JPH07110368A - Magnetostriction measuring method - Google Patents

Abstract

PURPOSE:To measure magnetostriction with higher definition. CONSTITUTION:The method for measuring a magnetostriction comprises the steps of disposing magnetic substance sample 3 in the inner space of a coil 2, supplying a current to the coil 2 to generate an alternating magnetic field, and measuring the magnetostriction generated in the sample 3 by the field. Before generating the field for an actual measurement, an alternating current for aligning the sample 3 and the coil 2 therebetween at an electrically central position is supplied to the coil 2 for a predetermined time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostriction measuring method which enables measurement of particularly small magnetostriction of a magnetic material.

[0002]

2. Description of the Related Art Magnetic materials such as iron and steel are
The acicular domains, which are the smallest magnets, are irregularly arranged and do not exhibit magnetism, but when the magnetic body is placed in a magnetic field, the acicular domains are aligned along the direction of the magnetic field, and Is magnetized to become a magnet. At this time, it is known that magnetostriction occurs in the magnetic body. Therefore, when the magnetic body is placed in an alternating magnetic field, the magnetic body vibrates due to magnetostriction.

Vibration due to magnetostriction of the magnetic material is considered to occur as follows. The magnetization of the magnetic body changes depending on the direction of the magnetic field in which it is placed. Therefore, when the magnetic body is placed in an alternating magnetic field as shown in FIG. 11A, the direction of magnetization of the magnetic body is reversed at a repetition rate twice the repetition frequency of the alternating magnetic field. At the time of reversing the direction of the magnetization, the needle-shaped magnetic domains 101 rotate as shown in FIG. 11B to reverse their magnetic poles.

As can be seen from FIG. 11B, with the reversal of the needle-shaped magnetic domains, the needle-shaped magnetic domains are in the horizontal position and in the vertical position. Therefore, it is considered that the magnetic substance is distorted by these positional changes. Since the rotation of the magnetic domain is caused by the alternating magnetic field, the magnetostriction of the magnetic substance placed in the alternating magnetic field is 2 times the repetition frequency of the alternating magnetic field.
It becomes the vibration distortion based on the double frequency.

Conventionally, the following method has been used as a method for measuring the magnetostriction of this magnetic material. That is, in this method, as shown in FIG. 12, a mirror 102 in which a sample 102 made by flattening and thinning a magnetic material is provided with an inclination is provided.
03, and this sample with a mirror is placed in the internal space of a coil (solenoid coil) 107 wound in a cylindrical shape shown by a dotted line in the figure. Then, an alternating current is passed through the coil 107 to generate an alternating magnetic field (alternating magnetic flux φ), and the sample 1
02 causes magnetostriction.

In this state, the light beam 105 is emitted from the light source 104 to the mirror 103 attached to the sample 102, and the reflected light is received by the light receiving section 106 to measure the magnitude of magnetostrictive vibration. . The measurement principle is shown in FIG.
As shown in, the mirror 103 attached to the magnetic material sample 102.
The fact that the reflected light has a divergence angle θ according to the amount of magnetostriction when the beam 105 is incident on is used.

[0007]

By the way, such vibration due to magnetostriction of the magnetic material causes various noises such as appearing as a humming noise in a motor or a transformer. Therefore, there is a demand for a material having as small a magnetostriction as possible, and its development is in progress. And recently, the amount of magnetostriction is 10 ⁻⁷ per 1 m.
The possibility of birth of materials that are pressed down to around 10 ^-9 m is emerging.

By the way, such a small magnetostriction of the magnetic material must be confirmed by measuring the magnitude of the magnetostriction. For that purpose, it must be possible to measure such a very small magnetostriction. However, in the conventional device, 1
Although it is possible to measure the magnetostriction up to a minimum of about 10 ⁻⁷ m per m, it is impossible to accurately measure a smaller magnetostriction.

The inventor of the present invention has sought out the cause of this and found the following points. The installation position of the magnetic material sample 102 in the coil 107 is such that the electrical center position of the coil 107 in the winding direction coincides with the center (electrical center) position of the sample 102 in the tube axis direction. It must be. This is because when it is not at the electrical center position, the alternating magnetic field causes the sample 3 itself to change its position in the tube axis direction, and only magnetostriction cannot be correctly measured.

Therefore, conventionally, the physical center position of the coil 107 in the winding direction and the physical center position of the magnetic material sample 102 in the magnetostriction direction are matched.

However, when the magnetic material sample 102 has, for example, a polycrystalline structure, the crystals forming the magnetic domains have various sizes, and the sample is placed in a magnetic field to exhibit magnetism. When the magnetic domains are aligned with each other, the electrical center position does not coincide with the physical center position of the sample due to the difference in the size of the magnetic domains. For this reason, even if the physical central position is aligned with dimensional accuracy, the electric central position is not reached.

