JP5737992B2 - Ultrasonic flaw detector - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection apparatus that detects flaws in a structure with ultrasonic waves.

  Ultrasonic flaw detection is a technique for detecting the soundness of structures using ultrasonic waves. For example, Patent Document 1 describes the use of ultrasonic flaw detection for inspection of high-temperature components of a steam turbine.

JP 2004-279181 A

  In ultrasonic flaw detection, a probe that transmits ultrasonic waves is attached to a support body called a shoe, and ultrasonic waves are introduced into an inspection object. At this time, a liquid contact medium is interposed between the shoe and the inspection object. The ultrasonic flaw detection apparatus described in Patent Document 1 supplies the contact medium from the outside of the shoe, but there is a problem that the apparatus becomes complicated. For this reason, there is a method of performing ultrasonic flaw detection by bringing a shoe into contact with an inspection object in a state where a contact medium is applied to the surface of the inspection object. However, since the ultrasonic flaw detector described in Patent Document 1 has no gap between the portion of the shoe through which the ultrasonic waves pass and the inspection target, the surface of the inspection target is applied to the inspection target. There is a possibility that the contact medium does not enter the gap and the contact medium is not sufficiently interposed in the gap. Further, the movement of the shoe may reduce the contact medium interposed in the gap, and the contact medium may not be sufficiently interposed in the gap.

  The present invention provides an ultrasonic flaw detector capable of reliably propagating ultrasonic waves between a support and an inspection object by reliably interposing a contact medium between the support to which the probe is attached and the inspection object. The purpose is to do.

In order to solve the above-described problems and achieve the object, the present invention adjusts an angle at which the ultrasonic wave is incident on the inspection object and a probe that transmits the ultrasonic wave toward the inspection object. An ultrasonic flaw detector, comprising: a support body; and a gap forming means that is provided on the inspection object side of the support body and maintains a constant interval between the inspection object and the support body. is there. The bottom surface of the support is a curved surface along the outer peripheral surface of the inspection object. The gap forming means includes an outer cylinder attached to the support and a ball rotatably held on the opposite side of the outer cylinder from the support. The outer cylinder protrudes from the support toward the inspection object, so that the support is moved between the support and the inspection object when the support moves on the surface of the inspection object. A gap for allowing the contact medium around the body to flow into a position where the probe and the inspection object face each other is formed.

  In this ultrasonic flaw detection apparatus, the gap between the support to which the probe is attached and the inspection object is always kept constant by the gap forming means. For this reason, even if the ultrasonic flaw detector is moved, the contact medium can be surely introduced into the gap, so that the contact medium is surely interposed between the support and the inspection object, so that the support and the inspection object are interposed. Ultrasonic waves can be reliably transmitted between the two. Since this ultrasonic flaw detector can reliably introduce the contact medium applied to the surface to be inspected into the gap, means for supplying the contact medium from the outside is unnecessary. For this reason, in this ultrasonic flaw detector, the inspection object has a complicated shape, or there is a narrow portion in the inspection object, so that it is difficult to handle the contact medium supply means, and the supply means can be used. There is also an advantage that ultrasonic flaw detection can be performed even when it is difficult.

  In this invention, it is preferable that the said support body has a pressing force provision means to generate the force which goes to the said test object. In this way, since the pressing force applying means presses the support against the inspection object, variations in pressing force can be reduced. As a result, the gap between the support and the inspection object can be kept more constant, so that the contact medium can be more reliably held in the gap.

  In this invention, it is preferable that the said pressing force provision means is a magnet attached to the said test object side of the said support body. As described above, since the support is pressed against the inspection target using magnetic force, it is not necessary to press the support against the inspection target when the inspection target is a magnetic body.

  In the present invention, the gap forming means may include an outer cylinder attached to the support, and a ball that generates a magnetic force and is rotatably held on the opposite side of the outer cylinder from the support. preferable. As described above, since the support is attracted to the inspection target using the magnetic force, it is not necessary to press the support against the inspection target when the inspection target is a magnetic body.

  In the present invention, a rotary encoder that moves together with the support and measures the moving distance of the ultrasonic flaw detector, and an outer peripheral portion that is attached to an input shaft of the rotary encoder and that generates a magnetic force contacts the inspection object. And a wheel. With such a structure, even when the contact medium is applied to the surface of the inspection object, slippage between the wheel and the inspection object can be reduced. As a result, the rotary encoder can reduce the measurement error of the moving distance of the ultrasonic flaw detector.

