one section is cut in each of the forward stroke and the return stroke, and then a cut is made only in the axial direction of the turbine blade by the other cutting tool, and one section is divided in each of the forward stroke and the return stroke. Cut and finish.

In this case, it is necessary to replace the cutting tool during the finishing of the cutting, but unlike the above case, the cutting direction does not take the combined direction, so that the cutting edge can be easily formed. Have.

[0023]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is an explanatory view of a cutting finishing method according to an embodiment of the present invention. FIG. 1 (a) is a plan view of a cutting finishing device,
1B is a view in the direction of the arrow in FIG. 1A, FIG. 1C is a vertical cross-sectional view of a cutting tool according to an embodiment of the present invention, and FIG.
It is CC sectional drawing of (c).

FIG. 2 is an explanatory view of a cutting example in one embodiment of the present invention. FIG. 2 (a) is a longitudinal sectional view when the cutting tool is in operation, and FIG. 2 (b) is when starting cutting. 2C is an explanatory view of setting the cutting tool reference position, FIGS. 2C and 2D are explanatory views immediately before and immediately after the start of cutting in the forward process of the cutting tool, and FIGS. 2E and 2F are cutting tools. FIG. 7 is an explanatory diagram immediately before the start of cutting and immediately after the end of cutting in the returning step of FIG.

In FIGS. 1A and 1B, the cutting tool 3
Is attached to a tool rest 4 installed at the tip of the swing arm 5, and the arc in which the cutting tool 3 is about to finish cutting the arc root groove 2 after rough machining at the root of the turbine rotor blade 1 It is fixed to the tool rest 4 so that it can reciprocate in an arcuate path that is as close as possible to the arc of the root groove 43 (see FIG. 5).

That is, at each starting point of the stroke in which the cutting tool 3 reciprocates, the tool rest 4 is moved with respect to the swing arm 5 so that the cutting tool 3 can be given a predetermined cut.

A cutting tool 3 is shown in FIGS. 1 (c) and 1 (d). The cutting tool 3 has two cutting edges diagonally attached to each other as shown in the drawings. For convenience of explanation, with the axis center line of the cutting tool 3 in FIG. 1 (c) as a boundary, the cutting edge located above it will be referred to as the upper cutting edge and the cutting edge located below will be referred to as the lower cutting edge. . That is, in FIG.
In (c), 7 indicates an upper cutting edge and 8 indicates a lower cutting edge, and the cutting tool 3 is also called a forming tool.

FIG. 2 (a) shows the cutting finish of the arc root groove 2 after rough machining. In this embodiment, the cutting location is divided into four areas, and the cutting tool 3 is reciprocated twice to perform the cutting finish, so that the cutting stroke is performed twice in each of the forward stroke and the return stroke. In addition, each of the cuts has a different cut direction.

The cutting directions are the combined direction of the radial direction of the arc of the arc root groove 43 and the axial direction of the turbine rotor blade 1. The combined directions are the upper left direction 9 and the lower left direction in FIG. 2 (a). There are four directions: 10, an upper right direction 11, and a lower right direction 12. For example, the cut portion 13 is a cut portion by the upper cutting edge 7 when the cutting direction is the upper left direction 9. The order of selecting the cutting directions is not particularly limited, and the order of the cutting directions is selected so that the given cutting tool 3 and cutting conditions can be optimally handled. Of FIG.
(b) to (f) show the cutting finish state by the cutting tool 3 in each of the forward stroke and the return stroke when the cutting tool 3 reciprocates.

That is, in FIG. 2B, at the start of cutting, the cutting tool 3 is inserted into the arc root groove 2 after rough machining, and the center point of the cutting tool 3 is set to the tool setting reference position 18. It shows the situation when alignment is performed. Insertion gap amount 15
Is a radius difference between the root groove width 17 after rough machining and the maximum diameter of the cutting tool 3, and is provided to facilitate insertion of the cutting tool 3 into the blade root groove 2 after rough machining. It is a thing. Therefore, when the cutting tool 3 is cut, the cut amount 19 has a value obtained by adding the finishing allowance 16 to the insertion gap amount 15.

Reference numeral 20 in FIG. 2 (c) is immediately before the start of the forward stroke, 21 in FIG. 2 (d) is immediately after the end of the forward stroke, and 22 in FIG. 2 (e).
Indicates the position of the center point of the cutting tool 3 with respect to the arc-shaped root groove 2 after rough machining immediately before the start of the return stroke and 23 in (f) of FIG. 2 immediately after the end of the return stroke.

