Position detection device

Abstract

The present invention provides a position detection device that has a long service life and can perform position detection with high precision and stability. The position detection device (1) has a magnet (40) that is configured to move along a moving path (M) extending along the X direction together with a movable body (2). The magnet (40) has different magnetic poles (41, 42) in the Z direction. The position detection device (1) has a pair of magnetic sensors (21, 22) that are equidistant from the moving path (M) in the Z direction and are arranged at equidistant distances from a reference line (S) extending along the Z direction. The magnetic sensors (21, 22) have the same sensor characteristics. The position detection device (2) has a detection unit (30) that is configured to detect that the magnet (40) is on the reference line (S) when the absolute value of the output change rate of both magnetic sensors (21, 22) is approximately maximum.

Description

Technical Field

[0001] The present invention relates to a position detection device, in particular to a position detection device for detecting the position of a moving object. Background Art

[0002] For example, in machine tools such as machining centers, it is necessary to detect the initial position of a tool in order to achieve accurate machining. Position detection devices that detect the position of a movable body moved by such a detection target, such as a tool, are known that mechanically open and close electrical contacts in response to the movement of the movable body (e.g., see Patent Document 1).

[0003] However, such conventional position detection devices have the following problems: repeated mechanical switching causes contact degradation, resulting in a short lifespan. Furthermore, there are issues with poor conductivity between contacts due to foreign matter or the formation of oxide films, and wear and dents of the contacts due to repeated contact, which can reduce detection accuracy.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-183699. Summary of the Invention

[0007] Problems to be solved by the invention

[0008] The present invention has been made in view of the above-mentioned problems in the conventional technology, and an object of the present invention is to provide a position detection device that has a long life and can perform position detection with high precision and stability.

[0009] Solutions for solving problems

[0010] According to one aspect of the present invention, there is provided a position detection device that has a long service life and is capable of performing position detection with high precision and stability. The position detection device includes a magnet configured to move together with a movable body on a moving path extending along a first direction. The magnet has different magnetic poles in a second direction perpendicular to the first direction. In addition, the position detection device includes a pair of magnetic sensors that are equidistant from the moving path in the second direction and are arranged at equidistant distances from a reference line extending along the second direction. The pair of magnetic sensors have the same sensor characteristics. The position detection device includes a detection unit configured to detect that the magnet is located on the reference line when the absolute value of the output change rate of both the pair of magnetic sensors is approximately maximum. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram showing the structure of a position detection device according to an embodiment of the present invention.

[0012] Figure 2 This is a graph showing the relationship between the position of the magnet and the output of the magnetic sensor according to the embodiment of the present invention.

[0013] Figure 3 This is a graph showing changes in the output of the magnetic sensor according to the embodiment of the present invention due to temperature.

[0014] Figure 4 This is a graph showing the relationship between the shape of the magnet and the maximum magnetic flux according to the embodiment of the present invention.

[0015] Figure 5 This is a graph showing the relationship between the thickness of the magnet and the magnetic flux density according to the embodiment of the present invention.

[0016] Figure 6 1 is a diagram showing the relationship between the track deviation of the magnetic sensor and the position of the magnet according to the embodiment of the present invention.

[0017] Figure 7 This is a graph showing the relationship between the deviation of the magnetic sensor in the track direction and the output distribution according to the embodiment of the present invention.

[0018] Figure 8 This is a graph showing the relationship between the position of the magnet and the output change rate of the magnetic sensor according to the embodiment of the present invention.

[0019] Figure 9 This is a graph showing the relationship between the distance (interval) between the magnetic sensor and the magnet and the magnetic flux density according to the embodiment of the present invention.

[0020] Figure 10 This is a graph showing the relationship between the distance in the X direction centered on the detection point and the output according to the embodiment of the present invention.

[0021] Figure 11 This is a graph showing the relationship between the distance in the X direction centered on the detection point and the actual value of the output change rate according to the embodiment of the present invention.

[0022] Figure 12 This is a diagram showing changes in internal sensor values ​​as internal data when the position detection device 1 is operating normally.

