Linear displacement detection system, valve positioner, and valve opening meter

Abstract

To utilize a detectable area of a magnetic sensor in the entire area.SOLUTION: A linear displacement detection system comprises a displacement unit 101, a magnetic sensor 102, and an operation unit 103. The displacement unit 101 includes magnetized parts 111, 112 that are arranged at a plurality of portions and provided at an interval in a direction of displacement 151. The adjacent magnetized parts 111, 112 have different magnetic poles on a side of the magnetic sensor 102. The interval between the adjacent magnetized parts 111, 112 is within a range in which the magnetic sensor 102 can detect the intensity of a magnetic field generated at a middle position between the adjacent magnetized parts 111, 112, with the magnetic sensor 102 being arranged at the middle position between the adjacent magnetized parts 111, 112.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a linear displacement detection system, a valve positioner, and a valve opening meter. [Background technology]

[0002] A known position detection device is a magnetic type position detection device that detects the position of a magnet by detecting the magnetic field of the magnet. For example, there is a technology that uses a magnetic sensor to detect the angular change of the magnetic field vector emitted from a magnet moving in a linear direction, and then converts the linear movement of the magnet into an angle to identify the linear position (Patent Document 1, Patent Document 2).

[0003] To accurately detect angles, a sufficient magnetic field must be applied to the magnetic sensor, and the range of displacement that can be sensed is limited by the distance between the magnet and the sensor. Simply increasing the size of the magnet may not be enough to detect a sufficient amount of angular change in the magnetic field vector. The technology in Patent Document 1 uses multiple magnetic sensors to expand the detection range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 10,571,305 [Patent Document 2] US Patent Application Publication No. 2020 / 0191546 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional technology, when it is desired to achieve both the strength of the magnetic field and the amount of vector angle change per displacement, there is a problem in that the entire detectable range of the magnetic sensor cannot be utilized.

[0006] The present invention has been made to solve the above problems, and has an object to make it possible to utilize the entire detectable area of ​​a magnetic sensor. [Means for solving the problem]

[0007] The linear displacement detection system of the present invention comprises a displacement unit having magnetization units arranged at intervals at multiple locations in the direction of displacement, a magnetic sensor fixed to a location where the magnetic field generated by the magnetization unit can be detected, and a calculation unit configured to calculate the relative position between the displacement unit and the magnetic sensor based on the angular change in the magnetic field vector caused by the displacement of the displacement unit detected by the magnetic sensor, wherein adjacent magnetization units have different magnetic poles on the side of the magnetic sensor, and the interval between adjacent magnetization units is set within a range where the magnetic sensor can detect the strength of the magnetic field generated at the midpoint between adjacent magnetization units when the magnetic sensor is positioned at the midpoint between adjacent magnetization units.

[0008] In one configuration example of the linear displacement detection system, the magnetizing portion is a permanent magnet, and the displacement portion includes permanent magnets individually arranged at intervals at a plurality of locations in the direction of displacement.

[0009] In one example of the linear displacement detection system, the permanent magnet is a rectangular parallelepiped.

[0010] The valve positioner according to the present invention detects and controls the opening of the valve as a displacement of the valve using the linear displacement detection system.

[0011] The valve opening meter according to the present invention detects and displays the valve opening as a valve displacement using the linear displacement detection system. [Effects of the Invention]

[0012] As described above, according to the present invention, the spacing between adjacent magnetized sections is set to a range in which the magnetic sensor can detect the strength of the magnetic field created at the midpoint between adjacent magnetized sections when the magnetic sensor is placed at the midpoint between the adjacent magnetized sections, so that the entire detectable area of ​​the magnetic sensor can be utilized. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the configuration of a linear displacement detection system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a characteristic diagram showing changes in the magnetic field intensity and magnetic field vector detected by the magnetic sensor in response to changes in the relative positions of the magnetized portion and the magnetic sensor. [Figure 3] FIG. 3 is a characteristic diagram showing changes in the magnetic field intensity and magnetic field vector detected by the magnetic sensor with respect to differences in the relative positions of the magnetized portion and the magnetic sensor. [Figure 4] FIG. 4 is a characteristic diagram showing changes in the magnetic field intensity and magnetic field vector detected by the magnetic sensor with respect to differences in the relative positions of the magnetized portion and the magnetic sensor. [Figure 5] FIG. 5 is a characteristic diagram showing changes in the magnetic field intensity and magnetic field vector detected by the magnetic sensor with respect to differences in the relative positions of the magnetized portion and the magnetic sensor. [Figure 6] FIG. 6 is a characteristic diagram showing changes in the magnetic field intensity and magnetic field vector detected by the magnetic sensor with respect to differences in the relative positions of the magnetized portion and the magnetic sensor. DETAILED DESCRIPTION OF THE INVENTION

