JP2019120615A - Ultrasonic flaw detection device - Google Patents

Abstract

To provide a more accurate ultrasonic flaw detection device.SOLUTION: The ultrasonic flaw detection device comprises: a frame disposed on one axial side of a disk; a transducer which is supported by the frame and irradiates an ultrasonic wave toward the disk; a drive roller rolling in the circumferential direction on the axis direction-one side of the surface of the disc; and a motor rotating the drive roller, the drive roller includes a roller body rotatable around the radially extending rotation axis, a pair of roller holding parts supporting the roller body from the circumferential direction- both sides, a pair of elastic members connecting a pair of the roller holding parts and the frame to each other, and magnetic force generation parts provided one for each of the pair of the rollers.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an ultrasonic flaw detector.

  The steam turbine includes a rotor rotating about an axis, a plurality of moving blades attached to the rotor, a casing that covers the rotor and the moving blades from the outside, and a plurality of stationary blades attached to the inner surface of the casing. There is. The high temperature and high pressure steam flows in from one side in the axial direction, energy is added to the moving blades, and the rotating shaft rotates. A generator connected to the steam turbine is driven by the rotational energy.

  The rotor has a plurality of disk-shaped disks arranged axially. The blades are embedded in blade grooves formed in these disks. As a shape of the wing groove, there is known a T-route type having a T-shaped cross section, and a Christmas tree type having an uneven cross section. When the rotor rotates, centrifugal force acts on the blade roots of the moving blades. The centrifugal force generates stress in the blade groove supporting the blade root. In addition, the rotor is exposed to the high temperature of the steam. Due to these factors, stress corrosion cracking (SCC) may occur around the blade groove of the disk. In the case of a T-routed blade, a crack is particularly likely to occur at the corner of the blade groove.

  Ultrasonic flaw inspection is known as a nondestructive inspection technique for inspecting a crack state of a moving blade. Patent Document 1 describes an apparatus using a phased array flaw detection method with a plurality of probes. Patent Document 2 describes an apparatus for inspecting a rotor using a position monitoring probe and a flaw detection probe.

  The apparatuses described in Patent Document 1 and Patent Document 2 all assume that an operator manually moves along the disc surface. For this reason, depending on the degree of skill of the worker, etc., the inspection result may vary. Therefore, in recent years, a self-propelled inspection apparatus described in Patent Document 3 has also been proposed. This device is self-propelled in the circumferential direction while being attracted to the outer peripheral surface of the rotor by magnetic wheels. On the way, a phased array flaw inspection is performed. However, since the device described in Patent Document 3 self-propelled along the outer peripheral surface of the rotor, when the outer peripheral surface is provided with irregularities, the followability of the device is impaired, and the device is practically used. I can not stand

  In order to solve such a problem, there is considered a method in which the device is self-propelled in the circumferential direction in a state of being adsorbed to the disk surface. Specifically, there is a configuration in which the disk surface can be moved in the circumferential direction by providing a magnet and a drive wheel.

JP, 2009-244079, A JP, 2013-068425, A JP, 2014-163805, A

  However, in the above configuration, an inner ring difference occurs between the radially inner end edge and the radially outer end edge of the drive wheel. Due to this inner ring difference, a force to move straight ahead acts on the drive wheels. That is, movement of the device in the circumferential direction may be hindered. In particular, when the radius of the disk is relatively small, the curve radius of the travel path of the device is small, which is susceptible to the inner ring difference, which may cause difficulty in causing the device to follow the curve. Thereby, there is a possibility that the accuracy of flaw detection inspection may be lost.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a more accurate ultrasonic flaw detection apparatus.

  According to a first aspect of the present invention, there is provided an ultrasonic flaw detection apparatus for inspecting a disk of a disk-shaped steam turbine centered on an axis, the frame being disposed on one side in the axial direction of the disk; A probe supported by a frame and irradiating ultrasonic waves toward the disc, a drive roller rolling in a circumferential direction with respect to the axis on the surface of the disc on one side in the axial direction, and rotating the drive roller A motor, the drive roller includes a roller main body rotatable about a rotational axis extending in a radial direction with respect to the axis, a pair of roller holding portions supporting the roller main body from both sides in the circumferential direction with respect to the axis; It has a pair of elastic members connecting a pair of roller holding portions and the frame, and a magnetic force generating portion provided at least in the pair of roller holding portions.