Further, if there is uneven winding of the wire on the coil 107 side, the physical center position and the electrical center position in the coil winding direction do not match. In the conventional measuring device of FIG. 12, light must be emitted from the outside of the coil 107 to the mirror 103 and the reflected light must be guided to the external light receiving unit 106. Therefore, a gap must be provided in the path of these lights. I have to. Therefore, it is difficult for the physical center position of the coil 107 and the electrical center position to coincide with each other.

An alternating magnetic field for measuring magnetostriction was passed through the coil 107 to generate an alternating magnetic field in a state where the electrical center position of the coil 107 and the magnetic sample 102 were not aligned. In this case, along with the magnetostriction, the sample 102 itself moves (vibrates) so that the electrical center positions of the coil 107 and the magnetic sample 102 coincide with each other. The position movement of the sample 102 stops at the coincidence point of the electrical center position after a predetermined time has elapsed, but the alternating magnetic field at the time of measuring the magnetostriction is relatively large, and it takes a long time before the stop. Takes. For this reason,
In the past, the magnetostriction was measured during the period in which this vibration movement occurred, and accurate and minute magnetostriction could not be measured.

Further, since the conventional measuring device is a device in which a mirror is attached to a sample, the mirror is irradiated with light, and the magnetostriction of the sample is measured from the divergence angle of the reflected light, the following problems occur. There is.

That is, since the conventional strain measuring device using a mirror does not directly measure the magnetostriction itself of the sample, it is a method of indirectly measuring the magnetostriction amount, so that it is predetermined. The small magnetostriction below the value could not be measured accurately.

Further, since the system receives the reflection of light from the mirror attached to the sample, it is difficult to firmly fix the sample. For this reason, for example, when trying to measure the magnetostriction in the flat plane direction of a sample cut into a flat and thin shape, the sample is affected by the magnetostriction in the thickness direction of the sample, causing the sample to laterally shake, etc. Strain measurement is disabled.

In addition, since the mirror is attached to the sample, the magnetostriction generated in the sample is affected by the amount of the attached mirror, which is also a hindrance to accurate measurement of smaller magnetostriction. .

Further, in the case of the conventional example shown in FIG. 12, the mirror 103 to which the sample is attached is irradiated with light from the light source 104 outside the coil 107, and the reflected light is reflected by the coil 1.
Since the light receiving element 106 provided outside 07 needs to receive light, the coil 107 has the sample 1
In the vicinity of 02, a space for guiding the light must be provided without winding the wire. Therefore, the coil 107
The alternating magnetic field generated in the winding direction becomes uneven in the vicinity of the sample 102, and it is difficult to arrange the magnetic characteristic environment in the vicinity of the sample, which is important for accurate measurement of magnetostriction, to be the desired one. Met.

In view of the above points, the present invention arranges a magnetic material sample in the internal space of a solenoid coil, applies an electric current to the coil to generate an alternating magnetic field, and the magnetic field generated in the magnetic material sample by the alternating magnetic field. It is an object of the present invention to provide a method that makes it possible to measure magnetostriction with higher precision in a magnetostriction measuring device that measures strain.

[0020]

In order to solve the above-mentioned problems, in the method according to the present invention, the first coil for magnetic field generation wound in a cylindrical shape corresponds to the reference numerals of the embodiments described later. 2, an alternating signal generator 11 for generating an alternating signal to be supplied to the first coil 2 in order to generate an alternating magnetic field in the inner space, and an inner space of the first coil 2. A sample holding member 30 for disposing the magnetic material sample 3 therein, second coils 4 and 5 for detecting magnetic characteristics in the vicinity of the sample 3, and displacement of the magnetic material sample 3 due to magnetostriction. And a magnetostriction detecting means 6 for determining the magnetic characteristics of the magnetic material sample in the vicinity of the magnetic material sample from the induced voltage output obtained in the second coils 4 and 5 and the output signal of the magnetostrictive detecting means 6. Under the condition of its magnetic properties, In the case of using a magnetostriction measuring device adapted to obtain the relationship with the amount of magnetostriction generated in the sample, before the generation of the alternating magnetic field for the actual measurement, a magnetic magnetic material sample is added to the first coil. First above
It is characterized in that a current is supplied for electrical center alignment between the coil and the coil.

