JP2022038362A - Vibration detector - Google Patents

Abstract

To provide a vibration detector capable of suppressing fluctuations in measurement accuracy.SOLUTION: A vibration detector includes: a first magnetic circuit comprising a first magnet, and including an air gap in a part, and a magnetic flux line passing portion of a magnetic material adjacent to the gap; a second magnetic circuit that comprises a second magnet, includes the air gap in a part and the magnetic flux line passing portion, and is formed by stacking on the first magnetic circuit along a sensitivity axis, and in which the direction of a magnetic flux line in the magnetic flux line passing portion and the air gap matches the direction of a magnetic flux line by the first magnetic circuit; and a conductor placed in the gap and displaceable relatively with respect to the first magnetic circuit and the second magnetic circuit.SELECTED DRAWING: Figure 1

Description

This case relates to a vibration detector.

A vibration detector that detects the magnitude of vibration by measuring the electromotive force obtained by vibrating a conductor in a magnetic field generated by a magnetic circuit is disclosed (see, for example, Patent Documents 1 to 5). ..

Japanese Unexamined Patent Publication No. 2000-46638 Japanese Patent Application Laid-Open No. 2003-42837 Japanese Unexamined Patent Publication No. 2001-336974 JP-A-2015-4539 Japanese Unexamined Patent Publication No. 10-148567

The characteristics of the magnets that make up the magnetic circuit change depending on the ambient temperature. For example, when the ambient temperature rises, the magnetic force of the magnet tends to weaken. Therefore, the sensitivity of the vibration detector may change depending on the installation environment, and the measurement accuracy of the vibration detector may fluctuate.

In one aspect, it is an object of the present invention to provide a vibration detector capable of suppressing fluctuations in measurement accuracy.

In one embodiment, the vibration detector according to the present invention includes a first magnet, a first magnetic circuit including a gap and a magnetic flux line passing portion of a magnetic material adjacent to the gap, and a first magnetic circuit. It is provided with two magnets, includes the void and the magnetic flux line passing portion in a part thereof, and is formed by being laminated on the first magnetic circuit along the sensitivity axis, and is formed by laminating the magnetic flux line in the magnetic flux line passing portion and the void. Is arranged in the gap between the second magnetic circuit whose direction is the same as the direction of the magnetic flux line by the first magnetic circuit, and is displaced relative to the first magnetic circuit and the second magnetic circuit. It is characterized by having a possible conductor.

In the vibration detector, the first magnetic circuit and the second magnetic circuit may be formed by a magnetic material in a portion excluding the gap.

The vibration detector has a tubular portion in which a top plate portion and a bottom plate portion are connected by a peripheral wall portion, and a shaft portion provided in a central portion of the tubular portion along the sensitivity axis. The gap is formed between the annular portion protruding inward from the peripheral wall portion and the shaft portion, and the first magnetic circuit has the top plate portion, the annular portion, and the gap. And the shaft portion, and the second magnetic circuit may include the bottom plate portion, the annular portion, the gap, and the shaft portion.

In the vibration detector, the first magnet and the second magnet may be provided on the shaft portion.

In the vibration detector, the first magnet and the second magnet may be provided on the peripheral wall portion.

In the vibration detector, the magnetic flux density in the magnetic flux line passing portion can be equal to or higher than the saturation magnetic flux density of the magnetic material forming the magnetic flux line passing portion.

It is possible to provide a vibration detector capable of suppressing fluctuations in measurement accuracy.

FIG. 1A is a schematic cross-sectional view illustrating the overall configuration of the vibration detector according to the first embodiment, and FIG. 1B is a cross-sectional view of a yoke included in the vibration detector according to the first embodiment. It is a figure. It is a figure which illustrates the magnetic flux line in the vibration detector which concerns on 1st Embodiment. It is a figure which illustrates the magnetic flux line in the vibration detector which concerns on a comparative form. It is a graph which illustrates the relationship between the strength of the magnetic field and the magnetic flux density in the magnetic material forming a yoke. It is a schematic cross-sectional view which illustrates the vibration detector which concerns on 2nd real form.

Hereinafter, embodiments will be described with reference to the drawings.

(First Embodiment)
FIG. 1A is a schematic cross-sectional view illustrating the overall configuration of the vibration detector 100 according to the first embodiment. In FIG. 1A, the sensitivity axis AX1 (for example, the vertical direction) is defined as the Z axis, and the direction orthogonal to the sensitivity axis AX1 (for example, the horizontal direction) is defined as the X axis.

As illustrated in FIG. 1A, the vibration detector 100 has a structure in which each device is arranged in a case 10 having a bottomed lid and a substantially cylindrical shape having an axis along the Z axis. The case 10 is made of a non-magnetic metal such as SUS304.

