JP6253501B2 - Linear actuator - Google Patents

Description

  The present invention relates to a linear actuator that reciprocates along a straight path using a voice coil motor.

  Linear actuators that use a voice coil motor to move a lens or the like with good responsiveness and perform focusing are widely used. In such a magnetic drive type linear actuator, the movable element is supported in a linearly movable state by a linear guide or the like, and a load attaching portion for attaching a lens to be driven is fixed to the movable element.

  In general, a magnetically driven linear actuator is required to linearly move a minute range with a load such as a lens with high responsiveness and high positioning accuracy. In the patent document 1, the present inventors have proposed a magnetically driven linear actuator for the purpose of improving positioning accuracy and durability.

  In this linear actuator, a load mounting portion, a linear guide, and a sensor portion for detecting the position of the mover are arranged inside a mover having a configuration in which a drive coil is wound around a rectangular cylindrical coil frame. The support center of the linear guide is made to coincide. In addition, a pair of permanent magnets on the stator side is arranged on both sides of the rectangular cylindrical mover so as to be symmetrical, and the generation center of magnetic force (thrust) acting on the mover coincides with the center of gravity of the mover I try to let them. As a result, the moment applied to the linear guide portion can be reduced, and the mover can be positioned with high responsiveness and high positioning accuracy. Further, since the moment acting on the linear guide supporting the mover is reduced, the durability of the linear actuator can be improved.

JP 2008-35645 A

  Here, when there is a restriction on the installation space of the linear actuator, the size reduction is required. In order to reduce the size of the linear actuator configured as described above, it is an effective measure to reduce the size of the rectangular cylindrical movable element incorporated therein.

  However, if the mover is made smaller, the sides on both sides of the drive coil wound around the rectangular cylindrical coil frame that face the permanent magnet are also shortened, the thrust generation area is reduced, and the thrust constant is reduced. End up. Increasing the electrical load (number of turns, current value) to compensate for the decrease in the thrust constant is not preferable because the heat generation characteristics are deteriorated.

  On the other hand, in the linear actuator having the above configuration, when mechanical deformation occurs in the rectangular cylindrical mover, the load mounting portion on which the lens or the like is mounted may not be positioned with high responsiveness and high accuracy. In order to prevent the deformation of the mover, it is necessary to take measures such as increasing the thickness of the coil frame. However, this increases the weight of the mover significantly. An increase in the weight of the mover is undesirable because it causes a decrease in responsiveness.

In view of the above, an object of the present invention is to provide a linear actuator capable of reducing the size of a mover without causing a reduction in thrust and a deterioration in heat generation characteristics. Moreover, the subject of this invention is providing the linear actuator which can suppress a deformation | transformation of a needle | mover and can improve responsiveness with size reduction of a needle | mover.

In order to solve the above problems, the linear actuator of the present invention is
A cylindrical mover provided with a drive coil wound around a cylindrical coil frame;
A stator provided with a permanent magnet that surrounds the outer periphery of the mover from first to third directions which are three directions among the four directions around the central axis of the mover;
A load attaching portion attached to the mover and projecting outward from the mover toward a fourth direction which is the remaining one of the four directions ;
A linear bearing that guides the mover along a straight path parallel to a central axis thereof;
A position detection unit for detecting the position of the load mounting unit on the linear path;
Have
The linear motion bearing includes a fixed-side bearing member attached to the stator, and a movable-side bearing member supporting the movable element,
The fixed-side bearing member extends through the inner side of the mover in the direction along the central axis,
The movable side bearing member is slidably supported along the linear path by the fixed side bearing member inside the movable element,
The coil frame is attached to the movable side bearing member via a bearing fixing member,
The bearing fixing member is a member that is positioned inside the mover and is longer in the front-rear direction along the central axis than the mover,
When the frame portion of the coil frame defining the portion facing the fourth direction in the mover is a lower frame portion, the bearing is fixed to the upper surface of the lower frame portion facing the inner side of the mover. The member is fixed,
The load mounting portion includes a front plate portion and a back plate portion that protrude in the fourth direction with respect to the lower frame portion from front and rear end portions in the front-rear direction along the central axis of the bearing fixing member. And
Wherein the position detector includes a movable-side detecting section that is attached to the load attachment portion, and the for the movable-side detecting section so as to face from the fourth direction, the fixed-side detecting section attached to a portion of said stator It is characterized by having.