Further, the present invention is notable for its effect when the following magnetostrictive measuring device is targeted. That is, the magnetostriction measuring apparatus uses the first coil 2 for generating a magnetic field wound in a cylindrical shape and the first coil 2 for generating an alternating magnetic field in the internal space of the first coil 2. An alternating signal generator 11 for generating an alternating signal to be supplied to the magnetic material sample 3 and a pair of non-magnetic material plates 31 and 32 for sandwiching and holding the magnetic material sample 3, and the direction of the sandwiched surface of the magnetic material sample 3 is In a state of being coincident with the winding direction of the first coil 2, substantially in the center of the space surrounded by the first coil 2 and in the center of the winding direction of the first coil 2,
A sample holding member 30 for arranging the magnetic material sample 3 and a sample holding member 30 in order to detect magnetic characteristics in the vicinity of the sample 3 are provided around the portion between the pair of non-magnetic material plates 31 and 32 for sandwiching the sample 3. The second coils 4 and 5 fixed to the holding member 30, and the pair of non-magnetic material plates 31 of the sample holding member 30,
End face 3t of the magnetic material sample 3 between 32 or this end face 3t
And an optical displacement meter 6 for detecting the displacement of the end face 3t of the magnetic material sample 3 from the reflected light by irradiating a light beam on the reflection plate attached to the second coil 4, 5. From the output and the output signal of the optical displacement meter 6, the magnetic material sample 3
It is characterized in that the relationship between the magnetic characteristics in the vicinity of and the amount of magnetostriction generated in the magnetic material sample 3 under the magnetic characteristics condition is obtained.

[0022]

According to the method of the present invention having the above-mentioned structure, a predetermined current is supplied to the coil 2 for a predetermined time or longer prior to the actual measurement of the magnetostriction of the magnetic material sample. As a result, the position of the magnetic material sample 3 arranged in the coil 2 in the winding direction of the coil 2 is in a state where the electrical center position of the magnetic material sample 3 and the electrical center position of the coil 2 coincide with each other. ,Stop.
In this state, the actual measurement current is supplied to the coil 2 to measure the magnetostriction of the magnetic material sample.

Since the electric center positions of the coil 2 and the magnetic material sample 3 coincide with each other, the magnetic material sample does not move in the winding direction of the coil 2 and only magnetostriction can be correctly measured.

In particular, when the magnetostriction measuring device having the structure described in claim 2 is targeted, the effect is great.

That is, in the magnetostriction measuring apparatus in this case, the magnetic material sample 3 has a pair of non-magnetic material plates 31,
The first coil 2 is sandwiched by 32, and the displacement in that direction is limited, and the first coil 2 is arranged in a space in which an alternating magnetic field is generated. Due to the alternating magnetic field, the magnetic material sample 3 is displaced by magnetostriction in the direction of the surface sandwiched by the pair of non-magnetic material plates 31, 32, that is, in the winding direction of the first coil 2, and its end surface 3t is , And exhibits vibration according to the displacement due to the magnetostriction.

The optical displacement meter 6 irradiates the end face 3t of the sample 3 with a light beam from the space in the winding direction of the first coil 2 and uses the reflected light to vibrate and displace the end face 3t of the sample 3. Obtain an output signal according to the quantity. In the present invention, this displacement does not include the position variation due to the deviation of the electrical center position of the magnetic material sample 3, but only the magnetostriction. Therefore, the magnetostriction can be measured accurately and precisely.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method according to the present invention will be described below with reference to the drawings together with an embodiment of a novel magnetostriction measuring apparatus to which the present invention is applied.

FIG. 1 shows the entire mechanical structure and signal processing system of the mechanical portion of the magnetostrictive measuring apparatus of this example.
The mechanical configuration of the mechanism section shown in FIG. 1 shows a principle configuration, and a detailed configuration example thereof is as shown in FIG. FIG. 2A is a plan view (partially shown as a cross section) of the mechanical section of the measurement apparatus of this example, and FIG. 2B is a side view (partially shown as a cross section) of the mechanical section of the measurement apparatus of this example. It is).

First, in FIG. 1, reference numeral 1 denotes a hollow cylindrical double glass tube. The glass tube 1 has a shape in which concentric cylindrical glass walls are connected at their ends in the tube axis direction. A coil 2 for generating an alternating magnetic field is provided on the outer periphery of the glass tube 1 except for both ends in the tube axis direction.
Is wound into a solenoid coil. Then, the magnetic material sample 3 is placed at a substantially central position in the cylindrical space in the glass tube 1.

In the case of this example, the magnetic material sample 3 has a flat rectangular thin plate shape, and the thickness, width, and length thereof are obtained in advance. The sample 3 is held by the sample holding means 30 to be described later and placed in the glass tube 1 in a state where the plate surface direction thereof coincides with the tube axis direction of the glass tube 1.

The alternating voltage from the alternating signal generator 11 is supplied to the alternating magnetic field generating coil 2 through the amplifier 12. As a result, the alternating current i flows through the coil 2,
An alternating magnetic field in the tube axis direction is generated in the cylindrical space of the glass tube 1.

By the way, since a relatively large current i is passed through the coil 2, heat is generated. Therefore, in the apparatus of this example, cooling water is caused to flow in the double wall of the glass tube 1 to prevent excessive heat generation.

In order to make this cooling water flow, the glass tube 1 is provided with an opening 1a so as to project from a part of one end side in the tube axis direction and the other end side in the tube axis direction. Of the opening 1b so as to project from that position at a position 180 degrees apart from the position of the opening 1a.
Is provided. Then, as shown in the figure, the glass tube 1 is placed in a horizontal position with the opening 1a facing upward and the opening 1b facing downward, and cooling water is injected from the opening 1a. The cooling water goes through all the parts in the glass tube 1 and is drained from the opening 1b.

