JPH059616B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a combustion chamber of a direct injection diesel engine, and in particular, it produces slow combustion without ignition delay over a wide range of conditions, from low loads to high loads, thereby producing blue and white smoke. This invention relates to a direct injection diesel engine combustion chamber that can significantly reduce combusted unburned materials and noise.

[Prior Art] In general, direct injection diesel internal combustion engines have advantages such as high combustion efficiency and low exhaust temperature.
On the other hand, high explosion pressure, vibration, noise, etc. were considered to be disadvantageous.

In order to improve these drawbacks, the top of the piston is recessed to form a combustion chamber, and while a swirl is generated within the combustion chamber, fuel is injected and collides with the inner wall of the combustion chamber to evaporate it, thereby reducing the swirl. A so-called MAN-M type engine is known in which a premixture with excellent ignitability is generated by mixing the premixed mixture with the premixed mixture, and the premixed mixture is spontaneously ignited and combusted.

However, since the M type engine is a type in which the injected fuel is evaporated and burned, it does not have sufficient wall evaporation capacity under conditions where the atmospheric temperature is low and the engine cooling water temperature is low. As a result, a large amount of unburned matter (HC) is generated in the combustion chamber, which causes blue-white smoke. Furthermore, even when the air and water temperatures are normal, when the load is light such as when idling, the wall temperature required for fuel evaporation has not been reached, so a large amount of unburned matter (HC) is generated and the combustion state is deteriorated. It became a factor that made things worse.

It has also been confirmed that this drawback occurs even in lean conditions with controlled fuel injection in a toroidal combustion chamber. The reason is that after ignition, the flame cannot propagate normally and it blows out.

In order to eliminate these drawbacks, Japanese Patent Application Laid-Open No. 49-50307
Publication No. 1987-33221 (conventional example), and JP-A-57-41417 (conventional example)
Proposals have been made, and these will be explained below.

In the conventional example, as shown in FIG. 5, the piston top 1 is deeply recessed to form the main combustion chamber 2 of a so-called MAN-M type engine, and a small, approximately spherical auxiliary combustion chamber 3 is formed within the cylinder head 20. A communication passage 21 communicating between the combustion chambers 2 and 3 is formed in the cylinder head 20. On the other hand, as shown in FIG. 6, the conventional example also has a piston 6
A main combustion chamber 2 and a sub-combustion chamber 3 are formed inside and inside the cylinder head 20, respectively, and a communication passage 21 connecting them at the top dead center position of the piston 6 is formed tangentially to each other, and a swirl chamber is formed therebetween. 22 is formed.

The sub-combustion chamber 3 of these conventional examples and the conventional example is provided with a fuel injection nozzle 4 facing into the sub-combustion chamber 3 and the main combustion chamber 2, respectively, and when the engine is in low-load operation, the sub-combustion chamber 3 is During high-load operation, fuel injection is performed to mainly inject fuel into the main combustion chamber 2, and the air-fuel ratio (fuel/fuel ratio) during low-load operation is controlled.
The aim is to raise the amount of air (air) and cause excessive combustion, thereby suppressing the production of unburned matter (HC).

However, in the above-mentioned conventional examples and conventional examples, the generation of unburned substances (HC) is suppressed during low loads, and at the same time, the generation of unburned substances (HC) is injected into the main combustion chamber 2 from the communication passage 21 during high loads. Since the fuel spray is ignited by the combustion gas that ignites and burns in the auxiliary combustion chamber 3, it loses its penetrating power, resulting in incomplete combustion in the main combustion chamber 2, resulting in smoke generation and reducing combustion efficiency. I was letting it happen.

Furthermore, in order to eliminate this drawback, a conventional example shown in FIG. A portion of the injected fuel is injected and supplied to the swirl sub-chamber 26 communicating with the cavity 24 through the generation throttle hole 25 to the inner wall 24a of the cavity 24, and the remainder is injected and supplied to the swirl sub-chamber 26 through the throttle hole 25. Equipped with a fuel injection nozzle 4, a swirl subchamber 26
Rapid combustion in the cavity 24 and slow combustion utilizing fuel evaporation in the cavity 24 are used together, the throttle hole 25 is opened in the swirl S direction with respect to the cavity 24, and a sub throttle hole faces in the combustion injection direction;
The combustion chamber of an internal combustion engine has a main throttle hole facing in the swirl direction with respect to the cavity 24, and a part of the combustion chamber is pushed in by the piston compression process to form a vortex flow type vortex chamber, A part of the injected fuel is rapidly combusted within the auxiliary chamber 26, and the remaining injected fuel is burned on the inner wall 2 of the cavity 24.
4a, and the combustion gas rapidly combusted in the auxiliary chamber 26 is ejected into the cavity 24 to generate a large air flow, thereby stretching the fuel adhering to the inner wall 24a of the cavity 24 into a film. , and the resulting fuel evaporation is promoted to achieve slow combustion.

