JPH09154197A - Electromagnetic driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain miniaturization and low cost with high sensitivity by providing a coil and an endless conductor ring so as to obtain a prescribed torque at all times by means of a damping torque of the conductor ring independently of a motion of the coil. SOLUTION: A drive current based on an acoustic signal is supplied from an input terminal 9 to a voice coil 11 via a tinsel 14. When the drive current is supplied to the voice coil 11, since the voice coil 11 is placed in a magnetic field, the voice coil section 2 is vibrated vertically according to the Fleming's left-hand rule. When a large drive current is supplied to the voice coil, the amplitude of the vibration of the voice coil section 2 is increased and the voice coil 11 is going to be deviated downward from a magnetic gap g1. In this case, a 1st conductor ring 12 enters the magnetic gap g1 and a current is supplied to the conductor ring 12. Since the 1st conductor ring 12 is provided around the coil bobbin 10 to be short-circuited, then a damping torque going to move the voice coil section 2 upward is exerted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic drive device used for a lens drive device of an optical pickup, a speaker and the like, which obtains a driving force by applying a drive current to a coil arranged in a magnetic gap. .

[0002]

2. Description of the Related Art An electromagnetic driving device is a device for obtaining a driving force by passing a driving current through a coil arranged in a magnetic gap, and is used for a lens driving device of an optical pickup, a speaker and the like.

A loudspeaker, which is a device to which an electromagnetic drive device is applied, is mainly composed of a magnetic circuit 101 having a magnetic gap and a voice coil section having a voice coil arranged in the magnetic gap, as shown in FIG. 102 and a funnel-shaped diaphragm 10 attached to the voice coil unit 102.
3 and a funnel-shaped frame 104 attached to the magnetic circuit 101.

The magnetic circuit 101 includes a yoke 106 having a cylindrical center pole 105 formed in the center thereof, and an annular magnet 107 fixed on the yoke 106.
An annular plate 10 fixed on the magnet 107
8 and. In this magnetic circuit 101, as shown in FIG.
From the magnet 107 to the plate 1 as indicated by the middle arrow A
08, and a magnetic flux passing through the yoke 106 is generated,
A magnetic gap g is formed between the plate 108 and the center pole 105.

On the other hand, as shown in FIG. 24, which is an enlarged perspective view of the voice coil unit 102, and FIG. 25, which is a sectional view thereof, the voice coil unit 102 has a cylindrical coil bobbin 109 and a coil bobbin 109 wound around the coil bobbin 109. The voice coil 110 and the tinsel wire 111 led out from the voice coil 110. This voice coil unit 102
23, so that the voice coil 110 is located in the magnetic gap g where a uniform magnetic field is generated, as shown in FIG.
And, so that it can swing with respect to the frame 104,
It is attached to the frame 104 by a damper 112. Further, the tinsel wire 111 led out from the voice coil 110 is the input terminal 1 attached to the frame 104.
13 is connected.

An inner peripheral portion of the diaphragm 103 is fixed to the coil bobbin 109 of the voice coil portion 102, and an outer peripheral portion thereof is swingably attached to the frame 104.

When driving such a speaker, the voice coil 1 is fed from the input terminal 113 through the tinsel wire 111.
A drive current based on the acoustic signal is supplied to 10. Then, when a driving current flows through the voice coil 110, a driving force in a direction perpendicular to the magnetic gap g is generated in the voice coil 110 arranged in a uniform magnetic field according to Fleming's left-hand rule. Then, the voice coil unit 102 vibrates by this driving force, and the diaphragm 103 attached to the voice coil unit 102 vibrates accordingly, and as a result, a reproduced sound based on the acoustic signal is output.

[0008]

By the way, when the speaker is driven in this way, the voice coil moves perpendicularly to the magnetic gap as described above. However, in order to always obtain a constant driving force, the voice coil is required. It is necessary that a constant magnetic field is always applied to the voice coil regardless of the movement of the voice coil. That is, when the amplitude of the voice coil becomes large and the voice coil moves above the magnetic gap, or when the voice coil moves below the magnetic gap, the magnetic field applied to the voice coil is increased. Becomes weaker and the driving force changes.

Conventionally, as a method of preventing such a change in driving force, a method of sufficiently increasing the winding width of the voice coil or, conversely, a method of sufficiently reducing the winding width of the voice coil has been used. There is.

In the method in which the winding width of the voice coil is made sufficiently large, even if the amplitude of the voice coil portion is increased, the voice coil is always present over the entire range of the magnetic gap, so that the voice coil is thickened with respect to the plate thickness. Make the coil winding width large enough. When the winding width of the voice coil is sufficiently large in this way, the entire magnetic field generated in the magnetic gap is always applied to a part of the voice coil, and even if the voice coil section moves largely, a constant magnetic field is always generated. Applied to the coil.