  In the linear actuator of the present invention, the load attaching portion and the position detecting portion are arranged outside the cylindrical mover, and only the linear motion bearing is arranged inside the mover. Therefore, the mover can be made small. Moreover, the permanent magnet is arrange | positioned in the state which surrounds a needle | mover from three directions. Therefore, even if the cylindrical mover is made smaller, it is possible to secure the same thrust generation area as when a pair of permanent magnets are arranged on both sides of the cylindrical mover, and to prevent a reduction in thrust constant. Therefore, the mover can be made small without deteriorating the heat generation characteristics associated with an increase in electrical loading to compensate for the decrease in thrust constant. As a result, the linear actuator can be reduced in size without a reduction in thrust or deterioration in heat generation characteristics.

  Moreover, in the linear actuator of this invention, the position of the load attachment part located in the outer side of a needle | mover is detected by the movable side detection part directly attached to the said load attachment part. If the load mounting portion mounted on the mover and the movable side detection unit are separated in a direction orthogonal to the moving direction of the mover, the position detection unit detects that the mover is deformed. There is a difference between the position and the actual position of the load mounting portion, and there is a possibility that the position control of the load member mounted on the load mounting portion cannot be performed with high accuracy. In the present invention, since the position of the load mounting portion is directly detected, the position control error due to the deformation of the mover can be suppressed or prevented, and the load member can be accurately positioned.

  Here, when the first, second, and third permanent magnets are arranged at an angular interval of 90 degrees in this order as the permanent magnet, the first, third, The permanent magnet faces and sandwiches the mover, the load mounting portion protrudes in a direction away from the second permanent magnet, and the mover has a width in the direction of the first and third permanent magnets orthogonal to this. It is desirable that the cylindrical shape is wider than the width in the direction.

  If it does in this way, the movable side bearing member which supports the needle | mover can be made to approach the center of the thrust which acts on a needle | mover. That is, since the cylindrical mover is surrounded by the first to third permanent magnets from three directions, the center of the thrust is a position offset toward the second permanent magnet with respect to the center of the mover. By narrowing the width of the mover in the direction perpendicular to the direction of the first and third permanent magnets, the distance between the movable bearing member and the thrust center that are separated in this direction can be shortened. As a result, the moment acting on the movable-side bearing member due to the thrust can be reduced, the moving load of the mover can be reduced, and the responsiveness of the position control of the mover can be improved.

It is an external appearance perspective view which shows the linear actuator to which this invention is applied, and is a thing at the time of seeing from the front upper side. It is the front view and bottom view of the linear actuator of FIG. FIG. 2 is a transverse sectional view, a longitudinal sectional view, and a bottom view of the linear actuator of FIG. 1.

  Hereinafter, an embodiment of a magnetic drive type linear actuator to which the present invention is applied will be described with reference to the drawings.

  FIG. 1 is an external perspective view showing the linear actuator according to the present embodiment, as viewed from the front upper side. 2A and 2B are a front view and a bottom view of the linear actuator. In the following, for convenience of explanation, the direction of the arrow X is the width direction, the direction of the arrow Y perpendicular to the direction is the front-rear direction, and the direction of the arrow Z perpendicular to the arrows X, Y is the up-down direction.

  The linear actuator 1 has a voice coil motor including a stator 2 and a mover 3. Further, a load attachment portion, in this example, a lens holder 4 is attached to the mover 3. The mover 3 is slidably supported by a linear motion bearing 5. The linear motion bearing 5 allows the mover to reciprocate along a straight path parallel to the central axis 3 a extending in the front-rear direction Y. The moving position of the mover 3 is detected by the position detector 6. The linear actuator 1 has a substantially bilaterally symmetric structure around a plane P extending in the vertical direction including the central axis 3a, except for the position detector 6.