[0014] A linear displacement detection system according to an embodiment of the present invention will be described below with reference to FIG. 1. This linear displacement detection system includes a displacement unit 101, a magnetic sensor 102, and a calculation unit 103. This linear displacement detection system is applicable to, for example, a valve positioner. The valve positioner detects and controls the opening of a valve as a valve displacement using the linear displacement detection system according to the embodiment. The linear displacement detection system is also applicable to, for example, a valve position indicator. The valve position indicator detects and displays the opening of a valve as a valve displacement using the linear displacement detection system according to the embodiment.

[0015] The displacement unit 101 includes magnetized units 111 and 112 arranged at intervals at multiple locations in the displacement direction 151. Adjacent magnetized units 111 and 112 have different magnetic poles on the side of the magnetic sensor 102. The magnetized units 111 and 112 may be permanent magnets. The magnetized units 111 and 112 are magnets and are individually arranged at intervals at multiple locations in the displacement direction 151. The permanent magnets constituting the magnetized units 111 and 112 may have a rectangular parallelepiped outer shape.

[0016] The magnetic sensor 102 is fixed to a location where it can sense (detect) the magnetic field generated by the magnetized portions 111 and 112. The magnetic sensor 102 is a sensor that detects a magnetic field using the magnetoresistance effect, and its electrical resistance changes with changes in the magnetic field. The magnetic sensor 102 can be configured, for example, from an anisotropic magnetoresistance effect (AMR) element, a giant magnetoresistance effect (GMR) element, or a tunnel magnetoresistance effect (TMR) element.

[0017] The calculation unit 103 calculates the relative position between the displacement unit 101 and the magnetic sensor 102 based on the change in angle of the magnetic field vector caused by the displacement of the displacement unit 101 detected by the magnetic sensor 102. The calculation unit 103 outputs the calculated position information to a higher-level device, for example, via a network.

[0018] Here, the distance between adjacent magnetized portions 111, 112 is set to a range in which the magnetic sensor 102 can detect the strength of the magnetic field generated at the midpoint between the adjacent magnetized portions 111, 112 when the magnetic sensor 102 is positioned at the midpoint between the adjacent magnetized portions 111, 112.

[0019] When the magnetized portion (magnet) in the displacement portion moves (displaces) linearly and passes the magnetic sensor, the magnetic field vector from the magnetized portion changes at the magnetic sensor. This change in magnetic field vector can be detected by the magnetic sensor. For accurate detection of the magnetic field vector by this magnetic sensor, it is important that a sufficient magnetic field is applied to the magnetic sensor. For example, if the magnetic sensor is an AMR sensor (kmt37) manufactured by TE Connectivity, a magnetic field of 25 kA / m (saturation magnetic field) or more is required to maintain sufficient accuracy. In addition, the range of displacement that can be detected is limited by the distance between the magnet and the sensor. For example, even if a larger magnet is used to generate a larger magnetic field, the angular change in the magnetic field vector may not be sufficient.

[0020] As mentioned above, when detecting linear displacement, the strength of the magnetic field reaching in the linear direction and the amount of vector angle change per displacement are important, but when detecting linear displacement using conventional magnets, considering both the strength of the magnetic field and the amount of vector angle change per displacement, it is not possible to use the entire detectable range of the magnetic sensor.

[0021] For example, in the case of one magnetized portion (magnet), the magnetic field vector detected by the magnetic sensor in response to the change in the relative position between the magnetized portion and the magnetic sensor changes as shown by the straight line in Figure 2. Furthermore, if the length of the magnetized portion in the displacement direction is increased, for example, if two magnets are simply lined up, the magnetic field vector detected by the magnetic sensor in response to the change in the relative position between the magnetized portion and the magnetic sensor changes as shown by the straight line in Figure 3. Note that in Figures 2 and 3, the change in magnetic field strength in response to the change in the relative position between the magnetized portion and the magnetic sensor is indicated by the dashed line. The same applies to Figures 4, 5, and 6, which will be described later.