[0023] Figure 13 This is a diagram showing changes in the values ​​of the internal sensors as internal data when the position detection device 1 becomes abnormal due to a return failure.

[0024] Figure 14This is a diagram showing changes in internal sensor values ​​as internal data when the position detection device 1 becomes abnormal due to bearing deterioration. DETAILED DESCRIPTION

[0025] Below, refer to Figures 1 to 14 The embodiment of the position detection device according to the present invention is described in detail. Figures 1 to 14 In the present invention, the same or equivalent structural elements are marked with the same symbols and repeated descriptions are omitted. Figures 2 to 14 In the drawings, the proportions and sizes of various components may be exaggerated, and some components may be omitted.

[0026] [1. Basic structure]

[0027] Figure 1 Schematic diagram showing the structure of the position detection device 1 according to the first embodiment of the present invention. Figure 1 As shown, the position detection device 1 of this embodiment includes: a fixed part 10; a pair of magnetic sensors 21, 22, which are fixed to the fixed part 10; a detection part 30, which is connected to the magnetic sensors 21, 22 via a signal line 12; and a magnet 40, which is mounted on a movable body 2 that is moved by a detection object such as a tool of a machining center. The movable body 2 is movable along the X direction (first direction) as shown by the arrow, and the magnet 40 mounted on the movable body 2 is configured to move on a moving path M extending along the X direction. The position detection device 1 detects whether the movable body 2 that can move in the X direction like this (and further detects the detection object such as the tool of the machining center) is located at a predetermined position ( Figure 1 baseline S).

[0028] The magnet 40 has different magnetic poles in the Z direction (second direction). Figure 1 As shown, the magnetic pole 41 on the +Z direction side of the magnet 40 is the N pole, and the magnetic pole 42 on the -Z direction side is the S pole, or vice versa. The shape of the magnet 40 can be a rectangular parallelepiped, a cube, a cylinder, a disk, etc.

[0029] The magnetic sensors 21 and 22 detect the surrounding magnetic field and have the same sensor characteristics (electrical characteristics, magnetic characteristics, temperature characteristics). These magnetic sensors 21 and 22 are arranged on a fixed portion 10 extending in the X direction and are configured at positions that are equidistant from the moving path M of the magnet 40 in the Z direction. The magnetic sensors 21 and 22 respectively have sensor sensing surfaces 21A and 22A that are perpendicular to the Z direction. In addition, the magnetic sensors 21 and 22 are configured at equal distances from a reference line S extending in the Z direction. In other words, the reference line S is located at the midpoint of the line segment connecting the two magnetic sensors 21 and 22. In addition, as Figure 1As shown, the distance between the two magnetic sensors 21 and 22 is approximately the same as the length L of the magnet 40 in the X direction. In particular, when the magnet 40 is shaped like a rectangular parallelepiped or a cube, the distance between the two magnetic sensors 21 and 22 is approximately the same as the length of the side of the magnet 40 in the X direction. Furthermore, when the magnet 40 is shaped like a cylinder or a disk, the distance between the magnetic sensors 21 and 22 is approximately the same as the length of the diameter of the magnet 40. As such magnetic sensors 21 and 22, Hall elements, magnetic modulation sensors, magnetoresistive elements, SQUID magnetic sensors, and the like can be used.

[0030] The outputs from the magnetic sensors 21 and 22 are input to the detection unit 30 , and the detection unit 30 includes a comparison circuit that compares the outputs from these magnetic sensors 21 and 22 . Figure 2 : is a graph showing the relationship between the position of the magnet 40 and the outputs of the magnetic sensors 21 and 22. Figure 2 In FIG, the output of the magnetic sensor 21 is represented by a solid line, and the output of the magnetic sensor 22 is represented by a dotted line. Figure 2 The horizontal axis represents the distance from the reference line S to the center of the magnet 40, and the vertical axis represents the output of the magnetic sensors 21 and 22. In this example, the distance between the centers of the magnetic sensor 21 and 22 in the X direction is set to approximately 3 mm, and the width of the magnet 40 in the X direction is set to approximately 4 mm.