However, if the winding width of the voice coil is increased, the effective length of the voice coil, that is, the length of the voice coil in the portion to which the magnetic field is actually applied becomes shorter than the total length of the voice coil. . Therefore, the weight of the entire voice coil is increased relative to the obtained driving force. Moreover, in order to increase the winding width of the voice coil, it is necessary to increase the length of the entire voice coil. Therefore, if the resistance of the voice coil is the same, it is necessary to use a thick wire with low resistance. This leads to an increase in coil weight. As described above, when the winding width of the voice coil is increased, the weight of the voice coil is increased and, as a result, the sensitivity is significantly reduced.

On the other hand, in the method in which the winding width of the voice coil is made sufficiently small, even if the amplitude of the voice coil portion becomes large, the voice coil is always present in the magnetic gap so that the entire voice coil is always present. Make the coil winding width sufficiently small. When the winding width of the voice coil is sufficiently small as described above, the magnetic field uniformly generated in the magnetic gap is always applied to the entire voice coil, and even if the voice coil section is largely moved, it is always constant. A magnetic field is applied to the voice coil.

However, when the winding width of the voice coil is reduced, the magnetic field applied to the voice coil is reduced.
The resulting driving force is greatly reduced. Therefore,
Even if the winding width of the voice coil is reduced, there is a problem that the sensitivity is significantly reduced.

As described above, according to the conventional method, the sensitivity is significantly lowered when the winding width of the voice coil is increased or when the winding width of the voice coil is decreased. Therefore, in the conventional method, in order to maintain the sensitivity, it is necessary to enlarge the magnetic circuit so that a large magnetic field is applied to the voice coil. As described above, in the conventional method, it is necessary to use a large magnetic circuit that is expensive to manufacture in order to maintain the sensitivity, and thus it is difficult to reduce the size and cost.

In the above description, the speaker is taken as an example, but such a problem is generally applicable to an electromagnetic drive device that obtains a driving force by supplying a driving current to a coil arranged in a magnetic gap. Therefore, for example, a similar problem occurs in a lens driving device of an optical pickup.

The present invention has been proposed in view of such conventional circumstances, and it is possible to always obtain a constant driving force irrespective of the movement of the coil. Further, the present invention is highly sensitive, downsized, and low in size. It is an object of the present invention to provide an electromagnetic drive device that can be priced.

[0017]

SUMMARY OF THE INVENTION An electromagnetic drive device according to the present invention completed to achieve the above object has a magnetic bobbin coupled to a driven body and a magnetic gap into which the coil bobbin is inserted. Circuit, and a coil and an endless conductor ring are provided at a position facing the magnetic gap of the coil bobbin. Here, examples of the driven body include a diaphragm and an objective lens.

In this electromagnetic drive device, as a conductor ring, a first conductor ring provided so as to circulate around the coil bobbin above the coil and a first conductor ring provided so as to circulate around the coil bobbin below the coil. It may be provided with two conductor rings.

In this electromagnetic drive device, the coil bobbin may be made of a conductive material, and the coil bobbin may also serve as the conductor ring. At this time, the conductor rings may be provided, for example, on the upper side and the lower side of the coil, or may be provided substantially at the center of the magnetic gap.

In such an electromagnetic drive device according to the present invention, when a drive current is supplied to the coil to drive the coil, a braking force that suppresses an unnecessary movement is generated by the conductor ring. Therefore, in this electromagnetic drive device, unnecessary movement is suppressed when the drive current is supplied to the coil for driving.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the following examples, and it goes without saying that the shape, material, and the like can be arbitrarily changed without departing from the gist of the present invention.

In the following description, in the first to third embodiments, an example in which the electromagnetic drive device according to the present invention is applied to a speaker will be described, and in the fourth embodiment, the electromagnetic drive device according to the present invention will be described. An example in which the driving device is applied to a lens driving device of an optical pickup will be described. However, the present invention can be widely applied to an electromagnetic drive device that obtains a driving force by passing a driving current through a coil arranged in a magnetic gap, and the application range of the present invention is a speaker or a speaker as described below. It is not limited to the lens driving device.

First Embodiment FIG. 1 shows a cross-sectional view of a speaker according to the present embodiment.
As shown in FIG. 1, the speaker according to the present embodiment is a cone type speaker, and mainly includes a magnetic circuit 1 having a magnetic gap and a voice coil unit 2 in which a voice coil is arranged.
And a funnel-shaped frame 3 attached to the magnetic circuit 1.
And a funnel-shaped diaphragm 4 attached to the magnetic circuit 1 and the voice coil unit 2.

The magnetic circuit 1 includes a yoke 6 having a cylindrical center pole 5 formed in the center thereof, a magnet 7 fixed on the yoke 6, and a plate 8 fixed on the magnet 7. . Here, the magnet 7 and the plate 8 are formed in an annular shape, and an opening is provided in the center. Then, the magnet 7 and the plate 8
The inner diameter of the opening is larger than the outer diameter of the center pole 5, and the inner diameter of the opening of the plate 8 is smaller than the inner diameter of the opening of the magnet 7. The yoke 6, the magnet 7 and the plate 8 are arranged so that their central axes coincide with each other, whereby a magnetic gap g1 is formed between the plate 8 and the center pole 5.

