JP7009167B2 - Drive device, optical equipment equipped with it, and lens barrel - Google Patents

Description

The present invention relates to a drive device capable of detecting the position of a drive target such as a lens using a magnet, an optical device provided with the drive device, and a lens barrel.

Optical equipment such as lens barrels use a so-called voice coil motor to perform zoom and focus operations as a drive device that drives multiple lens groups in the optical axis direction to enable high-speed / silent drive. (Patent Document 1).

A voice coil motor arranges a coil in a magnetic circuit consisting of a magnet and a yoke, and the coil moves relative to the magnet. By changing the current to the coil, the position of the coil relative to the magnet is changed. Is in control. Further, the current value to the coil when moving the lens to a predetermined position is not always constant, and changes depending on the posture of the lens barrel at that time. Therefore, in Patent Document 1, an encoder magnet and a position sensor are provided separately from the drive device, and the amount of energization to the coil is changed while detecting the position of the lens.

However, in Patent Document 1, magnetism due to energization of a magnet or a coil affects the position sensor, causing a detection error. Therefore, Patent Document 2 proposes a technique in which a guard yoke for suppressing magnetism is provided, and Patent Document 3 proposes a technique in which a permanent magnet is attached to the yoke and a position sensor is provided at a position orthogonal to the extending direction of the yoke. Further, Patent Document 4 proposes a technique of using a magnet constituting a drive device as a position sensor.

Japanese Unexamined Patent Publication No. 2011-75674 Japanese Unexamined Patent Publication No. 2011-237507 Japanese Unexamined Patent Publication No. 2013-37042 Japanese Unexamined Patent Publication No. 2011-13619

However, in Patent Document 2, the encoder magnet for position detection is required separately from the magnet constituting the drive device, and a guard yoke for shielding the magnetism is required. For this reason, the number of parts increases and an arrangement space is required, which hinders miniaturization. Further, in Patent Document 3, since the voice coil constituting the drive device and the position sensor are close to each other, the position sensor may erroneously detect due to the magnetism generated when the coil is energized. Further, in Patent Document 4, the stroke that can be driven is limited, and it is not suitable for driving a lens having a relatively large amount of movement, such as a focus lens.

Therefore, according to the present invention, it is possible to prevent erroneous detection of the position of the drive target with a simple structure without inviting an increase in the size of the optical device, and further, it is possible to secure a relatively large drive stroke of the drive target. It is an object of the present invention to provide a drive device.

In order to achieve the above object, the drive device according to the present invention is fixed to one of the movable portion, the base member that movably holds the movable portion in the first direction, and the base member and the movable portion. A magnet and a yoke fixed to the other of the base member and the movable portion and extending in the first direction, and a magnetic sensor for detecting the magnetic flux of the magnet. The yoke is the first. It has a pair of arms extending in the direction of the above, the magnet is arranged on the inner surface of one of the pair of arms, and the other arm is inserted into the hollow portion of the coil. The movable part is a drive device that can move relative to the base member by energization of the magnet, and the magnet has N poles and S poles magnetized in a second direction orthogonal to the first direction. The magnetic sensor faces the yoke in the second direction when the movable portion is moved to the first position in the first direction, and the movable portion is different from the first position. It is characterized in that it is provided at a position not facing the yoke when it is moved to the second position .

According to the present invention, it is possible to prevent erroneous detection of the position of the drive target with a simple structure without inviting an increase in size of the optical device, and further, it is possible to secure a relatively large drive stroke of the drive target. Drive devices can be provided.

