JP2007028833A - Linear motor and lens drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motor producing a big drive output with small size by enhancing utilization efficiency of a coil. <P>SOLUTION: The linear motor 7 comprises a yoke 17, a magnet 19, and a coil 23 wherein the yoke 17 is subjected to linear driving relatively to the coil 23 with an electromagnetic force produced by conducting the coil 23. The yoke 17 has one sidewall portion 25a and the other sidewall portion 25b provided substantially in parallel along the relative moving direction of the coil 23, and an intermediate wall portion 25c provided between the one sidewall portion 25a and the other sidewall portion 25b. A magnet 19 is provided on the side face of each intermediate wall portion for the one sidewall portion 25a and the other sidewall portion 25b wherein each magnet 19 is arranged to direct the magnetic pole toward the intermediate wall portion 25c side. The coil 23 is formed annularly and arranged between the one sidewall portion 25a and the other sidewall portion 25b while inserting the inner circumferential side of the annular coil into the intermediate wall portion 25c. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a linear motor in which a coil moves relative to a yoke on a straight line, and a lens driving device that drives a lens in the optical axis direction using the linear motor.

  In Patent Document 1, in a yoke provided with one side wall portion and the other side wall portion provided substantially in parallel, a magnet is disposed on one side wall portion, and a coil body wound in an annular shape is inserted into the other side wall portion, A linear motor is disclosed in which a coil is linearly driven relative to a yoke by energizing the coil.

JP 2004-280031 A

  However, the conventional linear motor uses a coil wound with a coil wire, but only one side facing the magnet contributes to obtaining thrust, and the other part is substantially Therefore, the use efficiency of the coil is inferior, and there is a limit in obtaining a predetermined thrust.

  On the other hand, when the magnet is enlarged or the volume of the coil is increased, there is a problem that the entire motor becomes large or the relative moving distance of the coil is limited. In particular, in a linear motor mounted on a small camera or the like, a predetermined drive output (high thrust) and a drive distance are required along with downsizing of the entire motor.

  Accordingly, an object of the present invention is to provide a linear motor capable of obtaining a large driving output while being small in size by increasing the utilization efficiency of the coil, and a lens driving device using the linear motor.

  The invention described in claim 1 is a linear motor that includes a yoke, a magnet, and a coil, and the coil is linearly driven relative to the yoke by electromagnetic force generated by energizing the coil. One side wall portion and the other side wall portion provided substantially parallel to each other along the relative movement direction, and an intermediate wall portion provided between the one side wall portion and the other side wall portion. Has a magnet on the side of each intermediate wall, each magnet is arranged with the same magnetic pole facing the intermediate wall, the coil is annular, and the inner periphery of the ring is inserted through the intermediate wall It arrange | positions between one side wall part and the other side wall part, It is characterized by the above-mentioned.

  According to a second aspect of the present invention, in the first aspect of the present invention, the yoke has a closing wall on each of one end side and the other end side in the relative movement direction of the coil, and the closing wall has one side wall portion and The field formed by each wall part of the other side wall part and the intermediate wall part is closed.

  The invention according to claim 3 is the invention according to claim 1, wherein the yoke is provided with two yoke components having a substantially U-shaped cross section, and the U-shaped openings of the yoke components are arranged adjacent to each other. And the intermediate wall portion is formed by joining adjacent wall portions of the yoke constituent member.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the coil is formed by winding a plurality of coil wires, and each coil wire is parallel to the DC power source. It is characterized by being connected to.

  A fifth aspect of the invention includes the linear motor according to any one of the first to fourth aspects, wherein a lens holder of a small camera is attached to the coil, and the coil extends along the optical axis direction of the lens. It is a lens drive device characterized by moving.

  According to the first aspect of the present invention, the first magnetic field is formed between the one side wall portion and the intermediate wall portion constituting the yoke, and the second magnetic field is formed between the other side wall portion and the intermediate wall portion. At the same time, the directions of the magnetic fields are in opposite directions in each magnetic field. In addition, in the coil wound in an annular shape around the intermediate wall portion, reverse current flows in the first magnetic field and the second magnetic field. Therefore, according to Fleming's left-hand rule, thrust in the same direction acts on the coil in the first magnetic field and the second magnetic field, respectively, so that the efficiency of use of the coil can be increased, and the thrust acting on the two magnetic fields is added up. Therefore, a small and high thrust linear motor can be obtained.

  The yoke is provided with one side wall and the other side wall that extend along the relative driving direction of the coil, and an intermediate wall portion located between them, and a magnet is provided on each opposing surface side of the one side wall portion and the other side wall portion. Therefore, the configuration is simple and the manufacture is easy.

