JPH0570097U - Inner magnet type magnetic circuit - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents oxidation and chipping of the magnet, and positions the yoke, poles, and magnet accurately. [Structure] Engineering plastic in a cylindrical shape
Further, the cylindrical body 4 is obtained by molding so that the inner diameter of the open end is the same size as the diameter of the cylindrical magnet and the middle portion thereof is slightly smaller than the diameter of the cylindrical magnet. A cylindrical magnet 3 is press-fitted into the center of the cylindrical body, and a plate 1 having a groove-shaped annular recess 1a having the same diameter as the opening end of the cylindrical body, and a yoke 2 similarly having an annular recess 2a formed therein. Then, the open end of the cylindrical body is fitted to obtain the inner magnet type magnetic circuit according to the present invention.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a magnetic circuit used in an electroacoustic transducer such as a speaker, and more particularly to an inner magnet type magnetic circuit.

[0002]

[Prior Art]

 As is well known, an inner magnet type magnetic circuit used in a conventional speaker or the like is composed of a magnet 03, a plate 01, and a yoke 02 as shown in FIG. 3, and is assembled by using an adhesive. .

[0003]

[Problems to be solved by the device]

 As is well known, in such a magnetic circuit, the gap between the magnetic gap formed between the plate and the yoke is made uniform, and the magnetic flux density in the magnetic gap is made uniform. Ideally, however, in the assembly process, since the adhesive is used for assembly, there is a problem that the magnetic gap is misaligned when the adhesive is dried and the magnetic gap is not uniformly formed. In order to prevent this, a method of fitting a magnetic gap gauge into the magnetic gap in the adhesive drying process and then removing this magnetic gap gauge after the adhesive has been dried is commonly used. Has the following drawbacks. (1) A magnetic gap gauge extraction process is required after the adhesive is dried. (2) Since the magnetic gap gauge is provided with a small amount of play so that the magnetic gap gauge can be easily inserted and removed, the accuracy is not sufficient and the magnetic gap has some variation. (3) Only the positioning of the yoke and the plate is performed, and accurate positioning of the entire magnetic circuit including the magnet is not possible. Therefore, the magnetic flux density in the magnetic gap tends to be uneven. (4) Due to the non-uniform magnetic gap spacing and the non-uniform magnetic flux density in the magnetic gap due to the displacement of the magnet, the driving force of the voice coil inserted in the magnetic gap becomes uneven, which adversely affects the reproduced sound. Exert.

In addition, as other drawbacks of the conventional inner magnet type magnetic circuit, there are deterioration of the performance of the magnet due to oxidation when a rare earth magnet is used, and a gap defect due to lack of the magnet or adhesion of rust.

Therefore, the present invention solves the drawbacks of the above-mentioned conventional example, prevents the magnet from being chipped or oxidized, and easily and accurately positions the magnet, the plate, and the yoke, and the gap of the magnetic gap and the magnetic flux density. It is an object of the present invention to provide a magnetic circuit for a speaker having a uniform structure.

[0006]

[Means for Solving the Problems]

 An inner magnet type magnetic circuit according to the present invention for achieving the above-mentioned object includes a cylindrical magnet 3, a cylindrical body 4 made of a non-magnetic material having an inner diameter substantially equal to the diameter of the cylindrical magnet 3, and the cylindrical magnet 3. A plate 1 in which an annular recess for fitting one opening end of the body 4 is formed, and a yoke in which an annular recess for fitting the other opening end of the tubular body 4 is formed. 2 and the cylindrical magnet 3 is arranged inside the cylindrical body 4, and one opening end of the cylindrical body 4 is formed in an annular recess formed in the plate 1 and the yoke 2. It is characterized by a structure in which the other open end is fitted.

Further, the inner diameter of the intermediate portion of the tubular body 4 is smaller than the inner diameter of the open end of the tubular body 4 and the diameter of the columnar magnet 3.

The cylindrical body 4 is made of a non-magnetic and high conductivity material.

[0009]

[Action]

 In the inner magnet type magnetic circuit having such a configuration, the side surface of the magnet is covered with the cylindrical body, and the upper and lower surfaces of the magnet are covered with the plate and the yoke.

Further, since the magnet is located inside the tubular body and the open end of the tubular body is fitted into the annular recess formed in the yoke and the plate, the magnet, the yoke and the plate can be accurately positioned. .