When measuring the magnetostriction of the sample 3, the magnetic field in the vicinity of the sample 3 or the magnetic flux (magnetic flux density) passing through the sample 3 is known, and the magnetostriction generated under the magnetic characteristic conditions of the magnetic flux or the magnetic field is measured. There is a need.
Therefore, the coil block CB is provided to measure the magnetic characteristics in the vicinity of the sample 3.

This coil block CB is, in this example,
As will be described later, it comprises a search coil 4 for measuring a magnetic flux passing through the sample 3 and a correction coil 5 for measuring a magnetic field as close to the sample 3 as possible. The detailed configuration will be described later.

In the above structure, when an alternating current i is passed through the coil 2, an alternating magnetic field is induced in the tube axis direction of the glass tube 1, and the alternating magnetic field causes the current in the magnetic material sample 3 as described above. Magnetostriction is generated that oscillates at twice the frequency of i. In this case, since the sample 3 is a flat rectangular thin plate, this magnetostriction appears as expansion and contraction in the plate surface direction (tube axis direction). That is, the end surface 3t of the thickness portion of the sample 3 is displaced in the tube axis direction according to the expansion and contraction of the sample 3.

In this example, the end face 3t of the sample 3 is
Of the sample 3 by measuring the displacement of
The magnetostriction of is directly measured. Since the displacement is measured using light, there is almost no electromagnetic effect.

In FIG. 1, 6 is an optical displacement meter, and 6a
Is the probe. The probe 6a is made of a non-magnetic material. The optical displacement meter 6 of this example includes a probe 6
A light beam 7 is emitted from a and reflected light is obtained from this probe 6a. In this example, the end face 3t of the sample 3 is irradiated with the light beam emitted from the probe 6a. The optical displacement meter 6 receives the reflected light from the end face 3t via the probe 6a, converts the displacement of the end face 3t into a voltage change, and obtains it as an output signal Vλ.

The probe 6a is attached to the end face 3t of the sample 3.
For example, a minute reflector may be attached to reflect the light beam from.

Next, with reference to FIGS. 2 to 4, a more detailed structure of the mechanical portion described above will be described. 3 is an AA cross-sectional view of FIG. 1, and FIG. 4 is an enlarged cross-sectional view of the central portion of the mechanism portion.

As shown in FIG. 2, the outside of the glass tube 1 is
It is covered with a cylindrical case 7 made of Bakelite. The housing 7 is fixed to the base member 8. Glass tube 1
The cooling water inlets / outlets 1 a and 1 b are led to the outside of the housing 7. Further, both ends of the casing 7 in the tube axis direction are attached to the sample 3
It is an opening for entering and exiting and for inserting the probe 6a of the optical displacement meter 6.

The magnetic material sample 3 is held by the sample holding member 30. That is, as shown in FIGS. 2 and 4, in this example, the magnetic material sample 3 is in the shape of an elongated flat thin plate, and a pair of non-magnetic material plates 31 and 31 similarly configured in the shape of an elongated thin plate. It is sandwiched and held by 32. The non-magnetic plates 31 and 32 are preferably as heavy as possible in order to securely hold the magnetic sample. In this example,
Alumina porcelain is used.

In the case of this example, the dimensions of the nonmagnetic plates 31 and 32 are, for example, thickness × width × length = 2 (mm).
It is set to x31 (mm) x277 (mm). Also,
The dimensions of the sample 3 are, for example, thickness × width × length = 1 (mm)
It is set to × 30 (mm) × 280 (mm). That is, the sample 3 is slightly longer than the non-magnetic material plates 31 and 32, and the portion thereof protrudes toward the probe 6a side.
The end surface 3t of the projecting portion is displaced due to magnetostriction. Therefore, it is advisable to attach a reflector to the end face 3t.

One end side in the lengthwise direction of the pair of nonmagnetic plates 31, 32 is fixed by a holding arm 33. in this case,
The holding arm 33 fixes the non-magnetic plates 31 and 32 with the sample 3 in between, for example, with a screw or the like. The other ends of the pair of non-magnetic plates 31, 32 in the length direction are not fixed and are placed on a holding table 34 fixed to the housing 7 or the base 8 in the measurement state. The sample 3 can be exchanged by loosening the screw and releasing the fixed holding of the pair of nonmagnetic plates 31 and 32 by the holding arm 33.

The holding arm 33 holds the holding arm pedestal 35 for guiding the sample 3 out of the glass tube 1 and exchanging it.
On the other hand, it is slidably engaged in the horizontal direction along the tube axis direction of the glass tube 1. Sliding between the holding arm 33 and the holding arm pedestal 35 can be performed very easily, and after the sliding, the holding arm 33 is moved by a screw or the like.
Are fixed to the pedestal 35.

