JPH1054244A - Indirect injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve thermal efficiency by conducting ignition combustion in an auxiliary chamber formed at a piston and burning lean mixture formed previously at a main chamber in a short period in an indirect injection type engine. SOLUTION: This auxiliary chamber type engine is provided with an indirect injection chamber 2 formed at a piston 3, and a communication hole 6 and a central communication hole 5 which communicates the indirect injection chamber 2 and a main chamber 1 with each other. A fuel injection nozzle 4 injects fuel from a multiple-injection holes to the main chamber 1, produces uniform lean mixture at the main chamber 1 previously, and injects ignition fuel to the inside of the indirect injection chamber 2 through the central communication hole 5 near a piston compression top dead center to conduct ignition combustion at the indirect injection chamber 2. The fire flame injected to the main chamber 1 from the indirect injection chamber 2 triggers off short-period combustion of lean mixture in the main chamber 1, thus it is possible to reduce generation of NOX as the whole for improved thermal efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sub-chamber engine having a communication hole for communicating a main chamber formed on a cylinder side with a sub-chamber formed on a piston head or a cylinder head.

[0002]

2. Description of the Related Art Conventionally, a swirl chamber type engine having a swirl chamber has been developed for the purpose of improving the combustion of the engine. Such a swirl chamber type engine has a swirl chamber formed in a cylinder head, a communication hole communicating the swirl chamber with a main chamber formed on a cylinder side, and a fuel injection nozzle for spraying fuel into the swirl chamber. The vortex flowing into the swirl chamber through the hole forms a mixture of fuel and air injected into the swirl chamber and performs primary combustion.Then, a gas such as a flame, an unburned air-fuel mixture, etc. is transferred from the swirl chamber to the main chamber through the communication hole. Spouts and secondary combustion.

Japanese Utility Model Laid-Open Publication No. 58-77125 discloses a diesel engine with a combustion chamber inside the piston. The diesel engine with a combustion chamber inside the piston performs fuel injection from the fuel injection nozzle in the sub-chamber, and then, from the fuel injection nozzle to the main combustion chamber for the combustion gas injected from the sub-combustion chamber into the main combustion chamber. The remaining fuel is injected to form a strong vortex in the main combustion chamber.

Japanese Patent Application Laid-Open No. Hei 7-119577 discloses a fuel injection control device for a two-cycle diesel engine with a sub chamber. The fuel injection control device includes a main fuel injection nozzle for injecting fuel into the sub chamber in the latter half of the compression stroke to improve ignition delay, and a pre-fuel injection for injecting fuel into the sub chamber after the piston bottom dead center during scavenging. And a nozzle.

Japanese Patent Laid-Open Publication No. Hei 7-332091 discloses a sub-chamber engine. The sub-chamber engine forms a sub-chamber on the piston side, generates a fuel-rich mixture in the upper part of the sub-chamber, and quickly ejects the air-fuel mixture into the main chamber to shorten a combustion period. A nozzle is protruded from a nozzle hole formed at the top of the piston into the sub-chamber near the top dead center of the piston, and fuel is injected from the multiple injection holes toward a region higher than half the height in the axial direction with respect to the side wall surface. A communication hole is formed at the top of the piston around the nozzle hole, and the passage cross-sectional area of the communication hole is set to an area ratio of 1.5 to 5% with respect to the entire area of the piston top surface. The collision angle of the fuel spray from the multiple injection holes against the side wall surface on the top side of the piston is 90.
The angle is set to be in the range of ° to 120 °.

[0006] Japanese Patent Laid-Open Publication No. 3-115727 discloses a sub-chamber insulated engine. The sub-chamber insulated engine injects an amount of fuel equal to or less than a combustible air-fuel mixture into the main chamber toward the wall of the main chamber at an early stage of the suction stroke from the main nozzle to the main chamber to absorb heat energy from the wall, and the mixture by injecting fuel in the rich ignites combustion subchamber towards the wall surface of the auxiliary chamber near top dead center compression stroke from, NO _X,
It reduces the generation of HC, soot and the like.

Japanese Patent Application Laid-Open No. 4-259640 discloses a spark ignition internal combustion engine for lean burn. The lean-ignition spark ignition internal combustion engine arbitrarily controls the fuel supply ratio to the sub-chamber so that the nitrogen oxide concentration in the exhaust gas does not increase even when the operating state changes.

[0008]

To the 0005] Generally, the combustion temperature in the secondary chamber because of the high temperature, as a measure to reduce the production of NO _X, it is effective to combust the fuel-rich.
In addition, when the combustion temperature is high, it is effective to use a sub-chamber engine as a type of engine structure in order to perform fuel-rich combustion. In order to increase the combustion speed of the sub-chamber combustion chamber to the same level as the combustion speed of the direct injection combustion chamber when the engine is configured as a sub-chamber combustion chamber, a communication hole communicating the sub-chamber with the main chamber is provided. It is necessary to enlarge the cross-sectional area of the passage. However, if the passage cross-sectional area of the communication hole is increased, the speed of jetting out from the sub-chamber to the main chamber is reduced, and combustion in the main chamber is not sufficiently performed.

