JP2013104321A - Method for manufacturing impeller of centrifugal rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an impeller, designed to form a channel by electrical discharge machining and smooth a polished surface without undulation in removing an alteration layer generated on an electrical-discharge-machining surface by chemical polishing.SOLUTION: The method for manufacturing the impeller includes: a channel formation step of forming a channel 14 of an impeller 10 of a centrifugal rotating machine by electrical discharge machining; and a chemical polishing step of polishing an inner wall of the channel 14 by chemical polishing. In the chemical polishing step, the impeller 10 immersed in a polishing solution 23 rotates around a rotational axis C thereof.

Description

  The present invention relates to a method for manufacturing an impeller used in a centrifugal rotating machine such as a centrifugal compressor.

As an impeller for a centrifugal compressor, there is known an impeller provided with a disk provided on a rotating shaft, a cover facing the disk, and a plurality of blades for partitioning a space between the disk and the cover.
In this impeller, a portion surrounded by the mutually facing surfaces of the disk and the cover and the side surface of the blade is a flow path for compressing the gas. This flow path is gradually curved from the gas inlet opening along the axial direction on the inner peripheral side of the impeller toward the outer peripheral side, and has a complicated shape with the outlet opening along the radial direction at the outer peripheral end. . Until now, an impeller having such a flow path is usually manufactured by dividing a disk, a cover, and a blade into two or three members and welding these members. However, technical difficulties are involved in performing the welding soundly.

Therefore, it is often performed to manufacture an impeller from an integral material. In this case, electric discharge machining is employed as a method for forming a flow path (for example, Patent Documents 1 and 2). When electric discharge machining is performed, the workpiece is repeatedly melted and solidified, so that a deteriorated layer that is very hard and has many cracks is formed. Therefore, in Patent Documents 1 and 2, this deteriorated layer is removed by pickling.
Patent Document 3 describes that the pickling solution is stirred by rotating a stirring blade when the deteriorated layer by electric discharge machining is removed by pickling.

JP 2010-89190 A JP 2010-285919 A JP-A-8-300228

  However, according to the study by the present inventors, when wet polishing is performed, a fine streak-shaped portion 91 whose polishing amount is smaller than other portions is formed on the polishing surface 90 as shown in FIG. confirmed. Due to the presence of the stripe-shaped portion 91, the polishing surface 90 undulates in the height direction. This swell W hinders the flow of the centrifugally rotated fluid and causes pressure loss.

  The present invention has been made on the basis of the above-described problems, and the purpose thereof is to form a flow path by electric discharge machining, and then swell in removing the altered layer generated on the electric discharge machining surface by wet polishing. An object of the present invention is to provide an impeller manufacturing method capable of smoothing a polished surface without causing it.

When the present inventors searched for the above-mentioned waviness W, it was found that the hydrogen gas generated by the oxidation-reduction reaction accompanying wet polishing was the cause of the waviness W. In other words, since the hydrogen gas becomes bubbles and stays along the polishing surface (processed surface), polishing of the portion where contact between the processing surface and the polishing liquid is hindered does not proceed, so that the portion where polishing has progressed does not proceed. As a result, the waviness W occurs.
Here, as in Patent Document 3, even if the agitating blade is rotated to agitate the polishing liquid, it is not sufficient to suppress the generation of waviness W and smooth the polished surface. It is understood that it is difficult to exert the stirring effect of the polishing liquid even in the flow path of the impeller having a complicated shape.