  According to this configuration, since the magnetic force generating unit for attracting the device to the disk is provided in the roller holding unit, it is not necessary to separately provide a magnet or the like in the roller main body. As a result, the width of the roller body (the dimension in the radial direction with respect to the axis of the disk) can be reduced. That is, the contact area between the roller body and the disk surface can be kept small. As a result, the inner ring difference generated in the roller main body can be reduced, and the possibility that the circumferential movement of the device is hindered can be reduced. Furthermore, since the roller holding portion and the frame are connected by the elastic member, the distance between the probe provided on the frame and the disk surface can be kept constant. In other words, inspection can be performed without strictly adjusting the distance between the probe and the disc surface.

  According to the second aspect of the present invention, the end face on the outer peripheral side of the roller main body may gradually decrease in size in the direction of the rotation axis as it goes from the radially inner side to the outer side with respect to the rotation axis.

  According to this configuration, as the end face on the outer peripheral side of the roller main body goes from the radially inner side to the outer side with respect to the rotation axis, the dimension in the rotation axis direction becomes gradually smaller. Thereby, the contact area between the end face on the outer peripheral side of the roller body and the disk surface can be further reduced. Therefore, the inner ring difference generated in the roller main body can be further reduced, and the possibility of preventing the circumferential movement of the device can be further reduced.

  According to the third aspect of the present invention, the end face on the outer peripheral side of the roller main body moves away from the rotation axis as it goes from the radially inner side to the outer side of the disc in a sectional view including the rotation axis It may extend.

  According to this configuration, the end face on the outer peripheral side of the roller body extends in the direction away from the rotation axis as it goes from the radially inner side to the outer side of the disc. In other words, the dimension in the radial direction with respect to the rotation axis of the roller body becomes smaller toward the radially inner side of the disc. Thereby, the contact area between the end face on the outer peripheral side of the roller body and the disk surface can be further reduced. In addition, a radially inward force of the disc can be applied to the roller body. Thereby, the device can be moved in the circumferential direction more smoothly.

  According to the fourth aspect of the present invention, the roller body may further include an O-ring attached along the end face on the outer peripheral side.

  According to this configuration, since the O ring is provided on the end face on the outer peripheral side of the roller main body, the contact area between the end face on the outer peripheral side of the roller main body and the disc surface can be further reduced. In addition, a relatively large frictional force is generated between the O-ring and the disk surface, which can reduce the possibility of the roller body slipping or slipping.

  According to the fifth aspect of the present invention, it further comprises a guide roller provided radially inward of the axis with respect to the drive roller and rotatable about a sub rotation axis extending parallel to the rotation axis, the sub rotation The dimension of the guide roller in the radial direction with respect to the axis may be smaller than the dimension of the roller body in the radial direction with respect to the rotational axis.

  According to this configuration, the guide roller is provided radially inward of the drive roller with respect to the axial line, and the radial dimension of the guide roller with respect to the sub-rotational axis is smaller than the radial dimension of the drive roller main body. That is, the circumferential length of the guide roller is smaller than the circumferential length of the drive roller. Therefore, a force is applied to the drive roller toward the guide roller (inward in the radial direction with respect to the axis). Thereby, the device can be moved in the circumferential direction more smoothly.

  According to the present invention, it is possible to provide a more accurate ultrasonic flaw detection apparatus.

It is a schematic diagram showing composition of a steam turbine concerning an embodiment of the present invention. It is an explanatory view showing the section of the disk concerning the embodiment of the present invention, and the installation position of installation of a probe. It is a perspective view showing the composition of the ultrasonic flaw detector concerning the embodiment of the present invention. It is a schematic diagram which shows the structure of the ultrasonic flaw detector based on embodiment of this invention. It is a schematic diagram which shows the 1st modification of the ultrasonic flaw detector which concerns on embodiment of this invention. It is a schematic diagram which shows the 2nd modification of the ultrasonic flaw detector which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the steam turbine 1 includes a steam turbine rotor 3 extending along the direction of the axis O, a steam turbine casing 2 (casing) covering the steam turbine rotor 3 from the outer peripheral side, and an axial end of the steam turbine rotor 3 A journal bearing 4 rotatably supporting 3 A around an axis O and a thrust bearing 5 are provided.

