JPH0256200A - Speaker - Google Patents

Abstract

PURPOSE:To prevent the generation of a leakage current by forming a diaphragm in order to lower the electric resistance of a conductive part in the diaphragm than the electric resistance of a vibration part. CONSTITUTION:An integral drawing with a press is executed for a cylindric body 16 as the member for formation of a diaphragm 2 to form the diaphragm 2. In this case, a vibration part 15 is thinly drawn to a necessary and minimum thickness and a conductive part 8 is thick drawn. Consequently, the entire part of the diaphragm 2 can be lightened and the sensitivity of a speaker 1 can be improved. Since the cross sectional area of the conductive part 8 is made large and the cross sectional area of the vibration part 15 is made small, the resistance of the conductive part 8 is relatively decreased and the resistance of the vibration part 15 is relatively increased. Thus, further more dielectric current flows through the conductive part 8 and the generation of the leakage current can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to loudspeakers, particularly inductive loudspeakers.

[Summary of the invention]

This invention is a speaker in which the diaphragm is formed so that the electrical resistance of the conductive part is lower than the electrical resistance of the vibrating part, thereby making it possible to prevent the occurrence of leakage current flowing to the vibrating part. It is.

[Conventional technology]

In conventional electrodynamic speakers, driving force is obtained by passing an audio signal current through a voice coil in a DC magnetic field.

This audio signal current is normally supplied to the voice coil from the outside through a lead wire fixed to a paper cone serving as a diaphragm.

[Problem to be solved by the invention]

However, since conventional electrodynamic speakers are equipped with lead wires, they have the disadvantage that the lead wires are easily cut due to the reciprocating movement of the diaphragm. On the other hand, even if the lead wire is not cut, the linearity of the reciprocating motion of the diaphragm is inhibited, which tends to cause sound distortion, and the lead wire itself resonates, producing abnormal noise. there were. Furthermore,
During manufacture, the lead wire had to be drawn out through a narrow gap in the speaker, positioned, and then glued and fixed, making assembly difficult.

Therefore, as a speaker to eliminate the various drawbacks mentioned above, an inductive type speaker with the lead wire removed was developed.
It is disclosed in Japanese Patent No. 27039. In the speaker disclosed in the above publication, the lead wire is removed and a drive coil is placed near the voice coil wound around the voice coil bobbin.

An audio signal current is supplied to this drive coil, and the audio signal is supplied from this drive coil to the voice coil by magnetic induction. That is, when an AC signal from an audio frequency power amplifier flows into the drive coil, the AC signal generates an AC magnetic flux from the drive coil corresponding to the input waveform, and this AC magnetic flux is closely connected to the voice coil located at a close distance. interlink. On the other hand, since the voice coil itself is short-circuited, a short-circuit current flows through the voice coil due to the above-mentioned alternating current magnetic flux. Since the voice coil is located within the magnetic field created by the pole piece and the surrounding magnetic poles, a force proportional to the product of the strength of the magnetic field and the short-circuit current acts on the voice coil. This force causes the paper cone to vibrate from the voice coil through the voice coil bobbin, and sound is emitted from the cone like a normal speaker.

In the technology disclosed in the above-mentioned publication, the lead wires are removed, so although various drawbacks caused by the lead wires are resolved, the following problems also occur. .

Since the voice coil is generally fixed to the voice coil bobbin with an adhesive, there is a drawback that the driving force generated in the voice coil is difficult to be directly transmitted to the cone.

Furthermore, the voice coil inevitably generates heat due to short-circuit current, but there is a drawback in that it is difficult to properly dissipate this heat.

In order to improve the sensitivity of the speaker, the gap (magnetic gap) between the coil bobbin and the drive coil is narrowed, and
It is required that the voice coil be wound many times within this gap. Therefore, the diameter of the metal wire used in the voice coil inevitably becomes smaller, and the heat capacity of the metal wire becomes smaller.

As a result, combined with the heat dissipation problem mentioned above,
The voice coil has the drawback of being easily disconnected due to heat generation, which limits the current capacity.

Furthermore, there is a drawback that the paper voice coil bobbin is carbonized due to the above-mentioned heat generation being repeated.

Therefore, an induction type speaker without a voice coil has been proposed in Japanese Utility Model Application Publication No. 105438/1983.

