JP6018417B2 - Position detection device - Google Patents

Description

  The present invention relates to a position detection device using a Hall sensor, and is resistant to a phenomenon in which position detection accuracy in a direction along the detection axis (detection axis direction) deteriorates due to displacement in a direction other than the detection axis direction (other axis direction). The present invention relates to a position detection device having a gap.

  In recent years, there is an increasing expectation for a position detection device that detects a moving distance used in mechatronic machines and automobiles. In particular, along with the improvement in performance of this type of industrial equipment, there is a demand for a position detection device that is small, highly accurate, and highly reliable. One type of position detection device is a magnetic encoder.

  In addition, while maintaining a highly accurate position detection function equivalent to the conventional one, it is possible to reduce the distance between the magnetic flux detection means and the magnet as compared with the conventional one. A device using a single hall sensor (for example, see Patent Document 1) is known. For example, in a position detection device including a magnet that detects a change in position corresponding to a change in magnetic flux and a plurality of magnetic flux detection means, the magnet includes a line connecting at least two of the magnetic flux detection means on the magnetic wall surface of the magnet, It has been proposed that the moving direction of the magnet be on the magnetic wall surface.

  FIG. 9 is a schematic perspective view in which the position detection device according to the prior art is applied to a camera module. A camera module 40 shown in FIG. 9 includes a lens 21, a lens frame 22 that supports the lens 21, and rectangular parallelepiped permanent magnets (hereinafter simply referred to as “cuboid permanent magnets”) fixed to the side surfaces 22 x and 22 y of the lens frame 22. 31x, 31y), Hall sensors 3x, 3y arranged near the center in the magnetization direction of these magnets 31x, 31y so as to face each other with a gap G therebetween, and these Hall sensors 3x, 3y are fixed. And a substrate 11 to be configured. In addition, illustration description of the printed wiring etc. for applying a voltage to Hall sensor 3x, 3y is abbreviate | omitted. Further, the gap G will be accurately defined later with reference to FIG. 2, and in FIG. 7, the gap G is also indicated as “sensor position (magnet-sensor distance: Gap)” mm.

  The lens frame 22 is supported by support means (not shown) so as to be swingable within a certain range along the X axis direction and the Y axis direction with respect to the substrate 11 so as to make use of the camera shake correction function. Yes. A description of the movement of the lens frame 22 in the Z-axis direction is omitted. Further, the position detection device 30 x detects the distance that the lens frame 22 has moved in the X-axis direction with respect to the substrate 11. The position detection device 30x is composed of a hall sensor 3x fixed on the substrate 11 and a magnet 31x fixed to the side surface 22x of the lens frame 22, and the relative movement distance between the hall sensor 3x and the magnet 31x. The corresponding voltage is detected.

  Similarly, the position detection device 30y detects the distance that the lens frame 22 has moved in the Y-axis direction with respect to the substrate 11. The position detection device 30Y is composed of a hall sensor 3y fixed on the substrate 11 and a magnet 31y fixed to the side surface 22y of the lens frame 22, and the relative movement distance between the hall sensor 3y and the magnet 31y is set. The corresponding voltage is detected.

  Further, the camera module 40 shown in FIG. 9 detects the position of the lens 21 from the magnetic flux change caused by the movement of the magnets 31x and 31y used in the optical camera shake correction system in the small camera. In the camera module 40, when the magnets 31x and 31y move in the X-axis direction and the Y-axis direction, the position detection accuracy may deteriorate due to the displacement in the other axis direction. In order to reduce the deterioration of the detection accuracy in the detection axis direction due to the displacement in the other axis direction, the width W ″ of the position detection magnet is set to the direction perpendicular to the detection axis direction of the magnet in the moving plane. In other words, a measure to increase in the direction of the other axis was common. That is, the magnet 31x is widened in the other axis direction Y-axis direction perpendicular to the detection axis direction, and the magnet 31y is widened in the other axis direction X-axis direction perpendicular to the detection axis direction.

JP 2008-76193 A

  However, the above-described measures for increasing the size of the magnet in the other axis direction conflicts with the demands for reducing the size and weight of the product and reducing the cost. Therefore, the optical camera shake incorporated in a small and light camera module incorporated in a mobile phone or the like. The correction system has a problem that it is difficult to apply. The present invention has been made to solve such a problem, and it is possible to reduce deterioration in detection accuracy in the detection axis direction due to displacement in the other axis direction without increasing the size of the position detection magnet. An object of the present invention is to provide a position detecting device.

