JP4801568B2 - Magnetic circuit for speaker and speaker - Google Patents

Description

  The present invention relates to a speaker magnetic circuit and a speaker.

  2. Description of the Related Art A speaker having a magnetic circuit in which a pair of flat plates are arranged in the longitudinal direction and a magnetic gap is formed between the plates is known. As an example, there is a ribbon type speaker described in Patent Document 1 below.

  FIG. 1A is an explanatory diagram showing a configuration example of a ribbon speaker. A yoke J3 is provided between one magnetic pole of the permanent magnets J1 and J2, and a pair of plates J4 and J5 are provided on the other magnetic pole to form a magnetic circuit J6. The pair of plates J4 and J5 are arranged so that the side surfaces thereof face each other, and a magnetic gap J7 is formed between the side surfaces.

  A ribbon diaphragm J8 is provided in the magnetic field of the magnetic gap J7. The ribbon diaphragm J8 is entirely formed in a strip shape or a ribbon shape by a thin conductive plate, the width direction of which coincides with the width direction of the magnetic gap J7, and electrodes J8a, J8b at two longitudinal ends. The signal source J9 is connected to the electrodes J8a and J8b, and the audio current I is supplied to the ribbon diaphragm J8.

  According to this, the sound current I flows in the longitudinal direction on the ribbon diaphragm J8, and the electromagnetic force along the thickness direction of the plates J4 and J5 acts by the magnetic field in the width direction of the magnetic gap J7. As a result, the ribbon diaphragm J8 vibrates in the thickness direction.

  The characteristic of this ribbon type speaker is that the vibrating body is simplified (the vibrating body is provided with a voice coil, a voice coil bobbin, and a diaphragm in a general speaker, but in a ribbon type speaker, an audio current is passed through the ribbon diaphragm itself), and the ribbon Since a driving force acts directly on the entire diaphragm J8, a lightweight vibrating body can be driven efficiently. In addition, since the vibrating body itself plays the role of a voice coil, the length of the vibrating body (voice coil) in the vibration direction is small, so that the inductance of the vibrating body (voice coil) can be suppressed from increasing in the high sound range. . Therefore, it is possible to increase the sensitivity, speed up the response to the audio signal, and reproduce to a very high frequency.

Japanese Patent Laid-Open No. 10-178699

  Not only the ribbon type speaker described above, but a magnetic circuit in which a pair of flat plates are arranged in the longitudinal direction and a magnetic gap is formed between the plates, a magnetic gap having the same width is formed along the longitudinal direction. Since the vibrating body is arranged in the magnetic gap, it is necessary to form a uniform magnetic field along the longitudinal direction of the magnetic gap in order to apply a uniform driving force to the entire vibrating body. become.

  However, near the end of the plate extending in the longitudinal direction, an outward magnetic field is formed, so the magnetic flux density is inevitably different from the central part of the plate, and a uniform magnetic field is formed throughout the magnetic gap. I can't do it.

  FIG. 1B is an explanatory diagram schematically showing the magnetic flux density in the magnetic gap of the conventional ribbon type speaker. When the plates J4 and J5 having a constant thickness in the longitudinal direction are used, a magnetic flux g1 that wraps outward is generated at both ends of the plates J4 and J5, so that two central portions J7a of the magnetic gap J7 are formed by the magnetic flux g1. The magnetic flux density is smaller than that of the end J7b.

  Here, since the driving force F (electromagnetic force) acting on the ribbon diaphragm is expressed by the following equation (1), assuming that the length of the diaphragm and the magnitude of the audio current are constant, the magnitude of the magnetic flux density is large. As a result, the driving force of the diaphragm changes.

  Further, the driving force F of the diaphragm can be correlated with the sound pressure SPL (dB) of the speaker, and the relationship can be expressed by the following equations (2a) to (2d).

  As is clear from the equation (2d), the loudspeaker sound pressure P increases as the driving force F of the loudspeaker increases. As a result, when a magnetic circuit formed of a plate with a constant thickness is used, the magnetic flux escapes outward and the magnetic flux density is different between the end and the center of the plate. This causes a problem that the magnetic flux density becomes small at the portion, and a uniform sound pressure SPL cannot be obtained, and the sound quality of the speaker is deteriorated.

  This invention makes it an example of a subject to cope with such a problem. That is, in a magnetic circuit in which a pair of flat plates are arranged in the longitudinal direction and a magnetic gap is formed between the plates, a uniform magnetic field is formed along the longitudinal direction of the magnetic gap. It is an object of the present invention that a uniform sound pressure can be obtained in a speaker using the above.

