JP6197893B2 - Inspection device for detecting cracks in tubular members - Google Patents

Description

The present invention relates to inspection apparatus for discovering cracks in the tubular member fabricated by powder molding or the like.

For example, a magnet 1 used for a rotor of a motor as shown in FIG. 5 is manufactured by magnetizing an outer peripheral portion after being formed into a cylindrical shape by powder molding.
The magnets manufactured in this way are inspected for the total number of cracks before being incorporated into the motor.

  Conventionally, the inspection of the presence or absence of cracks in the magnet is generally carried out by placing the magnet on a sponge soaked in moisture, and if there is a crack portion, the moisture enters the crack portion by osmotic pressure and becomes black. Using the color change, the presence or absence of the color change was confirmed visually.

  However, in the above conventional crack detection method, there is a problem that it is difficult to reliably discriminate with respect to slight scratches and cracks that may develop into cracks and require skill. Although effective for magnets molded by sintering, there is also a problem that it cannot be applied to magnets made of water-repellent materials such as bonded magnets and plastic magnets.

The present invention has been made in view of the above circumstances, and reliably detects cracks or small scratches that can develop into cracks in a cylindrical member, regardless of the material and without skill. It is an object of the present invention to provide an inspection device for detecting a crack in a cylindrical member.

To solve the above problems, a first aspect of the present invention, there is provided an inspection apparatus for finding cracks in the tubular member, is the tubular member therein is formed by a bottom plate and a cylindrical side wall The lower frame body to be mounted, the upper end opening of the side wall having the same shape as the side wall is closed by the top plate, and the pressing ring is fixed to the inner surface of the top plate along the outer periphery, and at the center of the top plate An upper frame body provided with a connection portion for a compressed air supply line, and a connecting pipe with the connection portion at the center of the upper surface are integrally formed, and a large number of compressed air jets are formed on the entire outer peripheral surface. And a columnar member that is formed in the center opening of the cylindrical member and has a flow path that guides the compressed air introduced from the connecting pipe to the jet outlet, and the cylindrical member and the lower frame Between the bottom plate of the body and the tubular member Serial is interposed between the pressing ring of the upper frame member characterized in Rukoto such and an O-ring for sealing airtight between the central opening and the outer peripheral surface of the tubular member is there.

According to the first aspect of the present invention, when the compressed gas is ejected from the gas outlet of the columnar member inserted into the central opening of the cylindrical member toward the cylindrical member, the crack portion is formed in the cylindrical member. If present, the supply flow rate remains at a large value because the compressed gas flows through the crack portion and is discharged to the outer peripheral surface. On the other hand, when there is no crack portion, the supply flow rate becomes extremely small because the compressed air does not flow through the cylindrical member.

As a result, the supply flow rate is measured while maintaining the compressed gas at a predetermined pressure, and the presence or absence of a crack portion can be determined based on the magnitude of the value.
At this time, by setting the pressure of the compressed gas to a value as appropriate, even slight cracks or scratches that may develop into cracks are caused to progress from the cracks or scratches to the cracks by the compressed gas. It becomes possible to discover easily.

  As a result, it is possible to surely find a crack portion generated in the cylindrical member, a small crack that may develop into a crack, or the like regardless of the material and without requiring skill.

  When the compressed gas is ejected from the gas outlet of the columnar member, generally, the applied pressure decreases and the supply flow rate increases until the pipe portion reaches the predetermined pressure, and then the applied pressure is increased to the predetermined pressure. And the supply flow rate decreases.

For this reason , there is a small possibility that a compressed gas is ejected from the gas ejection port and the flow rate of the compressed gas is measured after being held at a predetermined pressure for a certain period of time. It becomes possible to find cracks and the like.

It is a figure for demonstrating one Embodiment of this invention, and is a longitudinal cross-sectional view which shows the state which mounted | wore the inspection apparatus with the magnet. It is a longitudinal cross-sectional view which shows the state which closed the upper frame of FIG. It is a longitudinal cross-sectional view which shows the state which supplied compressed gas inside the magnet of FIG. It is a graph which shows the change of the supply pressure and supply flow rate of the compressed air to the said inspection apparatus. It is a perspective view which shows the shape of a general magnet.

Hereinafter, with reference to FIGS. 1 to 5, a description will be given of an embodiment applying the crack discovery inspection device of a tubular member according to the present invention for cracking the discovery of the cylindrical magnet 1.
As shown in FIGS. 1 to 3, the inspection apparatus is inserted into the magnet 1, the lower frame 2 to which the magnet 1 is attached, the upper frame 3 that closes the upper opening of the lower frame 2, and the magnet 1. The cylindrical member 4 is generally configured.

  The lower frame 2 is formed in a bottomed cylindrical shape by the bottom plate 5 and the side wall 6, and the inner diameter dimension of the side wall 6 is slightly larger than the outer diameter dimension of the magnet 1. On the other hand, the upper frame 3 is composed of a cylindrical side wall 7 having the same diameter as the side wall 6 and a top plate 8 that closes the upper end opening of the side wall 7. A pressing ring 9 is fixed along the.

A connecting portion 10 of a compressed air supply line is provided at the center of the top plate 8.
Further, the cylindrical member 4 is formed so that the outer diameter is such that it can be closely inserted into the central opening of the magnet 1, and a connecting tube 11 with the connecting portion 10 is integrally formed at the center of the upper surface. . The cylindrical member 4 has a large number of compressed air outlets on the entire outer peripheral surface, and a flow path for introducing compressed air introduced from the connecting pipe 11 to the outlet. Is formed.