The impeller manufacturing method of the centrifugal rotator of the present invention made therein includes a flow path forming step for forming the flow path of the impeller by electric discharge machining, and a wet process for wet polishing the inner wall of the flow path by immersing the impeller in a polishing liquid. A polishing step, and in the wet polishing step, the impeller is rotated around its rotation axis.
In the present invention, by rotating the impeller, the polishing liquid in the flow path flows along the flow path, and the polishing liquid outside the flow path is also sequentially supplied into the flow path, so that a predetermined flow velocity is generated in the flow path. A polishing liquid flow having a thickness is formed. The energy generated by this polishing liquid flow forcibly releases hydrogen gas from the inner wall of the flow channel (which is the electric discharge machining surface and the polishing surface). In addition to the polishing liquid flow, the vibration generated on the inner wall of the flow channel by the rotation of the impeller also promotes the detachment of hydrogen gas from the inner wall of the flow channel. Thereby, the polishing liquid uniformly contacts the inner wall of the flow path without hindering the contact between the polishing liquid and the inner wall of the flow path by the hydrogen gas. Therefore, according to the present invention, the occurrence of the swell described above can be avoided or suppressed, so that the inner wall of the flow path can be smoothed.
In the present invention, “wet polishing” is a general term for chemical polishing and electrolytic polishing.

Since the shape accuracy of the flow path is ensured by the smoothing of the inner wall of the flow path described above, the predetermined performance of the centrifugal rotating machine can be satisfied, but the inventors of the present invention have the following in order to improve the performance. We focused on the difference (unevenness) in the polishing amount described in.
Depending on the shape of the flow path of the impeller, the flow rate of the polishing liquid flow is assumed to be different at each part in the flow path. If it does so, since the site | part with a high flow rate becomes easy to grind | polish, the site | part with a slow flow rate becomes difficult to grind | polish, Therefore The grinding | polishing amount may arise by the site | parts in a flow path.
Therefore, it is preferable to change the rotational speed of the impeller in the wet polishing process according to the present invention.
Changing the rotation speed of the impeller can be realized, for example, by the following form. The change in the rotational speed is a concept including the direction of rotation.
(A) The forward rotation in which the impeller is rotated in the same direction as when the centrifugal rotator is operated and the negative rotation in which the impeller is rotated in the opposite direction are alternately repeated.
(B) In (a), a non-rotation for stopping the rotation of the impeller is inserted between the positive rotation and the negative rotation.

According to the present invention, when the rotational speed of the impeller is changed, the change in the flow rate of the polishing liquid flow follows this, and the flow rate of the polishing liquid flow in the portion in the flow path changes. The part can be interchanged, and unevenness in polishing amount can be reduced. Thereby, since it becomes easier to ensure the shape accuracy required for the flow path, the performance of the centrifugal rotating machine can be improved.
In particular, by inserting non-rotation between the positive rotation and the negative rotation, it is possible to gradually move the portion that is easily polished according to the direction of rotation, which can contribute to smoothing the inner wall of the flow path.

In the wet polishing process of the present invention, the impeller can be precessed.
The impeller that performs precession reciprocates in the vertical direction during one rotation, so that the polishing liquid flow has a considerable speed in the vertical and radial directions, particularly on the outer peripheral side in the flow path. As a result, the stagnation of hydrogen gas on the inner wall of the flow path can be prevented more reliably, so that the polished surface can be further smoothed.

In the wet polishing step of the present invention, electrolytic polishing may be performed using a rotating structure including an electrode inserted into the flow path.
The rotating structure includes a movable conductor and a fixed conductor in addition to the electrodes.
The movable conductor supports the electrode and rotates with the impeller.
Electric power is supplied to the fixed conductor from the outside.
The power supplied to the fixed electrode is supplied to the electrode through the movable conductor.
When the impeller is rotated, the movable conductor rotates with the impeller, but the fixed conductor does not rotate. For this reason, it is not necessary to move the power supply connected to a fixed conductor with the rotation of the impeller. Therefore, it is possible to maintain power supply to the electrodes without providing a moving mechanism accompanying the rotation of the impeller in the power source.

  According to the impeller manufacturing method of the centrifugal rotating machine of the present invention, the polished surface can be smoothed without causing waviness when the altered layer generated on the inner wall of the flow path by electric discharge machining is removed by wet polishing.

