WO2024135209A1 - Linear position sensor and level sensor - Google Patents

Abstract

Provided are a linear position sensor and a level sensor with which the detection accuracy is less likely to vary even when the detection range is increased and usage conditions fluctuate, the linear position sensor comprising: a magnetic sensor 18c in which a magnetic detection element 18d is enclosed; a magnetism detection component 18 formed by attaching the magnetic sensor 18c to a substrate 27; an elongated magnetic body 12 disposed so that an end thereof faces the magnetism detection component 18; a magnet 15 capable of moving between the two ends of the elongated magnetic body 12; and a frame body 20 that supports the elongated magnetic body 12 with respect to the magnetism detection component 18 so as to be capable of moving in the longitudinal direction, the frame body 20 enclosing a magnet 15, an elastic part 23 being provided to the frame body 20, and the end of the elongated magnetic body 12 and the magnetic detection element 18d being biased by the elastic part 23 so as to maintain a prescribed spacing.

Description

Linear Position and Level Sensors

The present invention relates to a linear position sensor and a level sensor using the same.

Traditionally, linear position sensors have been used as level sensors to detect the liquid level in various tanks, with many known sensors supporting a magnet on a float that can rise and fall along a stem, magnetically detecting the position of the float. Many of these linear position sensors place a reed switch at a specified position on the stem, and detect that the liquid level has reached a specified position when the float reaches a specified position on the stem.

A level sensor has also been proposed in which a magnetic concentrator member is placed on the stem and a magnetoelectric conversion element is placed on the longitudinal end of the magnetic concentrator member (see Patent Document 1). This level sensor is said to be able to continuously detect changes in the liquid level.

JP 2009-300189 A

However, the level sensor using soft ferrite described in Patent Document 1 has the problem that the range in which the liquid level can be continuously detected is narrow, and detection accuracy is prone to fluctuating under operating conditions where the temperature changes.

The present invention aims to provide a linear position sensor with a wide detection range that is less susceptible to variations in detection accuracy even when usage conditions change, and a level sensor that uses the same.

The linear position sensor of the present invention, which solves the above problems, comprises a magnetic sensor containing a magnetic detection element, a magnetic detection component formed by mounting the magnetic sensor on a substrate, a long magnetic body arranged with its end facing the magnetic detection component, a magnet that can move between both ends of the long magnetic body, and a frame that supports the long magnetic body in a state where it can move longitudinally relative to the magnetic detection component and contains the magnet, and an elastic part is provided on the frame, and the elastic part biases the end of the long magnetic body and the magnetic detection element to maintain a predetermined distance.

This linear position sensor may have two magnetic detection components facing each end of the long magnetic body, with both ends of the long magnetic body facing the magnetic detection components, and may be biased by an elastic part to maintain a predetermined distance between both ends of the long magnetic body and each magnetic detection element.

In this linear position sensor, the frame preferably has a receiving portion that supports the end of the long magnetic body at a predetermined position. This linear position sensor preferably has a long pipe that houses the long magnetic body, and the long pipe is fixed to the frame in a non-jointed state with the long magnetic body. The long magnetic body is preferably made of a soft magnetic material having a saturation magnetic flux density of 0.65 T or more, a coercive force of 12 A/m or less, and a magnetic permeability of 3000 or more at a magnetic flux density of 5 to 15 mT. The magnetic permeability of the long magnetic body at a magnetic flux density of 5 to 15 mT is preferably 5000 or more. The long magnetic body is preferably made of PC permalloy, and the PC permalloy has a saturation magnetic flux density of 0.65 T or more and a magnetic permeability of 8000 or more at a magnetic flux density of 5 to 15 mT. The long magnetic body is preferably made of PB permalloy, which has a saturation magnetic flux density of 1 T or more and a magnetic permeability of 5000 or more at a magnetic flux density of 5 to 15 mT. The long magnetic body is preferably made of magnetically annealed permalloy. The magnet is preferably made of a neodymium magnet or a samarium-cobalt magnet with a residual magnetic flux density of 1 T or more.

The linear position sensor of the present invention is preferably configured such that a long magnetic body is housed inside a long pipe, the ends of the long pipe are fixed and supported by a frame, the magnet is supported by a slider, and the slider is arranged movably along the long pipe within the frame, and the slider moves between both ends of the long magnetic body as the detection target moves or increases or decreases, thereby detecting the magnetic flux of the magnet induced by the long magnetic body with a magnetic detection component, and the end of the long magnetic body and the magnetic detection element are biased to maintain a predetermined constant distance by the elasticity of the elastic part. Preferably, the magnetic detection element is incorporated in the magnetic detection component, and when the slider is arranged at a position furthest from the magnetic detection element of the magnetic detection component, the magnetic flux density generated by the magnet at the position of the magnetic detection element is 1 mT or more. This linear position sensor is typically used as a level sensor.

According to the present invention, the end of the long magnetic body is placed facing the magnetic detection component, and a magnet is movably placed between both ends of the long magnetic body, so that the magnetic flux of the magnet can be induced by the long magnetic body and detected by the magnetic detection element, and the detection range can be expanded according to the length of the long magnetic body.

The long magnetic body is supported by a frame that contains a magnet, so even if the long magnetic body is long, it can be stably positioned relative to the magnetic detection component. Therefore, even if the detection range is wide, the position of the magnet can be detected with high accuracy by the magnetic detection element of the magnetic detection component.

In particular, the frame is provided with an elastic portion that biases the end of the long magnetic body and the magnetic detection element of the magnetic detection component to maintain a predetermined distance. This means that even if thermal expansion or contraction occurs in the frame, the distance between the end of the long magnetic body and the magnetic detection element can be kept constant, improving detection accuracy.

Therefore, the present invention can provide a linear position sensor and a level sensor that can provide a wide detection range, are less susceptible to variations in detection accuracy even when the conditions of use change, and are capable of accurate and stable detection.

In the linear position sensor of this invention, if two magnetic detection components are provided facing each end of the long magnetic body and both ends of the long magnetic body are positioned facing each magnetic detection component, magnetic flux can be detected at both ends of the long magnetic body, allowing a longer long magnetic body to be used and resulting in a wider detection range.

If the elastic portion is biased to maintain a predetermined distance between both ends of the long magnetic body and each magnetic detection element, even if magnetic detection components are disposed at both ends of the long magnetic body, the distance between the magnetic detection element of each magnetic detection component and the ends of the long magnetic body can be kept constant when thermal expansion or contraction occurs in the frame portion.

In the linear position sensor of this invention, if the frame has a receiving portion that supports the end of the long magnetic body in a predetermined position, the end of the long magnetic body is prevented from shifting sideways relative to the magnetic detection component. In addition, a gap can be provided between the long magnetic body and the magnetic detection element, which prevents the magnetic detection element from being loaded with magnetic flux that exceeds the detection range from the magnet, allowing for stable and accurate detection.

In the linear position sensor of this invention, if a long pipe is provided to house the long magnetic body and the long pipe is fixed to the frame in a non-jointed state with the long magnetic body, the long magnetic body is more likely to undergo slight displacement, and thermal deformation and vibrations that occur in the frame are further prevented from being directly transmitted.

