JP6073734B2 - Straight line moving body position detection device - Google Patents

Description

  The present invention relates to a position detection device for a rectilinear moving body that is moved by a linear drive mechanism including permanent magnets and coils.

  For example, a camera is known in which a focusing lens group (a linearly moving body) of a photographing lens is driven straight by a voice coil motor (linear drive mechanism) using permanent magnets and coils instead of a feed screw mechanism that converts rotational motion into linear motion. ing. In this linear drive mechanism, it is possible to detect the position of the rectilinear moving body by mounting a Hall element on the rectilinear moving body and using the permanent magnet of the linear drive mechanism as a permanent magnet for position detection.

  Patent Document 1 describes a unit of a rectilinear moving body by fixing and inclining a long side direction of a permanent magnet having a rectangular parallelepiped shape with respect to a line segment connecting the centers of a pair of Hall elements mounted on the rectilinear moving body. A highly accurate position detection mechanism with a large change in the output of the Hall element per movement is proposed.

International Publication No. 2007/069680

  However, the configuration of Patent Document 1 is effective when the moving distance of the rectilinear moving body is small, but when the moving distance of the rectilinear moving body becomes large, a sufficient output change of the Hall element cannot be obtained, that is, There is a problem that the magnetic flux density change detected by the Hall element is insufficient and accurate position detection cannot be performed.

  The present invention is a position detection mechanism for a rectilinear moving body that is moved by a linear drive mechanism using permanent magnets and coils based on the above awareness of the problem, and ensures a change in output of the Hall element over a longer moving distance. An object of the present invention is to obtain a position detection device with high position detection accuracy.

  The present invention focuses on the fact that the change in the magnetic flux of the permanent magnet detected by the Hall element will increase if the distance between the Hall element and the permanent magnet changes three-dimensionally with respect to the moving direction of the Hall element. And completed. That is, the present invention is a rectilinear moving body supported so as to be linearly movable in the Z direction of an XYZ orthogonal triaxial coordinate system; a coil supported by the linearly moving body and having a winding center parallel to the Z direction; A coil insertion portion that is inserted into the coil so as to be relatively movable, a yoke made of a magnetic material integrated with a permanent magnet; and a linearly moving body fixed to a portion that receives the magnetic flux of the permanent magnet The permanent magnet has a rectangular parallelepiped shape having front and back surfaces, both side surfaces in the length direction, and both end surfaces, and magnetizes NS on the front and back surfaces or both side surfaces. The front and back surfaces of the magnet are non-parallel to the movement direction of the Hall element in the YZ section, and are inclined with respect to the Z direction, and both side surfaces of the permanent magnet are For the direction of movement No parallel, that is inclined with respect to the Z direction, characterized by.

  The permanent magnet is inclined so that the front and back surfaces of the permanent magnet are widened from one moving end to the other moving end of the rectilinear moving body, and both side surfaces thereof are the one moving end of the rectilinear moving body. To the other moving end so as to increase the distance from the Hall element.

  The permanent magnet is inclined so that the front and back surfaces of the permanent magnet are shortened from one moving end to the other moving end of the rectilinear moving body, and both side surfaces thereof are the one moving end of the rectilinear moving body. And the other moving end are inclined so as to reduce the distance from the Hall element.

  The yoke insertion portion of the yoke is preferably parallel to the front and back surfaces of the permanent magnet.

  It is practical to make the coil insertion portion of the yoke parallel to the Z direction.

  The position detection device for a rectilinear moving body of the present invention can be applied to a focusing lens group of a lens barrel as a rectilinear moving body.

  According to the present invention, there is provided a position detection mechanism for a rectilinear moving body that is moved by a linear drive mechanism using a permanent magnet and a coil, and the permanent magnet of the linear drive mechanism cooperates with a Hall element mounted on the rectilinear moving body. It is possible to obtain a position detection device with high position detection accuracy that can ensure a change in the output of the Hall element over a longer moving distance of the rectilinear moving body while being shared with a working position detection permanent magnet.

