JPH063133B2 - Combustion chamber of direct injection diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a combustion chamber of a direct injection type diesel engine in which fuel oil is directly injected into a combustion chamber, and in particular, low cetane number and volatilization of gasoline, alcohol, etc. as fuel oil. The invention relates to a combustion chamber of a direct injection diesel engine that can use organic fuel.

[Prior Art] In general, as a fuel oil that can be used as a poor fuel oil such as methanol (methyl alcohol), there is a method disclosed in Japanese Utility Model Laid-Open No. 57-10782.
A proposal of a methanol stratified charge engine described in Japanese Patent No. 0 is known, and in this proposal shown in FIG. 4, a pre-combustion chamber b is provided on the side of the top end of a cylinder a, and a bottom wall portion of the pre-combustion chamber b is provided. c
And a fuel injection valve e facing the preheating plug d, and a spark plug f between the fuel injection valve e and the preheating plug d. It is what is done.

[Problems to be Solved by the Invention] In the above-mentioned proposal, at the time of starting the engine, in order to improve the light load operability, a glow plug is used to ignite and burn the fuel in a high temperature atmosphere in the precombustion chamber. Is.

However, since the pre-combustion chamber b and the main combustion chamber g are communicated by the sloak h, the throttle loss when pushing the compressed air into the pre-combustion chamber b and the combustion gas from the pre-combustion chamber b enter the main combustion chamber g. The diaphragm loss when pushed in was large, and the thermal efficiency decreased due to these losses. This decrease in thermal efficiency lowers the combustion temperature in the main combustion chamber, so the output decreases.
There is a risk of increasing unburned substances such as HC. Also, at the time of a low temperature start when the atmospheric temperature exceeds -20 ° C, the amount of injected fuel oil must be increased for that start, and the fuel oil must have a small latent heat of vaporization such as methanol. In order to generate an air-fuel mixture that is difficult to be vaporized from and can assist the spark plug, it requires a long heating time and measures such as increasing the heat generation capacity of the glow plug are required. It was not preferable from the viewpoint of starting time and the like.

[Object of the Invention] The present invention was devised to solve the above-mentioned various problems. An object of the present invention is to provide a combustion chamber of a direct injection diesel engine capable of satisfactorily burning a low cetane number and volatile fuel oil such as alcohol or gasoline in a full load operation range including a low temperature start.

[Summary of the Invention] In order to achieve the above object, the present invention is provided with a main combustion chamber deeply recessed in a piston top portion, and a shallow depression in the piston top portion adjacent to the main combustion chamber. An auxiliary combustion chamber having a smaller volume than the main combustion chamber, and a bank formed by radially opening upper side walls of the main combustion chamber and the auxiliary combustion chamber. A glow plug having its heating portion located in the auxiliary combustion chamber, and an ignition plug having the ignition portion disposed in the auxiliary combustion chamber at a downstream side of the swirl adjacent to the ignition portion. , The sub-injection port that is provided with its injection port facing the bank section and supplies atomized fuel spray to the vicinity of the glow plug under any load, and the atomized fuel spray into the main combustion chamber when the load is exceeded. Larger particle size And a fuel injection nozzle formed having a main injection port for supplying atomized fuel.

Therefore, the atomized fuel spray injected from the sub-injection instantly becomes an air-fuel mixture with good ignitability and combustibility due to the heating atmosphere in the glow plug or in the vicinity of the glow plug, and is promptly ignited by the spark plug downstream thereof. To burn. Then, the atomized fuel supplied into the main combustion chamber after exceeding the low load is flame-propagated by the flame and combustion energy of the auxiliary combustion chamber.

[Embodiment] A preferred embodiment of the combustion chamber of the direct injection diesel engine of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the piston top 1 has
The main combustion chamber 2 and the sub-combustion chamber 3 are recessed from this, and are formed so as to have, for example, circular cross-sections whose upper portions are opened. Further, the main combustion chamber 2 and the auxiliary combustion chamber 3 are
The bank portion 4 is formed by opening the upper portions of the peripheral side walls 2a and 3a. The volume ratio of the sub-combustion chamber 3 and the main combustion chamber 2 is such that the main combustion chamber 2 is formed to have a larger volume than the sub-combustion chamber 3, and specifically, the circular cross section of the main combustion chamber 2 is a circle of the sub-combustion chamber 3. The auxiliary combustion chamber 3 is formed to have a larger diameter than the cross section, and the auxiliary combustion chamber 3 is shallower than the main combustion chamber 2.