It is a top view of the impeller of the centrifugal rotating machine concerning a 1st embodiment. It is sectional drawing (II-II arrow line view of FIG. 1) along the flow path of the impeller. It is a figure which shows the wet polishing apparatus used in 1st Embodiment. 10 is a polishing timing chart according to the second embodiment. It is a schematic diagram which shows the difference (nonuniformity) of the grinding | polishing amount which arises in an impeller channel inner wall. It is a grinding | polishing timing chart which concerns on the modification of 2nd Embodiment. 10 is a polishing timing chart according to another modification of the second embodiment. It is a figure which shows the wet polishing apparatus used in 3rd Embodiment. It is a figure which shows the wet polishing apparatus used in 4th Embodiment. It is a figure which shows the wet polishing apparatus used in 5th Embodiment. It is a perspective view which shows the movable conductor and electrode with which the wet polishing apparatus used in 5th Embodiment is provided. It is a perspective view which shows the waviness of a grinding | polishing surface typically.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
[First Embodiment]
The impeller 10 shown in FIGS. 1 and 2 is mounted on a centrifugal rotator such as a centrifugal compressor as a rotating body assembled to a rotating shaft of the centrifugal rotator. The impeller 10 divides the substantially disc-shaped disk 11 provided coaxially with the rotating shaft of the centrifugal rotator, the cover 12 facing the disk 11 with a space therebetween, the disk 11 and the cover 12, and the gas flow The impeller 10 including the disk 11, the cover 12, and the blade 13 includes a plurality of blade-shaped blades 13 that form a path 14 as main components. The impeller 10 includes a high-strength heat-resistant alloy such as stainless steel. It is formed from the material by electric discharge machining.

  The side close to the rotation axis C along the rotation axis is the inner peripheral side of the impeller 10, and the far side is the outer periphery side. In the following, it is assumed that the upper and lower sides are defined based on the upper and lower sides in FIG. Further, in FIG. 1, the gas flows in the direction of arrow F in the flow path 14.

The disk 11 has a shaft hole 110 into which the rotation shaft is inserted. The surface 11a of the disk 11 is curved so as to gradually protrude upward from the outer peripheral side toward the inner peripheral side.
The cover 12 having an annular shape concentric with the disk 11 is also curved so as to gradually protrude upward from the outer peripheral side toward the inner peripheral side, following the shape of the surface 11a of the disk 11.

The blades 13 are provided radially about the rotation axis C between the front surface 11a of the disk 11 and the back surface 12a of the cover 12 facing each other. The blade 13 is curved following the shape of the surface 11 a of the disk 11 and is also curved in the circumferential direction of the disk 11.
A space defined by a pair of side surfaces 13 a of adjacent blades 13, a surface 11 a of the disk 11, and a back surface 12 a of the cover 12 is a gas flow path 14 introduced into the centrifugal rotator.
The flow path 14 has a curved shape with respect to both the radial direction and the rotation axis direction, and is formed by electric discharge machining (shape engraving electric discharge machining).

  When the impeller 10 of the rotary compressor configured as described above is rotationally driven around the rotation axis C by a drive unit (not shown), an arrow F pointing from the radially inner periphery side to the outer periphery side in the flow path 14 The gas flow shown is generated and the gas is accelerated by the centrifugal force generated by the rotation. As a result, the air sucked from the inlet 141 of the flow path 14 is compressed in the flow path 14, discharged from the outlet 142, and sent to an external device (not shown).

When manufacturing the impeller 10, a wet polishing apparatus 20 (FIG. 3) is used to remove the altered layer generated on the inner wall (the front surface 11 a, the back surface 12 a, and the side surface 13 a) of the flow path 14 by electric discharge machining.
The wet polishing apparatus 20 includes a mounting base 21 that has a rotating shaft 22 that is assembled in the shaft hole 110 of the impeller 10 and supports the impeller 10, and a polishing liquid tank 24 that stores the impeller 10 together with the polishing liquid 23.
The installation base 21 is a disk having a diameter larger than that of the impeller 10, and the impeller 10 is placed on the installation base 21 with the cover 12 facing upward. The rotating shaft 22 is connected to a drive unit (motor) 25.