  3A is a schematic cross-sectional view of the linear actuator 1 when cut along the line IIIa-IIIa in FIG. 1, and FIG. 3B is a linear actuator 1 when cut along the line IIIb-IIIb in FIG. FIG. 3C is a bottom view of the linear actuator. In these drawings, the position detector 6 is omitted.

  Referring mainly to FIG. 3, the stator 2 has a gate-shaped outer yoke 8 that opens downward, three flat rectangular parallelepiped permanent magnets 9L, 9U, and 9R, and a downward opening. A gate-shaped inner yoke 10 is provided. The outer yoke 8 has a fixed length extending in the front-rear direction Y. The top plate portion 8U having a fixed thickness and the left and right sides extending downward in the vertical direction Z perpendicularly from both ends in the width direction X of the top plate portion 8U. Side plate portions 8L and 8R are provided.

  As can be seen from FIG. 3B, projecting portions 8a and 8b projecting downward are formed at the front and rear end portions of the top plate portion 8U, and a recess 8c extending in the front-rear direction is formed therebetween. Yes. A rectangular plate-shaped permanent magnet 9U is attached in the recess 8c. As can be seen from FIG. 3C, the left and right side plate portions 8L and 8R are also formed with protrusions 8d and 8e that protrude perpendicularly inwardly. The recess 8f extends to the bottom and has a certain depth. Rectangular plate-shaped left and right permanent magnets 9L and 9R are attached to the respective recesses 8f.

  The inner yoke 10 is disposed inside the outer yoke 8 and has the same length in the front-rear direction Y as the outer yoke 8. The inner yoke 10 includes a top plate portion 10U and left and right side plate portions 10L and 10R extending downward in the vertical direction Z at right angles from both ends in the width direction X. The top plate portion 10U faces the permanent magnet 9U at regular intervals, and both end portions in the front-rear direction Y are attached to the front and rear protrusions 8a, 8b of the top plate portion 8U of the outer yoke 8. Similarly, the left and right side plate portions 10L and 10R face the left and right permanent magnets 9L and 9R at a constant interval, and both front and rear ends thereof are protrusions 8d before and after the left and right side plate portions 8L and 8R of the outer yoke 8. , 8e.

  Between the three permanent magnets 9U, 9L, and 9R attached to the gate-shaped outer yoke 8 and the gate-shaped inner yoke 10 disposed on the inner side, the gate shape having a predetermined width extending in the front-rear direction Y. The gap is formed. A flat rectangular cylindrical movable element 3 is disposed in the gap.

  The mover 3 includes a rectangular cylindrical coil frame 11 and a drive coil 12 wound in the circumferential direction along the outer peripheral surface. The coil frame 11 has a flat rectangular tube shape in which the dimension in the vertical direction Z is smaller than the dimension in the width direction X. The left first surface of the mover 3 faces the permanent magnet 9L at a constant interval, the upper second surface faces the permanent magnet 9U at a constant interval, and the right third surface is fixed to the permanent magnet 9R. They are facing each other at intervals. In other words, the mover 3 is surrounded by the permanent magnets 9L, 9U, and 9R from the outer three sides (left, upper, and right) at an angular interval of 90 degrees around the central axis 3a.

  Next, a linear motion bearing 5 for guiding the mover 3 is arranged inside the rectangular cylindrical mover 3. The linear motion bearing 5 includes a guide rail 5a that is a fixed-side bearing member attached to the lower surface of the top plate portion 10U of the inner yoke 10, and a slider 5b that is a movable-side bearing member that supports the mover 3. The slider 5b is slidable along the guide rail 5a.

  The guide rail 5 a is disposed in a state of passing through the inner side of the mover 3 in the front-rear direction Y in a direction parallel to the central axis 3 a of the mover 3 at the center in the width direction X of the stator 2. A coil frame 11 is attached to a slider 5b slidably attached to the guide rail 5a from below via a bearing fixing member 13 fixed to the lower surface thereof.

  The bearing fixing member 13 is fixed to the upper surface of the lower frame portion 11B of the coil frame 11 that defines the portion of the fourth surface facing the lower side of the mover 3. The bearing fixing member 13 is a rectangular plate-like member that is positioned inside the mover 3 and is longer in the front-rear direction than the mover 3.

