JPH04179840A - Two-cycle gasoline injection engine with sub-combustion chamber - Google Patents

Abstract

PURPOSE:To obtain a good ignition and combustion regardless of the engine load, by performing gasoline injections one time in an ending half of a compression stroke in the case of a low-load operation, and two times in an ending half of a scavenging stroke, or in a beginning half of a compression stroke and in an ending half thereof in the case of a middle-load operation. CONSTITUTION:A fuel injection valve 13 and an ignition plug 12 are disposed in a sub-combustion chamber 10 communicated with a main combustion chamber 5 via an injection port 11. During a low load engine operation, in an ending half of a compression stroke in which the flow velocity of air flow is relatively high, a gasoline is injected from the fuel injection valve 13 so that the injected gasoline as a whole may substantially remain in the sub-combustion chamber 10 owing to the air flow from the port 11 to this chamber 10. Further, during a middle-load engine operation, a first gasoline injection is performed in an ending half of a scavenging stroke, or in a beginning half of the compression stroke, where the flow velocity of air flow is relatively low as compared with that during a low-load engine operation, and thereafter a second gasoline injection is performed in an ending half of the compression stroke, so that a part of the injected gasoline may flow into the chamber 5. This enable obtaining good ignition and combustion regardless of the engine load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stroke gasoline injection engine with a secondary combustion chamber.

[Conventional technology]

A two-cycle gasoline injection engine with a sub-combustion chamber, which has a sub-combustion chamber that communicates with the main combustion chamber through a nozzle, and has a fuel injection valve and a spark plug arranged in the sub-combustion chamber so that gasoline is injected from the fuel injection valve. is publicly known (Japanese Unexamined Patent Publication No. 49-1337
(See Publication No. 06). In this two-stroke engine, the sub-combustion chamber occupies most of the volume of the entire combustion chamber, and therefore, in this two-stroke engine, substantially all combustion takes place within the sub-combustion chamber.

[Problem to be solved by the invention]

By the way, in an open chamber type combustion chamber, an ignitable mixture region is formed around the ignition plug regardless of the engine load, and the area around this ignitable mixture region consists only of air when the engine is operating at low load. form an area,
If the region around the ignitable mixture region can be gradually formed into a rich mixture region as the engine load increases, good ignition can be obtained regardless of the engine load, and the engine output will increase as the engine load increases. can be increased satisfactorily. However, the ignition plug must be placed in the center of the inner wall surface of the cylinder head in order to shorten the overall distance of flame propagation from the ignition plug. It is actually difficult to collect an ignitable air-fuel mixture around the spark plug located in the center of such a wide combustion chamber.
Normally, the air-fuel mixture diffuses throughout the combustion chamber,
When the engine is operated at low load, the air-fuel mixture around the spark plug becomes diluted, making it difficult to ignite. The entire combustion is carried out in the auxiliary combustion chamber 2 as described in the above-mentioned Japanese Patent Application Laid-Open No. 49-133706.
In a cycle engine as well as in an oven chamber type combustion chamber, it is difficult to form an ignitable air-fuel mixture around the spark plug when the engine is operated at low load, and thus it is difficult to obtain good ignition.

However, in internal combustion engines equipped with an auxiliary combustion chamber that occupies about 30% to 70% of the total combustion chamber volume, the auxiliary combustion chamber is a closed space, and the auxiliary combustion chamber is located above the main combustion chamber. Because of this arrangement, it is easy to collect ignitable air-fuel mixture in the auxiliary combustion chamber during low-load engine operation.

The present invention forms an ignitable air-fuel mixture in the auxiliary combustion chamber regardless of the engine load, forms an area consisting only of air in the main combustion chamber when the engine is running at low load, and forms an area in the main combustion chamber that is made up of only air when the engine is running at medium load. The aim is to form a relatively lean mixture capable of flame propagation, thereby obtaining good ignition and subsequent good combustion.

