JP2987997B2 - Subchamber type combustion chamber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subchamber combustion chamber having a subchamber formed in a cylinder head.

[0002]

2. Description of the Related Art Conventionally, a combustion chamber of an engine is represented by a direct injection type and a sub-chamber type. The direct injection combustion chamber achieves mixing of fuel and air by the injection energy of the fuel injected from the fuel injection nozzle and swirl formed in the combustion chamber to form a combustible air-fuel mixture. The sub-chamber type combustion chamber achieves mixing of fuel oil droplets and air by a high swirl formed in the sub-chamber to form a combustible air-fuel mixture, but forms a high swirl in the sub-chamber and heat transfer. There is a problem that heat loss increases due to an increase in area, and further, there is a problem that throttle loss due to the communication hole increases when air flows into the sub chamber.

Conventionally, an insulated engine having a sub chamber has been developed for the purpose of improving combustion of the insulated engine. For example, Japanese Patent Application No. 1-252277 filed by the present applicant discloses a sub-chamber engine. The sub-chamber type heat-insulated engine includes a sub-chamber having a heat insulating structure formed in a cylinder head, a communication hole having a heat insulating structure communicating the sub-chamber with the main chamber, a multi-injection fuel injection nozzle arranged in the sub-chamber, and a piston. A protruding portion is provided on the piston head which protrudes into the communication hole near the top dead center.

Further, Japanese Patent Application No. Hei.
No. 68544 discloses an insulated subchamber diesel engine. The heat-insulated sub-chamber diesel engine includes a sub-chamber wall that forms a spherical sub-chamber of a heat-insulating structure provided in a cylinder head, and is formed at a cylinder-facing central portion of the sub-chamber wall and includes the sub-chamber and the main chamber. A communication hole communicating therewith, a lip portion formed in a peripheral portion where the communication hole opens to the sub-chamber and protruding into the sub-chamber, and a sub-chamber arranged at the upper center of the sub-chamber facing the communication hole; The fuel injection nozzle has a multi-injection hole for injecting fuel downward from above the inner wall surface.

[0005]

Generally, in a sub-chamber engine, the intake air flowing into the sub-chamber from the main chamber through the communication hole to the sub-chamber has a predetermined value regardless of the engine operating state. There is no adjustment. When the engine operating state is high load, the inflow speed of the intake air flowing through the communication hole from the main chamber side is increased to generate a strong swirl in the sub-chamber, and the fuel and air injected from the fuel injection nozzle are mixed with each other. It is necessary to promote mixing to promote combustion. However, when the operating state of the engine is a partial load, if the inflow speed of the intake air flowing from the main chamber through the communication hole is high, heat loss in the sub-chamber as described above,
There is a problem in that gas flow loss and the like increase, fuel efficiency deteriorates, and engine performance deteriorates.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and a sub-chamber in which a fuel injection nozzle for injecting fuel is disposed is formed in a cylinder head, and a main chamber is provided on a piston head side, that is, on a cylinder side. In particular, a gas injection nozzle for injecting gas into the sub-chamber is arranged, and when the engine is partially loaded, the gas is injected from the gas injection nozzle and collides with the intake air to reduce the inflow air velocity, thereby reducing the inflow air velocity. An object of the present invention is to provide a sub-chamber type combustion chamber capable of reducing gas flow loss and heat loss in a room and improving fuel efficiency.

[0007]

The present invention is configured as follows to achieve the above object. That is,
The present invention provides a sub-chamber formed in a cylinder head and having a fuel injection nozzle for spraying fuel, a piston reciprocating in a cylinder constituting a main chamber, and a sub-chamber formed in the cylinder head communicating with the cylinder side. In a sub-chamber combustion chamber having a communication hole, a gas injection nozzle arranged in the sub-chamber for injecting gas in a direction opposite to air flowing into the sub-chamber from the communication hole, a load sensor for detecting an engine load, And a controller that controls the injection of gas from the gas injection nozzle toward the intake air in response to a partial load signal from the load sensor.

The subchamber-type combustion chamber has a projection extending from the piston head surface of the piston and protruding into the communication hole near the top dead center to reduce the passage area of the communication hole. is there.

