JPS58202378A - Sparkplug for starting diesel engine - Google Patents

Abstract

PURPOSE:To prevent stray current corrosion and oxidation of an electrode and improve the starting property of an engine by allowing a sparkplug to discharge while giving high energy to the plug for a short period of time after forming the spark discharge part of the sparkplug used instead of a glow plug with titanium or a titanium alloy. CONSTITUTION:A sparkplug 11 is equipped with a central electrode 12 and a side electrode 13, and a discharge part G is formed between the both electrodes 12, 13. These electrodes 12, 13 are formed by titanium or a titanium alloy. The sparkplug 11 is attached to the wall part 4a of a vortex flow chamber 4 by means of a mounting screw part 17 such that the gap G is located near the central part of a fuel injected from a fuel injecting valve 5. By turning a starter motor after starting the igniter, the fuel to be sprayed is discharged into the vortex flow chamber 4 and a fuel chamber 3 from the fuel injecting valve 5. Then, by raising DC voltage of battery 19 to higher voltage with a DC-DC converter 18 and allowing high energy stored in a large capacity condenser 22 to be discharged by a converter output of the plug 11 via diodes 20, 21 for a short perid of time, the engine is started.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a spark plug for starting a diesel engine.

(Prior Art) As a conventional σ) diesel engine starting device, there is one shown in FIG.

In the figure, a fuel injection valve 5 is attached to a swirl chamber 4 formed further above a combustion chamber 3 formed at the top of a piston 2 in each cylinder 1 of the engine, and a glow plug 6 is attached to a threaded portion. Attached by 7. The glow plug 6 is arranged so that its heat generating portion 8 is sprayed with atomized fuel from the fuel injection valve 5, and is energized from a terminal 9 of the glow plug 6 through an air circuit (not shown). 10 is a valve.

In order to start the engine in such a conventional device, first, an electric current is applied to the glow plug 6, and the electric current is applied for several seconds to several tens of seconds to make the glow plug 6 red-hot, depending on the ambient temperature and engine water temperature at the time. After the glow plug 6 becomes red hot, the starter motor (not shown) is rotated to crank the engine while the glow plug 6 is energized, and fuel is injected from the fuel injection valve 5 into the high-temperature compressed swirl chamber 4. This started combustion and started the engine.

However, in such conventional diesel engine starting devices, combustion is started by making the glow plug 6 red hot and injecting fuel into it as described above, so it is difficult to start the engine. Before starting the ranking, it is necessary to wait several seconds to several tens of seconds for the glow plug 6 to become red-hot, which poses a problem in that it takes time to start the engine. In addition, in order to make the glow plug 6 red hot, a large current of about 10 to 15 A is normally passed from the battery for a long time as described above.
There was also the problem that the battery performance decreased and the capacity was insufficient, and this was especially noticeable at low temperatures.

Therefore, the present inventor focused on the conventional problems as described above, and developed a diesel engine starting spark plug as shown in FIG. 2, as shown in FIG. 3; The ignition plug 11 is installed in a vortex chamber, and high energy (about 0.5 to 2 J) is injected into the spark plug 11 within a short period of time (several hundred μS to several ms) using the high energy ignition device shown in FIG. 4 or FIG. A spark was used to ignite and burn the sprayed fuel indoors, allowing for a quick start, eliminating the problem of decreased battery capacity and capacity, and improving starting performance especially at low temperatures. 56-128043
This is proposed in the specification etc.

In the above proposal, various studies were attempted on the materials of the center electrode and side electrodes that form the discharge part of the spark plug for starting a decel engine. Due to the high energy injected within a certain period of time, the temperature of the electrode of the spark plug increases considerably, and therefore the material of the spark plug proposed above may have problems in terms of durability such as galvanic corrosion and oxidation. found.

That is, when the center electrode and side electrodes are formed of a nickel-iron alloy, electrolytic corrosion begins to occur after several tens of minutes to several hours of exposure. Therefore, the problem of electrolytic corrosion has been solved by using a high melting point material such as tungsten or a tungsten alloy. However, since the spark plug is installed in the swirl chamber not only at the time of starting (always), and the temperature in the combustion chamber and swirl chamber of a diesel engine usually rises to 700 to 800 degrees Celsius, tungsten and tungsten alloys cannot be used in this high-temperature oxidizing atmosphere. Oxidation progresses, and oxidation rapidly progresses to the inside of the electrode, especially when the engine is operated at full throttle and under high load.In this way, conventional electrode materials such as nickel-iron alloys and tungsten are susceptible to electrolytic corrosion and oxidation. There was a problem with durability.

(Purpose of the Invention) This invention was made by focusing on such conventional problems, and uses a spark plug instead of a glow plug, eliminates preheating time, performs starting in an extremely short time, and saves battery power. The purpose is to eliminate performance degradation and capacity shortages, greatly improve startability at low temperatures, and in particular to improve the durability of spark plug electrodes.

(Structure and operation of the invention) Therefore, the present invention is characterized in that, in an ignition plug used in place of a glow plug, the center electrode and the side electrodes (particularly the spark discharge portion) are formed of titanium or a titanium alloy.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment of the spark plug 11 for starting a diesel engine according to the present invention. In the figure, the spark plug 11 has a center electrode 12 and side electrodes 13, and a gap (discharge section) (■) is formed between the electrodes 12 and 13. It is electrically insulated from the casing 15 and connected to the high-voltage power supply terminal 16. On the other hand, the side electrode 13 is attached to the engine casing (specifically, to the wall of the vortex chamber) using a threaded portion 17. They are mechanically and electrically coupled and grounded.Therefore, when a high voltage is supplied to the high voltage power supply terminal 16, a spark discharge occurs in the gap G.