According to a first aspect of the present invention, there is provided a permanent magnet attached to an object whose position is to be detected and arranged so as to be movable in the detection axis direction, and a magnetic detection element for detecting a magnetic flux density generated by the permanent magnet. And a position detecting device for detecting the position of the object based on a detection value of the magnetic detection element, wherein the outer surface of the permanent magnet has a direction perpendicular to the detection axis direction on a reference surface facing the magnetic detection element. A magnetic flux density reduction part is provided at the center, and the permanent magnet is arranged such that the N pole and the S pole are distributed in the detection axis direction, and the area where the N pole is formed and the area where the S pole is formed are adjacent to each other. The two permanent magnets are arranged so as to be spaced apart so that the same poles are aligned, and the magnetic flux density reducing unit includes the two permanent magnets. this is the was placed apart from the configuration The features.

  According to this configuration, the central portion of the outer surface of the magnet in the direction orthogonal to the detection axis direction on the reference surface facing the magnetic detection element is the center where the magnetic flux density is high and lacks flatness. By providing the magnetic flux density reduction part of the part, there is an effect that the magnetic flux density distribution near the magnetic detection element is flattened in the direction of the other axis. As described above, the relationship between the detection output of the magnetic detection element that moves vertically and horizontally along a plane parallel to the surface of the magnet whose magnetic flux density distribution is flattened, and the movement distance is the detection output by the displacement in the other axis direction. It is easy to maintain a proportional relationship (linear) over a wider movement range without causing fluctuations. Therefore, it is possible to reduce deterioration in detection accuracy in the detection axis direction due to displacement in a direction other than the detection axis direction (other axis direction).

Further, the magnetic flux density distribution can be flattened in a wider range with respect to directions other than the detection axis direction (other axis directions). Therefore, it is possible to more reliably reduce the deterioration in detection accuracy in the detection axis direction due to displacement in a direction other than the detection axis direction (other axis direction).

A second aspect of the present invention is the invention according to the first aspect , wherein the magnetic detection element is a Hall sensor. According to this configuration, an inexpensive and high-performance position detection device can be provided.
According to a third aspect of the present invention, in the invention according to the first or second aspect, the distance G from the reference plane to the magnetosensitive surface of the magnetic detection element and the center of the permanent magnet parts on both sides sandwiching the magnetic flux density reducing portion The relationship between the distance D, the width W in the direction perpendicular to the magnetization direction on the reference surface of the permanent magnet, and the width Sp of the magnetic flux density reducing portion satisfies the following expressions (1) to (4). It is characterized by.

0.6 mm <G <2.1 mm (1)
0.1 mm <Sp (2)
When W ≦ 1.5 mm, D = (Sp + W) <0.5 × G + 2 (3)
When 1.5 mm <W, 1.6 mm <D <3G ≦ 2.8 mm (4)

  According to this structure, it is easy to manufacture without hindering mass production. In addition, the magnetic flux density distribution can be flattened more reliably in directions other than the detection axis direction (the other axis direction). Therefore, it is possible to provide a position detection device that can more reliably reduce deterioration in detection accuracy in the detection axis direction due to displacement in a direction other than the detection axis direction (other axis direction) at low cost.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the position detection apparatus which can reduce more reliably the detection accuracy deterioration of the detection-axis direction by the displacement of directions other than a detection-axis direction (other-axis direction) more inexpensively.