[0031] like Figure 2 As shown in FIG. 1 , the sensor outputs of the magnetic sensors 21 and 22 become convex corresponding to the position of the magnet 40 in the X direction. Here, since the magnetic sensors 21 and 22 have the same sensor characteristics, when the magnet 40 is located at the midpoint of the line segment connecting the magnetic sensors 21 and 22, that is, when the movement distance = 0 mm (when the magnet 40 is located on the reference line S), the sensor outputs of the two sensors are consistent. In other words, Figure 2 As shown, point P where the output characteristics of magnetic sensor 21 and magnetic sensor 22 intersect is located on reference line S. Therefore, when the output of magnetic sensor 21 matches the output of magnetic sensor 22, it can be determined that magnet 40 is located on reference line S. Detection unit 30 utilizes this principle to compare the output from magnetic sensor 21 with the output from magnetic sensor 22, and when the two match, it determines that magnet 40 is located on reference line S.

[0032] By adopting this structure, it is possible to detect that the magnet 40 is located on the reference line S without using mechanical contacts. That is, according to the position detection device 1 of this embodiment, it is possible to detect the position of the movable body 2 without using mechanical contacts. Since mechanical contacts are not used in this way, problems such as shortened life due to deterioration of the contacts, poor electrical continuity between the contacts, and reduced detection accuracy due to wear or denting of the contacts do not occur.

[0033] Here, if the magnetic sensors 21 and 22 are arranged so that the rate of change of their outputs is maximized when the magnet 40 is located on the reference line S, the outputs of the magnetic sensors 21 and 22 are more likely to change when the magnet 40 is located near the reference line S. Therefore, the point at which the outputs of the magnetic sensors 21 and 22 match can be determined more accurately. Therefore, the accuracy of detecting the position of the magnet 40 is improved.

[0034] Furthermore, although the output characteristics of the magnetic sensors 21 and 22 vary depending on the temperature, since the magnetic sensors 21 and 22 have the same sensor characteristics, even if the output characteristics of the magnetic sensors 21 and 22 vary depending on the temperature, the variation in the output characteristics of the magnetic sensor 21 and the variation in the output characteristics of the magnetic sensor 22 cancel each other out. Figure 3 As shown, the point PL where the output characteristics of the magnetic sensor 21 when the temperature drops and the output characteristics of the magnetic sensor 22 when the temperature drops intersect is located on the reference line S, and the point PH where the output characteristics of the magnetic sensor 21 when the temperature rises and the output characteristics of the magnetic sensor 22 when the temperature rises intersect is also located on the reference line S. Therefore, as described above, by determining whether the output of the magnetic sensor 21 is consistent with the output of the magnetic sensor 22, it is possible to stably detect that the magnet 40 is on the reference line S even when the temperature changes. In addition, Figure 3 The thin dotted line shows Figure 2 The output characteristics of the magnetic sensors 21 and 22 are shown.

[0035] Similarly, even if the electrical or magnetic characteristics of magnetic sensors 21 and 22 change, the changes in the output characteristics of magnetic sensor 21 and magnetic sensor 22 cancel each other out, allowing for stable detection of the position of magnet 40. Furthermore, external magnetic fields in the Z direction and the Y direction (perpendicular to the paper) act similarly on both magnetic sensors 21 and 22. Since the changes in the output characteristics of magnetic sensor 21 and magnetic sensor 22 cancel each other out, the position of magnet 40 can be detected while suppressing the influence of these external magnetic fields. Furthermore, since the changes in the output characteristics of magnetic sensors 21 and 22 corresponding to the displacement of magnet 40 in the Z and Y directions cancel each other out, the position of magnet 40 can be detected while suppressing the influence of the displacement of magnet 40 in the Z and Y directions.

[0036] Alternatively, the outputs of the magnetic sensors 21 and 22 may be A / D converted and passed through a digital filter to reduce noise. Alternatively, the analog outputs of the magnetic sensors 21 and 22 may be passed through a low-pass filter to remove noise.

[0037] [2. Specific examples of structures]

[0038] [2.1. Size of magnet]

[0039] To be incorporated into precision equipment, the magnet 40 and sensor substrate must be as small as possible. Therefore, the magnet 40 is preferably less than 5 square millimeters, or φ5 mm or less. On the other hand, considering the ease of assembly of the position detection device 1, the magnet 40 is preferably of an appropriate size, and therefore is preferably at least 1.5 square millimeters.