An injection nozzle 5 is provided in the bank portion 4 of the main combustion chamber 2 and the auxiliary combustion chamber 3 thus formed so as to face the bank portion 4. The injection nozzle 5 is provided in a cylinder head (not shown). It is installed facing those combustion chambers. The main structure of the injection nozzle 5 is, as shown in FIG. 3, a needle valve having a taper portion 9 that seats in a vertically movable manner on a valve seat 8 in a nozzle body 7 mounted on a cylinder head to open and close the seat. 10 and a sub-injection port 1 which is opened from the valve seat 8 and ejects atomized fuel spray having a small penetration force.
1 and the nozzle body 7 and the needle valve 10 are opened along the axial direction of the needle valve 10 and accommodate the reduced diameter portion 12 of the needle valve 10. It is formed from a main injection port 13 that ejects fuel spray.

Further, the auxiliary injection port 11 and the main injection port 13 are opened by the lift amount of the needle valve 10, and when the engine has a low load, the auxiliary injection port 11 is below a predetermined lift.
Is opened, and above the lift, the sub nozzle 11 and the main nozzle 1
3 is opened and fuel is injected and supplied into the combustion chambers 2 and 3, respectively.

In the embodiment of the present invention, when the fuel injected from the injection nozzle 5 is a low cetane number fuel such as gasoline or pure alcohol, the fuel is surely ignited and burned in a low temperature atmosphere under a low load. For the spark plug 15
And a glow plug 16 are provided. Spark plug 1
5 and the glow plug 16 are provided so as to project into the auxiliary combustion chamber 3, and the glow plug 1 provided in the auxiliary combustion chamber 3
6 the spark plug 15 is the glow plug 1
It is provided on the downstream side in the swirl direction in the vicinity of 6.

On the other hand, the direction of the auxiliary injection port 11 of the injection nozzle 5 is provided so as to face the glow plug 16 or in the vicinity of the glow plug 16, and the main injection port 13 is provided on the inner wall 2a of the main combustion chamber 2. Moreover, it is provided toward the downstream side of the main combustion chamber 2 in the swirl direction.

The operation of the embodiment of the combustion chamber of the internal combustion engine of the present invention will be described below with reference to the accompanying drawings.

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

When the engine is started, the needle valve 1 of the injection nozzle 5
0 is lifted, but the needle valve 10 at the time of cold start is set to a rotation speed of the injection pump of 50 rpm to 150 rpm when the internal combustion engine is driven by the starter, a so-called excessive supply state (more than at full load). (State), the fuel flow velocity is extremely low, so that the lift value is kept low to open only the sub injection port 11. As a result, a large amount of atomized fuel spray F ₁ is supplied into the auxiliary combustion chamber 3. Since the atomized fuel spray F ₁ is ejected toward the glow plug 16 or the vicinity of the glow plug 16, the atomized fuel spray F ₁ is acceleratedly vaporized by the compressed air further heated by the glow plug 16 and mixed with the air, and the ignition and combustion property is excellent. The fuel vapor layer F ₃ is generated.
The fuel vapor layer F ₃ is reliably ignited by igniting the spark plug 15 when it is flowed downstream by the swirl S and distributed around the spark plug 15. When the atomized fuel spray F ₁ is made to collide with the sub-combustion chamber inner wall 3a on the upstream side in the swirl direction near the glow plug 16, the atomized fuel spray F ₁ further promotes atomization of the fuel spray and vapor. Since the gasification / mixture vaporization is accelerated, a rich mixture is generated in the auxiliary combustion chamber 3 and rich combustion is performed. After the cold start, the auxiliary combustion chamber 3
The inner wall 3a is heated by the combustion energy and reaches a wall temperature sufficient to vaporize the fuel oil, so that the atomized fuel spray F ₁ from the auxiliary injection port 11 is stably ignited and burned at the time of light load of the engine. Since the sub combustion chamber 3 is separated from the main combustion chamber 2 via the bank portion 4 and most of the combustion gas is confined in the sub combustion chamber 3 by the swirl S in the sub combustion chamber 3, Therefore, the inside of the auxiliary combustion chamber 3 can be set to a predetermined air-fuel ratio without letting the fuel vapor escape into the inside.
Therefore, use a low cetane number and volatile fuel oil such as alcohol,
Rapid combustion can be performed in the auxiliary combustion chamber 3. As a result, the combustion temperature rises, and it is possible to suppress the generation of bluish white smoke and combustion unburned matter (HC), and when the load is low,
The average combustion temperature in the sub-combustion chamber 3 rises, and as a result, generation of bluish white smoke and combustion unburned matter (HC) can be suppressed.