Next, when the inner diameter of the intermediate portion of the cylindrical body is smaller than the inner diameter of the open end of the cylindrical body and the direct diameter of the cylindrical magnet, the cylindrical magnet is tightened when it is inserted into this cylindrical body. It becomes a tight fit, absorbs the dimensional tolerance of the cylindrical magnet, and improves the adhesion between the cylindrical magnet and the cylindrical body.

Further, when the tubular body is made of a non-magnetic and high-conductivity material, the tubular body acts as a short ring, short-circuiting the eddy current due to the alternating magnetic field generated by the voice coil, and reducing the magnetic strain.

[0013]

【Example】

 An embodiment of the present invention will be described in detail with reference to FIGS. 1 is a sectional view of an inner magnet type magnetic circuit according to an embodiment of the present invention, FIG. 2 is a sectional view of a cylindrical body, 1 is a plate, 2 is a yoke, 3 is a magnet, 4 is a cylindrical body, and 1a and 2a are circles. It is an annular recess.

First, as a first embodiment, the engineering plastic is made cylindrical, and the inner diameter of the open end is the same size as the diameter of the cylindrical magnet 3, and the middle portion thereof is slightly smaller than the diameter of the cylindrical magnet 3. The cylindrical body 4 is obtained by molding so that. A cylindrical magnet 3 is press-fitted in the center of the cylindrical body, and a plate 1 having a groove-shaped annular recess 1a having the same diameter as the opening end of the cylindrical body and a yoke 2 similarly having an annular recess 2a formed therein. Then, the open end of the cylinder is fitted to obtain the inner magnet type magnetic circuit according to the present invention.

Next, as a second embodiment, an inner magnet type magnetic circuit according to the present application is obtained in the same manner as in the first embodiment by using aluminum, which is a non-magnetic material and has high conductivity, as the material of the cylindrical body 4. .

Although the internal magnet type magnetic circuit according to the present invention has been described above in detail based on an example considered to be typical, the embodiment of the present invention is not limited to the structure of the above-mentioned example. For example, the annular concave portion does not necessarily have to be a groove shape, may have a step shape, and the material of the support ring is not limited to engineering plastic or aluminum. The present invention can be appropriately modified and implemented as long as it has the constitutional requirements described in the range, exhibits the action of the present invention, and has the effects described below.

[0017]

【effect】

 The inner magnet type magnetic circuit according to the present invention has the following effects. (1) Since the plate and the yoke are connected by the tubular body and the magnet is placed inside the tubular body, the positions of the plate, the yoke and the magnet are inevitably and extremely accurately determined, and the magnetic gap distance is distributed over the entire circumference. The magnetic flux density in this magnetic gap is also uniform. As a result, the voice coil bobbin has a uniform driving force over the entire circumference, and the sound quality is good. (2) The magnet is chipped and oxidation is prevented, resulting in excellent reliability. (3) If a high-conductivity material is used for the cylindrical body, it also functions as a short ring, so that a magnetic circuit with less magnetic strain can be obtained. (4) The magnetic circuit is more firmly assembled. (5) Since the extraction process of the magnetic gap gauge is unnecessary, the manufacturing process is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inner magnet type magnetic circuit according to an embodiment.

FIG. 2 is a cross-sectional view of a cylindrical body of the embodiment.

FIG. 3 is a sectional view of a conventional inner magnet type magnetic circuit.

[Explanation of symbols]

 1 plate 2 yoke 3 cylindrical magnet 4 cylindrical body 1a, 2a annular recess

Claims (3)

[Scope of utility model registration request] 1. An inner magnet type magnetic circuit used for an electroacoustic transducer such as a speaker, wherein a cylindrical magnet (3) is used.
A cylindrical body (4) made of a non-magnetic material having an inner diameter substantially equal to the diameter of the cylindrical magnet (3), and an annular recess for fitting one open end of the cylindrical body (4). And a yoke (2) having an annular recess for fitting the other open end of the tubular body (4). The tubular body (4) ), The columnar magnet (3) is arranged inside, and one opening end and the other opening end of the tubular body (4) are provided in annular recesses formed in the plate (1) and the yoke (2). An inner magnet type magnetic circuit having a structure in which and are fitted. 2. The inner diameter of the middle portion of the tubular body (4) is smaller than the inner diameters of both open ends of the tubular body (4) and the diameter of the cylindrical magnet (3). Item 1. The inner magnet type magnetic circuit according to item 1. 3. The inner magnet type magnetic circuit according to claim 1, wherein the cylindrical body (4) is made of a non-magnetic and high conductivity material.