A yoke 21 is arranged in the case 10. As shown in FIG. 1 (B), the yoke 21 is formed as a tubular portion in which the top plate portion 21a and the bottom plate portion 21b are connected by a peripheral wall portion 21c. The top plate portion 21a and the bottom plate portion 21b are provided so as to be substantially axisymmetric with the axis AX2 extending along the X axis as the axis of symmetry.

The yoke 21 which is a tubular portion has an axis along the Z axis. The yoke 21 is formed of a magnetic material (soft magnetic material). The yoke 21 includes an annular portion 21d protruding inward from the peripheral wall portion 21c connecting the top plate portion 21a and the bottom plate portion 21b. The annular portion 21d is provided so that the axis AX2 passes at a position that is ½ of the dimension of the annular portion 21d along the Z-axis direction. The annular portion 21d forms a magnetic flux line passing portion in the first magnetic circuit M1 and the second magnetic circuit M2, which will be described later, and functions as an outer pole of the yoke 21.

Since the outer diameter of the yoke 21 is set to be slightly smaller than the inner diameter of the case 10, the yoke 21 is housed in the case 10. The yoke 21 is fixed in the case 10.

A substantially cylindrical first magnet 22a having an axis along the Z-axis direction is arranged at the center of the lower surface of the top plate portion 21a. On the other hand, a second magnet 22b having a substantially cylindrical shape having an axis along the Z-axis direction is arranged at the center of the upper surface of the bottom plate portion 21b. A substantially cylindrical top plate 23 having an axis along the Z-axis direction is arranged between the first magnet 22a and the second magnet 22b. The top plate 23 is formed of a magnetic material (soft magnetic material). The top plate 23 is arranged at a position facing the annular portion 21d that functions as an outer pole. As a result, the top plate 23 functions as an internal pole. The first magnet 22a and the second magnet 22b of the present embodiment are both neodymium magnets.

The first magnet 22a, the second magnet 22b, and the top plate 23 are provided as shaft portions provided along the sensitivity shaft AX1 at the central portion of the yoke 21 which is a cylindrical portion. Therefore, the vibration detector 100 according to the present embodiment is an internal magnetic type vibration detector. Here, the first magnet 22a and the second magnet 22b are arranged so that the same poles face each other via the top plate 23. For example, when the S pole of the S pole and the N pole of the first magnet 22a is arranged on the side closer to the top plate 23, the S pole of the second magnet 22b is also on the side closer to the top plate 23. Be placed.

The annular portion 21d that functions as the outer pole and the top plate 23 that functions as the inner pole are separated from each other. As a result, the gap 24 is formed by the annular portion 21d and the top plate 23. A DC magnetic field is formed in the gap 24.

As a result, the first magnetic circuit M1 is formed by the top plate portion 21a, the peripheral wall portion 21c (above the axis AX2 of the peripheral wall portion 21c), the annular portion 21d, the gap 24, the top plate 23, and the first magnet 22a. .. That is, the first magnetic circuit M1 includes a top plate portion 21a, an annular portion 21d, a gap 24, and a shaft portion.

Further, the second magnetic circuit M2 is formed by the bottom plate portion 21b, the peripheral wall portion 21c (below the axis AX2 of the peripheral wall portion 21c), the annular portion 21d, the gap 24, the top plate 23, and the second magnet 22b. That is, the second magnetic circuit M2 includes a bottom plate portion 21b, an annular portion 21d, a gap 24, and a shaft portion.

The first magnetic circuit M1 and the second magnetic circuit M2 are formed by being laminated along the sensitivity axis AX1. The first magnetic circuit M1 and the second magnetic circuit M2 include a common annular portion 21d, a common top plate 23, and a common void 24.

Referring to FIG. 2, the magnetic flux lines in the first magnetic circuit M1 are the first magnet 22a, the top plate 23, the gap 24, the annular portion 21d, the peripheral wall portion 21c (above the axis AX2 of the peripheral wall portion 21c), and the sky. A loop called a plate portion 21a and a first magnet 22a is formed. For convenience, this loop is referred to as an internal rotation loop in the first magnetic circuit M1. Alternatively, the magnetic flux lines in the first magnetic circuit M1 include the first magnet 22a, the top plate portion 21a, the peripheral wall portion 21c (above the axis AX2 of the peripheral wall portion 21c), the annular portion 21d, the void 24, and the top plate 23. A loop called the first magnet 22a is formed. For convenience, this loop is referred to as an external rotation loop in the first magnetic circuit M1.

