1. Technical Field
The disclosure relates to a position detecting device using a magnet structure and a magnetic detection device, and especially relates to a highly accurate and improved position detecting device for enlarging a linearity range of an output of magnetic detection means while increasing magnetic flux density of a composite magnetic field in a position detecting area.
2. Description of the Related Art
Patent Literature 1 discloses a position detecting device that enlarges a range in which magnetic flux density varies linearly. The position detecting device includes a permanent magnet unit having a permanent magnet with two magnetized poles. A magnet structure is configured in such a manner that auxiliary magnetic materials or auxiliary magnets are disposed apart from the permanent magnet and their centers each are positioned to deviate outwardly from a peak position of a magnetic field emitted from the respective magnetic poles of the permanent magnet. The position detecting device further includes magnetic detection means that moves, relative to the permanent magnet, in a space between the permanent magnet and auxiliary magnetic materials or auxiliary magnets, and detects a magnetic field of the permanent magnet. Thus, the peak positions of the magnetic field are shifted to separate from each other, thereby enlarging a linearity area of a composite magnetic field generated in between two poles.
PTL1: Unexamined Japanese Patent Publication No. 2007-225575
The present disclosure proposes a position detecting device that increases magnetic field intensity while having a simple magnet structure and enlarges a linearity area of a composite magnetic field generated in between two poles.
The position detecting device in the present disclosure includes a permanent magnet unit having magnetic pole areas of N-pole and S-pole in a surface thereof, and a magnetic detection device apart from the surface of the permanent magnet unit by a distance. The permanent magnet unit has a main magnet element, and an auxiliary magnet element that is located closer to the magnetic detection device than the main magnet element is. The auxiliary magnet element has an N-pole auxiliary magnet part with the N-pole in the side of the surface and an S-pole auxiliary magnet part with the S-pole in the side of the surface. The main magnet element has an N-pole main magnet part on a side of the N-pole auxiliary magnet part and an S-pole main magnet part on a side of the S-pole auxiliary magnet part. The magnetic detection device is relatively movable in a direction tilted with respect to an area boundary plane that separates magnetic poles of a magnetic field generated by the permanent magnet unit, while keeping the distance from the permanent magnet unit. The N-pole auxiliary magnet part and the S-pole auxiliary magnet part are disposed apart from each other by a gap, and the gap is larger than a gap between the N-pole main magnet part and the S-pole main magnet part.
The position detecting device in the present disclosure can enlarge a linearity area of a composite magnetic field while increasing magnetic field intensity with a simple structure.
Hereinafter, exemplary embodiments will be described in detail with reference to the drawings as necessary. Note that, unnecessary detail description may be omitted. For instance, detail description of well-known matters or overlapped description of the substantially same configuration may be omitted. This is because that the following description is avoided from being redundant unnecessarily and understood easily by those skilled in the art.
Note that, the accompanying drawings and the following description is proposed in order for those skilled in the art to fully understand the present disclosure, but not intended to limit subject matter recited in claims.
Hereinafter, using
Main magnets 111a, 111b are magnetized in a direction perpendicular to a plane area in which magnetic detection device 30 moves. Directions of magnetic flux from main magnets 111a, 111b are opposite to each other, and desirably differ from each other by 180 degree. Auxiliary magnets 121a, 121b are disposed in direct contact with upper surfaces of main magnets 111a, 111b. Directions of magnetic flux from auxiliary magnets 121a, 121b are the same as those of the magnetic flux from main magnets 111a, 111b respectively. Magnetic detection device 30 is disposed above permanent magnet unit 110 configured in such a manner. Now, the space between auxiliary magnet 121a and auxiliary magnet 121b, which is a magnetic gap, is wider than the gap between main magnet 111a and main magnet 111b. Herein, the gap between main magnet 111a and main magnet 111b and the gap between auxiliary magnet 121a and auxiliary magnet 121b are preferably determined to satisfy the following conditional expression (1):
L10<L11 (1)
where L10 is a gap distance between the main magnets, and L11 is a gap distance between the auxiliary magnets.