  The steam turbine rotor 3 has a plurality of moving blades 25. A plurality of moving blades 25 are arranged at regular intervals in the circumferential direction of the steam turbine rotor 3. Also in the direction of the axis O, the rows of the plurality of moving blades 25 are arranged at a constant interval. The moving blade 25 has a blade body 27 and a moving blade shroud 26 (shroud). The wing body 27 protrudes radially outward from the outer peripheral surface of the steam turbine rotor 3. The wing body 27 has a wing-shaped cross section as viewed in the radial direction. The moving blade shroud 26 is provided at the tip (radially outer end) of the blade body 27.

  The steam turbine casing 2 has a substantially cylindrical shape covering the steam turbine rotor 3 from the outer peripheral side. A steam supply pipe 13A for taking in steam is provided on one side of the steam turbine casing 2 in the direction of the axis O. On the other side of the steam turbine casing 2 in the direction of the axis O, a steam discharge pipe 13B for discharging steam is provided. In the following description, the side on which the steam supply pipe 13A is located as viewed from the steam discharge pipe 13B is referred to as the upstream side, and the side on which the steam discharge pipe 13B is viewed from the steam supply pipe 13A is referred to as the downstream side.

  A plurality of stationary blades 10 are provided along the inner peripheral surface of the steam turbine casing 2. The vane 10 is a blade-like member connected to the inner circumferential surface of the steam turbine casing 2 via a vane pedestal 12. Furthermore, a stator blade shroud 11 is provided at the tip (a radially inner end) of the stator blade 10. Similar to the moving blades 25, a plurality of the stationary blades 10 are arranged along the circumferential direction and the axis O direction on the inner circumferential surface. The moving blades 25 are disposed so as to enter an area between the plurality of adjacent stationary blades 10.

  In the inside of the steam turbine casing 2, a region in which the stationary blades 10 and the moving blades 25 are arranged forms a main flow passage 20 through which the steam S, which is a working fluid, flows. Between the inner peripheral surface of the steam turbine casing 2 and the bucket shroud 26, a recess 14 that is recessed radially outward with respect to the axis O is formed over the entire circumferential direction. The recess 14 forms a cavity that accommodates the tip of the moving blade 25 (moving blade shroud 26). That is, the recess 14 has a sufficiently large volume as compared to the volume of the moving blade shroud 26.

  The steam S is supplied to the steam turbine 1 configured as described above through the upstream steam supply pipe 13A. Thereafter, the steam S passes through the row of the stationary blades 10 and the moving blades 25 as the steam turbine rotor 3 rotates, and is eventually discharged toward the subsequent device (not shown) through the downstream steam discharge pipe 13B.

  The journal bearing 4 supports a load in the radial direction with respect to the axis O. One journal bearing 4 is provided at each end of the steam turbine rotor 3. The thrust bearing 5 supports a load in the direction of the axis O. The thrust bearing 5 is provided only at the upstream end of the steam turbine rotor 3.

  Although not shown in FIG. 1, the steam turbine rotor 3 has a plurality of disk-shaped disks 9 centered on the axis O. The disks 9 are arranged without gaps along the axis O. FIG. 2 is a cross sectional view of the disk 9 in a cross section including the axis O. As shown in FIG. As shown in the figure, at the outer peripheral edge of the disk 9, a wing groove 17 for supporting the moving blade 25 is formed. In this embodiment, although a T route type blade groove is explained to an example, the shape of the blade groove 17 is not limited to this, and it is also possible to apply a Christmas tree type blade groove.

  More specifically, the disk 9 has a disk-like disk main body 9a and a shoulder 9C integrally formed on the outer peripheral side of the disk main body 9a. The radially outward facing surface of the shoulder 9C is an inclined surface 9D extending in a direction intersecting the axis O. On the further radial outside of the inclined surface 9D, a projecting portion 91 that protrudes radially outward is provided. The surface of the disk body 9a facing the direction of the axis O is the disk surface 9A.

  The wing groove 17 has a neck through portion 17A penetrating the above-mentioned shoulder portion 9C in the radial direction with respect to the axis O, and a wing groove main body 17B extending radially inward of the neck through portion 17A. As shown in FIG. 2, the wing groove main body 17B has a rectangular shape in a cross sectional view. The radially inner surface of the wing groove main body 17B is a wing groove bottom surface 17a. The surface radially opposite to the blade groove bottom surface 17a is a blade groove top surface 17b. A pair of surfaces connecting the blade groove top surface 17b and the blade groove bottom surface 17a in the radial direction is respectively made a blade groove side surface 17c.

