Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to a distributor and more
particularly tO a rotor brush of a distribulor treated to suppress electromag-
netic lnterference, hereinafter referred ro simply as noise waves, generated
by the distributor.
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It is well known that a distributor provided in a vehicle, such as an
automobile or the like, generates noise waves by spark discharges inter-
mittently gener~ted ut high rates which interfere with radio and telcvision
broadcasting j various kind of radio communication, etc .
These noise waves are becoming an increasingly serious problem
because of the recent tendency towards the generation of a s~rong spark
discharge in an ignitlon device by a large current in n short time in order
to purify the exhaust gases.
Hitherto, various proposals have been made for suppressing these
noise waves, but exceedingly few of them huve been put into practical use
because of their high cost in the mass production of vehicles or becuuse of
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their poor performance. Typical of the noise suppressing means which have been
put into practical use is one in which the surface of at least one of the dis-
charge electrodes respectively provided on the rotor brush and a side terminal,
which are facing each other to form a discharge gap in the distributor, is
additionally provided with a coating of highly resistive material, as mentioned
in the specification of Japanese Patent No. 858,984, corresponding to U.S. Patent t
No. 4,007,342. For example, a rotor brush is composed of a silicon wafer, the
surface of which is formed with a coating of highly resistive material or a sili-
con oxide coating on the silicon wafer per se. Alternatively, the rotor brush
10 and side terminal are each composed of a brass material or a resistive alloy
invar or the like, and on the surface of each of the respective discharge elec-
trodes of the rotor brush and the side terminal is deposited, by a spraying
method, with a resistive material, such as copper oxide, aluminium oxide, resis- tive alloy invar or the like.
In the examples described herein, silicon is the most superior material
ln providing noice wave suppressing characteristics. However, silicon has
certain disadvantages in that it is very expensive for the mass production of
vehicles and it requires after-treatment to form a coating of silicon oxide
as a highly resistive material. While a rotor brush, upon which
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copper oxide or the like is spray-deposited, is economically practical, there
are other disadvantages in such cases in that such a sprayed rotor brush is
inferior to the silicon wafer rotor brush as to the noise wave suppressing
effect attained, ln that the surface of such a sprayed rotor requires shot-
blast treatment and further requires a deposition by spraying of nickel
aluminlde or the like as a foundation, in order to increase the stickiness
thereof prior to the treatment of spraying copper oxide or the like, and in
that the discharging gap has to be specially designed taking into consider-
ation the thickness of the sprayed material, which comes to several milli-
meters.
An ob~ect of the present invention is to provide a distributorrotor brush which is more suitable for mass production and is less expensive
than conventional ones and superior to these in noise wave suppressing cap-
ability.
It ls a further object of the present invention to provide an
improved method of forming a sillcon coating on a surface of a dlstrlbutor
rotor brush.
More particularly, in accordance with one aspect of the invention
there is provided in a distributor having a rotor brush with a discharge
electrode portion adapted to rotate in association with a driving rotary
shaft of an internal combustion engine, and side terminals arranged
adjacent to a locus of rotation of the rotor brush, forming a discharge
gap between said discharge electrode portion and said side terminals
respectively,
the improvement which comprises,
an ion plated silicon coating disposed on the surface of the
discharge electrode portion of the rotor brush for reducing electro-
magnetic noise caused by current across said discharge gap. The silicon
coating may be disposed on an upper, a lower, and a side surface of the
discharge electrode portion. The silicon coating may be disposed only on
the side surface of the discharge electrode portion. The thickness of
the coating may be 5 - 15 )u.
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In accordance with a second c~spect of the invention there is provided,
a method for forming a silicon coating on a surface of a rotor brush for a
distributor by an ion-plating method, comprising the steps of:
establishing a low pressure atmosphere about said rotor brush;
ionizing an inactive gas in said low pressure atmosphere while main-
taining the rotor brush at a relative negative potential; and
vapori~ing a silicon mass in the presence of said rotor brush. The
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surface of the brush may initially be cleaned by sputtering. ~
Specific embodiments of the invention will now be described having ,;
reference to the accompanying drawlngs in which;
FIGURE 1 is a partially sectional elevation view of a conventional
distributor rotor brush;
FIGURE 2 i8 an enlarged plan view of the portion shown wlthin a
circle A of Figure 1, when the present invention is applied thereto;
FIGURE 3 is a sectional elevation view of Figure 2;
FIGURE 4 is a perspective view of Figure 2;
FIGURE 5 is a sectional view of a silicon ion-plating device;
FIGURE 6 i8 a perspective view of rotor brushes in the device of
Figure 5; ~ : -
FIGURE 7 is a graph comparing the characteristics in noise wave
suppressing effect of a rotor brush according to the present invention wlth
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the conventional ones; and
FIC:UI~E 8 is a graph showing the characteristic of Ihe rotor brush
according to the present invention when the Ihickness of the silicon plating
is changed.
