JPS631299A - Low magnetism leak speaker - Google Patents

Abstract

PURPOSE:To prevent the occurrence of color blur and color deviation of a high definition television receiver by forming an enclosure stuck to the inside bottom of a bottomed deep drawing frame consisting of a magnetic material and providing a shield cover on the outside peripheral part of the enclosure and forming the sheild cover into a body of revolution whose section is an ellipse having the minor axis in the radial direction of a diaphragm. CONSTITUTION:A magnetic sheild cover 29 consisting of a magnetic material is arranged in the outer peripheral part of a bottomed deep drawing frame 20 between a spacer 30 consisting of a paramagnetic material between them. An enclosure 22 has a bottom larger than the outside of a magnetic circuit 19 and is formed to stick to the inside bottom of the frame 20 consisting of a magnetic material. The leaked magnetic flux density on the outside of the frame is low in the transverse direction of the frame and is high in the lower part. However, there is not a magnetic potential difference on the sheild cover 29 because the shield cover 29 is formed into a body of revolution whose section is along an isomagnetic flux face from a point E to a point G and is an ellipse having the minor axis in the radial direction of the diaphragm. Thus, the magnetic flux leaked out of the frame 20 is shut by the shield cover 29 and is not leaked to other spaces.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a low magnetic leakage type speaker used in video equipment using a CRT.

BACKGROUND OF THE INVENTION Television receivers compatible with audio multiplex broadcasting and stereo broadcasting have been manufactured, and speakers have been placed on the left and right sides, and slim cabinets have been designed to be placed close to the CRT. Under these circumstances, if you use a normal speaker, the magnetic field generated by the speaker's magnetic field will bend the trajectory of the electrons emitted from the CRT's electron gun, causing deformation and discoloration of the screen. Smudges, etc. occur. In order to solve this problem, there has been a low magnetic leakage type speaker that has a structure in which a magnetic circuit is fixed to the inner bottom surface of a deep-drawn frame. (For example, Japanese Utility Model Publication No. 52-64343).

The conventional low magnetic leakage type speaker mentioned above will be explained below with reference to the drawings.

FIG. 6 is a half-sectional view of a conventional low magnetic leakage type speaker. In FIG. 6, 1 is a bottom plate, 2 is an annular magnet, 3 is a top plate, and bottom plate 1
Then, the top plate 3 serves as a magnetic circuit 6 that holds the annular magnet 2 and forms an annular magnetic gap 4. Reference numeral 6 denotes a deep-drawn frame made of a magnetic material, the bottom of which is larger than the outer shape of the magnetic circuit, and a through hole 7 is formed at its upper end. The back surface of the magnetic circuit 5 is fixed to the inner bottom surface of the deep-drawn frame 6. The casing 8 is formed by the above structure.

A voice coil bobbin 9 has a voice coil 10 wound thereon, and is fixed to the top plate 3 via a damper 11 in order to suspend the voice coil 10 in the magnetic gap 4. Reference numeral 12 denotes a diaphragm whose inner circumferential portion is fixed to the voice coil bobbin 9, while its outer circumferential portion is fixed to the frame 6 via an edge 13. 14 is a dust cap that closes a hole on the inner circumference of the diaphragm 12.

The operation of the conventional low magnetic leakage type speaker constructed as described above will be explained.

Now, assume that the top plate 3 side of the temporarily magnetized annular magnet 2 is the north pole, and the bottom plate 1 side is the south pole. Therefore, the bottom and side surfaces of the deep drawing frame 6 are magnetized to the S pole. In this case, most of the magnetic flux flows from the top plate 3 through the magnetic gap 4 to the bottom plate 1, but the remaining magnetic flux flows into the bottom and side surfaces of the deep drawing frame 6.

