JPH0331579A - Microwave corona discharge-type internal combustion engine igniter - Google Patents

Abstract

PURPOSE:To improve ignition performance in a small size device by providing a discharge electrode in a specified position of a wave guide for transmitting a microwave pulse to a combustion chamber in a device constructed so that a microwave is transmitted to the a combustion chamber to course microwave corona discharge, thereby igniting combustible gas. CONSTITUTION:An impulse voltage generator 21 is adapted to generate impulse voltage with a pulse width of 0.1-0.5msec in synchronization with the fuel ignition timing in a combustion chamber 25 according to the output of a distributer 20, and the output of the device 21 is applied to a microwave generator 22 such as a magnetron or the like. The thus generated microwave pulse about 300-500W is transmitted through an isolator 24 to a feeder 23 comprising a wave guide 23a, and transmitted to the interior of the combustion chamber 25. A microwave discharge is formed in the combustion chamber 25 to ignite and burn combustible gas. In this case, discharge electrodes 23b, 23b are disposed opposite to each other in a position separated by 1/4 wavelength from the terminal end portion of the wave guide 23a so as to cause microwave corona discharge between both electrodes 23b.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a microwave corona discharge type internal combustion engine ignition device, and more particularly, the present invention relates to a microwave corona discharge type internal combustion engine ignition device, and more specifically, a microwave corona discharge type internal combustion engine ignition device for burning combustible gas in an engine combustion chamber. This invention relates to a microwave corona discharge type internal combustion engine ignition system that utilizes.

[Conventional technology]

Generally, gasoline engines ignite by causing a high-voltage spark discharge using a spark plug, but in this ignition method, the high-voltage impulse generated by the ignition coil is passed through a high-tension cable to the ignition ignition with a small gap. A voltage is applied between the plug electrodes to generate a discharge, and the resulting arc heat ignites the fuel gas.

For this reason, (1) Incomplete combustion occurs because free carbon and unburned fuel caused by ignition failure significantly reduce the insulation resistance between the electrodes, which reduces the impulse voltage applied between the electrodes and reduces the energy of the arc. As a result, ignition failure continues or ignition becomes impossible.

(2) Since arc discharge with large energy is advantageous for igniting dilute fuel gas, it is necessary to improve the ignition coil for generating impulses. (3) The electromagnetic noise from high-tension cables is large, which is a major hindrance to the advancement of car electronics. (4) Fluctuations in ground potential during discharge may cause electronic equipment to malfunction. There were other problems.

Therefore, conventionally, as shown in Japanese Patent Application Laid-Open No. 57-186067, a microwave corona discharge type internal combustion engine is used, in which corona discharge is generated by microwaves in the combustion chamber of the internal combustion engine to ignite the fuel gas. An igniter has been proposed.

In the proposed ignition device, as shown in FIG. 5, a combustion chamber 3 is composed of a cylinder 1 and a piston 2,
Suction hole 1a for sucking mixed gas into the upper part of the inner wall of cylinder 1
A discharge hole 1b for discharging gas after combustion, a suction hole opening/closing valve 1c, and a discharge hole opening/closing valve 1d are provided. The piston 2 is connected to the crankshaft 4.
A crank angle sensor 5 is attached to. Further, a coaxial resonator 6 that resonates at a predetermined frequency is fixed to the upper center of the combustion chamber 3 by screws or other means. One end of the center conductor 6a of this coaxial resonator 6 is directly fixed to the wall of the resonator 6, and the other end is supported by an insulating ring 7. The tip of the center conductor 6a is made slightly thinner using a heat-resistant material, and is provided as a microwave antenna 8 so as to protrude into the combustion chamber 3.

Further, a coaxial circuit 9 is connected to the coaxial resonator 6 . A coaxial core wire 9a is provided in this coaxial circuit 9, and this coaxial core wire 9a is connected to the center conductor 6a of the coaxial resonator 6 under appropriate coupling conditions, so that most of the output from the microwave oscillator 10 is The signal is supplied to the coaxial resonator 6 via the coaxial circuit 9. The microwave oscillator 10 is operated by the output of a timing circuit 11 which uses the output from the crank angle sensor 5 as a timing signal.