Further, at the time of high load, fuel spray is injected from the main injection port 13 toward the inner wall 2a of the main combustion chamber 2 and toward the downstream side of the swirl S as shown in FIGS. 1 and 2. It In the main combustion chamber 2, fuel spray F ₂ from the main injection port 13
Is injected toward the inner wall 2a of the main combustion chamber 2, the fuel film H flowing downstream of the swirl S along the inner wall 2a.
To generate. This fuel film H produces the above-mentioned fuel vapor layer F ₃ in the main combustion chamber 2 by the combustion energy of the auxiliary combustion chamber 3, the high temperature compressed air and the inner wall heat. This vapor layer F ₃ is propagated through the flame in the auxiliary combustion chamber 3 and good combustion is performed. At that time, the particle size of the fuel injected from the main injection port 13 depends on the auxiliary injection port 1
1 has a larger diameter than the fuel particle size injected and has a large penetration force, so that the fuel vapor layer F ₃ generated by mixing the evaporated fuel and the compressed air is not excessively generated, which causes ignition. However, rapid combustion cannot occur in the main combustion chamber 2. Therefore, the remaining fuel film H is quickly evaporated by the heat generated by the ignition of the fuel vapor layer F ₃ , and this vapor is burned to cause slow combustion, which causes a rapid main combustion. The pressure rise in the combustion chamber 2 is suppressed, and noise can be further reduced. Further, as the load becomes higher, the amount of fuel injected from the main injection port 13 increases, and 90% or more of the fuel is injected at the maximum, so the above-mentioned action is reliably achieved, and the flame flowing from the auxiliary combustion chamber 3 surely ignites. Burning takes place.

[Effects of the Invention] As described in detail above, according to the present invention, the following excellent effects are exhibited.

Pure alcohol, gasoline, etc. can be satisfactorily ignited and burned under any use load including cold start, and reduction of white smoke, unburned combustibles (HC) and noise can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a preferred embodiment of a combustion chamber of a direct injection diesel engine of the present invention, and FIG. 2 is an injection direction of a fuel injection nozzle for injecting fuel into a main combustion chamber and a sub combustion chamber of the present invention. FIG. 3 is a schematic sectional view of the injection nozzle, and FIG. 4 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 auxiliary combustion chamber, 5 is the injection nozzle, 11 is the auxiliary injection port, 13 is the main injection port, 1
5 is a spark plug and 16 is a glow plug.

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Claims (1)

[Claims] 1. A main combustion chamber which is deeply recessed at the top of a piston, and a sub combustion chamber which is recessed shallowly at the top of the piston so as to be adjacent to the main combustion chamber. A sub-combustion chamber formed to have a smaller volume, a bank formed by radially opening upper portions of peripheral walls of the main combustion chamber and the sub-combustion chamber, and a heating unit located in the sub-combustion chamber. The glow plug disposed in the sub-combustion chamber, the ignition plug disposed in the auxiliary combustion chamber at a position downstream of the swirl adjacent to the ignition part, and the injection port part thereof facing the bank part. The atomized fuel with a particle size larger than that of the atomized fuel spray is supplied into the main combustion chamber from the auxiliary injection port that supplies the atomized fuel spray to the vicinity of the glow plug under any use load and when the low load is exceeded. With a main spout to be shaped A combustion chamber of a direct injection diesel engine comprising the fuel injection nozzles.