As polishing liquid 23, what contains a specific acid, an alkali, and a salt in a component can be used. As the polishing liquid 23 for chemical polishing, for example, a polishing solution containing 8 wt% H ₂ O ₂ and ₄ wt% NH ₄ HF can be used. Moreover, as the polishing liquid 23 for electropolishing which will be described later, for example, one containing 85 wt% of phosphoric acid (H ₃ PO ₄ ) can be used. All of the polishing liquids exemplified here are suitable for carbon steel.
The polishing liquid tank 24 has an opening larger than the installation base 21 that supports the impeller 10, and an amount of polishing liquid 23 sufficient to be immersed up to the upper end of the impeller 10 is placed therein. The polishing liquid tank 24 has a liquid inlet 241 for replenishing the polishing liquid 23 and a liquid outlet 242 for discharging the polishing liquid 23, and is controlled by a liquid management device (not shown) by dissolving the metal. The deteriorated polishing liquid 23 is replaced with a new one.

Next, a method for manufacturing the impeller 10 will be described focusing on the wet polishing process by the wet polishing apparatus 20 described above.
First, each flow path 14 is formed by sculpting an integral material having a separate outer shape and performing electric discharge machining. Thereby, the impeller 10 including the disk 11, the cover 12, the blade 13, and the flow path 14 is molded.
In the sculpture electric discharge machining, first, the electrode 141 is sent from the inlet 141 (or the outlet 142) to the back of the flow path 14 to be formed. After digging to a predetermined depth, the flow path 14 communicating from the inlet 141 to the outlet 142 is then formed by similarly carving from the outlet 142 (or the inlet 141). The electrode used has a shape along the flow path 14. A voltage is applied between the electrode and the workpiece to cause discharge, and the flow path 14 is formed by transferring the electrode shape to the workpiece while melting the workpiece with heat during discharge.

As described above, the altered layer is formed on the electric discharge machined surface. Since this deteriorated layer has a high carbon content and is harder than the base material, it is easy to break, and thus includes many fine cracks. Such cracks may deteriorate the metal fatigue characteristics or increase the pressure loss due to the resistance of the gas flowing through the flow path 14. For this reason, the wet polishing process (chemical polishing process) which removes the deteriorated layer by electric discharge machining is performed by immersing the impeller 10 in the polishing liquid 23 of the wet polishing apparatus 20 for a predetermined time. In this wet polishing process, the drive unit 25 causes the impeller 10 to rotate forward R + (FIG. 1) in the same direction as in use.
In this wet polishing process, the altered layer is removed by dissolving the surface of the electric discharge machined surface from the surface layer to a predetermined depth by an oxidation-reduction reaction with the components of the polishing liquid 23. Along with this oxidation-reduction reaction, hydrogen gas is generated in the polishing liquid 23.

The present embodiment is characterized in that the impeller 10 immersed in the polishing liquid 23 is rotated.
By doing so, a flow of the polishing liquid 23 (polishing liquid flow) along the flow path 14 is generated in the flow path 14 of the impeller 10. That is, when the impeller 10 is rotated forward, the polishing liquid 23 is sucked into the flow path 14 from the inlet 141, and the polishing liquid 23 in the flow path 14 is pushed out toward the outlet 142, thereby along the flow path 14. As a result, a polishing liquid flow is generated. The energy of the polishing liquid flow prevents hydrogen gas from staying along the inner wall (polishing surface) of the flow path 14. Therefore, since the polishing liquid 23 can be uniformly brought into contact with the entire inner wall of the flow path 14, the inner wall of the flow path 14 is smoothed without causing the swell W as shown in FIG. Further, the vibration accompanying the rotation of the impeller 10 reaches the polishing surface, and this vibration promotes the separation of hydrogen gas from the polishing surface.