Further, in the conventional engine, in order to achieve both high thermal efficiency and low NO _X , the lean premixed gas is compressed,
Development is underway to burn by self-ignition near top dead center. In this case, a very high thermal efficiency can be expected by combining a high compression ratio and lean premixing, but the combustion temperature is low due to the leaner, and NO The generation of _X is also very small. However, in such a premixed lean self-ignition engine, it is very important to control the ignition point, and it is extremely difficult to compress so that knocking does not occur and to satisfactorily self-ignite near the piston compression top dead center. . That is, in the engine, there is a variation in each cycle, and there is a variation in each cylinder, so that stable self-ignition cannot be performed. Therefore, in the premixed lean self-ignition engine,
There is a problem how to control the ignition point. Also, to make such an engine practical,
To avoid knocking, generate a lean enough mixture, set a lower compression ratio,
It is important to use a highly knockable (high octane) fuel such as gasoline. In an engine having such a combustion process, basically, if the mixture is sufficiently lean, the engine can be operated so that self-ignition does not occur even with light oil.

The sub-chamber insulated engine disclosed in Japanese Patent Laid-Open No. 3-115727 requires a main nozzle for injecting fuel into the main chamber and a sub-nozzle for injecting fuel into the sub-chamber. As the auxiliary chamber is of the swirl chamber type, the mixing time in the main chamber becomes longer, and it is difficult to increase the combustion speed.

In the spark ignition internal combustion engine disclosed in Japanese Patent Laid-Open No. 4-259640, the distribution of fuel gas to the main chamber and the sub chamber is controlled based on the result of a nitrogen oxide concentration sensor. In the case of spark ignition,
Since the heat energy is small, it is necessary to perform combustion by flame propagation, and there is a limit to making the equivalent of the air-fuel mixture in the main chamber lean.

The homogeneous charge compression ignition engine has high efficiency and N
In order to suppress the generation of O _X, it is necessary to properly carry out the control of the ignition timing, the temperature in the cylinder, the equivalent ratio of the pressure or the premixed gas, or ignition timing is changed, the non-ignition . In addition, the homogeneous charge compression ignition engine partially ignites depending on the state of the air-fuel mixture in the cylinder, but does not burn over the entire area and misfires, and can be operated only in an extremely narrow operating range. Further, in the premixed compression ignition engine, since the premixed air is not self-ignited at a high compression ratio, a lean mixture and a high octane fuel are used. For example, using gasoline as fuel, and setting the compression ratio to 15-16
In this case, the equivalent ratio that does not cause self-ignition is 0.5 or less. Even if sparks are ignited in such a state, the flame does not propagate and propagate, causing misfire. In addition, as a countermeasure, self-ignition is extremely difficult because it requires time to form an air-fuel mixture even if gasoline is injected near top dead center, and it takes time because the air-fuel mixture rises in temperature. It is.

Therefore, in the sub-chamber engine, the temperature in the sub-chamber is raised in order to create a condition in which the injected fuel is liable to self-ignite, and an air-fuel mixture having an equivalence ratio close to 1 is generated in a short time. In addition, in the sub-chamber engine, ignition and combustion at a high compression ratio with a super-lean mixture can be performed to increase the theoretical thermal efficiency, so how to perform ignition and combustion at a high compression ratio with a super-lean mixture, After ignition in the sub chamber, how to burn the lean mixture in the main chamber in a short time,
Fuel injected for ignition into the sub-chamber does not flow out to the main chamber,
That is, the mixture is generated in the sub-chamber and the heat is taken from the high-temperature wall surface to instantaneously ignite the combustible mixture.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems. In a premixed compression ignition engine, the ignition timing is appropriately controlled so that the premixed air can be steadily reduced in a short time. In addition, the combustion is performed in a wide operating range, and the premixed lean combustion in the main chamber is performed. The premixed air in the main chamber is secured at a high compression ratio, and the mixture is lean enough to prevent self-ignition, that is, knocking. A fuel-air mixture is generated in advance, then fuel for ignition is injected into the sub-chamber, and a flame and an unburned air-fuel mixture are radially ejected from the sub-chamber to the periphery of the cylinder through a number of communication holes, and the flame is ignited. is flame propagation in lean mixture in the main chamber in the, and up combustion speed in the main chamber to complete the combustion in the short, providing a pre-combustion chamber engine to reduce the occurrence of overall NO _X, thereby improving the thermal efficiency It is to be.

According to the present invention, there is provided a piston reciprocating in a cylinder, a main chamber formed on the cylinder side surrounded by a top surface of the piston and the cylinder, and provided substantially at the center of the cylinder. A sub-chamber, a plurality of communication holes formed in the cylinder central region that communicate the main chamber and the sub-chamber substantially in the circumferential direction, and a fuel injection nozzle configured to inject fuel into at least the sub-chamber. Then, during a predetermined period from the suction stroke to the compression stroke, a lean mixture that does not self-ignite in the main chamber is generated, and the fuel for injection into the sub-chamber from the fuel injection nozzle near the piston compression top dead center. And a sub-chamber engine that ignites the air-fuel mixture in the sub-chamber.