It is the schematic perspective view which applied the position detection apparatus concerning a 1st embodiment of the present invention to a camera module. It is comparison explanatory drawing of the position detection apparatus which concerns on 1st Embodiment of this invention, and a prior art example, (a) The conventional non-measure example, (b) The conventional measure example, (c) This invention is shown. . It is explanatory drawing contrasting with the position detection apparatus which concerns on 1st Embodiment of this invention, and a prior art example, (a) The example of a countermeasure conventionally and (b) This invention are shown. It is a performance contrast graph of the position detection apparatus which concerns on 1st Embodiment of this invention, and a prior art example, (a) The conventional countermeasure example and (b) This invention are shown. FIG. 5 is various simulation graphs of the position detection apparatus according to another embodiment of the present invention. (A) When W = 0.5 mm, G = 1.3 mm, Sp = 1.7 mm, and (b) A case where W = 1.5 mm, G = 1.3 mm, and Sp = 0.85 mm, and (c) a design index (SP adapted to W and G) are shown. It is the data which shows the relationship of the magnetic flux with respect to the width | variety of the magnet used for a position detection apparatus, (a) Graph of magnetic flux density distribution according to magnet width W '', (b) Displacement of the other axial direction according to magnet width W '' 3 shows a graph of the rate of change in magnetic flux density due to the above and (c) a table explaining the performance of the present embodiment. It is a graph which shows the design parameter | index of the position detection apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the shape of the magnet which is not limited to a rectangular parallelepiped for the position detection apparatus which concerns on other embodiment of this invention. It is the schematic perspective view which applied the position detection apparatus concerning a prior art to the camera module.

(First embodiment)
A first embodiment according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic perspective view in which the position detection apparatus according to the first embodiment of the present invention is applied to a camera module. Since the present invention is applied to the conventional example shown in FIG. Parts are denoted by the same reference numerals.

  The camera module 20 shown in FIG. 1 is fixed in parallel along a lens 21, a lens frame 22 that supports the lens 21, and side surfaces 22x and 22y of the lens frame 22 with a distance of two spaces Sp. A rectangular parallelepiped magnet 1, 2, a Hall sensor 3 disposed near the center of the magnets 1 and 2 in the magnetizing direction so as to face each other with a gap G, and a substrate 11 for fixing these Hall sensors 3. , Is configured.

  The positional relationship among the magnet 1, the magnet 2, and the hall sensor 3 will be described in detail later. In FIG. 1, there is a possibility of misunderstanding that the magnet 2 floats without being supported anywhere, but the fixing means for the magnet 2 is simply omitted from the drawing. That is, the main part of the position detection device 10, 10 y moves in conjunction with the lens frame 22. On the side surfaces 22x and 22y of the lens frame 22, the nearest magnet 1 and the magnet 2 fixed in parallel with a distance Sp from the magnet 1 are fixed.

Further, the position detection device 10 in the X axis direction is disposed along the side surface 22x, and the position detection device 10y in the Y axis direction is disposed along the side surface 22y. The position detection device 10 and the position detection device 10y have a relationship in which the position detection direction is replaced with the X axis and the Y axis. Therefore, hereinafter, only the position detection device 10 will be described, and description regarding the position detection device 10y will be omitted. On the other hand, even when the position detection devices 10 and 10y are arranged in a diagonal positional relationship in a space provided by cutting off the corners of the lens frame 22, the same operational effects as in this embodiment can be obtained.
In the present embodiment, the magnetizing directions of the magnets 1 and 2 of the position detecting device 10 and the position detecting device 10y are substantially the same as the direction of detecting the position (detection axis direction). And in the vicinity of the central portion in the direction orthogonal to the detection axis direction of the position detection device 10y, the gap G is disposed so as to face each other.

  The lens frame 22 is supported by support means (not shown) so as to be swingable within a certain range along the X axis direction and the Y axis direction with respect to the substrate 11 so as to make use of the camera shake correction function. Yes. Since the camera module 20 has an autofocus function in addition to the camera shake correction function, the entire camera module 20 shown in FIG. 1 also operates in the Z-axis direction, but the description thereof is omitted. The gap G is always constant, and the position detection device 10 detects the distance that the lens frame 22 moves in the X-axis direction with respect to the substrate 11. The position detection device 10 includes a Hall sensor 3 fixed on the substrate 11 and magnets 1 and 2 fixed to the side surface 22x of the lens frame 22. A voltage corresponding to the relative movement distance is detected.

  With this configuration, a gap R is provided in the width direction of the magnets 1 and 2 having a high magnetic flux density, that is, the center in the Y-axis direction other than the detection axis direction (the other axis direction) to reduce the magnetic flux density. There is an effect of flattening the magnetic flux density distribution in the direction other than the detection axis direction (the other axis direction) near the sensor 3. The detection output of the Hall sensor 3 that moves vertically and horizontally along a plane parallel to the reference plane A of the magnets 1 and 2 having a flat magnetic flux density distribution becomes linear over a wider movement range. Therefore, it is possible to prevent deterioration in position detection accuracy in the detection axis X direction due to displacement in the Y direction other than the detection axis X direction.