Note that 12 is a power source.

In the above configuration, by supplying the output of the microwave oscillator 10 to the coaxial resonator 6 via the coaxial circuit 9, a strong electric field is generated in the microwave antenna 8 portion at the tip of the center conductor 6a of the coaxial resonator 6. A high frequency arc discharge is generated by the distribution, and the fuel gas in the combustion chamber 3 is ignited by this high frequency arc. This eliminates the problem of ignition failure or inability to ignite due to a decrease in arc energy, and also eliminates problems such as generation of electromagnetic noise by making arc discharge possible with a small amount of supplied energy.

[Problem to be solved by the invention]

However, in the conventional ignition device described above, since the microwave antenna is only placed inside the combustion chamber 3, it is difficult to ensure ignition by causing a discharge phenomenon in the compressed, high-pressure fuel gas. , it is necessary to increase the microwave power transmitted to the microwave antenna. For this reason,
This requires a microwave generator with a high output, which poses a problem of increasing the size and cost of the microwave generator and its power source.

Therefore, in view of the above-mentioned conventional problems, it is an object of the present invention to provide a microwave corona discharge type internal combustion engine ignition device that can reliably ignite with small microwave power.

[Means to solve the problem]

In order to solve the above problems, a microwave corona discharge type internal combustion engine ignition device made according to the present invention transmits a microwave pulse to a combustion chamber, causes a microwave corona discharge to be generated by the microwave pulse, and a microwave corona discharge is caused by the corona discharge. A microwave corona discharge type internal combustion engine ignition device that ignites and explodes combustible gas in a cylinder compressed by a piston, and pushes down the piston by the explosive force, and transmits the microwave pulse to the combustion chamber. A discharge electrode is formed in the waveguide at a position 1/4 wavelength of the microwave from the piston in the compression position, or the end of the internal conductor is connected to the combustion chamber. A coaxial waveguide for transmitting the microwave is connected to face the end face of the piston, and a microwave roller is connected to the end face of the piston where the end of the internal conductor is opposite to the end face of the piston in cooperation with the end of the internal conductor. It is characterized by the formation of electrodes that generate electric discharge.

[For production]

In the above configuration, the discharge electrode is formed at a position 1/4 microwave wavelength away from the piston in the compression position in the waveguide connected to the combustion chamber and transmitting microwave pulses to the combustion chamber. The maximum electric field of the standing wave is located at the electrode portion, and a small microwave power can easily cause corona discharge at the discharge electrode to reliably ignite the fuel gas.

In addition, an electrode is formed on the end surface of the piston to face the end of the internal conductor of the coaxial waveguide connected to the combustion chamber, so that it cooperates with the end of the internal conductor to generate microwave corona discharge. , microwave electric lines of force concentrate between the electrodes, creating a strong electric field and easily causing corona discharge due to dielectric breakdown.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a microwave corona discharge type internal combustion engine ignition system according to the present invention, in which 20 is a distributor, 21 is an impulse voltage generator, 22 is a microwave generator, 23 is the feeder line, 2
4 is an isolator, and 25 is a combustion chamber.

The impulse voltage generator 21 is a distributor 20
Based on the output of , an impulse voltage with a pulse width of 0.1 to 0.5 m5ec is generated in synchronization with the timing of fuel ignition in the combustion chamber 25, and this is applied to the microwave generator 22. The microwave generator 22 can be composed of a magnetron, and generates microwave pulses of 300 to 500 W when the impulse voltage from the impulse voltage generator 21 is applied between the cathode and anode of the magnetron. .

The isolator 2 absorbs the microwave pulses generated by the microwave generator 22 with an internal resistance so that power is transmitted in one direction without loss and is not transmitted in the opposite direction.
4 to the feeder line 23. The feeder line 23 is composed of a rectangular or circular waveguide, a coaxial waveguide, etc. whose end is connected to the cylinder 25a of the combustion chamber 25, and the microwave pulse is transmitted to the combustion chamber 25 via the feeder line 23. Ru.

