JPS5831689A - Degausser - Google Patents

Abstract

PURPOSE:To surely degauss a shadow mask which is easily magnetized with external magnetic fields and to obtain excellent color purity, by making transient attenuated AC currents flowing to coils opposite in direction symmetrically. CONSTITUTION:A coil 231 is wound at a panel 21 of a funnel 20 of a color cathode-ray tube (CRT) and a transient attenuated AC current 41 flows to the coil 231 toward the arrow 241. Another coil 232 is wound to a neck 22 of the funnel 20 and a current 41 flows to the coil 232 toward the arrow 242 in the opposite direction to the coil 231 in the same phase. Magnetic flux to internal magnetism shields 251, 252 and a shadow mask 26 in the color CRT is generated in the direction of arrows 271, 272, and 273 almost along the direction of thickness of the shields 251, 252 and the shadow mask 26. Through the generation of this magnetic flux, the directions of maximum magnetization of the shields 251 and 252 and the shadow mask 26 are almost made coincident to degaussing the residual magnetism in excellent way.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a degaussing device, and more particularly to a degaussing device provided outside a color cathode ray tube used in a color television receiver aircraft.

Shadow masks are mainly used in color cathode ray tubes installed in color television receivers that are currently in general use. In a color cathode ray tube in which this shadow mask is used, the shadow mask and the internal magnetic shield used as necessary are magnetized by external magnetism such as earth's magnetism, and the residual magnetism caused by this magnetization causes electrons to be emitted from the electron gun. The direction of the beam is bent,
A phenomenon of decreased color purity occurs. In order to prevent this phenomenon of color purity deterioration, a degaussing device is usually provided to demagnetize the residual magnetism of the shadow mask and/or the internal magnetic shield.

This degaussing device is carried out by winding a coil in a predetermined shape around the outer part of a color cathode ray tube and passing a transient attenuated alternating current through this coil.

Conventionally, these degaussing devices have been used, for example, in a collar shade @ 7 annels (11 panels (11)) of a bell pipe, as shown in II.
A pair of coils (13t) (1
3m), and these coils (13*) (
13*) j(R8tL) so that the transient decay currents are in symmetrical positions and in the same direction, that is, arrow (14) (14t)
I was starting to drift in different directions.

According to such a degaussing device, the magnetic flux formed by the transient decay current is absorbed by the internal magnetic shield (1) as shown in FIG.
51) Magnetic shield inside shadow mask (15□)
By flowing in the directions of upward arrows (17*) (17g) (17a), the shadow mask α and the internal magnetic shield (15*) (15*) were demagnetized.

However, in such a conventional degaussing device, a shadow mask fA@, a mask 7 frame (not shown) and an internal magnetic shield (15*) built into the color cathode ray tube are used.
(15m), their magnetic conductivity changes depending on how they are joined together, and the ease with which the magnetic flux for demagnetization passes through depends on the method.
For this reason, the magnetic flux for demagnetization may not work effectively.
There was a drawback that residual magnetism could not be effectively demagnetized.

The present invention was developed in view of the above-mentioned drawbacks of the conventional art, and it is possible to effectively and reliably demagnetize the magnetized parts in the color picture tube, such as the shadow mask and the internal magnetic shield, to obtain an image with improved color purity. The purpose is to provide a demagnetizing device.

Next, one embodiment of the degaussing device of the present invention, the magnetic flux direction, and the waveform of the transient damped alternating current are shown in FIGS. 3 to 5! ! ! First, Figure 3 shows a color cathode ray tube viewed from the neck side, and one coil (23
t) is set by passing a transient decay current as shown in Figure 5 in the direction of the arrow (24t), and setting the other coil (231) so as to wind around the neck opening side of the funnel (7). In the direction of the arrow (24,), that is, the previous degaussing coil (23,
) and in the opposite direction, a transient damped alternating current I4 as shown in FIG.
A degaussing device is provided that allows the rays 1 to flow in the same phase. By providing such a degaussing device, the magnetic flux directed to the internal magnetic shields (25,) (25 snow) and the shadow mask (1) in the color cathode ray tube is transferred to
5*) (25t) and the arrow (27,) (27t) (27
1) The direction will occur and this arrow (271)
(27ri (27s) is the internal magnetic shield (25t) (
Since it almost coincides with the maximum magnetization direction of the shadow mask (25t) and the shadow mask (25t),
25! ) and the shadow mask (to) can be demagnetized.

According to the inventor's experiments, the demagnetization rate shown in the conventional degaussing device shown in FIG. It was confirmed that the demagnetization rate expressed by this formula reached 50%.

Next, another embodiment of the degaussing device of the present invention will be described with reference to FIG.

That is, in this example, the coil (33s) (3:
h) of 7 channels (to) of a color cathode ray tube, respectively.
From the C channel r3111 to the funnel example neck 031I along the vertical axis (7) of this channel approximately the tube axis (
The coils (331) and (33*) are provided as a pair at positions symmetrical to the plane containing the vertical ring, which is almost the same as the conventional one shown in FIG. It is characterized in that the alternating current is caused to flow in opposite directions, ie, in the directions of arrows (34s) (34), in the same phase at symmetrical positions. By doing this, it is possible to make the magnetic flux almost follow the thickness direction of the internal magnetic shield and shadow mask, as shown in Figure 11!4, and the same effect as in the previous embodiment is obtained. .

As described above, the degaussing device of the present invention reliably demagnetizes the effective surface of the shadow mask, which is easily magnetized by external magnetism such as terrestrial magnetism, especially the effective surface having the electron beam passage hole, and/or the internal magnetic shield. This makes it possible to obtain better color purity than with conventional degaussing devices, so its industrial value is extremely large.

[Brief explanation of drawings]

1 and 2 are diagrams showing a conventional degaussing device, in which FIG. 1 is an arrangement diagram of a degaussing coil, FIG. 2 is an explanatory diagram showing the magnetic flux direction by the degaussing coil, and 7 The figures are diagrams showing one embodiment of the degaussing device of the present invention, FIG. 3 is a layout diagram of the degaussing coil, FIG. 4 is an explanatory diagram showing the magnetic flux direction by the degaussing coil, and 5th Wi is a transient attenuation flowing through the degaussing coil. A curve diagram showing the waveform of an alternating current, and FIG. 6 is a layout diagram of a degaussing coil according to another embodiment of the present invention. 10.20.30--Funnel 11,21.31
...Panel 12.22.32...Neck 131, 131, 23*, 231, 331
, 33m...Coil 41...Transient damped alternating current agent Patent attorney Inoue -Male

Claims (2)

[Claims] (1) A transient attenuated alternating current that is provided on the outer wall of a color cathode ray tube that includes at least a shadow mask and/or an internal magnetic shield, and generates magnetic flux approximately along the thickness of the shadow mask and/or internal magnetic shield. A degaussing device consisting of a coil that can conduct current (2) A degaussing device 0 (匈) The coils are provided as a pair at the positions where the funnel and neck of the funnel of a color cathode ray tube are respectively wound, and the current is passed through these coils. 2. The degaussing device according to claim 1, wherein the directions in which the transient attenuated alternating currents flow are opposite to each other. (2) Coils are provided in pairs at positions symmetrical to a plane that includes the tube axis and said vertical axis, each extending from the /R channel of the funnel to the neck of the funnel along a straight axis of the spring. 2. The degaussing device according to claim 1, wherein the flowing directions of the transient attenuated alternating currents flowing through these coils are opposite at the symmetrical positions.