JPH0720317B2 - Electromagnetic driver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in which a driving driver is provided in a part of the housing of an audio device such as a television or a cassette recorder with a radio, and sound is reproduced by vibrating the housing. Related to the speaker.

Configuration of Conventional Example and Problems Thereof In recent years, audio equipment such as a television and a cassette recorder with a radio has been remarkably compact in shape. Here, taking a television cassette as an example and describing its problems, the speaker shape is one of the factors that hinder the compactness. For this reason, measures such as adopting a rectangular speaker with a good space factor and mounting the speaker on the side surface of the set have been made.

However, even if the shape of the speaker is rectangular, a space for the speaker is required on the entire surface of the set, and thus there is a limit to downsizing. Also, when the speaker is received on the side of the set, the speaker has directivity in sound pressure characteristics, so that the sound pressure in the high range is significantly reduced at a position deviated from the front axis of the speaker, that is, at the front of the set, and the sound quality is deteriorated. There was a problem. Further, in the method of mounting the speaker on the side surface, there is a drawback that sound reproduction becomes difficult if there is an obstacle on the side surface and the installation place of the set is limited.

In order to solve these problems, a reproducing method has been considered in which a driver for driving is attached to the front panel of the entire surface of the cathode ray tube constituting the set and driven, and the front panel is used as a diaphragm.

As the driving driver, an electromagnetic type driver having a simple structure and a large mechanical strength is used as compared with an electrodynamic type driver which requires a voice coil as a movable part. However, in the conventional electromagnetic driver, a diaphragm made of ferromagnetic material such as soft iron,
The magnitudes of the static attraction force and the driving force are greatly affected by the magnetic gap between the static attraction force and the exciting portion that generates the driving force corresponding to the electric signal on the diaphragm.
That is, with respect to the vertical movement of the diaphragm, the driving force is large in the direction in which the diaphragm approaches the excitation part because the magnetic gap is small, and the driving force is small when the diaphragm retreats because the magnetic gap is large. Asymmetry had occurred. Therefore, the sound pressure reproduced from the front panel also has a large amount of distortion components. The vibrating plate is held by the suspension so as to maintain a predetermined magnetic gap without being attracted to the exciting portion by the static attraction force of the permanent magnet. For this reason, the suspension is constantly stressed, and in order to withstand long-term use,
It was necessary to pay great attention to the material, structure, and fixing method, and there was also a problem with reliability.

In order to solve the above-mentioned drawback, an electromagnetic driver of static attraction force balance type, which is composed of two exciting portions opposed to each other on the plate surface and a diaphragm, has been considered.

The conventional speaker of this type will be described below.

FIG. 1 is a perspective view of a television set adopting this type of speaker, in which 1 is a cabinet, 2 is a cathode ray tube,
3 is a front panel mounted on the front surface of the cathode ray tube 2 and made of a material having a high light transmittance such as transparent acrylic, and 4 is an electromagnetic driving driver (hereinafter referred to as an electromagnetic driver) mounted on the back surface of the front panel 3. It is called).

FIG. 2 shows a structural cross-sectional view of the above electromagnetic type driver. FIG. 2 (a) is the same structural cross-sectional view and FIG. 2 (b) is a second.
It is the sectional view on the I-II line of FIG. In Figure 2, 5a, 5b
Is a center pole with a hole in the center plate 6a, 6b
It is integrally or mechanically coupled with. 7a and 7b are exciting coils wound on the center poles 5a and 5b, and 8a and 8b are plates 6
The ring-shaped permanent magnets arranged on the a and 6b constitute two exciting portions facing each other on the surfaces of the plates 6a and 6b. 9a and 9b are diaphragms, and a recess having an opening at the center is provided at the center, and the suspension 1 is provided via spacers 10a and 10b.
It is fixed to 1 with screws 12 and nuts 13. Further, the outer peripheral portion of the suspension 11 has ring-shaped spacers 14a, 14a as fixing portions provided on the bottom surface of the periphery of the plates 6a, 6b.
The vibrating plates 9a and 9b are fixed to each other with an adhesive or the like via b, and are arranged with predetermined intervals l _g1 and l _g2 provided between the vibrating plates 9a and 9b.

The upper surface of the diaphragm 9a is firmly fixed to the front panel 3 of the TV set.