[Means to solve the problem]

In order to achieve the above object, the present invention includes an auxiliary combustion chamber that communicates with the main combustion chamber through a nozzle, a fuel injection valve and a spark plug are arranged in the auxiliary combustion chamber, and gasoline is injected from the fuel injection valve. In a two-cycle gasoline injection engine with sub-combustion chamber material, the volume of the sub-combustion chamber is 30% of the total combustion chamber volume.
% to about 70%, and at least part of the gasoline injection direction from the fuel injector is directed toward the nozzle, so that when the engine is running at low load, the air flow flowing from the nozzle into the auxiliary combustion chamber substantially directs all injected gasoline to the auxiliary combustion chamber. Gasoline is injected from the fuel injection valve during the latter half of the compression stroke, when the airflow speed is relatively high so that it remains within the combustion chamber, and when the engine is running under medium load, the engine is kept at a low temperature so that some of the injected gasoline flows into the main combustion chamber. The first gasoline injection from the fuel injection valve is performed during the latter half of the scavenging stroke or the first half of the compression stroke, when the flow rate of the air flow is slower than during load operation, and the second gasoline injection is then performed during the latter half of the compression stroke. There is.

[For production]

During low-load engine operation, all of the injected gasoline is substantially retained within the sub-combustion chamber by the airflow flowing into the sub-combustion chamber from the nozzle, thus forming an ignitable air-fuel mixture within the sub-combustion chamber. During engine medium load operation, the first gasoline injection forms a relatively lean mixture capable of flame propagation in the main combustion chamber and the auxiliary combustion chamber, and the second gasoline injection substantially reduces the amount of gasoline injected. Since all of the fuel is retained within the sub-combustion chamber, an ignitable air-fuel mixture is formed within the sub-combustion chamber.

〔Example〕

Referring to FIGS. 1 to 3, 1 is a two-stroke internal combustion engine body, 2 is a cylinder block, 3 is a piston, 4 is a cylinder head, and 5 is a gap between the flat top surface of the piston 3 and the flat inner wall surface of the cylinder head 4. 6 is a pair of intake valves, 7 is an intake boat, 8 is a pair of exhaust valves, 9 is an exhaust boat, 1° is a sub-combustion chamber formed in the cylinder head 4, Reference numeral 11 indicates a nozzle that communicates the sub-combustion chamber IO with the main combustion chamber 5, 12 indicates a spark plug disposed within the sub-combustion chamber 10, and 13 indicates a fuel injection valve disposed at the top of the sub-combustion chamber 10.
As shown in FIG. 3, a mask wall 14 is formed on the inner wall surface of the cylinder head 4 to cover the opening of the air intake valve 6 on the exhaust valve 8 side during the period when the air intake valve 6 is substantially fully open. In the embodiment shown in FIGS. 1 to 3, the volume of the sub-combustion chamber 10 is approximately equal to the volume of the main combustion chamber 5;
The zero volume can be formed to be about 30% to 70% of the total combustion chamber volume.

FIGS. 4 and 5 show an example of the opening/closing timing of the intake valve 6 and the exhaust valve 8, and the timing of gasoline injection from the fuel injection valve 13. Note that FIG. 4 shows the engine running at low speed, and FIG. 5 shows the engine running at high speed.

In the embodiment shown in FIGS. 1 to 3, the exhaust valve 8 opens before the intake valve 6 and closes before the intake valve 6, as shown in FIGS. 4 and 5. When the intake valve 6 opens, fresh air flows into the main combustion chamber 5 from the opening of the intake valve 6 on the opposite side of the mask wall 14, and then this fresh air flows along the inner wall surface of the cylinder bore below the intake valve 6. After descending, it advances along the top surface of the piston 3 as shown by arrow W in FIG. Providing the mask wall 14 in this manner allows fresh air to flow in a loop within the main combustion chamber 5, thus achieving good scavenging. Then, a while after the piston 3 begins to rise past the bottom dead center BDC, the exhaust valve 8 closes. By the time the exhaust valve 8 closes, the opening area of the intake valve 6 has become considerably smaller. Therefore, by the time the exhaust valve 8 has closed, the air in the main combustion chamber 5 is compressed by the upward action of the piston 3. The action begins. When the compression action of the air in the main combustion chamber 5 is started and the pressure in the main combustion chamber 5 becomes higher than the pressure in the sub-combustion chamber 10, the air in the main combustion chamber 5 flows through the nozzle 11 into the sub-combustion chamber 10. begins to flow inside. The pressure difference between the compressed air pressure in the main combustion chamber 5 and the pressure in the auxiliary combustion chamber 10 gradually increases as the piston 3 rises, and this pressure difference reaches its maximum at about 30'' BTDC before top dead center.
As shown in the figure, the flow velocity V of the air flowing through the nozzle 11 from the main combustion chamber 5 to the auxiliary combustion chamber 10 gradually increases as the piston 3 rises from around the time when the exhaust valve 8 closes. The flow velocity V reaches its maximum at about 30 degrees BTDC before top dead center.