It is a perspective view which shows the outline of the focus part of the lens barrel which concerns on 1st Embodiment of the optical apparatus which comprises the driving device of this invention. It is an exploded perspective view of the focus part shown in FIG. It is a schematic cross-sectional view when the focus part shown in FIG. 1 is seen from the left side. It is a graph which shows the change of the magnitude of the magnetic field detected by the magnetic sensor when the distance between a magnetic sensor and a magnet changes. It is an exploded perspective view of the focus part of the lens barrel which concerns on 2nd Embodiment of the optical apparatus which comprises the driving device of this invention. It is schematic cross-sectional view of the focus part when the lens holding frame moves to the upper end (one end) in the optical axis direction of a movable range. It is schematic cross-sectional view of the focus part when the lens holding frame moves to the lower end (the other end) of the movable range in the optical axis direction. It is a graph which shows the state of the magnetic field change detected by a magnetic sensor. FIG. 3 is an exploded perspective view of a focus portion of a lens barrel according to a third embodiment of an optical device including a driving device of the present invention. It is a schematic sectional drawing of a focus part. It is a graph which shows the state of the magnetic field change detected by a magnetic sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a perspective view showing an outline of a focus portion of a lens barrel according to a first embodiment of an optical device including a driving device of the present invention. FIG. 2 is an exploded perspective view of the focus portion shown in FIG. FIG. 3 is a schematic cross-sectional view of the focus portion shown in FIG. 1 when viewed from the left side.

As shown in FIGS. 1 to 3, a voice coil motor including a yoke 8, a magnet 7, and a coil 3 is mounted on the focus portion. The focus unit includes a focus lens 5 (hereinafter referred to as a lens 5) as one of the lens groups, and the lens 5 is held by the lens holding frame 6. The lens 5 corresponds to an example of the optical member of the present invention.

The lens holding frame 6 has a guide sleeve 6a, a steady rest portion 6b, and a yoke receiving portion 6c to which the yoke 8 is fixed, and the guide sleeve 6a and the steady rest portion 6b are a pair extending from the base member 1. It is held movably along the guide bar 2 in the optical axis direction. As a result, the focus operation can be performed. Further, the base member 1 holds an annular coil 3 and a magnetic sensor 4 such as a Hall element.

The magnet 7 is arranged in parallel with the guide bar 2 and has a length equal to or longer than the drive stroke in the optical axis direction of the lens 5. The north pole and the south pole are magnetized in the thickness direction orthogonal to the moving direction of the lens 5 of the magnet 7. The north pole and the south pole may be reversed.

The yoke 8 has a pair of arm portions 8a and 8b having substantially the same length extending in the moving direction of the lens 5, and is formed in a U shape by connecting the ends of the arm portions 8a and the arm portions 8b. There is. A magnet 7 is fixed to the inner surface of one arm portion 8a facing the other arm portion 8b. The lens holding frame 6 and the magnet 7 to which the yoke 8 is fixed are assembled to the base member 1 so that the arm portion 8b of the yoke 8 is inserted into the hollow portion of the coil 3 fixed to the base member 1.

When the coil 3 is energized in this state, the magnetic flux from the magnet 7 crosses the coil 3, so that a driving force is generated and the coil 3 moves relative to the magnet 7. In other words, since the coil 3 is fixed to the base member 1, the magnet 7 moves in the optical axis direction together with the lens holding frame 6 that holds the lens 5 to be driven.

Further, the magnetic sensor 4 is arranged at a position overlapping the magnet 7 when viewed from the optical axis direction of the lens 5, and detects the leakage flux of the magnet 7. When the magnet 7 moves in the optical axis direction with the energization of the coil 3, the distance between the magnet 7 and the magnetic sensor 4 changes, and the magnitude of the magnetism detected by the magnetic sensor 4 changes.

FIG. 4 is a graph showing a change in the magnitude of the magnetic field detected by the magnetic sensor 4 when the distance between the magnetic sensor 4 and the magnet 7 changes. As shown in FIG. 4, it can be seen that the magnetic field changes according to the distance from the magnet 7 to the magnetic sensor 4. Therefore, by detecting the magnetic field with the magnetic sensor 4, the position of the magnet 7, that is, the position of the lens 5 is detected. It becomes possible to do.

In the present embodiment, the magnet 7 is longer than the length of the arm portion 8a of the yoke 8, and the magnet 7 projects from the end of the arm portion 8a toward the magnetic sensor 4 by the length x. By doing so, the leakage flux from the magnet 7 can be effectively detected by the magnetic sensor 4. Even if the magnet 7 has the same length as or shorter than the yoke 8, it can be detected by the magnetic sensor 4, but the output of the voice coil motor is not sufficient or the detectable distance becomes short. Or something.