A funnel-shaped frame 3 is fixed to the upper surface of the plate 8 of the magnetic circuit 1. Here, an input terminal 9 is attached to the frame 3, and when the speaker is driven, the input terminal 9 is attached.
Drive current is input from.

On the other hand, as shown in FIG. 2 which is an enlarged perspective view of the voice coil unit 2 and FIG. 3 which is a sectional view thereof, the voice coil unit 2 has a cylindrical shape made of paper, metal foil, film or the like. A coil bobbin 10, a voice coil 11 made of a wire wound around the coil bobbin 10, such as copper, aluminum or copper clad aluminum, and a voice coil 1.
1, a first conductor ring 12 provided so as to circulate around the coil bobbin 10, a second conductor ring 13 provided so as to circulate around the coil bobbin 10 below the voice coil 11, and a voice coil 11 And two tinsel cords 14 respectively derived from the winding start and the winding end.

The coil bobbin 10 has an inner diameter larger than the outer diameter of the center pole 5 and an outer diameter smaller than the inner diameter of the opening of the plate 8.
The first conductor ring 12 and the second conductor ring 13 provided so as to surround the coil bobbin 10 are made of a conductive material such as aluminum foil and short-circuit the coil bobbin 10 for one turn. Is wound like.

The coil bobbin 10 is generally a coil bobbin 10a of a type in which thin spiral paper is wound in a cylindrical shape as shown in FIG. 4 or a coil bobbin 10a as shown in FIG.
There are a coil bobbin 10b of a type in which a strip-shaped material is rolled and abutted at both ends, and a coil bobbin 10c for a dielectric speaker of a type in which a conductive material is processed into a cylindrical shape as shown in FIG. In the embodiment, any type of coil bobbin may be used.

Then, such a voice coil unit 2 is
As shown in FIG. 1, after being inserted into the center pole 5 so that the central axes thereof coincide with each other, the damper 15 holds the frame 3 so as to be swingable. Here, in the voice coil unit 2, when the speaker is not driven, the center of the voice coil 11 is located substantially at the center of the magnetic gap g1 and the first conductor ring 12 is positioned at the magnetic gap g.
It is held by the damper 15 so that it is located above 1 and the second conductor ring 13 is located below the magnetic gap g1.

Further, the tinsel wire 14 led out from the voice coil 11 is connected to the input terminal 9 attached to the frame 3. When reproducing an acoustic signal, the tinsel wire 14 is connected to the tinsel wire 14 from the input terminal 9. The drive current is supplied to the voice coil 11 via the voice coil 11.

A diaphragm 4 is attached to the voice coil section 2 as described above. Here, the diaphragm 4
Is formed in a funnel shape, and its inner peripheral portion is fixed to the upper portion of the coil bobbin 10 of the voice coil portion 2 with an adhesive or the like. An edge 16 is provided on the outer peripheral portion of the diaphragm 4 so that the diaphragm 4 can swing with respect to the frame 3. The outer periphery of the edge 16 is attached to the frame 3 by using a gasket 17. It is installed.
The voice coil unit 2 is provided at the center of the diaphragm 4.
A dustproof cap 18 is attached so as to cover the center pole 5.

Next, a method of manufacturing the speaker having the above structure will be described.

When manufacturing the speaker, first, as shown in FIG. 7, the yoke 6, the magnet 7 and the plate 8 are fixed to each other to manufacture the magnetic circuit 1.

Here, in manufacturing the magnetic circuit 1, first, an adhesive is applied to the upper surface of the yoke 6, and the magnet 7 is fixed to the upper surface of the yoke 6 by this adhesive. Here, a magnet guide 6 a for positioning the magnet 7 is formed on the upper surface of the yoke 6 in advance. Here, the magnet guide 6a is formed as a convex portion whose outer diameter substantially matches the inner diameter of the opening of the magnet 7 and whose center coincides with the center of the center pole 5. Then, the magnet 7 is fitted into the magnet guide 6a, and then the yoke 6 and the magnet 7 are fixed. As a result, the yoke 6 and the magnet 7 are fixed to each other with the center axis of the center pole 5 and the center axis of the magnet 7 aligned.

After that, an adhesive is further applied to the upper surface of the magnet 7, and the plate 8 is fixed to the upper surface of the magnet 7 by this adhesive. Here, when the magnet 7 and the plate 8 are fixed to each other, the inner diameter is substantially equal to the outer diameter of the center pole 5, and the outer diameter is the plate so that the central axis of the plate 8 and the central axis of the center pole 5 coincide with each other. A gap guide, which is a cylindrical guide member substantially matching the inner diameter of the opening of No. 8, is used. That is, by inserting the gap guide into the center pole 5 and inserting the plate 8 from above, the center axis of the plate 8 and the center axis of the center pole 5 are aligned. Then, in this way, the center axis of the plate 8 and the center axis of the center pole 5 are made to coincide with each other, and as described above, the magnet 7 and the plate 8 are fixed by the adhesive, and then the gap guide is removed. .