1 is a perspective view of a level sensor according to a first embodiment of the present invention; 1 is a vertical sectional view of a level sensor according to a first embodiment of the present invention; FIG. 3 is an enlarged cross-sectional view showing the AA cross section of FIG. 2. 4 is an enlarged vertical cross-sectional view of a base portion of a level sensor according to an embodiment of the present invention. 1 is a vertical cross-section of the top side of a level sensor according to an embodiment of the present invention. FIG. 13 is a vertical cross-sectional view of the top side showing a modified example of the level sensor according to the first embodiment, illustrating an example in which a compression spring is used for the spring portion. FIG. 13 is a vertical cross-sectional view of the top side showing a modified example of the level sensor according to the first embodiment, illustrating an example in which an elastic resin molded body is used for the spring portion. FIG. 6 is a vertical sectional view of a level sensor according to a second embodiment of the present invention. FIG. 11 is a vertical sectional view of a level sensor according to a third embodiment of the present invention. FIG. 13 is a vertical cross-sectional view of a level sensor according to a modified example of the third embodiment. FIG. 10 is a vertical sectional view of a level sensor according to a fourth embodiment of the present invention. FIG. 13 is a vertical cross-sectional view of a level sensor according to a fifth embodiment of the present invention. FIG. 8B is a partially enlarged view of FIG. 8A. 1 is a graph showing the results of Example 1. FIG. 2 is a diagram showing a magnetization curve of a long magnetic body made of PB Permalloy used in Example 1. FIG. 2 is a diagram showing a magnetization curve of a long magnetic body made of PC Permalloy used in Example 1. FIG. 2 is a diagram showing a magnetization curve of a long magnetic body made of permendur used in Example 1. FIG. 2 is a diagram showing a magnetization curve of a long magnetic body made of soft ferrite used in Example 1. 1 is a graph showing the results of Example 2 and Reference Example 1. 1 is a graph showing the results of Example 3. 1 is a graph showing the results of Examples 4 to 6. FIG. 13 is a diagram showing the magnetic flux density of the level sensor of the seventh embodiment. FIG. 13 is a diagram showing an output voltage of the level sensor of the seventh embodiment. FIG. 23 is a diagram showing the output voltage of the level sensor of the eighth embodiment. 1 is a graph showing the results of Reference Example 2. 1 is a graph showing the results of Reference Example 3.

Below, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, as shown in Figures 1 and 2, a linear position sensor will be described as a level sensor for detecting the liquid level disposed in a container.

The level sensor 10 basically comprises a magnetic detection component 18, an elongated magnetic body 12, a magnet 15, and a frame 20. The magnetic detection component 18 is configured with a magnetic sensor 18c containing a magnetic detection element 18d attached to a substrate 27. The elongated magnetic body 12 is arranged facing the magnetic sensor 18c of the magnetic detection component 18 with its upper end facing the magnetic sensor 18c in Figure 1. The magnet 15 is arranged surrounding the elongated magnetic body 12 and is arranged so as to be movable between both ends of the elongated magnetic body 12. The frame 20 supports the elongated magnetic body 12 with respect to the magnetic detection component 18, and contains the magnet 15. Specifically, the frame 20 includes a base portion 11 that houses and fixes the magnetic detection component 18, a rigid frame portion 21 that is fixed to the base portion 11 at one end and supports the lower end of the long magnetic body 12 at the other end, and an elastic portion 23 that is disposed at one or the other end of the rigid frame portion 21 and biases the end of the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18 to maintain a predetermined distance.

The long magnetic body 12 is housed inside the long pipe 29 to form the stem portion 13. When housed in the long pipe 29, the top end of the long magnetic body 12 is disposed opposite the magnetic detection component 18 of the base portion 11 and is biased by the elasticity of the elastic portion 23.

The magnet 15 is supported by a float 16 that acts as a slider. The float 16 is movably surrounded by a rigid frame 21 and is arranged to be movable along the stem 13 and the long magnetic body 12. As the float 16 moves between both ends of the long magnetic body 12 in response to the movement of the detection target, such as movement or increase or decrease in weight, the magnetic flux of the magnet 15 induced by the long magnetic body 12 is detected by the magnetic detection component 18.

As shown in Figures 2 and 3B, the base portion 11 has a resin housing 25 formed into various shapes, and the magnetic detection component 18 is fixed inside the housing 25. In this embodiment, the base portion 11 is sealed with resin, with the magnetic detection component 18 housed inside the housing 25. The output 18a of the magnetic detection component 18 is drawn to the outside from the board 27 as a conductor. The base portion 11 is provided with a flange portion 11a for mounting, and the stem portion 13 and rigid frame portion 21 are provided to protrude from the flange portion 11a, and the output 18a for connecting to a control unit (not shown) is drawn liquid-tightly from the board 27 to the outside of the flange portion 11a by a connector 18b.

The housing 25 of the base portion 11 is provided with a receiving portion 23b that fits one end of the long magnetic body 12 to support it in a predetermined position. The receiving portion 23b is provided in a concave shape on the wall surface of the housing 25. The receiving portion 23b has a shape corresponding to the shape of the end of the long magnetic body 12. When the tip of the long magnetic body 12 is inserted into the receiving portion 23b and fitted, the tip of the long magnetic body 12 abuts the bottom of the receiving portion 23b and is arranged without any positional deviation in the horizontal direction, i.e., in the direction perpendicular to the insertion direction. The receiving portion 23b may be opened through and arranged so that the upper end of the long magnetic body 12 abuts against the magnetic sensor 18c of the magnetic detection component 18. The receiving portion 23b may also be provided with a bottom wall, and air or resin may be present between the bottom wall of the receiving portion 23b and the magnetic sensor 18c of the magnetic detection component 18. This allows the upper end of the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18 to be positioned facing each other at a specified distance.

By having air or resin between the end of the long magnetic body 12 and the magnetic sensor 18c of the magnetic detection component 18, the tip of the long magnetic body 12 can be arranged apart from the surface of the magnetic sensor 18c of the magnetic detection component 18 without directly contacting the surface. This prevents the end of the long magnetic body 12 from receiving excessive stress, and protects the magnetic sensor 18c of the magnetic detection component 18. At the same time, by providing a constant gap between the tip of the long magnetic body 12 and the magnetic detection element 18d contained in the magnetic sensor 18c, it is possible to prevent the magnetic detection element 18d from being loaded with a magnetic flux that exceeds the detection range when the magnet 15 of the float 16 approaches the magnetic detection element 18d, and to suppress variation in the magnetic flux detected by the magnetic detection component 18.

The magnetic detection element 18d of the magnetic sensor 18c can be an electromagnetic conversion element, and specifically, a Hall element is preferable. If the linear position sensor is a liquid level sensor or a level sensor such as a liquid level sensor, a linear Hall IC or the like can be preferably used as the magnetic sensor 18c incorporating the magnetic detection element 18d. As will be described later, if the linearity between the liquid level and the linear Hall IC is not good, a programmable Hall IC can be used. The programmable Hall IC includes an EEPROM element or the like and has the function of correcting the liquid level and the output of the linear Hall IC to a straight line. In this embodiment, a programmable Hall IC is used that can linearize the magnetic flux change using an approximation formula and output it.

As shown in Figures 2 and 3A, the stem portion 13 has a long pipe 29 and a long magnetic body 12. One end (also called the upper end) of the long pipe 29 is fixed to the base portion 11, and the other end (also called the lower end) is fixed to the rigid frame portion 21. The long magnetic body 12 is placed along the stem portion 13 while being housed within the long pipe 29, and is supported in a non-jointed state with the long pipe 29.

The long pipe 29 is formed of, for example, resin, etc., to the same length as the long magnetic body 12, and has a generally cylindrical shape with a substantially constant cross section. The stem portion 13 is provided with a detection area of at least 30 mm or more, preferably 40 mm or more, and particularly preferably 100 mm or more, in which the float 16 can move. Although stoppers or the like may be placed at each end to divide the detection area, in this embodiment, the detection area is defined by the entire length between the position where the float 16 abuts against the base portion 11 and the position where it abuts against the inner end of the rigid frame portion 21. As shown in Figures 2 and 3C, a plurality of ribs 29a extending in the axial direction are provided on the outer circumferential surface of the long pipe 29. This is to reduce sliding resistance when the float 16 and the long pipe 29 come into contact. The spaces between the ribs may be closed or may be open, penetrating from the inside to the outside.

The internal support pieces 23c are provided on the inside of the long pipe 29 at multiple positions surrounding the long magnetic body 12, protruding so as to abut the outer periphery of the long magnetic body 12 in a non-bonded state. The multiple internal support pieces 23c position the long magnetic body 12 at a predetermined radial position, such as the center of the long pipe 29, while allowing it to move in the longitudinal direction, and elastically support it in the radial direction.