On the other hand, the magnetic flux lines in the second magnetic circuit M2 include the second magnet 22b, the top plate 23, the gap 24, the annular portion 21d, the peripheral wall portion 21c (below the axis AX2 of the peripheral wall portion 21c), and the bottom plate portion 21b. A loop called the second magnet 22b is formed. For convenience, this loop is referred to as an internal rotation loop in the second magnetic circuit M2. Alternatively, the magnetic flux lines in the second magnetic circuit M2 include the second magnet 22b, the bottom plate portion 21b, the peripheral wall portion 21c (below the axis AX2 of the peripheral wall portion 21c), the annular portion 21d, the void 24, and the top plate 23. A loop called the second magnet 22b is formed. For convenience, this loop is referred to as an external rotation loop in the second magnetic circuit M2.

Here, when the magnetic flux lines in the first magnetic circuit M1 form an internal rotation loop, the magnetic flux lines in the second magnetic circuit M2 also form an internal rotation loop. Further, when the magnetic flux lines in the first magnetic circuit M1 form an external rotation loop, the magnetic flux lines in the second magnetic circuit M2 also form an external rotation loop. This is because the first magnet 22a and the second magnet 22b are arranged so that the same poles face each other via the top plate 23. As a result, the direction of the magnetic flux line by the first magnetic circuit M1 in the gap 24 and the direction of the magnetic flux line by the second magnetic circuit M2 match.

In the present embodiment, the first magnetic circuit M1 and the second magnetic circuit M2 are laminated along the sensitivity axis AX1 and the directions of the magnetic flux lines are the same, so that the density of the magnetic flux lines passing through the void 24 is the same. Is high. That is, since the magnetic flux line by the first magnetic circuit M1 and the magnetic flux line by the second magnetic circuit M2 in the same direction pass through the gap 24, the magnetic flux density is high.

In FIG. 2, a magnetic flux line is drawn, and hatching is omitted in order to make it easy to understand.

In the gap 24, a substantially cylindrical coil 30 provided with a winding conductor is arranged so as to orbit around the Z-axis direction. The coil 30 is supported by a pair of upper and lower support springs 40. The coil 30 is relatively displaceable and oscillating in the void 24 with respect to the first magnetic circuit M1 and the second magnetic circuit M2. The coil 30 is formed by directly winding the coil wire in a cylindrical shape without using a bobbin made of a non-magnetic material, or by winding the coil wire on the bobbin in a cylindrical shape. The two lead wires 51 extending from the coil 30 are connected to the output terminal 52 penetrating the top plate portion 21a and the lid of the case 10.

When the coil 30 vibrates along the Z-axis direction, a voltage E proportional to the relative velocity between the coil 30 and the first magnetic circuit M1 and the second magnetic circuit M2 is generated at both ends of the coil 30. This voltage can be expressed by the following equation (1). By measuring this voltage E using the output terminal 52, the vibration speed v of the coil 30 can be detected, and the vibration displacement can be detected.
E = BLv (1)
B: Magnetic flux density of the gap 24 in which the coil 30 is located L: Effective length of the coil 30 v: Relative velocity between the coil 30 and the first magnetic circuit M1 and the second magnetic circuit M2.

Here, in order to explain the effect of the vibration detector 100 according to the present embodiment, the vibration detector 200 according to the comparative embodiment will be described. FIG. 3 is a schematic cross-sectional view illustrating the configuration of the vibration detector 200. As illustrated in FIG. 3, the vibration detector 200 differs from the vibration detector 100 in that the yoke 221 is provided instead of the yoke 21. The yoke 221 is made of a magnetic material, has a bottom plate portion 221b, a peripheral wall portion 221c, and an annular portion 221d that functions as an outer pole, and has a substantially cylindrical shape having an axis along the Z axis. However, unlike the yoke 21, it does not have a top plate.

In the vibration detector 200, a substantially cylindrical magnet 220 having an axis along the Z-axis direction is arranged at the center of the upper surface of the bottom plate portion 221b, and the magnet 220 has an axis along the Z-axis direction. A cylindrical top plate 230 is arranged. The top plate 230 is formed of a magnetic material and functions as an internal pole. A gap 240 is formed between the annular portion 221d and the top plate 230. As a result, the vibration detector 200 is formed with a single magnetic circuit M200 including a bottom plate portion 221b, a peripheral wall portion 221c, an annular portion 221d, a gap 240, a top plate 230, and a magnet 220. Then, in the gap 240, a coil 30 having a substantially cylindrical shape supported by a pair of upper and lower support springs 40 is arranged. The coil 30 is connected to the output terminal 52 via two lead wires 51.