  The blade root 25 A (radially inner end with respect to the axis O) of the moving blade 25 has a shape corresponding to the blade groove 17. Specifically, the wing root 25A is substantially T-shaped, and has a neck portion 25B and a wing root body 25C. The neck portion 25B is integrally connected to the radially inner side of the wing body 27 having a wing cross-sectional shape. The wing root body 25C has a cross-sectional area larger than that of the neck portion 25B, and is connected to the radially inner side of the neck portion 25B.

  The blade root 25A is rectangular in cross section, and the radially inner surface of the blade root 25A is a blade root bottom surface 25a. The radially outer surface of the blade root 25A is a blade root top surface 25b. A pair of surfaces connecting the blade root top surface 25b and the blade root bottom surface 25a in the radial direction is a blade root side surface 25c. In a state where the moving blade 25 is mounted to the blade groove 17, the blade root bottom surface 25a abuts on the blade groove bottom surface 17a. The blade root top surface 25b abuts on the blade groove top surface 17b. The blade root side surface 25c abuts on the blade groove side surface 17c. The neck portion 25B abuts on the inner surface of the neck penetration portion 17A.

  Subsequently, the configuration of the ultrasonic flaw detection apparatus 100 will be described with reference to FIGS. 3 and 4. The ultrasonic flaw detection apparatus 100 according to the present embodiment detects a crack generated around the wing groove 17 by nondestructive inspection while moving in the circumferential direction with respect to the axis O along the disk surface 9A. As shown in FIG. 3, the ultrasonic flaw detection apparatus 100 according to the present embodiment includes a frame 30, two probes (first probe 22 and second probe 24), and a driving roller 42. And a motor unit 40 (motor). The frame 30 is formed by combining columnar members in a rectangular shape. Specifically, the frame 30 includes a pair of subframes 31A and 31B extending in a substantially radial direction with respect to the axis O, and a pair of connecting frames 33 connecting the subframes 31A and 31B.

  The first probe 22 and the second probe 24 each have a plurality of ultrasonic transducers. The first probe 22 and the second probe 24 oscillate an ultrasonic beam according to an excitation voltage supplied from a controller (not shown). More specifically, as shown in FIG. 2, the first probe 22 is disposed on the disc surface 9A. The second probe 24 is disposed on the inclined surface 9D of the shoulder 9C. For example, when a crack is generated in a corner C formed by the blade groove top surface 17b and the blade groove side surface 17c, ultrasonic beams emitted from the first probe 22 and the second probe 24 are , Reflected by the crack to generate a shape echo. The first probe 22 and the second probe 24 receive this shape echo. Thereby, the occurrence position and size of the crack are identified.

  The first probe 22 is supported by the frame 30 via the first gimbal mechanism 52 and the first holding member 32. The first gimbal mechanism 52 supports the first probe 22 so as to be pivotable about at least two axes including a roll axis and a pitch axis. The first gimbal mechanism 52 is supported by the first holding member 32. The first holding member 32 is movable in the radial direction with respect to the axis O along a guide groove 36G formed in the frame 30 (subframes 31A and 31B).

  The second probe 24 is supported by the frame 30 via the second gimbal mechanism 54 and the second holding member 34. The second gimbal mechanism 54 supports the second probe 24 so as to be pivotable about at least two axes including a roll axis and a pitch axis. The second gimbal mechanism 54 is supported by the second holding member 34. The second holding member 34 is movable in the radial direction with respect to the axis O along a guide groove 36G formed in the frame 30 (subframes 31A and 31B).

  The drive roller 42 and the motor unit 40 are supported by the frame 30. The drive roller 42 rolls in a state of being in contact with the disk surface 9A. The motor unit 40 applies a rotational force to the drive roller 42 by the power supplied from the outside. The detailed configuration of the drive roller 42 will be described later.

  The driven rollers 38 and 39 are attached to the sub frame 31B. The driven roller 38 is rotatably supported by the support mechanism 38C, and rotates with the movement of the apparatus while in contact with the disk surface 9A. The driven roller 39 is rotatably supported by the support mechanism 39C, and rotates in accordance with the movement of the apparatus while in contact with the inclined surface 9D.