  1 includes two axes, an X axis and a Y axis, in a three-dimensional space defined by an orthogonal X axis, a Y axis, and a Z axis, respectively. When the relationship between the detection axis direction and the other axis direction is only the X axis and the Y axis with respect to the XY plane, that is, the reference plane A, the detection axis is caused by displacement in a direction other than the detection axis direction (other axis direction). The effect of reducing the deterioration of direction detection accuracy is exhibited.

  FIG. 2 is an explanatory diagram for comparing the position detection device according to the first embodiment of the present invention and the conventional example, in which (a) an example of conventional countermeasures, (b) an example of conventional countermeasures, and (c) the present invention. FIG. 2 is a perspective view of the upper half of FIG. 2, and a side view of the lower half of FIG. In FIG. 2, the direction in which the Hall sensor 3 detects a position by relatively displacing the magnets 1, 2, 4, and 5, that is, the detection axis direction is the X axis, and the direction other than the detection axis direction (the other axis direction). ) Is defined as the Y axis. In FIG. 2, the magnets 1, 2, 4, 5 and the hall sensor 3 are shown in an enlarged manner. The widths W, W ′, W ″ in the Y-axis direction of the magnets 1, 2, 4, 5, one or two or two magnets in each device, and the interval Sp between them, The distance G between 2, 4, 5 and the hall sensor 3 is clarified. The magnets 1, 2, 4, and 5 have the same length in the X-axis direction as (a), (b), and (c) in FIG.

  In the position detection device 39 shown in FIG. 2A, the square bar-like magnet 4 is magnetized in the longitudinal direction, and the front side of the figure is the N pole and the back side of the figure is the S pole. As clearly shown in the side view of the lower part of FIG. 2A, the Hall sensor 3 is arranged with a gap G from the upper surface of the magnet 4. Note that the position detection devices 39, 30x, 10 shown in FIG. 2 are reversed in the vertical relationship between the magnets 1, 2, 31x and the hall sensor 3 in the position detection devices 10, 30x shown in FIGS. However, the function for detecting the relative position remains the same.

  That is, the position detection device 39 measures the distance that the Hall sensor 3 arranged with a gap G on the upper surface of the magnet 4 moves in the X-axis direction. The position detection device 39 detects the distance that the magnet 4 moves relative to the hall sensor 3. In addition, even if either one is fixed and only the other moves, the description on the fixed side and the moving side may be opposite to the actual one, but this point is not related to the present invention. It is not a problem.

  On the upper surface of the magnet 4 of the position detection device 39 shown in FIG. 2A, the Hall sensor 3 not only moves in the X-axis direction but also moves in the Y-axis direction. That is, the displacement in the other axis direction deteriorates the position detection accuracy in the X axis direction. Therefore, the position detection device 30x shown in FIG. 2B has been used as a conventional countermeasure. The width W ″ of the magnet 5 of the position detection device 30x shown in FIG. 2B is expanded about three times the width W ′ of the magnet 4 of the position detection device 39 shown in FIG. . The fact that it is possible to reduce the effect of reducing the deterioration of the position detection accuracy in the detection axis direction due to the displacement in the other axis direction other than the detection axis will be described later based on the data shown in FIG.

  The magnets 1 and 2 of the position detection device 10 shown in FIG. 2 (c) are in the shape of a square bar, and the same two magnets are spaced apart by a distance Sp in the width W direction, along the reference plane A including the X axis and the Y axis. Thus, each one surface is arranged to be flush with each other. Further, the position detection device 10 is located near the center of the magnetizing direction of the square bar-like magnets 1 and 2 and near the center of the gap R having the interval Sp in the width W direction, and is the distance from the reference plane A to the gap G. The hall sensor 3 is arranged so as to face away from each other. The square bar shape is a shape of a rectangular parallelepiped.