Also in the vibration detector 200, the vibration speed v can be detected by measuring the voltage E using the output terminal 52. However, the characteristics of the magnet 220 change depending on the ambient temperature. For example, as the ambient temperature rises, the magnetic force of the magnet 220 tends to weaken. Therefore, the sensitivity of the vibration detector 200 changes depending on the installation environment, and the measurement accuracy of the vibration detector 200 fluctuates.

Further, it is considered that the magnetic flux leakage in the magnetic circuit M200 is a cause of the fluctuation of the measurement accuracy of the vibration detector 200. It is considered that the magnetic flux line drawn in FIG. 3 tends to leak upward along the sensitivity axis AX1 around the gap 240. That is, it is considered that the yoke 221 included in the vibration detector 200 does not have a top plate portion, and the magnetic flux tends to leak to the upper side of the annular portion 221d. Therefore, even if the magnetic force of the magnet 220 is increased and the strength of the magnetic field is increased, it is considered difficult to significantly improve the magnetic flux density in the void 240.

Here, referring to FIG. 4, which is an example of a graph showing the relationship between the magnetic field strength and the magnetic flux density in the magnetic material forming the yoke 21, the magnetic field strength is determined between the first region and the second region with a certain threshold value as a boundary. It can be divided into areas. In the region where the magnetic field is weak, that is, in the first region where the strength of the magnetic field is lower than the threshold value, the magnetic flux density rapidly increases as the strength of the magnetic field increases. On the other hand, in the region where the magnetic field is strong, that is, in the second region where the strength of the magnetic field is higher than the threshold value, the increase in the magnetic flux density due to the increase in the strength of the magnetic field slows down, and the magnetic flux density is generally saturated. ing. As described above, in the second region, the magnetic flux density is unlikely to change even if the strength of the magnetic field changes. In other words, in the region where the magnetic flux density is high, the magnetic flux density is unlikely to change even if the strength of the magnetic field changes. Therefore, according to the vibration detector 100 of the present embodiment, the magnetic flux density changes even if the ambient temperature changes and the strength of the magnetic field generated by the first magnet 22a and the second magnet 22b changes. Hateful. As a result, the change in sensitivity due to the installation environment of the vibration detector 100 is suppressed, and the change in measurement accuracy is suppressed.

Here, the threshold value in this embodiment is the saturation magnetic flux density Bs of the magnetic material forming the yoke 21. The threshold value can be appropriately set depending on the temperature characteristic of the vibration detector 100, that is, how much the sensitivity to temperature is set, but the saturation magnetic flux density Bs is one of the items representing the magnetic characteristic of the magnetic material. Therefore, it is easy to adopt it as a threshold.

In the vibration detector 100, the magnet is selected, the magnetic material forming the yoke 21 is selected, and the shape (dimensions) of the yoke 21 is selected so that the strength of the magnetic field and the magnetic flux density can be maintained in the second region. The settings have been made. First, regarding the magnet, in the present embodiment, neodymium magnets are used as the first magnet 22a and the second magnet 22b, but other magnets, for example, rare earth magnets such as samarium-cobalt magnets may be used. Further, if the magnetic material forming the yoke 21 is a material in which the first region and the second region shown in FIG. 4 can be clearly distinguished and the value of the saturation magnetic flux density is not too large, the magnetic flux density is set to the second region. Easy to maintain and easy to use. In this embodiment, permalloy is adopted as a material having such properties. Among the shapes (dimensions) of the yoke 21, it is the thickness (dimensions along the Z direction) of the annular portion 21d of the yoke 21 that affects the magnetic flux density in the vibration detector 100. Therefore, the thickness of the annular portion 21d in the present embodiment is set according to the performance of the first magnet 22a and the second magnet 22b adopted and the material of the magnetic material forming the yoke 21.

In the vibration detector 200 according to the comparative embodiment, since the magnetic flux easily leaks and it is difficult to increase the magnetic flux density in the void 240, it is difficult to use it in the second region in FIG. 4, and it is easy to use it in the first region. Therefore, when the ambient temperature of the vibration detector 200 changes and the strength of the magnetic field changes, the magnetic flux density changes significantly accordingly. As a result, the measurement accuracy of the vibration detector 200 tends to fluctuate.

On the other hand, in the vibration detector 100 according to the present embodiment, since the magnetic flux line by the first magnetic circuit M1 and the magnetic flux line by the second magnetic circuit M2 both pass through the annular portion 21d, the annular portion 21d The magnetic flux can be concentrated on. Further, since the first magnetic circuit M1 and the second magnetic circuit M2 are laminated and formed along the sensitivity axis AX1, leakage of magnetic flux is also suppressed. As a result, the magnetic flux density of the void 24 increases, and the vibration detector 100 can be used in the second region where the magnetic flux density is close to the saturated state. Since the annular portion 21d is arranged substantially at the center of the vibration detector 100 in the direction along the sensitivity axis AX1, leakage of magnetic flux is further suppressed.

