JPS63261993A - Production of low leakage magnetic circuit - Google Patents

Abstract

PURPOSE:To easily pass magnetic flux and to set an operating point high by magnetizing a second magnetic circuit by inserting a second bottom plate having pole into the center hole of a shield cover and a plate at the time of separately magnetizing the first and the second magnetic circuits in an opposite direction. CONSTITUTION:After the first magnetic circuit consisting of the bottom plate 1, a magnet 6 and a top plate 2 and the second magnetic circuit having a magnet 8, the plate 10 and the shield cover 11 and the bottom plate 13 having the pole inserted into the center hole of the plate 10 and the cover 11 are separately magnetized, the second magnetic circuit is connected to the external periphery of the first magnetic circuit. The height of the pole of the bottom plate 13 is higher than the plate 10 and abuts against the lower surface of the plate 10. The bottom plate 13 is removed and a shielding plate cover 12 is connected. Since according to this construction, a magnetic flux (j) passing through a magnetic path consisting of the plate 10 and the bottom plate 13 and a magnetic flux (k) passing through the plate 10 from the side face of the cover 11 easily pass, the operating point of the second magnetic circuit can be improved in the vicinity of the operating point of the first magnetic circuit and a low leakage magnetic circuit can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a low-leakage magnetic circuit that significantly reduces leakage magnetic flux and utilizes magnets effectively.

2. Description of the Related Art Generally speaking, it is preferable that a speaker has a small leakage magnetic flux, but speakers for color television receivers are particularly desired to have a low leakage magnetic flux. In other words, in color television receivers, speakers are generally placed at the bottom or on the side of the cathode ray tube, but if a large leakage magnetic flux is generated from the speaker in such a configuration, the electron beam will focus on a single point on the fluorescent surface of the cathode ray tube. This results in problems such as color shift due to lack of concentration.

Therefore, many efforts have been made to reduce leakage magnetic flux, and magnetic circuits having the configurations described below have now been put into practical use. A conventional low leakage magnetic circuit will be described below with reference to the drawings.

Conventionally, this type of low leakage magnetic circuit has had a configuration as shown in FIG. In FIG. 6, 1 is a bottom plate having a pole part, 2 is an upper plate, a field part is formed by an annular magnet 3 provided between the two, and a voice is formed by the bottom plate 1 and the upper plate 2. A main magnetic flux & is caused to flow through a magnetic gap 6 for inserting a coil, and by covering this magnetic circuit with a shield cover 4, the magnetic flux bl leaking to the outside is reduced.

However, this type of magnetic circuit cannot sufficiently reduce the leakage magnetic flux, and if the thickness of the shield cover 4 is made thicker in order to reduce the leakage magnetic flux, the main flow to the magnetic gap 5 forming the magnetic circuit is There was a problem that the magnetic flux a decreased.

Therefore, in recent years, a low leakage magnetic circuit having a configuration as shown in FIG. 6 has been developed and is widely used.

In FIG. 6, 6 is an annular first magnet, 7 is a top plate larger than the outer diameter of the first magnet, 8 is a second magnet whose magnetization direction is opposite to that of the first magnet, and 9 is a second magnet. The bottom plate 1 is a shield cover that allows the magnetic flux of the second magnet to flow and at the same time shields leakage magnetic flux, and has a pole part on the bottom surface of the annular first magnet 6.
Further, a top plate 7 is provided on the upper surface, thereby forming a magnetic gap for inserting the voice coil, and a second magnet 8 whose magnetization direction is opposite to that of the first magnet 6 is provided on the lower surface of the bottom plate 1. Furthermore, a shield cover 9 is adhered to the lower surface of the shield cover 9, and a top plate 7 is attached to the upper end of the concave shield cover 9.
It has a configuration in which it is combined with the outer peripheral part of the. The low leakage magnetic circuit configured in this way has a main magnetic flux C caused by the first magnet 6.
The magnetic flux of the magnetic gap is composed of the main magnetic flux d of the first magnet 6 and the second magnet 8 whose magnetization direction is reversed, and the leakage magnetic flux e due to the first magnet 6 and The leakage magnetic flux f caused by the second magnet 8 is shielded by the shield cover 9 without leaking to the outside, and the leakage magnetic flux can be sufficiently reduced. On the contrary, the main magnetic flux d formed by the second magnet was improved without reducing the main magnetic flux C, and the circuit was a low-leakage magnetic circuit with little loss.

Problems to be Solved by the Invention However, in such a conventional configuration, as shown in FIG. 7, the magnetization directions of the first magnet 6 and the second magnet 8 must be reversed. , a first magnetic circuit constituted by the first magnet 6, the bottom plate 1, and the top plate 7, and a second magnetic circuit constituted by the second magnet 8 and the shield cover 9,
After being separately magnetized, the upper surface of the second magnet 8 must be adhered to the lower surface of the bottom plate 1.

Therefore, as shown in FIG. 8, the operating point g of the second magnetic circuit is lower than the operating point g of the first magnetic circuit because the magnetic circuit is not configured at the time of magnetization. The magnetic flux generated by the eight magnets was extremely small, resulting in an inefficient magnetic circuit.