[0009]

The sub-chamber combustion chamber according to the present invention is constructed as described above, and operates as follows. That is, the sub-chamber combustion chamber includes a gas injection nozzle disposed in the sub-chamber for injecting gas in a direction opposing air flowing into the sub-chamber through the communication hole, a load sensor for detecting an engine load, and the load sensor. A controller that controls the gas injection nozzle to inject gas toward the intake air in response to the partial load signal by the gas injection nozzle, so that the gas is injected from the gas injection nozzle against the intake air during the partial load, The air is disturbed to reduce the incoming air velocity, thereby reducing heat loss, gas flow loss, etc., and improving fuel economy. Further, when the engine is under a high load, the gas is not injected from the gas injection nozzle, so that the inflow air velocity is increased, and the combustion can be promoted.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sub-chamber type combustion chamber according to the present invention will be described below with reference to the drawings. First, an embodiment of a sub-chamber type combustion chamber according to the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing an embodiment of a sub-chamber type combustion chamber according to the present invention and showing a state when an engine is partially loaded, and FIG. 2 is a view showing the sub-chamber type combustion chamber of FIG. It is sectional drawing which shows the state of.

This sub-chamber type combustion chamber is applied to a diesel engine, and includes a cylinder block 14, a cylinder head 7 fixed to the cylinder block 14 and having an intake port 25 and an exhaust port 26, and a cylinder head 7. Sub-chamber 2 with heat insulation structure formed, cylinder block 14
Piston 1 reciprocating in cylinder 18 formed in
7, a cylinder chamber 15 formed by a lower surface of a cylinder head, a cylinder 18 and a top surface of a piston head, a fuel injection nozzle 6 opening a multi-injection hole 16 in a sub chamber 2 and a piston 17
The main chamber 1 includes a cavity 20 formed in the piston head 4 of the first embodiment. When the sub-chamber 2 is configured to have a heat-insulating structure, the sub-chamber wall 3 is made of, for example, ceramics, heat-resistant metal, etc., which are disposed in the concave portion 21 formed in the cylinder head 7 and have high heat resistance and heat insulation. It is composed by producing. Similarly, when the main chamber 1 is configured to have a heat-insulating structure, the main chamber 1 is formed by manufacturing ceramics, heat-resistant metal, or the like having excellent heat resistance and heat insulating properties. The sub chamber wall 3 is
It is fixed to the cylinder head 7 with a mounting bracket or the like. A heat insulating air layer or the like may be formed between the outer surface of the sub-chamber wall 3 and the inner surface of the concave portion 21 of the cylinder head 7 to improve the degree of heat insulation of the sub-chamber 2. The lower surface of the sub-chamber wall 3 constitutes a part of the cylinder head lower surface 19, and the sub-chamber 2 formed in the cylinder head 7 is formed in the piston head 4 at the center of the lower surface of the sub-chamber wall 3. A communication hole 9 is formed facing the chamber 1. In addition, the sub-chamber 2 has a structure in which air is disturbed in the sub-chamber 2 by pushing the intake air in the figure. However, the sub-chamber 2 is not limited to this structure, and the sub-chamber structure can be configured as a swirl chamber. It is. The intake port 25 is provided with an intake valve 27, and the exhaust port 26 is provided with an exhaust valve 28.

In this sub-chamber type combustion chamber, the fuel injection nozzle 6 arranged in the sub-chamber 2 has a multi-injection hole 16 formed in the circumferential direction of the nozzle body so as to spray fuel radially into the sub-chamber 2. Have. The fuel injection nozzle 6 is disposed downward from the center in the sub-chamber 2, and the multiple injection holes 16 are open toward the peripheral wall of the sub-chamber 2. In other words, the inside of the sub-chamber 2 is formed in a substantially symmetrical shape with respect to the nozzle axis of the fuel injection nozzle 6. A cavity 20 formed in the piston head 4 of the piston 17 constitutes the main chamber 1, and the main chamber 1 is formed with a communication hole 9 formed in the cylinder head 7.
Is located in a facing state.