Problems to be Solved by the Invention However, the magnetic flux leaking from the middle part of the top plate in the - section largely circulates around the through hole 7 provided on the upper end side of the deep drawn frame 6 and the entire surface thereof, and is transmitted to the back of the low magnetic leakage type speaker. In high-definition television receivers, etc., which are more susceptible to leakage magnetic flux than current television receivers because it flows into the sides, color bleeding and color shift are likely to occur, so it is necessary to fix the speaker far away from the cathode ray tube. There were problems such as the need for magnetic shielding and other magnetic shielding measures.

The present invention has been made in view of the above problems, and aims to provide a low-magnetic leakage type speaker that can be used even in high-definition television receivers at low cost.

Means for Solving the Problem To achieve this object, the low magnetic leakage type speaker of the present invention has a magnetic circuit that forms an annular magnetic gap with a top plate and a bottom plate fixed to the upper and lower surfaces of an annular magnet. a casing whose back surface is fixed to the inner bottom surface of a bottomed deep-drawn frame made of a magnetic material and having a bottom surface larger than the outer shape of the magnetic circuit; and a shield made of a magnetic material on the outer periphery of the casing. A cover is provided, and the shield cover is configured as a rotating body whose cross section is an oval whose diameter is smaller in the radial direction of the diaphragm.

Effect The present invention has the above-described structure, and includes a top plate forming one magnetic pole of an annular magnet, a bottom plate forming the other magnetic pole, and a bottomed plate connected to the top plate and magnetized to have an opposite polarity. By surrounding the inner bottom and side surfaces of the deep-drawn frame with a magnetic shielding cover made of ferromagnetic material, the magnetic flux leaking to the outside of the deep-drawn frame (') is late closed by the cover, so that it is not leaked to other spaces. This means that it will not leak.

Furthermore, by making the shape of the shield cover a rotating body whose cross section is an ellipse with a smaller diameter in the radial direction of the diaphragm, which approximates an equal magnetic flux surface with equal leakage magnetic flux density, leakage magnetic flux due to remagnetization will not occur. Become.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a half-sectional view of a low magnetic leakage type speaker according to an embodiment of the present invention. In FIG. 1, 15 is a bottom plate, 16 is an annular magnet, and 17 is a top plate. The bottom plate 16 and the top plate 17 form a magnetic circuit 19 that sandwiches the annular magnet 16 and forms an annular magnetic gap 18. . Reference numeral 20 denotes a deep-drawn frame made of a magnetic material whose bottom surface is larger than the outer shape of the magnetic circuit, and a through hole 21 is formed in the upper end side of the frame. The back surface of the magnetic circuit 19 is fixed to the inner bottom surface of the deep drawing frame 20.

22 is a housing, 23 is a voice coil bobbin which combines two cylinders having two diameters, one large and one small, the cylinder part around which the voice coil 24 is wound.A damper 25 is used to suspend the voice coil 23 in the magnetic gap 18. It is fixed to the top plate 17 via. Reference numeral 26 denotes a diaphragm whose inner circumference is fixed to the voice coil bobbin 23, and whose outer circumference is fixed to the frame 2o via an edge 27.

28 is a dust cap that closes a hole on the inner circumference of the diaphragm 26. These are the same as before.

Reference numeral 29 denotes a magnetic shield cover made of a magnetic material, which is disposed on the outer periphery of the bottomed deep-drawn frame via a spacer 30 made of a paramagnetic material. The shape of this cover is a rotating body whose cross section is an ellipse whose diameter is smaller in the radial direction of the diaphragm, and approximates the equal magnetic flux line of the speaker leakage magnetic flux.

The operation of the low magnetic leakage type speaker of this embodiment configured as above will be explained.

In FIG. 1, the back side of the magnetic circuit wT19, which forms an annular magnetic gap with the top plate 17 and bottom plate 15 fixed to the upper and lower surfaces of the annular magnet 16, is shown in the magnetic circuit 19.
The leakage magnetic flux density of a speaker consisting of a casing 22 which has a bottom surface larger than the external shape and is fixed to the inner bottom surface of a deep-drawn frame 2° made of a magnetic material is as shown in FIG. Become. Curve A shows an equal magnetic flux density of 0.6 Gauss. Similarly, curve B shows 0.9 Gauss, curve C shows 1.6 Gauss, and curved line shows 1.8 Gauss.

