JPH059617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a direct injection diesel engine combustion chamber, and more particularly to a direct injection diesel engine combustion chamber that can use low cetane fuel such as gasoline or alcohol as fuel.

[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. The so-called MAN-M method engine is known, which generates a premixture with excellent ignitability by mixing the premixed mixture with the fuel mixture, and spontaneously ignites and burns it. Because the engine was built using a cooling system, it did not have sufficient wall evaporation capacity under conditions of low atmospheric temperature and low engine cooling water temperature. 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 overcome these drawbacks, the present applicant has previously proposed a direct injection diesel engine combustion chamber in Japanese Patent Application No. 59-210519.

This proposal consists of a sub-combustion chamber 3, which is recessed in the piston top 1 and arranged in parallel to the main combustion chamber 2 so as to communicate with each other, as shown in FIG.
It has a main nozzle that spouts fuel facing the direction of the swirl generated therein, and when the main nozzle is closed, it has a main nozzle that faces the direction of the swirl generated within the auxiliary combustion chamber 3. The combustion chamber of the direct injection diesel engine is composed of the fuel injection nozzle and the fuel injection nozzle, which has a sub-nozzle for injecting fuel.

More specifically, the auxiliary combustion chamber 3 is formed to have a smaller volume than the main combustion chamber 2, and each of the combustion chambers 2 and 3 has a circular cross section with an open top. The combustion chambers 2 and 3 are formed so as to have a bank portion by opening a part of their peripheral side walls.

Main and auxiliary combustion chambers 2 and 3 formed in this way
In the combustion chambers 2 and 3, a fuel injection nozzle of, for example, a pintorque nozzle type is provided for supplying atomized fuel.

As shown in FIG. 4, this fuel injection nozzle 4 includes a needle valve 10 that is movable up and down in a nozzle body 7, and when the needle valve 10 is below a predetermined lift, opens a sub-nozzle 11 formed in the nozzle body 7.
When the lift exceeds a predetermined value, the main nozzle 13 formed in the nozzle body 7 is opened and the main and sub-nozzle nozzles 11, 13 are opened.
The fuel is ejected from the fuel tank.

Therefore, under low load, atomized fuel injected into the sub-combustion chamber 3 from the sub-nozzle 11 of the fuel injection nozzle 4 is generated in the sub-combustion chamber 3 and mixed with the swirl S confined therein. The mixture is instantaneously evaporated to produce a premixture F with excellent ignitability. On the other hand, most of the injected atomized fuel collides with the inner wall 3a of the sub-combustion chamber 3 to form a fuel film H that flows along the inner wall 3a of the sub-combustion chamber 3. Since the fuel film H gradually receives heat and evaporates from the inner wall 3a of the sub-combustion chamber 3, when the premixture F is ignited and combusted, the flame is gradually propagated to the fuel film H. Therefore, the fuel in the sub-combustion chamber 3 is combusted while preventing the pressure in the combustion chamber from rising rapidly.

Under high load, fuel spray with a large penetration force and relatively large particle size is injected into the main combustion chamber 2 from the main injection port 13;
Swirl S generated within and trapped in this
It is mixed with and evaporated to form a premixture F with good ignitability. On the other hand, most of the fuel spray is in the main combustion chamber 2.
A fuel film H is formed which collides with and flows along the inner wall 2a of the fuel cell.

Therefore, the premixture F is ignited and combusted by the fire generated in the auxiliary combustion chamber 3, and the flame gradually propagates to the fuel film H that is evaporated by the inner wall 2a of the main combustion chamber 2. As a result, slow combustion within the main combustion chamber 2 is achieved.

[Problems to be solved by the invention] The direct-injection diesel engine combustion chamber configured as described above achieves slow and quiet combustion over a wide range of low-load and high-load operations, and eliminates the generation of blue-white smoke and unburned matter. It is designed to suppress the

However, when the atmospheric temperature is low, the entire engine is cooled, so the combustion chamber cannot have sufficient evaporation capacity at the time of startup. For that reason,
The applicant has inserted a glow plug into the auxiliary combustion chamber to assist the spontaneous ignition of the auxiliary combustion chamber. However, this glow plug cannot demonstrate sufficient ability to ignite unless the cetane number of the supplied fuel is above a certain level, so it is not sufficient to be applied to low cetane number fuels such as pure alcohol and gasoline. Nakatsuta.