The annular stem portion 13 is inserted into the through hole 16a of the float 16. When the long pipe 29 of the stem portion 13 is inserted into the through hole 16a, the float 16 can slide smoothly in the axial direction of the stem portion 13 without excessive rattling in the radial direction relative to the stem portion 13. There are no particular limitations on the shape and material of the float 16, as long as it floats on the surface of the liquid to be detected while supporting the magnet 15.

The magnet 15 supported by the float 16 is preferably a strong magnet such as neodymium, with both poles arranged along the axial direction of the through hole 16a of the float 16, for example formed in a ring shape surrounding the through hole 16a. The magnet may be formed in one or more chunks or rods extending along the axial direction of the through hole 16a.

For example, when the float 16 is positioned at the farthest position from the magnetic detection element 18d of the magnetic detection component 18 in the detection area, the magnetic flux density at the position of the magnetic detection element 18d obtained by the magnet 15 is preferably 1 mT or more.

The long magnetic body 12 induces the magnetic flux of the magnet 15 supported by the float 16 to the magnetic detection element 18d of the magnetic detection component 18, and is made of a soft magnetic material with, for example, a saturation magnetic flux density of 0.65 T or more, a coercive force of 12 A/m or less, and a magnetic permeability of 3000 or more at a magnetic flux density of 5 to 15 mT. The reason why the coercive force of the long magnetic body 12 is set to 12 A/m or less is to prevent the detection position from shifting when the liquid level rises and falls, and the reason why the saturation magnetic flux density of the long magnetic body 12 is set to 0.65 T or more and the magnetic permeability of 3000 or more at a magnetic flux density of 5 to 15 mT is to expand the detection range.

The deviation of the detection position depends on the coercive force of the long magnetic body 12, or what is called hysteresis, and in order to make deviation of the detection position less likely to occur, the coercive force is set to 12 A/m or less, and more preferably 4 A/m or less. If the coercive force is 4 A/m or less, there is almost no deviation of the detection position when the detection range is about 100 mm. If the coercive force is 20 A/m, the deviation of the detection position is, for example, about 10% when the detection range is about 100 mm, and deviation of the detection position occurs, which is undesirable. If the coercive force is 20 A/m or more, the deviation of the detection position becomes larger, but it can be used when the deviation of the detection position is not a problem, for example, when detecting liquid levels at zero, intermediate, or maximum.

In order to expand the detection range of the level sensor 10, it is necessary to increase the amount of magnetic flux density generated at the position of the magnetic detection element 18d of the magnetic detection component 18. As a result of examining the soft magnetic material used for the long magnetic body 12 using electromagnetic field analysis software, it was found that in order to expand the detection range, it is effective for the soft magnetic material used for the long magnetic body 12 to have a sufficiently large saturation magnetic flux density and to have sufficient magnetic permeability near the minimum value of magnetic flux density that can be detected by the magnetic detection element 18d even if the initial permeability is small. The magnetic permeability of the long magnetic body 12 was calculated when a surface magnetic flux density of about 1 to 3 mT was generated at the end position of the magnetic detection element 18d when the detection range was about 100 mm. Specifically, the magnetic permeability was calculated when the surface magnetic flux density generated at the end of the long magnetic body 12 was 5 to 15 mT. This revealed that in order to expand the detection range, the soft magnetic material used for the long magnetic body 12 must have a saturation magnetic flux density of 0.65 T or more and a magnetic permeability of 3000 or more at a magnetic flux density of 5 to 15 mT. Soft magnetic materials that meet this condition include, for example, PB permalloy, PC permalloy, and permendur. As will be described later, it was difficult to expand the detection range to about 100 mm with soft ferrite.

The long magnetic body 12 may be PB permalloy with magnetic grade 06 having DC magnetic properties conforming to JIS C2531:1999, PC permalloy with magnetic grade 30, iron-nickel magnetic materials with permeability and saturation magnetic flux density equal to or higher than these permalloys and coercivity equal to or lower than these permalloys, sendust, amorphous magnetic materials, nanocrystalline magnetic materials, etc. PB permalloy may be a composition of 42-49% Ni by mass, the remainder being Fe. PC permalloy may be a composition of 75-78% Ni by mass, 2-3% Cr by mass, 4-6% Cu by mass, the remainder being Fe, 75-80% Ni by mass, 1-6% Cu by mass, 3.5-6% Mo by mass, the remainder being Fe, 79-82% Ni by mass, 3.5-6% Mo by mass, the remainder being Fe.

The long magnetic body 12 can be in a variety of shapes, including cylindrical, prismatic, plate-like, and strip-like shapes, but a cylindrical shape allows for a larger cross-sectional area, which increases the saturation magnetic flux density and the magnetic flux density that reaches the magnetic detection element 18d.

The end of the long magnetic body 12 may have a tapered shape such as a spherical surface, a tapered surface, or a conical surface. In this way, the magnetic flux is concentrated in a narrow area at the end, so the peak of the magnetic flux density that reaches the magnetic detection element 18d can be increased.

2, 3B, and 3C, the rigid frame portion 21 has a plurality of frame plates 21a fixed at one end to the base portion 11 and arranged along the long magnetic body 12 surrounding the periphery of the float 16, and a connecting portion 21b to which the other end sides of the plurality of frame plates 21a are connected, and the other end side of the stem portion 13 is supported by the connecting portion 21b. The frame plates 21a are arranged in at least two directions, preferably three or more directions, around the periphery of the float 16, and each is formed into a plate shape that is more rigid than the long pipe 29. The plurality of frame plates 21a may be connected together on the base portion 11 side. Each frame plate 21a is arranged at a position spaced apart from the long pipe 29, except for the connecting portion 21b. Although not particularly limited, each frame plate 21a may be arranged so that the distance between the frame plate 21a and the long pipe 29 is, for example, two to six times the diameter of the long pipe 29. In this embodiment, the frame plate 21a is formed with an arc-shaped cross section that is wider than the diameter of the long pipe 29 and thicker than the long pipe 29, and is arranged approximately parallel to the long pipe 29 in each of the four directions around the float 16, supporting the connecting part 21b so that it cannot be displaced.

As shown in FIG. 3C, the elastic portion 23 presses the long magnetic body 12 against the base portion 11 by elastic force. In this embodiment, the long pipe 29 is fitted and fixed in a groove or recess provided in the housing 25 of the base portion 11 and the connecting portion 21b of the rigid frame portion 21, and the long magnetic body 12 housed in this long pipe 29 is pressed by elastic force. As the elastic portion 23 in this embodiment, a spring portion 23a is provided in the connecting portion 21b of the rigid frame portion 21, and it urges one end of the long magnetic body 12 against the magnetic detection component 18, thereby urging the other end of the long magnetic body 12.

The spring portion 23a is composed of an elastically deformable leaf spring 24a provided at the connecting portion 21b of the rigid frame portion 21. For example, if the long pipe 29 or the rigid frame portion 21 is made of resin, the spring portion 23a can be formed integrally with it as long as the desired elastic force is obtained. The spring portion 23a is not particularly limited to the leaf spring 24a shown in FIG. 3C, but may be a compression spring 24b consisting of a coil spring shown in FIG. 4A. This compression spring 24b is disposed between the connecting portion 21b of the rigid frame portion 21 and the other end of the long magnetic body 12 to bias the long magnetic body 12 in the longitudinal direction. Also, for example, as shown in FIG. 4B, the spring portion 23a may be formed of an elastic resin molded body 24c. The resin molded body 24c is integrally provided with a pressure applying portion 24d that is disposed at the connecting portion 21b of the rigid frame portion 21 and applies pressure to the long magnetic body 12, and a receiving portion 24e into which the other end of the long magnetic body 12 is inserted. Alternatively, a coil spring or a coned disc spring may be used, and various materials such as elastic resins and elastic non-magnetic metal materials may also be used.

If such a spring portion 23a is used to bias the long magnetic body 12 in a direction pressing it against the magnetic detection component 18, the end of the long magnetic body 12 can be pressed against the magnetic detection component 18 with sufficient pressure even if thermal expansion or contraction occurs in the long pipe 29 or the rigid frame portion 21, and the distance between the end of the long magnetic body 12 and the magnetic detection element 18d can be kept constant with high precision.