  The present invention provides an ultrasonic flaw detector capable of reliably propagating ultrasonic waves between a support and an inspection object by reliably interposing a contact medium between the support to which the probe is attached and the inspection object. can do.

FIG. 1 is a schematic view showing an ultrasonic flaw detector according to Embodiment 1. As shown in FIG. FIG. 2 is a plan view showing a state in which the ultrasonic flaw detector according to Embodiment 1 is viewed from the bottom. FIG. 3 is a cross-sectional view of the ball plunger. FIG. 4 is a cross-sectional view of the ball plunger. FIG. 5 is a view showing a modification of the gap forming means. FIG. 6 is a schematic diagram showing an ultrasonic flaw detector according to the second embodiment. FIG. 7 is a plan view showing a state in which the ultrasonic flaw detector according to Embodiment 2 is viewed from the bottom. FIG. 8 is an explanatory diagram illustrating an ultrasonic flaw detector according to the third embodiment. FIG. 9 is an explanatory diagram illustrating an ultrasonic flaw detector according to the third embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

(Embodiment 1)
FIG. 1 is a schematic view showing an ultrasonic flaw detector according to Embodiment 1. As shown in FIG. FIG. 2 is a plan view showing a state in which the ultrasonic flaw detector according to Embodiment 1 is viewed from the bottom. The ultrasonic flaw detector 1 detects a flaw or the like in the inspection target T by transmitting the ultrasonic wave inside the inspection target T and receiving the ultrasonic wave reflected and returned inside the inspection target T. It is. The inspection target T of the ultrasonic flaw detector 1 is, for example, a pipe or the like included in a power plant or a chemical plant. In the present embodiment, the inspection target T is piping. The ultrasonic flaw detector 1 transmits ultrasonic waves from a predetermined position in the circumferential direction of the inspection target T and receives reflected ultrasonic waves. The ultrasonic flaw detector 1 moves in the circumferential direction of the inspection target T, and repeats the transmission and reception of ultrasonic waves at different positions in the circumferential direction, and the like, etc. Is detected.

  The ultrasonic flaw detector 1 includes a probe 2, a support 3, and a ball plunger 10 as a gap forming means. The ultrasonic flaw detector 1 further includes a rotary encoder 5 and a wheel 6. In the present embodiment, the ultrasonic flaw detector 1 does not necessarily include the rotary encoder 5 and the wheel 6. The probe 2 transmits an ultrasonic wave toward the inspection target T. The probe 2 is a transducer capable of transmitting and receiving ultrasonic waves. The probe 2 only needs to be able to transmit or receive ultrasonic waves, and is not limited to a transducer.

  The support 3 is a member for adjusting an angle when the ultrasonic wave transmitted from the probe 2 is incident on the inspection target T. In addition, the support 3 introduces ultrasonic waves transmitted from the probe 2 to the inspection target T, and introduces ultrasonic waves from the inspection target T to the probe 2. The support 3 is made of, for example, a resin such as polyetherimide or acrylic, a metal, or the like. As the material of the support 3, an appropriate material is selected and used according to the material of the inspection target T.

  As shown in FIG. 2, the support 3 is a substantially rectangular member in plan view. The probe 2 is attached to the support 3 from the side opposite to the surface (bottom surface) 3B where the support 3 faces the inspection target T. The bottom surface 3B of the support 3 is parallel to the surface TP of the inspection target T. In the present embodiment, since the inspection target T is a pipe, the bottom surface 3B is a curved surface along the outer peripheral surface of the inspection target T. When the ultrasonic flaw detector 1 performs ultrasonic flaw detection, a gap having a predetermined interval is provided between the surface TP of the inspection target T and the bottom surface 3B of the support 3, and a liquid contact called a coplanar is provided in this gap. An ultrasonic wave is transmitted between the probe 2 and the inspection target T through a medium (for example, glycerin or water) Lg. When the size of the gap is S and the outer diameter of the inspection object is D, the curvature radius of the bottom surface 3B is S + D / 2.