  According to the second aspect of the present invention, the effect of the first aspect can be obtained, and the magnetic field space is closed and the magnetic path is closed, so that the magnetic flux density can be increased and the thrust is further increased. Can be obtained.

  According to the invention described in claim 3, since the function and effect described in claim 1 can be obtained, and the yoke only joins a yoke constituent member having a general U-shaped cross section. It is easy to manufacture and can be manufactured using existing parts.

  According to the invention described in claim 4, the same effect as described in any one of claims 1 to 3 is achieved, and generally, the same current flows through the plurality of coil wires. The thrust F acting by applying a current to the coil wire is generally F = BLI. Since B is the magnetic field strength, L is the length of the coil wire, and I is the current passed through the coil wire, a large thrust can be obtained by increasing the length of the coil wire (increasing the number of turns). However, when the length L of one coil wire is increased or the number of turns is increased, the resistance of the coil wire is increased, the current value I flowing through the coil wire is decreased, and sufficient thrust cannot be obtained.

  In the present invention, even if the length and volume of the coil wire used in the entire coil are the same, the length of one coil wire is shortened, so that the resistance to current can be reduced for one coil wire. In addition, since the plurality of coil wires are connected in parallel to the DC power supply, an extremely large thrust (thrust close to a multiple of the number of coil wires) can be obtained as compared with the case where the coil is constituted by a single coil wire. It can be obtained.

  According to the invention described in claim 5, the effects described in any one of claims 1 to 3 are achieved, and in the lens holder of the small camera, the weight and friction of the lens and the holder act. Even in such a case, it is possible to drive with high responsiveness with a simple and compact configuration.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1A and 1B are diagrams for explaining the configuration of a linear motor according to the present embodiment. FIG. 1A is a transverse sectional view, and FIG. 1B is a longitudinal sectional view. 2 is a longitudinal sectional view of a small camera using the linear motor according to the present embodiment, FIG. 3 is a sectional view taken along line AA of the small camera shown in FIG. 2, and FIG. 4 explains the configuration of the coil. It is a figure, (a) is a front view, (b) is a perspective view.

  A lens driving device 1 according to the present embodiment is a lens driving device for an autofocus camera with an optical zoom incorporated in a mobile phone.

  As shown in FIG. 2, the lens driving device 1 includes a first lens holder 3 and a second lens holder 5 that are driven by electromagnetic force, a first driving mechanism (linear motor) 7 that drives the first lens holder 3, and And a second drive mechanism (linear motor) 9 for driving the second lens holder 5.

  The first lens holder 3 holds the optical zoom lens 15 in the present embodiment, and is provided so as to be slidable in the optical axis direction by the guide shaft 13.

  The second lens holder 5 holds a focusing lens 16, and is provided so as to be slidable in the optical axis direction by the guide shaft 13 in the same manner as the first lens holder 3. The zoom lens and the focus lens have the same optical axis.

  Since the first drive mechanism 7 and the second drive mechanism 9 have substantially the same configuration, the first drive mechanism 7 will be described, and the same reference numerals are given to the parts that exert the same effect on the second drive mechanism 9. Therefore, the description of the part is omitted.

  The first drive mechanism 7 is a linear motor, and includes a yoke 17, a magnet 19, and a coil body (coil) 23. In the present embodiment, the yoke 17 is fixed to the housing 11, the lens holder 3 is attached to the coil body 23, and the coil body 23 moves with respect to the yoke 17 in the optical axis direction.

  The yoke 17 has a substantially rectangular cross section and closes the magnetic field, and is provided between the one side wall portion 25a and the other side wall portion 25b which are long in the moving direction of the coil body 23, and between the one side wall portion 25a and the other side wall portion 25b. An intermediate wall portion 25c is provided, and the wall portions 25a, 25b, and 25c are provided substantially in parallel. On the other hand, the magnet 19 is stuck on the surface of the side wall 25a facing the intermediate wall 25c, and the magnet 19 is stuck on the surface of the other side wall 25b facing the intermediate wall 25.

  As shown in FIG. 1A, each of the magnets 19 has an N pole on the side of the intermediate wall 25c and an S pole on the opposite side, and the first in the N → S direction from the intermediate wall 25c toward the one side wall 25a. A magnetic field B is formed, and similarly, a second magnetic field B in the N → S direction is formed from the intermediate wall portion 25c toward the other side wall portion 25b. That is, in the present embodiment, two magnetic fields B having the same strength and opposite directions are formed on one side wall portion 25a side and the other side wall portion 25b side.

  As shown in FIGS. 1A and 1B, the coil body 23 is formed in a substantially rectangular tube shape, and an intermediate wall portion 25c is inserted through the inner peripheral side of the tube. In the present embodiment, the coil body 23 is formed by winding two coil wires 27a and 27b, respectively.