Further, the sub-chamber is formed by a sub-chamber member disposed in a cavity formed substantially in the center region of the cylinder of the cylinder head, and the communication hole is formed in the sub-chamber member so as to be circumferentially spaced. The lean mixture generated in the main chamber is generated by injecting fuel from the fuel injection nozzle through the communication hole into the main chamber.

Alternatively, in this sub-chamber engine, another fuel injection nozzle is provided in an intake system for supplying intake air to the main chamber, and the lean mixture generated in the main chamber is supplied to the another fuel injection nozzle. And is generated by injecting fuel into the intake system.

Further, the sub-chamber is formed by a sub-chamber member disposed in a cavity formed substantially in the center region of the cylinder of the cylinder head, and the sub-chamber member is interposed between the cavity of the cylinder head through a heat shield layer. It is arranged.

The sub-chamber is formed by a sub-chamber member disposed in a cavity formed substantially in the center region of the cylinder of the cylinder head, and a wall for controlling the temperature of the sub-chamber is provided in a wall of the sub-chamber member. Therefore, a heater is provided.

Alternatively, the present invention provides a piston which reciprocates in a cylinder, a main chamber formed on the cylinder side, a sub-chamber formed in the piston so as to be located substantially at the center of the cylinder, A central communication hole formed substantially in the cylinder central region communicating the main chamber and the sub-chamber, and a plurality of communication holes formed in a circumferential direction around the central communication hole; A fuel injection nozzle having a multi-injection hole for injecting fuel into the sub-chamber, and generating a lean air-fuel mixture that does not self-ignite by injecting fuel into the main chamber during a predetermined period from a suction stroke to a compression stroke. And a controller for injecting ignition fuel into the sub-chamber near the piston compression top dead center and performing control to ignite and burn a mixture in the sub-chamber.

In this sub-chamber engine, fuel is injected from the multiple injection holes of the fuel injection nozzle into the sub-chamber through the central communication hole formed in the piston toward the wall surface of the sub-chamber. It is what is injected.

In this sub-chamber engine, the fuel injection nozzle protrudes into the central communication hole near the piston compression top dead center, and the fuel is injected from the multi-injection hole toward the wall surface of the sub-chamber in the sub-chamber. Is injected.

In this sub-chamber type engine, the sub-chamber is constituted by a sub-chamber structure made of a heat-resistant material and disposed in a cavity formed in the piston via a heat-insulating layer. .

Since the sub-chamber engine is constructed as described above, in the intake stroke or the compression stroke, a part of the fuel is injected from the fuel injection nozzle into the main chamber so that the main chamber does not self-ignite. A lean air-fuel mixture is generated in advance, and then fuel for ignition is injected into the sub-chamber near the piston compression top dead center, mixed with high-temperature air in the sub-chamber, and ignited and burned. In addition, since the sub-chamber has a heat shielding structure, the wall temperature in the sub-chamber is higher than the wall temperature in the main chamber. It can be ignited and burned, the temperature and pressure in the sub-chamber rises sharply and the combustion energy increases, causing a flame to radiate radially from the sub-chamber to the main chamber through a number of communication holes circumferentially separated, Since the flame that has erupted into the main chamber radiates radially with a strong penetration, the flame becomes a kind of fire, entrains the lean air-fuel mixture in the main chamber, propagates through the combustion, and immediately reaches the cylinder periphery, completing the combustion in a very short time. To improve thermal efficiency.

In addition, in this sub-chamber engine, the combustion ratio in the sub-chamber is reduced as a whole, and the main chamber is mainly used for combustion. Further, since the sub-chamber combustion is partially diesel combustion, NO _X is generated. However, since the air-fuel mixture in the sub-chamber is lean overall, the amount of generated NO _X is small. Further, even if the air-fuel mixture in the sub-chamber is made rich, the generation of NO _X becomes a small value. Since the lean mixture burns in the main room,
The generation of NO _X can be reduced to almost zero, and the NO _X emission can be greatly reduced as a whole in the combustion of the sub chamber and the main chamber. For example, the NO _X emission can be reduced to 0 to 50 ppm.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sub-chamber engine according to the present invention will be described below with reference to the drawings. 1 shows a first embodiment of a sub-chamber engine according to the present invention, and is a cross-sectional view showing a state in the middle of a compression stroke. FIG. 2 is a cross-sectional view showing a state of a piston compression top dead center of the sub-chamber engine of FIG. FIG. 3 is a sectional view showing an initial stage of an expansion stroke of the sub-chamber engine of FIG. 1, and FIG. 4 is an explanatory diagram showing injection timing of a fuel injection nozzle in the sub-chamber engine of FIG.

The sub-chamber engine of the first embodiment is, for example,
A cylinder liner 18 constituting a cylinder 20 disposed in a hole 19 formed in a cylinder block 17, a cylinder head 13 fixed to the cylinder block 17 via a gasket 25, and a fuel injection nozzle attached to the cylinder head 13 4 and a piston 3 reciprocating in the cylinder 20. The piston 3 has a piston ring groove 27 in which the piston ring 26 is mounted. In this sub-chamber engine, the main chamber 1 is located on the cylinder 20 side and the cylinder head lower surface 14 and the piston top surface 1
The sub-chamber 2 is formed in a cavity 9 formed in the piston 3. The cylinder block 17 has holes 19 corresponding to the number of cylinders of the engine.
Are formed. The cylinder 20 may be formed by the cylinder liner 18 fitted into the hole 19 as described above, or may be directly formed by the hole 19 of the cylinder block 17. Also, the cylinder head 13
, An intake port 22 and an exhaust port 24 are formed, the intake port 22 is provided with an intake valve 21, and the exhaust port 24 is provided with an exhaust valve 23.