It is a disassembled perspective view which shows one Embodiment which applied the position detection apparatus of the linearly moving body by this invention to the position detection apparatus of the focusing lens group of a lens-barrel. It is a disassembled perspective view which shows the assembly state in the middle of the lens barrel of FIG. It is the disassembled perspective view which looked at FIG. 2 from the different direction. FIG. 1A is a front view and FIG. 2B is a rear view in which a guide shaft, a focusing lens frame, a yoke, a permanent magnet, and a hall element are extracted from the lens barrel of FIGS. A state in which the focusing lens frame is located farthest in the optical axis direction (imaging plane side) and is drawn by extracting the guide shaft, focusing lens frame, yoke, permanent magnet and Hall element from the lens barrel of FIGS. FIG. FIG. 6 is a side view of the focusing lens frame in a state where the focusing lens frame is positioned in the forefront (subject side) in the optical axis direction. (A) is a side view drawn by extracting the guide shaft, yoke, permanent magnet and Hall element from FIGS. 5 and 6, and (B) is a plan view drawn with one yoke removed. It is the figure which showed the relationship between Hall element position and Hall element output of embodiment shown in FIG. 7 and a prior art example with the graph. (A) of the 2nd Embodiment of this invention is a side view corresponding to FIG. 7 (A), (B) is a top view corresponding to FIG. 7 (B). (A) of the 3rd Embodiment of this invention is a side view corresponding to FIG. 7 (A), (B) is a top view corresponding to FIG. 7 (B).

  1 to 7 show an embodiment in which the position detecting device for a linearly moving body according to the present invention is applied to the position detecting device for the focusing lens group L1 of the lens barrel 100. FIG. The illustrated embodiment is intended to depict only the guide mechanism and position detection device of the focusing lens group L1, and the configuration of the other parts is omitted.

  The lens barrel 100 has, as a fixed member, a fixed substrate 32 that fixes an image sensor 31 and the like that forms a subject image formed by a photographing lens system including the focusing lens group L1, and a fixed ring that supports a movable lens frame member. 33. The rear end portions of the two guide shafts 34 and 35 parallel to the optical axis O are fixed to the image sensor 31, and the front end portions of the guide shafts 34 and 35 are lens frame members positioned in the fixed ring 33. (Not shown).

  A movable lens frame (linearly moving body) 10 to which the focusing lens group L1 is fixed has a cylindrical frame portion 10a and a radial arm portion 10b. A cylindrical portion 10c to be fitted and a forked portion 10d slidably engaged with the guide shaft 35 are formed. Further, the coil 11 of the linear drive mechanism is fixed to the distal end portion of the radial arm portion 10b so as to be positioned between the cylindrical portion 10c and the bifurcated portion 10d. This coil 11 is a flat air-core coil whose winding center is in a direction parallel to the optical axis O. The movable lens frame 10 is formed with a horizontally long through hole 10e (FIGS. 1 and 4) having a shape corresponding to the coil 11.

  The magnet unit 20 constituting the linear drive mechanism is fixed to the fixed ring 33 together with the coil 11. The magnet unit 20 includes a holder 21, a pair of yokes 22 and 23, and a permanent magnet 24. The yoke 22 has a horizontally long through hole 10e of the movable lens frame 10 and a coil insertion portion (longitudinal wall) 22a that is inserted into the coil 11 (air core portion) in a non-contact manner (FIGS. 5 and 6). ), The coil insertion portion 22a (permanent magnet 24) and the coil 11 constitute a linear drive mechanism (voice coil motor). That is, when the coil 11 is energized in the forward and reverse directions, the movable lens frame 10 (focusing lens group L1) is moved in the optical axis O direction along the guide shafts 34 and 35 by the linear drive mechanism.

  The permanent magnet 24 of the magnet unit 20 described above constitutes a position detection device together with a hall element (hall sensor) 25 mounted on the movable lens frame 10. FIG. 7 shows the yokes 22 and 23, the permanent magnet 24, and the Hall element 25 taken out. 7A and 7B, an XYZ orthogonal triaxial coordinate system is employed. The Z direction is the same (parallel) as the optical axis O direction. The direction of the intersecting line where the surface perpendicular to the Z direction and the surface 24a of the permanent magnet 24 intersect is the X direction, and the directions of XYZ correspond to the XYZ axes shown in FIGS. 7 to 10 below, the left side is the rear (backward moving end) imaging surface side, the right side is the subject side, and the front (front moving end). 7, 9, and 10 show a state in which the hall element 25 is located at the rearward movement end position and the forward movement end position.