In the center of the cavity 20 formed in the piston head 4, there is formed a projecting portion 5 projecting from the upper surface 22 of the piston head and penetrating through the center of the communication hole 9 near the top dead center of the piston. I have. The protruding portion 5 extends upward and protrudes from the bottom surface 23 at the center of the cavity 20 of the piston head 4. Since the protruding portion 5 is a portion having a high thermal load exposed to high-temperature combustion gas, it is preferable that the protruding portion 5 be made of ceramics having high heat resistance and high temperature strength. In the figure, the protrusion 5
Although the upper surface is formed in a flat surface, the upper surface is not limited to the flat surface and may be formed in a shape having a rounded upper portion. That is, the protrusion 5 forms an annular passage 13 between the inner wall surface of the communication hole 9 and the side wall surface of the protrusion 5 by protruding into the communication hole 9, and passes through the annular passage 13 from the sub chamber 2. The configuration is such that the combustion gas that is blown out passes through a passage having a reduced passage area, and increases in speed and flows out to the main chamber 1 at high speed. Accordingly, the passage of the communication hole 9 is formed in an annular shape and reduced by the protrusion 5 protruding into the communication hole 9 near the piston top dead center, and the communication hole 9 is formed by the protrusion 5 coming out of the communication hole 9. Passage area expanded,
The passage area of the communication hole 9 forms a passage area variable passage whose passage area changes in accordance with the reciprocating motion of the piston 17.

This sub-chamber type combustion chamber has the following features in the above configuration. That is, this sub-chamber combustion chamber
A gas injection nozzle 8 disposed in the sub-chamber 2 for injecting gas in a direction opposing air flowing into the sub-chamber 2 from the communication hole 9;
A load sensor 12 for detecting an engine load, and a controller 10 for controlling the gas injection from the gas injection nozzle 8 toward the intake air in response to a partial load signal from the load sensor 12 are provided. The gas injection nozzle 8 is provided with the surge tank 1
1 is to inject the air sent from 1 into the sub-chamber 2. In the surge tank 11, for example, air sent from a turbocharger compressor is stored,
Alternatively, air supplied from a separately provided compressor is stored. The gas injection nozzle 8 is configured to inject air so as to oppose a part of the annular airflow that is sucked from the main chamber 1 side through the annular passage 13. . Therefore, the gas injection nozzle 8
By causing air to collide with the annular air flow, the annular air flow of the intake air is disturbed, and the effect of reducing the inflow air velocity is achieved. By reducing the air flow in the sub-chamber 2, the heat flow from the wall of the sub-chamber 2 to the cylinder head 7 side is suppressed, heat loss, gas flow loss, etc. are reduced, and deterioration of fuel efficiency is suppressed. it can. The engine load L is detected by the load sensor 12. The load sensor 12 can detect the engine load L by, for example, detecting the amount of depression of an accelerator pedal or detecting the flow rate of fuel injected from the fuel injection nozzle 6.

Next, the operation of the sub-chamber type combustion chamber will be described. In the combustion cycle of this sub-chamber type combustion chamber, since the protruding portion 5 does not protrude into the communication hole 9 up to near the top dead center of the compression stroke, the passage area of the communication hole 9 is not reduced, The intake air sucked into the sub-chamber 2 from the main chamber 1 side smoothly flows through the communication holes 9 without receiving a throttle loss. When the protrusion 5 of the piston 17 protrudes into the communication hole 9 in the latter half of the compression stroke near the piston top dead center, an annular passage 13 is formed between the inner wall surface of the communication hole 9 and the side wall surface of the protrusion 5. , The passage area of the communication hole 9 is reduced, and the intake air is pushed into the sub-chamber 2 so that the sub-chamber 2 is pressed.
A strong annular pushing flow is generated inside. In this state, as indicated by the arrow, the fuel spray injected from the fuel injection nozzle 6 into the sub-chamber 2 achieves good mixing with the flowing air in the sub-chamber 2 to perform fuel-rich primary combustion. Become.