Although not shown, the piston 3 includes a piston body made of a metal such as aluminum alloy and FC,
It can be constituted by a sub-chamber structure forming a sub-chamber made of heat-resistant high-strength ceramics such as Si ₃ N ₄ arranged in a cavity formed in the piston body. The heat shielding structure of the sub-chamber 2 can be configured, for example, by arranging a ceramic sub-chamber structure in the cavity of the piston 3 and forming a heat-insulating air layer between the cavity and the outer surface of the sub-chamber structure. If the sub-chamber 2 is configured as a heat shield structure, the wall temperature of the sub-chamber 2 can be maintained higher than the wall temperature of the main chamber 1, and the fuel injected into the sub-chamber 2 can be ignited and burnt well.

In this sub-chamber type engine, the cavity 9 is formed in the center of the cylinder of the piston 3 reciprocating in the cylinder 20, and the sub-chamber 2 is formed substantially in the center of the cylinder 20 by covering the cavity 9 with the piston top 15. Have been. A central communication hole 5 is formed in the piston top 15 so that fuel from the fuel injection nozzle 4 is injected into the sub-chamber 2 at the center of the cylinder. Also, the fuel injection nozzle 4
Has multiple injection holes 8 spaced apart in the circumferential direction. The controller can control the injection timing of the fuel injection nozzle 4, and injects fuel from the multiple injection holes 8 of the fuel injection nozzle 4 into the main chamber 1 during a predetermined period from the suction stroke to the compression stroke. A lean mixture that does not ignite is generated in advance, and then control is performed to inject fuel into the sub chamber 2 through the central communication hole 5 near the piston compression top dead center.

In this sub-chamber engine, the piston 3
A central communication hole 5 and a communication hole 6 are formed in the piston top 15 to communicate the main chamber 1 and the sub-chamber 2. The center communication hole 5 is formed substantially in the center region of the cylinder on the piston top 15. The central communication hole 5 may be formed as a circular hole as shown in the figure, or may be formed as a petal-shaped hole with a rugged periphery, though not shown. In addition, a plurality of communication holes 6 are formed in the circumferential direction around the central communication hole 5 formed in the piston top 15.
The communication hole 6 has a main chamber side opening 10 opening to the main chamber 1 and the sub chamber 2
It is formed so as to communicate with the sub-chamber-side opening 11 that opens to the outside.

In this sub-chamber engine, as shown in FIGS. 1 and 4, fuel is injected from the multiple injection holes 8 of the fuel injection nozzle 4 into the main chamber 1 during a predetermined period from the suction stroke to the compression stroke. To generate a lean mixture, i.e., a premix, in the main chamber 1 to such an extent that self-ignition does not occur. Next, as shown in FIGS. 2 and 4, near the piston compression top dead center (explosion top dead center), the fuel for ignition is introduced into the sub chamber 2 from the multiple injection holes 8 of the fuel injection nozzle 4 through the central communication hole 5. Is injected and mixed with the lean air-fuel mixture in the sub-chamber 2 to ignite and burn. In this case, it is sufficient if the fuel injected from the multiple injection holes 8 of the fuel injection nozzle 4 is injected into the sub-chamber 2, so that the tip of the fuel injection nozzle 4 is connected to the center as shown in FIG. There is no need to protrude into the hole 5, and it is only necessary to protrude slightly from the lower surface 14 of the cylinder head 13, and the durability of the fuel injection nozzle 4 is not impaired.

In the sub-chamber engine, as described above, when the fuel for ignition is injected into the sub-chamber 2 from the multiple injection holes 8 of the fuel injection nozzle 4, the sub-chamber 2 is configured to have a heat shielding structure. When the fuel collides with the high-temperature wall surface in the sub-chamber 2 or the fuel is injected toward the wall surface, the fuel is injected into the sub-chamber 2 because the temperature in the sub-chamber 2 is high. As a result, a relatively rich air-fuel mixture is generated and self-ignites, ignition and combustion occur immediately and reliably in the sub-chamber 2, and the temperature and pressure in the sub-chamber 2 rapidly rise to increase the combustion energy. As shown in FIG. 3, the flame is radiated radially from the sub-chamber 2 to the main chamber 1 through a large number of communication holes 6 circumferentially separated, and the flame blasted into the main chamber 1 is radiated by strong penetration. Spouts. Therefore, immediately reaches the periphery cylinder jetted flame with burn propagation involving a lean mixture in the main chamber 1 becomes spark, to complete the combustion in an extremely short time, the emission of the overall NO _X The heat efficiency can be improved by greatly reducing the temperature.

