JPH066896A - Top plate manufacturing method - Google Patents

Abstract

PURPOSE:To obtain the top plate at low cost by forming a tapered part, which is conventionally formed by the cutting of a lathe, by an extruding process by pressing and an elliptic internal-diameter punching process when the magnetic gap formation part of the top plate is made thinner than the external-diameter part by forming the tapered part so as to improve the magnetic flux density of the magnetic gap in the constitution of the magnetic circuit for a speaker, specially, a tweeter. CONSTITUTION:The manufacture of the top plate of the magnetic circuit of the speaker which uses an elliptic voice coil consists of a punching process wherein a steel plate having prescribed thickness is used to form a disk 14 by external-diameter punching by pressing and the disk 14 is punched to an internal diameter 15 smaller than prescribed internal diameter size, a process forming the tapered part 17 by pressing and the punching process for an elliptic internal hole 18; and the top plate can easily be produced at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a top plate which constitutes a magnetic circuit of a speaker using an elliptical voice coil.

[0002]

2. Description of the Related Art In order to improve the magnetic flux density of a magnetic air gap in a speaker, particularly in the structure of a tweeter magnetic circuit,
The thickness of the magnetic gap forming portion of the top plate is set to be substantially equal to the winding width of the voice coil, and the taper portion is formed to be evenly thinner than the thickness of the outer diameter portion.

A conventional top plate manufacturing method and speaker will be described below. FIG. 3 shows a cross-sectional view of a speaker using a conventional circular voice coil.

This is a dome type tweeter in which a bottom plate 1 having a cylindrical center pole at the center, a ring-shaped magnet 2 and a top plate 4 having a taper portion 3 in an inner diameter are concentric. And the magnetic gap 5 is formed between the inner peripheral cross-section of the top plate 4 and the upper portion of the pole of the bottom plate 1. A frame 6 is bonded onto the top plate 4, and a voice coil 7 and a voice coil bobbin 8 wound in a magnetic width 5 having a winding width substantially equal to the thickness of the inner peripheral portion of the top plate 4 are provided on the upper portion thereof. It is fixed to the frame 6 so as to be held via the edge 9a of the outer peripheral portion of the bonded dome type diaphragm 9.

The operating principle will be described below. Magnetic air gap 5
When an electric input is applied, the voice coil 7 suspended in the center of the unit vibrates up and down according to Fleming's left-hand rule,
The dome-shaped diaphragm 9 joined to the voice coil bobbin 8 vibrates the air on the front surface to generate sound.

In the case of a tweeter, generally, the thickness of the inner diameter portion of the top plate 4 is set to be substantially equal to the winding width of the voice coil 7 so that the winding width of the voice coil 7 becomes smaller and the magnetic flux density in the magnetic gap 5 becomes higher. Has been done. On the other hand, the thickness of the outer diameter portion of the top plate 4 is set thick so that magnetic saturation does not occur even if the strong magnet 2 is used.

FIG. 4 shows the shape of the top plate in each step according to the conventional top plate manufacturing method. 4 (a) is a disc 10 having an outer diameter removed from a steel plate having a predetermined material thickness, and FIG. 4 (b) is a top plate having an inner hole 11 formed by punching the disc 10 into a predetermined inner diameter. 12, FIG. 4C shows that the peripheral portion of the upper surface of the inner hole 11 of the top plate 12 is cut into a taper shape to form a taper portion 13.
Is formed and processed into a predetermined thickness of the magnetic gap forming portion. In practice, a deburring process is added if necessary, and the final process is a plating process.

[0008]

As described above, the conventional method for manufacturing the top plate of the speaker using the circular voice coil uses the steel plate having a predetermined thickness to press the outer diameter and press the inner diameter. It is a process, a taper part cutting process by a lathe, a post-process such as deburring, and a plating process. Since there is a lathe cutting process, the number of steps is increased and the cost is increased. Further, it is very difficult to provide a uniform taper portion on the inner diameter of the top plate of the speaker using the elliptical voice coil.

The present invention solves the above-mentioned conventional problems. In a method of manufacturing a speaker top plate using an elliptical voice coil, a cutting process is omitted and a taper portion is formed on an elliptical inner diameter portion. A method of forming is provided.

[0010]

In order to solve this problem, a method of manufacturing a top plate according to the present invention uses a steel plate having a predetermined thickness, an outer diameter removing step by pressing, and a size larger than a predetermined elliptical dimension. It consists of an inner diameter removal process, a taper extrusion molding process using a press, and an elliptical inner diameter removal process.