The holding arm cradle 35 is made of a heavy member, and is made of stainless steel in this example.
In order to further increase the horizontal movement distance, the holding arm pedestal 35 is also slidably attached to the base 34 in the same direction as the holding arm 33, and can be fixed by a screw or the like. It is configured. The handle 36 is used when the holding arm pedestal 35 slides.

In this case, in the state of being held by the non-magnetic material plates 31 and 32, the magnetic material sample 3 can freely expand and contract due to magnetostriction in the plate surface direction (tube axis direction of the glass tube 1). However, since it is held by the non-magnetic material plates 31 and 32, the expansion and contraction of the magnetic material sample 3 is restricted in the thickness direction.

Next, the structure of the coil block CB will be described. The search coil 4 is wound in a solenoid coil shape with the tube axis direction of the glass tube 1 as a winding direction, and when the sample 3 is installed in the space inside the glass tube 1, the sample 3 is almost wound around the coil 4. It is supposed to be located in the center. This coil 4 is a sectional view taken along the line AA of FIG.
And as shown in FIG. 4 of the enlarged view of the main part, it is wound around the hollow cylindrical bobbin 41 made of a non-magnetic material, and in the measurement state,
The sample 3 is in a state of being inserted into the hollow portion of the bobbin 41.

The size of the bobbin 41 is selected such that the cross-sectional area of its hollow portion is slightly larger than the cross-sectional areas of the non-magnetic plates 31 and 32 holding the sample 3 therebetween, so that replacement of the sample 3 will not be hindered. Has been done. The bobbin 41 is fixed to one of the non-magnetic plates 31 and 32, for example, at a substantially central position in the length direction of the plate 31 by adhesion or the like.

The correction coil 5 for measuring the magnetic field as close as possible to the sample 3 is formed by winding a wire around the non-magnetic material cores 51 and 52, such as Mylar, and winding the wire. It is fixed to the outer peripheral part. In this example, as shown in FIG. 3, the correction coil 5 is composed of cores 51 and 52 in which wire rods are wound in series above and below the sample 3 on the outer peripheral portion of the search coil 4, respectively. Configured to be connected to. The winding direction of the correction coil 5 also matches the tube axis direction of the glass tube 1. Further, the cross-sectional areas of the cores 51 and 52 are set to a predetermined value A in order to obtain the magnetic flux density. The correction coil 5 may be an air core instead of a non-magnetic core wound with a wire.

Further, as shown in FIG. 2, the lead wire end portions 4L, 5L of the coils 4 and 5 from the coil block CB.
Is guided from the inside of the glass tube 1 to the space between the housing 7 and the outer wall of the glass tube 1, and is connected to an output terminal (not shown) provided outside the housing 7 Is connected to an internal terminal (not shown).

Before actually measuring the magnetostriction of the magnetic material sample 3 by the magnetostriction measuring apparatus configured as described above, in the present invention, the glass tube 1 of the magnetic material sample 3 is used.
The installation position in the tube axis direction inside the coil 2 wound around the glass tube 1 matches the electrical center position in the winding direction and the center position (electrical center) in the tube axis direction of the sample 3. The operation is performed so that such a position is obtained.

Therefore, in this example, the non-magnetic plates 31, 3 are used.
After fixing the sample 3 in a sandwiched state to the holding arm 33 by 2 and arranging it at a substantially physical center position in the glass tube 1, before starting the actual measurement, a predetermined current, for example, shown in FIG. 5A is shown. Such a positive current + is or a negative current −is as shown in FIG. 5B is passed through the coil 2. At this time, the holding arm 3
Loosen the screws that fix the 3 to the pedestal 35,
The holding arm 33 is made slidable with respect to 5.

In this case, the coil 2 is used for alignment.
The magnitude of the current supplied to is not required to be a large current as in the case of measuring the magnetostriction, and may be a value that allows the holding member 30 holding the sample 3 to move, for example, 200 mA. It is said that Further, the supply time of the current may be, for example, about 10 msec.

As described above, when a positive or negative current is is passed, the sample 3 will vibrate and move so that its electrical center position coincides with the center position of the coil 2. And

As described above, since the holding arm 33 and the holding arm receiving base 35 can slide very easily, if the arm 33 is not fixed to the receiving base 35, this sample 3 includes a holding arm 33 and a pair of non-magnetic plates 31 sandwiching the magnetic material sample 3 according to the movement of itself.
32 vibrates left and right, and after a predetermined time, stops moving at a position where the electrical center position of the sample 3 and the central position of the coil 2 coincide. After the elapse of this predetermined time, the holding arm 33 is fixed to the pedestal 35 with a screw. In this way, the electrical center position of the sample 3 can be aligned with the electrical center position of the coil 2.