The operation of the conventional electromagnetic driver constructed as described above will be described below.

The two vibrating plates 9a and 9b are arranged with the same magnetic gaps l _g1 and l _g2 between the two opposing exciting parts, so that the static attraction forces by the permanent magnets 8a and 8b cancel each other out. Suspension 11 becomes zero in steady state with no electrical signal
There is no stress on. The state of this static suction force
Shown in the figure. In FIG. 3, I is a static attraction force acting on the diaphragm 9a, and II is a static attraction force acting on the diaphragm 9b.
The attraction force III, which is a combination of the static attraction forces I and II, acts on 9a and 9b. From this figure, it can be seen that the static attractive force is zero in the steady state where both magnetic gaps l _g1 and l _g2 are equal.

The exciting coils 7a, 7b are connected in series or in parallel and correspond to the signal current flowing in the exciting coils 7a, 7b for applying an electric signal,
The magnetic force acting on the diaphragms 9a, 9b supported by the suspension 11 in the state of zero stress via the spacers 10a, 10b is changed to generate a driving force. FIG. 4 shows the state of the driving force generated on the diaphragms 9a and 9b. In FIG. 4, A is a diaphragm 9a.
Is a driving force generated on the diaphragm 9b, and a driving force C that is a combination of the driving forces A and B acts on both diaphragms 9a and 9b. When an electric signal is applied, the diaphragms 9a and 9b move up and down, but with respect to the upper and lower passages, when the magnetic gap of one diaphragm becomes narrower, the other becomes wider, so that the structure is symmetrical. The driving force can be made symmetrical as shown in FIG. 4C.

As described above, in the steady state, the electromagnetic driver composed of the two exciting parts and the vibrating plate that oppose each other on the plate surface cancels the static attractive force to make the stress applied to the suspension 11 zero, so that it can be used for a long time. On the other hand, there was a great effect that the reliability was greatly improved and the driving force was made symmetrical so that the sound pressure distortion reproduced from the front panel could be reduced.

However, in the electromagnetic driver having the above-described configuration, the outer diameter of the suspension is the same as the outer diameter of the magnet. Therefore, when the outer diameter of the magnet is small, the stiffness of the suspension becomes large and the resonance frequency of the driver becomes high. There was a problem that the sound reproduced from was lacking in bass.

SUMMARY OF THE INVENTION It is an object of the present invention to realize a static attraction force balanced type electromagnetic driver which can easily reproduce low-pitched sound because it solves the above problems.

Configuration of the Invention In order to achieve the above object, an electromagnetic driver of the present invention includes: two disk-shaped plates, which are integrated with a center pole having a hole in the center, and the two disk-shaped plates. An exciting coil wound around the center pole is arranged on the upper side, and ring-shaped permanent magnets having an outer shape smaller than the outer shape of the disc-shaped plate are arranged on the outer peripheral portion of the exciting coil. And a suspension formed by fixing the plates to each other via a fixing portion between the outer peripheral bottom surface of each plate, and an opening in the center, and at least one of the diaphragms has the opening. Two vibrating plates having a concave portion having an outer diameter larger than the hole, and arranged inside the hole of the center pole and abutting on the periphery of the opening of the suspension so that the exciting unit and the vibrating plate are respectively provided in a predetermined manner. Between And a spacer formed by holding the said two sheets of diaphragm the two spacers connecting member for connecting the suspension is made consisting comprise.

In addition, the electromagnetic driver of the present invention is such that the center pole is wound on the two disc-shaped plates integrated with the center pole having a hole in the center, and the two disc-shaped plates. Mounted excitation coils are arranged, and ring-shaped permanent magnets each having an outer shape smaller than the outer shape of the disc-shaped plate are arranged on the outer peripheral portion of the excitation coil, and the two plates are the ring. Two exciting parts formed by cutting along two parallel straight lines in contact with the outer peripheral part of the plate-shaped permanent magnet, and the plates are fixed to each other via a fixing part between the outer peripheral bottom faces of the plates. A suspension, two diaphragms having an opening in the center, and at least one diaphragm having a recess having an outer diameter larger than the opening, and arranged inside the hole of the center pole, And the above suspension A spacer that is in contact with the periphery of the opening of the probe and holds the exciting part and the vibrating plate at predetermined intervals, respectively, and a connecting member that connects the two vibrating plates, the two spacers, and the suspension. , Is provided.

