Magnetic linear position detector

Abstract

Magnetic linear position detector (20, 21), comprising: a stator (1); and a motion device (2) designed to be movable along a first direction relative to the stator (1), wherein an element consisting of the elements stator (1) and motion device (2) is provided with a magnetic detector (3), wherein the other element consisting of the elements stator (1) and motion detector (2) is provided with a magnet (4, 40) which has a first surface (4a, 40a) facing the magnetic detector (3), wherein the magnet (4, 40) is magnetized in such a way that on the first surface (4a, 40a) of the magnet (4, 40) a magnetization direction changes in an arc shape around a magnetization center (5, 5a, 5b) in the first surface, and wherein the magnetic detector (3) is an element whose output changes depending on the direction of a magnetic field, and wherein the magnetization of the magnet (4, 40) is obtained by arranging a straight electrical wire (10) orthogonally to the first surface (4a, 40a) at the magnetization center (5, 5a, 5b) and passing a direct current through the electrical wire (10), characterized by that the magnetization center (5, 5a, 5b) lies within the plane of the first surface (4a), and that a hole is formed in the magnetization center (5, 5a, 5b) to guide the electrical wire (10) through the hole.

Description

Area

[0001] The present disclosure relates to a magnetic linear position detector capable of detecting a position of a moving device that moves linearly. background

[0002] Magnetic linear position detectors capable of detecting the position of a moving device moving in a straight line are known. In a magnetic linear position detector, one of the moving device and the stator is provided with a magnetic detector, and the other of the two is provided with a magnet. Patent Literature 1 discloses a position detector including a magnet with alternately arranged S-poles and N-poles and a magnetic sensor including a magnetoresistive element whose resistance value changes depending on the direction of a magnetic field received from the magnet.

[0003] Patent Literature 2 discloses a magnetic sensor for rotational, linear or curvilinear displacement using at least one permanent magnet and at least one magnetosensitive element.

[0004] Patent Literature 3 discloses a rotation sensor using a magnet with alternating magnetization pattern.

[0005] Patent Literature 4 discloses a magnetic linear position detector that can detect a relative linear position between a sensor and a magnetic body.

[0006] Patent Literature 5 discloses a magnetic linear position sensor that can measure a far field of a magnet.

[0007] Patent Literature 6 discloses a method and a sensor system for determining a relative angular position between two parts about a rotation axis using a magnetized body, wherein a magnetization plane of the magnetized body is parallel to the rotation axis.

[0008] Patent Literature 7 discloses a non-contact position sensor comprising a magnet and a magnetic flux sensor, wherein the magnet is configured so that a magnetic flux field can be generated by a wire in which an electric current flows, and wherein a magnetic flux direction of the magnetic flux field can be changed along at least one dimension of the magnet. Citation listPatent literature Patent literature 1: JP 5 343 001 B2; Patent literature 2: US 2010 / 0 231 205 A1; Patent literature 3: DE 10 2008 059 774 A1; Patent literature 4: DE 198 49 613 A1; Patent literature 5: DE 10 2012 111 653 A1; Patent literature 6: WO 2020 / 079 350 A1; Patent literature 7: US 2007 / 0 090 827 A1. OverviewTechnical Problem

[0009] However, magnetic lines of magnetic force from the N pole to the S pole may have a shape close to an elliptical arc. In the case of elliptically shaped magnetic lines, there are some areas where the change in the direction of the magnetic field is small depending on the change in the relative position between the magnet and the magnetic detector. Since the change in the resistance value of the magnetic detector also becomes small in this case, the accuracy of position detection is reduced. In particular, if the distance between the N pole and the S pole is increased to accommodate the displacement of the moving device, the shape of the magnetic force lines becomes an elliptical arc, which becomes long in the moving direction of the moving device, and areas where the change in the magnetic field is small are easily generated.

[0010] The present disclosure has been made in view of the above, and it is an object of the present disclosure to obtain a magnetic linear position detector capable of improving the accuracy of position detection while using a magnetoresistive element whose resistance value changes depending on the direction of a magnetic field. Solution to the problem

[0011] To achieve this goal, a magnetic linear position detector having the features of the independent claim of the present invention is provided. Advantageous embodiments of the present invention are defined in the subclaims, the description, and the drawings of the present invention.