Next, the combustion cycle of the sub-chamber type combustion chamber shifts to the expansion stroke, and in the early stage of the expansion stroke, the combustion gas composed of the air-fuel mixture and the flame from the sub-chamber 2 emits the projecting portion 6 formed on the piston head 4. Flows out at a high speed along the side surface 8 of the fuel cell, but as the protrusion 5 comes out of the communication hole 9, the passage area increases, and the combustion gas flows out of the sub-chamber 2 to the main chamber 1 at a stretch. Therefore, the mixture of the combustion gas and the fresh air existing in the main chamber 1 in the main chamber 1 is promoted, and the mixing of the flame and the air is achieved in a short time, and the secondary combustion is performed favorably to completely burn. To complete combustion.

This sub-chamber type combustion chamber operates as described above, but has the following features in particular. In particular, with reference to FIG. 3, the operation of the sub-chamber type combustion chamber will be described.
FIG. 3 is a processing flowchart for explaining one embodiment of the operation of the sub-chamber type combustion chamber according to the present invention. By driving the engine, the engine load L is detected by the load sensor 12 (step 40). The load signal detected by the load sensor 12 is input to the controller 10 and the controller 1
0 load L ₀ of the engine load L is preset is necessary to inject air toward the intake air from the gas injection nozzle 8
It is determined whether the state is smaller (step 41). When the engine load L detected by the load sensor 12 is smaller than the preset load L ₀ , the engine is in a partial load state, and the gas injection nozzle 8 is operated just before the top dead center of the compression stroke to move to the sub chamber 2. Air is injected to the intake air (step 42), and control is performed to reduce the inflow air velocity (step 43). When the air is injected from the gas injection nozzle 8 against the intake air flowing into the annular state to collide with the intake air, the intake air is disturbed and the velocity of the inflow air decreases,
The fuel is injected from the fuel injection nozzle 6 in a state where the air flow is reduced, and the injected fuel is ignited and burns to perform fuel-rich primary combustion.
And the air velocity is reduced by the air blown out from the gas injection nozzle 8, so that heat loss, gas flow loss and the like are reduced.

Further, in step 41, is greater than the load L ₀ of the engine load L is preset detected by the load sensor 12, the engine is a high load state, by injecting air from the gas injection nozzle 8 Since there is no need to lower the inflow air speed by colliding air with the intake air to disturb the intake air, the controller 10 keeps the gas injection nozzle 8 inoperative (step 44).
Do not control the inflow air speed (Step 4
5). Therefore, the state where the inflow air velocity is high in the sub chamber 2 from the main chamber 1 side through the communication hole 9 is maintained, and the fuel is injected from the fuel injection nozzle 6, where the injected fuel is ignited and burns, and the fuel is rich and primary. Although the fuel is burned, the combustion is sufficiently performed in the sub chamber 2 because the communication hole 9 is narrowed.

Next, this sub-chamber type combustion chamber shifts to an expansion stroke, in the initial stage of the expansion stroke, the protruding portion 5 is intruding into the communication hole 9, and the combustion gas starts to be injected through the annular passage 13. Then, the protruding portion 5 comes out of the communication hole 9 and the passage area of the communication hole 9 increases at a stretch, and the combustion gas is blown out to the main chamber 1 at a stretch. Combustion of the combustion gas blown out to the main chamber 1 with fresh air existing in the main chamber 1 is promoted, so that the combustion period is shortened and secondary combustion is favorably performed. Therefore, unlike the conventional sub-chamber type engine, the sub-chamber type combustion chamber does not need to be formed in a shape that narrows the communication hole communicating the main chamber and the sub-chamber, and the communication hole 9 in the sub-chamber type combustion chamber is not required. Since the projecting portion 6 is made to protrude into the communication hole 9, the diameter of the communication hole 9 can be made large, and the mixing of the fuel or the air-fuel mixture with the air can be promoted. In this state, the fuel is completely burned, and the generation of HC and NO _X can be suppressed. Therefore, according to the pre-combustion chamber a combustion chamber, is performed combustion cycle in an optimum state to engine operating conditions, reduces the combustion period, the fuel economy is improved, HC, and occurrence of NO _X can be suppressed.