Referring now to FIGURE 1 a distributor 1 is conventionally composed
; of a rotor brush 2 adapted to rotate in associalion with a driving rotary shaft
of an internal combustion engine and a plurulity of side terminals 3 are
arrungad adjaccnt to a locus of the rotation of the rotor brush 2 with a
discharge gap g being provided ~herebetween.
FIGURES 2-4 are enlarged detail views of the portion disposed within
the area of a circle A as shown in l-:IGURE 1 when the present invention is
applied thereto. A silicon coating 5 of about 5-15,l~ thickness is formed on
the surface of the rotor brush 2 or only on the surfacc of ~ discharge
electrode portion 4 at the end portion of the rotor brush 2. Sufficient per-
formunce is obtained if the silicon coat~ng 5 is formed on the surface of the
discharge electrode portion 4 of the rotor brush 2. Eurther even when the
silicon coating 5 is ormed only on the surface of the discharge electrode
portion 4 - it is sufficient for good performance to form the silicon coating
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msinly on the peripheral edge surface G facing the side terminals and only
on the portions of the respective upper and lower surfaces 7 and 7', which
are perpendicular to the surface G and are adjacent thereto. As the material
, composing the rotor brush ? any commonly used good electro-conductive
material, such as brass, steel or the like, may be employed.
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~r The formation of the silicon coating 5 on the surface of the rotor brush
2 may be achieved by an ion-plating method described hereinafter.
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.i After lightly washing with trichloroethylene or the like, a great number
. of the rotor brushes 2 are closely hung by a supporting rod ~ or the like ln
~ 10 a vaeuum eontuiner 8, u8 shown in l lGU~l~ 5 . At the same time, a mass of
,.~ silieon 10, eonsisting of high purity silicon, is set a eertain dislanee from
und facing tllc cclge surfaces û of the discllarge electrodes 4 of the rotor
brushes 2. After a vacuum is applied to the container 8, by means of an
.; exhaust device 13, argon gas or the like is introduced to thc vacuum area
,, 15 in the eontainer 8 through a gas introducing device 14, thereby providing
. an inactive gas atmosphere of argon gas or the like of about 10 torr. A
.. bias voltnge of several KV is applied between the container, which is
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. . grounded to be set at zero potential, and the rotor brush 2 in such a manner
. that the eontainer functions as a positive cleetrode and the brushes as a
~ neg~tive el Irode.
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¦ Thus, a glow discharge is generated to ionize the inactive argon gas
or the like into positive ions which rush onto the surface of the rotor brushes
2, which are maintained at negative potential.
The surface of each rolor brush 2 is scraped at a rate of some
Ansgtroms per minute by the ions. In this case, if any oxide has been
artached on the surface thereof, the portion a~ached with oxide is concen-
tratedly scraped by the ions of the inactive gas. A stain or oxide coating
~'"~ on the surface only preliminarily cleaned with trichlene or the like can be
readily removed within 10 minutes by sputter-cleaning by the ions. Next,
the pressure in the container 8 is depressed to about 10 torr to vaporize
the mass of silicon 10 by meuns of an electron beam, plasma arc or the like.