Next, a second embodiment of the sub-chamber engine according to the present invention will be described with reference to FIG. FIG. 5 is a sectional view showing a second embodiment of the sub-chamber engine according to the present invention, showing a state near a piston compression top dead center. The second embodiment has the same configuration and operation and effects as those of the first embodiment except that a plurality of central communication holes formed at the top of the piston are formed. , And duplicate description is omitted here.

As shown in FIG. 5, in this sub-chamber engine, a plurality of central communication holes 7 are formed at intervals in the circumferential direction around the center of the piston. Moreover, the multiple injection holes 8 provided in the fuel injection nozzle 4 correspond to the respective central communication holes 7, and the fuel spray injected from the multiple injection holes 8 respectively passes through the respective central communication holes 7 into the sub-chamber 2. And is ignited and mixed with the air in the high-temperature sub-chamber 2.
The central communication hole 7 is formed as a hole having a diameter small enough to allow the fuel spray injected from the multiple injection holes 8 of the fuel injection nozzle 4 to pass therethrough, and is set so that the injected fuel collides with the wall surface of the sub-chamber 2. Have been.

A third embodiment of the sub-chamber engine according to the present invention will be described with reference to FIG. FIG. 6 is a sectional view showing a piston in a third embodiment of the sub-chamber engine according to the present invention. The third embodiment is different from the first embodiment in that the sub-chamber 2 formed in the piston has a heat shielding structure, and the fuel injection nozzle is inserted into the central communication hole near the top dead center. Have the same configuration and the same operation and effect, and a duplicate description will be omitted here.

As shown in FIG. 6, in this sub-chamber engine, the piston 30 has a piston body 31 made of a metal such as an aluminum alloy or FC, and a heat-resistant body disposed in a cavity 32 formed in the piston body 31. Si ₃ N
A sub-chamber structure 33 which forms the sub-chamber 2 made of ceramics such as ₄ is provided. The heat shielding structure of sub chamber 2
The sub-chamber structure 33 is disposed in the cavity 32 of the piston 30, and a heat shield air layer 34 is formed between the cavity 32 and the outer surface of the sub-chamber structure 33. The piston top 35 has a central communication hole 36 sized so that the fuel injection nozzle 4 attached to the cylinder head 13 can enter.
And a plurality of communication holes 37 circumferentially spaced around the central communication hole 36. Further, in this sub-chamber engine, the fuel injection nozzle 4 attached to the cylinder head 13 protrudes into the central communication hole 36 formed in the piston top 35 near the piston compression top dead center, and enters the sub-chamber 2. The fuel for ignition can be injected from the multiple injection holes 8 so as to collide with the wall surface of the sub chamber 2. In this embodiment, the sub-chamber structure 33 is made of a vertically divided member, but it is needless to say that the sub-chamber structure 33 can be constructed in various structures.

Next, a fourth embodiment of the sub-chamber engine according to the present invention will be described with reference to FIGS.
7 is a sectional view showing a fourth embodiment of the sub-chamber engine according to the present invention, FIG. 8 is a cross-sectional view of the sub-chamber member along line AA in FIG. 7, and FIG. 9 shows a state in which fuel is injected into the main chamber. Illustrated illustration,
FIG. 10 is an explanatory view showing a state in which a lean mixture is generated in the main chamber, FIG. 11 is an explanatory view showing a state in which the lean mixture enters the sub chamber from the main chamber, and FIG. FIG. 13 is an explanatory diagram showing a state in which the air-fuel mixture is ejected, and FIG. 13 is a diagram showing fuel injection and ignition timing. Compared with the engine of the first embodiment, the sub-chamber type engine of the fourth embodiment has substantially the same configuration except that the structure in which the sub-chamber 42 is provided in the cylinder head 13 is different. Are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIGS. 7 and 8, this sub-chamber type engine has a piston 43 which reciprocates in the cylinder 20;
A main chamber 41 formed on the cylinder 20 side, a sub-chamber 42 provided in the cylinder head 13 so as to be located substantially at the center of the cylinder 20, and a circumferential direction substantially in a cylinder central region communicating the main chamber 41 and the sub-chamber 42. A plurality of communication holes 46 formed at a distance from each other and a fuel injection nozzle 44 for injecting fuel into at least the sub-chamber 42. The main chamber 41 is automatically connected to the main chamber 41 during a predetermined period from the suction stroke to the compression stroke. A lean mixture that does not ignite is generated, fuel is injected from the fuel injection nozzle 44 into the sub-chamber 42 near the piston compression top dead center, and the sub-chamber 42 ignites and burns. A cavity 49 is formed in the piston crown of the piston 43 and forms a part of the main chamber 41. Sub-chamber member 45 constituting sub-chamber 42
The heat shield gaskets 51, 5 are provided with the flange 57 on the step 58 of the cavity 50 formed in the cylinder head 13.
2 are interposed. The fuel injection nozzle 44
The multi-injection hole 48 is opened through the through hole 54 of the sub chamber member 45 into the sub chamber 42.