Note that, main magnet 111a and main magnet 111b may be in direct contact with each other, or may be separated by a magnetic gap. Further, a yoke (not shown) may additionally be attached to an opposite side of main magnets 111a, 111b with respect to magnetic detection device 30 as necessary.
More specifically, magnetic detection device 30 moves in above auxiliary magnets 121a, 121b (in a space apart from auxiliary magnets 121a, 121b in Z direction) relatively with respect to permanent magnet unit 110 in approximately X direction, and then generates an output voltage depending on the magnetic flux density in Z direction that is detected at a goal position thereof. This makes it possible to detect a relative position of magnetic detection device 30 to permanent magnet unit 110. That is, as shown in
A magnetic detection method using position detecting device 100 with the above configuration will be described below.
Note that, in permanent magnet unit 110 shown in
As above, in position detecting device 100 in accordance with the first exemplary embodiment, auxiliary magnets 121a, 121b are disposed on main magnets 111a, 111b respectively, and magnetic detection device 30 is further disposed above auxiliary magnets 121a, 121b. This configuration ensures a wide range linearity of the composite magnetic field, thereby increasing magnetic flux density. Consequently, position detecting device 100 of the present disclosure can enlarge a position detectable area. Additionally, large enough magnetic field intensity can be obtained. This makes it possible to reduce errors due to influence of surrounding magnetic materials, thereby proposing a position detecting device with small errors. Further, if a yoke is disposed below main magnets 111a, 111b, larger magnetic flux density will be obtained.
Hereinafter, position detecting device 200 in accordance with a second exemplary embodiment will be described using
In permanent magnet unit 210 of position detecting device 200, main magnet 111a and auxiliary magnet 121a, which are described in the first exemplary embodiment, are integrated. Likewise, main magnet 111b and auxiliary magnet 121b, which are described in the first exemplary embodiment, are integrated. That is, permanent magnet 210a is formed by integrating main magnet 111a and auxiliary magnet 121a of permanent magnet unit 110 described in the first exemplary embodiment. Likewise, permanent magnet 210b is formed by integrating main magnet 111b and auxiliary magnet 121b. Then, permanent magnet 210a and permanent magnet 210b constitute permanent magnet unit 110.
As shown in
L20<L21 (2)
where L20 is a gap distance between the base parts, and L21 is a gap distance between the auxiliary parts.
Herein, base part 211a and base part 211b may be in direct contact with each other, or may be separated by a magnetic gap. Further, a yoke (not shown) may additionally be attached to an opposite side of permanent magnets 210a, 210b with respect to magnetic detection device 30 as necessary.
Furthermore, the length in Y direction of auxiliary parts 221a, 221b may be shorter than that of base parts 211a, 211b.
As above, in the present exemplary embodiment, auxiliary parts 221a, 221b are disposed on base parts 211a, 211b respectively to constitute permanent magnet unit 210. Further, magnetic detection device 30 is disposed above permanent magnet unit 210. This configuration ensures a wide range linearity, thereby increasing magnetic flux density. Consequently, position detecting device 200 of the present disclosure can enlarge a position detectable area. Additionally, large enough magnetic field intensity can be obtained. This makes it possible to reduce errors due to influence of surrounding magnetic materials, thereby proposing position detecting device with small errors.
Hereinafter, a third exemplary embodiment will be described using
Main magnets 311a, 311b are magnetized in a direction orthogonal to a plane area in which magnetic detection device 30 moves. Magnetic flux directions of main magnets 311a, 311b are opposite to each other in up-and-down direction (Z direction), and desirably differ from each other by 180 degree. Magnetic flux directions of first auxiliary magnets 321a, 321b disposed in direct contact with upper surfaces of main magnets 311a, 311b are the same as the magnetic flux directions of main magnets 311a, 311b respectively. Further, magnetic flux directions of second auxiliary magnets 322a, 322b disposed in direct contact with upper surfaces of first auxiliary magnets 321a, 321b are the same as the magnetic flux directions of first auxiliary magnets 321a, 321b respectively.