That is, in this speaker, a diaphragm having an annular conductive part is supported in a magnetic gap in a magnetic circuit so as to be able to vibrate freely with a damper, and a feeding coil is opposed to the conductive part which is electrically coupled to the conductive part by mutual induction. It is arranged as follows. and,
This speaker generates an induced current based on mutual induction in an annular conductive part formed in a part of the diaphragm, and causes this induced current to interact with a DC magnetic field at the position of the magnetic gap to excite the diaphragm. It is something that makes you

In the technique disclosed in the above-mentioned publication, not only the lead wire but also the voice coil is removed, so various drawbacks caused by the lead wire, voice coil, etc. are eliminated.

However, the above-mentioned diaphragm usually requires generating an induced current in the conductive part that is a part of the diaphragm.
It had to be made of metal.

If the diaphragm is made of metal, there is a problem in that the diaphragm becomes heavy, which reduces the sensitivity of the speaker.

In addition, since the conductive part of the diaphragm and the parts of the diaphragm other than the conductive part are not insulated at all, the induced current induced in the conductive part flows outside the conductive part and becomes a leakage current, causing an induced current. There was a problem in that the number decreased accordingly. Since this leakage current is not useful for driving the diaphragm, the force for driving the diaphragm is also weakened, resulting in a problem in that the sensitivity of the speaker is reduced.

Therefore, it has been desired to improve these problems.

Therefore, an object of the present invention is to provide a speaker that can reduce the weight of the diaphragm, prevent leakage current, and increase sensitivity.

[Means to solve the problem]

A speaker according to the present invention includes a diaphragm including a vibrating part and an annular conductive part, a power supply coil disposed to face the conductive part with a predetermined gap, and a magnetic circuit to which the power supply coil is attached, The diaphragm is characterized in that the diaphragm is formed so that the electrical resistance of the conductive part is lower than the electrical resistance of the vibrating part.

[Effect]

When an alternating current as an audio signal is passed through the power supply coil, alternating magnetic flux is generated. Since the annular conductive portion closely interlinks with the above-mentioned alternating current magnetic flux, induced currents of the same frequency are induced in the above-mentioned conductive portion due to a mutual induction phenomenon.

Since the electrical resistance of the conductive part is lower than the electrical resistance of the vibrating part, it becomes easier for induced current to flow in the conductive part, but it becomes more difficult for induced current to flow in the vibrating part.

As a result, more induced current flows through the conductive portion, and it is possible to prevent leakage current that is not useful for driving the diaphragm from occurring.

The above-mentioned induced current interacts with the DC magnetic field in the magnetic gap to excite the diaphragm, but since the leakage current is eliminated, the driving force of the diaphragm can be increased, driving the diaphragm more sharply. It is possible to improve the sensitivity of the speaker.

Furthermore, the entire diaphragm can be made lighter, and the sensitivity of the speaker can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a dome-shaped speaker as shown in FIGS. 1 to 7. Note that this explanation will be made in the following order.

(A) About the first embodiment (B) About the second embodiment (C) About the third embodiment (D) About the fourth embodiment (E) About the fifth embodiment (F) About the sixth embodiment (A ) First Embodiment FIG. 1 shows a first embodiment of the present invention. In the configuration shown in FIG. 1, the speaker 1 includes a diaphragm 2
, a damper 9, a primary power feeding coil 3, a plate 4,
Magnet 5, yoke plate 6, and pole piece 1
It is mainly composed of 1.

The dome-shaped diaphragm 2 includes a vibrating section 15 that is thin and formed in a hemispherical shape, and a conductive section 8 that is thick and annularly formed at the opening edge 7. The entire diaphragm 2 is made of a good conductor, such as a metal such as aluminum, beryllium, or magnesium.

The diaphragm 2 is supported by a damper 9 so as to be able to freely vibrate, with the conductive portion 8 located within the magnetic gap 10 .

The magnetic gap 10 described above is formed in an annular shape between the plate 4 and the pole piece 1 of the yoke plate 6.

The damper 9 has spring properties and is formed in an annular shape. The damper 9 has an inner circumferential side connected to the periphery of the conductive part 8 and an outer circumferential side fixed onto the plate 4.

