JPH0746733Y2 - Spark assist type alcohol engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a spark assist type alcohol engine, and more particularly to a spark assist type alcohol engine which assists ignition by a spark plug.

(Prior Art) Among internal combustion engines that use alcohol fuel, in particular, a spark assist alcohol engine based on a diesel engine is known.

In this engine, intake air in the combustion chamber is highly compressed, and alcohol is sprayed from the fuel injection valve, and at this time, a spark plug is driven to assist ignition, and ignition is performed accurately. One example is shown in FIG. In this case, the fuel injection valve 1 has its plurality of injection ports located substantially in the center of the cavity 3 of the piston 2 near the top dead center, and collides the spray flow 5 with the inner peripheral wall 4 of the cavity 3 to atomize and ignite the fuel. Is promoting.

Further, the spark plug 6 used here has its electrode projecting relatively large into the combustion chamber, and this electrode is directly opposed to the fuel spray flow 5 from the fuel injection valve to perform the ignition process. .

FIG. 6 shows an example of the thermal efficiency characteristics of such a spark assist type alcohol engine when the injection amount is 120 mm ³ / st, for example. As is clear from this, by operating the injection timing and the ignition timing, the thermal efficiency can be maintained in the optimum region A.

(Problems to be solved by the invention) However, when the spark plug is largely projected to the combustion chamber side as described above, the wear of the electrode is apt to proceed and the durability thereof is apt to cause a problem.

Furthermore, if an attempt is made to optimize the thermal efficiency of the engine, there is a defect area immediately after the optimum area A, that is, a misfire area B, which may cause misfire if the control accuracy is not kept at a high level, which is a problem. Was there.

An object of the present invention is to provide a spark assist type alcohol engine with stable ignition performance.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention sprays fuel from a fuel injection nozzle into high pressure gas in a combustion chamber pressurized in a compression stroke, and The part is configured to be ignited by a spark plug to enter a combustion stroke, wherein the spark plug has an electrode facing the combustion chamber, located inside the cylinder head or near the bottom surface of the cylinder head.
A heat-resistant cap is attached to the combustion chamber facing end position of the spark plug, and an ignition chamber accommodating the electrode of the spark plug is formed in the heat-resistant cap, and a partition wall for isolating the ignition chamber from the outside is formed, And a downstream of the swirl inside the combustion chamber and the fuel spray inlet for guiding a part of the fuel spray flow into the ignition chamber so as to collide with the inner wall surface of the heat-resistant cap below the electrode by opening to the injection nozzle side. Only the flame outlet located at the side facing portion is formed.

(Operation) The electrode of the spark plug facing the combustion chamber is located in the cylinder head or near the lower surface of the cylinder head, and a heat-resistant cap is attached to the end of the spark plug facing the combustion chamber.
Since the ignition chamber in the heat resistant cap is not affected by the external air flow, the ignition chamber can be kept at a relatively high temperature and the wear of the electrode can be reduced. Since the fuel spray inlet that guides a part of the fuel spray flow into the ignition chamber to collide with the inner wall surface below and the flame outlet located at the downstream facing portion of the swirl in the combustion chamber are formed, the fuel spray inlet leads to the ignition chamber. The fuel that directly collided with the wall surface is atomized, the vaporization of the fuel spray is promoted by the wall surface of the ignition chamber that is at a high temperature, a mixture with good ignitability is generated, and this mixture is easily ignited by the neighboring electrodes, The flame from the flame outlet can be used as the ignition source for other air-fuel mixture.

(Example) The spark-assist type alcohol engine shown in FIG. 1 is based on a well-known diesel engine.
The overall schematic structure is shown in FIG.

This engine has a cylinder block 10 and a cylinder head 11
A cylinder liner 13 for accommodating the piston 12 is integrally fitted inside the cylinder block 10.

The piston 12 slides up and down by the action of the reciprocating rotary link system C on the crank chamber side (not shown), and the combustion chamber 14 can be compressed at a relatively high compression rate. A cavity K is formed on the top surface of the piston 12, and this portion can form the main part of the combustion chamber 14 at the top dead center position of the piston.