The level sensor 10 described above is attached to the bottom wall or lid wall of a liquid storage unit such as a tank using the flange portion 11a, and is used with the stem portion 13 positioned vertically, for example. The flange portion 11a is configured with a packing or the like to provide a liquid-tight structure.

When liquid accumulates in the liquid storage section, the float 16 rises and falls according to the liquid level, and the magnetic flux of the magnet 15 supported by the float 16 is induced into the long magnetic body 12 and detected by the magnetic detection element 18d arranged at the end of the long magnetic body 12, and a detection signal corresponding to the magnetic flux is transmitted from the substrate 27 to the outside. At this time, the magnetic flux corresponding to the position of the magnet 15 can be detected throughout the entire detection area of the long magnetic body 12, so the liquid level can be detected continuously throughout the entire detection area. In particular, in this embodiment, the liquid is linearized and detected by the magnetic detection component 18, so a detection signal corresponding to the liquid level is obtained.

The long magnetic body 12 is made of a soft magnetic material with a saturation magnetic flux density of 0.65 T or more, a coercive force of 12 A/m or less, and a magnetic permeability of 3000 or more at a magnetic flux density of 5 to 15 mT, which allows the detection area to be long and prevents discrepancies between when the liquid level rises and when it falls. As a result, it is possible to detect the displacement of the liquid level in either direction continuously and with high accuracy over a wide range. Here, the saturation magnetic flux density, magnetic permeability, and coercive force are values obtained using the measurement method described in JISC2531:1999 Iron-nickel soft magnetic materials.

In the level sensor 10 of this embodiment, the magnetic detection component 18 is fixed to the base portion 11, the stem portion 13 having the long magnetic body 12 is provided so as to protrude from the base portion 11, and the magnetic detection component 18 is disposed at one end of the long magnetic body 12. Therefore, the end of the long magnetic body 12 is disposed facing the magnetic detection element 18d attached to the substrate 27, and the magnet 15 is disposed movably between both ends of the long magnetic body 12, so that the magnetic flux of the magnet 15 can be induced by the long magnetic body 12 and detected by the magnetic detection component 18, and the detection range can be widened according to the length of the long magnetic body 12.

In the present invention, the long magnetic body 12 can be formed long. As a result, even if the long magnetic body 12 has a large protrusion amount from the base portion 11 of the stem portion 13, the other end of the stem portion 13 is fixed and supported by the rigid frame portion 21 fixed to the base portion 11, so the stem portion 13 can be firmly supported relative to the base portion 11. Therefore, even if vibration, acceleration, etc. act on the linear position sensor, the long magnetic body 12 can be stably positioned relative to the magnetic detection component 18. Therefore, it is possible to prevent fluctuations in the angle and position of the long magnetic body 12 relative to the magnetic detection component 18, and the magnetic detection component 18 can accurately detect the position of the magnet 15 of the float 16. According to the present invention, the detection range of the level sensor 10 can be widened, and it is possible to reduce the occurrence of variations in detection accuracy even if the usage conditions change.

This level sensor 10 is provided with an elastic section 23 that elastically supports the long magnetic body 12, and the elasticity of the elastic section 23 supports the long magnetic body 12 so that it can be displaced relative to the rigid frame section 21. This prevents thermal deformation and vibrations that occur in the rigid frame section 21 from being directly transmitted to the long magnetic body 12, and allows the magnetic detection component 18 to detect the magnetic flux induced by the long magnetic body 12 with high accuracy and stability.

In the present invention, an elastic portion 23 is provided on the frame 20, and the elastic portion 23 biases the other end of the long magnetic body 12 so that a predetermined distance is maintained between one end of the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18. Therefore, even if thermal expansion or contraction occurs in the long pipe 29 or the rigid frame 21, one end of the long magnetic body 12 can be pressed toward the magnetic detection component 18 with an appropriate pressure, and the distance between the end of the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18 is kept constant, improving detection accuracy.

In this level sensor 10, the elastic portion 23 has a receiving portion 23b arranged between one end of the long magnetic body 12 and the magnetic detection component 18, so that the long magnetic body 12 does not directly contact the surface of the magnetic sensor 18c of the magnetic detection component 18, but is stably separated at a close position. Therefore, the magnetic sensor 18c can be protected without receiving excessive stress from the end of the long magnetic body 12. By providing a gap between the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18, it is possible to prevent the magnetic detection element 18d from being loaded with a magnetic flux that exceeds the detection range when the magnet 15 of the float 16 is closest to the magnetic detection component 18, and a stable detection state can be obtained.

In this level sensor 10, the stem portion 13 has a long pipe 29 that houses the long magnetic body 12 and slidably supports the float 16, and the long magnetic body 12 is supported in a non-jointed state with the long pipe 29 and fixed to the frame body 20. This makes it easier for the long magnetic body 12 to be slightly displaced, and further prevents thermal deformation and vibrations that occur in the base portion 11, rigid frame portion 21, long pipe 29, etc. from being directly transmitted to the long magnetic body 12.

[Second embodiment]
5 shows an example of the level sensor 10 of the second embodiment. The level sensor 10 includes two magnetic detection components 18x and 18y, and each end of the long magnetic body 12 is arranged to face each of the magnetic detection components 18x and 18y. In the second embodiment, the level sensor 10 includes a first magnetic detection component 18x having a magnetic detection sensor 18c attached to a first board 27x and a second magnetic detection component 18y having a magnetic detection sensor 18c attached to a second board 27y, facing both ends of the long magnetic body 12, and the movable range of the float 16 is set to 100 mm or more. In detail, one end side of the level sensor 10 and the stem portion 13 are the same as those of the first embodiment, the first magnetic detection component 18x is arranged in the housing 25 of the base portion 11, and the long magnetic body 12 is accommodated in the long pipe 29. A resin housing 30 is provided on the connecting portion 21b of the rigid frame portion 21, which is the other end side of the level sensor 10. The housing 30 is arranged between the connecting portion 21b of the rigid frame portion 21 and the other end of the elongated magnetic body 12, and the housing 30 is urged toward the other end of the elongated magnetic body 12 by a compression spring 32 as an elastic portion 23 arranged in the connecting portion 21b.

The housing 30 contains a second magnetic detection component 18y, similar to the one end side of the level sensor 10. The first and second boards 27x, 27y arranged on both ends of the level sensor 10 are connected by a connection harness 31. Therefore, the magnetic flux of the magnet 15 of the float 16 can be detected on both ends of the long magnetic body 12, and the detection signal detected by the first and second magnetic detection components 18x, 18y on both ends is transmitted to the outside from the output 18b of the connector 18a on one end side.

In the second embodiment, the elasticity of the compression spring 32 biases the elongated magnetic body 12 towards the housing 25 on one side via the housing 30. The second board 27y in the second magnetic detection component 18y is pressed by the compression spring 32, and biases the magnetic detection element 18d of the second magnetic detection component 18y so as to maintain a predetermined distance from the end of the elongated magnetic body 12. The compression spring 32 also biases the housing 30, and the second board 27y in the second magnetic detection component 18y is pressed, thereby biasing the elongated magnetic body 12, and the end of the elongated magnetic body 12 is biased so as to maintain a predetermined distance from the magnetic detection element 18d of the first magnetic detection component 18x. In this way, the distance between one end of the long magnetic body 12 and the first magnetic detection component 18x of the housing 25 can be kept constant, while the distance between the other end of the long magnetic body 12 and the second magnetic detection component 18y of the housing 30 can be kept constant, thereby improving detection accuracy.

A receiving portion 33 having a shape corresponding to the shape of the end of the long magnetic body 12 is provided on the wall surface of the housing 30 facing the long magnetic body 12. When the long magnetic body 12 is inserted into the receiving portion 33 and engaged, the tip of the long magnetic body 12 abuts against the bottom of the receiving portion 33 and is positioned without any positional misalignment in the horizontal direction, i.e., in the direction perpendicular to the insertion direction. The rest is the same as in the first embodiment.