  Moreover, the positional relationship among the magnet 1, the magnet 2, and the hall sensor 3 is disclosed in the best form by the design index shown by the following formulas (1) to (4). In addition, in the actual product, the magnetic sensitive surface of the Hall sensor 3 is disposed at the center of the depth defined from the outer surface of the mold package. However, in each drawing including FIG. 2, the magnetic sensor-sensitive surface of the Hall sensor 3 is regarded as being located on the surface where the Hall sensor 3 faces the magnet, thereby simplifying the illustration.

  The positional relationship between the magnet 1, the magnet 2 and the hall sensor 3 is such that the distance (also referred to as a gap) from the reference plane A to the magnetosensitive surface of the hall sensor 3 is G, and the gap R (magnetic flux density reduction part) is sandwiched between both sides. A line segment obtained by projecting a line segment connecting the centers of the magnet 1 and the magnet 2 onto the reference plane A is a distance D between the centers, and a width in a direction perpendicular to the magnetization direction of the magnet 1 and the magnet 2 on the reference plane A. It is preferable that the following formulas (1) to (4) are satisfied, where W is Sp and the distance between the magnet 1 and the magnet 2 on the reference plane A (the width of the gap R that is a magnetic flux density reduction portion) is Sp.

0.6 mm <G <2.1 mm (1)
0.1 mm <Sp (2)
When W ≦ 1.5 mm, D = (Sp + W) <0.5 × G + 2 (3)
When 1.5 mm <W, 1.6 mm <D <3G ≦ 2.8 mm (4)

  The basis for numerical limitation by the above formulas (1) to (4) is that the best design index is based on experimental results of trial and error with simulation verification, as will be described later with reference to FIGS. It is the result of having found. For example, the above equation (1) is a result of finding a practical area where the sensitivity of the Hall sensor 3 is good. On the other hand, the above equation (2) indicates the constraint condition in production technology when mass production such as gap management is performed rather than the experimental result.

  FIG. 3 is an explanatory diagram for comparing the position detection device according to the first embodiment of the present invention and the conventional example, and shows (a) a conventional countermeasure example and (b) the present invention. In FIG. 3, the horizontal axis indicates the position along the non-measurement axis direction (also referred to as other axis direction or Y-axis direction) that is the width direction of the magnets 1, 2, and 5. A central portion in the front-rear direction of the rectangular magnet 5 shown in FIG. 3A is a boundary portion of the magnetic pole NS and schematically shows a boundary line. Similarly, the central portion in the longitudinal direction of the square bar-shaped magnets 1 and 2 shown in FIG. 3B is a boundary portion of the magnetic pole NS and schematically shows the boundary line. The intermediate point of the width W ″ of the magnet or the intermediate point of the total value (2 × W + Sp) of the width W of the magnets 1 and 2 and the interval Sp of the magnets 1 and 2 is set as the reference point 0, and the other axis The position displaced in the direction is shown on the horizontal axis of the graph shown in FIG.

  Moreover, the vertical axis | shaft of Fig.3 (a), (b) has shown the magnetic flux density. However, the graph shown in FIG. 3 is used to verify whether the magnetic flux density characteristics are mountain-shaped or flat with respect to the other axis direction. Therefore, the curve shape of the graph shown in FIG. 3 is the verification result, and each numerical value represents the magnetic flux density in units of T (Tesla). In the graph of FIG. 3A, since the magnetic flux density changes in a mountain shape, it is shown that the position detection accuracy in the detection axis direction is greatly deteriorated due to the displacement in the other axis direction other than the detection axis. That is, under the condition of the magnet width W ″ = 3 mm, it is shown that the position detection accuracy in the detection axis direction is inevitably deteriorated due to the displacement in the other axis direction. In addition, the graph of Fig.3 (a) is one shown on the conditions of W '' = 3mm among the curves described in Fig.6 (a) demonstrated later.

  On the other hand, FIG. 3B is a graph of the position detection device 10 disclosed as the best embodiment and a simulation result thereof. The position detection device 10 is provided with two rectangular bar-shaped magnets 1 and 2 having a magnet width W = 1.0 mm, and the distance Sp between these magnets 1 and 2 is set to 1.1 mm. As shown in the graph, the characteristic curve of the magnetic flux density is trapezoidal, and the upper part is substantially flat in the range of displacement ± 1 mm in the other axis direction. Therefore, the position detection device 10 disclosed in FIG. 3B can reduce deterioration in position detection accuracy in the detection axis direction due to the displacement in the other axis direction other than the detection axis in the range of displacement ± 1 mm in the other axis direction. Proved.