Next, the crack detection method of the magnet 1 using the said inspection apparatus is demonstrated.
First, as shown in FIG. 1, the O-ring 12 is disposed on the bottom plate 5 of the lower frame 2, and the magnet 1 having the columnar member 4 inserted therein is placed thereon.

  Next, as shown in FIG. 2, the upper frame 2 is put on the upper part of the magnet 1. At this time, an O-ring 12 is also interposed between the upper surface of the magnet 1 and the pressing ring 9 of the upper frame 2. Then, by pressing the upper frame 2 downward, the space between the inner peripheral surface side and the outer peripheral surface side of the magnet 1 is hermetically sealed, and the connection pipe 11 of the columnar member 4 is connected to the connection portion of the upper frame body 2. 10 is connected.

  Next, as shown in FIG. 3, a compressed air supply line 13 is connected to the connecting pipe 10 of the upper frame 2, and a constant pressure (in the present embodiment, inside the cylindrical member 4 is connected via the flow meter 14. 2Mpa) of compressed air is supplied and ejected from the jet outlet on the outer peripheral surface, and at the same time, the flow rate of the compressed air is measured by the flow meter 14.

  The measurement method of the pressure and flow rate at this time will be described in more detail with reference to FIG. 4. In the initial stage of supplying compressed air from the compressed air supply line 13 into the cylindrical member 4, the compressed air is connected to the connecting pipe. 11, the applied pressure decreases until it reaches the connection portion 10 and the cylindrical member 4. Therefore, a fixed time (2.5 seconds in this embodiment) is set as the measurement waiting time.

  Next, the compressed air is filled in these pipes, the applied pressure returns to a predetermined pressure (2 MPa), and the supply flow rate is measured by the flow meter 14 while maintaining the pressure. Incidentally, this measurement time is 0.2 seconds in this embodiment.

  And when a crack part exists in the magnet 1 or when a slight crack or scratch that may develop into a crack develops into a crack due to the pressure of the compressed air (2 MPa), the compressed air is , The supply flow rate measured by the flow meter 14 is still a large value because the gas is discharged from the outer peripheral surface of the magnet 1 through the gap between the side walls 6 and 7 to the outside.

  On the other hand, when there is no crack part in the magnet 1, since there is no compressed air which leaks from the inside of the magnet 1 to the outer peripheral surface side, the supply flow rate gradually decreases.

  Therefore, by setting the determination flow rate in the flow meter 14 in advance, there is a crack part when the supply flow rate exceeds the set value, and there is no crack part when the flow rate drops below the set value. Judgment can be made.

By the way, according to the verification results by the present inventors, the supply flow rate was 300 to 450 L / min in the general good magnet 1, but in the magnet 1 where the crack portion exists, The upper limit was 1144 L / min.
As a result, it was possible to easily and surely determine the presence or absence of cracks by previously setting the flow rate of the compressed air supply flow rate to the flow meter 14 as 500 L / min.

As described above, according to the inspection apparatus for detecting cracks in the magnet 1 having the above-described configuration, the gas outlet of the columnar member 4 inserted into the central opening of the magnet 1 is directed toward the inner peripheral surface of the magnet 1. When the compressed gas is ejected and the magnet 1 has a crack portion, the compressed gas flows through the crack portion and is discharged to the outer peripheral surface, and the supply flow rate becomes a large value. The presence or absence can be determined.

  In addition, by setting the pressure of the compressed gas to an appropriate value, it is possible to detect slight cracks and scratches that may develop into cracks by causing the compressed gas to develop into cracks. . As a result, it is possible to surely find a crack generated in the cylindrical member or a small crack that may develop into a crack regardless of the material and without skill.

  At this time, since the compressed gas is ejected from the gas ejection port of the cylindrical member 4 and the flow rate of the compressed gas is measured after being held at a predetermined pressure for a certain period of time, it develops more accurately into cracks and cracks. It becomes possible to find a small crack or the like that may be.

  In addition, in the said embodiment, although shown only about the case where the crack discovery method of the cylindrical member of this invention was applied to the crack discovery method of the cylindrical magnet 1, this invention is not limited to this, It can be applied to find cracks in various tubular members. In addition, the present invention is not limited to the cylindrical shape such as the magnet 1 and can be used for finding cracks in a rectangular tube-like member.

1 Magnet (tubular member)
12 O-ring 13 Compressed air supply line 14 Flow meter

Claims (1)

An inspection device for finding a crack in a tubular member,
A lower frame which is formed by a bottom plate and a cylindrical side wall and in which the cylindrical member is mounted;
The upper end opening of the side wall having the same shape as the side wall is closed by the top plate, a pressing ring is fixed to the inner surface of the top plate along the outer periphery, and the connection portion of the compressed air supply line at the center of the top plate An upper frame provided with,
A connecting pipe with the connecting portion is integrally formed at the center of the upper surface, and a large number of compressed air outlets are formed on the entire outer peripheral surface, and the compressed air introduced from the connecting pipe is supplied into the outlet. A columnar member that is inserted into the central opening of the cylindrical member and has a flow path that leads to
Between the cylindrical member and the bottom plate of the lower frame and between the cylindrical member and the pressing ring of the upper frame, the central opening and the outer peripheral surface of the cylindrical member tubular member cracks found inspection apparatus according to claim Rukoto such and an O-ring seal airtightly between.

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