[0022] In contrast to these simulation results, when a magnetic sensor with a detection angle range of 180° is used, only about half of the detectable area of ​​the magnetic sensor is utilized for one magnetized part. Also, as is clear from a comparison of Figure 2 with Figure 3, simply increasing the size of the magnet reduces the amount of change in the magnetic field vector detected by the magnetic sensor in response to changes in relative position.

[0023] On the other hand, when two magnetized sections with different magnetic poles on the magnetic sensor side are placed at an appropriate interval, the magnetic field vector detected by the magnetic sensor in response to the difference in relative position between the two magnetized sections and the magnetic sensor changes as shown by the straight line in Figure 4. As is clear from Figure 4, by placing the two magnetized sections at an appropriate interval, the amount of change in the magnetic field vector detected by the magnetic sensor in response to the difference in relative position increases.

[0024] In this way, by arranging two magnetized parts with different magnetic poles on the magnetic sensor side at an appropriate interval, it becomes possible to utilize almost the entire detectable area of ​​the magnetic sensor. Also, as is clear from Figure 4, by arranging two magnetized parts with different magnetic poles on the magnetic sensor side at an appropriate interval, the amount of change in the magnetic field vector per unit displacement is increased. It is clear that by increasing the amount of change in the magnetic field vector per unit displacement, differences in relative position can be detected more accurately.

[0025] However, if the distance between the two magnetized parts with different magnetic poles on the magnetic sensor side is narrowed as shown in Fig. 5, the sensing distance becomes shorter, as is clear from a comparison of Fig. 4 and Fig. 5. Therefore, it is preferable to make the distance between the two magnetized parts as long as possible.

[0026] On the other hand, as shown in Figure 6, if the distance between the two magnetized parts with different magnetic poles on the magnetic sensor side is too wide, the magnetic field between the two magnetized parts will be weak. This will make it impossible to detect position continuously with precision. In addition, the detected angle change will be small between the two magnetized parts, which will also make it difficult to maintain precision.

[0027] As described above, according to an embodiment of the present invention, the magnetization sections are arranged at multiple locations in the direction of displacement and spaced apart, and the spacing between adjacent magnetization sections is set within a range in which the magnetic sensor can detect the strength of the magnetic field created at the midpoint between the adjacent magnetization sections when the magnetic sensor is positioned at the midpoint between the adjacent magnetization sections, thereby making it possible to utilize the entire detectable area of ​​the magnetic sensor.

[0028] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0029] 101...displacement portion, 102...magnetic sensor, 103...calculation portion, 111...magnetization portion, 112...magnetization portion, 151...displacement direction.

Claims

1. a displacement unit including magnetized portions arranged at intervals in a plurality of positions in a displacement direction; a magnetic sensor fixed to a location capable of detecting a magnetic field generated by the magnetization unit; a calculation unit configured to calculate a relative position between the displacement unit and the magnetic sensor based on an angle change of a magnetic field vector caused by the displacement of the displacement unit detected by the magnetic sensor; Equipped with The adjacent magnetized portions have different magnetic poles on the magnetic sensor side, The interval between the adjacent magnetized portions is set within a range in which the magnetic sensor can detect the strength of the magnetic field generated at the intermediate position between the adjacent magnetized portions when the magnetic sensor is disposed at the intermediate position between the adjacent magnetized portions. Linear displacement detection system.

2. 2. The linear displacement detection system according to claim 1, A linear displacement detection system in which the magnetization unit is a permanent magnet, and the displacement unit includes the permanent magnets arranged at multiple locations in the direction of displacement and individually spaced apart.

3. 3. The linear displacement detection system according to claim 2, A linear displacement detection system, wherein the permanent magnet is a rectangular parallelepiped.

4. A valve positioner that detects and controls the opening of a valve as a valve displacement using the linear displacement detection system according to any one of claims 1 to 3.

5. A valve opening meter that detects and displays the opening of a valve as a valve displacement using the linear displacement detection system according to any one of claims 1 to 3.

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