Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – Electron or ion beam deflecting type
Reexamination Certificate
2001-09-14
2004-02-24
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
Electron or ion beam deflecting type
C313S440000, C335S211000
Reexamination Certificate
active
06696907
ABSTRACT:
TECHNICAL FIELD
Background Art
The type of deflecting yoke core to which the present invention relates is used to constitute a deflecting yoke. A deflecting yoke, which is constituted by providing a horizontal deflection coil and a vertical deflection coil at a deflecting yoke core, is mounted between a neck and a funnel of a cathode ray tube (CRT). An electron beam emitted from an electron gun provided at the neck is deflected along horizontal and vertical directions. In a standard deflecting yoke core, the shape of an opening end at the neck portion and the shape of an opening end at the funnel portion are both circular.
Another deflecting yoke core in the prior art is disclosed in Japanese Examined Patent Publication No. 1996-28194 and adopts a structure having a circular opening end at the neck portion and an oval opening end at the funnel portion. In addition, Japanese Unexamined Patent Publication No. 1995-37525 discloses a technology whereby the deflection efficiency is improved without compromising moldability, by forming the inner surface of the deflecting yoke core in an almost oval shape and forming the outer surface of the deflecting yoke core in an almost completely circular shape. Japanese Examined Patent Publication No. 1996-7781 also discloses a similar deflecting yoke core.
However, these prior art technologies, which do not take into consideration the relationship between the core sectional area and the density of the core internal magnetic flux distribution, present a concern in that the density of the core internal magnetic flux is not consistent, and magnetic saturation may occur over an area of the core where the density of the core internal magnetic flux is high, resulting in an image plane distortion.
These types of deflecting yoke cores are formed by molding ferrite powder or the like into a tube achieving a specific finished shape. The molded product may have dividing grooves formed in advance so that it can be divided into two core pieces along the dividing grooves so as to allow the horizontal deflection coil and the vertical deflection coil to be provided with ease.
As disclosed in Japanese Unexamined Patent Publication No. 1995-37525, Japanese Unexamined Utility Model Publication No. 1996-194, and U.S. Pat. No. 4,754,190, the dividing grooves in a deflecting yoke in the prior art are normally provided at two positions facing opposite each other over a horizontal axis.
However, the dividing grooves in this structure are provided at areas where the horizontal deflection magnetic field is the most intense. While the vertical deflection magnetic field has a low frequency of approximately 60 to 100 Hz, the horizontal deflection magnetic field has a high frequency of approximately 20 to 120 KHz, and thus, the horizontal deflection magnetic field may become a predominant cause of core loss. In addition, the presence of the dividing grooves provided at areas where the horizontal deflection magnetic field is the most intense, reduces the core sectional area of these areas and, as a result, the density of the magnetic flux attributable to the horizontal deflection magnetic field becomes extremely high, further increasing core loss. As is well known, core loss manifesting under these circumstances increases in proportion to the density of the magnetic flux to the power of 2 to 2.5. Thus, a problem arises in that the core temperature rises on the two positions facing opposite each other over the horizontal axis where the dividing grooves are provided.
In addition, if the opening end facing toward the funnel has a long diameter along a major axis and a short diameter along a minor axis, as disclosed in Japanese Examined Patent Publication No. 1996-28194 and Japanese Unexamined Patent Publication No. 1995-37525, the core density becomes lower near the minor axis due to the structure of the forming die. This results in a lower degree of core strength manifesting near the minor axis, and induces chipping of the core and the like.
Since there is an area with a low core density in the core as described above, the core shrinks unevenly during the baking process, resulting in a significant degree of deformation.
Clip grooves are formed at two sides of the dividing grooves in advance in an actual molded product. When forming a deflecting yoke by using such a deflecting yoke core, the deflecting yoke core is first divided into two pieces along the dividing grooves, after which a separator, a horizontal deflection coil and a vertical deflection coil are provided and then the divided core pieces are assembled. Subsequently, clips are provided at the clip grooves at the two sides of the dividing grooves to couple the two core pieces. This process tends to cause an increase in core temperature and chipping of the core or the like even more readily.
While the shape of the opening end at the funnel portion is either oval or rectangular, the shape of the opening end at the neck portion is circular in the prior art. Such a structure does not adequately support an in-line type cathode ray tube achieved by linearly providing three electron guns corresponding to the three primary colors.
Japanese Examined Patent Publication No. 1996-28194 discloses a deflecting yoke core adopting a slot structure, which is constituted by providing a plurality of projecting portions continuously and in a radial pattern along the inner surface of the core, extending from a neck portion to a funnel portion, and providing a horizontal deflection coil and a vertical deflection coil at grooves formed between the projecting portions. However, since the positions of the horizontal deflection coil and the vertical deflection coil are determined in conformance to the positions of the projecting portions, magnetic field distribution cannot be adjusted. Thus, a means other than the deflecting yoke must be employed to implement adjustment, such as a ballast operation distortion correction, a pincushion graphic distortion correction or a convergence characteristics correction.
As a means for solving the problem described above, Utility Model Registration No. 2580242 discloses a deflecting yoke core having coil guide grooves and projecting portions formed in a non-radial pattern, corresponding to the wiring pattern of a vertical deflection coil and a horizontal deflection coil designed in advance.
However, after the molding process, the deflecting yoke core disclosed in this Utility Model Registration cannot be rapped out along the direction of the core axis (tube axis), since projecting portions must be formed in a radial pattern relative to the core axis in order to allow the deflecting yoke core to be rapped out along the direction of the core axis.
When this type of deflecting yoke core is used to constitute a deflecting yoke, the core must achieve a high degree of dimensional accuracy, and the core and the cathode ray tube must be assembled with a high degree of accuracy to ensure that an electron beam is deflected as designed, because the electron beam is deflected along the inner surface of the deflecting yoke core. Since the core is mounted at the cathode ray tube via a separator, the core must be mounted at the separator with great accuracy in order to ensure that the core and the cathode ray tube are assembled with a high degree of accuracy.
However, since the deflecting yoke core is a baked product formed by baking a ferrite powder molding, it is bound to become deformed due to baking shrinkage. The rate of thermal contraction occurring at this time is fairly high at approximately 10% to 20%, resulting in a reduction of the volume of the baked core which is only approximately 60% of the volume of the unbaked core. Thus, the assembly accuracy with which the core and the cathode ray tube are assembled becomes poor, which prevents an electron beam from being accurately deflected as designed. Consequently, problems arise, such as a poor image quality attributable to misconvergence.
The problems attributable to the deformation of the baked core discussed above may be solved by grinding the core. However,
Anbo Minoru
Ito Shinichiro
Iwaya Hitoshi
Ono Masahiro
Barrera Ramon M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
LandOfFree
Core for deflection yoke and its production method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Core for deflection yoke and its production method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Core for deflection yoke and its production method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3353850