The sub-chamber 42 is formed in a sub-chamber member 45 disposed in a cavity 50 formed substantially in the center area of the cylinder head 13, and the communication hole 46 is formed in the sub-chamber member 45.
Is formed. As shown in FIGS. 9 and 10, the lean air-fuel mixture generated in the main chamber 41 is
From the main chamber 41 through the communication hole 46. The sub-chamber 42 is formed in a sub-chamber member 45 disposed in a cavity 50 formed substantially in the center region of the cylinder of the cylinder head 13. The sub-chamber member 45 is provided with the heat shielding gasket 5 in the cavity 50 of the cylinder head 13.
It is arranged via a heat shield layer composed of the air layers 1 and 52 and the air layer 53. The heat shielding gaskets 51 and 52 are made of a material such as ceramics having a low thermal conductivity. Therefore,
The sub-chamber 42 formed in the sub-chamber member 45 has a heat shielding structure. The sub chamber member 45 is provided with a heater 47 for controlling the temperature in the sub chamber 42. Heater 47
Is supplied with electric power through a lead wire 56 and is controlled by a controller. Fuel injection nozzle 44
Is formed with a plurality of injection holes 48. The injection hole 48
They are formed to face the communication holes 46 of the sub chamber member 45, respectively.

In this sub-chamber engine, FIGS.
As shown in FIG. 5, during the period from just before the end of the exhaust stroke to the first half of the compression stroke through the suction stroke, the fuel injection nozzle 4
Fuel is injected from the four injection holes 48, and the fuel is injected from the sub-chamber 42 through the communication hole 46 into the main chamber 41. Since the injection hole 48 of the fuel injection nozzle 44 faces the communication hole 46, the fuel from the injection hole 48 passes through the communication hole 46 and passes through the main chamber 4.
1 is reliably injected. During this period, the fuel injection nozzle 44
The flow rate of fuel injected from the fuel cell is adjusted to such an extent that a lean air-fuel mixture is generated that does not ignite, that is, does not spontaneously ignite (knock). Next, as shown in FIG. 10, the fuel is diffused in the main chamber 41, and a lean mixture is generated in the main chamber 41.

As shown in FIG. 11, in the compression stroke,
The lean mixture in the main chamber 41 is connected to the sub-chamber 4 through the communication hole 46.
2 to a high temperature state in the sub-chamber 42. The sub-chamber 42 is configured as a heat shield structure, and the air-fuel mixture flowing from the main chamber 41 to the sub-chamber 42 through the communication hole 46 is narrowed to the communication hole 46 and flows in at a high speed. Higher than the inside temperature. As shown in FIGS. 12 and 13,
At the end of the compression stroke, fuel is injected again from the fuel injection nozzle 44 into the sub-chamber 42, and at this time, the piston 43 is in a rising stroke, and the air-fuel mixture flows from the main chamber 41 to the sub-chamber 42. Therefore, the fuel injected into the sub chamber 42 does not flow out to the main chamber 41. When the fuel for ignition is injected into the sub-chamber 42, the spray receives heat from the high-temperature wall of the sub-chamber member 45, and a temperature, a pressure and an equivalence ratio sufficient to ignite can be secured. The mixture is ignited and burned. Further, at the time of starting or at the time of partial load, the temperature of the sub-chamber member 45 is low, and the temperature in the sub-chamber 42 is low.
There is a possibility that self-ignition in the sub chamber 42 is unlikely to occur. Therefore,
In order to assist the ignition and combustion of the fuel in the sub-chamber 42, the heater 47 is energized by a command from the controller to raise the temperature of the sub-chamber member 45 to increase the temperature inside the sub-chamber 42.

By igniting and burning the combustible mixture,
The pressure in the sub-chamber 42 rises, and a flame and an air-fuel mixture are jetted from the sub-chamber 2 to the main chamber 41 through the communication hole 46, so that the temperature and the pressure in the main chamber 41 increase, and the lean air-fuel mixture in the main chamber 41 Self-ignites, the speed of flame propagation to the lean mixture in the main chamber 1 increases, and the fuel speed in the main chamber 41 increases,
Combustion is completed in a short time. That is, the flame spouted from the sub-chamber 42 to the main chamber 41 becomes a fire, causing high-speed combustion in the main chamber 41, and the combustion is completed in a short time. Since the burning of the majority of the fuel is burned in a lean air-fuel mixture in the main chamber 41, it is possible to greatly suppress the generation of NO _X.

In the sub-chamber engine, the main chamber 41
Produces a lean mixture, but at partial load,
Since the degree of lean may be too high, a throttle can be provided to control the amount of intake air as needed, but the throttle ratio of intake air is significantly smaller than that of a conventional gasoline engine. The fuel used for this sub-chamber engine can be gasoline, methanol, etc., with high octane number, light oil with low cetane number, etc., but other fuels can be used by selecting the compression ratio etc. Can also.

Next, a fifth embodiment of the sub-chamber engine according to the present invention will be described with reference to FIGS. FIG. 14 is a sectional view showing a fifth embodiment of the sub-chamber engine according to the present invention, FIG. 15 is a graph showing changes in the pressure in the main chamber and the sub-chamber and the temperature in the cylinder corresponding to the piston displacement, and FIG. FIG. 3 is a diagram showing fuel injection and ignition timing.
The sub-chamber engine according to the fifth embodiment is different from that according to the fourth embodiment mainly in that fuel is injected into the intake pipe and the main chamber 41 is used.
Since they have almost the same configuration except that a lean air-fuel mixture is generated, the same components are denoted by the same reference numerals, and redundant description will be omitted.

