JPS5862312A - Combustion chamber of direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To reduce smoke and generation of unburnt HC by forming recesses opposedly to a cavity combustion chamber so as to restrain combustion gas from being cooled by the cold wall face thereof. CONSTITUTION:The number of recesses 11 is equivalent to that of holes of a nozzle 6. The recesses 11 are located except in the positions at which fuel is sprayed in the directions 12 against the wall of a cavity. Gas being burnt and unburnt vapor are swerved by the swirl in the direction 13 and then ejected from the recesses 11 into a clearance combustion chamber 7.

Description

[Detailed description of the invention] In particular, in the cavity combustion chamber provided at the top of the piston, by providing a plurality of cavities connected to the cavity combustion chamber, combustion with higher thermal efficiency and less cooling loss than before can be obtained. This is how it was done.

In combustion chambers in which fuel is directly injected into a single combustion chamber formed by a cylinder head and a piston head, piston heads having various concave shapes are used. Among these, the so-called cavity combustion chamber undergoes a swirling motion (17A) during the intake stroke.
The air that has been caused to swirl (swirl) is guided into this combustion chamber during the compression stroke, and is further pushed in to give e4fJft.

Figure 7 shows the combustion chamber of this type of direct injection diesel engine disclosed in Jikko Sho Deku Cococo No. 77.
is a cavity combustion chamber in which the head of the piston is hollowed out, and in this example, a concentric inclined peripheral portion J that is inclined toward the combustion chamber is provided around the combustion chamber.

Now, when the inner surface of the piston cylinder bow is scraped in the suction stroke, #II is formed so that a swirl is generated in the air sucked into the cylinder IK, and when the piston 2 rises in the next pressure M stroke, this Pressure air accompanied by a swirl is forced into the medium cavity combustion chamber l (hereinafter abbreviated as cavity) while generating 114tIt. This figure shows a state in which the piston has risen almost to the top dead center of the clamping stroke.
Fuel is injected from the nozzle of the fuel injection valve that has been pierced by jKd toward this cavity t-i/. Note that the tip of the nozzle 6 is provided with 9Ie nozzle holes (not shown) for fuel injection, and the fuel is injected in the range of directions shown by single-point melting in this figure. It is something.

When the injected fuel vaporizes into the pressurized air, it is promoted by the republican swirl to form a mixture with the air, which causes combustion in the yaviteino and causes the piston 2 to descend.

According to the lower pI# of the piston 2, the burning gas and unburned fuel flow from the cavity l to the clearance combustion '118.
'M? However, at this point, the mixture with air further progresses and the remaining combustion is completed.

In addition, in this example, there is an inclined peripheral edge J around this cavity.
By providing this, in clearance combustion W17, the distance from the lower surface jA of the cylinder head j to the top surface core A of the piston 2 increases as it approaches the cavity. Therefore, in the conventional cavity combustion chamber without the inclined peripheral edge @J, the temperature of the cylinder wall is kept relatively low and moderate.

Bottom surface jA of cylinder head j and top surface JA of piston 2
Since the combustion gas and unburned fuel ejected from the cavity/clearance toward the combustion chamber 7 tended to be cooled, this configuration could alleviate this problem. I can do that. Therefore, especially at high load Q, smoke and unburned He (hydrocarbons)
The effect of suppressing the generation of can be obtained.

However, in the combustion chamber of such a direct injection diesel engine, by providing the inclined peripheral edge sJ, the opening lm of the cavity l is located at a position f lower than the piston top surface core A.
k', the injection angle is constrained in order to inject the fuel into the cavity. Here, the injection angle refers to the angle between the central axis of the sprayed fuel injected from each nozzle hole of the nozzle 6 and the cylinder axis.

That is, if the Jiia edge 3 is provided to prevent the combustion gas and unburned fuel from being cooled, the injection angle will be narrowed, and there is a risk that they will cancel each other out in terms of combustion efficiency. Furthermore, if the peripheral edge J is provided over the entire circumference of the cavity opening/A in this way, in order to secure the desired compression ratio, the volume equivalent to the peripheral edge JK must be reduced from the volume of the cavity L. Moreover, the effect of providing the cavity l is diminished.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a recess at the peripheral edge of the cavity in contact with the nozzle at a position away from the central axis of the fuel injected from the nozzle hole, and from this recess into the cavity. to blow out the combusted gas and unburned fuel toward the clearance area (to prevent smoke and H
K provides a combustion chamber for a direct injection diesel engine that suppresses the generation of C and improves the fuel consumption rate.

In the following, the invention will be explained on fPIIA based on figure rrJK.

In the following, parts similar to those in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

Figure 1 (4) 8 and (B) show an embodiment of the present invention, where ll is a recess provided at the cavity mouth of the piston top surface A/kWc; In the example, recesses are provided at locations corresponding to the number of nozzle holes in the nozzle 6. In FIG. This indicates the direction of fuel flow, and the recess// is provided away from the wall of the cavity 1, which is directly hit by these sprayed fuels.

Now, to explain the combustion operation in the combustion chamber configured in this way, during the intake stroke, the swirl in the cylinder formed by the well-known helical ports and tangential ports (not shown) is caused by the piston 1 during the compression stroke. is guided into the cavity l by the rise of. Here, when the piston 1 has risen to near the top dead center, fuel is injected from the nozzle hole of the nozzle 6, but the sprayed fuel is once placed on the side of the cavity / as shown by the arrow lλ in Fig. 1 (B). After colliding with the wall, it turns with a delay in the direction of the swirl shown by the arrow 13, and during this time it forms a mixture with the compressed air forming the swirl, which ignites and burns.