  The yokes 22 and 23 have symmetrical L-shaped cross sections. That is, the yokes 22 and 23 include the coil insertion portion 22a and the longitudinal wall 23a that are slightly inclined with respect to the Z direction, and the transverse walls 22b and 23b orthogonal to the coil insertion portion 22a and the longitudinal wall 23a. The coil insertion portion 22a and the longitudinal wall 23a are coupled so as to be parallel to each other (that is, so as to draw a closed section with the yokes 22 and 23). The horizontally long through hole 10e of the movable lens frame 10 and the coil insertion portion 22a inserted into the coil 11 are not parallel to the Z direction, but the inner diameter of the horizontally long through hole 10e and the coil 11 is Z of the movable lens frame 10. It is determined to be non-contact with the coil insertion portion 22a in the entire movement region in the direction. Further, the Hall element 25 is disposed in a portion that receives the magnetic flux of the permanent magnet 24 (a position where the magnetic flux can be detected) in the entire movement region of the movable lens frame 10 in the Z direction, and is closed by the yokes 22 and 23. Move through.

  The permanent magnet 24 is fixed on the longitudinal wall 23a of the yoke 23 (surface facing the coil insertion portion 22a). The permanent magnet 24 has a rectangular parallelepiped shape having a front surface 24a and a back surface 24b that are parallel to each other, both side surfaces 24c and 24d that are parallel to each other, and both end surfaces 24e and 24f that are parallel to each other. Is magnetized (the front surface 24a and the back surface 24b are magnetized to NS). The magnetizing direction may be both side surfaces 24c and 24d as long as the direction is perpendicular to the moving direction of the movable lens frame 10, and the surface in contact with the yoke is magnetized in NS.

The permanent magnet 24 is inclined with respect to the Z direction as follows.
As shown in FIGS. 5 to 7A, the front surface 24a and the back surface 24b of the permanent magnet 24 are not parallel to the moving direction (Z direction) of the Hall element 25 (movable lens frame 10) in the YZ section. There is no. The permanent magnet 24 has front and back surfaces 24a and 24b and a hall element 25 from the rear moving end (image forming side, left side in the figure) toward the front moving end (subject side, right side in the figure) with respect to the Z direction. Is inclined at an angle α in the direction of gradually increasing the distance.
Further, as shown in FIG. 7B, both side surfaces 24c and 24d of the permanent magnet 24 are not parallel to the moving direction of the Hall element 25 (movable lens frame 10) in the XZ section. The permanent magnet 24 has an angle β in the direction of gradually increasing the distance between the side surface 24c and the Hall element 25 from the rear moving end (left side in the figure) toward the front moving end (right side in the figure) with respect to the Z direction. Inclined. The angle β in the illustrated embodiment is approximately 12 °.
Since the angle α and the angle β are inclined so that the magnetic flux density detected by the Hall element 25 gradually decreases when the movable lens frame 10 moves from the rear to the front, the movable lens frame 10 moves from the rear moving end to the front moving end. As it moves in the direction, the output of the Hall element 25 gradually decreases (substantially linearly). The angles α and β are positive when the magnetic flux density received by the Hall element 25 decreases when the Hall element 25 moves from rear to front, and negative when the Hall element 25 increases. In this case, the angles α and β in the first embodiment are positive.

  FIG. 8 shows a graph in which the relationship between the movement position of the Hall element 25 and the output of the Hall element 25 is measured in the first embodiment described above. In the graph, the horizontal axis represents the movement (Z direction) position of the Hall element 25, the vertical axis represents the output value of the Hall element 25, the solid line represents the Hall element output value of the present invention (first embodiment), and the broken line represents the conventional value. It is a Hall element output value of the apparatus. As for the movement direction of the Hall element 25, the left direction is rearward and the right direction is frontward in FIG.

