JPH0584814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a combustion chamber of an internal combustion engine, and more particularly to a combustion chamber structure configured to be able to use low cetane number fuel such as alcohol or gasoline.

[Prior Art] The present applicant had previously developed a swirl combustion chamber type diesel engine (Japanese patent application 1983-
No. 193477) was proposed.

This proposal, as shown in FIG. 2, allows the fuel injection nozzle 6 to face the swirl combustion chamber 2 through the passage 4,
This injection nozzle is provided with a sub-nozzle 11 that injects fuel spray under any operating load, and a main nozzle 10 that injects fuel spray when a predetermined load is exceeded. facing the inner wall 4b on the downstream side, and furthermore, the direction of the sub-nozzle is
The fuel injected from this flows into the inner wall 2 of the swirl combustion chamber 2.
It is designed to form a fuel film that flows downstream of the swirl along the direction a, thereby achieving slow evaporative combustion.

[Problems to be Solved by the Invention] However, even with the above proposal, there was a problem that good combustion could not be obtained when a low cetane number and volatile fuel such as gasoline was used.

In other words, low cetane number/volatile fuels such as gasoline are quickly dispersed throughout the vortex combustion chamber due to the strong swirl, allowing flame propagation, especially when the injection amount is small and the engine is under low load. This is because it becomes impossible to form a proper air-fuel mixture. Incidentally, this problem regarding the air-fuel ratio occurs not only in swirl combustion chambers but also in direct injection type diesel combustion chambers that are assisted by spark plugs.

An object of the present invention is to provide a combustion chamber structure that can burn low cetane number and volatile fuel without misfire.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

That is, in a combustion chamber of an engine operated with low cetane number fuel, a fuel injection nozzle for injecting low cetane number fuel, which has a main nozzle and a sub nozzle and faces the vortex combustion chamber, is attached via a passage. The fuel injected from the main nozzle passes through the passage and directly reaches the vortex combustion chamber, and the auxiliary nozzle is provided close to the inner wall of the passage on the upstream side of the swirl generated in the vortex combustion chamber. The fuel injected from the sub-nozzle collides with the inner wall surface of the passage, becomes atomized and scattered, and is injected so as to be retained in the passage, and the fuel spray collides with the inner wall of the passage. An ignition means is provided by locating the heating section or the ignition section near the point and near the accumulated fuel vapor.

[Operation] The fuel spray injected from the sub-nozzle toward the inner wall of the passage on the upstream side in the swirl direction collides with the inner wall of the passage, atomizes and scatters, rapidly vaporizes, and stays in the passage. Therefore, if heating or ignition is performed by the ignition means, stable combustion will occur even at low rotation and low load.

That is, in the present invention, the direction of the sub-nozzle is such that the fuel spray injected from the sub-nozzle collides with the inner wall of the passage on the upstream side in the swirl direction of the passage and is scattered, and the collision causes fuel vapor to accumulate in the passage. Conventionally (Patent Application No. 58-193477)
This method forms a large amount of fuel vapor without forming a fuel film, and burns low cetane number and volatile fuels such as gasoline and alcohol without misfire.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a vortex combustion chamber 2 is formed in the cylinder head 1, and a communication passage 3 is formed below the vortex combustion chamber 2 to connect the vortex combustion chamber 2 and the cylinder of a cylinder body (not shown). has been done. Further, above the swirl combustion chamber 2, there is a cylinder head 1.
A passage 4 is formed which is opened from one side and communicates with the swirl combustion chamber 2, and a heat shield 5 is integrally accommodated in the enlarged diameter portion 4a at the upper part of the passage 4. , a fuel injection nozzle 6 is housed within the heat shield 5 .