Description of Embodiments FIG. 5 is a sectional view of an electromagnetic driver according to a first embodiment of the present invention. In each of the following figures, the same members as those in the conventional example shown in FIG. 2 are designated by the same reference numerals.
In FIG. 5, 15a and 15b are center poles having a hole in the center thereof and are integrally or mechanically connected to the plates 16a and 16b. 7a, 7b is an exciting coil wound on the center pole 15a, 15b, 8a, 8b is a ring-shaped permanent magnet arranged on the plate 16a, 16b, the outer diameter of the plate 16a, 16b, the permanent magnet 8a, It has a larger diameter than the outer diameter of 8b, and two exciting portions are formed by these, and they are arranged facing each other on the surfaces of the plates 16a and 16b. The diaphragms 9a and 9b are provided with a recess in the center, and are fixed to the periphery of the central opening of the suspension 17 with screws 12 and nuts 13 via cylindrical spacers 10a and 10b. Furthermore, the outer peripheral portion of the suspension 17 is fixed via ring-shaped spacers 18a and 18b provided on the outer peripheral bottom surfaces of the plates 16a and 16b, and the vibrating plates 9a and 9b have a predetermined magnetic gap between the two exciting portions. Is arranged to hold.

The operation of the electromagnetic driver of this embodiment constructed as above will be described below.

Since the two vibrating plates 9a and 9b are arranged with the same magnetic gap between them and the respective exciting parts, the permanent magnets 8a and 8b are arranged.
The static attraction force due to is canceled out and becomes zero, and in the steady state where there is no electric signal, the stress acting on the suspension 17 is completely eliminated. The exciting coils 7a and 7b are directly connected or connected in parallel to apply an electric signal. When an electric signal is applied, the diaphragms 9a and 9b move up and down, but when one magnetic gap becomes narrower, the other becomes wider, so that the driving force can be made symmetrical.

The above is the same as the operation of the conventional static attraction force balance type electromagnetic driver described in FIG. The difference from the conventional example is that the outer diameters of the plates 16a and 16b are ring-shaped permanent magnets 8a and 8b.
The outer diameter of the suspension 17 provided on the outer peripheral bottom surfaces of the plates 16a and 16b is set to be larger than the outer diameter of the permanent magnet 8.
The outer diameters of a and 8b are set to be larger, and the stiffness of the suspension 17 is being reduced. As a result, regardless of the outer diameters of the permanent magnets 8a and 8b, the resonance frequency of the electromagnetic driver is lowered, and if the front surface of the diaphragm 9a is fixed to the front panel 3, a significantly lower bass band than the conventional one can be achieved. Can be expanded.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a sectional view of an electromagnetic driver showing a second embodiment of the present invention.

6, the same members as those in FIG. 5 are designated by the same reference numerals. The difference from the configuration of FIG. 5 is that the ring-shaped suspensions 18a and 18b used to fix the outer periphery of the suspension 17 are integrated with the plates 16a and 16b, and the contact surface with the suspension 17 is flat, and the center pole 15a. , 15
The point is that plates 19a and 19b that form a fixing portion in a tapered shape are provided toward the hole provided in b. As a result, the number of parts and the assembly method can be reduced, and the cost can be reduced.

The third embodiment of the present invention will be described below. FIG. 7 (a) is a partially cutaway top view of the electromagnetic driver in the third embodiment of the present invention, and the notched portion is shown in FIG. 7 (b).
The III-IV line cross section is shown. FIG. 7 (b) is a sectional view taken along line I-II of FIG. 7 (a).

7, the same members as those in FIG. 5 are designated by the same reference numerals. The structure shown in FIG. 5 has two sides of the plates 20a and 20b facing each other, and in FIG.
It is a point cut in parallel according to the outer diameter of a and 8b. further,
The suspension 21 has been changed from the three-sided support shown in FIG. 5 to the two-sided support so that it does not protrude from the two-side cut plates 20a, 20b. Also, the suspension 21
The spacers 22a and 22b used for fixing the outer periphery of
It has a shape that matches the outer shapes of the plates 20a and 20b.