By the way, in the embodiments shown in No. 1rIIJ to No. 311ilJ, the direction of gasoline injection from the fuel injection valve 13 is directed onto the inner circumferential wall surface 11a of the injection port 11, and therefore
Figure (A), Figure 8 (A), Figure 8 (B) and Figure 9 (
As shown by F in A), gasoline is injected from the fuel injection valve 13 toward the inner circumferential wall surface 11a of the injection port 11. This injected gasoline has a relatively rod-like shape with a strong penetrating force, and when it collides with the inner peripheral wall surface 11a of the nozzle, atomization of the gasoline is promoted and the collided gasoline is scattered in all directions. In Figures 4 and 5, II indicates the gasoline injection timing when the engine is running at low load, 11 and L2 indicate the gasoline injection timing when the engine is running at medium load, and Ih indicates the gasoline injection timing when the engine is running at high load. .

As can be seen from FIGS. 4 to 6, when the engine is operating at low load, the injection action is completed at around 30° BTDC before top dead center, that is, around the vicinity where the air flow velocity V in the nozzle 11 is at its maximum. When the engine is operating at low load, the injection period 1 is relatively short, and therefore injection is performed when the air flow velocity V in the nozzle 11 is quite high. If the injection is performed when the air flow velocity V inside the nozzle 11 is quite high, as shown in FIG. The air flow 2 directed from the auxiliary combustion chamber lo into the auxiliary combustion chamber lo is prevented from entering the main combustion chamber 5. Therefore, at this time, the injected gasoline F is retained within the sub-combustion chamber 10, and a homogeneous ignitable air-fuel mixture is formed within the sub-combustion chamber 10, as shown in FIG. 7(B). On the other hand, at this time, the main combustion chamber 5 is filled with air only.
In reality, it is filled only with air containing residual burnt gas. The ignitable homogeneous air-fuel mixture thus collected in the sub-combustion chamber 10 is ignited by the ignition plug 12,
As a result, good ignition and subsequent good combustion are obtained.

Next, a method of injecting gasoline during engine medium load operation will be explained. As shown in FIGS. 4 to 16, during engine medium load operation, gasoline injection is performed in two parts, and the fuel injection valve 13 is injected in two parts during the second half of the scavenging stroke or the first half of the compression stroke when the air flow velocity V in the nozzle 11 is relatively slow. The first gasoline injection work will be carried out. If injection is performed when the air flow velocity V in the nozzle 11 is slow as described above, the injected gasoline F will be scattered in all directions after colliding with the nozzle inner circumferential wall surface 11a, as shown in FIG. 8(A). Since the axial direction of the nozzle inner circumferential wall surface 11a is obliquely inclined with respect to the axis of the cylinder block 2, some of the gasoline F scattered in all directions enters the main combustion chamber 5, and the gasoline F scattered in all directions enters the main combustion chamber 5. The remaining portion enters the sub-combustion chamber 10. By the way, as described above, the air W (see FIG. 3) flowing in a loop within the main combustion chamber 5 during the scavenging stroke generates a swirling flow X that swirls within the vertical plane within the main combustion chamber 5. The gasoline F that has entered the main combustion chamber 5 is caused by this swirling flow
diffused within. On the other hand, the gasoline F that has entered the sub-combustion chamber 10 is diffused into the sub-combustion chamber 5 by an air flow Z directed into the sub-combustion chamber 10 from the nozzle 11, which is gradually increased in force as the piston 3 rises.

In this way, a uniform air-fuel mixture is formed in the main combustion chamber 5 and the sub-combustion chamber 10 as shown in FIG. 8(B). Note that gasoline injection is performed in two parts, so the first
The air-fuel mixture formed in the main combustion chamber 5 and the sub-combustion chamber 10 by the second gasoline injection 11 is a fairly lean air-fuel mixture.

Next, as shown in FIG. 8(B), the second gasoline injection 1+a2 is performed in the latter half of the compression stroke.

This is the second gasoline injection ■. 2 is carried out when the air flow velocity V in the nozzle 11 is quite high, as is the case when the engine is running at low load, so the injected gasoline F is mainly combusted by the air flow 2 heading from the nozzle 11 into the sub-combustion chamber 10. Room 5
Intrusion into the interior is prevented.

Therefore, the gasoline F injected in the second gasoline injection 172 is retained within the sub-combustion chamber 10.

