JPH06197398A - Thin profile speaker - Google Patents

Abstract

PURPOSE:To provide the thin profile speaker in which a diaphragm is not in contact with a top plate comprising a magnetic circuit during its vibration. CONSTITUTION:The speaker has a magnetic circuit comprising a bottom plate 2 in which a bottom surface 2a is made to a flat plate and an upper surface 2b is formed to be a conical surface whose thickness is made thinner from a base end part of a center pole 1 established upright on the center toward an outer circumferential direction, a magnet 3 whose bottom surface 3a is formed to be conical in close contact with a conical surface of the bottom plate 2 and in which the upper surface part 3b is made in parallel with the bottom part 3a of a conical shape whose thickness is kept constant, a conical shaped bottom part 4a in close contact with the upper surface part 3b of the magnet 3 and a top plate 4 having an upper surface 4b whose thickness is made thinner from the center toward the outer circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin speaker mounted on a door of an automobile or the like, and more particularly to a so-called inverted cone speaker in which a magnetic circuit is located in front of a diaphragm.

[0002]

2. Description of the Related Art A thin speaker installed in a place having a small volume such as a door of an automobile is disclosed in Japanese Utility Model Publication No. Sho 49-2802.
No. 2, Japanese Utility Model Publication No. 52-2428, and Japanese Patent Laid-Open No.
The one described in -1111597 has been proposed and put into practical use. The speakers described in these publications are all
A bottom plate of a bottom plate having a center pole is fixed on a grill on which a speaker frame or a speaker is installed, a ring-shaped magnet is arranged on the bottom plate, and a ring-shaped top plate is arranged on the magnet. The voice coil is installed in the gap formed between the center pole and the top plate, the cone base of the cone-type diaphragm is connected to the tip of the voice coil, and the magnetic circuit is provided on the front surface of the diaphragm. It is configured to be located.

[0003]

The above-mentioned known inverted cone type speaker is, for example, as shown in FIG. 1 of Japanese Utility Model Publication No. 52-2428, in which the diaphragm constitutes an upper surface of the upper plate which constitutes a magnetic circuit. Since it is installed very close to the outer peripheral edge, when the diaphragm is driven, a part of the diaphragm comes into contact with the outer peripheral edge of the upper surface of the upper plate, generating abnormal noise, or in the worst case, the diaphragm. Had some problems such as the possibility that some of the items would be damaged. Therefore, in order to prevent contact between the diaphragm and the upper plate, it is necessary to provide a distance such that the diaphragm does not contact the magnetic circuit.Therefore, the magnetic circuit uses an inner magnet type or outer magnet type magnet with a small outer diameter. I had no choice but to obtain a sufficient magnetic flux.

In view of the above circumstances, the present invention provides a thin speaker in which the diaphragm and the magnetic circuit do not come into contact with each other even when a magnetic circuit having a large outer diameter is used.

[0005]

In order to achieve the above object, the thin speaker of the present invention has a flat bottom surface,
The top surface has a bottom plate that is a conical surface whose thickness decreases from the base end portion of the center pole that is erected in the center toward the outer peripheral direction, and the bottom surface portion has a conical shape that is in close contact with the conical surface of the bottom plate, It has a magnet whose top surface is parallel to the conical bottom surface and maintains a constant thickness, and a conical bottom surface that is in close contact with the top surface of the magnet. The magnetic circuit is composed of the top plate and the voice coil, which have a conical surface with a reduced thickness, and the cone-type diaphragm is provided so that the magnetic circuit is located in front of the diaphragm.

If the thickness of the outer peripheral portion of each of the bottom plate and the top plate constituting the above magnetic circuit is equal to or larger than the thickness inversely proportional to the radius from the center portion, no leakage magnetic flux is generated and the magnetic flux No unevenness occurs.

Further, the magnets that make up the magnetic circuit are
The ferrite magnet may be either an alnico magnet or a rare earth cobalt magnet, but for a small and thin speaker, it is preferable to use a rare earth cobalt magnet having a large maximum energy product.