  As shown in FIG. 4, the two coil wires 27a and 27b are wound from one end 23a to the other end 23b in the driving direction of the coil body 23 (see FIG. 4B). Then, as shown in FIG. 4A by extracting with a one-dot chain line, the two coil wires 27a and 27b are bundled by bundling the two coil wires 27a and 27b at the winding start end and the winding end end. It is manufactured by winding at the same time in the state.

  A direct current is supplied to each of the coil wires 27 a and 27 b and is connected in parallel to the direct current power supply 31.

  Next, operations and effects of the lens driving device 1 according to the present invention will be described.

  When shooting with a camera (mobile phone) equipped with the lens driving device 1, when using an optical zoom, the first driving mechanism 7 is driven by passing an electric current through the coil body 23. For example, driving is performed in one direction from the position indicated by the solid line in FIG. 2 to the position indicated by the two-dot chain line. In addition, by flowing a current in the reverse direction, driving is performed in the other direction from the position indicated by the two-dot chain line to the position indicated by the solid line.

  The first lens holder 3 is held at a predetermined position by the frictional force with the guide shaft 13.

  In the first drive mechanism (linear motor) 7, a first magnetic field B is formed between the one side wall 25a and the intermediate wall 25c of the yoke 17, and between the other side wall 25b and the intermediate wall 25c. A second magnetic field B is formed. In the first magnetic field B and the second magnetic field B, the directions of the magnetic fields are opposite to each other (see FIG. 1A).

  On the other hand, since the coil body 23 inserted through the intermediate wall portion 25c is annularly wound around the intermediate wall portion 25c, the coil portions between the first magnetic field and the second magnetic field are opposite to each other. Current I flows. Therefore, according to Fleming's left-hand rule, the coil body 23 can obtain the thrust F in the same direction for the first magnetic field and the second magnetic field (see FIG. 1B), and the coil acts with two magnetic fields. A total thrust (2 × F) obtained by summing up the thrusts F can be obtained.

  In addition, in the present embodiment, the coil body 23 is wound around two coil wires 27a and 27b, so that the entire coil body 23 is compared with the case where one coil wire is wound. Even if the length and volume of the coil wires 27a and 27b to be used are the same, the length of one coil wire 27a (or 27b) is shortened, so that the resistance to current can be reduced for one coil wire. Moreover, since the plurality of coil wires are connected in parallel to the DC power supply, extremely large thrust can be obtained.

  That is, in the present embodiment, the coil body 23 can obtain a thrust of about twice the conventional magnetic field and about twice the current, so that a total of nearly four times the thrust can be obtained, and the coil body 23 is small. A high-thrust linear motor can be obtained.

  The yoke 17 is provided with a total of three wall parts, one side wall 25a extending along the relative driving direction of the coil body 23, the other side wall 25b, and an intermediate wall part 25c located in the middle thereof, and one side wall Since the magnets 19 may be provided on the side surfaces of the portion 25a and the other side wall portion 25b, the configuration is simple and the manufacture is easy.

  Further, in the present embodiment, the first magnetic field B and the second magnetic field B each close the magnetic path with the closed wall 25d to increase the magnetic flux density (the magnetic flux leakage is small), so that a higher thrust is achieved. Obtainable.

  In the present embodiment, it is possible to obtain a high thrust while being small in size, and in particular, when used as the lens driving device 1, it can be driven with high responsiveness.

  Next, another embodiment of the present invention will be described. In the embodiment described below, the same reference numerals are given to the portions having the same effects as those of the first embodiment described above. The detailed description of this part will be omitted, and the differences mainly from the first embodiment will be described.

  In the linear motor 1 according to the second embodiment, as shown in FIG. 5 (a), the yoke 17 has yoke component members 18a and 18b having a substantially U-shaped cross section arranged with the U-shaped openings next to each other. The intermediate wall portion 25c is formed by joining adjacent wall portions of the yoke constituent members 18a and 18b. In the present embodiment, the closing wall 25d of the yoke 17 is not provided. The coil body 23 is configured by winding a single coil wire.

  In the second embodiment, substantially the same functions and effects as those of the first embodiment are obtained except for the effects of the coil body 23 winding two coil wires in the first embodiment described above. In addition, since it is only possible to join the yoke constituent members 18a and 18b having a generally U-shaped cross section with versatility, it is easy to manufacture and can be easily manufactured using existing components. Is.

  Here, since the experiment which compared the thrust of the linear motor 1 concerning 2nd Embodiment and the conventional linear motor 40 shown in FIG.5 (b) was conducted, the result is shown in FIG. The conventional linear motor 40 uses one yoke component 18a constituting the linear motor 1 according to the second embodiment as the yoke 17. Other configurations, for example, the current flowing through the coil body 23 and the coil are the same.