[0011]

By configuring the manufacturing method of the top plate as described above, it is possible to realize the tapered portion, which was conventionally difficult to form by cutting, in the extrusion molding step by pressing in a short time.

[0012]

EXAMPLE An example of the present invention will be described below.

According to the method of manufacturing a top plate of the present invention, the thickness of the magnetic gap forming portion of the top plate is the outer diameter portion among the top plates forming the magnetic gap portion of the magnetic circuit of the speaker using the elliptical voice coil. Compared to the thickness of the above, regarding the top plate with the tapered portion formed to have a uniform thickness, a steel plate having a predetermined thickness is used to perform an outer diameter removing step by pressing, and a substantially inner diameter removal not larger than the predetermined elliptical dimension. Process, taper part extrusion process by press, elliptical inner diameter removal process, post process such as deburring,
It is composed of a plating process.

A description will be given below with reference to the drawings. FIG. 1 shows the shape of the top plate in each step according to the method for manufacturing the top plate of this embodiment. FIG. 1 (a) shows a disk 14 having an outer diameter removed from a steel plate having a predetermined material thickness, and FIG. 1 (b) shows the disk 14 having an inner diameter not larger than a predetermined elliptical size. 1C shows a top plate 16 having an inner hole 15 formed therein. FIG. 1C shows that the inner diameter portion of the top plate 16 has a tapered portion 17 formed around the inner hole 15 in a tapered portion extrusion molding process by a press. 1D shows a top plate 16 processed to have the thickness of the magnetic gap forming part. FIG. 1D shows a top plate 16 in which the inner hole 11 is punched out into a predetermined elliptical size to form an elliptical inner hole 18. Is shown. Actually, after this, a deburring process is added as needed, and the final process is the plating process.

As the extrusion die used in the above-mentioned taper portion extrusion forming step, one shown in FIG. 2 is used.
That is, an elliptic taper processing part 20 for forming an elliptical taper part 17 around the projection 19 has a cylindrical projection 19 that fits into the inner hole 15 having a diameter smaller than the inner hole 15. A spherical surface portion 21 is provided around the tapered portion 20, and a flat surface portion 22
The tapered portion 17 is formed on the top plate 16 by pressing with the extrusion die 23 provided with.

When the extrusion die 23 is pressed, a tapered portion 17 is formed around the inner hole 15 as shown in FIG. 1C. At this time, the taper of the top plate 16 is formed on the inner hole 15 side. The inner hole 15 becomes smaller because the portion forming the processed portion 20 is extruded. Finally, as shown in FIG. 1D, an elliptical inner hole 18 is formed to form a top plate 16.

The top plate 16 is arranged on a plate having a center pole having an elliptical cross section through a ring magnet, and a magnetic gap is formed between the center pole and the inner hole 18 of the top plate 16. Use a magnetic circuit.

With the above-described structure, the tapered portion 17 which has hitherto been unachievable by the cutting work by the lathe can be realized by the extrusion molding process by the press in a short time.

[0019]

As described above, according to the present invention, in the top plate forming the magnetic gap portion of the magnetic circuit of the speaker using the elliptical voice coil, the thickness of the magnetic gap forming portion of the top plate is the outer diameter portion. Regarding the top plate in which the tapered portion is formed to have a uniform thickness as compared with the thickness of, the manufacturing method thereof is performed by using a steel plate having a predetermined thickness.
It can be manufactured by the outer diameter cutting process using a press, a substantially inner diameter cutting process that is not larger than the specified elliptical dimension, the extrusion process of the tapered portion by a press, and the elliptical inner diameter cutting process. The taper part which was not present can be realized in a short time by an extrusion molding process by a press, and a low cost top plate can be realized.

[Brief description of drawings]

1A to 1D are perspective views showing a top plate in each step according to a method for manufacturing a top plate of an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of an extrusion molding die used for extrusion molding of the tapered portion.

FIG. 3 is a sectional view of a speaker using a conventional circular voice coil.

4A to 4C are perspective views showing a top plate in each step according to a conventional method for manufacturing a top plate.

[Explanation of symbols]

 14 disk 15 inner hole 16 top plate 17 taper portion 18 inner hole

Claims (1)

[Claims] 1. A step of forming a circular plate by punching an outer diameter by using a steel plate having a predetermined thickness, a step of punching an inner hole not larger than a predetermined elliptical dimension, and forming a taper portion by pressing by extrusion. And a step of forming an elliptical inner hole by punching.