That is, in the first cutting process, in each of the forward stroke and the return stroke, among the four directions of the upper left direction 9, the lower left direction 10, the upper right direction 11 and the lower right direction 12 in FIG. , So that one of the remaining cutting directions is not overlapped in each of the forward stroke and the return stroke in the second cutting process. select. In this way, one of the four sections of the surface to be cut is successively cut and finished.

In the case of this embodiment, since the surface to be cut is divided into four sections, the amount of cutting in each of the forward stroke and the return stroke is small, and the cutting vibration is significantly reduced, so that high machining accuracy can be obtained. Moreover, since the processing speed can be increased, the processing efficiency can be improved.

Next, another embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is an explanatory view of axial cutting, and FIG.
(a) is a longitudinal sectional view of the cutting tool in operation, (b) of FIG. 3 is of FIG.
It is an EE sectional view of (a). 4 is an explanatory view of the radial direction cutting, FIG. 4 (a) is a vertical cross-sectional view when the cutting tool is in operation, and FIG. 4 (b) is a P arrow view of FIG. 4 (a). .

The present embodiment is different from the above-mentioned embodiments in that only one cutting tool is used and the cutting direction of the cutting edge is the radial direction of the arc of the arc root groove 43. In contrast to the combined direction of the turbine blade 1 and the axial direction of the turbine blade 1, in the present embodiment, two cutting tools having different cutting edges are used, and the cutting directions of the cutting edges are two. One of them is divided by the cutting tool so that one is in the radial direction of the arc of the arc root groove 43 and the other is in the axial direction of the turbine rotor blade 1.

FIG. 3A shows a situation in which the arc root groove 2 after rough machining is cut and finished when the cutting direction of the cutting blade is the axial direction of the turbine rotor blade 1. (b) shows the shape of the cutting edge of the axial cutting tool 24 used at that time, respectively. Further, when the cutting direction of the cutting blade is the axial direction of the turbine rotor blade 1, there are two cutting directions, that is, the upward direction 25 and the downward direction 26 shown in FIG. (a) shows the case of the upward direction 25.

That is, the axial cutting tool 2 shown in FIG.
When the cutting edge located above the axis center line in 4 is the upper cutting edge 27 and the lower cutting edge is the lower cutting edge 28,
In FIG. 3 (a), the upper cutting edge 2
This is the case where the cut portion 29 is cut and finished by using No. 7. After the completion of this cutting finish, a cut is made in the downward direction 26, and the opposite side is processed using the cutting edge 28.

Next, an axial cutting tool is used to finish the remaining surface to be cut, which will be described.

FIG. 4A shows a situation in which the arc root groove 2 after rough machining is cut and finished when the cutting direction of the cutting edge is the radial direction of the arc of the arc root groove 43. In (b) of 4,
The shape of the cutting edge of the radial cutting tool 30 used at that time is
Shown respectively.

At this time, the radial cutting tool 30 is used,
The cutting direction is two directions, that is, the left direction 31 and the right direction 32 of FIG. That is, first, a cut is made in the left direction 31, the cut part 36 is cut and finished by the cutting blade parts 33, 34, and 35, and then a cut is made in the right direction 32, and the cut blade parts 37, 38, etc. The cutting portion 39 is cut and finished.

In this method, it is necessary to replace the axial cutting tool 24 with the radial cutting tool 30 in the course of cutting finishing, but the cutting directions of these cutting tools are not the combined directions as in the above-mentioned embodiment. Therefore, the cutting edge of the cutting tool can be easily formed, and the cutting tool can be manufactured at low cost.

[0043]

According to the method of the present invention, in the case of cutting and finishing the arc root groove of the turbine blade moving blade, it is possible to carry out the cutting and finishing with the optimum cutting specifications for all the cutting edges, and the working efficiency is improved. Further, since the depth of cut can be freely set, even if the finishing allowance is large, it is possible to perform cutting with the most appropriate depth, high machining accuracy is obtained, and reliability of the arc root groove for cutting finish is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a cutting finishing method according to an embodiment of the present invention.

FIG. 2 is also an explanatory diagram of a cutting example.

FIG. 3 is an explanatory diagram of axial cutting according to another embodiment of the present invention.

FIG. 4 is likewise an explanatory view of radial cutting.