  In order to achieve such an object, the present invention comprises at least the configurations according to the following independent claims.

  [Claim 1] A pair of plate-like plates that are long in one direction are provided, the plates are arranged along the longitudinal direction so that the side surfaces thereof are opposed to each other, and a magnetic gap is formed between the side surfaces. Has two end portions and a central portion in the longitudinal direction, and the thickness of the central portion is smaller than the thickness of the end portion.

  [Claim 4] A pair of flat plates that are long in one direction are provided, the plates are arranged along the longitudinal direction so that the side surfaces thereof are opposed to each other, and a magnetic gap is formed between the side surfaces. A vibrating body is disposed along the longitudinal direction of the plate between the gaps and vibrates in the thickness direction of the plate by being supplied with an audio current along the longitudinal direction of the plate. A speaker comprising two ends and a center in a direction, wherein the thickness of the center is smaller than the thickness of the end.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is an explanatory view for explaining a speaker magnetic circuit according to an embodiment of the present invention (FIG. 2A is a plan view, FIG. 2B is an XX cross-sectional view, and FIG. YY sectional view).

A magnetic circuit 10 according to an embodiment of the present invention includes a pair of flat plates 11 and 12 that are long in one direction, and are arranged along the longitudinal direction so that the side surfaces of the plates 11 and 12 face each other. The magnetic gap 10G is formed. The plates 11 and 12 have an end b and a center a in the longitudinal direction, and the thickness t ₁ of the center a is smaller than the thickness t ₂ of the end b. In the illustrated embodiment, the magnetic gap 10G includes a pair of magnets 13 and 14 disposed along the longitudinal direction of the plates 11 and 12, and a single yoke 15, respectively. By sandwiching the magnets 13 and 14, the magnetic field from one side surface of the plates 11 and 12 toward the other side surface is formed. The magnets 13 and 14 include magnetic poles magnetized in the thickness direction of the plates 11 and 12, and the magnetic poles are arranged in directions opposite to each other.

According to the magnetic circuit 10 according to such an embodiment, the magnetic flux density escaping from the end b of the plates 11 and 12 to the outside reduces the magnetic flux density of the magnetic gap 10G at the central portion a of the plates 11 and 12. In order to prevent this, the thickness t ₁ of the side surfaces 11a and 12a of the plates 11 and 12 facing the magnetic gap 10G at the central portion a is made smaller than the thickness t ₂ of the side surfaces 11b and 12b at both ends, Thereby, the magnetic flux density in the longitudinal direction of the magnetic gap 10G is made uniform.

  By using such a magnetic circuit 10, it becomes possible to apply a uniform driving force to a conductor through which an audio current flows along the longitudinal direction of the magnetic gap 10G, and it is driven by this conductor. The sound pressure of the vibrating body can be made uniform along the longitudinal direction, and a high-quality speaker can be obtained.

  FIG. 3 is an explanatory view for explaining a speaker according to an embodiment of the present invention (FIG. 3 (a) is a perspective view showing the overall configuration, and FIG. 3 (b) is an XX cross-sectional view thereof). . Here, a ribbon speaker is shown as an example, but the present invention is not limited to this. For example, a voice coil may be disposed along the longitudinal direction of the magnetic gap, and a part of the vibrator may be connected to a voice coil bobbin around which the voice coil is wound.

  The speaker 20 includes flat plates 21 and 22 that are long in one direction, are arranged along the longitudinal direction so that the side surfaces of the plates 21 and 22 face each other, and a magnetic gap 20G is formed between the side surfaces. . In addition, a vibrating body 26 that vibrates in the thickness direction of the plates 21 and 22 when an audio current is supplied along the longitudinal direction of the plates 21 and 22 is provided in the magnetic gap 20G. In the illustrated example, the vibrating body 26 is a conductive ribbon-like member, and terminal portions 26 </ b> A and 26 </ b> B that supply an audio current are formed at two ends of the vibrating body 26. The vibrating body 26 is supported by the vibrating body support portions 27A and 27B at both ends in the longitudinal direction, and is disposed in the magnetic gap 20G.