This level sensor 10 also provides the same effect as the first embodiment. Moreover, since the long magnetic body 12 has the first magnetic detection component 18x and the second magnetic detection component 18y at both ends, no matter which end of the movable range the float 16 moves to, it can be detected with high accuracy by either of the magnetic detection components 18x, 18y. Therefore, even if the long magnetic body 12 is so long that the magnetic detection components 18x, 18y at either end cannot detect the middle of the long magnetic body 12 with high accuracy, it can be detected with high accuracy near both ends, i.e., near the lower and upper ends of the movable range of the float 16.

[Third embodiment]
6A shows a level sensor 10 according to a third embodiment. This level sensor 10 is similar to the first embodiment, except for the structure of the frame 20. This frame 20 is divided into two parts in the vertical direction, i.e., in the longitudinal direction of the long magnetic body 12, and connected by a connection part 35. In detail, the frame 20 is composed of a base part 11, a rigid frame part 21 that is connected to the base part 11 at one end and supports the other end of the long magnetic body 12 at the other end, a connection part 35 that connects the upper end side of the rigid frame part 21 to the base part 11, and an elastic part 23 arranged in the connection part 35.

As in the first embodiment, the base portion 11 has the magnetic detection component 18 housed and fixed in the housing 25. At a number of positions corresponding to each frame plate 21a of the rigid frame portion 21, connection protrusions 36 for connecting each frame plate 21a are provided, bent inwardly and having a generally L-shaped cross section.

The rigid frame portion 21 is connected to the base portion 11 via the connection portion 35. The rigid frame portion 21 integrally comprises a plurality of frame plates 21a extending along the long magnetic body 12, a connection piece 21c bent outward in a generally L-shape at one end of each frame plate 21a and connected to the base portion 11, a connection pin 21d protruding from each connection piece 21c in a direction along the long magnetic body 12, and a connection portion 21b provided on the other end of the plurality of frame plates 21a to connect them to each other.

In the connection portion 35, the connection pieces 21c of each frame plate 21a of the rigid frame portion 21 are arranged between the housing 25 of the base portion 11 and the connection protrusion 36, and the connection pins 21d protruding from each connection piece 21c are inserted into the through holes 21e of the connection protrusion 36. The elastic portion 23 is made of a compression spring attached around each connection pin 21d, and urges the connection protrusion 36 and the connection piece 21c of the frame plate 21a in a direction to separate them from each other. The elastic portion 23 urges each connection piece 21c of the rigid frame portion 21 toward the housing 25, so that the entire rigid frame portion 21 is urged toward the housing 25. Therefore, the long magnetic body 12 of the stem portion 13 supported by the connecting portion 21b of the rigid frame portion 21 can be pressed toward the housing 25. As a result, the upper end of the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18 are urged to maintain a predetermined distance.

This level sensor 10 can achieve the same effects as the first embodiment.

[Modification of the third embodiment]
Fig. 6B shows a modified example of the third embodiment. The level sensor 10 of this modified example has the same configuration as the level sensor 10 of the third embodiment shown in Fig. 6A, except that the structure of the frame body 20 is different and the first and second magnetic detection components 18x and 18y are arranged on both ends of the long magnetic body 12. That is, the base portion 11 accommodating the first magnetic detection component 18x is provided on one end of the frame body 20 as in Fig. 6A, and the second board 27y of the second magnetic detection component 18y is fixed by a fixing member 21k to the connecting portion 21b on the other end side of the rigid frame portion 21. The first and second boards 27x and 27y are connected by a connection harness (not shown), and the detection signals detected by both magnetic detection components 18x and 18y are transmitted from the connector 18b. In this modification, since the second magnetic detection component 18y is fixed to the rigid frame portion 21, the elastic portion 23 disposed in the connection portion 35 biases the second magnetic detection component 18y together with the rigid frame portion 21 toward the housing 25. As a result, both ends of the long magnetic body 12 and the magnetic detection elements 18d, 18d of each magnetic detection component 18, 18y are biased to maintain a predetermined distance. Even in this modification, the same effects as those in the first embodiment can be obtained. Moreover, as in the second embodiment, since the long magnetic body 12 has the magnetic detection components 18x, 18y at both ends, accurate detection is possible even if the length of the long magnetic body 12 is increased.

[Fourth embodiment]
7 shows a level sensor 10 according to a fourth embodiment. This level sensor 10 is similar to the level sensor 10 according to the first embodiment, except for the structure of the frame 20. In this frame 20, the rigid frame portion 21 is divided into two in the vertical direction, i.e., in the longitudinal direction of the long magnetic body 12.

The rigid frame portion 21 has multiple frame plates 21a that are fixed at one end to the flange portion 11a of the base portion 11 and extend along the long magnetic body 12, and a connecting portion 21b to which the other ends of the multiple frame plates 21a are connected. Each frame plate 21a is divided at a dividing portion 21f, and the frame piece 21g on the base portion 11 side and the frame piece 21g on the connecting portion 21b side are connected by a connecting portion 35 of the dividing portion 21f. An elastic portion 23 is disposed in the connecting portion 35, and the frame pieces 21g are connected via the elastic portion 35.

In the connection portion 35, connection pieces 21c bent outward in a generally L-shaped cross section are provided facing each other at the end of the frame piece 21g on the base portion 11 side and the end of the frame piece 21g on the connecting portion 21b side. One of the facing connection pieces 21c is provided with a connection pin 21d that protrudes in a direction along the elongated magnetic body 12, and the other is provided with a through hole 21e through which the connection pin 21d can be inserted. In this connection portion 35, the connection pieces 21c are faced each other and connected with the connection pin 21d inserted through the through hole 21e.

The elastic portion 23 is made of a tension spring attached around each connection pin 21d, and biases the connection pieces 21c in a direction to bring them closer together. The elastic portion 23 pulls the frame piece 21g on the connecting portion 21b side toward the frame piece 21g on the base portion 11 side, thereby biasing the connecting portion 21b of the rigid frame portion 21 toward the housing 25 side of the base portion 11. This allows the long magnetic body 12 of the stem portion 13, which is fixed and supported by the connecting portion 21b of the rigid frame portion 21, to be pressed toward the housing 25 side, and the end of the long magnetic body 12 and the magnetic detection component 18 can be biased so that they always abut or maintain a predetermined distance from each other.

This level sensor 10 also provides the same effect as the first embodiment. In this embodiment, as in the modified example of the third embodiment, it is possible to place magnetic detection components 18 on both ends of the long magnetic body 12.

[Fifth embodiment]
The level sensor 10 of the fifth embodiment is similar to the fourth embodiment except for the structure of the frame body 20. Figures 8A and 8B show the level sensor 10 of the fifth embodiment. In the frame body 20 of this embodiment, the rigid frame portion 21 is also divided into two in the vertical direction, i.e., in the longitudinal direction of the long magnetic body 12.

The rigid frame portion 21 has multiple frame plates 21a that are fixed at one end to the flange portion 11a of the base portion 11 and extend along the long magnetic body 12, and a connecting portion 21b to which the other ends of the multiple frame plates 21a are connected. Each frame plate 21a is divided at a dividing portion 21f near the connecting portion 21b, and the frame piece 21g on the base portion 11 side and the frame piece 21g on the connecting portion 21b side are connected by an elastic connecting portion 35a.

In the elastic connection portion 35, a cylindrical protrusion 21h that protrudes outward is provided on one of the ends of the frame piece 21g on the base portion 11 side and the end of the frame piece 21g on the connecting portion 21b side, and a clip 21i that elastically clamps the cylindrical protrusion 21h is provided on the other. The clip 21i protrudes from the frame piece 21g and is formed integrally with the frame piece 21g. The clip 21i has a pair of elastic claws 21j that are arranged close to each other and opposite each other, and the cylindrical protrusion 21h can be clamped between the elastic claws 21j by elastic force.