Through the above steps, as shown in FIG.
The magnetic circuit 1 to which the yoke 6, the magnet 7 and the plate 8 are fixed is completed.

Next, the magnetic circuit 1 manufactured as described above.
The funnel-shaped frame 3 is attached to the upper surface of the plate 8 and then the voice coil unit 2 is incorporated as shown in FIG. Here, when the voice coil unit 2 is incorporated in the magnetic circuit 1, as shown in FIG. 8, the voice coil 11 is arranged at a predetermined position within the magnetic gap g1 formed by the magnetic circuit 1. Voice coil spacer 19
Use Here, the voice coil spacer 19 is a guide member for arranging the voice coil portion 2 at a predetermined position, the outer diameter of which is substantially equal to the inner diameter of the voice coil portion 2, and the inner diameter of which is outside the center pole 5. It has a cylindrical portion that substantially matches the diameter. The voice coil unit 2 is attached to the magnetic circuit 1.
When assembling, the voice coil spacer 19 is inserted into the center pole 5, and the voice coil portion 2 is inserted from above. As a result, the center axis of the center pole 5 and the center axis of the voice coil unit 2 coincide with each other, and the voice coil 11 is arranged at a predetermined position within the magnetic gap g1 formed by the magnetic circuit 1.

Then, with the voice coil spacer 19 positioning the voice coil portion 2 as described above, first, the damper is arranged so that the voice coil portion 2 is swingably held with respect to the magnetic circuit 1. Attach 15.
Here, the damper 15 is attached by bonding the inner periphery of the damper 15 to the outer periphery of the coil bobbin 10 of the voice coil unit 2 and the outer periphery of the damper 15 to the inner side of the frame 3.

Next, the diaphragm 4 having the edge 16 formed on the outer peripheral portion is attached so that the voice coil portion 2 can swing with respect to the frame 3. Here, the diaphragm 4 is attached by bonding the inner circumference of the diaphragm 4 to the outer circumference of the coil bobbin 10 of the voice coil unit 2 and the outer circumference of the edge 16 of the diaphragm 4 to the inside of the frame 3. Done by. Paper is usually used for the diaphragm 4, and the diaphragm 4 made of paper is generally called cone paper.

After the voice coil section 2 and the diaphragm 4 are attached by the above steps, the voice coil spacer 19 arranged between the center pole 5 and the voice coil section 2 is removed. After that, the cap 18 is attached to the diaphragm so as to cover the opening of the diaphragm 4, that is, the voice coil section 2 and the center pole 5, and the voice coil 11 of the voice coil section 2 is covered.
The tinsel wire 14 derived from is soldered to the input terminal 9 attached to the frame 3. Finally, by magnetizing the magnet 7, the speaker according to the present embodiment is completed.

Next, the operation of the above speaker will be described.

When driving the speaker, a drive current based on an acoustic signal is supplied from the input terminal 9 to the voice coil 11 through the tinsel wire 14. And voice coil 1
When a drive current flows through the voice coil 1, the voice coil 11 is arranged in the magnetic field, and therefore the voice coil unit 2 vibrates up and down according to the Fleming left-hand rule. Since the diaphragm 4 is attached to the voice coil unit 2, when the voice coil unit 2 vibrates, the diaphragm 4 also vibrates together with the voice coil unit 2, and the vibration of the diaphragm 4 is based on the acoustic signal. Playback sound is output.

At this time, in the conventional speaker, when a large drive current flows through the voice coil, the amplitude of vibration of the voice coil portion increases, and the voice coil portion vibrates even outside the magnetic gap. Such driving force is generated. Moreover, when the voice coil is disengaged from the magnetic gap, an inertial force is generated in the voice coil portion, so a force acts in a direction in which the voice coil is further disengaged from the magnetic gap. In the conventional speaker, when the voice coil is disengaged from the magnetic gap, the voice coil returns to the magnetic gap due to the stiffness of the speaker support system, that is, the stiffness of the damper and the stiffness of the edge. As a result, the vibration of the voice coil section is maintained.

On the other hand, in the speaker according to the present embodiment, when the voice coil 11 is about to come off from the magnetic gap g1, the first conductor ring 12 enters the magnetic gap g1. First conductor ring 1
2, a current flows. Here, since the first conductor ring 12 is provided so as to go around the coil bobbin 10 and short-circuit, the braking force that moves the voice coil unit 2 upward acts.

Similarly, when the voice coil 11 is about to move upward from the magnetic gap g1, the second conductor ring 13 enters the magnetic gap g1 and a current flows through the second conductor ring 13. Here, since the second conductor ring 13 is provided so as to circulate around the coil bobbin 10 and short-circuit, a braking force for moving the voice coil portion 2 downward acts.