[Object of the Invention] The present invention was devised to solve the above-mentioned problems, and an object of the present invention is to reduce the amount of gasoline and
To provide a direct injection diesel engine combustion chamber that can satisfactorily ignite a low cetane number fuel such as pure alcohol, perform slow combustion over the entire load range, and reduce blue-white smoke 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 at the top of the piston;
A sub-combustion chamber, which is provided adjacent to the main combustion chamber by being shallowly recessed at the top of the piston and whose volume is smaller than that of the main combustion chamber, communicates the sub-combustion chamber and the main combustion chamber with each other. A bank is provided by recessing the upper part of each side wall from above between the auxiliary combustion chamber and the main combustion chamber, and a bank is provided facing this bank to contain alcohol, etc., which has a low cetane number and high volatility. A fuel injection nozzle configured to inject fuel into a sub-combustion chamber in the forward direction of its swirl and impinging atomized fuel on an inner wall outside the center of the sub-combustion chamber during all operating loads of the engine. The above-mentioned atomization is carried out in the forward direction of the swirl in the main combustion chamber and on the inner wall outside the center of the main combustion chamber under a predetermined load or more. A fuel injection nozzle configured with a main injection port whose injection direction is determined so that atomized fuel having a particle size larger than the fuel collides with each other to form a fuel film on the inner wall of the main combustion chamber. and an ignition means having an ignition portion located within the sub-combustion chamber.

[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, a piston top 1 is recessed into a main combustion chamber 2 and a sub-combustion chamber 3, each of which has a circular cross-sectional shape, for example, with its top open. ing. Moreover, the main combustion chamber 2 and the sub-combustion chamber 3 have mutual circumferential walls 2a,
A bank portion 16 is formed by opening a part of 3a. The volume ratio of the sub-combustion chamber 3 to the main combustion chamber 2 is such that the main combustion chamber 2 has a larger volume than the sub-combustion chamber 3, and specifically, the circular cross section of the main combustion chamber 2 is larger than the sub-combustion chamber 3.
The auxiliary combustion chamber 3 is formed to have a larger diameter than the circular cross section of the main combustion chamber 2, and is recessed shallower than the main combustion chamber 2.

As shown in FIG. 4, a fuel injection nozzle 4 is provided in the bank portion 16 of the main combustion chamber 2 and the auxiliary combustion chamber 3 formed in this way so as to face it. is attached to a cylinder head (not shown). Also, fuel injection nozzle 4
The main components of the needle valve 10 include a needle valve 10 having a tapered part 9 that is movable up and down on a valve seat 8 in a nozzle body 7 attached to a cylinder head to open and close it; As shown in FIG. 1, the inner wall 3a of the sub-combustion chamber 3 is formed such that the fuel spray injected therefrom is injected toward the downstream side of the swirl S generated within the sub-combustion chamber 3. A sub-nozzle 11 is opened at the tip of the nozzle body 7 and along the axial direction of the needle valve 10.
0, and when the reduced diameter part 12 is opened, the fuel is injected onto the inner wall 2a of the main combustion chamber 2 and downstream in the direction of the swirl S generated therein, as shown in FIG. It is formed from the main nozzle 13.

Further, the sub-nozzle 11 and the main nozzle 13 are each opened according to the lift amount of the needle valve 10, and when the engine is under low load, the sub-nozzle 11 is opened when the lift is below a predetermined level, and the lift is adjusted. The main injection port 13 is now opened, and the fuel required for high-load operation is supplied into the combustion chambers 2 and 3, respectively.

Now, in the embodiment of the present invention, when the fuel injected from the fuel injection nozzle 4 is a low cetane number fuel such as low cetane light diesel oil, gasoline, or pure alcohol, the fuel is Ignition means 15 is provided to ensure ignition and combustion under load.

As shown in FIG. 1, the ignition means 15 is provided so as to hang down facing into the auxiliary combustion chamber 3, and for example, a spark plug or the like is used.

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

As shown in FIGS. 1 to 4, the swirl S supplied from a swirl port (not shown) is generated and confined in the main and sub-combustion chambers 2 and 3, respectively, while being compressed.