  Next, the detailed configuration of the drive roller 42 will be described with reference to FIG. In FIG. 4, the first probe 22, the second probe 24, and the like are not shown in order to simplify the description. Further, illustration of a motor unit 40 for driving the drive roller 42 is also omitted. As shown in the figure, the drive roller 42 includes a roller main body 42A which is a wheel rotatable around the rotation axis Ac, a pair of roller holding portions 42B supporting the roller main body 42A from both sides in the circumferential direction with respect to the axis O It has a pair of elastic members 42C connecting the holding portion 42B and the frame 30, and a pair of magnetic force generating portions 42D respectively provided on the roller holding portion 42B.

  The rotation axis Ac of the roller body 42A extends in the radial direction with respect to the axis O. The roller main body 42A is provided with rod-like roller shafts 42E on both sides in the radial direction of the roller main body 42A with respect to the axis O. The roller holding portion 42B is, for example, a ball bearing, and rotatably supports the roller shafts 42E around the rotation axis Ac. It is also possible to use a bearing device other than a ball bearing as the roller holding portion 42B. The rotational force supplied from the above-described motor unit 40 is transmitted to the roller main body 42A via the roller shaft 42E. Thus, the ultrasonic flaw detection apparatus 100 is movable in the circumferential direction with respect to the axis O.

  The end face (roller end face 42a) on the outer peripheral side of the roller main body 42A has a gradually smaller dimension in the width direction (a dimension in the radial direction with respect to the axis O) as it goes from the radial inner side to the outer side with respect to the rotation axis Ac. Specifically, the roller end surface 42a extends in a direction away from the rotation axis Ac as it goes from the radially inner side to the outer side of the disc 9 in a cross-sectional view including the rotation axis Ac. In other words, the roller end surface 42 a extends radially inward from the rotational axis Ac toward the outside from the radially inward to the outward with respect to the axis O. The relatively large diameter end of the roller end face 42a is a large diameter end 42b, and the relatively small diameter end is a small diameter end 42c.

  Of the roller end face 42a, the area in contact with the disk surface 9A is limited to only the area including the large diameter end edge 42b. That is, at least a part of the small diameter end 42c is not in contact with the disk surface 9A, and the contact area of the roller end surface 42a with the disk surface 9A is kept small.

  The roller holding portion 42B is connected to the frame 30 via the pair of guide members 90 and the elastic member 42C. The guide member 90 has a first guide member 90a attached to the frame side and a second guide member 90b attached to the roller holding portion 42B side. The first guide member 90a is guided displaceably only in the direction of the axis O by the second guide member 90b.

  The elastic member 42C connects the frame 30 and the second guide member 90b. Specifically, a compression coil spring is preferably used as the elastic member 42C. The elastic member 42C exerts an elastic restoring force toward both sides in the axis O direction. That is, the roller body 42A is pressed from the frame 30 side toward the disc surface 9A by the elastic member 42C, so that the outer peripheral surface of the roller body 42A is in contact with the disc surface 9A.

  Specifically, the magnetic force generation unit 42D is a permanent magnet or an electromagnet, and presses the roller main body 42A against the disk surface 9A by generating a magnetic force. One magnetic force generating portion 42D is provided at least on the lower side (the disk surface 9A side) of the roller holding portion 42B. The magnetic force generator 42D is opposed to the disk surface 9A with a slight gap in the direction of the axis O. In addition to the magnetic force generation unit 42D, the frame 30 may be provided with another magnet (permanent magnet or electromagnet).

  Next, operations of the steam turbine 1 and the ultrasonic flaw detection apparatus 100 according to the present embodiment will be described. When the steam turbine 1 is operated, high temperature and high pressure steam is supplied from the external steam supply source (not shown) to the inside (main flow passage 20) of the steam turbine casing 2 through the steam supply pipe 13A. The steam forms a flow that flows from the upstream side toward the downstream side along the main flow passage 20. The steam flow alternately collides with the stationary blades 10 and the moving blades 25 to apply rotational force to the steam turbine rotor 3 via the moving blades 25. The rotation of the steam turbine rotor 3 is taken out from the shaft end to drive an external device such as a generator (not shown).