Specifically, for example, in a full-band speaker with a diameter of 65 mm in which the first conductor ring 12 and the second conductor ring 13 having a thickness of 30 μm are provided, the vibration velocity of the voice coil portion 2 is 8.14. × 10 ⁻¹ m / s, the resistance of the first conductor ring 12 and the second conductor ring 13 is
0.96 × 10 ⁻² Ω, and at this time, the braking force by the first conductor ring 12 or the second conductor ring 13 at the lowest resonance frequency f0 is 0.41N, and the voice coil 11 at the lowest resonance frequency f0. The driving force by
It becomes 0.55N. As described above, the braking force by the first conductor ring 12 or the second conductor ring 13 is sufficiently large with respect to the driving force by the voice coil 11, and the movement of the voice coil 11, that is, the voice coil portion 2 and the diaphragm 4.
Will be damped by the first conductor ring 12 or the second conductor ring 13.

As described above, in the loudspeaker according to the present embodiment, when the voice coil 11 is about to come out of the magnetic gap g1, the voice coil section is made by the first conductor ring 12 or the second conductor ring 13. Since the braking force acts on the vibration of 2, the over-vibration in which the voice coil 11 is disengaged from the magnetic gap g1 is prevented. Therefore, in the speaker according to the present embodiment, the voice coil unit 2 vibrates very smoothly, and as a result, the distortion of the sound particularly in the low frequency range is significantly reduced.

When the speaker is driven, the heat generated from the voice coil section 2 may become a problem, but in the speaker according to the present embodiment, the first conductor ring 1
The second conductor ring 13 and the second conductor ring 13 do not significantly affect such heat generation. This is the first conductor ring 12
Since the second conductor ring 13 and the second conductor ring 13 have very low resistance, they hardly generate heat, and the heat generation in the voice coil unit 2 can be regarded as only the heat generation from the voice coil 11 as in the conventional speaker. is there.

Next, the results of evaluating the characteristics of the above speaker will be described.

The characteristics are evaluated by φ65 according to the present embodiment.
The frequency characteristics of the impedance, the distortion rate, and the output sound pressure level when a 2 W input is made are measured for a mm-diameter speaker and a conventional φ65 mm-diameter speaker according to JIS.
The measurement was performed using a measurement box. The measurement results of these characteristics are shown in FIGS. Here, FIG. 9 shows the measurement results of the characteristics of the speaker according to the present embodiment in which the winding width of the voice coil is 3.2 mm, and FIG. 10 is the present embodiment in which the winding width of the voice coil is 6.5 mm. FIG. 11 is a measurement result of the characteristic of the speaker according to the embodiment, and FIG. 11 is a measurement result of the characteristic of the conventional speaker. From these measurement results, in the speaker according to the present embodiment, the distortion in the low frequency range, that is, the distortion in the vicinity of the minimum resonance frequency f0 is reduced, and the sound quality is improved, compared with the conventional speaker. I understand.

In the above description, the voice coil unit 2
The first conductor ring 12 and the second conductor ring 13 are provided in the first conductor ring 12 and the second conductor ring 13.
Only one of them may be provided in the voice coil unit 2. That is, as shown in FIG. 12, the voice coil unit 2 may be provided with only the first conductor ring 12 and not provided with the second conductor ring. In such a speaker, when the voice coil 11 is about to come off from the magnetic gap g1, the first conductor ring 12 exerts a braking force to move the voice coil portion 2 upward, and thus the present invention is realized. The effect is obtained. Similarly, as shown in FIG. 13, the voice coil unit 2 may be provided with only the second conductor ring 13 and not provided with the second conductor ring. In such a speaker, when the voice coil 11 is about to come off from the magnetic gap g1, the second coil
The conductor ring 13 causes a braking force to move the voice coil portion 2 downward, and the effect of the present invention is obtained.

Second Embodiment In the speaker according to the first embodiment, the voice coil portion is provided with the conductor ring. However, the coil bobbin is formed of a conductive material so that the coil bobbin also serves as the conductor ring. Good. Therefore, a speaker in which the coil bobbin also serves as a conductor ring will be described below.

In the following description, the same members as those of the speaker according to the first embodiment are designated by the same reference numerals as those of the speaker according to the first embodiment, and detailed description thereof will be omitted. There is.

FIG. 14 shows a cross-sectional view of the speaker according to this embodiment. As shown in FIG. 14, the speaker according to the present embodiment is a cone type speaker similar to the speaker according to the first embodiment, and the configuration other than the voice coil unit is the same as that of the first embodiment. It is similar to the speaker.

In this speaker, the voice coil unit 3
1 is an enlarged perspective view of the voice coil unit 30. FIG.
5, and a cross-sectional view of FIG. 16, a substantially cylindrical coil bobbin 31 made of a conductive material such as aluminum foil, a voice coil 32 wound around the coil bobbin 31, and a winding start of the voice coil 32. And two tinsel cords 33 respectively derived from the winding end.