Now, a magnetic gap is provided between first auxiliary magnet 321a and first auxiliary magnet 321b. Likewise, a magnetic gap is provided between second auxiliary magnet 322a and second auxiliary magnet 322b. Herein, gap distance L31 between first auxiliary magnet 321a and first auxiliary magnet 321b and gap distance L32 between second auxiliary magnet 322a and second auxiliary magnet 322b are wider than gap distance L30 between main magnet 311a and main magnet 311b. Further, gap distance L32 between second auxiliary magnet 322a and second auxiliary magnet 322b is wider than gap distance L31 between first auxiliary magnet 321a and first auxiliary magnet 321b. Furthermore, gap distance L30 between main magnet 311a and main magnet 311b, gap distance L31 between first auxiliary magnet 321a and first auxiliary magnet 321b, and gap distance L32 between second auxiliary magnet 322a and second auxiliary magnet 322b are determined to satisfy the following conditional expression (3):
L30<L31≦L32 (3)
where L30 is a gap distance between the main magnets, L31 is a gap distance between the first auxiliary magnets, and L32 is a gap distance between the second auxiliary magnets.
Note that, as shown in conditional expression (3), gap distance L31 between first auxiliary magnet 321a and first auxiliary magnet 321b may be equal to gap distance L32 between second auxiliary magnet 322a and second auxiliary magnet 322b. Further, main magnets 311a, 311b may be in direct contact with each other, or may be separated by a magnetic gap. Furthermore, a yoke (not shown) may be additionally attached to an opposite side of main magnets 311a, 311b with respect to magnetic detection device 30 as necessary. Still further, the lengths in Y direction of the first auxiliary magnets 321a, 321b and the second auxiliary magnets 322a, 322b may be shorter than that of main magnets 311a, 311b. Still furthermore, any auxiliary magnets may be further disposed on the second auxiliary magnets 322a, 322b. The number of laminated auxiliary magnets may be more than this.
In permanent magnet unit 310 in accordance with the third exemplary embodiment, first auxiliary magnets 321a, 321b and second auxiliary magnets 322a, 322b are disposed on main magnets 311a, 311b respectively. Further, magnetic detection device 30 is disposed above second auxiliary magnets 322a, 322b. This configuration ensures a wide range linearity, thereby increasing magnetic flux density. Consequently, position detecting device 300 of the present disclosure can enlarge a position detectable area. Additionally, large enough magnetic field intensity can be obtained. This makes it possible to reduce errors due to influence of surrounding magnetic materials, thereby proposing a position detecting device with small errors.
As above, the first, second, and third exemplary embodiments are described as an example of the technique disclosed in the present application. However, the technique of the present disclosure is not limited to this, but may be applied to exemplary embodiments in which modification, replacement, addition, omission, or the like are made. Further, the respective components described in the first, second, and third exemplary embodiments may be combined to configure a new exemplary embodiment. Hereinafter, other exemplary embodiments will be described as an example.
Main magnet 411 (main magnet element) is a permanent magnet that is magnetized to have multiple poles. That is, main magnet 411 has non-magnetized area 411c located between first main magnet area 411a (N-pole main magnet part) and second main magnet area 411b (S-pole main magnet part). Herein, first main magnet area 411a and second main magnet area 411b each serve as a magnetized area. Auxiliary magnets 121a, 121b are disposed on one surface of main magnet 411 to configure permanent magnet unit 410. A gap (gap distance P2) between auxiliary magnets 121a, 121b is larger than a width (length in X direction) of non-magnetized area 411c.