The primary feeding coil 3 electrically couples the annular conductive portion 8 by mutual induction, and is disposed opposite to the conductive portion 8 with a predetermined gap therebetween. This primary feeding coil 3 is disposed to face a position corresponding to the outer circumference or a position corresponding to the inner circumference of the conductive portion 8 . 1 in the illustrated example
The secondary feeding coil 3 is fixed to one end surface 12 of the plate 4 so as to correspond to the outer periphery of the annular conductive portion 8 . Further, when the primary feeding coil 3 is provided at a position corresponding to the inner circumference of the conductive portion 8, it is fixed to the outer circumference 13 side of the pole piece 11. Note that the primary feeding coil 3 may be provided both at a position corresponding to the outer periphery or at a position corresponding to the inner periphery of the conductive portion 8.

The plate 4, magnet 5, yoke plate 6, and pole piece 11 constitute a magnetic circuit. That is,
As shown in FIG. 1, a magnet 5 is fixed to the outer periphery of the yoke plate 6, and the plate 4 is fixed to the outer periphery of the magnet 5. A magnetic circuit is formed along a path such as from the magnet 5 to the plate 4 and from the magnet 5 to the yoke plate 6 and the pole piece 11 across the magnetic gap 10.

Next, an example of the formation of this diaphragm 2 will be explained.

In this first embodiment, when forming the diaphragm 2, for the cylindrical body 16 as a member for forming the diaphragm 2,
Perform integral drawing with a press. In this case, the vibrating section 15 is thinned down to the necessary minimum thickness, and the conductive section 8 is thickened.

In this way, by thickening the conductive part 8 to increase the cross-sectional area of the conductive part 8, and by making the vibrating part 15 thinner to reduce the cross-sectional area of the vibrating part 15, on the one hand, the entire diaphragm 2 can be made lighter. On the other hand, the resistance of the conductive part 8 is lowered,
The resistance of the vibrating section 15 is increased.

Next, the operation of the speaker 1 will be explained.

When an alternating current as an audio signal is passed through the primary feeding coil 3, an alternating magnetic flux corresponding to the input waveform is generated. Since the annular conductive portion 8 closely interlinks with the above-mentioned alternating current magnetic flux, induced currents of the same frequency are induced in the conductive portion 8 due to mutual induction phenomenon. Since the conductive portion 8 is located within the magnetic gap 10, a force proportional to the product of the strength of the DC magnetic field in the magnetic gap 10 and the induced current acts on the conductive portion 8. That is, the induced current in the conductive portion 8 acts on the DC magnetic field within the magnetic gap 10 to directly drive the diaphragm 2 to radiate sound waves.

As described above, since the conductive part 8 is thick and the vibrating part 15 is formed as thin as necessary, the entire diaphragm 2 can be made lighter and the sensitivity of the speaker 1 can be improved. Further, since the cross-sectional area of the conductive part 8 is made large and the cross-sectional area of the vibrating part 15 is made small, the resistance of the conductive part 8 is relatively reduced, and the resistance of the vibrating part 15 is relatively increased. Therefore, more induced current flows through the conductive portion 8, and leakage current can be prevented from occurring.

By preventing leakage current from occurring, the driving force of the diaphragm 2 can be increased, the diaphragm 2 can be driven more sensitively, and the sensitivity of the speaker 1 can be improved.

(B) Second Embodiment This second embodiment differs from the first embodiment in the method of forming the diaphragm 2.

FIG. 2 shows an example of the formation of the diaphragm 2 in the second embodiment. The key point in forming this diaphragm 2 is to reduce only the thickness of the cylindrical body 16 in the range corresponding to the vibrating section 15 by cutting.

The outer circumferential surface 17 of the cylindrical body 16 having a thickness t16 as shown in FIG. 2A is cut to a minimum necessary thickness t15, leaving only the lower portion 18. As a result, the diaphragm 2 as shown in FIG. 2B is formed. That is, this diaphragm 2 is composed of a thin vibrating portion 15 that is cut from a thickness t16 to a thickness t15, and a thick conductive portion 8 that has a thickness t16 in an uncut state.

By the way, if the recess 25 is formed as shown by the dotted line in FIG.
The resistance value between 5 and 5 can be increased. By providing such a recess 25, the high cutoff frequency can be adjusted.

As described above, although the second embodiment shows an example in which the diaphragm 2 is formed by cutting, methods other than cutting, such as sputtering and oxidation treatment, are also possible. If the diaphragm 2 is made of aluminum, oxidation treatment, so-called alumite treatment, is particularly effective. In this case, by applying colored alumite treatment, for example, black, the design can be improved and the heat dissipation performance can also be improved.

Note that the other contents are the same as in the first embodiment, so redundant explanation will be omitted.