When the cylindrical projection 21h is clamped between the elastic claws 21j, an elastic force acts in the tensile direction between the cylindrical projection 21h and the clip 21i due to the angle of the contact surface between the pair of elastic claws 21j and the cylindrical projection 21h, the frame piece 21g on the connecting part 21b side is pulled toward the frame piece 21g on the base part 11 side, and the connecting part 21b of the rigid frame part 21 is biased toward the housing 25 side of the base part 11. This allows the long magnetic body 12 of the stem part 13 supported and fixed to the rigid frame part 21 to be pressed toward the housing 25 side, and the end of the long magnetic body 12 and the magnetic detection component 18 are biased so that they always abut or maintain a predetermined distance.

This level sensor 10 can achieve the same effects as the first embodiment. Also, as in the modified example of the third embodiment, it is possible to place magnetic detection components 18 on both ends of the long magnetic body 12.

The first to fifth embodiments described above can be modified as appropriate within the scope of the present invention. For example, in the above embodiments, an example was described in which the long magnetic body 12 was housed in the long pipe 29 as the stem portion 13, but the stem portion 13 made of the long magnetic body 12 may be supported by the base portion 11 or the rigid frame portion 21 without using the long pipe 29. In the above embodiments, it is preferable to use non-magnetic materials except for the long magnetic body 12 and the magnet 15. Examples of non-magnetic materials include soft resins and non-magnetic metal materials.

Examples and reference examples of the present invention will be described below.
[Example 1]
The magnetic flux density at the position of the magnetic detection element 18d was calculated by magnetic simulation using the long magnetic body 12 having a wire shape of 0.6 mm in diameter and 150 mm in length and made of PB permalloy (manufactured by Hitachi Metals, Ltd., YEP-B, initial permeability: 6000, saturation magnetic flux density: 1.4 T), PC permalloy (manufactured by Hitachi Metals, Ltd., YEP-C, initial permeability: 200,000, saturation magnetic flux density: 0.7 T), permendur (manufactured by Hitachi Metals, Ltd., YEP-2V, initial permeability: 840, saturation magnetic flux density: 2.45 T), and soft ferrite (manufactured by JFE Ferrite Corporation, MBT2, initial permeability: 3300, saturation magnetic flux density: 0.53 T). The magnet 15 used was an anisotropic ferrite magnet with a residual magnetic flux density of 395 mT, ring-shaped with an outer diameter of 15 mm, an inner diameter of 10 mm, and a thickness of 3 mm, and magnetized in the thickness direction.

The magnetic flux density at the position of the magnetic detection element 18d was calculated by placing the long magnetic body 12 at the center of the ring-shaped magnet 15 and simulating the magnetic flux generated according to the distance between the magnet and the end using electromagnetic field analysis software (JMAG) from JSOL Corporation.

The calculation results of the magnetic flux density in Example 1 are shown in Figure 9. The horizontal axis of Figure 9 is the distance (mm) between the long magnetic body 12 and the magnet 15, and the vertical axis is the magnetic flux density (mT) at the position of the magnetic detection element 18d. In Figure 9, PB permalloy, PC permalloy, and permendur generate a magnetic flux density of 1.5 mT or more even at a magnet distance of 110 mm, while soft ferrite has a small magnetic flux density of 1 mT or less.

The surface magnetic flux density of the end of the long magnetic body 12 at the magnet position when a magnetic flux density of 2 mT was generated at the magnetic detection element 18d was calculated to be 10 mT. The magnetic permeability was calculated from the surface magnetic flux density based on the magnetization curve of each material. Figures 10A to 10D show the magnetization curves of the long magnetic body 12 used in Example 1. The long magnetic bodies 12 are shown in Figure 10A for PB permalloy, in Figure 10B for PC permalloy, in Figure 10C for permendur, and in Figure 10D for soft ferrite. The magnetic permeability at magnetic flux densities of 5 to 15 mT calculated from the magnetization curves of Figures 10A to 10D was 6,600 for PB permalloy, 37,000 for PC permalloy, 4,000 for permendur, and 3,300 for soft ferrite.

From these, it was found that in order to increase the amount of magnetic flux density generated at the position of the magnetic detection element 18d, the soft magnetic material used for the long magnetic body 12 needs to have a sufficiently large saturation magnetic flux density, and even if the initial permeability is small, it needs to have sufficient permeability near the minimum value of the magnetic flux density detected by the magnetic detection element 18d. Soft magnetic materials that meet this condition have a saturation magnetic flux density of 0.65T or more and a permeability of 3000 or more at a magnetic flux density of 5 to 15mT, such as PB permalloy, PC permalloy, and permendur.

[Example 2]
The influence of hysteresis was measured using a long magnetic body 12 obtained by annealing a PC permalloy (manufactured by Oji Alloy Co., Ltd., model number: 78Ni) having a wire shape of 0.6 mm in diameter and 150 mm in length under conditions of a treatment temperature of 850 degrees and a treatment time of 6 minutes or more in a nitrogen atmosphere. The composition of the PC permalloy of Example 2 is 77.0 mass% Ni, 4.2 mass% Mo, 5.0 mass% Cu, and 13.5 mass% Fe. The magnet 15 used was made of samarium cobalt with a residual magnetic flux density of 1.06 T, had a ring shape with an outer diameter of 12 mm, an inner diameter of 7 mm, and a thickness of 3 mm, and was magnetized in the thickness direction.

The measurement was performed by placing the long magnetic body 12 inside a plastic pipe and fixing it there, and fixing the end of the plastic pipe to the probe of a gauss meter (manufactured by Lake Shore, model number: 425) which serves as the magnetic detection component 18, while passing the plastic pipe through the ring-shaped magnet 15 described above. The magnet 15 was then moved along the long pipe 29 in both directions, toward and away from the gauss meter, to measure the magnetic flux generated at the probe.

[Reference Example 1]
The wire was made of 52% iron-nickel alloy used as a reed switch material (52 alloy wire for reed switches (Fe-Ni: 52%), manufactured by Nippon Bell Parts Co., Ltd.) and had the same wire shape as in Example 1. In the same manner as in Example 1, the magnet was moved along the long pipe 29 in the direction toward and away from the gaussmeter, and the magnetic flux generated in the probe was measured. The 52% iron-nickel alloy has a saturation magnetic flux density similar to that of the PB permalloy of Example 1, a magnetic permeability at a magnetic flux density of 5 to 15 mT, and a coercive force of 20 A/m.

The results of the magnetic flux measurements in Example 2 and Reference Example 1 are shown in Figure 11. The horizontal axis of Figure 11 is the distance (mm) between the long magnetic body 12 and the magnet 15, and the vertical axis is the magnetic flux density (mT) at the end of the long magnetic body 12 measured with a gauss meter. As shown in Figure 11, in Example 2, the change in magnetic flux when the magnet 15 was moved in a direction toward the gauss meter was approximately the same as the change in magnetic flux when it was moved in a direction away from the gauss meter.

The 52% iron-nickel alloy of Reference Example 1 has a higher saturation magnetic flux density of 1.4 T than PC permalloy, and therefore generates a larger magnetic flux, but its coercive force is large at 20 A/m, which causes the effects of hysteresis and results in a significant difference between the magnetic flux when approaching and when separating. At the position of magnetic detection element 18d, the magnet distance when a magnetic flux density of 2 mT is generated is 100 mm when approaching and 112 mm when separating, resulting in an error of 12 mm when determining the distance from the numerical value of the magnetic flux density at the position of magnetic detection element 18d. If the detection range is 100 mm, the error is approximately 12%.

Another problem caused by coercive force is that when the 52% iron-nickel alloy is approached, in areas where the magnet distance is 130 mm or more, the change in magnetic flux density at the position of the magnetic detection element 18d is very small, at 0.2 mT or less, making it difficult to determine the magnet position from the change in magnetic flux density. In contrast, the PC permalloy of Example 2 obtains a change in magnetic flux density at the position of the magnetic detection element 18d that is nearly linear in areas where the magnet distance is 110 mm or more.

From the above, it can be seen that soft magnetic materials with high coercivity, such as the 52% iron-nickel alloy of Reference Example 1, are less suitable for use as the long magnetic body 12 due to the generation of hysteresis. Specific examples of soft magnetic materials with high coercivity other than Reference Example 1 include pure iron such as SUY-0 (coercivity 60 A/m or less), electromagnetic stainless steel such as K-M31 (coercivity 105 A/m or less), and permendur such as YEP-2V (coercivity 68 A/m or less).