[0012] Specifically, the magnetic linear position detector according to the present disclosure includes a stator and a moving device movable relative to the stator in a first direction. One of the stator and moving device elements is provided with a magnetic detector. The other of the stator and moving device elements is provided with a magnet having a first surface facing the magnetic detector. The first surface is magnetized in such a manner that a magnetization direction changes in an arc shape around a magnetization center. The magnetic detector is an element whose output changes depending on a direction of a magnetic field. The magnetization of the magnet is obtainable by arranging a straight electric wire orthogonal to the first surface at the magnetization center and passing a direct current through the electric wire. Advantageous effect of the invention

[0013] A magnetic linear position detector according to the present disclosure has an effect of being able to improve the accuracy of position detection of a moving device, using a magnetoresistive element whose resistance value changes depending on the direction of a magnetic field. Brief description of the drawings Fig. 1 is a perspective view explaining a schematic configuration of a magnetic linear position detector according to a first embodiment. Fig. 2 is a diagram showing a direction of a magnetic field received by a magnetic detector depending on the displacement of a magnet according to the first embodiment. Fig. 3 is a diagram explaining a method of magnetizing the magnet according to the first embodiment. Fig. 4 is a perspective view explaining a schematic configuration of the magnetic linear position detector according to a second embodiment. Fig. 5 is a diagram showing a direction of a magnetic field received by the magnetic detector depending on the displacement of the magnet according to the second embodiment. Description of embodiments

[0014] Hereinafter, a magnetic linear position detector according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the disclosure is not limited to the embodiments. First embodiment.

[0015] Fig. Fig. 1 is a perspective view illustrating a schematic configuration of a magnetic linear position detector according to a first embodiment. A magnetic linear position detector 20 includes a stator 1 and a moving device 2. The moving device 2 is rotatable relative to the stator 1 in the direction along a Fig. 1. The direction along the X-axis is a first direction. The stator 1 is provided with a magnetic detector 3. The movement device 2 is provided with a magnet 4.

[0016] The magnet 4 has a first surface 4a facing the magnetic detector 3. Note that a Z-axis is defined perpendicular to the first surface 4a. Furthermore, a Y-axis is defined perpendicular to the X-axis and the Z-axis. In the following description, the direction along the X-axis is referred to as a transverse direction, and the direction along the Y-axis is referred to as a longitudinal direction.

[0017] The first surface 4a is a rectangle with a long side parallel to the X-axis, and the ratio of the long side to the short side is 2:1.

[0018] The magnet 4 is a polar anisotropic or isotropic magnet. The first surface 4a of the magnet 4 is polar anisotropically magnetized around a magnetization center 5, and the magnetization direction is arcuate, as indicated by an arrow 6. In the first embodiment, there is a magnetization center 5, and the magnetization center 5 is located at the central portion of a long side of the first surface 4a.

[0019] The magnetic detector 3 is an element whose output changes depending on the direction of the magnetic field received by the magnet 4. The magnetic detector 3 is, for example, a spin-valve giant magnetoresistance (GMR) type detector, a spin-valve tunneling magnetoresistance (TMR) type detector, a rotation-detection anisotropic magnetoresistance (AMR) type detector, or the like. Such a magnetic detector is generally inexpensive, and the manufacturing cost of the magnetic linear position detector 20 can be kept low.

[0020] Fig. Fig. 2 is a diagram showing a direction of a magnetic field received by the magnetic detector depending on the displacement of the magnet according to the first embodiment. Fig. 2, the horizontal axis represents the displacement of the magnet 4, and the vertical axis represents the direction of the magnetic field received by the magnetic detector 3. Fig. 2 shows an example where the long side of the first surface 4a of the magnet 4 is 30 mm. Furthermore, in a state where the magnet 4 is positioned on a line extending parallel to the Y axis from the magnetization center 5, the displacement is set to 0.

[0021] As in Fig. As shown in Figure 2, the direction of the magnetic field received by the magnetic detector 3 changes in the entire range along the longitudinal direction of the magnet 4. Specifically, in the process where the displacement of the magnet 4 changes from -15 mm to +15 mm, the direction of the magnetic field received by the magnetic detector 3 changes by 180 degrees from -90 degrees (+Y direction) through 0 degrees (-X direction) to +90 degrees (-Y direction). Since the output of the magnetic detector 3 is different for all displacements, the displacement of the magnet 4 can be determined as long as the output is known.