The transmission of microwaves via the feed line 23 is best carried out in fundamental mode.

The supply of microwave pulses to the combustion chamber 25 was synchronized with the piston 25b of the combustion chamber 25 by the distributor 20, and the end of the piston 25b and the end of the feeder line 23 were at an optimal distance of ~2+11111. Since this occurs at a certain time, a strong microwave electric field is generated in the combustion chamber 25, a microwave corona discharge is formed, and the ignition of the fuel gas is realized.

The impulse voltage generated by the impulse voltage generator 21 is determined depending on the type of magnetron used. For example, in the case of the most popular magnetron for microwave ovens, the impulse voltage is 2 to 3 kV, the oscillation frequency is 2.45 GHz, and the maximum output is 1.5 kW.

2 to 4 are cross-sectional views showing various embodiments of the connection structure between the power supply line 23 and the combustion chamber 25 in FIG. 1,
In the example shown in FIG. 2, the feed line 23 is a rectangular or circular waveguide 2.
3a, and the end of the waveguide 23a is connected to the upper center of the cylinder 25a of the combustion chamber 25 while maintaining an airtight state.

Electrodes 23b and 23b with sharp tips are provided on the opposing inner wall portions of the waveguide 23a, and the electrodes 23b and 23b have sharp tips extending approximately λ,/4 (λ9; wavelength) and are provided opposite to each other at an interval of 1 to 2+11111. In order to separate the combustion chamber 25 from the atmosphere, a separator plate 23c made of a ceramic plate is fitted to the inner peripheral wall of the waveguide 23a in an airtight manner.

In this configuration, when the piston 25b comes close enough to contact the end of the waveguide 23a, that is, when a microwave pulse of 300 to 500 W is transmitted while the fuel gas is in a compressed state, the piston 25b moves to the short circuit plate. The electric field of the standing wave reaches its maximum value at the positions of the electrodes 23b and 23b, microwave corona discharge occurs between the electrodes 23b and 23b, and the fuel gas is ignited.

FIG. 3 shows another connection structure between the combustion chamber 25 and the power supply line 23. In this example, the power supply line 23 is composed of a coaxial waveguide 23d consisting of an outer conductor 23d-1 and an inner conductor 23d-2. The end of the outer conductor 23d-1 of the cough guide waveguide 23d is connected to the upper center of the cylinder 25a of the combustion chamber 25 while maintaining an airtight state. At opposing portions of the outer conductor 23d-1 and the inner conductor 23d-2 of the coaxial waveguide 23d, electrodes 23e and 23e with sharp tips are arranged at approximately λg/4 ( They are provided opposite to each other at an interval of 1 to 2 mm at the position of λ, which is the wavelength of the microwave transmitted through the waveguide. In addition, in order to separate the combustion chamber 25 and the atmosphere, the coaxial waveguide 23d has its outer conductor 23.
A separator plate 23f made of a ceramic plate is fitted in the gap between d-1 and the internal conductor 23d-2 in an airtight manner.

With the above configuration, the piston 25b is
acts as a short-circuit plate, and when the piston 25b comes close enough to contact the end of the waveguide, a corona discharge is generated between the electrodes 23e and 23e due to the microwave pulse being transmitted to the coaxial waveguide 23d at this timing. As a result, fuel gas is ignited in the combustion chamber 25.

FIG. 4 is a diagram showing a modification of FIG. 3, in which the coaxial waveguide 2
The inner conductor 23d-2 of 3d is stopped at an appropriate distance d from the end of the outer conductor 23d-1, and its tip is sharpened, and is opposed to the tip of the inner conductor 23d-2 of the piston 25b, which acts as a short circuit plate. An electrode 25c with a sharp tip is fixed to the area where the electrode 25c is attached. The tip of the internal conductor 23d-2 and the electrode 25c cooperate to form a discharge electrode, and when the piston 25b approaches the end of the coaxial waveguide 23d to the extent that it contacts the end, the distance between the discharge electrodes is 2 to 2. Make sure it is about 3mm. Note that 23g is an isolation member that separates the combustion chamber 25 from the atmosphere.