[0040] [2.2. Shape of the magnet]

[0041] The stronger the magnetic field of the magnet 40, the better the S / N ratio and the better the repeatability. That is, it is desirable that the magnet 40 is large and thick. In addition, it is desirable that the distance between the magnetic sensors 21 and 22 and the magnet 40 is closer.

[0042] Figure 4 This is a graph showing the relationship between the magnet shape and the maximum magnetic flux when the interval between the magnetic sensor 21 and the magnetic sensor 22 and the magnet 40 is 0.8 mm and the thickness (length in the Z direction) of the magnet 40 is 1.0 mm. Figure 4 Each line in represents the length of the magnet 40 in the Y direction. That is, Figure 4 The figure shows the change in the value of the magnetic flux density when the length of the magnet 40 in the X direction is changed when the length of the magnet 40 in the Y direction is 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm, respectively. Figure 4 As can be seen from the graph, when the X-direction length of magnet 40 is less than 1.5 mm, the magnetic flux density is too low, while when it exceeds 3 mm, the magnetic flux density does not change much. In other words, the X-direction length of magnet 40 is preferably set between 1.5 and 3 mm. On the other hand, the Y-direction length of magnet 40 is preferably between 2 and 4 mm.

[0043] In addition, the magnetic field in the magnetization direction of the magnet 40 is roughly proportional to the thickness of the magnet 40 (length in the Z direction). However, if it is too thick, the shape of the magnet 40 becomes larger. In order to prevent the adhesion of chips, the magnetic shielding also needs to be strengthened. Therefore, it is expected that the thickness of the magnet 40 is set to an appropriate range.

[0044] Figure 5This is a graph showing the relationship between the length (thickness) of the magnet 40 in the Z direction and the magnetic flux density when the lengths of the magnet 40 in the X direction and the Y direction are set to 2mm×3mm and 3mm×4mm. Figure 5 As shown in the graph, when the thickness of the magnet 40 is less than 1 mm, the magnetic flux density is too low, while when the thickness exceeds 3 mm, the magnetic flux density value does not change much. In other words, the thickness of the magnet 40 is preferably set to 1 mm to 3 mm.

[0045] Furthermore, based on the principle of the position detection device 1 including the magnetic sensors 21 and 22 used in this embodiment, the positioning accuracy in the X direction is not dependent on the track deviation of the magnetic sensors 21 and 22. However, if there is an installation error between the magnetic sensors 21 and 22, the influence of the track deviation can cause positioning error. In this case, if a small, round or square magnet is used as the magnet 40, the magnetic field attenuation increases from the track, that is, from the X-axis toward the outside of the Y direction, the S / N ratio is likely to decrease, and the origin position is likely to deviate. Therefore, it is desirable that the magnet 40 be a rectangle with its length in the Y direction.

[0046] Figure 6 : is a diagram showing the relationship between the track deviation of the magnetic sensor 21 and the magnetic sensor 22 and the position of the magnet 40 when the magnet 40 is rectangular. Figure 6 As shown, the magnetic field of the magnet 40 is in an elliptical shape with the Y direction as the longitudinal direction, so the influence of the orbit deviation is reduced.

[0047] Figure 7 This graph shows the relationship between the deviation in the track direction of magnetic sensors 21 and 22 and the output distribution when the distance between magnetic sensors 21 and 22 and magnet 40 is 0.8 mm, and the lengths of magnet 40 in the X, Y, and Z directions are 3 mm × 4 mm × 1 mm. Magnet 40 is a rectangular shape with its length in the Y direction. In this case, even with a deviation in the track direction of 0.3 mm, the output attenuation rate is within 2%. This shows that magnet 40 is preferably rectangular with its length in the Y direction.

[0048] [2.3, Magnet material]

[0049] The magnet 40 is preferably made of a material that is strong, rust-resistant, and has a good temperature coefficient. More specifically, a samarium cobalt magnet with a temperature coefficient of -0.03% / °C or a rust-proof neodymium magnet with a temperature coefficient of -0.13% / °C is preferred.