  The rotation speed of the impeller 10 is preferably set to such an extent that a sufficient flow rate is obtained for the polishing liquid flow in the flow path 14 and does not cause turbulent flow in the flow path 14, for example, 8 to 30 rpm. This is because the effect of rotating the impeller 10 cannot be sufficiently obtained when the speed of the polishing liquid flow becomes slow due to the influence of the turbulent flow.

  After the above-described wet polishing step, the outer shape is finished, for example, by machining, if necessary. Thus, the impeller 10 is completed.

  According to the present embodiment, since the impeller 10 is rotated in the wet polishing process, the generation of the undulation W due to the hydrogen gas can be avoided or suppressed, so that the inner wall of the flow path 14 can be smoothed. Thereby, since the resistance of the inner wall with respect to the gas which flows through the flow path 14 becomes small, the centrifugal rotator using the impeller 10 can reduce pressure loss.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. In the description after the second embodiment, the same components as those already described are denoted by the same reference numerals, and the description thereof is omitted or simplified.
Also in the second embodiment, as in the first embodiment, the wet polishing apparatus 20 removes the deteriorated layer due to the electric discharge machining surface while rotating the impeller 10. At this time, the rotational speed of the impeller 10 is changed. This is different from the first embodiment.
The rotation of the impeller 10 is alternately switched between a positive rotation in the same direction as the rotation during the operation of the centrifugal rotator and a negative rotation in the opposite direction. For example, as shown in FIG. 4, the number of rotations is changed between 15 rpm during positive rotation and −15 rpm during negative rotation. The rotation direction is switched by a control unit (not shown) that controls the drive unit 25.

In the present embodiment, in order to further improve the performance of the centrifugal rotator satisfied by the first embodiment described above, the difference (unevenness) in the polishing amount described below is reduced.
That is, when the polishing is performed by the wet polishing apparatus 20 with only the forward rotation (R + in FIG. 5) without changing the direction of rotation, the polishing amount is applied to the inner wall of each flow path 14 as shown in FIG. Difference (unevenness) may occur. When the impeller 10 rotates forward, the flow rate of the polishing liquid flow from the inner peripheral side to the outer peripheral side in the flow path 14 is concave toward the adjacent flow path 14 (not shown) at the center of the flow path 14. The concave side 143 that is recessed is faster than the opposing convex side 144, so the concave side 143 is more easily polished than the convex side 144. Therefore, the amount of polishing on the concave side 143 is large, and the amount of polishing on the convex side 144 is small. In this embodiment, the direction of rotation of the impeller 10 is switched in order to reduce such unevenness in the polishing amount of the inner wall of the flow path 14.

  When the impeller 10 is rotated in the direction opposite to the positive rotation R + (negative rotation R−), the flow rate of the polishing liquid 23 on the concave side 143 becomes slower than that on the positive rotation, so that the polishing amount on the concave side 143 is positive. Less than during rotation. In this way, the flow in the flow path 14 is changed by switching the direction of rotation, and the amount of polishing in each part in the flow path 14 is changed accordingly, so that the concave side 143 is intensively polished. Is avoided. As a result, unevenness in the polishing amount of the inner wall of the flow path 14 can be reduced.