Here, in the coil bobbin 31, a slit 31a is formed in a portion around which the voice coil 32 is wound, and a slit 31b is also formed above the portion in which the voice coil 32 is wound. . The slits 31a and 31b form a first conductor ring portion 31c formed on the upper side of the voice coil 32 such that the coil bobbin 31 circulates, and a lower portion of the voice coil 32 formed on the coil bobbin 31 circulate. The formed second conductor ring portion 31d is formed. That is, the coil bobbin 31 is formed into one turn so that the coil bobbin 31 is short-circuited in the first conductor ring portion 31c formed on the upper side of the voice coil 32, and similarly formed on the lower side of the voice coil 32. The second done
In the conductor ring portion 31d, the coil bobbin 31 has one turn so as to be short-circuited.

The coil bobbin 31 can be easily manufactured by, for example, press-molding a conductive material into a cylindrical shape and then punching out the slits 31a and 31b.

In the speaker according to this embodiment, the first conductor ring portion 31c formed on the coil bobbin 31 functions similarly to the first conductor ring 12 of the speaker according to the first embodiment. The coil bobbin 31
The second conductor ring portion 31d formed in the same function as the second conductor ring 13 of the speaker according to the first embodiment.

Therefore, also in the loudspeaker according to the present embodiment, when the voice coil 32 is about to come off the magnetic gap g1, the braking force acts on the voice coil portion 30 so that the voice coil 32 moves from the magnetic gap g1. Excessive vibration that may come off is prevented. Therefore,
Also in the speaker according to the present embodiment, the voice coil unit 30
Vibration is very smooth, and as a result, the distortion of the sound is significantly reduced, especially in the low range.

Further, in the speaker according to the present embodiment,
Since it is not necessary to newly provide the first conductor ring and the second conductor ring, it is possible to reduce the weight of the coil bobbin portion as compared with the speaker according to the first embodiment. Therefore, the speaker according to the present embodiment can obtain higher sensitivity.

Third Embodiment In the speaker according to the second embodiment, the first conductor ring portion and the second conductor ring portion are provided above and below the voice coil, but the conductor ring portion is provided in the voice coil. May be provided only at one place. Therefore, a speaker of the type in which the coil bobbin is provided with only one conductor ring will be described below.

In the following description, the same members as those of the speaker according to the first embodiment are designated by the same reference numerals as those of the speaker according to the first embodiment, and detailed description thereof will be omitted. There is.

FIG. 17 shows a cross-sectional view of the speaker according to this embodiment. As shown in FIG. 17, the speaker according to the present embodiment is a cone type speaker similar to the speaker according to the first embodiment, and the configuration other than the voice coil unit is the same as that of the first embodiment. It is similar to the speaker.

In this speaker, the voice coil unit 4
1 is an enlarged perspective view of the voice coil unit 40. FIG.
8, and a cross-sectional view thereof as shown in FIG. 19, a substantially cylindrical coil bobbin 41 made of a conductive material such as aluminum foil, a voice coil 42 wound around the coil bobbin 41, and a winding start of the voice coil 42. And two tinsel cords 43 respectively derived from the winding end.

Here, in the coil bobbin 41, as shown in FIG. 20, a conductor ring portion 41a is formed in the center of a portion around which the voice coil 42 is wound, the conductor ring portion 41a being formed so as to circulate. This conductor ring portion 41
Slits 41b are formed on the upper and lower sides, leaving a. That is, the coil bobbin 41 has one turn so that the coil bobbin 41 is short-circuited in the conductor ring portion 41a formed in the center of the portion where the voice coil 42 is wound.

In the speaker according to this embodiment, when the voice coil section 40 vibrates, the coil bobbin 4
An electric current flows through the conductor ring portion 41a provided in No. 1 to generate a braking force against the vibration of the voice coil portion 40. Then, in the speaker according to the present embodiment, this braking force suppresses unnecessary over-vibration of voice coil unit 40, and as a result, distortion of sound particularly in the low range is reduced.

Fourth Embodiment A perspective view of a lens driving device according to the present embodiment is shown in FIG. 21, and a transverse sectional view thereof is shown in FIG.
As shown in these figures, the lens driving device according to the present embodiment includes a mounting substrate 50 that serves as a mounting portion for an optical pickup in which the lens driving device is incorporated, and a pair of fan-shaped curved arc-shaped members. Outer side yokes 51a, 5
1b and a pair of fan-shaped inner peripheral side yokes 52a, which are curved and formed in an arc shape smaller than the outer peripheral side yokes 51a, 51b.
52b and a pair of fan-shaped magnets 53a, 53 curved in an arc shape similar to the inner yokes 52a, 52b.
and a magnetic circuit 54 composed of b.

In this magnetic circuit 54, the outer peripheral yokes 51a, 51b and the inner peripheral yokes 52a, 52b are arranged such that the outer peripheral yokes 51a, 51b are on the outer side, and the inner peripheral yoke 5 is formed.
It is arranged on the mounting substrate 50 so that 2a and 52b are inside. In addition, the outer peripheral side yokes 51a and 51b and the inner peripheral side yokes 52a and 52b are one outer peripheral side yoke 51.
a and the magnetic gap G1 between one inner peripheral side yoke 52a.
Are formed so as to be opposed to each other so that a magnetic gap G2 is formed between the other outer peripheral side yoke 51b and the other inner peripheral side yoke 52b. Here, the outer peripheral side yokes 51a and 51b are directly attached to the mounting substrate 50, and the inner peripheral side yokes 52a and 52b
52b is attached to the attachment substrate 50 via magnets 53a and 53b. That is, the inner yoke 5
In the portions 2a and 52b, magnets 53a and 53b are arranged on the mounting substrate 50.
Inner side yokes 52a and 52b on a and 53b, respectively.
Are arranged.