Next, in this example, the optical displacement meter 6 is further calibrated before the actual measurement is started. The optical displacement meter 6
Generally, the displacement of a light-irradiated portion is measured from a change in intensity of reflected light when light is irradiated. The intensity of the reflected light is inversely proportional to the square of the distance between the probe 6a of the optical displacement meter 6 and the measurement target site, but the displacement is measured by measuring the portion with good linearity as the photoelectric conversion output characteristic of the optical displacement meter 6. use. FIG. 6 shows an example of the output characteristic of the optical displacement meter 6 of this example, and the linearity becomes good when the output is around 5V.

The optical displacement meter 6 is calibrated in the following manner with the distance between the probe 6a and the end surface 3t of the sample 3 being the measurement target site being set at this position with good linearity.

That is, in this example, the optical displacement meter 6
Are attached to the sliding movement member 60, as shown in FIG. The sliding movement member 60 includes a micrometer 61, and by adjusting the micrometer 61,
The tip of the probe 6a is configured to be slidable in the tube axis direction of the glass tube 1 by the distance indicated by the meter. Then, the micrometer 61 is operated to change the distance between the tip of the probe 6a and the end surface 3t of the sample 3 and first adjust the output of the optical displacement meter 6 to a position with good linearity.

In this case, since the photoelectric conversion output of the displacement caused by the magnetostriction of the optical displacement meter 6 is very small with respect to the direct current component of several hundred mV and 5V, even if the output voltage is amplified as it is, The amount of displacement due to strain cannot be amplified to an appropriate value. Therefore, in this example, the DC component of the output of the optical displacement meter 6 is removed as an offset in accordance with the alignment of the output signal of the micrometer 61 to a position having good linearity.

Next, at this position, when the tip of the probe 6a is moved by a predetermined distance by operating the micrometer 61, the output voltage is detected and the output is calibrated. For example, if the output is a volt when moved by 200 μm, it becomes a / 2 when moved by 1 μm.
Calibrate so that it will be 00 volts.

As the optical displacement meter 6, a light beam having a beam spot diameter larger than the thickness of the sample 3 is used. This is because when using a beam having a narrowed beam diameter, irregularities existing on the end face 3t of the sample 3 irradiated with the beam may be detected as strain.

As described above, after the electrical center positions of the sample 3 and the magnetic field generating coil 2 have been aligned and the calibration of the optical displacement meter 6 has been completed, the coil 2 has a frequency of, for example, 50H.
An alternating current i of z, 200 Hz, 400 Hz and an effective value of about 1 A is passed. Then, an alternating magnetic field is induced in the tube axis direction of the glass tube 1, and the alternating magnetic field causes magnetostriction in the magnetic material sample 3 that vibrates at a frequency twice the frequency of the current i as described above. In this case, this magnetostriction appears as expansion and contraction in the plate surface direction (tube axis direction) of the sample 3, and the end surface 3t is displaced in the tube axis direction according to the magnetostriction. The optical displacement meter 6 receives the reflected light from the end face 3t via the probe 6a, converts the displacement of the end face 3t into a voltage change, and obtains it as an output signal Vλ.

Further, a voltage VB corresponding to a change in the magnetic flux φ passing through the bobbin 41 is obtained between the both ends 4a and 4b of the search coil 4 by the alternating magnetic field. The magnetic flux passing through the bobbin 41 is the same as the magnetic flux passing through the portion inside the bobbin except the sample 3.
It consists of the sum of the magnetic flux passing through.

Further, between both ends 5a and 5b of the correction coil 5, a voltage VH corresponding to the magnetic flux change in the space portion of the sum of the sectional areas A of the cores 51 and 52 is obtained.

The output signal Vλ from the optical displacement meter 6 and the voltages VB and VH obtained by the search coil 4 and the correction coil 5
Are respectively in the signal conditioner 21,
While being amplified, unnecessary high frequency components and low frequency components are removed.

The output signals Sλ, SB, SH obtained by processing the displacement output Vλ, the voltage VB, and the voltage VH by the signal conditioner 21 as described above are supplied to the A / D converter 22, and the digital signal Dλ, DB, DH
And is temporarily stored in the buffer memory 23.
The digital signals Dλ, DB stored in the memory 23,
The DH is supplied to the averaging circuit 24.

The averaging circuit 24 carries out a process for obtaining an average based on the trigger timing. In the case of this example, the alternating signal from the alternating signal generator 11 is supplied to the trigger generator 13 to synchronize with the trigger signal T.
G is obtained from this, and this trigger signal TG is supplied to the averaging circuit 24.

In the averaging circuit 24, each digital signal is averaged by being triggered by this trigger signal TG synchronized with the alternating signal. Each input signal of the averaging circuit 24 includes noise components other than the target displacement and voltage synchronized with the alternating signal, but this averaging process causes unnecessary noise components other than the component synchronized with the alternating signal. To be removed.

