Ignition distributor

An ignition distributor is disclosed which comprises an input terminal, output terminals, a rotor adapted to rotate with rotation of an engine and provided at its one end with a magnet, a first electrode facing the rotor and coupled to the input terminal, a piezo-conductive plate placed on the surface of the first electrode opposite to the rotor, second electrodes formed of magnetic material and connected to the output terminals, respectively, and the second electrodes circumferentially arranged on the piezo-conductive plate. When the rotor rotates to bring the magnet below one of the second electrodes, the one second electrode is attracted to exert a pressure on the piezo-conductive plate so as to render it conductive thereby establishing an electrical connection between the input terminal and the output terminal connected to the one second electrode.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an ignition distributor for use in an internal 
combustion engine. 
2. Description of the Prior Art 
In conventional ignition distributors, spark ignition occurs in a small gap 
between two electrodes to conduct a high voltage applied to an input 
terminal to one of output terminals. Such spark ignition creates several 
difficult problems. First, it produces a noise field to have an adverse 
influence on broadcasting systems. Second, it produces undesirable gases 
such as oxides of nitrogen which accelerate corrosion of the electrodes 
and reduce their life. Third, it causes a loss of energy to be transmitted 
to ignition plugs which results in poor exhaust gas purifying performance 
and poor fuel economy. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide one quite 
satisfactory solution of the problems encountered with conventional 
ignition distributors. 
Another object of the present invention is to provide a novel and improved 
ignition distributor in which high voltage distribution is taken place 
with no spark discharge. 
According to the present invention, these and other objects are 
accomplished by an ignition distributor for use in an internal combustion 
engine, comprising an input terminal for connection to a high voltage 
source, a plurality of output terminals for connection to ignition plugs, 
respectively, a rotor adapted to rotate with rotation of the engine and 
provided at its one end with a magnet, a first electrode disposed to face 
the rotor and electrically connected to the input terminal, a 
piezo-conductive plate placed on the surface of the first electrode 
opposite to the rotor, second electrodes formed of magnetic material and 
electrically connected to the output terminals, respectively, and the 
second electrodes circumferentially arranged on the piezo-conductive plate 
for exerting a pressure on the portion of the piezo-conductive plate 
between the magnet and one of the second electrodes to render the portion 
conductive thereby making an electrical connection between the input 
terminal and the one output terminal connected to the one second electrode 
when the rotor rotates to bring the magnet below the one second electrode. 
Other objects, means, and advantages of the present invention will become 
apparent to one skilled in the art thereof from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Prior to the description of the preferred embodiments of the present 
invention, we shall briefly describe the prior art ignition distributor 
shown in FIG. 1 in order to specifically point out the difficulties 
attendant thereon. 
In FIG. 1, the reference numeral 1 designates a cam shaft extending within 
a housing 2 and coupled to a crankshaft of an engine for rotation 
therewith. The distributor comprises an insulating rotor 3 secured at its 
lower side to the cam shaft 1 and provided on its upper surface with a 
rotor electrode 4, and a distribution cap 5 secured to the housing 2 and 
provided with a center input terminal 6 and a plurality of side output 
terminals 7 which are numbered in accordance with the cylinders 
incorporated in the engine. The center input terminal 6 is electrically 
connected to the rotor electrode 4 through a carbon electrode 8 and a 
spring 9 urging the carbon electrode 8 into contact with the rotor 
electrode 4. The side output terminals 7 are electrically coupled to side 
electrodes 10, respectively. 
When a high voltage is applied from an ignition coil (not shown) through a 
high voltage cable (not shown) to the center input terminal 6, it is 
conducted through the spring 9 and the carbon electrode 9 to the rotor 
electrode 4. This causes dielectric breakdown of air in a small gap G 
between the rotor electrode 4 and one of the side electrodes 10 to 
transmit the high voltage to the one side electrode 10. The high voltage 
is then conducted through a high voltage cable (not shown) to a 
corresponding one of the ignition plugs. 
In such conventional distributors, high voltage is conducted from the rotor 
electrode 4 to one of the side stationary electrodes 10 through spark 
discharge occurring in the gap G which normally has a distance of about 1 
mm. However, such spark ignition creates several difficult problems. 
First, it produces a noise field which is spread around from the high 
voltage cable serving as an antenna to have an adverse effect on 
broadcasting systems. Second, it produces undesirable gases such as oxides 
of nitrogen which accelerate corrosion of the electrodes and reduce their 
life. Third, it causes a loss of energy to be transmitted to ignition 
plugs so that energy cannot be applied to the ignition plugs in an amount 
sufficient to reliably ignite fuel for high exhaust gas purification and 
high fuel economy. 