  As can be seen from this graph, in the first embodiment of the present invention, the movement direction of the Hall element 25 is inclined at the inclination angles α and β from the Z direction in the XZ cross section and the YZ cross section. The maximum value is larger than the Hall element output value of the conventional example. According to the first embodiment, the change in magnetic flux density received by the Hall element 25 is larger than in the conventional example, and the difference in the output value (voltage) of the Hall element 25 is increased, thereby further improving the position detection accuracy. Can be achieved. In the first embodiment, the movement range of the Hall element 25, that is, the rearward movement end position and the forward movement end position of the Hall element are set in a range in which the linearity of the Hall element output value can be secured.

  In the first embodiment, the Hall element 15 is arranged on one side surface 24d side of the permanent magnet 24 in a plan view (FIG. 7B). On the other hand, in the second embodiment, the Hall element 15 is arranged on the other side surface 24c side of the permanent magnet 24 in plan view (FIG. 9B). In the first embodiment and the second embodiment, the angles formed by the permanent magnet 24 (both side surfaces 24c and 24d thereof) and the Z direction are the same in plan view. In the second embodiment, in the XZ cross section, the distance between the side surface 24c of the permanent magnet 24 and the Hall element 25 is gradually increased from the rear moving end (left side in the figure) to the front moving end (right side in the figure) of the movable lens frame 10. Shrink to Accordingly, the output of the Hall element 25 gradually increases as the movable lens frame 10 moves from the rearward movement end (left side in the figure) to the forward movement end (right side in the figure). Therefore, in the second embodiment, in the YZ section, the distance between the surface 24a of the permanent magnet 24 and the Hall element 25 is gradually reduced, that is, the movable lens frame 10 is moved from the rear moving end (left side in the drawing) to the front moving end ( The permanent magnets 24 are inclined with respect to the Z direction so that the output of the Hall element 25 gradually increases as it moves to the right side of the figure (FIG. 9A). In the second embodiment, the angle formed between the movement direction (Z direction) of the Hall element 25 in the YZ section and the surface 24a of the permanent magnet 24 is α ′, and the movement direction (Z direction) of the Hall element 25 in the XZ section. If the angle formed by the side surface 24c of the permanent magnet 24 is β ′, the angles α ′ and β ′ are negative. According to the second embodiment, as the movable lens frame 10 moves from the rear movement end to the front movement end, the output of the Hall element 25 gradually increases (substantially linearly).

  As described above, the permanent magnet 24 is not parallel to the moving direction of the movable lens frame 10 in the YZ section and is not only inclined with respect to the Z direction but also in the XZ section with respect to the moving direction of the movable lens frame 10. By being non-parallel and tilting with respect to the Z direction, it is possible to increase the change in output while ensuring linearity in the output of the Hall element 25 in the entire movement range of the Hall element 25 (movable lens frame 10). it can.

  The coil insertion portion 22a of the yoke 22 of the first and second embodiments is parallel to the front surface 24a and the back surface 24b of the permanent magnet 24 and is not parallel to the moving direction (Z direction) of the coil 11 ( Inclined at angles α and α ′ with respect to the Z direction). On the other hand, in the third embodiment shown in FIGS. 10A and 10B, the coil insertion portion 22a ′ of the yoke 22 ′ is formed in parallel with the moving direction (Z direction) of the coil 11. . The angle formed by the movement direction (Z direction) of the Hall element 25 and the surface 24a of the permanent magnet 24 in the YZ section is α ″. The movement direction (Z direction) of the Hall element 25 and the surface 24a of the permanent magnet 24 in the XZ section. Is the same as that in the first embodiment (FIG. 10B). In this third embodiment, the angle α ″ and the angle β are positive. If the coil insertion portion 22a ′ of the yoke 22 ′ is formed in parallel with the Z direction, the clearance between the coil insertion portion 22a ′ and the air core portion of the coil 11 can be reduced, so that the first and second embodiments can be used. However, the coil 11 and the coil insertion portion 22a 'can be downsized.

  In the third embodiment, since the coil insertion portion 22a ′ of the yoke 22 ′ and the surface 24a of the permanent magnet 24 are non-parallel, the coil insertion portion 22a of the yoke 22 includes the surface 24a and the back surface 24b of the permanent magnet 24. The distribution of the magnetic flux density in the Z direction between the coil insertion portion 22a, the surface 24a, and both side surfaces 24c, 24d is different from the parallel illustrated embodiment. Therefore, the optimum angles α, α ′ between the first and second embodiments in which the coil insertion portion 22a ′ of the yoke 22 ′ is parallel to the surface 24a of the permanent magnet 24 and the non-parallel third embodiment. , Α ″, and angles β, β ′ are different from each other, and the optimum angles α, α ′, α ″, and angles β, β ′ are set by simulation.