The frequency (time) for switching the direction of rotation is preferably set to a sufficiently short time so as not to cause uneven polishing. For example, if the total polishing time for immersing the impeller 10 in the polishing liquid 23 is 2 to 3 hours, the time is set to 30 seconds to 15 minutes, which is sufficiently shorter than this time. FIG. 4 shows an example in which the polishing is started from the positive rotation. However, the polishing may be started from the negative rotation and may be in the order of the negative rotation, the positive rotation, and the negative rotation.
Further, in the present embodiment, the example of the same 5 minutes is used for the positive rotation time and the negative rotation time, but the positive rotation time and the negative rotation time may be different. Furthermore, repeated multiple forward rotations may be performed at different times. The same applies to the negative rotation.
As for the rotational speed of the impeller 10, positive rotation and negative rotation may be performed at different rotational speeds (absolute values), and repeated multiple forward rotations may be performed at different rotational speeds. The same applies to the negative rotation.
The frequency of switching the rotation direction, the order of the rotation direction, the rotation time, and the number of rotations described above also apply to the following embodiments.

  According to this embodiment, in addition to the effect of the first embodiment in which the inner wall of the flow channel 14 can be smoothed, the unevenness of the polishing amount of the inner wall of the flow channel 14 can be reduced by switching the direction of rotation. Thereby, since the shape precision calculated | required by the flow path 14 of the impeller 10 is securable at a higher level, the predetermined performance of a centrifugal rotator can be improved.

As a modification of the second embodiment, as shown in the timing chart of FIG. 6, non-rotation for stopping the rotation of the impeller 10 can be inserted between the positive rotation and the negative rotation. By doing so, the degree of change (time change rate) of the flow rate of the polishing fluid flow when switching from forward rotation or negative rotation to non-rotation is directly compared to switching directly from positive rotation to negative rotation (or vice versa). Can be small. Thereby, since the site | part which is easy to grind | polish according to the direction of rotation can be moved gradually, the nonuniformity of grinding | polishing amount can be reduced effectively.
However, according to the present invention, after the rotation is switched in the order of the positive rotation, the non-rotation, and the negative rotation, the positive rotation is permitted without interposing the non-rotation. That is, in the present invention, the order of positive rotation, non-rotation, and negative rotation is arbitrary. Therefore, for example, non-rotation may be inserted after positive rotation, but non-rotation may be inserted only once every several times after negative rotation. The non-rotation time is also arbitrarily determined.

The above 2nd Embodiment was shown as an example which changes the rotation speed of the impeller 10 to the last. That is, if the rotation speed of the impeller 10 is changed as in the second embodiment (positive rotation, negative rotation) and the third embodiment (positive rotation, negative rotation, no rotation), the polishing liquid 23 in the flow path 14 is changed. As a result, the unevenness of the polishing amount is less likely to occur, so that a common effect of contributing to securing the shape accuracy can be obtained.
As a mode of changing the rotation speed of the impeller 10, the direction of the rotation can be switched in the order of positive rotation, no rotation, and positive rotation, or can be switched in the order of negative rotation, no rotation, and negative rotation.
In addition, according to the second embodiment, the example in which the rotation speed of the impeller 10 is made constant at both the positive rotation time and the negative rotation time is shown, but not limited thereto, as shown in FIGS. 8A and 8B, The present invention allows the rotational speed to be continuously changed or the rotational speed to be changed stepwise as shown in FIG.

[Third Embodiment]
Next, as a third embodiment of the present invention, a wet polishing apparatus 30 capable of rotating a suspended impeller 10 is shown.
As shown in FIG. 8, the wet polishing apparatus 30 includes a polishing liquid tank 24, a casing 31 that surrounds the polishing liquid tank 24, and a turntable 32 that is rotatably provided on the upper surface of the casing 31. The illustration of the liquid inlet 241 and the liquid outlet 242 of the polishing liquid tank 24 is omitted. The same applies to the apparatus shown in FIGS.
At the center of rotation of the turntable 32, a rotary shaft 33 that is assembled from the cover 12 side into the shaft hole 110 of the impeller 10 and connected to the drive unit 25 is provided. The impeller 10 is suspended by the turntable 32 so as to be rotatable with the cover 12 facing up and the disk 11 facing down. The suspended impeller 10 is entirely immersed in the polishing liquid 23.