[0022] When, as in the configuration disclosed in Patent Literature 1, for example, the same direction of the magnetic field appears multiple times depending on the displacement of the magnet, the same output of the magnetic detector also appears multiple times. Therefore, for example, a sensor for identifying the same output that appears multiple times or a sensor for detecting the magnet at the origin is required. Since the first embodiment eliminates the need for a sensor for the above-described determination, the manufacturing cost of the magnetic linear position detector 20 can be reduced. Furthermore, the process of returning to the origin when the magnetic linear position detector 20 is turned on is unnecessary, and the startup process of the drive device equipped with the magnetic linear position detector 20 can be further simplified, which means that the workability can be improved.

[0023] Furthermore, since the direction of the magnetic field changes in an arc shape, it is unlikely that areas will arise where the change in the direction of the magnetic field is small depending on the change in the relative position between the magnet 4 and the magnetic detector 3, unlike in the case where the change in the direction of the magnetic field is an elliptical arc. Therefore, it is possible to detect the position of the moving device more accurately, regardless of the displacement of the magnet 4.

[0024] By setting the ratio of the long side to the short side of the first surface 4a of the magnet 4 to 2:1, it is also possible to set the diameter of the arc to the length of the long side of the magnet 4 and to set the radius of the arc to the length of the short side of the magnet 4, as shown in Fig. 1. Therefore, it is possible to form the large area of ​​the first surface 4a as a magnetized area, ie, to actively magnetize the magnet 4 so that it has an arc-shaped magnetic field.

[0025] Fig. 3 is a diagram explaining a method for magnetizing the magnet according to the first embodiment. As shown in Fig. 3, a linear electric wire 10 is arranged orthogonally to the first surface 4a at the magnetization center 5, and a linear current is generated in the electric wire 10, thereby magnetizing the magnet 4 in such a way that the magnetization direction changes in an arc shape around the magnetization center 5. This utilizes the fact that an arc-shaped magnetic field is formed around the linear current. In the first embodiment, the electric wire 10 is arranged along the side surface of the magnet 4 because the magnetization center 5 is located on the long side of the first surface 4a. In the embodiments of the invention, the magnetization center 5 lies within the plane of the first surface 4a, a hole is formed in the magnetization center 5 to pass the electric wire 10 through the hole, and a direct current is generated in the electric wire 10.The hole is not shown in the figures that serve to explain the embodiments of the invention. Second embodiment.

[0026] Fig. Figure 4 is a perspective view illustrating a schematic configuration of the magnetic linear position detector according to a second embodiment. Note that components similar to those of the first embodiment are denoted by the same reference numerals, and a detailed description thereof is omitted.

[0027] A magnet 40 included in a magnetic linear position detector 21 according to the second embodiment is provided with two magnetization centers 5a and 5b. The magnetization direction in an arc around the magnetization center 5a is counterclockwise. The magnetization direction in an arc around the magnetization center 5b is clockwise.

[0028] The first surface 40a of the magnet 40 is a rectangle with a long side parallel to the X-axis, and the ratio of the long side to the short side is 4:1. The magnetization centers 5a and 5b are each located on 1 / 4 of a long side of the first surface 40a.

[0029] Fig. Fig. 5 is a diagram showing a direction of a magnetic field received by the magnetic detector depending on the displacement of the magnet according to the second embodiment. Fig. 5, the horizontal axis represents the displacement of the magnet 4 and the vertical axis represents the direction of the magnetic field obtained from the magnetic detector 3. Fig. 5 shows an example where the long side of the first surface 40a of the magnet 40 is 60 mm. Furthermore, the displacement is set to 0 in a state where the magnet 40 is positioned on a line extending parallel to the Y axis between the magnetization center 5a and the magnetization center 5b.

[0030] As in Fig. As shown in Figure 5, the direction of the magnetic field received by the magnetic detector 3 varies throughout the entire range along the longitudinal direction of the magnet 40. In the process where the displacement of the magnet 40 changes from -30 mm to +30 mm, the direction of the magnetic field received by the magnetic detector 3 changes by 360 degrees, namely from -180 degrees (+Y direction), through 90 degrees (-X direction), through 0 degrees (-Y direction), and through +90 degrees (+X direction) to 180 degrees (+Y direction). Since the output of the magnetic detector 3 is different at all displacements, the displacement of the magnet 40 can be determined as long as the output is known. Since a sensor for detecting the magnet 40 located at the origin is unnecessary, similar to the first embodiment, the manufacturing cost of the magnetic linear position detector 21 can be reduced.In addition, the operation of returning to the origin is unnecessary when the magnetic linear position detector 21 is turned on, and the reliability of the magnetic linear position detector 21 can be improved.