By using the annular portion 21d in the second region, even if the magnetic force of the first magnet 22a or the second magnet 22b changes due to the influence of the ambient temperature, the magnetic flux density of the annular portion 21d is less likely to change. As a result, the change in the magnetic flux density in the gap 24 is also suppressed, and the fluctuation in the measurement accuracy of the vibration detector 100 is suppressed.

(Second Embodiment)
FIG. 5 is a schematic cross-sectional view illustrating the vibration detector 100a according to the second actual embodiment. The difference between the vibration detector 100a and the vibration detector 100 of FIG. 1A is as follows.

First, in the vibration detector 100, the first magnet 22a and the second magnet 22b provided in the central portion of the yoke 21 as a part of the shaft portion are provided, and in the vibration detector 100, the peripheral wall portion 21c is provided. It is placed in a position. Along with this, the top plate 23 is provided from the top plate portion 21a to the bottom plate portion 21b. As a result, the vibration detector 100a according to the second embodiment forms an external magnetic type vibration detector.

Also in such a vibration detector 100a, the first magnetic circuit M1 and the second magnetic circuit M2 including the common annular portion 21d and the common void 24 are laminated and formed along the sensitivity axis AX1. .. As a result, a high magnetic flux density in the gap 24 can be maintained, and the vibration detector 100a can be used in the second region shown in FIG.

As a result, even if the magnetic force of the first magnet 22a or the second magnet 22b changes due to the influence of the ambient temperature, the magnetic flux density of the annular portion 21d is less likely to change. As a result, the change in the magnetic flux density in the void 24 is also suppressed, and the fluctuation in the measurement accuracy of the vibration detector 100a is suppressed.

In both the vibration detector 100 and the vibration detector 100a, the first magnetic circuit M1 and the second magnetic circuit M2 are provided substantially line-symmetrically with the axis AX2 as the axis of symmetry. It does not necessarily have to be arranged line-symmetrically. The axis that separates the first magnetic circuit M1 and the second magnetic circuit M2 may be located between the top plate portion 21a and the bottom plate portion 21b of the yoke 21. The first magnetic circuit M1 and the second magnetic circuit M2 may include a gap 24 common to the common annular portion 21d.

Although the examples of the present invention have been described in detail above, the present invention is not limited to the specific examples thereof, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Case 21 York 21a Top plate 21b Bottom plate
21c Peripheral wall part 21d Circular part 22a First magnet 22b Second magnet 23 Top plate 24 Void 30 Coil 40 Support spring 51 Lead wire 52 Output terminal M1 First magnetic circuit M2 Second magnetic circuit 100, 100a Vibration detector

Claims (6)

A first magnetic circuit including a first magnet, a gap, and a magnetic flux line passing portion of a magnetic material adjacent to the gap,
A second magnet is provided, and the gap and the magnetic flux line passing portion are partially included, and the magnetic flux in the magnetic flux line passing portion and the gap is formed by being laminated on the first magnetic circuit along the sensitivity axis. A second magnetic circuit whose wire direction matches the direction of the magnetic flux line by the first magnetic circuit, and
A conductor arranged in the gap and displaceable relative to the first magnetic circuit and the second magnetic circuit.
A vibration detector characterized by being equipped with. The vibration detector according to claim 1, wherein the first magnetic circuit and the second magnetic circuit have a portion excluding the voids formed of a magnetic material. It has a cylindrical portion in which a top plate portion and a bottom plate portion are connected by a peripheral wall portion, and a shaft portion provided in a central portion of the tubular portion along the sensitivity axis.
The gap is formed between the annular portion protruding inward from the peripheral wall portion and the shaft portion.
The first magnetic circuit includes the top plate portion, the annular portion, the void, and the shaft portion.
The second magnetic circuit includes the bottom plate portion, the annular portion, the void, and the shaft portion.
The vibration detector according to claim 1 or 2. The vibration detector according to claim 3, wherein the first magnet and the second magnet are provided on the shaft portion. The vibration detector according to claim 3, wherein the first magnet and the second magnet are provided on the peripheral wall portion. The vibration detection device according to any one of claims 1 to 5, wherein the magnetic flux density in the magnetic flux line passing portion is equal to or higher than the saturated magnetic flux density of the magnetic material forming the magnetic flux line passing portion.

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