With the above configuration, in order to reduce the stiffness of the suspension 21, even if the outer shape is large, that is, even if the outer shapes of the plates 20a and 20b are large, the vertical dimension of the electromagnetic driver is the same as the outer dimension of the permanent magnets 8a and 8b. Can be the same. Therefore, when it is installed on the front panel 3 of the television, the visible range of the image can be expanded without hiding a part of the image of the cathode ray tube 2.

EFFECTS OF THE INVENTION As described above, according to the electromagnetic driver of the present invention, the stiffness of the suspension supporting the diaphragm can be arbitrarily controlled despite the small permanent magnet.
The resonance frequency can be easily lowered as compared with the conventional electromagnetic driver, and the low frequency limit frequency of the sound reproduced from the housing of the attached device can be expanded. Further, since the plate widths of the two opposite sides can be made equal to the outer diameter of the permanent magnet, it is particularly effective for low-pitched sound reproduction of a device in which it is difficult to secure a space because there are restrictions in the vertical and horizontal directions. The effect is great.

[Brief description of drawings]

FIG. 1 is a perspective view of a television set in which a conventional electromagnetic driver is attached to a front panel, FIGS. 2 (a) and 2 (b) are structural cross-sectional views of the conventional electromagnetic driver, and FIG. 3 is the same magnetic gap. FIG. 4 is a static attraction force characteristic diagram, FIG. 4 is a magnetic gap-driving force characteristic diagram, FIG. 5 is a sectional view of an electromagnetic driver in a first embodiment of the present invention, and FIG. 6 is a second embodiment. FIG. 7 is a sectional view of the electromagnetic driver in FIGS. 7A and 7B, and FIGS. 7A and 7B are structural sectional views of the electromagnetic driver in the third embodiment. 8a, 8b …… Permanent magnet, 9a, 9b …… Vibrator, 16a, 16b, 19a, 19
b, 20a, 20b …… plate, 17,21 …… suspension.

Claims (6)

[Claims] 1. A disk-shaped two plate having a center pole having a hole at the center integrally formed therein, and an exciting coil wound around the center pole on the two disk-shaped plates. And two ring-shaped permanent magnets, each of which has a ring-shaped permanent magnet having an outer shape smaller than the outer shape of the disk-shaped plate, is disposed on the outer peripheral portion of the excitation coil, and the outer peripheral bottom surface of each plate. A suspension formed by fixing the plates to each other with a fixing portion interposed therebetween, and two suspension plates having an opening at the center and a concave portion having an outer diameter larger than the opening on at least one diaphragm. A vibrating plate; a spacer disposed inside the hole of the center pole, abutting on the periphery of the opening of the suspension, and holding the exciting unit and the vibrating plate at predetermined intervals, respectively; Diaphragm and above An electromagnetic driver comprising: two spacers and a connecting member that connects the suspension. 2. The electromagnetic driver according to claim 1, wherein the vibrating plate is arranged so that the magnetic gaps of the respective excitation parts have the same width. 3. The electromagnetic driver according to claim 1, wherein a ring-shaped spacer is used as the fixing portion. 4. The electromagnetic wave according to claim 1, wherein a plate having a flat contact surface with the outer peripheral portion of the suspension and a tapered portion between the outer peripheral portion and the hole of the center pole is used as the fixing portion. Type driver. 5. The electromagnetic driver according to claim 1, wherein a screw and a nut that can be housed in the recess are used as the connecting member. 6. A disk-shaped two plate in which a center pole having a hole in the center is integrated, and an exciting coil wound around the center pole on the disk-shaped two plates. And a ring-shaped permanent magnet having an outer shape smaller than the outer shape of the disc-shaped plate is arranged on the outer peripheral portion of the excitation coil, and the two plates are formed of the ring-shaped permanent magnet. Two exciting parts, which are cut along two parallel straight lines in contact with the outer peripheral part, a suspension formed by fixing the plates to each other via a fixing part between the outer peripheral bottom surfaces of the plates, Two diaphragms each having an opening and at least one of the diaphragms having a recess having an outer diameter larger than that of the opening; and an opening of the suspension which is arranged inside the hole of the center pole. Abut around the hole An electromagnetic driver comprising: a spacer that holds the exciting unit and the diaphragm at predetermined intervals; and a connecting member that connects the two diaphragms, the two spacers, and the suspension. .