In the magnetic circuit 54 as described above, the inner peripheral side yoke 52a and the outer peripheral side yoke 51 are connected to the magnet 53a.
A magnetic flux that passes through a is generated, and the magnet 5
A magnetic flux is generated from 3b so as to pass through the inner yoke 52b and the outer yoke 51b. And the outer yoke 5
A magnetic gap G1 is formed between the outer peripheral side yoke 51b and the inner peripheral side yoke 52a.
A magnetic gap G2 is formed between b.

In addition, the lens driving device is a substantially cylindrical lens driving device in which the cylindrical support shaft 55 which is erected on the mounting substrate 50 at the center of the magnetic circuit 54 and the objective lens 56 are mounted. And a part 57.

Here, the lens drive section 57 includes a support shaft 55.
Corresponding to the circular opening and a pair of inner peripheral side yokes 52
Fan-shaped openings corresponding to a and 52b are formed. A focus driving coil 58 is wound around the outer peripheral surface of the lens driving portion 57, and a first conductor ring 59 is provided above the focus driving coil 58.
And a second conductor ring 60 is provided below the focus driving coil 58. Here, the first conductor ring 59 and the second conductor ring 60 are made of a conductive material such as aluminum foil, and are provided so as to short-circuit the lens driving unit 57 by one turn.

In the lens driving section 57, the central axis of the support shaft 55 and the central axis of the lens driving section 57 are aligned with each other, and the inner peripheral side yokes 52a and 52b are arranged in the fan-shaped opening. A circular opening is inserted into the support shaft 55,
Thereby, it is held so as to be slidable in the axial direction with respect to the support shaft 55. Here, the lens driving unit 57
When the lens driving device is not driven, the focus driving coil 58 is located substantially in the center of the magnetic gaps G1 and G2, and the first conductor ring 59 is located above the magnetic gaps G1 and G2. , The second conductor ring 6
0 is arranged below the magnetic gaps G1 and G2. In addition, the lens driving unit 57 is provided with a supporting member (not shown) made of a rubber material or the like that is elastically displaceable.
The optical axis of the optical pickup in which this lens driving device is incorporated and the optical axis of the objective lens 56 attached to the lens driving unit 57 are held so as to coincide with each other.

A drive current is supplied to the focus drive coil 58 when the lens drive device having the above-described structure is driven, that is, when the objective lens 56 is moved in the axial direction of the support shaft 55 to perform focus control. To do. When a drive current flows through the focus drive coil 58, the focus drive coil 58 is arranged in the magnetic gaps G1 and G2, so that the lens drive unit 57 moves in the axial direction of the support shaft 66 according to the Fleming's left-hand rule. Then, the focus control is performed.

At this time, if the drive current supplied to the focus driving coil 58 is large, such a large driving force that the lens driving portion 57 tries to move the focus driving coil 58 to the outside of the magnetic gaps G1 and G2. Power is generated.

However, in the lens driving device according to this embodiment, the focus driving coil 58 has the magnetic gap G.
When it is about to come off from 1, G2, the first conductor ring 59 enters the magnetic gaps G1, G2,
A current flows through this first conductor ring 59, which causes
A braking force acts to move the lens driving unit 57 upward. Similarly, when the focus driving coil 58 is about to come off from the magnetic gaps G1 and G2, the second conductor ring 60 enters the magnetic gaps G1 and G2, and a current flows through the second conductor ring 60. Flows, which causes a braking force to move the lens driving unit 57 downward.

Therefore, in the lens driving device according to the present embodiment, when the focus driving coil 58 is about to come out of the magnetic gaps G1 and G2, the first conductor ring 59 or the second conductor ring 60 is used. Since the braking force acts, it is possible to prevent the focus driving coil 58 from coming off the magnetic gaps G1 and G2.
Therefore, in the lens driving device according to the present embodiment,
Unnecessary movement of the focus driving coil 58 is suppressed, and as a result, the lens can be driven with higher accuracy.

In the above description, focus control has been mainly described, but the present invention can be similarly applied to a lens driving device for performing tracking control. That is, the present invention can be applied to, for example, a lens driving device of a type in which the tracking driving coil is wound around the lens driving portion in the axial direction of the support shaft in addition to the focus driving coil as described above. When the present invention is applied to such a lens driving device, for example, the tracking driving coil is wound around the lens driving unit in the axial direction of the spindle, and the tracking driving coil is mounted on both sides of the tracking driving coil. A conductor ring that circulates in the axial direction may be provided.