Referring to FIGS. 2A and 2B, there is illustrated a first embodiment of an 
ignition distributor made in accordance with the present invention. The 
ignition distributor comprises a disc-shaped stationary electrode 11 
formed of a nonmagnetic material such as aluminium and formed integrally 
with a center rod 11' which is secured to the distribution cap 5 and 
electrically coupled to the center input terminal 6. The stationary 
electrode 11 has thereon a disc-shaped piezo-conductive plate 12 which is 
formed of silicon rubber mixed with conductive metal particles so as to 
serve as a conductor having a resistance of about several tens of ohms 
when applied with a pressure above a predetermined level such as one on 
the order of 0.1 to 2 kg/cm.sup.2 and to serve as an insulator having a 
resistance of about several tens of megohms under a pressure below the 
predetermined level. A plurality of working electrodes 13 which is 
numbered in accordance with the number of the cylinders incorporated in 
the engine are positioned circumferentially and fixed on the 
piezo-conductive plate 12 such as by conductive adhesive. The working 
electrodes 13 are formed of a magnetic material such as soft iron and 
electrically connected through wires 14 to the side output terminals 7, 
respectively. The ignition distributor also comprises a rotor 15 coupled 
at its lower side to the cam shaft 1 and provided at its one end with a 
rod magnet 16. The magnet 16 may be a permanent magnet or electromagnet. 
In operation, when the rotor 15 rotates with rotation of the cam shaft 1 to 
bring the magnet 16 below one of the working electrodes 13, the working 
electrode 13 is attracted downward to exert a pressure on the portion of 
the piezo-conductive plate 12 between the working electrode 13 and the 
magnet 16 so as to render the portion conductive. Thus, the high voltage 
applied to the center input terminal 6 is conducted through the 
established circuit including the rod 11', the stationary electrode 11, 
the portion of the piezo-conductive plate 12, the working electrode 13, 
the wire 14 and the side output terminal 7 to the corresponding one of the 
ignition plug. Similarly, the high voltage applied to the center input 
terminal 6 is sequentially distributed to the ignition plugs fitted in the 
respective cylinders when the magnet 16 passes below the respective 
working electrodes 13 with rotation of the rotor 15. 
A samarium-cobalt magnet may be used as the magnet 16 to provide an 
increased attractive force so as to facilitate creation of a pressure 
sufficient to render the piezo-conductive plate 12 conductive. 
Referring to FIG. 3, there is illustrated a second embodiment of the 
present invention which differs from the first embodiment only in that the 
wires 14 are removed and replaced with coil springs 19, respectively. The 
coil springs 19 serve to electrically connect the working electrodes 13 
and also to urge the working electrodes 13 downward so as to provide a 
bias pressure on the piezo-conductive plate 12, whereby the 
piezo-conductive plate 12 can reliably be rendered conductive with a small 
attractive force. Insulating guide members 18 may be provided on the 
stationary electrode 11 for positioning the respective working electrodes 
13, which restrict horizontal movement of the working electrodes 13 and 
allow vertical sliding movement thereof. As an example, the magnet 16 is 
illustrated as taken in the form of a horseshoe magnet. 
Referring to FIG. 4, there is illustrated a third embodiment of the present 
invention which is similar to the first embodiment except that a 
stationary electrode 20 is provided for each side output terminal 7 and 
all of the working electrodes 13 are connected to the center input 
terminal through respective wires 21. In this embodiment, when the rotor 
15 rotates to bring the magnet 16 below one of the stationary electrodes 
20 to attract the corresponding working electrode 13 so as to render the 
corresponding piezo-conductive plate 12 conductive, the high voltage 
applied to the center input terminal 6 is conducted through the wire 21, 
the working electrode 13, the piezo-conductive plate 12, and the 
stationary electrode 20 to the corresponding side output terminal 7. 
Referring to FIG. 5, there is illustrated a fourth embodiment of the 
present invention which differs from the third embodiment only in that the 
wires 21 are removed and replaced with coil springs 22, respectively. The 
coil springs 22 serve to electrically connect the working electrodes 13 to 
the center input terminal 6 and also to urge the working electrodes 13 
downward so as to provide a bias pressure on the piezo-conductive plate 
12, respectively, so that the piezo-conductive plate 12 can reliably be 
rendered conductive with a small attractive force. 
By the choice of the density and size of the metal particles mixed in the 
rubber of the piezo-conductive plate to adjust the resilient force thereof 
and/or by the choice of the mass and area of each working electrode 13, 
the speed with which the piezo-conductive plate 12 changes between its 
insulating and conductive conditions can be held high even if the rotor 15 
rotates at high speeds. 
FIG. 6 illustrates a modification of the present invention, in which each 
of the working electrodes 13 is taken in the form of a permanent magnet 
and two magnets 16' and 16" different in polarity are embedded in the 
rotor 15. When the rotor 15 rotates in the arrow direction, the magnet 16' 
first attracts the working electrode 13 to place the piezo-conductive 
plate 12 in its conductive condition and then the magnet 16" repels the 
working electrode 13 to return it to its insulating condition. This 
further increases the speed with which the piezo-conductive plate 12 
changes between these two conditions. 
The working electrodes are preferably made of, but are in no way limited 
to, ferromagnetic material or may be taken in the form of permanent 
magnets as shown in FIG. 6. In the latter case, a conductive plate may be 
sandwiched between the magnet and the piezo-conductive plate, which is 
connected through a wire to the center input terminal 6 or one of the side 
output terminals 7 since permanent magnets sometimes have poor 
conductivity. 
FIG. 7 illustrates another modification of the present invention, in which 
each working electrode 13 is provided with projections 13' to increase the 
pressure exerted on the piezo-conductive plate 12. 
It is therefore apparent that there has been provided, in accordance with 
the present invention, an ignition distributor which distributes a high 
voltage to a plurality of ignition plugs with no spark discharge and thus 
is free from disadvantages attendant with spark discharge that fully 
satisfies the objects, aims and advantages set forth above.