FIG. 7A shows the output signal of the optical displacement meter 6 when the averaging circuit 24 is input, and FIG. 7B shows the output signal Eλ after the averaging process. Further, FIG. 7C is an example of an averaging processing output EB of the voltage EB from the search coil 4 on the same time scale. Similarly, the averaging output EH of the voltage VH from the correction coil 5 is also noise-removed.

In this way, in the averaging circuit 24, the noise-removed outputs Eλ, EB, EH are supplied to the signal processing circuit 25 composed of a microcomputer. In this signal processing circuit 25, the magnetic field H near the sample 3 is obtained from the output EH. That is, the averaged output EH obtained from the output voltage VH of the coil 5 corresponds to the change of the magnetic flux φ in the space portion occupied by the cores 51 and 52 (dφ / dt: t is time). , 52 to obtain the magnetic flux φ passing through the space. Since the cross-sectional areas of the portions of the cores 51 and 52 are known, the magnetic flux density Ba of the space near the sample 3 is obtained from this magnetic flux φ, and the magnetic permeability of the space is also known. A magnetic field H in the vicinity is required.

Further, the magnetic flux passing through the sample 3 is obtained from the output EB and the magnetic flux density Ba of the space, and the magnetic flux density Bs of the portion of the sample 3 is obtained from the cross-sectional area of the sample 3. That is, the output EB can be considered as the sum of the change in the magnetic flux passing through the space inside the bobbin 41 and the change in the magnetic flux passing through the sample 3. The magnetic flux of the space portion (the cross-sectional area is known) in the bobbin 41 can be obtained from the magnetic flux density Ba, and the voltage component caused by the change can also be obtained. As a result, the voltage corresponding to the change of the magnetic flux passing only the sample 3 portion can be obtained, and the magnetic flux passing the sample 3 portion can be obtained. Since the cross-sectional area of the sample 3 is known, the magnetic flux density Bs of the sample 3 portion can be obtained. Further, the magnetic permeability μ of the sample 3 can be obtained from the magnetic field H and the magnetic flux density Bs.

Magnetostriction λ can be obtained from the output Eλ. Then, the relationship between the magnetic field H or the magnetic flux density B and this magnetostriction λ is obtained. The relationship is CR
It is displayed on the output device 26 such as a T display or a printer, or is output on a recording sheet.

FIG. 8A shows the obtained magnetic field H and magnetic flux density Bs, and FIG. 8B is a so-called magnetic hysteresis curve showing the relationship between the two. FIG. 9A shows the waveforms of the magnetic field H and the magnetostriction λ, and FIG. 9B shows the relationship between the two.
That is, the relationship of magnetic field-magnetostriction (H-λ) is shown. 8 and 9 show an alternating current of 200 Hz,
This is a case where a current of 0.6 A was passed through the coil 2 and the magnetostriction of the novel silicon steel plate was measured.

Similarly, FIG. 10A shows the waveforms of the magnetic flux density Bs and the magnetostriction λ, and FIG. 10B shows the relationship between them, that is, the relationship of the magnetic flux density-magnetostriction (B-λ). In the example of FIG. 10, 400 Hz, 1.12
The alternating current of A is applied to the coil 2.

As a result of the measurement of the strain of the magnetic material by the inventor of the present invention, according to the present invention, it is possible to measure the magnetostriction up to 10 ⁻⁹ m when the sample is 1 m. It has been found.

[0077]

As described above, according to the present invention, before the actual measurement of magnetostriction, a predetermined current is supplied to the coil for generating a magnetic field for a predetermined time to generate a magnetic material sample and a magnetic field. Since the electrical center of the work coil is adjusted, the magnetic sample is displaced only during measurement without causing the position change, as in the case where the magnetic material sample is displaced from the electrical center position. . Therefore, by measuring this displacement, it becomes possible to measure the magnetostriction more finely.

A magnetostriction measuring apparatus for realizing the method of the present invention is, like a conventional magnetostriction measuring apparatus,
Rather than indirectly measuring magnetostriction with a mirror,
An apparatus adapted to directly measure magnetostriction as a displacement of an end surface of a sample by using an optical displacement meter, and further, in the case of a novel apparatus having the following features, the method of the present invention is applied. By doing so, the magnetostriction can be measured with higher precision.

In this new device, an extra material is not added to the sample unlike the conventional method of attaching a mirror to the sample, and therefore, also in this point, more accurate measurement of magnetostriction is possible. Become.

Further, since the magnetic material sample is held by being sandwiched by a pair of plates made of non-magnetic material, the positional fluctuation of the magnetic material sample itself and the displacement other than the displacement direction intended for measurement by the optical displacement meter are limited. Therefore, the measurement accuracy can be improved in this respect as well.

Further, it is possible to attach a coil block for measuring the magnetic characteristics in the vicinity of the sample by utilizing a pair of non-magnetic material plates, and furthermore, the displacement measurement can be performed by using an optical beam with an optical displacement meter. Since this is done, it is not necessary to pay attention to the coil winding portion. Therefore, it becomes possible to accurately know the magnetic characteristics near the sample.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a magnetostriction measuring apparatus according to the present invention.