By using a soft magnetic material such as PC permalloy, which has a small coercive force of 4 A/m or less, as used in Example 2, it is possible to suppress the detection error of the sensor caused by hysteresis. For applications in which detection error is not an issue, it is possible to configure a linear position sensor using a magnet with weak magnetic force or the magnetic sensor 18c of the low-sensitivity magnetic detection component 18 by using PB permalloy, which has a coercive force of 12 A/m or less but a high saturation magnetic flux density of 1.4 T or more.

[Example 3]
The long magnetic body 12 was the same as in Example 1 except that the wire shape was 2 mm in diameter, and was made of PC permalloy with a length of 150 mm, and was not annealed under conditions of a treatment temperature of 850 degrees and a treatment time of 6 minutes or more in a nitrogen atmosphere. The magnet used was an anisotropic ferrite magnet with a residual magnetic flux density of 410 mT, in the shape of a ring with an outer diameter of 12.5 mm, an inner diameter of 5.3 mm, and a thickness of 6 mm, magnetized in the thickness direction. The magnetic flux generated in the probe of the gaussmeter was measured in the same manner as in Example 1.

The results of Example 3 are shown in Figure 12. As is clear from Figure 12, in Example 3, which used an unannealed long magnetic body 12, there was a significant difference in the magnetic flux obtained at the middle part of the long magnetic body 12 when the magnet 15 was moved in a direction toward the gaussmeter and when it was moved in a direction away from the gaussmeter. This is because the long magnetic body 12 had an increased coercive force due to processing distortion; by annealing it to return it to its original coercive force as in Example 1, it is possible to make the magnetic flux in both directions consistent.

[Examples 4 to 6]
As the long magnetic body 12, PC permalloy wires having a length of 150 mm and a diameter of 0.6 mm (Example 4), 0.8 mm (Example 5), and 2 mm (Example 6) were used after annealing under conditions of a treatment temperature of 850 degrees and a treatment time of 6 minutes or more in a nitrogen atmosphere. The same PC permalloy as in Example 1 was used except for the wire diameter. As the magnet 15, a neodymium magnet with a residual magnetic flux density of 1.35 T, having a ring shape with an outer diameter of 12 mm, an inner diameter of 8 mm, and a thickness of 3 mm, and magnetized in the thickness direction was used. The magnetic flux generated in the probe of the gaussmeter was measured in the same manner as in Example 1. The results are shown in FIG. 13. As is clear from FIG. 13, regardless of the thickness of the annealed long magnetic body 12, the magnetic flux in both the direction in which the magnet 15 approaches and the direction in which it is separated was the same. Moreover, the thicker the magnetic body, the greater the magnetic flux density when the magnet 15 is located in the middle part.

[Example 7]
In Example 7, the level sensor 10 shown in FIG. 1 was produced using the long magnetic body 12 (PC permalloy with a wire shape of 0.6 mm in diameter and 50 mm in length) made of PC permalloy in Example 1 and a programmable Hall IC as the magnetic sensor 18c of the magnetic detection component 18. The programmable Hall IC used was model number HAL2425 manufactured by TDK-Micronas. FIG. 14 shows the magnetic flux density of the level sensor 10 of Example 7. The horizontal axis of the figure is the float position (mm), and the vertical axis is the magnetic flux density (mT). The magnetic flux density is the magnetic flux density measured from the output voltage of the linear Hall IC that does not correct the linearity in the programmable Hall IC. From FIG. 14, in the level sensor 10 of Example 7, the magnetic flux density changes according to the float position, but it is a curved line rather than a straight line. The magnetic flux density with respect to the float position was linearized by the function of the programmable Hall IC.

Figure 15 shows the output voltage of the level sensor 10 of Example 7. The horizontal axis of the figure is the float position (mm), and the vertical axis is the output voltage (V) linearly corrected by the programmable Hall IC. As shown in Figure 15, when the float position is from 0 mm to 40 mm, the output voltage changes from 0.5 V to 4.5 V, and when the float position changes by 1 cm, the output voltage changes by 1 V, showing good linearity and indicating that a liquid level displacement of 40 mm can be measured.

[Example 8]
In Example 8, the level sensor 10 shown in Fig. 1 was fabricated using the long magnetic body 12 (PC permalloy with a wire shape of 0.6 mm in diameter and 110 mm in length) of Example 1 and the same programmable Hall IC as in Example 7 for the magnetic detection component 18. The level sensor 10 was fabricated in the same manner as in Example 7 except that the length of the long magnetic body 12 was changed.

Figure 16 shows the output voltage of the level sensor 10 of Example 8. The horizontal axis of the figure is the float position (mm), and the vertical axis is the output voltage (V) linearly corrected by the programmable Hall IC. As shown in Figure 16, when the float position is from 0 mm to 100 mm, the output voltage changes from 0.5 V to 4.5 V, and when the float position changes by 2 cm, the output voltage changes by 0.8 V, showing good linearity and allowing the measurement of a liquid level displacement of 100 mm.

[Reference Example 2]
The change in magnetic flux density was calculated by magnetic simulation when the distance between the tip of one end of the long magnetic body 12 and the magnetic detection element 18d of the magnetic detection component 18 was changed in the axial direction of the long magnetic body 12. The long magnetic body 12 used had a wire shape of 2 mm in diameter and 80 mm in length, and was made of PC permalloy (manufactured by Hitachi Metals, Ltd., YEP-C, initial permeability: 200000, saturation magnetic flux density: 0.7 T). The magnet 15 used was a neodymium magnet with a residual magnetic flux density of 1200 mT, ring-shaped with an outer diameter of 11 mm, an inner diameter of 9 mm, and a thickness of 5 mm, and magnetized in the thickness direction.

The magnetic flux density at the position of the magnetic detection element 18d was calculated by simulating the magnetic flux generated according to the distance between the magnet and the end by placing the long magnetic body 12 at the center of the ring-shaped magnet 15 and using electromagnetic field analysis software (JMAG) from JSOL Corporation. The distance between the tip of the long magnetic body 12 and the magnetic detection element 18d was changed in 0.3 mm increments within a range of ±0.6 mm, with 1.4 mm as the reference, and the magnetic flux density at the position of the magnetic detection element 18d relative to the magnet distance was calculated by magnetic simulation.

The calculation results of the magnetic flux density for Reference Example 2 are shown in Figure 17. The horizontal axis of Figure 17 is the magnet distance, i.e., the distance (mm) between the end of the long magnetic body 12 and the magnet 15, and the vertical axis is the magnetic flux density (mT) at the position of the magnetic detection element 18d. As is clear from Figure 17, even with the same magnet distance, the magnetic flux increases as the distance between the magnetic detection element 18d and the tip of the long magnetic body 12 becomes closer, and decreases as the distance becomes farther.

For example, assuming that the operating temperature changes from 20° C. to 60° C., the linear expansion coefficient of the PC permalloy used for the long magnetic body 12 is 13×10 ⁻⁶ /° C., and the length is 80 mm, so the length will expand by 0.0416 mm with a temperature change from 20° C. to 60° C. If the material of the stem portion 13 is polypropylene with a linear expansion coefficient of 100×10 ⁻⁶ /° C. and the length is 80 mm, the length will expand by 0.352 mm with a temperature change from 20° C. to 60° C. In the above combination of the long magnetic body 12 and the stem portion 13, a difference in length of approximately 0.31 mm occurs between the long magnetic body 12 and the stem portion 13 with a temperature change from 20° C. to 60° C., and the position of the end of the long magnetic body 12 can vary by up to 0.31 mm in the longitudinal direction.