[0020]

The sub-chamber type combustion chamber according to the present invention is configured as described above and has the following effects. That is, the sub-chamber combustion chamber includes a gas injection nozzle disposed in the sub-chamber for injecting gas in a direction opposing air flowing into the sub-chamber through the communication hole, a load sensor for detecting an engine load, and the load sensor. A controller that controls the gas injection nozzle to inject gas toward the intake air in response to the partial load signal by the gas injection nozzle, so that the gas is injected from the gas injection nozzle against the intake air during the partial load, The air is disturbed to reduce the incoming air velocity, thereby reducing heat loss, gas flow loss, etc., and improving fuel economy. Further, when the engine is under a high load, the gas is not injected from the gas injection nozzle, so that the inflow air velocity is increased, and the combustion can be promoted.

Then, the sprayed fuel from the fuel injection nozzle arranged in the sub-chamber is injected into the strong air flow generated in the sub-chamber, that is, swirl, and a good air-fuel mixture is formed to ignite the primary fuel. Perform combustion. That is, at the top dead center of the piston, the flow area of the variable flow area passage is reduced to a narrowed state, and the air introduced into the sub chamber generates strong air turbulence in the sub chamber. In addition, since the fuel injection nozzle is composed of multiple injection holes, the fuel is sprayed radially with high injection, so that the sprayed fuel forms a good mixture with the swirl, and the fuel is rich in the sub-chamber. generation of the NO _X is suppressed by burning in a state.

Next, the combustion gas of the air-fuel mixture and the flame primarily burned in the sub-chamber flows into the main chamber at high speed from the sub-chamber along the conical surface of the protruding portion, and the swirl in the vertical direction in the main chamber. And flows. Therefore, the mixing of the combustion gas with the fresh air in the main chamber is promoted in the main chamber, and the mixing of the combustion gas and the air is achieved in a short period of time, so that the mixing is promoted.
The combustion period is shortened, good secondary combustion is performed, fuel efficiency is improved, and generation of hydrocarbon HC can be suppressed.

Further, since the sub-chamber type combustion chamber has a protruding portion extending from the piston head surface of the piston and entering the communication hole near the top dead center to reduce the flow area, the vicinity of the piston top dead center is reduced. With the reciprocating motion of the piston, the passage area of the communication hole formed between the inner peripheral surface of the communication hole and the side surface of the protrusion becomes variable. Therefore, unlike the conventional sub-chamber type combustion chamber, it is not necessary to configure the communication hole which communicates the main chamber and the sub-chamber with a shape that narrows the communication hole. Thus, the intake air into the sub-chamber flows smoothly without receiving a throttle loss, and a highly efficient engine can be provided without deteriorating the engine performance. Further, since the expansion stroke initial the communication hole is narrowed by the projecting portion, occurrence of HC, NO _X and the like by performing a primary combustion at a sufficiently fuel rich the vice chamber can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a sub-chamber type combustion chamber according to the present invention and showing a state when an engine is partially loaded.

FIG. 2 is a cross-sectional view showing a sub-chamber type combustion chamber shown in FIG. 1 and showing a state when an engine is under a high load.

FIG. 3 is a process flowchart showing one embodiment of the operation of the sub-chamber type combustion chamber shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main chamber 2 Sub chamber 4 Piston head 5 Projection part 6 Fuel injection nozzle 7 Cylinder head 8 Gas injection nozzle 9 Communication hole 10 Controller 11 Surge tank 12 Load sensor 13 Annular passage 15 Cylinder chamber 16 Multiple injection holes 17 Piston 20 Cavity

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02B 19/08 F02B 19/10 F02B 23/00 F02B 23/02

Claims (2)

(57) [Claims] 1. A sub-chamber formed in a cylinder head and having a fuel injection nozzle for spraying fuel disposed therein, a piston reciprocating in a cylinder constituting a main chamber, and a cylinder head communicating the sub-chamber to a cylinder side. In a sub-chamber combustion chamber having a formed communication hole, a gas injection nozzle disposed in the sub-chamber for injecting gas in a direction opposite to air flowing into the sub-chamber from the communication hole, a load sensor for detecting an engine load And a controller that controls a gas injection from the gas injection nozzle toward the intake air in response to a partial load signal from the load sensor. 2. The sub-chamber combustion according to claim 1, further comprising a protrusion extending from a piston head surface of the piston and protruding into the communication hole near a top dead center to reduce a passage area of the communication hole. Room.