  6 shows thrust values measured when various values of current are passed through the linear motor (present invention) 1 according to the second embodiment and the conventional linear (conventional product) shown in FIG. 5B. Is shown in a graph.

  As is clear from FIG. 6, according to the product of the present invention, when the current value is 100 Am or less, a thrust more than twice that of the conventional product can be obtained, and even when the current value is 100 Am or more, it is nearly twice as much. Thrust was able to be obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  For example, as shown in FIG. 7, the coil body 23 may be configured by winding a single coil wire without providing the closing wall 25d in the first embodiment.

  As shown in FIG. 8, in the second embodiment, a closing wall 25b may be provided.

  Here, as shown in FIG. 8, a comparative experiment was conducted between the case where the magnetic field space of the yoke 17 was closed by the closed wall 25d and the case where the closed wall 25 shown in FIG. Tables 1 and 2 show. Table 1 shows the case where the closing wall 25d is provided (see FIG. 8), and Table 2 shows the case where the closing wall 25d is not provided (see FIG. 5A).

  As is apparent from Tables 1 and 2, when the yoke 17 is provided with the closing wall 25d shown in FIG. 8 to close the magnetic field space, it is as high as about 10% at 100 mA or less and nearly 10% at 100 mA or more. Thrust was able to be obtained.

  As shown in FIG. 9, the coil body 23 is composed of two coil wires 26 and 27, and one coil wire 26 is wound inward to form an inner layer having a thickness W1. The coil wire 27 may be wound to form an outer layer having a thickness W2. In this coil body 23, each coil wire 26, 27 is wound from one end to the other end along the driving direction of the coil body 23, and the winding start end 26c, 27c of each coil wire is connected to one end in the driving direction, The winding end ends 26d and 27d are respectively combined with the other end in the driving direction and connected in parallel to the DC power source.

  Further, as shown in FIG. 10, the coil body 23 may include a coil portion 33 wound with one coil wire and a coil portion 35 wound with the other coil wire arranged adjacent to each other in the driving direction. Good.

It is a figure explaining the structure of the linear motor concerning this Embodiment, (a) is a cross-sectional view, (b) is a longitudinal cross-sectional view. It is a longitudinal cross-sectional view of the small camera using the linear motor concerning this Embodiment. It is AA sectional drawing of the small camera shown in FIG. It is a figure which shows the structure of a coil, (a) is a front view, (b) is a perspective view. (A) is a side view of the linear motor concerning 2nd Embodiment, (b) is a side view of the conventional linear motor. It is a graph which shows the result of the comparative experiment of the linear motor shown in FIG. It is a side view of the linear motor concerning a 3rd embodiment. It is a side view of the linear motor concerning 4th Embodiment. It is a figure which shows a deformation | transformation of a coil body, (a) is a side view explaining the structure of a coil body, (b) is a perspective view of (a). It is a longitudinal cross-sectional view of the linear motor using the coil body concerning another modification.

Explanation of symbols

1 lens drive device 7 first drive mechanism (linear motor)
9 Second drive mechanism (linear motor)
17 Yoke 19 Magnet 23 Coil body (coil)
25a One side wall part 25b The other side wall part 25c Intermediate wall part 25d Closed wall part 31 DC power supply

Claims (5)

  A linear motor that includes a yoke, a magnet, and a coil, and in which the coil is linearly driven relative to the yoke by electromagnetic force generated by energizing the coil, and the yoke is substantially parallel along the relative movement direction of the coil. One side wall and the other side wall, and an intermediate wall provided between the one side wall and the other side wall. The one side wall and the other side wall are provided with magnets on the side surfaces of the respective intermediate wall. The magnets are arranged with the same magnetic poles facing the intermediate wall portion side, and the coil forms a ring, and the inner peripheral side of the ring is inserted into the intermediate wall portion, and one side wall portion and the other side wall portion A linear motor characterized by being disposed between.   The yoke has a closed wall on each of one end side and the other end side in the relative movement direction of the coil, and the closed wall has a magnetic field formed by each wall portion of the one side wall portion, the other side wall portion, and the intermediate wall portion. The linear motor according to claim 1, wherein the linear motor is closed.   The yoke is provided with two yoke constituent members having a substantially U-shaped cross section, the U-shaped openings of the respective yoke constituent members are arranged next to each other, and the intermediate wall portion is formed by joining adjacent wall portions of the yoke constituent members. The linear motor according to claim 1, wherein the linear motor is provided.   The linear motor according to any one of claims 1 to 3, wherein the coil is formed by winding a plurality of coil wires, and each coil wire is connected in parallel to a DC power source. . A lens drive comprising the linear motor according to claim 1, wherein a lens holder of a small camera is attached to the coil, and the coil moves along the optical axis direction of the lens. apparatus.

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