Also in this embodiment, wet polishing is performed using the wet polishing apparatus 30 while rotating the impeller 10. Even if the impeller 10 is suspended as in the present embodiment, the impeller 10 is polished in the flow path 14 by the rotation of the impeller 10 as in the first and second embodiments where the impeller 10 is mounted on the installation base 21 (FIG. 3). Since the liquid flow is generated, the polished surface can be smoothed.
Also in this embodiment, as described in the second and third embodiments, the unevenness of the polishing amount can be reduced by changing the rotation speed of the impeller 10.
In addition, the attitude | position of the impeller 10 at the time of wet polishing is not restricted to 1st Embodiment (FIG. 3) or 3rd Embodiment (FIG. 8), For example, the rotation axis C (FIG. 2) follows a horizontal direction. The impeller 10 may be supported.

[Fourth Embodiment]
FIG. 9 shows a wet polishing apparatus 35 according to the fourth embodiment of the present invention.
The wet polishing apparatus 35 can remove the deteriorated layer while precessing the impeller 10 supported by the rotating shaft 37.

Since the impeller 10 that performs precession reciprocates in the vertical direction during one rotation (spinning), the polishing liquid flow in the vertical direction and the radial direction in the flow path 14 particularly on the outer peripheral side. Will have speed. Thereby, since the stay of hydrogen gas on the inner wall of the flow path 14 can be prevented more reliably than when the impeller 10 only rotates, the polished surface can be smoothed.
In the present embodiment as well, unevenness in the polishing amount can be reduced by changing the rotational speed of the impeller 10 and changing the flow velocity of each part in the flow path 14. Here, because of the precession, the flow velocity of each part of the inner wall of the flow path 14 gradually changes while the impeller 10 makes one revolution, and thereby the position of the part that is easily polished also gradually changes while making one revolution. Unevenness of polishing amount can be made more difficult to express.

  The mechanism for precessing the impeller 10 is arbitrary, and the impeller 10 may be precessed by shifting the center of gravity of the impeller 10 from the original rotation axis C using the resistance of the polishing liquid 23, or the impeller 10 itself may be moved. You may force precession. Further, the impeller 10 does not necessarily have to be suspended when the impeller 10 is precessed. For example, the impeller 10 pivotally supported from the bottom with the disk 11 facing upward may be precessed.

[Fifth Embodiment]
The present invention also includes removing the altered layer by electrolytic polishing in addition to the chemical polishing shown in the first to fourth embodiments.
Therefore, as a fifth embodiment, an electropolishing apparatus 40 suitable for applying electropolishing to the present invention will be described with reference to FIGS. FIG. 10 shows only one side in the radial direction from the rotation axis C of the electropolishing apparatus 40, but the other side is also configured in the same manner.
The electrolytic polishing apparatus 40 includes an installation table 21 and a rotating shaft 22, a polishing liquid tank 24 in which a polishing liquid 23 is placed, and a conductive rotating structure 400 provided on the installation table 21.
The rotating structure 400 includes a movable conductor 42 that supports a rod-shaped electrode 41 inserted into each flow path 14, and a disk-shaped fixed conductor 43 that is disposed above the movable conductor 42. ing.

The electrode 41 is formed to be curved following the shape of the flow path 14. The electrode 41 is supported in a state where one end side thereof is electrically connected to the movable conductor 42, and has an end portion 41 a inserted from the outlet 142 side of the flow path 14 on the other end side. It is assumed that the electrode 41 is in charge of a predetermined range from the outlet 142 side.
A plurality of movable conductors 42 are erected on the outer periphery of the upper surface of the installation table 21, and rotate in synchronization with the impeller 10 as the installation table 21 rotates.
The fixed conductor 43 is supported on the upper end of the movable conductor 42 via a bearing 44 having an annular conductivity. Therefore, the fixed conductor 43 is electrically connected to the movable conductor 42 via the bearing 44. The fixed conductor 43 is restricted from rotating by being fixed to, for example, an apparatus housing (not shown). A power supply 45 installed outside the apparatus is electrically connected to the fixed conductor 43. Power is supplied to the electrode 41 by the power source 45 through the fixed conductor 43, the bearing 44, and the movable conductor 42.
An insulating plate 46 is interposed between the impeller 10 and the installation base 21. The installation base 21 and the rotating shaft 22 are grounded.