  Here, in the steam turbine 1 in operation, with the rotation of the steam turbine rotor 3, a centrifugal force directed radially outward of the axis O is applied to the moving blades 25. By repeating the operation and stop of the steam turbine 1 over a long period, stress corrosion cracking (SCC) may occur in the blade groove 17. In the case of the T-route type moving blade 25, a crack is particularly likely to occur at the corner C of the blade groove 17. Specifically, there is a high possibility that a crack will occur at the corner C formed by the blade groove top surface 17 b and the blade groove side surface 17 c. The ultrasonic flaw detection apparatus 100 according to the present embodiment is used to detect the above-mentioned cracks by irradiating ultrasonic waves from the outside of the disk 9.

  The ultrasonic flaw detection apparatus 100 performs flaw detection while moving in the circumferential direction with respect to the axis O along the outer peripheral side of the disc surface 9A, as shown in FIG. 3 or 4. When a crack is generated at a corner C or the like of the wing groove 17, ultrasonic beams emitted from the first probe 22 and the second probe 24 are reflected by the crack to generate a shape echo. . The first probe 22 and the second probe 24 receive this shape echo. Thereby, the occurrence position and size of the crack are identified.

  As described above, according to the configuration according to the present embodiment, the roller holding portion 42B is provided with the magnetic force generating portion 42D for causing the device to be adsorbed to the disk surface 9A. There is no need to separately provide etc. As a result, the width of the roller body 42A (the dimension in the radial direction with respect to the axis of the disk 9) can be reduced. That is, the contact area between the roller body 42A and the disk surface 9A can be reduced. As a result, the inner ring difference generated in the roller main body 42A can be reduced, and the possibility of the movement of the device in the circumferential direction being prevented can be reduced. Therefore, the ultrasonic flaw detection apparatus 100 with higher accuracy can be provided.

  Furthermore, since the roller holding portion 42B and the frame are connected by the elastic member 42C, the distance between the probe provided on the frame and the disk surface 9A can be kept constant. In other words, inspection can be performed without strictly adjusting the distance between the probe and the disk surface 9A.

  In addition, according to the above configuration, as the end face (roller end face 42a) on the outer peripheral side of the roller body 42A goes from the radially inner side to the outer side with respect to the rotation axis Ac, the dimension in the rotation axis Ac direction gradually becomes smaller There is. Thereby, the contact area between the end face on the outer peripheral side of the roller main body 42A and the disk surface 9A can be further reduced. Therefore, the inner ring difference generated in the roller main body 42A is further reduced, and the possibility that the circumferential movement of the device is hindered can be further reduced.

  Furthermore, according to the above configuration, the end surface (roller end surface 42a) on the outer peripheral side of the roller main body 42A extends in the direction away from the rotation axis Ac as it goes from the radially inner side to the outer side of the disc 9. In other words, the dimension in the radial direction with respect to the rotation axis Ac of the roller main body 42A becomes smaller as it goes inward in the radial direction of the disc 9. Thereby, the contact area between the end face on the outer peripheral side of the roller main body 42A and the disk surface 9A can be further reduced. In addition, the force directed radially inward of the disk 9 can be applied to the roller body 42A. Thereby, the device can be moved in the circumferential direction more smoothly.

  On the other hand, in the configuration in which the entire roller end face 42a contacts the disk surface 9A, a slight inner ring difference occurs between the radially inner end of the roller end 42a and the radially outer end. This inner ring difference may prevent the circumferential movement of the device. In particular, when the radius of the disk 9 is relatively small, the curve radius of the travel path of the device becomes small, so it is easily affected by the inner ring difference, which may cause difficulty in causing the device to follow the curve. Thereby, there is a possibility that the accuracy of flaw detection inspection may be lost. However, according to the configuration according to the present embodiment, such a possibility can be reduced.