  A lens holder 4 as a load attachment portion is attached to the bearing fixing member 13. In this example, the bearing fixing member 13 and the lens holder 4 are formed from a single component. That is, the lens holder 4 includes a front plate portion 4a and a back plate portion 4b that protrude downward at right angles from the front and rear ends of the bearing fixing member 13. A portion of the fourth surface of the mover 3 is located between these.

  A circular opening 4c for attaching a lens (not shown) as a load member is formed in the front plate portion 4a. In the back plate portion 4b, a circular opening 4d is formed coaxially with the circular opening 4c for allowing light passing through the lens to pass therethrough.

Next, with reference to FIG. 2, the position detection unit 6 that detects the movement position of the mover 3 on the straight path is an optical position detection unit, and is attached to the mover 3 side. The light-emitting part 6a which is a detection part, and the light-receiving part 6b which is a stationary-side detection part attached to the stator 2 side are provided. The light emitting unit 6 a is attached to the left side surface of the lens holder 4. In this example,
It is attached so as to be bridged between the side surfaces of the front plate portion 4a and the back plate portion 4b.

  Detection light emitted from a light emitting element such as an LED of the light emitting portion 6a is directed to the light receiving portion 6b attached to the inner side surface of the left side plate portion 8L of the outer yoke 8. The light receiving unit 6b includes a detecting element such as a one-dimensional semiconductor position detecting element whose light receiving surface extends in the front-rear direction Y, and outputs a position detection signal corresponding to the light receiving position.

  In the linear actuator 1 configured as described above, the three permanent magnets 9L, 9U, and 9R are arranged in a state of surrounding the flat cylindrical movable element 3 from three directions around the central axis 3a. Since the mover 3 has a flat cylindrical shape with a small height dimension (dimension in the vertical direction Z), the left and right first and third surfaces are short and the permanent magnets 9L and 9R facing each other The thrust generation area between is narrow. However, since the permanent magnet 9U faces the second upper surface from above, it is possible to avoid a reduction in thrust generation area due to the flattening of the mover 3. Therefore, the size of the mover 3 in the vertical direction can be reduced without causing deterioration of the heat generation characteristics due to a decrease in thrust or an increase in electrical loading to compensate for this. Therefore, it is possible to reduce the size of the linear actuator 1, particularly to reduce the vertical dimension.

  Further, by arranging the permanent magnet 9 </ b> U on the upper side, the center of the thrust acting on the mover 3 is shifted upward with respect to the center of the mover 3. As a result, the thrust center moves away from the support center of the mover 3 by the linear motion bearing. However, in this example, the mover 3 has a cylindrical shape with a flat vertical direction Z. In the vertical direction Z, the support center of the mover 3 by the linear motion bearing can be brought close to the thrust center, and the distance between them can be reduced. Therefore, the moment acting on the portion of the support center of the linear motion bearing and the bearing fixing member 13 can be suppressed by the thrust. As a result, the moving load of the mover 3 can be reduced, and the responsiveness of the positioning control can be improved.

  Further, since the movable element 3 has a flat cylindrical shape in the vertical direction Z, the vertical rigidity of the central axis 3a of the movable element 3 can be increased. Thereby, a deformation | transformation of the needle | mover 3 can be suppressed and the responsiveness at the time of high acceleration movement etc. can be improved.

  Further, the position detection unit 6 includes a light emitting unit 6a attached to the lens holder 4 on which a lens as a load member is mounted, and directly detects the position of the lens holder 4. When the movable side detection unit such as the light emitting unit is attached to a part different from the load attachment part such as the lens holder in the movable element 3, the actual position of the load attachment part is caused by the deformation of the movable element 3. And a position detected by the position detection unit may occur. In this example, since a decrease in detection accuracy due to such deformation of the mover 3 can be suppressed or avoided, positioning control of the load member mounted on the mover can be performed with high accuracy.