  And in this speaker 20, like the magnetic circuit 10 mentioned above, the thickness of the center part a of the plates 21 and 22 which form the magnetic gap 20G is formed small compared with the thickness of the edge part b. . Again, the magnetic gap 20G includes a pair of magnets 23 and 24 arranged along the longitudinal direction of the plates 21 and 22 and a single yoke 25. The magnets 23 are formed by the plates 21 and 22 and the yoke 25, respectively. , 24 is sandwiched, a magnetic field is formed from one side surface of the plates 21 and 22 toward the other side surface.

  In the illustrated example, in the central portion a of the plates 21 and 22, tapered surfaces 21a and 22a from the outside toward the magnetic gap 20G are formed on the upper surface thereof. In the width direction of the plates 21 and 22, the central portion a is The thickness on the magnetic gap side is small and the thickness on the outside is large. That is, the thickness of the plates 21 and 22 at the central portion a gradually decreases from the outside toward the magnetic gap 20G side.

  According to the speaker 20 according to such an embodiment, since the side surfaces of the plates 21 and 22 facing the magnetic gap 20G are formed thin at the central portion a, the plate is similar to the magnetic circuit according to the above-described embodiment. It is possible to prevent the magnetic flux density of the magnetic gap 20G from decreasing at the central portion a by the magnetic flux escaping from the end b of the 21 and 22 and obtain a uniform magnetic flux density in the longitudinal direction of the magnetic gap 20G.

  FIG. 4 is an explanatory diagram for explaining the characteristics of the speaker according to the embodiment of the present invention, in which the magnetic flux density of the magnetic gap 20G in the embodiment of FIG. 3 is measured along the length direction of the plates 21 and 22. It is an example. As is clear from this measurement example, the magnetic circuit of the embodiment shown by the solid line has a uniform magnetic flux density along the longitudinal direction compared to the plate having the constant thickness shown by the broken line. I understand that.

  According to this, a uniform driving force can be applied to the vibrating body 26 in which the audio current flows along the longitudinal direction of the magnetic gap 20G, and the sound pressure level of the speaker 20 is adjusted along the longitudinal direction of the magnetic gap 20G. And a decrease in sound pressure at the central portion a can be suppressed.

  As described above, according to the magnetic circuit and the speaker according to the embodiment of the present invention, in a magnetic circuit in which a pair of flat plates are arranged in the longitudinal direction and a magnetic gap is formed between the plates, A uniform magnetic field can be formed along the longitudinal direction, and a decrease in sound pressure can be suppressed in a speaker using such a magnetic circuit.

It is explanatory drawing of a prior art. It is explanatory drawing explaining the magnetic circuit which concerns on embodiment of this invention. It is explanatory drawing explaining the speaker which concerns on embodiment of this invention. It is explanatory drawing explaining the characteristic of the speaker which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic circuit 20 Speaker 10G, 20G Magnetic gap 11, 12, 21, 22 Plate 13, 14, 23, 24 Magnet 15, 25 Yoke 26 Vibration body 26A, 26B Terminal part 27A, 27B Vibration body support part a (of plate) Center part b (end of plate)

Claims (7)

A pair of flat plates that are long in one direction,
The plate is disposed along the longitudinal direction so that the side faces thereof, and a magnetic gap is formed between the side faces,
The plate has two ends and a central portion in the longitudinal direction,
A magnetic circuit for a speaker, wherein a thickness of the central portion is smaller than a thickness of the end portion. In the width direction of the plate,
The magnetic circuit for a speaker according to claim 1, wherein the central portion has a thickness on the outer side larger than a thickness on the magnetic gap side.   The pair of magnets respectively disposed along the longitudinal direction of the plate and one yoke are provided, and the magnets are sandwiched between the plates and the yoke. Magnetic circuit for speakers. A pair of flat plates that are long in one direction,
The plate is disposed along the longitudinal direction so that the side faces thereof, and a magnetic gap is formed between the side faces,
A vibrator that is disposed along the longitudinal direction of the plate between the magnetic gaps and vibrates in the thickness direction of the plate by being supplied with an audio current along the longitudinal direction of the plate;
The plate has two ends and a central portion in the longitudinal direction,
A speaker characterized in that the thickness of the central portion is smaller than the thickness of the end portion. In the width direction of the plate,
The speaker according to claim 4, wherein the central portion has a thickness on the outer side larger than a thickness on the magnetic gap side.   The pair of magnets respectively disposed along the longitudinal direction of the plate and one yoke are provided, and the magnets are sandwiched between the plates and the yokes. Speaker.   The speaker according to claim 4, wherein the vibrating body is a conductive ribbon-like member, and a terminal portion that supplies an audio current is formed at an end of the vibrating body.

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