FIG. 5 is an explanatory diagram of a combined portion of a disk outer peripheral groove and an arc root groove of a moving blade.

FIG. 6 is an explanatory view of a conventional turbine blade arc root groove processing device and processing tool.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Turbine blade, 2 ... Arc root groove after rough machining, 3 ... Cutting tool, 4 ... Tool rest, 5 ... Swing arm, 6 ... Crank mechanism, 7 ... Upper cutting edge, 8 ... Lower cutting edge, 9 ... Top left direction, 1
0 ... lower left direction, 11 ... upper right direction, 12 ... lower right direction, 13
… Cut part, 14… Tool maximum width, 15… Insertion gap amount, 1
6 ... Finishing allowance, 17 ... Root groove width after rough machining, 18 ... Tool setting reference position, 19 ... Depth of cut, 20 ... Tool position immediately before the start of the forward stroke, 21 ... Tool position immediately after the end of the forward stroke, 2
2 ... Tool position immediately before the start of the return stroke, 23 ... Tool position immediately after the end of the return stroke, 24 ... Axial cutting tool, 25
... upward, 26 ... downward, 27 ... upper cutting edge, 28 ... lower cutting edge, 29 ... cutting portion, 30 ... radial cutting tool, 31 ...
Left direction, 32 ... Right direction, 33, 34, 35 ... Left cutting edge cutting edge, 36 ... Cutting portion, 37, 38 ... Right cutting edge cutting edge, 39 ... Cutting portion, 40 ... Rotor shaft ,
41 ... Rotor disk, 42 ... Disk outer peripheral groove, 43 ...
Arc root groove, 44 ... Contact surface between disk outer peripheral groove and arc root groove, 45 ... General-purpose end mill, 46 ... Spindle head, 47 ...
Arc feed table, 48 ... Arm, 49 ... Minimum diameter of cutting edge, 50 ... Maximum diameter of cutting edge.

Claims (4)

[Claims] 1. A method for machining a circular arc root groove of a turbine rotor blade, comprising: cutting a circular arc root groove provided at a root portion of the turbine rotor blade to combine a root portion of the turbine rotor blade with an outer peripheral groove of the turbine disk. A cutting tool provided with a cutting edge that cuts the surface to be cut of the arc root groove in the forward stroke and a cutting edge that cuts in the return stroke diagonally, and reciprocates on the arc trajectory of the arc root groove. It is attached to a tool rest of a device that can be moved and the position of which can be adjusted in the radial direction of the circular arc and the axial direction of the turbine rotor blade, and the arc of the circular arc can be adjusted for each of the forward stroke and the return stroke. A method for machining an arc root groove of a turbine blade, which comprises: adjusting a position between a radial direction and an axial direction of the turbine blade to give a cut to the cutting tool to finish the cutting of the arc root groove. 2. The surface to be cut of the arc root groove after the rough machining is divided into four sections, and one section of each of the four sections is provided for each of the forward stroke and the return stroke of the cutting tool. The method for machining an arc root groove of a turbine rotor blade according to claim 1, wherein the cutting tool is cut and the cutting tool is reciprocated twice on an orbit of the arc. 3. A turbine rotor blade arc root groove machining method for cutting an arc root groove provided at a root portion of a turbine rotor blade in order to combine a root portion of a turbine rotor blade with an outer peripheral groove of a turbine disk. A cutting tool (A) and a cutting tool (B) provided with a cutting edge that cuts the surface to be cut of the arc root groove afterwards in a forward stroke and a cutting edge that cuts in a return stroke are diagonally provided, Both the cutting tool (A) and the cutting tool (B) can reciprocate on the circular arc orbit in the circular arc root groove, and the position can be adjusted in the radial direction of the circular arc and the axial direction of the turbine blade. The cutting tool (A) in the radial direction of the cutting tool (A) and the cutting tool (B) in the axial direction of the turbine blade for each of the forward stroke and the return stroke. Adjust the position of and make a cut By performing the cutting, the arc root groove after the rough machining is cut and finished. 4. The surface to be cut of the arc-shaped root groove after the rough machining is divided into four sections, and each section of the four sections is used for the cutting tool (A) and the cutting tool (B). The cutting tool is cut after each stroke of the stroke and the return stroke.
The turbine blade arc root groove machining method according to claim 3, wherein (A) and the cutting tool (B) are reciprocated once each on the orbit of the arc.