Note that, as described in the second exemplary embodiment, main magnet 411 and auxiliary magnets 121a, 121b may be formed integrally as a permanent magnet.
In position detecting device 500, as shown in
Further, main magnets 111a, 111b of position detecting device 500 may be formed integrally like main magnet 411 shown in the first modification example.
Furthermore, to increase the driving force, facing magnets 61a, 61b may be employed as necessary. Facing magnets 61a, 61b are disposed on an opposite side (lower side in Z direction) of drive coil 50 with respect to main magnets 111a, 111b as shown in
Hereinafter, to verify effects of the present disclosure, a verification experiment will be described.
NdFeB-based permanent magnet (10 mm×2 mm×1.5 mm) was used as a main magnet, and a main surface thereof (a surface of 10 mm×2 mm) was magnetized by a single pole. NdFeB-based permanent magnet (4 mm×1 mm×1 mm) was also used as an auxiliary magnet, and a main surface thereof (a surface of 4 mm×1 mm) was magnetized by a single pole.
Side faces of two main magnets extending in Y axial direction are directly contacted, and an iron yoke is further disposed on a back surface side of the two main magnets. At this time, the main magnets are disposed such that their magnetization directions are opposed to each other. The yoke has substantially the same size as the permanent magnet and its thickness is 1.0 mm. On an upper surface of each main magnet, an auxiliary magnet whose magnetization direction is aligned to that of the main magnet is disposed. Two auxiliary magnets each are apart from a contact face between the main magnets by distance d, and disposed plane-symmetrically. Gap distance L11 between the two auxiliary magnets is 2d.
Samples 1 to 3 of the position detecting device were fabricated. The configuration of each sample is as follows:
Sample 1: without disposing any auxiliary magnet in an upper part of the main magnet, magnetic flux density in Z direction was measured at a height of 0.5 mm from the surface of the main magnet (first comparative example).
Sample 2: without disposing any auxiliary magnet in an upper part of the main magnet, magnetic flux density in Z direction was measured at a height of 3.4 mm from the surface of the main magnet (second comparative example).
Sample 3: auxiliary magnets were disposed in an upper part of the main magnet and separated from each other by a distance d of 0.4 mm, and then magnetic flux density in Z direction was measured at a height of 0.5 mm from the surface of the main magnet (working example).
Secondly, Y-axis value C of straight line A is calculated at each measurement point (e.g., at 0.05 mm intervals in measurement position X), while value B of the magnetic flux density (Y-axis value of the wave form of magnetic flux density) is measured at the same measurement point. Subsequently, an amount of shift (100×(B−C)/α) from straight line A at each measurement point is calculated as a numerical value (%). Thus, a linearity index is obtained by evaluating the maximum absolute value among the numerical values calculated at the respective measurement points.
Table 1 shows linearity indexes and slopes a of straight line A, which are calculated in the above manner, with respect to above Samples 1 to 3.
As obvious from Table 1, the working sample has a small linearity index as compared with the first and second comparative examples (Samples 1, 2). The small linearity index means that an amount of shift from the straight line is small and good linearity is obtained. Further, if magnetic flux density has good linearity in a waveform, a position detectable area will be enlarged.
On the other hand, slope a of straight line of the working sample (Sample 3) is much larger than that of the second comparative example (Sample 2), which has a good linearity in the comparative examples. This shows that the working sample has robustness against noises, which serve as an external factor. Consequently, the position detecting device of the present disclosure is obviously effective.
The present disclosure is applicable to a position detecting device using a magnetic detection device. Specifically, the present disclosure is applicable to devices for performing position detection such as image stabilization mechanism in a digital still camera, valve deflection detecting mechanism in various kinds of devices for opening and closing a valve, and plunger control.
Number | Date | Country | Kind |
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2014-195437 | Sep 2014 | JP | national |
Number | Date | Country | |
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Parent | PCT/JP2015/004334 | Aug 2015 | US |
Child | 15255140 | US |