  The first embodiment of the present invention has been described above. Note that various changes and modifications can be made to the above-described configuration without departing from the scope of the present invention. For example, in the above embodiment, an example is described in which the roller end surface 42a extends in a direction away from the rotation axis Ac as it goes from the radially inner side to the outer side of the disc 9 in a sectional view including the rotation axis Ac. However, the shape of the roller end surface 42a is not limited to the above. As another example (first modification), as shown in FIG. 5, the width dimension (dimension in the direction of the rotation axis Ac) of the roller end surface 42 a becomes the rotation axis Ac as the roller end surface 42 a goes from the inside to the outside in the radial direction of the rotation axis Ac. It is also possible to adopt a shape that is reduced equally from both sides of the direction. That is, in the example of FIG. 5, the roller end surface 42a has a triangular shape in a cross-sectional view including the rotation axis Ac. Even with such a configuration, the contact area between the outer peripheral end face of the roller main body 42A and the disk surface 9A can be further reduced. Therefore, the inner ring difference generated in the roller main body 42A is reduced, and the possibility that the circumferential movement of the device is hindered can be further reduced.

  As a further modification (second modification), as shown in FIG. 6, it is also possible to attach an O-ring 60 to the roller end surface 42a. The roller end surface 42 a is formed with a concave groove to which the O-ring 60 can be attached. As the O-ring 60, an annular member made of silicone rubber or the like is preferably used. With such a configuration, the same function and effect as described above can be obtained.

100 ... ultrasonic flaw detection apparatus 1 ... steam turbine 2 ... steam turbine casing 3 ... steam turbine rotor 4 ... journal bearing 5 ... thrust bearing 9 ... disk 10 ... stator blade 11 ... stator blade shroud 12 ... stator blade base 17 ... blade groove 20 ... main flow path 22 ... first probe 24 ... second probe 25 ... moving blade 26 ... moving blade shroud 27 ... wing body 30 ... frame 32 ... first holding member 33 ... connecting frame 34 ... second holding member 40 ... Motor unit 42 ... Drive roller 52 ... First gimbal mechanism 54 ... Second gimbal mechanism 60 ... O-ring 90 ... Guide member 91 ... Projection 13A ... Steam supply pipe 13B ... Steam discharge pipe 17A ... Neck penetration part 17a ... Wing groove Bottom surface 17B: Wing groove main body 17b: Wing groove top surface 17c: Wing groove side surface 25A: wing root 25a: wing root bottom surface 25B: neck portion 25b: wing root top surface 25C: wing root body 25c ... Root side 31A, 31B ... Sub-frame 36G ... Guide groove 38, 39 ... Followed roller 38C, 39C ... Support mechanism 3A ... Shaft end 42A ... Roller body 42a ... Roller end face 42b ... Large diameter end edge 42C ... Elastic member 42c ... Small diameter end Edge 42D: Magnetic force generation part 42E: Roller shaft 90a: First guide member 90b: Second guide member 9a: Disc main body 9A: Disc surface 9C: Shoulder 9D: Inclined surface Ac: Rotational axis C: Corner part O: Axis

Claims (5)

An ultrasonic flaw detector for inspecting a disk of a disk-shaped steam turbine centered on an axis, comprising:
A frame disposed on one side in the axial direction of the disc;
A probe supported by the frame and irradiating ultrasonic waves toward the disc, a drive roller rolling in a circumferential direction with respect to the axis on the surface of the disc on one side in the axial direction, and rotating the drive roller Motor, and
Equipped with
The drive roller is
A roller body rotatable about an axis of rotation extending radially with respect to the axis;
A pair of roller holding portions for supporting the roller body from both sides in the circumferential direction with respect to the axis;
A pair of elastic members connecting the pair of roller holding portions and the frame;
A magnetic force generation unit provided in each of the pair of roller holding units;
Ultrasonic flaw detection apparatus having.   The ultrasonic flaw detection apparatus according to claim 1, wherein the dimension of the end face on the outer peripheral side of the roller body gradually decreases in the direction of the rotation axis from the radially inner side to the outer side with respect to the rotation axis.   The end face on the outer peripheral side of the roller body according to claim 1 or 2 extends in a direction away from the rotation axis as it goes from the radially inner side to the outer side of the disc in a sectional view including the rotation axis. Ultrasonic flaw detector.   The ultrasonic flaw detector according to claim 1, wherein the roller body further comprises an O-ring attached along an end face on the outer peripheral side.   A guide roller is provided radially inward of the drive roller relative to the axis and rotatable about an auxiliary rotation axis extending parallel to the rotation axis, and the dimension of the guide roller in the radial direction with respect to the auxiliary rotation axis is The ultrasonic flaw detector according to any one of claims 1 to 4, which is smaller than the dimension of the roller body in the radial direction with respect to the rotation axis.

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