Magnetic roller device

At least one pair of adjacent magnets, magnet A of which serves both as an assistant magnet and a main magnet for a necessary magnetic pole is arranged so that it may have a magnetic component in the right angle direction with respect to the magnetized direction of another magnet B. Magnet A itself forms not only the main magnetic pole, but also is adapted to increase the flux density of magnet B in the outer circumference direction.

BACKGROUND OF THE INVENTION 
This invention relates to a magnetic device which requires the supply of a 
high flux density used for a magnetic roller, particularly for a plain 
paper copier. 
In conventional magnetic rollers, a magnetic roller is well known wherein a 
sintered ferrite magnet having a rectangular cross-sectional area is 
adhered on a shaft by an aligned distribution with special form. However, 
such an arrangement significantly increases the manufacturing cost to form 
a shaft of special shape. In addition, the sintered ferrite magnet used is 
brittle and difficult to assemble. Further, defects can be caused by 
mechanical impact or vibration occurring after assembly. Furthermore, it 
is difficult to form a magnet having a profiled cross section because of 
the molding characteristics of sintered ferrite magnet material and the 
freedom in design of magnetic poles is very low. A magnet having a 
construction in the form of a plastic magnet in a bar shape, aligning it 
so that the direction of the magnetic poles thereof may be in the radial 
direction with respect to the central axis of the roller, and assembling 
it, is well known. However, in that case, it is very difficult to obtain a 
desired and sufficient magnetic flux density and the adjustment of the 
flux density is also different. 
Furthermore, though a method of after-work is also provided in order to 
increase the magnetic flux density, it is not easy to accomplish. 
Even in the case wherein a sintered ferrite magnet is employed, efforts to 
obtain a higher flux density are performed. In spite of such efforts, 
since a profiled magnet cannot be obtained when sintered ferrite is used, 
a method of assistant magnets is adopted in addition to the main magnets 
(magnets corresponding to or giving the necessary magnetic poles). 
However, this method is far more difficult in assembly and results in a 
considerably higher final cost. 
SUMMARY OF THE INVENTION 
This invention is performed from the above background in order to furnish a 
magnet roller having a high performance obtained by adapting it to a 
magnetic device so that a magnet corresponding to a necessary magnetic 
pole may be provided an operation as an assistant magnet mutually.