Although only one side electrode 13 is shown in the figure, the center electrode 1
A plurality of pieces (for example, 4 pieces) are provided around the gap part G.
The number of center electrodes 12 can also be increased.
By forming the gap portion ( ) in the shape of a protrusion, the durability of the electrodes 12 and 13 can be structurally improved.

The center electrode 12 and the side electrodes 3 are made of titanium or a titanium alloy. Titanium usually has a melting point of 200
It is a high melting point material with a temperature of just under 0°C.

FIG. 3 shows the state in which the spark plug 11 is installed in the swirl chamber 4 of the engine. It is mounted so as to be located near the center of the atomized fuel injected from the injection valve 5.

Therefore, the center electrode 12 and the side electrodes 13 are connected to the insulator 1
．． It is preferable that the screw portion 17 is attached through the threaded portion 17 so as to protrude from the screw portion 17.

FIG. 4 shows the configuration of one embodiment of the ignition device.

In the figure, 18 is a Dc-I)c converter that boosts the DC voltage of the batch January 9 to a DC high voltage, and the output is applied to a large capacity capacitor 22 via diodes 20 and 21 to produce approximately 0.5 to 2 J (joules). stores high energy. Reference numeral 23 denotes an ignition timing control circuit which generates an output at appropriate timing to turn on the thyristor 24. When the thyristor 21 is turned on, the ignition coil 5 and the condenser 26 act to cause the ignition plug 11 to start discharging, and then the high energy stored in the large capacitor 22 is injected into the ignition plug 11.

FIG. 5 shows the construction of another embodiment of the small fire device, in which the spark plug 11 is provided with a conventional point 27 and ignition coil path.
After that, the high energy stored in the large capacity capacitor 22 is injected into the spark plug 11 by turning on the thyristor 21.

Next, the effect of engine starting will be explained.

Activate the ignition device shown in FIG. 4 or 5 and turn the starter motor. As the engine rotates, fuel sent from a fuel pump (not shown) is injected as atomized fuel into the swirl chamber 4 from the fuel injection valve 5 at the required timing. The temperatures of the combustion chamber 3 and swirl chamber 4 are low at the time of startup (and the atomization condition of the spray is not very good, so the sprayed fuel does not immediately ignite by itself.The spray fuel does not flow into the swirl chamber 4 and the fuel chamber 3). At this time, the high energy (0
, 5 to 2 JI is injected into the spark plug 11 for a short period of time (several hundred μs to several ms) and discharged, the sprayed fuel is immediately and reliably and strongly ignited and combusted, and the engine is started.

Spark plug for diesel engine starting according to the present invention 1
The center electrode 12 and side electrodes 13 of 1 are made of titanium or titanium alloy, but with the ignition device of FIG. I couldn't see it at all. We also installed it inside the vortex chamber of a diesel engine and conducted a full-throttle, high-load test on the engine, and found that it was resistant to oxidation and had no problems.

The reason seems to be as follows. That is, even a titanium electrode or a titanium alloy electrode, being a metal, undergoes oxidation due to high-energy discharge or exposure to high-temperature oxidation conditions. However, the oxide Tie2
is formed relatively thinly only on the surface of the electrode, and the oxide film between the parentheses is hard. Therefore, this oxide film on the surface prevents oxidation from progressing to the inside of the electrode, protecting the entire electrode and improving durability.

(Effects of the Invention) As explained above, according to the present invention, instead of a tallow plug that requires a long preheating operation, an ignition plug that injects and discharges high energy within a short time is used. , it is possible to start the diesel engine instantly and reliably, eliminates the problem of decreased battery capacity and capacity shortage, and significantly improves startability at low temperatures.
By forming the center electrode and side electrodes of the spark plug from titanium or titanium alloy, it is possible to prevent electrolytic corrosion and oxidation of the electrodes, and to greatly improve the durability of the electrodes and, in turn, the spark plug. Effects can be obtained.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventional diesel engine equipped with a glow plug, Figure 2 is a front view of a spark plug for starting a diesel engine according to the present invention, and Figure 3 is a cross-sectional view of a diesel engine equipped with the spark plug shown in Figure 2. A sectional view, FIG. 4 is a block diagram of one embodiment of an ignition device for driving the spark plugs shown in FIGS. 2 and 3, and FIG. 5 is a block diagram of another embodiment of the ignition device. , 3... Combustion chamber 4... Vortex chamber 5
......Fuel injection valve 11...Spark plug for diesel engine starting 12...Center electrode 13...Side electrode 11...Insulator 15...
Housing 16... High voltage power supply terminal 17...
For installation, use the screw part 18...1. )C-L)C converter 22...Large capacity capacitor Patent applicant Nissan Motor Co., Ltd. Patent application representative Patent attorney Megumi Yamamoto - Figure 1

Claims (1)

[Claims] A diesel engine starting device is mounted in a swirl chamber of a diesel engine at a position where it is sprayed with atomized fuel injected from a fuel injection valve, and the atomized fuel is ignited and combusted by discharging between a center electrode and at least one side electrode. 1. A spark plug for starting a diesel engine, characterized in that the center electrode and the side electrodes are made of titanium or a titanium alloy.