Further, since the operating point of the second magnet is low, once it is exposed to a low temperature state, low temperature demagnetization occurs, resulting in a decrease in the main magnetic flux of the low leakage magnetic circuit.

An object of the present invention is to provide a method of manufacturing a low leakage magnetic circuit that can solve these problems.

Means for Solving the Problem In order to solve this problem, the present invention provides a bottom plate having a pole portion, a first annular magnet disposed on the top surface of the bottom plate,
A first magnetic circuit consisting of a top plate disposed on the top surface of the first magnet and having a hole forming a magnetic gap for inserting a voice coil between it and the pole part; An inverted annular second magnet, a plate placed on the top surface of the second magnet with a hole in the center, and a concave shield with a hole in the center placed on the bottom surface of the second magnet. a second magnetic circuit consisting of a cover, and a hole provided in the center of the shield cover when magnetizing the second magnetic circuit;
A second bottom plate having a pole part is inserted, and the pole part is further inserted between a hole provided in the center of the plate to form a magnetic path of a second magnetic circuit, and then magnetized. After performing this, a second magnetic circuit is joined to the outer periphery of the second magnetic circuit, and then the second bottom plate is removed.
Further, after removing the second bottom plate, a convex flat plate cover is joined to a hole provided in the center of the shield cover.

Effect With this configuration, when the first magnetic circuit and the second magnetic circuit are separately magnetized in opposite directions, the second magnetic circuit is inserted into the hole provided in the center of the shield cover and the plate with the pole portion. By performing magnetization with the second bottom plate having the second bottom plate fully inserted, a structure is created in which the magnetic flux easily flows, so that the operating point of the second magnetic circuit can be set high.

EXAMPLE An example of the present invention will be described below with reference to the drawings. Note that the same reference numerals as those in FIGS. 6 to 9 indicate the same parts.

FIG. 1 is a structural sectional view showing the configuration of a low leakage magnetic circuit manufactured according to an embodiment of the present invention.
10 is a plate with a hole in the center, 11 is a concave shield cover with a hole in the center, 12 is a convex flat plate cover, and 1 is a main magnetic flux generated by the second magnet 8. This shows the flow.

A bottom plate 1 having a pole portion is arranged on the lower surface of the annular first magnet 6, and a hole is provided in the center on the upper surface of the first magnet 6.
A first magnetic circuit has a top plate 7 larger than the outside diameter of the magnet, and forms a magnetic gap between the pole portion and the first magnet 6 for inserting a voice coil, and the first magnet 6 has a magnetization direction opposite to that of the first magnetic circuit. A plate 1o having a hole in the center is placed on the top surface of the annular second magnet 8, and a concave shield cover 11 with a hole in the center is placed on the bottom surface of the second magnet 8. A convex flat plate cover 1 is inserted into the hole provided in the center.
2 is connected to the second magnetic circuit in which the magnetic circuit 2 is arranged.

The operation of the low leakage magnetic circuit configured as described above will be explained below.

The magnetic flux of the magnetic gap is composed of the main magnetic flux C generated by the first magnetic circuit and the main magnetic flux 1 generated by the second magnetic circuit in which the magnetization direction of the first magnet 6 is reversed. As a method, as shown in FIG. 2, a first magnetic circuit consisting of a bottom plate 1, a first magnet 6 and a top plate 7, and a second
A second magnetic circuit consists of a magnet 8, a plate 1o, and a shield cover 11, and a second bottom plate 13 having a pole part is inserted into a hole provided in the center of the plate 10 and the shield cover 11. After magnetizing them separately, the first
The second magnetic circuit is connected to the outer periphery of the magnetic circuit of the second bottom plate 13. At this time, the second bottom plate 13 has a shape in which the total height of the pole portion protrudes from the hole in the center of the plate 1o, so that the second magnetic circuit As shown in FIG. 3, the second bottom plate 13
After removing the shield cover, a convex flat plate cover 12 for shielding magnetic flux leakage is joined to a hole provided in the center of the shield cover. At this time, the operating point of the second magnetic circuit is the second
As shown in the figure, the magnetic flux j flowing through the magnetic path formed by the plate 1o and the second bottom plate 13 and the shield cover 11
The structure creates a structure in which the magnetic flux k flowing from the side surface of the plate 1° flows easily, and as shown in Figure 4, the magnetic flux k flows easily to the operating point 1'c of the second magnetic circuit and the operating point g of the first magnetic circuit. This is something that can be improved.

As described above, according to this embodiment, the second bottom plate 13t-
By magnetizing it while inserted, the operating point can be set high. FIG. 6 shows the gap magnetic flux density distribution m of the conventional low leakage magnetic circuit shown in FIG. 7 and the gear joint magnetic flux density distribution ni according to an embodiment of the present invention. In this case, by setting the operating point of the second magnetic circuit high, it is possible to increase the utilization efficiency of the magnet, improve the gap magnetic flux density distribution, and improve reliability with less low-temperature demagnetization. It can be a low leakage magnetic circuit.