(C) Third Embodiment This third embodiment differs from the first embodiment in the method of forming the diaphragm 2.

FIG. 3 shows an example of the formation of the diaphragm 2 in the third embodiment. This will be explained below with reference to FIG.

The opening edge 30 of the cylindrical body 16, which is formed with the minimum necessary thickness, is folded back to form the annular conductive part 8. The diaphragm 2 is thus formed.

The means for forming the diaphragm 2 may be selected from a press or other suitable means.

Note that the other contents are the same as those in the first embodiment, and redundant explanation will be omitted.

(D) Fourth Embodiment This fourth embodiment differs from the first embodiment in the method of forming the diaphragm 2.

FIG. 4 shows an example of the formation of the diaphragm 2 in the fourth embodiment.

The main point of forming the diaphragm 2 in this fourth embodiment is that the thickness L8 of the conductive part 8 is changed by plating to the thickness t of the cylindrical body 16.
16.

The outer circumferential surface 17 of the cylindrical body 16 [thickness t16] is formed as thin as the necessary minimum thickness as shown in FIG. 4A.
Only the lower part 18 of the fourth
As shown in FIG. B, the diaphragm 2 is configured such that the plating portion 36 is formed thicker toward the outer periphery. That is, this diaphragm 2 is composed of a thin vibrating section 15 that is not plated and has a thickness of t15, and a thick conductive section 8 that has a plated section 36 and a thickness of t8.

Furthermore, FIG. 4C shows a plated portion 36 formed on the inner peripheral surface 35 of the cylindrical body 16, and the inner and outer peripheral surfaces 35.
17 shows a plated portion 36 formed thereon. Although not described in detail, in all of these, the plating portion 36 is formed by the same method as in the case of FIG. 4B.
This provides the desired functionality.

Although this fourth embodiment describes an example of plating processing, the present invention is not limited to plating processing, and may be performed by sputtering, for example.

Note that the other contents are the same as those in the first embodiment, and redundant explanation will be omitted.

(E) Regarding the fifth embodiment, this fifth embodiment differs from the first embodiment in the method of forming the diaphragm 2.

FIG. 5 shows an example of the formation of the diaphragm 2 in the fifth embodiment.

The key point in forming the diaphragm 2 in this fifth embodiment is to increase the thickness of the conductive portion 8 from the thickness t16 by fitting the conductive ring 40 into the opening edge 30 of the cylindrical body 16. .

As shown in FIG. 5A, the outer circumferential surface 17 of the lower portion 18 of the cylindrical body 16 (thickness 16) is formed as thin as possible, and is made of a material with good conductivity. A conductive ring 40 as shown in FIG. 5C is fitted in this way.The diaphragm 2 as shown in FIG.

Note that the other contents are the same as those in the first embodiment, and redundant explanation will be omitted.

(F) Sixth Embodiment This sixth embodiment differs from the first embodiment in the formation of the diaphragm 2.

FIG. 6 shows an example of the formation of the diaphragm 2 in the sixth embodiment.

The main point of forming the diaphragm 2 in this sixth embodiment is that in the vibrating part 15 of the diaphragm 2, which is formed thin, a large number of It has holes.

Note that the above-mentioned non-passing portion 45 is a portion within the range through which the DC magnetic field does not pass when the diaphragm 2 moves to the lowest position P [in the direction of arrow Do in FIG. 7] as shown in FIG.
means the lowest part.

In the example shown in FIG. 6A, a round hole 46, in the example shown in FIG. 6B, a horizontally elongated hole 47, and in the example shown in FIG. 6C, a vertically elongated hole 48.
are formed in the non-passing portion 45, respectively.

In this way, the holes 46 and 47 are formed in the part 45 through which the DC magnetic field does not pass.
．． By forming 48, the weight of the diaphragm 2 as a whole is reduced, and the cross-sectional area of the non-passing portion 45 through which current flows is reduced, increasing resistance and preventing leakage current from occurring.

Also, depending on the state of formation of the holes 46, 47, and 48,

Claims (1)

[Scope of Claims] A vibration plate comprising a vibrating part and an annular conductive part, a power supply coil disposed to face the conductive part with a predetermined gap, and a magnetic circuit to which the power supply coil is attached. A speaker characterized in that the diaphragm is formed such that the electrical resistance of the conductive part is lower than the electrical resistance of the vibrating part.