DETAILED DESCRIPTION OF THE INVENTION 
This invention provides a magnetic device which it is possible to provide 
in practice without any difficulty of assembly by forming magnets 
corresponding to necessary numbers of magnetic poles at the circumference 
of a magnetic roller so as to act as assistant magnets thereby intending 
the same increase of magnetic flux density as that of a case wherein 
assistant magnets are mounted notwithstanding the configuration of the 
main magnet. 
One of the features of the magnetic device of this invention is to form a 
magnetic circuit wherein together with at least one magnet, it forms an 
assistant magnet of other magnet as described above. 
In order to realize that feature, it is necessary that each magnet has a 
required profile cross section. Accordingly, it is appropriate to form the 
device with a synthetic resin bonded magnet having good molding 
characteristics from the industrial point of view. 
In order to provide high magnetic performance, it is desirable to use a 
so-called anisotropic bonded magnet molded from a synthetic resin 
composition containing anisotropic magnetic powders under a magnetic 
field. Generally, to form a magnet roller having a wide practical value, 
the maximum energy product of the magent necessitates more than 
1.0.times.10.sup.6 Gauss.Oerstead, preferably, more than 
1.2.times.10.sup.6 Gauss.Oersted. It is desirable to provide a magnet 
which contains 85 to 95 weight percent of magnetic powders, such as 
anistropic hard ferrite. The residual components which form the magnet may 
be provided singly or by mixing more than two kinds of resinous compounds 
from synthetic high polymers of homo- or copolymers of polymerizable 
compounds such as olefin, vinyl, or diene compounds, and the like, and 
synthetic polymers obtained by condensation of compounds having 
condensable functional groups, or chemically modified polymers from the 
above-mentioned polymers. In this case, from an industrial point of view, 
such as processability and other efficiencies, thermoplastic resins are 
desirable. 
In the case of magnet molding the axes of easy magnetization (hereinafter 
called "easy axes") of anistropic magnetic powders are adapted to be 
oriented in one direction by molding the magnet while applying a magnetic 
field in one direction at a temperature at which a binder of synthetic 
polymer is kept fluid. In this invention, a mechanical orientation molding 
is not appropriate because magnets having a profiled cross section are 
employed. The molding method in the magnetic field may be selected from 
molding methods widely used for synthetic polymer molding. However, an 
extrusion or an injection molding method is desirable from the standpoints 
of the facility of the unit design and economy. To obtain efficient 
performance of the anisotropic magnet thus obtained, magnetization in the 
same direction as the magnetic orientation direction is preferable. 
Further, the preferred embodiments of this invention is hereinafter 
described with reference to FIGS. 1 and 2. The illustrated embodiments are 
appropriate examples of this invention. In the drawing figures, the 
numeral 1 is a ferro-magnetic metal shaft and a plurality of magnets 
M.sub.1 to M.sub.6 (6 magnets in this example) are positioned at the 
circumference thereof. The outer circumference of the roller is defined by 
the exposed outer surfaces of the magnets. Each magnet M.sub.1 to M.sub.6 
is magnetized in the direction shown by an arrow so as to orient the easy 
axis (the magnetized directions of each M.sub.1 to M.sub.3 are abridged in 
FIG. 1). 
The above magnets M.sub.1 to M.sub.6 are main magnets and correspond to the 
necessary numbers of magnets at the circumferences of the magnet rollers. 
Further, in the above magnets (e.g., M.sub.5 in FIG. 1 and M.sub.5 in FIG. 
2) one magnet (e.g., M.sub.5) of at least one adjacent pair (e.g., magnets 
M.sub.5 and M.sub.6 in FIG. 1 and magnets M.sub.5 and M.sub.4 in FIG. 2) 
are one pair, respectively contact each other directly between said 
ferro-magnetic metal shaft 1 and the circumference 2 of the magnetic 
roller so that one magnet (e.g., M.sub.5) may be an assistant magnet of 
another residual magnet (e.g., M.sub.6 and M.sub.4) and the magnets are 
aligned so that an angle between the magnetized direction of said mutual 
magnets and the orientation direction corresponding thereto may be a right 
angle. When one pair of adjacent magnets directly contact each other as 
shown in the example, the assistant magnet effect can be set most 
effectively. Accordingly, it is a necessary condition of the magnetic 
device according to this invention that said adjacent magnets sufficiently 
contact each other magnetically. Therefore, if there exists a gap between 
the adjacent magnets which form one pair, the assistant magnet effect can 
be obtained according to the degree of the gap as long as the leakage of 
the magnetic flux is not extremely large. It is a sufficient condition 
that both magnets only magnetically contact each other through a slight 
gap, even if both do not directly contact each other physically. 
Further, when, for example, a magnet A which serves as an assistant magnet 
and a main magnet of one pair of the adjacent magents is aligned so that 
it may have a magnetic component in the right angle direction with respect 
to the magnetized direction of another magnet B, the magnet A itself not 
only forms a main magnet, but also increases the flux density given by 
magnet B in the outer circumference direction. Since the increasing degree 
thereof changes according to the strength of the magnetic component in 
said right angle direction, it is clear form this example that the most 
effective result can be obtained when said magnet B is aligned so that the 
magnetized direction thereof may be at a right angle with respect to the 
magnetized direction of magnet A. 
In the examples, said each magnet M.sub.1 to M.sub.6 has a profiled cross 
section which together form a part of the circumference of the magnet 
roller with a surface of the magnet itself in order to realize the effect 
of this invention, and forms a permanent magent consisting of a resin 
bonded permanent magnet, for example, comprising hard ferrite particles 
and synthetic resin, wherein an easy axis is oriented in one direction 
(shown by the arrows) and is magnetized in the same direction thereto. 
Each magnet M.sub.1 to M.sub.6 has a bar shape formed by extrusion or 
injection molding. In this case, in order to magnetize it in one direction 
by orienting the easy axis in that direction, a status oriented in the 
magnetic field is formed. The value of maximum energy product thereof is 
desired to be more than 1.0.times.1.0.sup.6 Gauss.Oersted, preferably more 
than 1.2.times.10.sup.6 Gauss.Oersted. In this example, the magnets 
M.sub.1 to M.sub.6 are manufactured by taking the maximum energy product 
for forming the main magnetic poles as about 1.35.times.10.sup.6 
Gauss.Oersted and the measurement of magnetic characteristics is 
performed. The results are as follows. The outer diameters of the magnetic 
rollers in FIGS. 1 and 2 are around 35 mm. The measured values of the flux 
densities are those at positions apart from the outer circumference by 2.5 
mm, namely that of the circle 3 having a 40 mm diameter. 
______________________________________ 
M.sub.1 
M.sub.2 M.sub.3 
M.sub.4 
M.sub.5 
M.sub.6 
______________________________________ 
FIG. 1 710 700 190 460 550 690 
FIG. 2 710 700 190 740 540 430 
______________________________________ 
Judging from the result, it is clear that the magnetic flux density of the 
magnet (M.sub.6 in FIG. 1 and M.sub.4 in FIG. 2) having a magnetized 
direction which forms a right angle with that of the magnet 5, (this 
magnet itself is a main magnetic pole) and functions as an assistant 
magnet, is increased. FIG. 4 shows another embodiment of this invention. 
In FIG. 4, each magnet has main magnetic poles, M.sub.1 and M.sub.3 are 
the assistant magnet of M.sub.2, and M.sub.4 is the assistant magnet of 
M.sub.3. 
Thus, according to this invention, when a plurality of magnets are 
connected and configured around a ferro magnetic metal shaft to form a 
magnet roller, magnets corresponding to the necessary numbers of magnetic 
poles at the circumference of said magnetic substance rollers are 
provided, and said mutual magnets in at least one group of adjacent 
magnets are provided with a magnetically contacting portion without the 
aid of the ferro-magnetic metal shaft between said strong ferro-magnetic 
metal shaft and the circumference of the magnetic substance roller so that 
one magnet of at least one group of adjacent magnets may be an auxiliary 
magnetic pole in itself. The magnet which serves for the auxiliary 
magnetic pole additionally is aligned with the magnetized direction 
thereof and can have a magnetic component at a right angle direction with 
respect to the magnetized direction of another residual magnet. 
Accordingly, said magnet can obtain the effect of increasing the magnetic 
force in the easy axis direction in the point that said magnet has a 
function as the auxiliary pole of the adjacent magent together with being 
the main magnetic pole itself. In this case, there is no need of a 
complicated construction for securing another magnet for an auxiliary pole 
compared with the conventional one. Accordingly, it is very advantageous 
in manufacturing. Further, since the magnetic force increases by only 
mutual arrangement of the magnets, the resin bonded magnet also can be 
used to secure a sufficient and satisfactory magnet force without any 
additional work.