  FIG. 4 is a performance comparison graph between the position detection apparatus according to the first embodiment of the present invention and the conventional example, and shows (a) a conventional countermeasure example and (b) the present invention. The horizontal axis in FIG. 4 is the movement distance (also referred to as a stroke) of the X axis that is the detection axis direction of the position detection devices 30x and 10. The vertical axis in FIG. 4 represents the voltage V before amplification with respect to the detection outputs of the position detection devices 30x and 10. The purpose of the graph shown in FIG. 4 is to verify whether the characteristics of the stroke vs. detection output are linear, and the unit of the vertical axis is not a problem. It is. In addition, since the actual detection voltage can be changed in any way by the setting of the amplifier circuit, the numerical value on the vertical axis has no particular meaning. 1 to 4, the magnetization direction of the magnet has been described based on a so-called two-pole magnet in which the N pole and the S pole are magnetized in parallel with the detection axis direction. The effect of the present invention can be achieved by using a so-called four-pole magnetized magnet in which the N and S poles are magnetized in the direction (Z-axis direction in FIG. 1) and the magnetization direction is reversed at the center of the detection axis direction. Will not change.

  As shown in FIG. 4A, in the position detection device 30x, in the region where the stroke of the X axis is 0 to 0.5 mm, the detection output when the displacement in the other axis direction is 0 mm, that is, there is no displacement in the other axis direction. When the voltage is compared with the detected output voltage when the displacement in the other axis direction is 0.5 mm, they are different. That is, the position detection accuracy of the position detection device 30x deteriorates due to the displacement in the other axis direction.

  As shown in FIG. 4B, in the position detection device 10, the displacement in the other axis direction is 0 mm, that is, the case in which there is no displacement in the other axis direction, the case in which the displacement in the other axis direction is 0.5 mm, and the other axis direction. Compared with the case of 1.0 mm displacement. As a result, the detected output voltage changes in a similar manner with respect to the stroke regardless of the displacement value in the other axis direction over the stroke of about 3 mm on the X axis, and the detected output voltage in each stroke is almost equal. Is obtained. In other words, the position detection device 10 proved that the position detection accuracy did not deteriorate even when the detected output voltage was displaced by ± 1 mm in the other axis direction over a stroke of about 3 mm.

(Other embodiments)
FIG. 5 is various simulation graphs of the position detection apparatus according to another embodiment of the present invention. (A) When W = 0.5 mm, G = 1.3 mm, Sp = 1.7 mm, and (b) A case where W = 1.5 mm, G = 1.3 mm, and Sp = 0.85 mm, and (c) a design index (SP adapted to W and G) are shown. As described above, FIG. 3B shows the conditions considered to be the best of the position detection device 10. However, an optimum SP value corresponding to the W value and the G value obtained by changing the positional relationship among the magnet 1, the magnet 2, and the hall sensor 3 to different conditions is searched for as a design index. In FIG. 5, the horizontal axis indicates the position mm in the other axis direction, and the vertical axis indicates the magnetic flux density T. FIG. 5A shows that the magnetic flux density characteristics under the conditions of magnet width W = 0.5 mm and separation distance Sp = 1.7 mm between magnets 1 and 2 are slightly flat.

  FIG. 5B shows the magnetic flux density characteristics under the condition of the magnet width W = 1.5 mm and the separation distance Sp = 0.85 mm between the magnets 1 and 2 over a displacement of about 3 mm in the other axis direction. Thus, the magnetic flux density is almost flat in the plateau state, and the grounds for reducing the deterioration of the position detection accuracy due to the displacement in the other axis direction have been proved. Further, the table shown in FIG. 5C shows the magnet width W, the gap G from the reference plane A to the magnetically sensitive surface of the Hall sensor 3, and the magnet 1 in the position detection device 10 shown in FIG. , 2 is optimized with respect to the separation distance Sp. That is, it is a design index in which the optimum Sp value for the W value and G value is determined by trial and error.