  The ball plunger 10 is provided on the inspection object T side of the support body 3 and keeps the distance between the inspection object T and the support body 3 constant. The inspection object T side of the support 3 is a surface facing the inspection object T of the support 3, that is, a bottom surface 3 </ b> B. The ball plunger 10 is provided on the bottom surface 3 </ b> B of the support 3. As for the support 3, the bottom surface 3B also has a rectangular shape in plan view. In this embodiment, the ball plungers 10 are provided at the four corners of the bottom surface 3B. The number of ball plungers 10 is not limited to four, but at least three are necessary.

  3 and 4 are sectional views of the ball plunger. The ball plunger 10 includes an outer cylinder 15, a ball 11, and an elastic body 14. The outer cylinder 15 is a cylindrical container with a bottom and is attached to the support 3. The ball 11 is rotatably held on the side of the outer cylinder 15 opposite to the support 3. In the present embodiment, the ball 11 is supported by the outer cylinder 15 via the ball receiver 12. The ball receiver 12 is a cylindrical and bottomed container, and the ball 11 is rotatably supported on the opening side. The ball receiver 12 has a plurality of sub-balls 13 inside, and these contact with the ball 11. With such a structure, the ball 11 supported by the ball receiver 12 can rotate smoothly while being supported by the ball receiver 12.

  The ball receiver 12 is attached to the opening of the outer cylinder 15 on the side opposite to the support 3. Since the outer diameter of the ball receiver 12 is smaller than the inner diameter of the outer cylinder 15, the ball receiver 12 can reciprocate inside the outer cylinder 15 (in the direction indicated by the arrow N in FIG. 3). The elastic body 14 is provided between the ball 11 and the end portion of the outer cylinder 15 on the support body 3 side, and gives the ball 11 a force toward the opposite side of the support body 3. In the present embodiment, a coil spring is used as the elastic body 14. The elastic body 14 is compressed when the ball 11 moves toward the inside of the outer cylinder 15 and generates a repulsive force. This repulsive force gives the ball 11 a force toward the opposite side of the support 3.

  As shown in FIG. 3, in the ball plunger 10, an end portion (ball-side end portion) 15 </ b> T of the outer cylinder 15 on the ball 11 side protrudes from the bottom surface 3 </ b> B of the support 3. When the ultrasonic flaw detector 1 is moved on the surface TP of the inspection target T, the ultrasonic flaw detector 1 is pressed toward the inspection target T. Then, the ball 11 moves toward the inside of the outer cylinder 15, that is, toward the support body 3. As shown in FIG. 4, the elastic body 14 is compressed by the movement of the ball 11, and the ball side end portion 15 </ b> T of the outer cylinder 15 contacts the surface TP of the inspection target T. At this time, the distance t between the ball side end portion 15T and the bottom surface 3B is the gap between the bottom surface 3B of the support 3 and the inspection target T. In this state, the ultrasonic flaw detector 1 does not approach the inspection target T any more. With such a structure, when the ultrasonic flaw detector 1 is pressed toward the inspection target T, an interval of a distance t is ensured between the bottom surface 3B of the support 3 and the inspection target T.

  The outer cylinder 15 has, for example, a male screw on the outer peripheral surface, and is screwed into a female screw that fits with the male screw provided on the support 3. With such a structure, since the outer cylinder 15 is attached to the support 3, the ball plunger 10 is attached to the support 3. Further, according to such a structure, the amount by which the ball side end portion 15T of the outer cylinder 15 protrudes from the bottom surface 3B of the support body 3 is adjusted by adjusting the screwing amount of the outer cylinder 15 into the support body 3. be able to. In this way, the gap between the bottom surface 3B of the support 3 and the inspection target T can be adjusted.

  As described above, in ultrasonic flaw detection, it is necessary to apply the contact medium Lg to the surface TP of the inspection target T in order to cause the ultrasonic wave from the probe 2 to enter the inspection target T. However, in ultrasonic flaw detection, when the support 3 to which the probe 2 is attached is moved on the surface TP of the inspection target T, the contact medium Lg moves from between the bottom surface 3B of the support 3 and the surface TP of the inspection target T. May be exhaled outside. Then, the contact medium Lg is not interposed between the support 3 and the inspection target T, and the ultrasonic wave may not enter the inspection target T in some cases. That is, ultrasonic waves may not be propagated between the support 3 and the inspection target T.