[0050] [2.4. Magnetic sensor spacing]

[0051] When the pair of magnetic sensors 21 and 22 are surface mounted, it is preferable that the magnetic sensors 21 and 22 are spaced apart by approximately 1.5 mm or more.

[0052] [2.5. Relationship between magnets and magnetic sensors]

[0053] The length of the magnet 40 in the X direction that can obtain the maximum rate of change of the output of a pair of magnetic sensors 21 and the magnetic sensor 22 is approximately equal to the installation distance between the magnetic sensors 21 and the magnetic sensor 22. Therefore, when the magnetic sensor 21 and the magnetic sensor 22 are separated by approximately 1.5 mm or more as described above, it is preferred that the length of the magnet 40 in the X direction is also set to a length of approximately 1.5 mm or more.

[0054] Figure 8 This is a graph showing the relationship between the position of the magnet 40 and the output change rate of the magnetic sensor 21 and the magnetic sensor 22 when the distance between the pair of magnetic sensors 21 and 22 and the magnet 40 is 0.8 mm, the length of the magnet in the X, Y, and Z directions is 3 mm × 4 mm × 1 mm, and the length of the magnet 40 in the X direction is approximately equal to the installation distance between the magnetic sensor 21 and the magnetic sensor 22. Figure 8 As shown, when the position of the magnet 40 is 0, that is, when the magnet 40 is located on the reference line, the absolute values ​​of the output change rates of the magnetic sensor 21 and the magnetic sensor 22 are both substantially maximum.

[0055] The distance (spacing) between the pair of magnetic sensors 21 and 22 and the magnet 40 is determined by factors such as repeatability, component accuracy, assembly accuracy, and ease of assembly verification. Specifically, this is determined based on the following requirements: component accuracy of ±0.1 mm, mounting accuracy of 0.2 mm, and mechanical fluctuations (i.e., variations due to shaft looseness) of 0.1 mm or less. Consequently, the distance (spacing) between the pair of magnetic sensors 21 and the magnet 40 is preferably set to a value between 0.3 mm and 0.8 mm or less.

[0056] Figure 9 The graph shows the relationship between the distance (interval) between the pair of magnetic sensors 21 and 22 and the magnet 40 and the magnetic flux density. When the distance (interval) is 0.3 mm to 0.8 mm, the magnetic flux density is usually 120 mT to 170 mT.

[0057] Figure 10 The graph shows the relationship between the distance in the X direction around the detection point and the output when the distance (interval) between the pair of magnetic sensors 21 and 22 and the magnet 40 is 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm. Figure 10In the graph of , "Ch1" represents the output of the magnetic sensor 21, and "Ch2" represents the output of the magnetic sensor 22. Figure 10 It can be seen that the graph showing that the distance (interval) between the pair of magnetic sensors 21 and 22 and the magnet 40 is 1.0 mm has a smaller output than the other graphs.

[0058] Figure 11 This is a graph showing the relationship between the distance in the X direction centered on the detection point and the measured value of the output change rate when the distance (interval) between the pair of magnetic sensors 21 and 22 and the magnet 40 is 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm. Figure 11 In the graph of , "Ch1" represents the output change rate of the magnetic sensor 21, and "Ch2" represents the output change rate of the magnetic sensor 22. Figure 10 It can be seen that the absolute value of the output change rate is smaller in the graph showing that the distance (interval) between the pair of magnetic sensors 21 and 22 and the magnet 40 is 1.0 mm than in the other graphs.

[0059] [3. Examples of use of internal data]

[0060] By monitoring the magnetic data (sensor data) as the internal data of the position detection device 1, the status of the pair of magnetic sensors 21 and 22 can be determined, thereby enabling fault diagnosis of the position detection device 1. More specifically, by monitoring the internal data, it is possible to diagnose the maintenance period of the position detection device 1, diagnose faults of the pair of magnetic sensors 21 and 22, and diagnose the operating environment of the position detection device 1.