This sub-chamber type engine has a cylinder head 1
A sub-chamber member 45 forming a sub-chamber 42 is provided at the center of the fuel injection nozzle 3, a plurality of communication holes 46 are formed radially in the sub-chamber member 45, and a fuel injector
5 is provided. That is, a fuel injection nozzle 55 is provided in an intake system (intake port 22) that supplies intake air to the main chamber 41, and lean air-fuel mixture generated in the main chamber 41 injects fuel from the fuel injection nozzle 55 to the intake port 22. Generated by This sub-chamber engine injects fuel from the fuel injection nozzle 55 to the intake port 22 to generate a lean mixture, and the lean mixture is used in the main chamber 4 during the intake stroke.
1 and the fuel for ignition from the fuel injection nozzle 44 provided in the sub chamber 42 near the top dead center of the compression stroke.
2 and is ignited and burned in the sub-chamber 42.

In the sub-chamber engine, the lean air-fuel mixture at the intake port 22 of the intake system is sucked into the main chamber 41, and self-ignition (knocking) does not occur in the main chamber 41 because the air-fuel mixture is lean. The sub-chamber member 45 includes heat shielding gaskets 51 and 52.
The sub-chamber 42 has a heat-shielding structure, and is maintained at a high temperature because the sub-chamber 42 is arranged on the cylinder head 13 via a heat-shielding layer including the heat-shielding air layer 53. Further, the lean air-fuel mixture flowing from the main chamber 41 into the sub-chamber 42 is narrowed by the communication hole 46 and flows in at a high speed, so that the lean air-fuel mixture flowing into the sub-chamber 42 has a high thermal conductivity. It is hotter than the lean mixture inside. When the fuel for ignition is injected from the fuel injection nozzle 44 into the sub chamber 42, the spray receives heat from the high temperature wall, and the temperature, pressure, and equivalent ratio necessary for self-ignition are secured, and the air-fuel mixture is generated in the sub chamber 42. It will self-ignite. Next, the main chamber 41 is connected from the sub chamber 42 through the communication hole 46.
As a result, the temperature and pressure in the main chamber 41 rise, and self-ignition becomes easy, or the flame becomes a kind of fire and propagates, and the combustion speed increases. Complete.

In the sub-chamber engine of the fifth embodiment, as described above, the main combustion, that is, the combustion in the main chamber 41, is extremely lean, so that the generation of NO _X is largely suppressed. Further, in the fifth embodiment, similarly to the fourth embodiment, at the time of partial load or starting, the heater 47 provided in the sub-chamber member 45 is energized to increase the temperature of the sub-chamber 42.

[0048]

[Effect of the Invention] pre-combustion chamber engine according to the present invention, which is configured as described above, for most of the combustion of the main chamber is premixed lean combustion, the combustion temperature is low, very generation of the NO _X Can be reduced. Since the flame from the sub-chamber radiates radially to the main chamber through a large number of communication holes, the ignition source in the main chamber becomes a flame blown out from the communication holes, and combustion is completed in a very short time in the entire main chamber. Combustion with a high compression ratio and a lean mixture can ensure high thermal efficiency. In addition, the amount of unburned mixture and flame ejected from the sub chamber to the main chamber through the communication hole is small because most of the fuel is injected into the main chamber in advance, and as a result,
The size of the sub-chamber itself can be made small, and the sub-chamber of the heat shielding structure can be formed favorably on the piston.

Further, in this sub-chamber engine, most of the heat is generated in the pre-mixed air injected into the main chamber in advance, and the amount of fuel injected into the sub-chamber is sufficient to create an ignition source in the sub-chamber. .
Therefore, since the generation of the air-fuel mixture in the sub-chamber has a relatively small effect on the engine performance, the fuel injection nozzle does not always need to be inserted into the sub-chamber, and the durability of the fuel injection nozzle can be greatly improved. it can.

In this sub-chamber engine, the lean air-fuel mixture can be burned at a high compression ratio in the main chamber, so that the thermal efficiency can be improved and most of the fuel is supplied to the lean air-fuel mixture in the main chamber. Is burned at
O _X generated can be significantly reduced, the ignition control is facilitated, a simple structure itself may be constructed by modifying an existing engine.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a sub-chamber engine according to the present invention and showing a state during fuel injection during a compression stroke.

FIG. 2 is a sectional view showing a state at the time of fuel injection near a piston compression top dead center of the sub-chamber engine of FIG.

FIG. 3 is a cross-sectional view showing an initial state of an expansion stroke of the sub-chamber engine of FIG.

FIG. 4 is an explanatory diagram showing injection timing of a fuel injection nozzle in the sub-chamber engine of FIG.

FIG. 5 is a cross-sectional view showing another embodiment of the sub-chamber engine according to the present invention, showing a state at the time of fuel injection near the piston compression top dead center.

FIG. 6 is a sectional view showing a piston in still another embodiment of the sub-chamber engine according to the present invention.