When performing tracking control with such a lens driving device, a driving current is supplied to the tracking driving coil. As a result, the lens driving unit rotates in the direction around the axis of the support shaft, and tracking control is performed. Even in such a lens driving device, as in the case of the focus control in the lens driving device described above, when the tracking driving coil is about to come out of the magnetic gap, the braking force is exerted by the conductor ring, It is possible to prevent the tracking drive coil from coming off the magnetic gap. Therefore, by applying the present invention to a lens driving device that performs tracking control, unnecessary movement of the tracking driving coil is suppressed, and as a result, the lens can be driven with higher accuracy.

[0079]

As is apparent from the above description, in the electromagnetic drive device according to the present invention, when the coil is driven by supplying the drive current, the conductor ring exerts a braking force that suppresses unnecessary movement. Occurs. Therefore, in this electromagnetic drive device, unnecessary movement is suppressed when the drive current is supplied to the coil for driving.

Therefore, for example, when the electromagnetic drive device according to the present invention is applied to a speaker, unnecessary movement due to the voice coil is suppressed, and as a result, distortion of sound particularly in the low range is reduced and sound quality is improved. To be done.

Further, for example, when the electromagnetic drive device according to the present invention is applied to a lens drive device for an optical pickup, unnecessary movement due to a focus drive coil, a tracking drive coil, etc. is suppressed, and as a result, higher movement is achieved. It is possible to drive the lens with high accuracy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a speaker to which the present invention is applied.

FIG. 2 is a perspective view showing a voice coil unit used in the speaker shown in FIG.

3 is a cross-sectional view of the voice coil unit shown in FIG.

FIG. 4 is a perspective view showing an example of a coil bobbin.

FIG. 5 is a perspective view showing another example of the coil bobbin.

FIG. 6 is a perspective view showing another example of the coil bobbin.

FIG. 7 is a cross-sectional view showing a state in which a magnetic circuit is manufactured.

FIG. 8 is a cross-sectional view showing how a voice coil unit is incorporated in a magnetic circuit.

FIG. 9 is a diagram showing a result of measuring characteristics of the speaker according to the first embodiment in which the winding width of the voice coil is 3.2 mm.

FIG. 10 is a diagram showing a result of measuring characteristics of the speaker according to the first embodiment in which the winding width of the voice coil is 6.5 mm.

FIG. 11 is a diagram showing a result of measuring characteristics of a conventional speaker.

FIG. 12 is a cross-sectional view showing another configuration example of the speaker to which the present invention is applied.

FIG. 13 is a cross-sectional view showing another configuration example of the speaker to which the present invention is applied.

FIG. 14 is a cross-sectional view showing another configuration example of the speaker to which the present invention is applied.

FIG. 15 is a perspective view showing a voice coil unit used in the speaker shown in FIG.

16 is a transverse cross-sectional view of the voice coil unit shown in FIG.

FIG. 17 is a cross-sectional view showing another configuration example of the speaker to which the present invention is applied.

18 is a perspective view showing a voice coil unit used in the speaker shown in FIG.

FIG. 19 is a cross-sectional view of the voice coil unit shown in FIG.

20 is a perspective view showing a coil bobbin of the voice coil unit shown in FIG. 18. FIG.

FIG. 21 is a perspective view showing a configuration example of a lens driving device to which the present invention has been applied.

22 is a cross-sectional view of the lens driving device shown in FIG.

FIG. 23 is a transverse cross-sectional view showing a configuration example of a conventional speaker.

FIG. 24 is a perspective view showing a voice coil unit used in the speaker shown in FIG. 23.

25 is a cross-sectional view of the voice coil unit shown in FIG.

[Explanation of symbols]

 1 magnetic circuit 2 voice coil part 3 frame 4 diaphragm 5 center pole 6 yoke 7 magnet 8 plate 9 input terminal 10 coil bobbin 11 voice coil 12 first conductor ring 13 second conductor ring 14 tinsel wire 15 damper 16 edge 17 gasket 18 Cap g1 Magnetic gap

Claims (7)

[Claims] 1. A coil bobbin coupled to a driven body,
A magnetic circuit having a magnetic gap into which the coil bobbin is inserted, the electromagnetic drive device comprising a coil and an endless conductor ring provided at a position facing the magnetic gap of the coil bobbin. 2. The electromagnetic drive device according to claim 1, wherein the driven body is a diaphragm. 3. The electromagnetic drive device according to claim 1, wherein the driven body is an objective lens. 4. As the conductor ring, a first conductor ring provided so as to surround the coil bobbin above the coil, and a second conductor ring provided so as to surround the coil bobbin below the coil. The electromagnetic drive device according to claim 1, further comprising: 5. The coil bobbin is made of a conductive material,
The electromagnetic drive device according to claim 1, wherein the coil bobbin also serves as the conductor ring. 6. The electromagnetic drive device according to claim 5, wherein the conductor rings are provided on an upper side and a lower side of the coil. 7. The electromagnetic drive device according to claim 5, wherein the conductor ring is provided substantially at the center of the magnetic gap.