Therefore, when the engine is started or under low load, a low cetane number fuel spray is injected from the sub-nozzle 11 of the fuel injection nozzle 4 into the sub-combustion chamber 3. 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, some of the low cetane fuel ejected is
Since the particle size is small, it is instantaneously evaporated by the swirl to generate a premixture F that is easy to ignite and burn.
The remainder is formed on the fuel film H and then evaporated on the wall surface.

Therefore, the ignition means 15 is applied to the premixture F.
By igniting the premixture F, the premixture F is ignited and burned. Due to this ignition, 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 the inner wall 3a
The fuel film F flowing along is gradually burned. In addition, when starting at a low temperature, by adjusting the air-fuel ratio of the fuel, the ignition means 1
It is possible to control the ignitability of the fuel for 5 ignition.

In this way, since the spray from the sub-nozzle 11 is directed toward the inner wall 3a of the sub-combustion chamber 3, much 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. The sub-combustion chamber 3 is separated from the main combustion chamber 2, and most of the combustion gas is trapped within the sub-combustion chamber 3 by the swirl S in the sub-combustion chamber 3, so that combustion within the sub-combustion chamber 3 is achieved. 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 high load, the main nozzle 13
1, the fuel spray is directed toward the inner wall 2a of the main combustion chamber 2 and toward the downstream direction of the swirl S.
As shown in FIG. 2, fuel is injected, and a fuel film H and a premixture F are produced in the same manner as described above. At this time,
A part of the combustion gas in the auxiliary combustion chamber 3 spreads as a flame to the premixture F in the main combustion chamber 2, and then the fuel film H
will be ignited and burned. However, the fuel injected from the main nozzle 13 is
Since it has a larger diameter than the fuel spray that is injected more often and has a greater penetration force, it does not generate excessive premixture F, which is generated by mixing the evaporated fuel and swirl S, so even if it ignites, it will not cause the main combustion. Rapid combustion cannot occur in chamber 2. Therefore, the heat generated by the ignition of the premixture F causes the remaining fuel film H to quickly evaporate, and this vapor is combusted and is slowly combusted. The pressure increase in the main combustion chamber 2 is suppressed, and noise can be further reduced. Also, the higher the load, the more the main nozzle 1
The amount of fuel injected from 3 increases, reaching more than 90% at maximum, so the above effect is reliably achieved and ignition is ensured by the flame flowing from the sub-combustion chamber 3. .

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

Able to burn diesel oil, pure alcohol, gasoline, and other low cetane number, highly volatile fuels normally and stably under all operating loads of the engine, eliminating blue-white smoke, unburned matter (HC), and combustion noise. can be drastically reduced.

[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 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, and FIG. 3 shows the main combustion chamber of the embodiment of the present invention formed at the top of the piston. FIG. 4 is a schematic sectional view of the fuel injection nozzle shown in FIG. 2, and FIG. 5 is a diagram showing a conventional example. In the figure, 1 is the top of the piston, 2 is the main combustion chamber, 3 is the sub-combustion chamber, 4 is the fuel injection nozzle, 11 is the sub-nozzle,
13 is a main nozzle, and 15 is an ignition means.

Claims (1)

[Claims] 1. A main combustion chamber that is deeply recessed in the top of the piston, and a shallow recess that is provided in the top of the piston adjacent to the main combustion chamber, the volume of which is smaller than the main combustion chamber The upper part of the side wall between the auxiliary combustion chamber and the main combustion chamber is recessed from above in order to communicate the auxiliary combustion chamber and the main combustion chamber with each other. A bank and a fuel injection nozzle facing the bank and configured to inject fuel with a low cetane number and high volatility, such as alcohol, into the auxiliary combustion chamber during all operating loads of the engine. The injection direction is determined so that the atomized fuel collides with the inner wall outside the center of the sub-combustion chamber in the forward direction of the swirl to form a fuel film on the inner wall. Forming a fuel film on the inner wall of the main combustion chamber by colliding atomized fuel with a fuel particle size larger than the above-mentioned atomized fuel against the inner wall of the combustion chamber in the forward direction of the swirl and outside the center of the main combustion chamber. The present invention is characterized by comprising: a fuel injection nozzle having a main nozzle whose injection direction is determined such that the injection direction can be determined; and an ignition means having an ignition portion located within the auxiliary combustion chamber. direct injection diesel engine combustion chamber. 2. The direct injection diesel engine combustion chamber according to claim 1, wherein the ignition means comprises a spark plug.