FIG. 7 is a sectional view showing a fourth embodiment of the sub-chamber engine according to the present invention.

8 is a cross-sectional view of the sub-chamber member taken along line AA in FIG.

FIG. 9 is an explanatory diagram showing a state in which fuel is injected into a main chamber.

FIG. 10 is an explanatory diagram showing a state in which a lean mixture is generated in a main chamber.

FIG. 11 is an explanatory diagram showing a state in which a lean air-fuel mixture enters the sub-chamber from the main chamber.

FIG. 12 is an explanatory view showing a state in which a flame and an air-fuel mixture blow out from a sub chamber to a main chamber.

FIG. 13 is a diagram showing fuel injection and ignition timing.

FIG. 14 is a sectional view showing a fifth embodiment of the sub-chamber engine according to the present invention.

FIG. 15 is a graph showing changes in the pressure in the main chamber and the sub-chamber and the temperature in the cylinder corresponding to the piston displacement.

FIG. 16 is a diagram showing fuel injection and ignition timing.

[Explanation of symbols]

 1,41 Main chamber 2,42 Sub chamber 3,30,43 Piston 4,44,55 Fuel injection nozzle 5,7,36 Central communication hole 6,37,46 Communication hole 8,48 Multi injection hole 9,32,50 Cavity 13 Cylinder head 20 Cylinder 22 Intake port (intake system) 33 Sub chamber structure 34 Heat shield layer 45 Sub chamber member 47 Heater 51, 52 Heat shield gasket 53 Heat shield air layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F02M 61/18 320 F02M 61/18 320Z

Claims (9)

[Claims] 1. A piston reciprocating in a cylinder, a main chamber formed on the cylinder side surrounded by a top surface of the piston and the cylinder, and a sub-chamber provided to be located substantially at the center of the cylinder. A plurality of communication holes formed in the cylinder central region that communicate with the main chamber and the sub-chamber in the circumferential direction and formed at intervals in the circumferential direction, and at least a fuel injection nozzle that injects fuel into the sub-chamber, Generates a lean mixture that does not self-ignite the main chamber during a predetermined period between the suction stroke and the compression stroke, and injects ignition fuel from the fuel injection nozzle into the sub-chamber near the piston compression top dead center. And a sub-chamber engine for igniting and burning the air-fuel mixture in the sub-chamber. 2. The sub-chamber is formed by a sub-chamber member disposed in a cavity formed substantially in the cylinder center region of the cylinder head, and the communication hole is formed in the sub-chamber member so as to be circumferentially spaced from the sub-chamber member. 2. The sub-chamber engine according to claim 1, wherein the lean air-fuel mixture generated in the main chamber is generated by injecting fuel from the fuel injection nozzle into the main chamber through the communication hole. 3. 3. An intake system for supplying intake air to the main chamber is provided with another fuel injection nozzle, and a lean air-fuel mixture generated in the main chamber supplies fuel from the another fuel injection nozzle to the intake system. The sub-chamber engine according to claim 1, wherein the engine is generated by injection. 4. The sub-chamber is formed by a sub-chamber member disposed in a cavity formed substantially in the center region of the cylinder of the cylinder head, and the sub-chamber member is formed on the cavity of the cylinder head through a heat shield layer. The sub-chamber engine according to any one of claims 1 to 3, wherein the sub-chamber engine is arranged at an angle. 5. The sub-chamber is formed by a sub-chamber member disposed in a cavity formed substantially in the cylinder center region of the cylinder head, and a wall of the sub-chamber member is provided for controlling the temperature of the sub-chamber. A heater is arranged for this purpose.
5. The sub-chamber engine according to any one of 4. 6. A piston reciprocating in a cylinder, a main chamber formed on the cylinder side, a sub-chamber formed in the piston so as to be located substantially at the center of the cylinder, and the main chamber and the main chamber formed in the piston. A plurality of communication holes formed in a circumferential direction around the center communication hole and the center communication hole formed substantially in the cylinder center region communicating with the sub chamber;
A fuel injection nozzle having a multi-injection hole for injecting fuel into the main chamber and the sub-chamber, and a fuel injection nozzle that injects fuel into the main chamber and does not self-ignite during a predetermined period from a suction stroke to a compression stroke. A sub-chamber engine comprising: a controller that generates a lean air-fuel mixture, controls ignition of the air-fuel mixture in the sub-chamber by injecting ignition fuel into the sub-chamber near a piston compression top dead center, and performs combustion. 7. The fuel injection nozzle according to claim 6, wherein fuel is injected from the multiple injection holes of the fuel injection nozzle into the sub-chamber through the central communication hole formed in the piston toward a wall surface of the sub-chamber. The described subchamber engine. 8. The fuel injection nozzle protrudes into the central communication hole near a piston compression top dead center, and fuel is injected from the multiple injection holes toward the wall surface of the sub-chamber in the sub-chamber. A sub-chamber engine according to the above. 9. The heat shield structure according to claim 6, wherein said sub-chamber is a sub-chamber structure made of a heat-resistant material disposed in a cavity formed in said piston via a heat shield layer. The sub-chamber engine according to claim 1.