The leakage magnetic flux density outside the frame is low in the lateral direction of the frame and high in the lower direction. Therefore, points E and F, which are equidistant from the frame, have significantly different values of 1.8 Gauss and 2o Gauss. Therefore, as shown in Figure 3, E
- If a shield cover 40 is placed connecting point F, the shield cover 40 will be magnetized due to the magnetic potential difference from point F to point E, and leakage magnetic flux as shown by the dotted line will occur. In the embodiment, since the rotating body has a cross section of an ellipse with a smaller diameter in the radial direction of the diaphragm along the plane of equal magnetic flux from point E to point G, the magnetic potential difference on the shield cover 29 is Since there is no shield cover 29, the shield cover 29 is hardly magnetized, and the leakage magnetic flux leaking to the outside of the bottomed deep-drawn frame 20 is closed late by the shield cover 29, so that it does not leak into the performance space.

In this embodiment, the speaker inside the shield cover 29 is a deep-drawn frame 20 with a bottom, but as shown in FIGS. A low magnetic leakage speaker having a magnet type magnetic circuit 31, and a top plate 17 and a bottom plate 15 fixed to the upper and lower surfaces of one annular magnet 16.
The back side of the magnetic circuit 19 forming the annular magnetic gap 18 is
In a space formed by a casing 22 fixed to the inner bottom surface of a bottomed deep-drawn frame 20 made of a magnetic material and having a bottom surface larger than the external shape of the magnetic circuit 19, a diaphragm 26, and a damper 25. , a speaker may be provided with an annular magnetic shield plate 32 made of a magnetic material.

Effects of the Invention As described above, the present invention provides a magnetic circuit whose back surface is larger than the outer shape of the magnetic circuit, which forms an annular magnetic gap by a top plate and a bottom plate fixed to the upper and lower surfaces of an annular magnet. A casing that has a large bottom surface and is fixed to the inner bottom surface of a bottomed deep drawn frame made of a magnetic material, and a shield cover made of a magnetic material is provided on the outer periphery of the casing, and the shape of the shield cover is adjusted. The diaphragm is a rotating body whose cross section is an ellipse with a smaller diameter in the radial direction (an electric leakage type speaker can be realized).

[Brief explanation of the drawing]

Fig. 1 is a half-sectional view of a low magnetic leakage type speaker according to an embodiment of the present invention, Fig. 2 is a leakage magnetic flux distribution diagram of a conventional low magnetic leakage type speaker, and Fig. 3 shows one shape of a shield cover. 4 and 5 are half sectional views of a low magnetic leakage type speaker according to another embodiment of the present invention, and FIG. 6 is a half sectional view of a conventional low magnetic leakage type speaker. 15... Bottom plate, 16... Annular magnet, 17... Top plate, 18
......Annular magnetic gap, 19...Magnetic circuit, 20...Bottomed deep drawing frame, 21...
...Through hole, 22...Housing, 23...Voice coil, 24...Voice coil bobbin, 2
5... Damper, 26... Vibration plate, 27
...Edge, 28...Dust cap, 29...Magnetic shield cover, 3o...
... Spacer, 31 ... Opposing magnet type magnetic circuit, 32 ... Annular magnetic shield plate. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure ≦ Nnan - Kotobuki'J-1 0tsu 32 --- J Rent 1 Tento type shield JR Figure 5 Figure 6

Claims (1)

[Claims] A back surface of a magnetic circuit forming an annular magnetic gap with a top plate and a bottom plate fixed to the upper and lower surfaces of the annular magnet has a bottom surface larger than the outer shape of the magnetic circuit,
and a housing formed by being fixed to the inner bottom surface of a bottomed deep-drawn frame made of a magnetic material, and a shield cover made of a magnetic material on the outer periphery of the housing, and the shape of the shield cover is set in the radial direction of the diaphragm. A low magnetic leakage speaker characterized by having a rotating body whose cross section is an ellipse with a small diameter.