According to the inventor's simulation, in the case of the first embodiment shown in the figure, when the angle β is approximately 12 °, the angle α is preferably in the range of 1 ° to 2 °. The optimum angles α ′, β ′, and angle α ″ vary depending on the size and shape of the permanent magnet 24 and the yokes 22 and 23, the distance between the permanent magnet 24 and the Hall element 25, etc., and are preferably determined by simulation.
In the present invention, the front and back surfaces of the permanent magnet are non-parallel to the movement direction of the Hall element in the YZ section, and are inclined with respect to the Z direction, and both side surfaces of the permanent magnet are in the XZ section. Although it is essential that the Hall element is not parallel to the moving direction of the Hall element and is inclined with respect to the Z direction, the inclination angle with respect to the Z direction in the YZ cross section and the XZ cross section is set individually.

  As described above, the embodiment in which the position detecting device for the linearly moving body according to the present invention is applied to the position detecting device for the focusing lens group that is moved by the linear driving mechanism of the photographing lens has been described. The present invention can be applied to a position detection device for a linearly moving body that is moved by a mechanism.

10 Movable lens frame (straight moving body)
10a Cylindrical frame portion 10b Radial arm portion 10c Tubular portion 10d Forked portion 10e Horizontally long through hole 11 Coil 20 Magnet unit 21 Holder 22 23 Yoke 22a Coil insertion portion (longitudinal wall)
22b Short direction wall 23a Longitudinal wall 23b Short direction wall 24 Permanent magnet 24a Front surface 24b Back surface 24c 24d Side surface 24e 24f End surface 25 Hall element 31 Image sensor 32 Fixed substrate 33 Fixed ring 34 35 Guide shaft

Claims (6)

A rectilinear moving body supported so as to be linearly movable in the Z direction of an XYZ orthogonal three-axis coordinate system;
A coil supported by the linearly moving body and having a winding center parallel to the Z direction;
A yoke made of a magnetic material integrated with a permanent magnet; and a portion that receives the magnetic flux of the permanent magnet; Hall element;
With
The permanent magnet has a rectangular parallelepiped shape having front and back surfaces, both side surfaces in the length direction, and both end surfaces, and the front and back surfaces or both side surfaces are magnetized in NS;
The front and back surfaces of the permanent magnet are non-parallel to the movement direction of the Hall element in the YZ section, and are inclined with respect to the Z direction, and both side faces of the permanent magnet are holes in the XZ section. It is non-parallel to the movement direction of the element and is inclined with respect to the Z direction.
A position detecting device for a linearly moving body characterized by the above. In the position detecting device of the rectilinear moving body according to claim 1, the permanent magnet is inclined and arranged such that the front and back surfaces increase the distance from the Hall element from one moving end to the other moving end of the rectilinear moving body, And the position detection apparatus of the rectilinear moving body by which both the side surfaces are inclinedly arranged so that the distance from a Hall element may be extended from said one moving end of the rectilinear moving body to the other moving end. In the position detecting device of the rectilinear moving body according to claim 1, the permanent magnet is inclined and arranged such that the front and back surfaces thereof reduce the distance from the Hall element from one moving end to the other moving end of the rectilinear moving body, And the position detection device of the rectilinear moving body whose both side surfaces are inclined so as to reduce the distance from the Hall element from the one moving end to the other moving end of the rectilinear moving body. 4. The position detecting device for a rectilinear moving body according to claim 1, wherein the coil insertion portion of the yoke is parallel to the front and back surfaces of the permanent magnet. 5. 4. The position detecting device for a rectilinear moving body according to claim 1, wherein a coil insertion portion of the yoke is parallel to the Z direction. 5. 6. The position detecting device for a rectilinear moving body according to claim 1, wherein the rectilinear moving body is a focusing lens group of a lens barrel.

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