In the present embodiment, by performing the electrolytic polishing process using the above-described electrolytic polishing apparatus 40, the deteriorated layer by electric discharge machining is removed. In this electrolytic polishing step, the electric discharge machining surface is polished by energizing the impeller 10 with a high voltage and the electrode 41 with a lower voltage and dissolving the surface layer of the inner wall of each flow path 14 based on the potential difference.
Also in this step, the impeller 10 is rotated as in the above-described embodiments. At this time, the movable conductor 42 rotates together with the impeller 10 and the installation base 21, but the rotation is not transmitted to the fixed conductor 43 because the bearing 44 is provided. Therefore, power can be supplied to the electrode 41 without moving the power supply 45 with the rotation of the impeller 10.

  In order to electrolytically polish the inlet 141 side of the flow path 14 beyond the range that the electrode 41 is responsible for, an electrode along the curved shape on the inlet 141 side is separately provided. By electropolishing using this electrode and the electrode 41, the entire region in the longitudinal direction of the flow path 14 is polished. Depending on the shape of the flow path 14, one electrode can be inserted into the flow path 14, and only the entire area of the flow path 14 or a portion having a great influence on the performance of the centrifugal rotating machine can be polished.

  Also in this embodiment, since the polishing liquid flow is generated in the flow path 14 by the rotation of the impeller 10, the polishing surface can be smoothed. Also in the present embodiment, as described in the second embodiment, the unevenness of the polishing amount can be reduced by changing the rotation speed of the impeller 10.

  In addition to those described above, the configurations described in the above embodiments can be selected or modified as appropriate to other configurations without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Impeller 11 Disk 12 Cover 13 Blade 14 Flow path 20, 30, 35 Wet polishing apparatus 22, 33, 37 Rotating shaft 23 Polishing liquid 24 Polishing liquid tank 40 Electropolishing apparatus 41 Electrode 42 Movable conductor 43 Fixed conductor 44 Bearing 45 Power supply 91 Line-shaped part 400 Rotating structure R + Positive rotation R- Negative rotation W Waviness

Claims (6)

A flow path forming step for forming the flow path of the impeller of the centrifugal rotating machine by electric discharge machining;
A wet polishing step of wet polishing the inner wall of the flow path by immersing the impeller in a polishing liquid,
In the wet polishing step, the impeller is rotated around its rotational axis.
An impeller manufacturing method for a centrifugal rotating machine. In the wet polishing step,
Changing the rotational speed of the impeller,
The manufacturing method of the impeller of the centrifugal rotary machine of Claim 1. In the wet polishing step,
By alternately switching between positive rotation and negative rotation, the rotation speed of the impeller is changed.
The manufacturing method of the impeller of the centrifugal rotary machine of Claim 2. In the wet polishing step,
Inserting a non-rotation to stop the rotation of the impeller between the positive rotation and the negative rotation,
The manufacturing method of the impeller of the centrifugal rotary machine of Claim 3. In the wet polishing step,
Precess the impeller,
The manufacturing method of the impeller of the centrifugal rotary machine as described in any one of Claim 1 to 4. In the wet polishing step,
An electrode inserted into the flow path;
A movable conductor that supports the electrode and rotates with the impeller;
Electrolytic polishing using a rotating structure provided with a fixed conductor to which power is supplied from the outside,
Electric power supplied to the fixed conductor is supplied to the electrode through the movable conductor.
The manufacturing method of the impeller of the centrifugal rotary machine as described in any one of Claim 1 to 5.

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