[0061] To diagnose maintenance requirements, it is effective to use internal data to identify poor return due to the adhesion or accumulation of chips or cutting fluid on the sliding portion of the position detection device 1, or to identify the number of operations. To diagnose failures of the pair of magnetic sensors 21 and 22, it is effective to identify poor return due to the adhesion of chips or cutting fluid, internal negative pressure, bearing deterioration, or brake damage due to collisions. To diagnose the operating environment, it is effective to identify poor return due to negative pressure inside the position detection device 1, for example, by observing changes in the ambient temperature, or to identify bearing deterioration due to machining vibrations, collisions caused by pallet changes, collisions caused by loading and unloading workpieces, clamping / unclamping, and collisions caused by storage and removal.

[0062] Below, by reference Figures 12 to 14 This section describes a method for detecting return failure and bearing degradation using internal data.

[0063] Figure 12The internal output of a conventional contact point is shown, that is, the internal output in a state where the contact 11 is pushed in and then returns.

[0064] exist Figure 12 In the figure, as shown in (a), the contact 11 is at its normal standby height during standby. Next, as shown in (b), the contact 11 is pressed in. After that, when the load on the contact 11 is removed, as shown in (c), the contact 11 returns to its original position. At this time, since the standby height of the contact 11 at (a) is equal to the standby height of the contact 11 at (c), the amount of contact 11 pressed in from (a) to (b) is equal to the amount of contact 11 returned from (b) to (c). In addition, regarding the value of the internal sensor, the value before the contact 11 is pressed in is also equal to the value after the contact 11 is pressed in and returned.

[0065] Figure 13 The figure shows changes in the values ​​of the internal sensors as internal data when the position detection device 1 becomes abnormal due to a return failure.

[0066] exist Figure 13 In the example shown, as shown in (c), cutting fluid and chips adhere to the area where contact 11 of position detection device 1 slides. Therefore, contact 11 does not return to its normal position when moving from (b) to (c). Therefore, the amount contact 11 returns from (b) to (c) is smaller than the amount contact 11 was pushed in from (a) to (b). Furthermore, the value of the internal sensor after contact 11 is pushed in and then returned is also smaller than the value before contact 11 was pushed in.

[0067] Figure 14 This figure shows the internal sensor values, which serve as internal data, when position detection device 1 is abnormal due to bearing deterioration. As shown in (a), during normal standby mode, the internal sensor values ​​do not change. On the other hand, if bearing deterioration occurs, contactor 11 vibrates due to machining vibrations, vibrations during workpiece loading and unloading, vibrations during sensor storage and removal, or collisions caused by pallet replacement. This causes the internal sensor values ​​to change, as shown in (b).

[0068] Therefore, the position detection device 1 can also have a comparison unit (not shown) and a first diagnostic unit (not shown), wherein the comparison unit compares the outputs of the magnetic sensor 21 and the magnetic sensor 22 when the position detection device 1 is on standby with the outputs of the magnetic sensor 21 and the magnetic sensor 22 when the magnet 40 is moved in the X direction and then returned in the opposite direction of the X direction, and the first diagnostic unit diagnoses abnormalities in the position detection device 1 based on the comparison result of the comparison unit.

[0069] Furthermore, the position detection device 1 may further include a second diagnostic unit (not shown) that diagnoses abnormality in the position detection device 1 based on waveforms of outputs from the magnetic sensors 21 and 22 when the position detection device 1 is in standby mode.

[0070] [4. Effects of the Implementation Method]

[0071] As described above, according to one embodiment of the present invention, there can be provided a position detection device having a long service life and capable of performing position detection with high precision and stability. The position detection device includes a magnet configured to move together with a movable body on a moving path extending along a first direction. The magnet has different magnetic poles in a second direction perpendicular to the first direction. In addition, the position detection device includes a pair of magnetic sensors that are equidistant from the moving path in the second direction and are arranged at equidistant distances from a reference line extending along the second direction. The pair of magnetic sensors have the same sensor characteristics. The position detection device includes a detection unit configured to detect that the magnet is on the reference line when the absolute value of the output change rate of both the pair of magnetic sensors is approximately maximum.