If polypropylene is used for the stem portion 13, and the distance between the position of the magnetic detection element 18d and the tip of the long magnetic body 12 is 1.4 mm at 20°C, it becomes 1.7 mm at 60°C. According to FIG. 17, when the magnetic flux density is 10 mT at the position of the magnetic detection element 18d, if the distance between the magnetic detection element 18d and the tip of the long magnetic body 12 is 1.4 mm, the distance of the magnet 15 is detected as 28 mm, whereas if the distance is 1.7 mm, the distance of the magnet 15 is 22 mm. Therefore, when the operating temperature changes from 20°C to 60°C, an error of 6 mm occurs when determining the distance of the magnet 15 from the numerical value of the magnetic flux density detected at the position of the magnetic detection element 18d. In this way, even a slight change in the distance between the tip of the long magnetic body 12 and the position of the magnetic detection element 18d causes the output of the magnetic detection component 18 to change, resulting in a large error in the detected distance of the magnet 15. Therefore, the present invention mechanically suppresses the change in distance.

[Reference Example 3]
The change in magnetic flux density when the distance between the tip of one end of the long magnetic body 12 and the magnetic detection element 18d is changed in a direction perpendicular to the axial direction of the long magnetic body 12 was calculated by magnetic simulation. The long magnetic body 12 used had a wire shape of 2 mm in diameter and 80 mm in length, and was made of PC permalloy (YEP-C, manufactured by Hitachi Metals, Ltd.; initial permeability: 200000; saturation magnetic flux density: 0.7 T). The magnet 15 used was a neodymium magnet with a residual magnetic flux density of 1200 mT, a ring shape with an outer diameter of 11 mm, an inner diameter of 9 mm, and a thickness of 5 mm, and magnetized in the thickness direction.

The magnetic flux density at the position of the magnetic detection element 18d was calculated by simulating the magnetic flux generated according to the distance between the magnet and the end by placing the long magnetic body 12 at the center of the ring-shaped magnet 15 and using electromagnetic field analysis software (JMAG) from JSOL Corporation. The magnetic flux density at the position of the magnetic detection element 18d relative to the magnet distance was calculated by magnetic simulation with the long magnetic body 12 shifted in the orthogonal direction within a range of 1.2 mm from the magnetic detection element 18d.

The calculation results of the magnetic flux density for Reference Example 3 are shown in Figure 18. The horizontal axis of Figure 18 is the distance (mm) between the long magnetic body 12 and the magnet 15, and the vertical axis is the magnetic flux density (mT) at the position of the magnetic detection element 18d.

As is clear from Figure 18, even with the same magnet distance, fluctuations in magnetic flux density occur when the tip of the long magnetic body 12 is misaligned in the orthogonal direction from the magnetic detection element 18d. When a magnetic flux density of 10 mT is generated at the position of the magnetic detection element 18d, if the misalignment of the long magnetic body 12 is 0 mm, the magnet distance is 28 mm, whereas if the misalignment of the long magnetic body 12 is 0.4 mm, the magnet distance is 26 mm. In this case, an error of 2 mm occurs when determining the distance from the numerical value of the magnetic flux density at the element position of the magnetic detection element 18d. As such, when the misalignment in the orthogonal direction between the tip of the long magnetic body 12 and the magnetic detection element 18d becomes large, an error occurs in the sensor output, so it is desirable to be able to suppress the misalignment in the orthogonal direction mechanically.

The present invention can be implemented in various forms without departing from the spirit of the invention. For example, in the above embodiment, the output of the programmable hall IC is shown as a voltage, but this is not limited to this. The liquid level and the liquid level scale can be displayed on a separate display device equipped with a liquid crystal or organic electroluminescence (EL) or the like, or the liquid level position information can be output to an external device via wired or wireless communication. Also, in the above embodiment, the output of the magnetic detection component 18 is output using the connector 18b, but a lead wire made of an insulated conductor or a wire harness can also be used.

10...Level sensor,
11...base portion, 11a...flange portion,
12... Long magnetic body,
13... stem portion,
15…Magnet,
16... float (slider), 16a... through hole,
18, 18x, 18y...magnetic detection components, 18a...output, 18b...connector, 18c...magnetic sensor, 18d...magnetic detection element,
20...frame body,
21...rigid frame portion, 21a...frame plate, 21b...connecting portion, 21c...connecting piece, 21d...connecting pin, 21e...through hole, 21f...dividing portion, 21g...frame piece, 21h...cylindrical protrusion, 21i...clip, 21j...elastic claw, 21k...fixing member,
23...elastic portion, 23a...spring portion, 23b...receiving portion, 23c...internal support piece,
24a... leaf spring, 24b... compression spring, 24c... resin molded body, 24d... pressure portion, 24e... receiving portion,
25...Housing,
27, 27x, 27y...substrate,
29... Long pipe, 29a... Rib,
30...Housing,
31...connection harness,
32...Compression spring,
33…Receiver,
35...connection portion, 35a...elastic connection portion,
36...Connection protrusion

Claims (13)

1. A magnetic sensor including a magnetic detection element, and a magnetic detection component configured by mounting the magnetic sensor on a substrate;
   a long magnetic body arranged with an end facing the magnetic detection component;
   a magnet movable between both ends of the long magnetic body;
   a frame that supports the elongated magnetic body in a state in which the elongated magnetic body can move in a longitudinal direction relative to the magnetic detection component and that contains the magnet;
   A linear position sensor comprising:
   The frame body is provided with an elastic portion,
   The linear position sensor, in which the elastic portion biases the end of the long magnetic body and the magnetic detection element to maintain a predetermined distance therebetween.
2. The linear position sensor according to claim 1, comprising two of the magnetic detection components facing both ends of the long magnetic body, both ends of the long magnetic body facing the magnetic detection components, and biased by the elastic portion so as to maintain a predetermined distance between both ends of the long magnetic body and each of the magnetic detection elements.
3. The linear position sensor according to claim 1 or 2, wherein the frame has a receiving portion that supports the end of the long magnetic body at a predetermined position.
4. The linear position sensor according to claim 1 or 2, which has a long pipe that houses the long magnetic body, and the long pipe is fixed to the frame in a non-jointed state with the long magnetic body.
5. The linear position sensor of claim 1, wherein the long magnetic body is made of a soft magnetic material having a saturation magnetic flux density of 0.65 T or more, a coercive force of 12 A/m or less, and a magnetic permeability of 3000 or more at a magnetic flux density of 5 to 15 mT.
6. The linear position sensor of claim 1, wherein the magnetic permeability of the long magnetic body is 5000 or more at a magnetic flux density of 5 to 15 mT.
7. The linear position sensor of claim 6, wherein the long magnetic body is made of PC permalloy, the saturation magnetic flux density of the PC permalloy is 0.65 T or more, and the magnetic permeability at the magnetic flux density of 5 to 15 mT is 8000 or more.
8. The linear position sensor of claim 6, wherein the long magnetic body is made of PB permalloy, the saturation magnetic flux density of the PB permalloy is 1 T or more, and the magnetic permeability at the magnetic flux density of 5 to 15 mT is 5000 or more.
9. The linear position sensor of claim 1, wherein the long magnetic body is made of magnetically annealed permalloy.
10. The linear position sensor of claim 1, wherein the magnet is a neodymium magnet or a samarium-cobalt magnet with a residual magnetic flux density of 1 T or more.
11. The long magnetic body is accommodated inside a long pipe,
    The frame fixes and supports the end of the long pipe,
    the magnet is supported by a slider, and the slider is disposed within the frame so as to be movable along the long pipe;
    A linear position sensor in which the slider moves between both ends of the long magnetic body in accordance with the movement of a detection target, and the magnetic detection component detects the magnetic flux of the magnet induced by the long magnetic body,
    3. The linear position sensor according to claim 1, wherein the elastic portion is urged to maintain a predetermined distance between the end of the long magnetic body and the magnetic detection element.
12. A magnetic detection element is incorporated in the magnetic detection component,
    12. The linear position sensor according to claim 11, wherein a magnetic flux density generated by said magnet at the position of said magnetic detection element is 1 mT or more when said slider is disposed at a position farthest from said magnetic detection element of said magnetic detection component.
13. 12. The linear position sensor of claim 11, which is a level sensor for detecting a liquid level.
    
    

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