[Problems to be Solved by the Invention] However, in the conventional example configured as described above, the subchamber 2 formed under the cavity 24
There is a possibility that excessive evaporation of the fuel injected onto the inner wall 24a of the cavity 24 may occur due to the rapid combustion gas flow within the combustion chamber 6 and the heat generated thereby.
It is thought that this phenomenon becomes even more noticeable under high loads. In other words, promoting fuel evaporation in the cavity 24 generates a large amount of premixture with excellent ignitability, and when this is ignited by the combustion gas from the pre-chamber 26, rapid combustion occurs. This also occurs within the cavity 24, resulting in an increase in combustion chamber pressure, which has the disadvantage of causing abnormally high noise.

[Object of the Invention] The present invention was devised to solve the above-mentioned problems, and an object of the present invention is to achieve slow combustion without ignition delay over a wide range of operations from low load to high load, and to reduce blue and white smoke. An object of the present invention is to provide a quiet direct injection diesel engine combustion chamber that can reduce combusted unburned matter (HC) and noise.

[Summary of the Invention] In order to achieve the above object, the present invention includes a main combustion chamber that is deeply recessed in the top of the piston, and a main combustion chamber that is shallowly recessed in the top of the piston adjacent to the main combustion chamber. A sub-combustion chamber formed to have a smaller volume than the main combustion chamber, and an upper part of the side wall between the sub-combustion chamber and the main combustion chamber from above in order to communicate the sub-combustion chamber and the main combustion chamber with each other. A recessed bank and an injection nozzle that injects atomized fuel in the forward direction of its swirl into the sub-combustion chamber and toward the inner wall outside the center of the sub-combustion chamber during all operating loads of the engine. , an auxiliary injection nozzle whose jetting direction is determined so that the atomized fuel collides with the inner wall of the auxiliary combustion chamber to form a fuel film on the inner wall of the auxiliary combustion chamber; An injection nozzle that injects atomized fuel having a fuel particle size larger than the atomized fuel in the forward direction of the swirl and toward the inner wall outside the center of the main combustion chamber, the injection direction being the inner wall of the main combustion chamber. and a main injection nozzle designed to cause the fuel spray to collide with the main combustion chamber to form a fuel film on the inner wall of the main combustion chamber.During low load, the fuel is injected from one fuel injection nozzle into the sub-combustion chamber. A part of the atomized fuel spray is instantly evaporated by the swirl generated and confined within the sub-fuel chamber, causing rapid combustion without ignition delay, and the remainder of the fuel spray is used for sub-combustion. The fuel collides with the inner wall of the chamber to form a fuel film that flows along the inner wall of the auxiliary combustion chamber, and this gradually burns slowly, reducing blue-white smoke, unburned matter (HC), and noise.・
When the load is high, a fuel spray with a larger particle size than the above fuel spray is injected from the other fuel injection nozzle into the main combustion chamber, and part of this is evaporated by the swirl generated in the main combustion chamber, and a part of it is evaporated into the sub-combustion chamber. The fuel film is ignited by the combustion gas through the bank part, and the remainder of the combustion spray flows along the inner wall of the main combustion chamber.The flame is gradually propagated through the fuel film, resulting in slow combustion, resulting in blue-white smoke, The aim is to significantly reduce unburned matter (HC) and noise.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be specifically described based on the accompanying drawings.

As shown in FIGS. 1 to 3, the piston top 1 is recessed to form a main combustion chamber 2 and a sub-combustion chamber 3, each having a circular cross-sectional shape, for example, with an open top. ing. Also,
The main combustion chamber 2 and the sub-combustion chamber 3 have mutual peripheral walls 2
A bank 16 is formed by opening part of a and 3a and recessing it from above. The volume ratio of the auxiliary combustion chamber 3 to the main combustion chamber 2 is such that the main combustion chamber 2 has a larger volume than the auxiliary combustion chamber 3, and specifically, the circular cross section of the main combustion chamber 2 is the same as the circular cross section of the auxiliary combustion chamber 3. The auxiliary combustion chamber 3 is formed to have a larger diameter and is recessed shallower than the main combustion chamber 2.