  FIG. 6 is data showing the relationship of the magnetic flux density with respect to the width of the magnet used in the conventional position detecting device. (A) Graph of magnetic flux density distribution according to magnet width W ″, and (b) Magnet width W ″. The graph of the rate of change of another magnetic flux density and the table explaining the performance of (c) this embodiment are shown. The conventional position detection device 30x has the shape shown in FIG. 2B and FIG. 3A, and the position detection device 10 according to the present embodiment has the shape shown in FIG. It is the shape shown in b).

  The horizontal axis of FIG. 6A indicates a position other than the detection axis direction that is the width direction of the magnet 5, that is, a position along the Y direction that is the other axis direction, that is, a position in the other axis direction. The horizontal axis in FIG. 6A shows the displacement in the Y direction in the other axis direction from the middle point of the width W ″ of the rectangular magnet 5. The vertical axis in FIG. 6A indicates the magnetic flux density T. In FIG. 6 (a), seven generally chevron curves with different curvatures show the simulation results when the widths W ′ and W ″ of the magnet are changed to 1, 3, 5, 6, 7, 10 mm and others. ing. Of the seven curves shown in FIG. 6A, one shown under the condition of W ″ = 3 mm is as described in the graph of FIG.

  In FIG. 6A, when the magnet width W ′ = 1 mm, the magnetic flux density changes to a low mountain shape, but when the magnet width W ″ = 10 mm, the magnetic flux density keeps a high value and has a substantially flat characteristic. is there. As described above, if the magnetic flux density is substantially flat with respect to the displacement in the other axis direction, the position detection accuracy is not deteriorated due to the displacement in the other axis direction of the position detection device. It was verified that 10 mm, which is wider than 1 mm, which is narrower, can easily eliminate the deterioration of position detection accuracy due to displacement in the other axis direction. That is, it is shown that as the magnet width W ′ is increased with respect to the other axis direction, it is effective as a countermeasure for eliminating the deterioration of position detection accuracy due to the displacement in the other axis direction.

  In addition, the horizontal axis in FIG. 6B also shows the distance along the non-measurement axis direction which is the width direction of the magnet. And the vertical axis | shaft of FIG.6 (b) has shown the difference of the magnetic flux density of the magnet center part which is a measurement origin, and the magnetic flux density in a measurement point. In FIG. 6 (b), seven generally valley-shaped curves with different curvatures are the results of simulations with the magnet widths W ′ and W ″ changed to 1, 3, 5, 6, 7, 10 mm, and others. Show. In FIG. 6B, when the magnet width W ′ = 1 mm, the difference in the magnetic flux density changes to a deep valley shape, but when the magnet width W ″ = 10 mm, the rate of change of the magnetic flux density is slight, almost It is a flat characteristic. As described above, the flat rate of change in the magnetic flux density with respect to the other axis direction as described above is effective as a measure for eliminating the deterioration in position detection accuracy due to the displacement in the other axis direction. Has been.

  The table shown in FIG. 6C is the intermediate point of the width W ′ or W ″ of the magnet when displaced in the other axis direction by 1 mm in the graph shown in FIG. 6B, that is, the displacement in the other axis direction. The rate of change of the magnetic flux density when the magnetic flux density is 0 mm is taken as a reference for each W ″. According to this, in the conventional position detection device 30x, the position detection accuracy based on the displacement in the other axial direction obtained by using the large magnet 5 having the magnet width W ″ = 9 mm is used in the present embodiment. 1 and 2 show that the position detection apparatus 10 under the conditions of W = 1 mm and Sp = 1.3 mm can be realized. Note that the magnetic flux density difference data under the condition of the magnet width W ″ = 9 mm is not plotted in FIG.

  FIG. 7 is a graph showing a design index of the position detection apparatus according to the embodiment of the present invention. The horizontal axis in FIG. 7 indicates the distance (gap) Gmm from the reference plane A to the magnetic sensitive surface of the Hall sensor 3. That is, the gap G described with reference to FIG. 2C is indicated as the distance Gmm from the reference surface to the magnetosensitive surface on the horizontal axis of FIG. The vertical axis of FIG. 7 represents a center distance D = (magnet width W + magnet distance Sp) mm of a pair of magnets in a rectangular parallelepiped.