As described above, in the voice coil motor having the U-shaped yoke 8 that enables a sufficient drive stroke of the lens 5, the magnet 7 is projected from the yoke 8 toward the magnetic sensor 4. By arranging the magnetic sensor 4 so as to face the protruding surface of the magnet 7 from the yoke 8, the position of the lens 5 in the optical axis direction can be detected.

As described above, in the present embodiment, it is possible to prevent erroneous detection of the position of the lens 5 to be driven by a simple structure without inviting an increase in size of the camera, and further, the lens 5 is relatively large. The drive stroke can be secured.

Further, in the present embodiment, a so-called moving magnet method is adopted in which the magnet 7 and the yoke 8 are held in the lens holding frame 6 which is a movable portion, and the coil 3 is held in the base member 1 on the fixed side. Therefore, it is not necessary for the lens holding frame 6 to have a flexible substrate for energizing the coil 3, and the focus portion can be configured with a simpler structure.

(Second embodiment)
Next, with reference to FIGS. 5 to 8, the focus portion of the lens barrel according to the second embodiment of the optical device provided with the driving device of the present invention will be described. FIG. 5 is an exploded perspective view of the focus portion. FIG. 6 is a schematic cross-sectional view of the focus portion when the lens holding frame 6 moves to the upper end (one end) in the optical axis direction of the movable range. FIG. 7 is a schematic cross-sectional view of the focus portion when the lens holding frame 6 moves to the lower end (the other end) of the movable range in the optical axis direction. In addition, in this embodiment, the same reference numerals are given to the respective figures with respect to the parts overlapping or corresponding to the first embodiment, and only the differences will be mainly described.

As shown in FIGS. 6 and 7, in the present embodiment, the magnetic sensor 4 is provided so as to sandwich the arm portion 8a of the yoke 8 with the magnet 7, and the magnetized surface of the magnet 7 (in the present embodiment, It is arranged opposite to the N pole). Further, the magnetic sensor 4 faces only the protruding portion of the magnet 7 from the yoke 8 in FIG. 6, and faces the magnet 7 and the yoke 8 in FIG. 7. That is, the magnetic sensor 4 may or may not face the yoke 8 depending on the position of the lens holding frame 6 in the optical axis direction.

FIG. 8A is a graph showing the state of the magnetic field change detected by the magnetic sensor 4. The horizontal axis is the relative position of the lens holding frame 6 with respect to the magnetic sensor 4 in the optical axis direction, and the vertical axis is the magnetic sensor 4. The magnitude of the detected magnetic field. FIG. 8B is a diagram showing a magnet 7 and a yoke 8 of the lens holding frame 6.

As is clear from FIG. 8, the magnetic flux density begins to change from the position where the magnetic sensor 4 and the magnet 7 face each other, and continues to change downward to the right. After that, the magnetic flux changes to the vicinity of the substantially central portion of the length of the magnet 7, and then the magnetic flux begins to converge. Therefore, the position of the lens 5 in the optical axis direction can be detected based on the detection value of the magnetic sensor 4 detected in the region where the magnetic flux changes downward to the right.

Further, since the magnetic sensor 4 is arranged to face the surface of the magnet 7 facing the opposite side to the coil 3, it is difficult for the magnetic sensor 4 to detect the magnetic flux generated when the coil 3 is energized. That is, since the magnetic sensor 4 is arranged on the back surface side of the arm portion 8a of the yoke 8 when viewed from the coil 3, the arm portion 8a functions as a shield member that shields the magnetism from the coil 3. Other configurations and effects are the same as those in the first embodiment.

(Third embodiment)
With reference to FIGS. 9 to 11, the focus portion of the lens barrel according to the third embodiment of the optical device provided with the driving device of the present invention will be described. FIG. 9 is an exploded perspective view of the focus portion. FIG. 10 is a schematic cross-sectional view of the focus portion. In the present embodiment, the parts that overlap or correspond to the first and second embodiments are designated by the same reference numerals, and the differences will be mainly described.

In the present embodiment, the lower end of the magnet 7 is substantially the same as the lower ends of the arms 8a and 8b, which are the ends on the open side of the yoke 8, as compared with the second embodiment, and the arms 8a and 8b are substantially the same. The difference is that the lower ends of the magnets are connected to each other by a flat plate-shaped second yoke 9.