In this way, as shown in FIG. 8(C), a homogeneous air-fuel mixture that can be ignited is formed in the sub-combustion chamber 10, and a relatively lean air-fuel mixture that is capable of flame propagation is formed in the main combustion chamber 5. The result is good ignition and subsequent good combustion.

Next, a method of injecting gasoline during high engine load operation will be explained. As shown in FIGS. 4 to 6, during high-load engine operation, gasoline injection 1h is performed from the fuel injection valve 13 during the latter half of the scavenging stroke or the first half of the compression stroke, when the air flow velocity V in the nozzle 11 is relatively slow. BTDC10 before dead center
The injection action is completed at about 5°. If injection is performed when the air flow velocity V in the nozzle 11 is slow as described above, a portion of the injected gasoline F will enter the main combustion chamber 5 as shown in FIG. 9(A). As shown in FIGS. 9A and 9B, the gasoline F that has entered the main combustion chamber 5 is diffused into the main combustion chamber 5 by the swirling flow X. On the other hand, the gasoline F that has entered the sub-combustion chamber 10 is diffused into the sub-combustion chamber 10 by an air flow Z directed into the sub-combustion chamber 10 from the nozzle 11, which is gradually increased in force as the piston 3 rises. In this way, a large amount of gasoline injected during high-load engine operation is almost uniformly diffused into the sub-combustion chamber 10 and the main combustion chamber 5. As a result, as shown in FIG. 9(C), an ignitable air-fuel mixture is formed in the sub-combustion chamber 10, and an almost equally rich air-fuel mixture is also formed in the main combustion chamber 5. In this way, good ignition and subsequent good combustion with a high air utilization rate can be obtained, and the required high engine output can be obtained.

〔Effect of the invention〕

During low-load engine operation, ignitable air-fuel mixture is collected in the auxiliary combustion chamber, so that good ignition and subsequent good combustion can be achieved. During medium load engine operation, an ignitable mixture is formed in the auxiliary combustion chamber, and a relatively lean mixture capable of flame propagation is formed in the main combustion chamber, resulting in good ignition and high air utilization. You can get a good combustion.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the two-stroke engine taken along line I-I in Figure 2, Figure 2 is a bottom view of the cylinder head in Figure 1, and Figure 3 is when the piston is at bottom dead center. ■ in Figure 2 of
- Figure 4 is a diagram showing the opening timing of the supply and exhaust valves and gasoline injection timing when the engine is running at low speeds, and Figure 5 is a diagram showing the opening timing of the supply and exhaust valves and the timing of gasoline injection when the engine is running at high speeds. A diagram showing the valve opening timing and gasoline injection timing. Figure 6 is a diagram showing the relationship between the crank angle and the flow velocity of air flowing through the nozzle. Figure 7 is a diagram showing the relationship between the crank angle and the flow velocity of air flowing through the nozzle. Figure 7 is a diagram showing the main combustion chamber and secondary combustion during low engine load operation. Figure 8 is a diagram to explain the interior of the main combustion chamber and auxiliary combustion chamber during medium load operation of the engine. Figure 9 is a diagram to explain the interior of the main combustion chamber and the auxiliary combustion chamber during high engine load operation. FIG. 3 is a diagram for explaining the inside of the sub-combustion chamber. 5... Main combustion chamber, 10... Sub-combustion chamber, 11.
...Nozzle port, 12... Spark plug, 13... Fuel injection valve.

Claims (1)

[Claims] A sub-combustion chamber that communicates with the main combustion chamber through a nozzle,
In a two-cycle gasoline injection engine with a sub-combustion chamber in which a fuel injection valve and a spark plug are disposed in the sub-combustion chamber and gasoline is injected from the fuel injection valve, the volume of the sub-combustion chamber is set to 30% of the volume of the entire combustion chamber. % to about 70%, and at least a part of the gasoline injection direction from the fuel injector is directed toward the nozzle, and when the engine is running at low load, the air flow flowing from the nozzle into the auxiliary combustion chamber effectively covers all the injected gasoline. Gasoline is injected from the fuel injection valve during the latter half of the compression stroke when the flow velocity of the air flow is relatively high so that the airflow remains in the auxiliary combustion chamber, and part of the injected gasoline flows into the main combustion chamber during engine medium load operation. The first gasoline injection from the fuel injection valve is performed during the latter half of the scavenging stroke or the first half of the compression stroke, when the flow velocity of the air flow is slower than during low-load operation, and the second gasoline injection is then performed during the latter half of the compression stroke. Two-stroke gasoline injection engine with auxiliary combustion chamber.