[0008]

In the thin speaker of the present invention, the bottom plate, the magnet, and the top plate which form the magnetic circuit have a special shape, and the whole structure becomes a truncated cone shape at the time of assembly. Even if it vibrates greatly, there is no possibility that the diaphragm will come into contact with the magnetic circuit, and the speaker can be made thinner than the cylindrical magnetic circuit when assembled.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the thin speaker of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a thin speaker of the present invention. A magnetic circuit has a bottom plate 2 made of a magnetic material having a center pole 1 in the center, and a magnet mounted on the bottom plate 2. 3 and a top plate 4 and a voice coil 5 placed on the magnet 3.

The bottom plate 2 fixed on the bottom surface of the frame 8 has a flat bottom surface 2a and an upper surface 2 thereof.
b is a conical surface whose thickness decreases from the base end portion of the center pole 1 toward the outer peripheral direction. The magnet 3 provided on the bottom plate 2 is made of samarium-cobalt, and the bottom surface portion 3a has a conical shape in close contact with the top surface portion 2b of the bottom plate 2, and the top surface portion 3b has the bottom surface portion 3a. It is parallel to and has a constant thickness.

The top plate 4 provided on the magnet 3 has a bottom surface 4a formed in a conical shape in close contact with the top surface 3b of the magnet 3 and has a thickness from the center of the top surface 4b toward the outer peripheral direction. The conical upper surface 4b is thinner than the bottom plate 2 and the top plate 4 in that the conical upper surface 4b is steeper than the top plate 2b of the bottom plate 2.
Has a thickness at the outer peripheral edge thereof that is inversely proportional to the radius from the center of the center pole 1.

In the figure, 5 is a voice coil held in a magnetic gap formed between the inner peripheral edge of the top plate 4 and the outer peripheral surface of the center pole 1, 6 is a cone type diaphragm, and 7 is a diaphragm. Indicates a dust cap.

In the magnetic circuit having such a structure, at the time of assembly, the bottom plate 2 is fixed on the bottom surface of the frame 8, then the ring-shaped magnet 3 is provided on the bottom plate 2, and then a gauge or the like is used. Top plate 4
Is placed on the magnet 3, the coil portion of the voice coil 5 is held in a magnetic gap formed between the top plate 4 and the center pole 1, and the tip of the voice coil 5 is formed into a cone shape. Speaker S installed in the center
It is what constitutes.

[0014]

According to the thin speaker of the present invention, the bottom surface of the magnetic circuit is a flat surface, and the top surface is a conical surface whose thickness is reduced from the base end of the center pole erected at the center to the outer peripheral direction. The bottom plate has a conical shape in which the bottom surface is in close contact with the conical surface of the bottom plate, and the top surface is in parallel with the bottom surface of the conical shape and has a constant thickness. It has a conical bottom surface and a top plate whose top surface is a conical surface whose thickness decreases from the center to the outer peripheral direction. When the speaker is assembled, the top edge of the outer peripheral edge of the top plate is below the top edge of the inner peripheral surface, so even if a magnet with a large outer diameter is used, It is possible to maintain sufficient spacing between the diaphragm. Therefore, compared to the conventional cylindrical magnetic circuit, the speaker can be made thinner, and the diaphragm does not come into contact with the outer peripheral edge of the top plate, which causes abnormal noise and damage to the diaphragm. There is no. In addition, since the shape of the magnet can be set to a required size, sufficient magnetic flux can be obtained even if the magnet is thin, and it is possible to provide a high-performance thin speaker, and the configuration is extremely simple. In addition, it has a great practical advantage such that the increase in cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part showing an example of a thin speaker of the present invention.

[Explanation of symbols]

 1 Center pole 2 Bottom plate 3 Magnet 4 Top plate

Claims (2)

[Claims] 1. A bottom plate having a flat bottom surface, and a top plate having a conical surface whose thickness decreases from the base end portion of a center pole erected in the center toward the outer peripheral direction, and the bottom surface portion. With a conical shape in close contact with the conical surface of the bottom plate, a magnet having a constant thickness with the upper surface portion parallel to the conical bottom surface portion, and a conical bottom surface portion in close contact with the upper surface portion of the magnet, A magnetic circuit is formed by a top plate and a voice coil whose top surface is a conical surface whose thickness decreases from the center to the outer peripheral direction, and the cone-type diaphragm is positioned so that the magnetic circuit is located in front of the diaphragm. A thin speaker characterized by being provided with. 2. The thin speaker according to claim 1, wherein each of the bottom plate and the top plate has a thickness of an outer peripheral portion equal to or larger than a thickness inversely proportional to a radius from a central portion.