With the above configuration, the piston 25b is connected to the coaxial waveguide 23.
When a microwave pulse is transmitted to the coaxial waveguide 23d while the coaxial waveguide 23d is close enough to touch the end of d, microwave electric lines of force are concentrated between the discharge electrodes, a strong electric field is generated, and dielectric breakdown occurs. , corona discharge occurs.

The configuration shown in Figure 4 does not require a shorting plate that must be positioned in a predetermined positional relationship with respect to the wavelength, so even if a popular magnetron with a low oscillation frequency is used, the waveguide shape can be enlarged. It is preferable and can be implemented because it is not necessary.

Furthermore, even with the configuration shown in FIG. 2, if a 1 OGHz band magnetron is used, the size of the waveguide can be reduced to about 1/4.

In the configurations shown in FIGS. 3 and 4, since the feeder line is a coaxial waveguide, there are no restrictions on the diameters of the inner and outer conductors, and the diameters of the inner and outer conductors can be set to desired dimensions.

Furthermore, an electrode with a sharp tip can generate a discharge using a low-power microwave pulse, but on the other hand, the discharge causes a large amount of wear, so the electrode and the end of the internal conductor that becomes the electrode should be made of heat-resistant material such as tungsten or molybdenum. It is preferably made of a plastic material.

In the above-mentioned embodiment, since the microwave is supplied between the electrodes, the polarity does not matter, and the electric field between the electrodes changes drastically so that electrons and ions are not captured by the electrodes, causing the problem of electrode contamination. At the same time, the plasma density generated by the discharge increases, making it possible to generate a discharge with high energy density. Furthermore, since a waveguide is used and the power supply line is a closed type, there is no problem of electromagnetic noise caused by leakage of electromagnetic fields to the outside.

〔effect〕

As explained above, according to the present invention, it is possible to easily generate corona discharge with small microwave power at the discharge electrode and reliably ignite the fuel gas, so a high output microwave generator is used. It is no longer necessary to do so, and benefits such as miniaturization and cost reduction can be obtained accordingly.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a microwave corona discharge type internal combustion engine ignition system according to the present invention, FIG. 2 is a sectional view showing an embodiment of a portion of FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing a modified example of a portion of FIG. 3, and FIG. 5 is a view showing an example of a conventional device. 23a... Waveguide, 23b... Electrode, 23d...
Coaxial waveguide, 23d-1...outer conductor, 23d-2...
...inner conductor, 23e is electrode, 25...combustion chamber, 25
a...Cylinder, 25b...Piston, 25c...
·electrode.

Claims (2)

[Claims] (1) A microwave pulse is transmitted to the combustion chamber, the microwave pulse generates a microwave corona discharge, the corona discharge ignites and explodes the combustible gas in the cylinder compressed by the piston, and the explosive force causes In a microwave corona discharge type internal combustion engine ignition device configured to push down a piston, a waveguide for transmitting the microwave pulse is connected to the combustion chamber, and the microwave pulse is transmitted from the piston in a compression position into the waveguide. A microwave corona discharge type internal combustion engine ignition device, characterized in that a discharge electrode is formed at a position 1/4 wavelength away from the wave. (2) Transmit microwaves to the combustion chamber, use the microwaves to generate microwave corona discharge, use the corona discharge to ignite and explode the combustible gas in the cylinder compressed by the piston, and use the explosive force to cause the piston to explode. In a microwave corona discharge type internal combustion engine ignition device configured to be pushed down, a coaxial waveguide for transmitting the microwave is connected to the combustion chamber so that the end of the internal conductor faces the end surface of the piston, and A microwave corona discharge type internal combustion engine ignition device, characterized in that an electrode is formed on an end surface of the piston opposite to which the end of the conductor faces, and performs microwave corona discharge in cooperation with the end of the internal conductor.