FIG. 11A is a graph showing the state of the magnetic field change detected by the magnetic sensor 4. The horizontal axis is the relative position of the lens holding frame 6 with respect to the magnetic sensor 4 in the optical axis direction, and the vertical axis is the magnetic sensor 4. The magnitude of the magnetic field detected in. FIG. 11B is a diagram showing a magnet 7 and a yoke 8 of the lens holding frame 6. In the present embodiment, the magnetic sensor 4 is always opposed to the magnet 7 and the yoke 8 regardless of the position of the lens holding frame 6 in the optical axis direction.

As is clear from FIG. 11, in the magnetic sensor 4, the magnetic flux does not change immediately at the position facing the second yoke 9, and the magnetic flux changes from the point where the lower end of the magnet 7 passes by to the right. Therefore, the position of the lens 5 in the optical axis direction can be detected based on the detection value of the magnetic sensor 4 detected in the region where the magnetic flux changes downward to the right.

Further, in the present embodiment, the absolute value of the magnetic flux itself is smaller than that of the change in the magnetic flux in the second embodiment (FIG. 8 (a)) (indicated by the broken line in FIG. 11 (a)), and the magnetic flux has a smaller value. The range of change is narrow. Therefore, in the present embodiment, the range in which the position of the lens 5 can be detected is smaller than that in the second embodiment, but the magnet 7 is surrounded by the yoke 8 and the second yoke 9, so that the magnetic circuit is formed. It is effectively formed and the output as a motor is high. Other configurations and effects are the same as those in the first and second embodiments.

The configuration of the present invention is not limited to those exemplified in each of the above embodiments, and the material, shape, dimensions, form, number, arrangement location, etc. are appropriately changed as long as the gist of the present invention is not deviated. It is possible.

For example, in each of the above embodiments, a so-called moving magnet method is adopted in which the magnet 7 and the yoke 8 are held on the movable portion side and the coil 3 is held on the fixed portion side, but the coil 3 is held on the movable portion side. However, the magnet 7 and the yoke 8 may be held on the fixed portion side. In this case, the magnetic sensor 4 is provided on the movable portion side.

1 Base member 2 Guide bar 3 Coil 4 Magnetic sensor 5 Lens 6 Lens holding frame 7 Magnet 8 York 8a, 8b Arm

Claims (7)

Moving parts and
A base member that movably holds the movable portion in the first direction, and
A coil fixed to one of the base member and the movable portion,
A magnet and a yoke fixed to the other of the base member and the movable portion and extending in the first direction.
A magnetic sensor for detecting the magnetic flux of the magnet is provided.
The yoke has a pair of arms extending in the first direction, the magnet is arranged on the inner surface of one arm of the pair of arms, and the other arm is inserted into the hollow portion of the coil. Has been
A drive device in which the movable portion can move relative to the base member by energizing the coil.
In the magnet, the north pole and the south pole are magnetized in the second direction orthogonal to the first direction, and the magnet is magnetized.
The magnetic sensor faces the yoke in a state where the movable portion is moved to the first position in the first direction in the second direction, and the movable portion is different from the first position. A drive device characterized in that it is provided at a position not facing the yoke when it is moved to the position of . The driving device according to claim 1 , wherein the magnetic sensor is provided so as to sandwich the one arm portion of the yoke between the magnet and the magnetic sensor in the second direction . The magnet projects from the yoke in the first direction.
The claim is characterized in that the magnetic sensor is provided at a position facing a portion of the magnet protruding from the yoke in a state where the movable portion is moved to the second position in the second direction. Item 2. The driving device according to Item 1 or 2. The first position is a position that is one end of the movable range of the movable portion.
The drive device according to any one of claims 1 to 3, wherein the second position is a position that is the other end of the movable range of the movable portion. The driving device according to any one of claims 1 to 4, wherein the second direction is a direction in which the pair of arms of the yoke face each other. An optical device comprising the drive device according to any one of claims 1 to 5. A lens barrel comprising the driving device according to any one of claims 1 to 5.

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