  In order to avoid this, when the ultrasonic flaw detector 1 is pressed against the inspection target T for movement, the ball plunger 10 has a gap between the bottom surface 3B of the support 3 and the inspection target T as described above. The interval is kept constant (distance t). In this way, even when the ultrasonic flaw detector 1 is pressed against the inspection target T and moved, the gap between the support 3 and the inspection target T is secured, so the contact medium Lg from between the gaps is secured. Is suppressed, and the contact medium Lg stably enters the gap. As a result, the contact medium Lg is interposed in the gap, and stable ultrasonic propagation can be realized between the support 3 and the inspection target T, so that ultrasonic flaw detection can be reliably performed. As a result, the number of times of ultrasonic flaw detection can be reduced.

  Next, the rotary encoder 5 will be described. The rotary encoder 5 moves together with the support 3 and measures the moving distance of the support 3. The rotary encoder 5 is connected to the support 3 of the ultrasonic flaw detector 1 via the arm 7. A bracket 8 is provided on the support 3. The arm 7 is rotatably attached to the bracket 8 by a pin 9. With such a structure, the rotary encoder 5 is connected to the support 3 so as to be rotatable about the position of the pin 9. In addition, the connection structure of the rotary encoder 5 and the support body 3 is not limited to such a structure.

  The rotary encoder 5 has a wheel 6 attached to the input shaft 5S. The wheel 6 has a structure in which the outer peripheral portion 6E generates a magnetic force. For example, an annular magnet (metal magnet, sintered magnet, bonded magnet, etc.) is attached to the outer peripheral portion, or the wheel 6 itself is manufactured with a magnet. By doing in this way, as for the wheel 6, the outer peripheral part 6E generate | occur | produces magnetic force. The outer peripheral portion 6E of the wheel 6 is in contact with the inspection target T. And it rotates according to the movement of the ultrasonic flaw detector 1. The rotary encoder 5 detects the number of rotations of the wheel 6 and measures the moving distance of the ultrasonic flaw detector 1 based on the detection result.

  Since the liquid contact medium Lg adheres to the surface TP of the inspection target T, the wheel 6 may slip, and the accurate moving distance of the ultrasonic flaw detector 1 may not be measured. In the present embodiment, the outer peripheral portion 6E of the wheel 6 attached to the input shaft of the rotary encoder 5 generates a magnetic force. For this reason, when the inspection target T is a magnetic body such as iron, the wheel 6 is attracted to the inspection target T by the magnetic force of the wheel 6, so that the slip of the wheel 6 is suppressed. As a result, it is possible to reduce the number of times that the ultrasonic flaw detection is repeated.

(Modification)
FIG. 5 is a view showing a modification of the gap forming means. The ball plunger 10a as the gap forming means according to this modification is provided with a movement restricting member 14F instead of the elastic body 14 of the ball plunger 10 shown in FIGS. A ball 11M is used. The movement restricting member 14 </ b> F is a member that restricts the magnetic ball 11 </ b> M from moving toward the inside of the outer cylinder 15. The magnetic ball 11M is a magnet, and when the inspection target T is a magnetic material such as iron, it is attracted to the inspection target T by a magnetic force.

  When the inspection target T is a magnetic body, the ultrasonic flaw detection apparatus 1 can be attracted to the inspection target T by the magnetic force of the magnetic ball 11M by using the ultrasonic flaw detection apparatus 1 including the ball plunger 10a. As a result, a constant gap of a distance ta is always formed between the bottom surface 3B of the support 3 of the ultrasonic flaw detector 1 and the surface TP of the inspection target T.

  Since the ultrasonic flaw detector 1 is attracted to the inspection target T by the magnetic ball 11M, it is not necessary to press the ultrasonic flaw detector 1 against the inspection target T when moving the ultrasonic flaw detector 1. When the ultrasonic flaw detector 1 is moved while the ultrasonic flaw detector 1 is attracted to the inspection target T, a gap between the support 3 and the inspection target T is secured, so that the contact medium Lg from between the gaps is secured. Is suppressed, and the contact medium Lg stably enters the gap. As a result, the contact medium Lg is interposed in the gap, and stable incidence of ultrasonic waves is ensured, so that the number of times of ultrasonic flaw detection can be reduced. Further, when performing ultrasonic flaw detection, the gap is kept constant at the distance ta without pressing the ultrasonic flaw detector 1 toward the inspection target T. For this reason, since the influence by the magnitude | size of the said gap | interval can be reduced, an ultrasonic flaw can be performed stably. As a result, stable incidence of ultrasonic waves is ensured, so that the number of times of ultrasonic flaw detection can be reduced.