  The mover 3 has a flat rectangular tube shape. The cylinder shape of the mover 3 is not limited to a rectangle, and may be an oval or an ellipse that is long in the width direction X, for example. In the above case, as the permanent magnets, three permanent magnets are arranged so as to surround the three surfaces of the mover 3 at an angular interval of 90 degrees around the central axis 3a. Permanent magnets can also be arranged in a state of being surrounded from three directions at angles other than 90 degrees, for example, 60 degree intervals. Moreover, it is also possible to use the single permanent magnet of the cross-sectional shape surrounding three surfaces as a permanent magnet.

1 Linear Actuator 2 Stator 3 Movable Element 3a Center Axis 4 Lens Holder (Load Mounting Section)
4a Front plate portion 4b Back plate portion 4c, 4d Circular opening 5 Linear motion bearing 5a Guide rail (fixed side bearing member)
5b Slider (movable side bearing member)
6 Position detector 6a Light emitter (movable side detector)
6b Light receiver (fixed side detector)
8 Outer yoke 8a, 8b Protruding portion 8c Concavity 8d, 8e Protruding portion 8f Concavity 8L, 8R Side plate portion 8U Top plate portion 9L, 9U, 9R Permanent magnet 10 Inner yoke 10L, 10R Side plate portion 10U Top plate portion 11 Coil frame 11B Bottom Side frame portion 12 Drive coil 13 Bearing fixing member P Plane

Claims (5)

A cylindrical mover provided with a drive coil wound around a cylindrical coil frame;
A stator provided with a permanent magnet that surrounds the outer periphery of the mover from first to third directions which are three directions among the four directions around the central axis of the mover;
A load attaching portion attached to the mover and projecting outward from the mover toward a fourth direction which is the remaining one of the four directions ;
A linear bearing that guides the mover along a straight path parallel to a central axis thereof;
A position detection unit for detecting the position of the load mounting unit on the linear path;
Have
The linear motion bearing includes a fixed-side bearing member attached to the stator, and a movable-side bearing member supporting the movable element,
The fixed-side bearing member extends through the inner side of the mover in the direction along the central axis,
The movable side bearing member is slidably supported along the linear path by the fixed side bearing member inside the movable element,
The coil frame is attached to the movable side bearing member via a bearing fixing member,
The bearing fixing member is a member that is positioned inside the mover and is longer in the front-rear direction along the central axis than the mover,
When the frame portion of the coil frame defining the portion facing the fourth direction in the mover is a lower frame portion, the bearing is fixed to the upper surface of the lower frame portion facing the inner side of the mover. The member is fixed,
The load mounting portion includes a front plate portion and a back plate portion that protrude in the fourth direction with respect to the lower frame portion from front and rear end portions in the front-rear direction along the central axis of the bearing fixing member. And
Wherein the position detector includes a movable-side detecting section that is attached to the load attachment portion, and the for the movable-side detecting section so as to face from the fourth direction, the fixed-side detecting section attached to a portion of said stator A linear actuator comprising: The permanent magnet includes first, second and third permanent magnets arranged at an angular interval of 90 degrees around the central axis,
The first and third permanent magnets face each other with the mover interposed therebetween,
The load mounting portion protrudes in a direction away from the second permanent magnet;
2. The linear actuator according to claim 1, wherein the movable element has a flat cylindrical shape in which a width in a direction of the first and third permanent magnets is wider than a width in a direction orthogonal to the first and third permanent magnets. The mover has a rectangular cylindrical shape with first to fourth surfaces,
The four directions are directions orthogonal to the first to fourth surfaces,
The first, second and third permanent magnets are opposed to the first, second and third surfaces;
The linear actuator according to claim 2, wherein the load attachment portion is attached to the lower frame portion that defines the fourth surface and protrudes in a direction orthogonal to the fourth surface.   The linear actuator according to claim 3, wherein the mover has a flat rectangular cylindrical shape in which a distance between the second surface and the fourth surface is narrower than a distance between the first surface and the third surface.   The stator, the mover, the linear motion bearing, and the load mounting portion include the central axis, and have a symmetrical shape with respect to a plane orthogonal to the second surface and the fourth surface. The linear actuator according to claim 4.

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