In the vicinity of the bank 16 of the main combustion chamber 2 and the auxiliary combustion chamber 3 formed in this way, a first
As shown in FIG. 2, fuel injection nozzles 4a and 4b, which are connected to a fuel injection pump (not shown), are provided facing the fuel injection nozzles 4a and 4b, respectively.

Specifically, in the sub-combustion chamber 3, there is one sub-nozzle that faces the downstream side of the swirl S generated in the sub-combustion chamber 3 and confined therein, and faces the inner wall 3a of the sub-combustion chamber 3. A fuel injection nozzle 4a is provided. Nozzle port 1 of this one fuel injection nozzle 4a
7, the diameter of the nozzle is reduced to a particle size that is easily evaporated and combusted by the swirl S generated in the sub-combustion chamber 3 and confined therein, that is, it is easy to form a premix F with good ignitability. The nozzle diameter d ₁ is set to inject fuel into the sub-combustion chamber 3 .

On the other hand, in the main combustion chamber 2, the other main nozzle, ie, the fuel injection port, faces the inner wall 2a of the main combustion chamber 2 and is located downstream of the swirl S generated within the main combustion chamber 2 and confined therein. A nozzle 4b is provided. Nozzle port 18 of this other fuel injection nozzle 4b
The nozzle diameter is set to have a relatively large penetration force with respect to the swirl S in the main combustion chamber 2, and a part of the injected fuel is evaporated by the swirl S, and the remainder is injected into the main combustion chamber. In other words, the nozzle diameter d 2 is larger than the nozzle diameter d ₁ of the one fuel injection nozzle 4a so as to form a fuel film H that collides with the inner wall 2a of the second fuel injection nozzle and flows along the inner wall _2a .

In addition, each of the fuel injection nozzles 4a, 4b
For example, depending on the lift amount of the needle valve, etc.,
The injection amount is adjusted and each is configured to be controlled according to the engine state (engine load, engine rotation speed).

Specifically, each fuel injection nozzle 4a, 4b
The injection amount is controlled as shown in FIG.

As shown in the figure, curve a shows the relationship between the nozzle opening/closing time (sec) of fuel injected from one fuel injection nozzle 4a and the lift amount of the needle valve, etc., and the valve opens at t ₀ and the load The valve closes at t ₁ , t ₂ , and t ₃ depending on the time. Curve b represents the opening/closing time (sec) of the injection nozzle 4a for fuel injected from the other injection nozzle 4b.
The relationship between the amount of lift and the lift amount of the needle valve is shown, and it is shown that the valve opens at time t ₂ and closes at t ₄ , t ₅ , and t ₆ .

Since the injection port 17 of one of the injection nozzles 4a is set to have a small injection diameter _d1 , the injection period is lengthened and the injection amount increases as the load increases. In other words, when idling
The injection amount is set to a ₁ (mm ³ ) for the time from t ₀ to t ₁ , but as the load increases, the injection amount is changed to a 2 (light load) for t ₀ to _{t 2} , and at medium load, the injection amount is set to a ₁ (mm 3 ) for the time from t 0 to t ₁ . In addition to the injection amount a ₃ at t ₃ , injection amounts b ₁ and b ₂ are also injected from the other injection nozzle 4b, and as the load becomes higher, the injection amount becomes b ₂ , and at the maximum load, the maximum injection amount is b ₃ . is set to

It is of course possible to electrically control the injection amount shown in FIG. 4 by a CPU or the like that detects and judges the engine state.

Hereinafter, the operation of the present invention will be explained based on the accompanying drawings.

As shown in FIGS. 1 to 3, swirl S supplied from a swirl port (not shown) is generated and confined within the main and sub-combustion chambers 2 and 3, respectively, while being compressed.

Therefore, when the engine is started (idling) or under low load, particulates are released from the nozzle 17 of one fuel injection nozzle 4a into the auxiliary combustion chamber 3, as shown by a ₁ and a ₂ in FIG. 4, depending on the engine condition. fuel spray is ejected. The fuel spray collides with the inner wall 3a of the sub-combustion chamber 3, becomes further atomized, and forms a fuel film H that flows along the inner wall 3a.

Here, a part of the ejected fuel spray has a small particle size and is instantly evaporated by the swirl S to generate a premixture F that is easily ignited and combusted, and the remainder is left on the inner wall of the sub-combustion chamber 3. After being formed into a fuel film H distributed along 3a, it evaporates on the wall surface.

Therefore, as the premixture F is spontaneously ignited and combusted rapidly, the flame is propagated from the ignition position in the sub-combustion chamber 3 toward the inner wall 3a of the sub-combustion chamber 3, and is spread along the inner wall 3a. The flowing fuel film F is gradually and quickly burned.