A supply / exhaust port opened / closed by a supply / exhaust valve (not shown) is formed in the cylinder head 11, and the fuel injection valve 15 and the spark plug 16 are respectively provided at positions that do not interfere with the supply / exhaust port and face the cavity K. It is installed.

The fuel injection valve 15 has a plurality of injection ports, which are arranged on the plane intersecting the valve center line 1 and are circumferentially spaced apart from each other at a required distance (see FIG. 3).

A spark plug 16 is provided opposite to one of the fuel injection flows from the injection port of the fuel injection valve 15. The spark plug 16 includes an insulator 161, a mounting portion 162 that covers the tip of the insulator 161, and is screwed into a cylindrical cap holder 17 that is press-fitted into the cylinder head. It is composed of an electrode 163 to be connected.

The cap holder 17 has a heat-resistant cap 19 integrally attached to the tip thereof, which accommodates the electrode 163 and reaches a position where the tip interferes with one of the spray flows 18 from the fuel injection valve 15.

The heat-resistant cap 19 is provided with a partition wall made of heat-resistant metal having a predetermined thickness, and is formed into a cap shape as a whole, and the electrode 16 is provided inside thereof.
An ignition chamber 22 that accommodates 3 is formed. The heat-resistant cap 19 may be made of ceramic (silicon nitride, etc.).
May be formed by A fuel spray inlet 20 is provided at a part of the partition wall of the heat-resistant cap 19, that is, a position directly facing one of the spray flows 18, and a flame outlet 21 (at a downstream facing position in the swirl direction S in the combustion chamber 14). Here, two are formed).

Such a spark assist type alcohol engine repeats driving as a well-known four-cycle diesel engine. In particular, when the final region of the compression process is reached, as shown in FIG. 6, the fuel injection valve 15 injects fuel at a predetermined timing p, and the spark plug 16 performs ignition processing at a predetermined ignition timing.

Here, one of the spray flows 18 from the fuel injection valve 15 reaches the inside of the ignition chamber 22 from the fuel spray inlet 20 and collides with the inner wall surface of the heat resistant cap 19. At this time, the upper surface of the inner wall surface of the heat-resistant cap 19 faces the direction of the spray flow 18 at an obtuse angle, and the fuel spray after the collision is scattered toward the electrode 163 side. At this time, the temperature of the ignition chamber 22 is higher than that of the outside thereof (because the heat-resistant cap itself can block the inflow of airflow into the ignition chamber), and therefore the electrode 163
A high-concentration air-fuel mixture having a good ignitability is generated and supplied to the vicinity, and the spark plug 16 is ignited while the air-fuel mixture is present, so that ignition can be easily performed.

Due to this, ignition combustion occurs in the ignition chamber 22, and a flame is ejected into the combustion chamber 14 from the two flame outlets 21 based on the thermal energy, and this becomes a flame of unburned gas and propagates to the entire combustion chamber for ignition. Combustion is promoted.

In this way, in this alcohol engine, the spray flow reaching the ignition chamber 22 is first ignited while being kept under conditions of good ignitability.
Ignition and combustion of the entire combustion chamber can be easily performed by using the generated flame as the ignition source. Therefore, when the engine ignition timing is set in the region A (see FIG. 6) where the thermal efficiency is highest and the engine is operated, the actual ignition timing is erroneously set to the conventional ignition timing because the ignition timing control accuracy is low. Misfire area B
Even if it shifts a little to the side, the alcohol engine here has improved ignitability, so it escapes misfires and can continue stable driving. Furthermore, since the electrode 163 is retained at the position retracted from the combustion chamber and protected by the heat-resistant gap, its durability is improved.

FIG. 4 shows another embodiment of the present invention. The spark-assisted alcohol engine here has a heat-resistant gap of 19
1 is the same as that shown in FIG. 1 except that the inner peripheral walls are different in shape from each other, and the description of the overlapping portions is omitted here.