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When using the electron beam method, an electron beam 12 is generated
by an electron beam generator 1l and is suitably defJectcd l~y npplication of
a magnetic field, so as to irradiate on the mass of silicon 10 und thereby fuse
and vaporize the mass of silicon lO, The vaporized silicon is attuched to
' the discharge electrode 4 of each rotor brush 2, mainly on the edge surface
6, which is disposed in facing rela~ion ro the mass of silicon 10, and is
further attached to a certain extent to the upper and lower, or side nat
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surfaces 7 and 7' perpendicular to the surface 6. Thus, ion-plating is
~; effecled. A ul 5-20 minules irredirlion IO vzporize the slliccn is sufficienr
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¦ to form a silicon coating 5 of about 5-15~l~ thickness. The after-trentment ~ -
slep to form a silicon oxide coating, which is necessary for the known
silicon wafer rotor brush or a rotor brush sprayed with silioon, is not
required when the silicon coating is formed by tlie present ion-plating
method .
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The experimental results of the characleristics in noise wave suppress-
¦ ing effect of the rotor brush formed with a silicon coating uccording tO the
l~ ;' present invention and the influence of the thickness of the silicon coating
will be described next.
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FIGURE 7 shows the measured resulls of the noise wave field
intensity, comparing the case when the distributor 1 containing a rotor
brush 2 formed with a silicon coating according to the present invention is
,~ actually mounted on a vehicle with Ihe case when a distributor containing
u conventional rotor brush sprayed wi~h copper oxide is mounted on a
vehicle and with the case when a distributor having un untreated rotor
brush is mounled on a vehicle. In FI~U~E 7, the ordinate axis represents
the noise wave field inte~;ity (dl~) on the horizont~lly polarized wave plane
and the abscissa axis represents the frequency (Mflz) of the measured
noise waves.
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1~57344
It is apparent from I;lGUl~E 7 that the horizontally polarized noise -
wave field intensity, when the silicon ion-pluted rotor brush is employed,
is always lower than that when the non-treated rotor brush or 1he rotor brush
sprayed with highly resistive matel~ial is employed in all the l`requencies
within the measured range. This means that, uccording to the present inven-
tion, the noise wave suppressing effect is very remarkably improved, by
greatly reducing the noise wave field intensity.
FlGURE 8 shows the effect on the hori~ontally polarized noise wave
field intensity when the thickness of the silicon layer formed by ion-plating
is changed. As seen from this figure, the thickness of about 5-I5 ~ of ion-
plated silicon layer results in a satisfactory effect to SUppI'C!SS noise waves.
The rotor brush thus treatecl by the ion-plating method and having a silicon
coating of about 5-15 lt thickness shows rhe same excellem effect in noise wave
supprcssing capabilities us the silicon wafer rotor brush . I ven if Ihe thickness
of the silicon couting is furthel increased nbove the thickness of I5,~, the
effect cannot be much improvcd. When the thickness of the silicon coating
is selected to be only about 0.5-2.5 ~, the noise ~ave suppressing cffect
may deteriorate with long use. llowever, lf the thickness is selected to be
more than 5~ , the noise wave suppressing churactclistic is maintained
qui~e stable wi~hou~ changing Irom its inirial slate und wilhslunds long usage.
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When t e brush according lo the present inventioo is ttsed, an
¦ extremely remarkuble effect for suppressing noise waves is obtained whlch
is far superior to the rotor brush having a sprayed copper o~;ide coating and
is the same as the silicon wafer roto~ brush, which shows the most superior
characteristic in noise wave suppressing effe.ct among the conventional rotor
~ brushes ~reated by various kinds of methods for forming a coating Or a highly
:', resistive material thereon. Further, preliminary treatments, such as shot-
. blast or ~he like, which are always required in the highly resistive material
. ,., spraying method and the treatment of spraying nickel aluminide or the like
, to form a foundation are not required in the method according to the present.
invention. S~ch treatment is replaced by the sputter cleaning by gas ions
,: in the method of the present invention, resulting~ in a g~reat simplification of
the preliminary treatment. Additionally, an after-treutment to form silicon
oxide co~ting, SUCII as is required in the production of the silicon wafer
brush, is also unnecessary in Ille method of the present invention.
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Still further, slnce a very thin 5-15,1~ ion-plated layer shows a suffi-
.~ cient performance for suppressing noise waves, even if a rotor brush presently
:............ in use i8 treated, according to the present invention, without changing its
- present shape, the change of the discharge gap between the rotor brush and
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Ihe s~de ter i als is negligibly sm611. ThGrefore, the present invention does
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not hsve the problem that arises in the spraying method wherein consideration
~u~t be given beforehand to the thickness of the sprayed layer in planning
;, ant manufacturing.
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