[0031] Furthermore, since the direction of the magnetic field changes in an arc shape, it is unlikely that areas will arise where the change in the direction of the magnetic field is small depending on the change in the relative position between the magnet 40 and the magnetic detector 3, unlike the case where the direction of the magnetic field changes in an elliptical arc. Therefore, it is possible to determine the position of the moving device more accurately regardless of the displacement of the magnet 40.

[0032] In addition, by setting the ratio of the long side to the short side of the first surface 40a of the magnet 40 to 4:1, the length of the long side of the magnet 40 can be set to twice the diameter of the arc, and the radius of the arc can be set to the length of the short side of the magnet 40, as shown in Fig. 4. As a result, it is possible to make a large area of ​​the first surface 40a a magnetized area, ie, to magnetize the magnet 40 so that it has an arc-shaped magnetic field.

[0033] As a magnetization method, an electric wire is arranged at each of the magnetization centers 5a and 5b, and a direct current flows in the electric wire, similar to the first embodiment. By making the current application direction different between the electric wire arranged at the magnetization center 5a and the wire arranged at the magnetization center 5b, the magnetization direction can be made different between the arc around the magnetization center 5a and the arc around the magnetization center 5b.

[0034] Furthermore, three or more arcuate magnetic fields can be provided adjacently, although a sensor or the like is required to identify the same outputs appearing at the magnetic detector multiple times, since the same direction of the magnetic field appears multiple times depending on the displacement of the magnet. This means that three or more magnetization centers can be provided. For example, when three arcuate magnetic fields are provided adjacently, the ratio of the long side to the short side of the first surface 40a of the magnet 40 is set to 6:1, whereby the magnet 40 can be effectively magnetized to have arcuate magnetic fields. When the number of arcuate magnetic fields is n (n is an integer), the ratio between the long side and the short side of the first surface 40a of the magnet 40 is preferably 2n:1.

[0035] The configurations described in the above embodiments are merely examples and may be combined with other conventional techniques, the above embodiments may be combined with each other, and part of the configurations may be omitted or changed without departing from the spirit of the present disclosure. List of reference symbols 1 stator; 2 exercise device; 3 magnetic detector; 4, 40 magnet; 4a, 40a first area; 5, 5a, 5b center of magnetization; 6 arrow; 10 electrical wire; 20, 21 magnetic linear position detector.

Claims

[1] Magnetic linear position detector (20, 21) comprising: a stator (1); and a movement device (2) which is designed to be movable along a first direction relative to the stator (1), wherein one of the elements stator (1) and movement device (2) is provided with a magnetic detector (3), wherein the other element of the stator (1) and motion detector (2) is provided with a magnet (4, 40) having a first surface (4a, 40a) facing the magnetic detector (3), wherein the magnet (4, 40) is magnetized in such a way that on the first surface (4a, 40a) of the magnet (4, 40) a magnetization direction changes in an arc shape around a magnetization center (5, 5a, 5b) in the first surface, and wherein the magnetic detector (3) is an element whose output changes depending on a direction of a magnetic field, and wherein the magnetization of the magnet (4, 40) is obtainable by arranging a straight electric wire (10) orthogonal to the first surface (4a, 40a) at the magnetization center (5, 5a, 5b) and passing a direct current through the electric wire (10), characterized by , that the magnetization center (5, 5a, 5b) lies within the plane of the first surface (4a), and that a hole is formed in the magnetization center (5, 5a, 5b) to guide the electric wire (10) through the hole. [2] Magnetic linear position detector (20, 21) according to claim 1, wherein the first surface (4a, 40a) is a rectangle having a long side parallel to the first direction, and where a ratio of the long side to a short side of the first surface (4a, 40a) is 2n: 1 (n is an integer). [3] Magnetic linear position detector (20, 21) according to claim 1, wherein two magnetization centers (5a, 5b) are provided on the first surface (40a) of the magnet, wherein the magnetization direction is oriented in an arc shape around one of the two magnetization centers (5a, 5b) counterclockwise, and wherein the magnetization direction is oriented in an arc shape around the other of the two magnetization centers (5a, 5b) in the clockwise direction.

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