FIG. 2 is a diagram showing a configuration example of a mechanical portion of an embodiment of the magnetostriction measuring apparatus according to the present invention.

FIG. 3 is a diagram for explaining in detail a configuration of a main part of the example of FIG.

FIG. 4 is an enlarged cross-sectional view of the configuration of the main part of the example of FIG.

FIG. 5 is a diagram for explaining an example of a current supplied to the magnetic field generating coil before the start of measurement in the magnetostriction measuring apparatus of the present invention.

FIG. 6 is a diagram for explaining output characteristics of the optical displacement meter.

FIG. 7 is a diagram showing an example of an output signal waveform of each part of an embodiment of the magnetostriction measuring apparatus according to the present invention.

FIG. 8 is a diagram showing an example of waveforms of magnetic fields and magnetic flux densities obtained by the magnetostriction measuring device according to the present invention and their relations.

FIG. 9 is a diagram showing an example of waveforms of a magnetic field and magnetostriction obtained by the magnetostriction measuring apparatus according to the present invention, and their relations.

FIG. 10 is a diagram showing an example of waveforms of magnetic flux density and magnetostriction obtained by the magnetostriction measuring apparatus according to the present invention, and a relationship thereof.

FIG. 11 is a diagram for explaining a mechanism of magnetostriction generation.

FIG. 12 is a diagram for explaining an example of a conventional magnetostrictive measuring device.

[Explanation of symbols]

 1 Glass Tube 2 Coil for Generating Alternating Magnetic Field 3 Magnetic Sample 4 Searching Coil 5 Correction Coil 6 Optical Displacement Meter 11 Alternating Signal Generator 13 Trigger Signal Generator 22 A / D Converter 23 Buffer Memory 24 Averaging Circuit 25 Signal Processing Circuit 30 sample holding member 41 bobbin 31, 32 non-magnetic material plate 51, 52 core 61 micrometer

Claims (3)

[Claims] 1. A magnetic material sample is arranged in an internal space of a coil for magnetic field generation wound in a cylindrical shape, an electric current is passed through the coil to generate an alternating magnetic field, and the alternating magnetic field causes the magnetic material sample to be applied to the magnetic material sample. In the method for measuring the magnetostriction generated, a current is supplied to the coil for electrical center alignment between the magnetic material sample and the coil before generating an alternating magnetic field for actual measurement. A method of measuring magnetostriction, characterized in that 2. A first coil for magnetic field generation wound in a cylindrical shape, and an alternating signal supplied to the first coil for generating an alternating magnetic field in the internal space of the first coil. An alternating signal generator to be generated; a sample holding member for disposing a magnetic material sample in the internal space of the first coil; and a second coil for detecting magnetic characteristics in the vicinity of the sample, And a magnetostriction detecting means for obtaining a displacement of the magnetic material sample due to magnetostriction. Based on the induced voltage output obtained in the second coil and the output signal of the magnetostrictive detecting means, In a magnetostriction measuring method using a magnetostriction measuring device designed to obtain the relationship between the magnetic characteristics and the amount of magnetostriction that occurs in the magnetic material sample under the magnetic characteristics conditions, generate an alternating magnetic field for actual measurement. The magnetic strain measurement method is characterized in that, before the step, a current is supplied to the first coil for electrical center alignment between the magneto-magnetic material sample and the first coil. 3. A first coil for generating a magnetic field wound in a cylindrical shape, and an alternating signal supplied to this first coil for generating an alternating magnetic field in the internal space of the first coil. An alternating signal generator for generating and a pair of non-magnetic material plates for sandwiching and holding a magnetic material sample are provided,
A substantially central portion in a space surrounded by the first coil for generating a magnetic field in a state where a direction of a sandwiched surface of the magnetic material sample matches a winding direction of the first coil, In addition, a sample holding member for disposing the magnetic material sample at approximately the center in the winding direction of the first coil, and the pair of non-magnetic members for detecting magnetic characteristics in the vicinity of the sample. A second coil fixed to the sample holding member and an end face of the magnetic sample between the pair of non-magnetic plates of the sample holding member around the portion of the body plate that holds the sample. An optical displacement meter for irradiating a light beam to a reflecting plate attached to this end face, and detecting the displacement of the end face of the magnetic material sample from the reflected light, and the induced voltage output obtained in the second coil From the output signal of the optical displacement meter, In the magnetostriction measuring method using the magnetostriction measuring device, which was designed to obtain the relationship between the magnetic characteristics in the vicinity of the magnetic material sample and the amount of magnetostriction generated in the magnetic material sample under the magnetic characteristics conditions, the actual measurement Prior to generating an alternating magnetic field for the first coil, a current is supplied to the first coil for electrical center alignment between the magneto-magnetic material sample and the first coil. And a method for measuring magnetostriction.