  The inventor of the present application has determined by experiment that, in the case of magnet width W = 0.5 mm, W = 1.0 mm, and W = 1.5 mm, the specific position associated with each magnet width W value It was confirmed that the detection device 10 can obtain high performance. Then, specific conditions under which the position detection device 10 can obtain high performance are plotted as a design index in the graph shown in FIG. 7, and the above equations (1) to (4) are used as the best mode shown in FIG. ) Is as limited in numerical values.

  According to this configuration, it is convenient for mass production, and the magnetic flux density distribution can be surely flattened in a direction other than the detection axis direction (the other axis direction). Therefore, it is possible to provide a position detection apparatus that can more reliably reduce the deterioration of position detection accuracy due to displacement in the other axial direction other than the detection axis direction at a low cost.

  FIG. 8 is a cross-sectional view showing the shape of a magnet not limited to a rectangular parallelepiped for a position detection device according to another embodiment of the present invention. However, as a basic configuration, FIG. 8A shows the pair of magnets 1 and 2 and the Hall sensor 3 that are in the shape of the square bar described above. And as shown to FIG.8 (b)-(d), (i), (k), the 1-pair structure by the rod-shaped magnet replaced with the rectangular parallelepiped is also considered. A gap R corresponding to the interval Sp is provided between these rod-shaped magnets. Also, as shown in FIGS. 8E to 8H, (j), (l), in the integrally formed magnet, a concave portion is formed at substantially the center of the reference surface A facing the Hall sensor 3 on the outer surface of the magnet. Q may be provided. In addition, like the magnet by the integral formation shown to FIG.8 (e)-(h), (j), (l), the plane without the recessed part Q has little fall of magnetic force. Therefore, the efficiency in the case where a driving coil for an actuator (not shown) constituting the camera shake correction function faces to generate a driving force is also good.

  According to this configuration, a concave portion or a gap is provided in the center of a magnet having a high magnetic flux density to reduce the magnetic flux density, and a magnetic flux density distribution in a direction other than the detection axis direction (the other axis direction) near the magnetic detection element is obtained. It has the effect of flattening. The detection output of the magnetic detection element that moves in the vertical and horizontal directions along a plane parallel to the surface of the magnet whose flat magnetic flux density distribution in the other axis direction is detected in the detection axis direction due to displacement in the other axis direction other than the detection axis direction. It is possible to prevent deterioration in position detection accuracy.

1, 2, 4, 5 Magnets 3, 3x, 3y Hall sensors 10, 30x, 10y, 39 Position detector A Reference plane D Center-to-center distance G Gap Q Recessed part (magnetic flux density reducing part)
R Air gap (magnetic flux density reduction part)
Sp interval W Magnet width

Claims (3)

A permanent magnet attached to the object whose position is to be detected and arranged so as to be movable in the detection axis direction;
A magnetic detection element for detecting a magnetic flux density generated by the permanent magnet,
In the position detection device that detects the position of the object based on the detection value of the magnetic detection element,
A magnetic flux density reduction unit is provided at the center of the outer surface of the permanent magnet in the direction orthogonal to the detection axis direction on the reference surface facing the magnetic detection element ,
The permanent magnets are two permanent magnets that are magnetized so that N poles and S poles are distributed in the detection axis direction, and a region where the N poles are formed and a region where the S poles are formed are adjacent to each other. Yes, with a configuration in which these two permanent magnets are spaced apart so that the same poles are aligned,
The magnetic flux density reducing unit has a configuration in which the two permanent magnets are arranged apart from each other . The position detection device according to claim 1, wherein the magnetic detection element is a Hall sensor. The distance G from the reference surface to the magnetic sensing surface of the magnetic detection element, the distance D between the centers of the permanent magnet portions on both sides of the magnetic flux density reduction portion, and the magnetization direction of the permanent magnet on the reference surface 3. The position detection according to claim 1, wherein the relationship between the width W in the orthogonal direction and the width Sp of the magnetic flux density reduction unit satisfies the following expressions (1) to (4): apparatus.
0.6 mm <G <2.1 mm (1)
0.1 mm <Sp (2)
When W ≦ 1.5 mm, D = (Sp + W) <0.5 × G + 2 (3)
When 1.5 mm <W, 1.6 mm <D <3G ≦ 2.8 mm (4)

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