In this way, since the spray from the nozzle 17 of one fuel injection nozzle 4a is directed toward the inner wall 3a of the sub-combustion chamber 3, most of the fuel is distributed along the inner wall 3a. Furthermore, the ignited thermal energy causes the fuel distributed on the wall surface to gradually evaporate and burn. Sub-combustion chamber 3
is separated from the main combustion chamber 2 by the bank 16, and most of the combustion gas is trapped in the sub-combustion chamber 3 by the swirl S in the sub-combustion chamber 3, causing rapid combustion in the sub-combustion chamber 3. As a result, the combustion temperature increases, and the generation of blue-white smoke and unburned matter (HC) can be suppressed. Therefore, when the load is low, the average combustion temperature in the sub-combustion chamber 3 increases, and as a result, the generation of blue-white smoke and the generation of unburned matter (HC) can be suppressed.

Furthermore, under medium to high load conditions, as explained in FIG. 1st toward the direction
As shown in FIG. 2, fuel is injected, and a fuel film H and a premixture F are produced in the same manner as in the sub-combustion chamber 3 described above. At this time, part of the combustion gas in the auxiliary combustion chamber 3 passes through the bank 16 to the premixture F in the main combustion chamber 2.
The flame propagates, and the fuel film H is further ignited and burned. However, the fuel injected from the nozzle 18 of the other fuel injection nozzle 4b has a larger diameter than the fuel spray injected from the nozzle 17 of the one fuel injection nozzle 4a, and has a larger penetrating force. Preliminary mixture F, which is generated by mixing the two, is not excessively generated. Therefore, even if it ignites, rapid combustion cannot occur within the main combustion chamber 2. Therefore, the heat generated by the ignition of the premixture F quickly evaporates the remaining fuel film H, and this vapor is combusted, resulting in slow combustion. A sudden rise in pressure within the main combustion chamber 2 is suppressed, and noise can be further reduced. Also, as shown in FIG. 4, the higher the load, the more the injection port 18 of the other fuel injection nozzle 4b
Since the amount of fuel injected increases and reaches a maximum of 90% or more, the above effect is reliably achieved and the flame flowing from the sub-combustion chamber 3 reliably ignites.

[Effects of the Invention] As detailed above, the present invention provides the following excellent effects.

(1) By making it possible to perform relatively rapid combustion in the auxiliary combustion chamber and slow evaporative combustion in the main combustion chamber, good combustion is possible under all operating loads, resulting in no blue-white smoke or combusted or unburned smoke. (HC), combustion noise can be significantly reduced.

(2) Low quality fuels with low cetane number or alcohol blends can be used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a preferred embodiment of the present invention, and FIG.
The figure is a schematic cross-sectional view showing the injection direction of the fuel injection nozzle that injects fuel into the main combustion chamber and the sub-combustion chamber of the present invention,
FIG. 3 is a schematic perspective view showing the main combustion chamber and sub-combustion chamber of the embodiment of the present invention formed at the top of the piston, and FIG. 4 is the injection of the fuel injection nozzle shown in FIGS. 1 and 2. The quantity control diagrams, FIG. 5, FIG. 6, and FIG. 7 are diagrams showing conventional examples. In the figure, 1 is a piston top, 2 is a main combustion chamber, 3 is a sub-combustion chamber, 4a, 4b are fuel injection nozzles, 16 is a bank, and 17, 18 are nozzles.

Claims (1)

[Claims] 1. A main combustion chamber that is deeply recessed at the top of the piston, and a sub-combustion chamber that is adjacent to the main combustion chamber and that is shallowly recessed at the top of the piston and whose volume is smaller than that of the main combustion chamber. The combustion chamber, the bank provided by recessing the upper part of the side wall between the auxiliary combustion chamber and the main combustion chamber from above to communicate the auxiliary combustion chamber and the main combustion chamber with each other, and any operating load of the engine. An injection nozzle that injects atomized fuel into a sub-combustion chamber in the forward direction of its swirl and toward an inner wall outside the center of the sub-combustion chamber,
A sub-injection nozzle whose injection direction is determined so that the atomized fuel collides with the inner wall of the sub-combustion chamber to form a fuel film on the inner wall of the sub-combustion chamber, and a swirl inside the main combustion chamber under medium load or higher. an injection nozzle that injects atomized fuel having a fuel particle size larger than the atomized fuel in the forward direction of the main combustion chamber and toward the inner wall outside the center of the main combustion chamber; A direct injection diesel engine combustion chamber comprising a main injection nozzle configured to cause the fuel spray to collide with each other to form a fuel film on the inner wall of the main combustion chamber.