In one embodiment, when the first magnetic circuit and the second magnetic circuit are joined, a concave shield is formed between the lower surface of the bottom plate 1, the upper surface of the plate 10, and the outer periphery of the top plate 7 so that the magnetic circuit forms a closed loop. Although the upper end of the cover 11 was joined at the same time, due to the assembly method, the first magnetic circuit and the second magnetic circuit are connected to the lower surface of the bottom surface 1, the upper surface of the plate 10, the outer periphery of the top plate 7, or the lower outer periphery. If the shield cover 11 is joined to the upper end of the concave shield cover 11, even if a gap is formed in any of the joint parts, the characteristics of the low leakage magnetic circuit of the present invention will not be significantly deteriorated. Needless to say.

According to the present invention, a bottom plate having a pole portion, an annular first magnet disposed on the top surface of the bottom plate, and a ring-shaped first magnet disposed on the top surface of the first magnet and connected to the pole portion. a first magnetic circuit consisting of a top plate having a hole between which forms a magnetic gap for inserting a voice coil; a second annular magnet whose magnetization direction is opposite to that of the first magnet; A second magnetic circuit includes a plate disposed on the top surface and having a hole in the center, and a concave shield cover disposed on the bottom surface of the second magnet and having a hole in the center. When the magnetic circuit is magnetized, the second bottom plate having the pole part is fully inserted into the hole provided in the center of the shield cover, and the pole part is further inserted between the hole provided in the center of the plate. After magnetization is performed with the magnetic path of the second magnetic circuit configured, the second magnetic circuit is joined to the outer periphery of the first magnetic circuit, and then the second bottom plate is removed and the second magnetic circuit is then magnetized. By joining the convex flat plate cover to the hole made in the center of the shield cover from which the bottom plate of No. 2 has been removed, the operating point of the second magnetic circuit can be set high. It is possible to increase the utilization efficiency of the magnetic flux, which in turn improves the main magnetic flux, and at the same time, by setting the operating point high, low-temperature demagnetization is reduced and reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a structural cross-sectional view showing a low leakage magnetic circuit manufactured according to the present invention, FIG. 2 is a structural cross-sectional view showing the magnetization process of the low leakage magnetic circuit shown in FIG. 1, and FIG. FIG. 4 is a structural cross-sectional view showing the assembly process of the low leakage magnetic circuit shown in FIG. The figure is a characteristic diagram comparing the gap magnetic flux density distribution of the low leakage magnetic circuit of the present invention shown in Figure 1 with the gap magnetic flux density distribution of the conventional low leakage magnetic circuit. 8 is a structural sectional view showing the conventional low leakage magnetic circuit shown in FIG. 7, and FIG. 9 is a structural sectional view showing the magnetization process of the conventional low leakage magnetic circuit shown in FIG. FIG. 6 is a characteristic diagram showing the state of the operating point of the second magnetic circuit. 1...Bottom plate, 6...First magnet, 7.
...Top plate, 8...Second magnet, 10...
River/Plate, 11... River/Shield Cover, 12...
...Flat plate cover, 13... Second bottom plate, C
...Main magnetic flux due to the first magnetic circuit, 1...
・Main magnetic flux due to the second magnetic circuit, j, k...
Flow of magnetic flux during magnetization of the second magnetic circuit, 2...Operating point of the second magnetic circuit, n...Magnetic flux density distribution of the magnetic gap of the low leakage magnetic circuit of the present invention . Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 1 =) Y-11 car, Ibihoromachi-dori! The season of 6 is fishing, crying 1 (
78 Bay) Figure 6 Figure 7

Claims (3)

[Claims] (1) A bottom plate having a pole part, a first annular magnet placed on the top surface of this bottom plate, and a magnet for inserting a voice coil between the top surface of the first magnet and the pole part. a top plate having holes forming a gap;
a magnetic circuit, a ring-shaped second magnet whose magnetization direction is opposite to that of the first magnet, a plate arranged on the upper surface of the second magnet and having a hole in the center, and the second magnet. a second magnetic circuit consisting of a concave shield cover arranged on the lower surface of the magnet and having a hole in the center, and a pole is inserted into the hole formed in the center of the shield cover when magnetizing the second magnetic circuit. inserting a second bottom plate having a section, further inserting the pole section between the hole provided in the center of the plate, and
After magnetization is performed with the magnetic path of the magnetic circuit configured,
A method of manufacturing a low-leakage magnetic circuit, characterized in that the second magnetic circuit is joined to the outer periphery of the first magnetic circuit, and then the second bottom plate is removed. (2) The total height of the pole portion of the second bottom plate is such that it protrudes from the top surface of the plate when inserted into the hole in the center of the plate, and when joining the first magnetic circuit and the second magnetic circuit. 2. The method of manufacturing a low-leakage magnetic circuit according to claim 1, wherein the second bottom plate is pushed downward by the lower surface of the bottom plate constituting the first magnetic circuit. (3) Manufacture of the low leakage magnetic circuit according to claim 1, characterized in that after removing the second bottom plate, a convex flat plate cover is joined to the hole provided in the center of the shield cover. Method.