[0072] Thus, it is possible to detect that the magnet is located on the reference line without using mechanical contacts. That is, according to the position detection device of the present invention, it is possible to detect the position of a movable body without using mechanical contacts. As such, according to the position detection device of the present invention, since mechanical contacts are not used, problems such as shortened life due to deterioration of the contacts, poor conduction between the contacts, and decreased detection accuracy due to wear and depression of the contacts do not occur. In addition, since changes in the output characteristics of the magnetic sensors caused by temperature changes, etc., cancel each other out between a pair of magnetic sensors, the position of the magnet can be stably detected.

[0073] Preferably, the outputs of the pair of magnetic sensors exhibit a maximum rate of change when the magnet is located on the baseline. In this manner, since the outputs of the magnetic sensors tend to change when the magnet is near the baseline, the point at which the outputs of the magnetic sensors coincide can be more accurately determined, thereby improving the accuracy of detecting the position of the magnet.

[0074] According to the present invention, it is possible to provide a position detection device that has a long life and can perform position detection with high accuracy and stability.

[0075] Furthermore, according to the present invention, it is possible to provide a position detection device capable of performing fault diagnosis and maintenance prediction.

[0076] Industrial Application Possibilities

[0077] The present invention is suitable for use in a position detection device for detecting the position of a moving object.

[0078] Description of Reference Numerals

[0079] 1: Position detection device

[0080] 2: Active body

[0081] 10: Fixed part

[0082] 21, 22: Magnetic sensor

[0083] 30: Detection Department

[0084] 40: Magnet

[0085] 41, 42: Magnetic poles

[0086] M: Moving path

[0087] S: Baseline

Claims

1. A position detection device comprising: a magnet configured to move along a movement path extending along a first direction together with the movable body, the magnet having different magnetic poles in a second direction perpendicular to the first direction; a pair of magnetic sensors having the same sensor characteristics, the pair of magnetic sensors being equidistant from the movement path in the second direction and being arranged at equidistant distances from a reference line extending along the second direction; as well as The detection unit is configured to make the distance between the pair of magnetic sensors equal to the length of the magnet in the first direction, and detect that the magnet is located on the reference line when the absolute values ​​of the output change rates of both the pair of magnetic sensors are maximized.

2. The position detection device according to claim 1, wherein: The length of the magnet in the first direction is greater than or equal to 1.5 mm.

3. The position detection device according to claim 1 or 2, wherein: The size of the magnet is within 5 square millimeters.

4. The position detection device according to claim 1 or 2, wherein: The size of the magnet is greater than 1.5 square millimeters.

5. The position detection device according to claim 1 or 2, wherein: The length of the magnet in the first direction is 1.5 mm to 3 mm, and the length of the magnet in the second direction is 2 mm to 4 mm.

6. The position detection device according to claim 1 or 2, wherein: A length of the magnet in a third direction perpendicular to the first direction and the second direction is greater than or equal to 1 mm and less than or equal to 3 mm.

7. The position detection device according to claim 1 or 2, wherein: The magnet is in the shape of a rectangle, and the symmetry axis of the rectangle is consistent with the first direction and the second direction.

8. The position detection device according to claim 1 or 2, wherein: The pair of magnetic sensors are spaced apart by 1.5 mm or more in the first direction.

9. The position detection device according to claim 1 or 2, wherein: A distance between a central axis of the movement path of the magnet and the pair of magnetic sensors is greater than or equal to 0.3 mm and less than or equal to 0.8 mm.

10. The position detection device according to claim 1 or 2, wherein: The magnet is a samarium-cobalt magnet or a neodymium magnet that has been subjected to rust-proofing treatment.

11. The position detection device according to claim 1 or 2, further comprising: a comparator that compares the output of the magnetic sensor when the position detection device is on standby with the output of the magnetic sensor when the magnet is moved in the first direction and then returned in a direction opposite to the first direction; and A first diagnostic unit diagnoses abnormality in the position detection device based on the comparison result of the comparison unit.

12. The position detection device according to claim 1 or 2, further comprising: The second diagnosis unit diagnoses abnormality of the position detection device based on a change in the output value of the magnetic sensor caused by vibration when the position detection device is in standby mode.

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