The heat-resistant gap 19a used here has a fuel spray inlet 20 at a position directly facing one of the spray flows 18 that is a part of the side wall thereof, and further has a flame outlet 21 at a downstream facing position in the swirl direction S in the combustion chamber 14. Each of them is provided with a rib 23 projecting annularly at the center of its inner peripheral wall.

By adopting such a configuration, the fuel flow injected into the ignition chamber 22 collides with the inner peripheral wall at one end, further collides with the rib 23 at the upper position and is scattered, and the mixed particles are refined. Become. Therefore, the air-fuel mixture around the electrode 163 in the ignition chamber 22 maintains a good ignitability state and is easily ignited by the spark plug 16, and the flame generated thereby serves as a flame to facilitate the air-fuel mixture in the combustion chamber. Can be burned. Also in this case, the same operational effect as that of the spark assist type alcohol engine of FIG. 1 can be obtained.

Further, the spark plug 16b having the heat-resistant gap 19b as shown in FIG. 1 can be attached to the engine adopting the wall collision combustion system as shown in FIG. 5 to improve the ignitability thereof.

(Effect of the Invention) As described above, in the present invention, the electrode of the spark plug facing the combustion chamber is located inside the cylinder head or near the lower surface of the cylinder head, and the heat-resistant gap is attached to the end of the spark plug facing the combustion chamber. Since the ignition chamber in the heat resistant cap is not exposed to the inflow of the external air flow, the ignition chamber can be kept at a relatively high temperature, the wear of the electrodes can be reduced, and the durability of the electrodes can be improved.

Further, at the fuel spray inlet for guiding a part of the fuel spray flow into the ignition chamber so as to collide the fuel spray flow with the inner wall surface below the electrode of the heat-resistant cap by opening to the injection nozzle side, and at the downstream facing portion of the swirl in the combustion chamber. Since the flame outlet located is formed,
The fuel directly impinging on the wall surface of the ignition chamber from the fuel spray inlet is atomized, and the vaporization of the fuel spray is promoted by the wall surface of the ignition chamber, which is at a high temperature, and a mixture with good ignitability is generated. With this, it is possible to ignite more easily, and the flame from the flame outlet can be used as the flame of another air-fuel mixture. Therefore, the durability of the electrode is improved, and a spark assist type alcohol engine having a good ignition property can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a spark assist type alcohol engine as an embodiment of the present invention, FIG. 2 is an overall schematic configuration diagram of the same engine, and FIG. 3 is a plan sectional view of a combustion chamber of the same engine. FIG. 4 is a side sectional view of a main part of a spark assist type alcohol engine as another embodiment of the present invention,
FIG. 5 is a schematic side sectional view of a spark assist type alcohol engine as another embodiment of the present invention, FIG. 6 is a characteristic diagram of injection timing-ignition timing of a conventional engine, and FIG. 7 is a main part side of a conventional engine. FIG. 15 ... Fuel injection valve, 16 ... Spark plug, 163 ... Electrode, 17 ... Gap holder, 18 ... Spray flow, 19 ... Heat-resistant gap, 20 ... Fuel spray inlet, 21 ... Flame outlet, 22
...... Ignition chamber, S ... Swirl.

Claims (1)

[Scope of utility model registration request] 1. A structure in which fuel is sprayed into a high-pressure gas in a combustion chamber pressurized in a compression stroke from an injection nozzle and a part of the fuel spray flow is ignited by a spark plug to enter a combustion stroke. In the spark-assist type alcohol engine, the spark plug has electrodes facing the combustion chamber,
Located in the cylinder head or near the lower surface of the cylinder head, a heat resistant cap is attached to the end of the spark plug facing the combustion chamber, and an ignition chamber accommodating the electrode of the spark plug is formed in the heat resistant cap. A partition wall is formed to isolate the ignition chamber from the outside, and one partition of the fuel spray stream is opened in the partition wall so as to collide the fuel spray stream with the inner wall surface of the heat-resistant cap below the electrode. A spark-assist type alcohol engine, characterized in that only a fuel spray inlet for guiding the portion into the ignition chamber and a flame outlet located at a downstream facing portion of the swirl in the combustion chamber are formed.