(Embodiment 2)
FIG. 6 is a schematic diagram showing an ultrasonic flaw detector according to the second embodiment. FIG. 7 is a plan view showing a state in which the ultrasonic flaw detector according to Embodiment 2 is viewed from the bottom. The ultrasonic flaw detector 1a according to the second embodiment is substantially the same as the ultrasonic flaw detector 1 according to the first embodiment, except that the support 3 has a pressing force applying unit that generates a force toward the inspection target T. Different. Other configurations of the ultrasonic flaw detector 1a are the same as those of the ultrasonic flaw detector 1.

  The ultrasonic flaw detector 1a has a magnet 4 as pressing force applying means. A plurality of magnets 4 are attached to the portion where the support 3 faces the inspection target T, more specifically, to the bottom surface 3B side of the support 3. In the present embodiment, as shown in FIG. 7, the support 3 has a plurality (four in the present embodiment) of magnets 4 at positions that do not overlap the probe 2 in plan view. That is, the plurality of magnets 4 are arranged at positions that do not interfere with the ultrasonic waves transmitted from the probe 2. By doing in this way, the influence of refraction by ultrasonic waves passing through different media can be eliminated.

  When the inspection target T is a magnetic body, the ultrasonic flaw detector 1a is attracted to the inspection target T by the magnetic force of the magnet 4 by using the ultrasonic flaw detector 1a. When the ultrasonic flaw detector 1a approaches the inspection target T due to the magnetic force of the magnet 4, the elastic body 14 of the ball plunger 10 contracts as shown in FIG. 4, so that the ball side end portion 15T of the outer cylinder 15 is the inspection target. Contact the surface TP of T. As a result, as shown in FIG. 4, a constant gap of a distance ta is always formed between the bottom surface 3B of the support 3 of the ultrasonic flaw detector 1a and the surface TP of the inspection target T. This gap is formed with the same size without applying a force toward the inspection target T to the ultrasonic flaw detector 1a. For this reason, when performing ultrasonic flaw detection, it is possible to reduce the influence of the change in the gap due to the difference in the pressing force of the operator. As a result, stable incidence of ultrasonic waves is ensured, so that the number of times of ultrasonic flaw detection can be reduced.

  Since the ultrasonic flaw detector 1a is attracted to the inspection target T by the plurality of magnets 4, it is not necessary to press the ultrasonic flaw detector 1a against the inspection target T when moving the ultrasonic flaw detector 1a. When the ultrasonic flaw detector 1a is moved in a state where the ultrasonic flaw detector 1a is attracted to the inspection target T, a gap between the support 3 and the inspection target T is secured, so that the contact medium Lg from between the gaps is secured. Is suppressed, and the contact medium Lg stably enters the gap. As a result, the contact medium Lg is interposed in the gap, and stable incidence of ultrasonic waves is ensured, so that the number of times of ultrasonic flaw detection can be reduced.

  Instead of attaching the magnet 4 to the support 3, the support 3 may be manufactured with a magnet. In this way, since the magnetic force can be increased, the ultrasonic flaw detector 1a can be attracted to the inspection object T more reliably. And it becomes easy to ensure the clearance gap between the support body 3 and the test object T constant.

(Embodiment 3)
8 and 9 are explanatory views showing an ultrasonic flaw detector according to the third embodiment. The ultrasonic flaw detector 1b according to the third embodiment is the same as the ultrasonic flaw detector 1 according to the first embodiment, but further includes a plurality of plungers 30 as pressing force applying means. As shown in FIG. 9, the plunger 30 includes a roller 31, a bracket 32 that rotatably supports the roller 31, a piston rod 33 attached to the bracket 32, and a cylinder 34 in which the piston rod 33 reciprocates. Have The cylinder 34 is filled with, for example, nitrogen gas, and a force in the direction in which the piston rod 33 protrudes from the cylinder 34 (the direction indicated by the arrow U in FIG. 9) is applied to the piston rod 33.