The fuel injection nozzle 6 consists of a well-known pintokes type fuel injection nozzle, and has a main injection port 10 and a sub injection port 1.
1, and by lifting a needle valve 9 housed in the nozzle body 7 so as to be able to rise and fall, the sub nozzle 11 opens before the main nozzle 10. That is, depending on the pressure of the fuel supplied to the fuel injection nozzle 6, when the engine is running at low speeds and under low load, only the sub-nozzle 11 is opened, and when the engine is at medium-high speeds and under medium-high loads, not only the sub-nozzle 11 is opened. The main nozzle 10 is also configured to open (at medium to high speeds and medium to high loads of the engine, the flow rate of fuel supplied to the fuel injection nozzle 6 increases and the pressure acts equally on the main nozzle 10 and the sub nozzle 11). , the fuel spray is injected from both the main nozzle 10 and the auxiliary nozzle 11). Further, the nozzle diameter of the main nozzle 10 is set larger than that of the auxiliary nozzle 11, so that the fuel spray injected from the main nozzle 11 crosses the swirl S of the vortex combustion chamber 2 to the lower part of the vortex combustion chamber 2 (on the communication passage 3 side). ) is set to reach. and the main injection port 10 of the fuel injection nozzle 6
is made to face the center of the swirl combustion chamber 2 via the passage 4, and the sub-nozzle port 11 is made to face the inside of the swirl combustion chamber 2 via the passage 4. Here, the sub-nozzle 11 is
The direction is such that the fuel spray injected from this collides with the inner wall 4b of the passage 4 on the upstream side in the swirl direction, and due to this collision, most of the main stream (jet) of the fuel spray collides with the inner wall 4b. The fuel vapor layer A 1 is designed so that it is atomized and scattered, and the fuel vapor layer A ₁ generated by the atomization can be retained in the passage 4 . Note that the remainder of the main stream (jet) of the fuel spray is vaporized within the swirl combustion chamber 2.

In order to ensure fuel ignition, an ignition means 12 consisting of a spark plug or a glow plug is attached to the cylinder head 1. In the embodiment, the ignition means 12
consists of a spark plug, and this ignition means 12
is arranged so that its plug gap 12a (heating part in the case of a glow plug) is in contact with the fuel vapor layer _A1 .

Next, the operation of this embodiment will be explained.

When the engine is running at low speed and under low load, only the auxiliary nozzle 11 is opened and fuel spray is injected from this. The outside of the fuel spray is evaporated when it comes into contact with the high-temperature air in the passage 4, and the main stream (jet) of the spray is atomized by collision with the inner wall 4b of the passage 4 and scattered. Due to this, the area of contact with the air in the passage 4 is dramatically expanded, and the fuel evaporates at an accelerated pace, forming the fuel layer _A1 and staying in the passage 4. fuel vapor layer
A part of _A1 is supplied to the plug gap 12a,
A part of the fuel is also flowed downstream by the swirl S and becomes the fuel vapor layer _A2 . For this reason,
When the spark plug, which is the ignition means 12, is ignited, first the fuel vapor layer around the plug gap 12a is ignited.
A ₁ is ensured to ignite, and then the flame is propagated to the fuel vapor layer A ₁ and the fuel vapor layer A ₂ , causing them to burn rapidly.

At medium or high speeds and high loads, not only the sub-nozzle 11 but also the main nozzle 10 is opened, and the fuel spray F injected from the main nozzle 10 is evaporated while swirling inside the vortex combustion chamber 2 due to the swirl S. Therefore, a dense fuel vapor layer is generated within the swirl combustion chamber 2 as a whole. Therefore, when the ignition means 12 assists, combustion occurs rapidly.

In addition, in this example, the fuel used is
Low cetane number and volatile fuels such as gasoline and alcohol.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) At low engine speeds and low loads, gasoline,
It is possible to ignite low cetane number/volatile fuels such as alcohol, and to burn them without misfires.

(2) Since alcohol fuel can be used, low NOx emissions can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional view showing a preferred embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing a conventional combustion chamber structure. In the figure, 1 is the cylinder head, 2 is the swirl combustion chamber,
4 is a passage, 6 is a fuel injection nozzle, 10 is a main injection port,
11 is a sub-nozzle, 12 is an ignition means, A ₁ and A ₂ are fuel vapor layers, and S is a swirl.

Claims (1)

[Claims] 1 A combustion chamber of an engine operated with low cetane fuel, with main nozzle 1 facing vortex combustion chamber 2.
A fuel injection nozzle 6 for injecting low cetane fuel having a fuel injection nozzle 0 and a sub-nozzle 11 is installed through the passage 4, and the fuel injected from the main injection nozzle 10 passes through the passage 4 and directly enters the swirl combustion chamber. 2, the sub-nozzle 11 is provided close to the passage inner wall 4b on the upstream side of the swirl generated in the swirl combustion chamber, and the fuel injected from the sub-nozzle 11 flows into the passage. The fuel vapor collides with the wall surface 4b, becomes atomized, and is injected so as to be accumulated in the passage 4, and the fuel vapor is sprayed near the point of collision between the fuel spray and the passage inner wall 4b and near the accumulated fuel vapor. A combustion chamber structure characterized in that a heating section or an ignition section is located and an ignition means 12 is provided.