  When performing ultrasonic flaw detection with this ultrasonic flaw detector 1b, the annular guide rail 21 is arranged with a certain distance from the outer periphery of the inspection target T. The guide rail 21 is attached to the surface TP of the inspection target T by a plurality of guide rail support devices 22. The guide rail support device 22 includes a connecting portion 22R connected to the guide rail 21 and a base 22B that fixes the connecting portion 22R to the surface TP of the inspection target T. The pedestal 22B generates an attractive force by, for example, magnetic force or vacuum suction.

  The ultrasonic flaw detector 1b is installed between the guide rail 21 and the inspection target T. At this time, the roller 31 of the plunger 30 is brought into contact with the guide rail 21. The piston rod 33 of the plunger 30 is pushed into the cylinder 34 to some extent. By doing in this way, since the plunger 30 presses the roller 31 against the guide rail 21, the ultrasonic flaw detector 1b is pressed against the inspection target T by the reaction force.

  In this way, even if the operator does not press the ultrasonic flaw detector 1b, there is always a certain size between the bottom surface 3B of the support 3 of the ultrasonic flaw detector 1b and the surface TP of the inspection target T. A gap is formed. For this reason, when performing ultrasonic flaw detection, it is possible to reduce the influence of the change in the gap due to the difference in the pressing force of the operator. As a result, stable incidence of ultrasonic waves is ensured, so that the number of times of ultrasonic flaw detection can be reduced.

  Since the ultrasonic flaw detector 1b is pressed against the inspection target T by the plunger 30 and the guide rail 21, it is not necessary for the operator to press the ultrasonic flaw detector 1b against the inspection target T when moving the ultrasonic flaw detector 1b. . When the ultrasonic flaw detector 1b is moved in a state where the ultrasonic flaw detector 1b is pressed against the inspection target T, a gap between the support 3 and the inspection target T is secured, so that the contact medium Lg from between the gaps is secured. Is suppressed, and the contact medium Lg stably enters the gap. As a result, the contact medium Lg is interposed in the gap, and stable incidence of ultrasonic waves is ensured, so that the number of times of ultrasonic flaw detection can be reduced.

DESCRIPTION OF SYMBOLS 1, 1a, 1b Ultrasonic flaw detector 2 Probe 3 Support body 3B Bottom surface 4 Magnet 5 Rotary encoder 6 Wheel 6E Outer peripheral part 10, 10a Ball plunger 11 Ball 11M Magnetic ball 13 Sub ball 14 Elastic body 14F Movement restricting member 15 Outside Tube 15T Ball side end 21 Guide rail 22 Guide rail support device 30 Plunger

Claims (7)

A probe that transmits ultrasonic waves toward the pipe to be inspected;
A support for adjusting an angle when the ultrasonic wave is incident on the inspection object;
A gap forming means that is provided on the inspection object side of the support and holds a constant distance between the inspection object and the support;
The bottom surface of the support is a curved surface along the outer peripheral surface of the inspection object ,
The gap forming means includes an outer cylinder attached to the support body, and a ball rotatably held on the opposite side of the outer cylinder to the support body,
The outer cylinder protrudes from the support toward the inspection object, so that the support is moved between the support and the inspection object when the support moves on the surface of the inspection object. A gap is formed to allow the contact medium around the body to flow into a position where the probe and the inspection object face each other.
An ultrasonic flaw detector characterized by that.   The ultrasonic flaw detection apparatus according to claim 1, further comprising a pressing force applying unit that generates a force of the support toward the inspection target.   The ultrasonic flaw detector according to claim 2, wherein the pressing force applying means is a magnet attached to the inspection target side of the support. The pressing force applying means is
  An annular guide rail disposed at a certain distance from the outer periphery of the inspection object;
  A plurality of guide rail support devices for attaching the guide rail to the inspection object;
  The ultrasonic flaw detector according to claim 2, further comprising: a plurality of plungers that press the guide rail. The ultrasonic flaw detector according to claim 1, wherein the support is a magnet. The ultrasonic flaw detector according to claim 1, wherein a ball that generates magnetic force is used as the ball. A rotary encoder that moves together with the support to measure a moving distance of the ultrasonic flaw detector;
A wheel that is attached to the input shaft of the rotary encoder and has an outer peripheral portion that generates a magnetic force is in contact with the inspection object;
The ultrasonic flaw detector according to any one of claims 1 to 6 , comprising:

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