When the engine is under high load, combustion is not completed only within the cavity, and as the piston descends, the burning gas and unburned fuel vapor flow from the cavity l to the clearance combustion chamber. However, at this point, the flow of combustion gas and unburned fuel is affected by the swirl as described above, so it bends in the direction of
It ejects from the recess provided in 1MM.

That is, as shown in this figure, by providing a recess // in the flow path of the gas tpt'f) which is ejected from the cavity l toward the clearance combustion chamber 7 under the influence of the swirl, this recess I/ In position, the cylinder head underside 5
Since a sufficient distance is secured between the bottom surface of the recess l/ and the lower surface of the cylinder head and the low-temperature area around the cylinder head of the piston top surface -A, combustion gas and unburned fuel vapor are prevented from leaking out. Cooling can be prevented.

Moreover, the position of the cavity opening/m where the recess// is provided is located away from the axis of the fuel injected from the nozzle nozzle hole, that is, the axial direction of the nozzle hole. The opening can be set within the range of the opening @/mu, and it can be made that much larger.
When the piston 2 descends, mixing with the air in the clearance combustion chamber 7 can be promoted. Furthermore, since the recess // does not need to be provided all around the circumference 111J shown in FIG. It is possible to suppress such drawbacks.

In this example, the depth of the recess // is uniform, but the same effect can be obtained by #C so that the depth of the recess /l becomes networked as the distance from the cavity opening lm increases in the radial direction. can be obtained, and if this value is set to 5, the volume of cavity / can be made sufficient by reducing the volume of cess l/ even further.
can be secured.

FIGS. 3(4) and 3(B) show other embodiments of the present invention, and in these figures, the same reference numerals are used for the same parts as in FIG. 1 or 2.

Here, 1 is a recess, and the position where the recess 21 is provided is 1.
As shown in the examples in Figure 1 (4) and (B), if the spray is deviated from the direction of the nozzle nozzle IIJAiI7A? The position of the cavity opening /A is downstream of the recess core, but special consideration has been given to the shape of the recess core.

That is, in this example, in order to make it easier for the swirl air flow to enter the cavity /&C* during the compression stroke, the shape of the recess core 1 is adjusted to the streamline of the air flow flowing into the cavity core 1, taking into consideration the swirl direction IJ. It is roughly semi-elliptical in shape.

By forming the recess core in this manner, the swirling air flow entering the cavity/KtlL is guided without attenuating the swirl. Further, during combustion, the injected fuel becomes a mixture and burns in the direction of the arrow - shown by the dashed dotted line 4, and is ejected from this recess U toward the clearance combustion chamber 7. In other words, by providing the recessco, the combustion gas and unburned fuel are not cooled, and the combustion promotion effect is obtained, as in the example shown in Fig. 2, but the swirl is attenuated. The more the mixture is generated and the combustion promoted, the more fuel efficiency can be expected to improve, and smoke and unburned IC can be suppressed.

Here, if the depth of the recess core is reduced to 5 according to the radial direction of the cavity, the volume of the recess core can be reduced without changing the effect, and sufficient volume can be secured for the cavity. be able to.

As explained above, according to the present invention, the cavity combustion chamber [#-1" part of the recess is located at a position away from the extension line of the nozzle hole axis direction. As a result, the combustion chamber of a direct injection diesel engine can be used without restricting the nozzle injection angle, and by providing a cavity combustion chamber instead of the conventional one, the combustion gas is prevented from being cooled by the low-temperature walls. It is possible to suppress the generation of smoke and unburned HC, especially when the engine is under high load, and it can be expected to improve fuel efficiency.

Also, if the shape of the recess is shaped in relation to the direction of the swirl, it will flow into the cavity.

Swirl can be prevented from fIicR, and even better combustion conditions can be obtained.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the configuration of the combustion chamber of a direct injection diesel engine disclosed in Utility Model Publication No. 1987--Coco J7, g
-1 and (B) are respectively a sectional view and a top view showing an example of the configuration of the combustion chamber of the direct injection diesel engine of the present invention, and Figures 3 (A) and ('B) are other embodiments of the present invention. FIG. 2 is a cross-sectional view and a top view thereof, respectively, showing an example of the configuration in FIG. /...combustion chamber, /mu...opening, co...
・Piston, λm ... Piston top surface, 3
...periphery, da...cylinder, j...
Cylinder head, jA...Bottom surface of cylinder head, 6...Nozzle, ri...Clearance combustion chamber, /c...recess, /c, i3...
Arrow, -ha...recess, 工...arrow. Patent applicant Nissan Motor Co., Ltd. Figure 1 Figure 29 (A) (B)

Claims (1)

[Claims] 1) In the compression stroke, the air that has generated a swirl in the intake stroke is guided into a cavity combustion chamber having an opening on the top surface of the piston, and the air and the injection hole of the injection nozzle are introduced into the cavity combustion chamber. In the combustion chamber of a direct-injection diesel engine, which is configured to mix and burn fuel injected toward 1 [Patent that several bales of IVC are arranged at predetermined intervals, and the part of the recess that connects to the cavity combustion chamber is located away from the axial direction of the injection hole of the injection nozzle. The combustion chamber of a direct injection diesel engine. 2. In the combustion chamber of the direct injection diesel engine according to claim 1, the shape of the front recess is approximately semicircular, which closely matches the streamline of the airflow of the cutting swirl. Combustion chamber of a direct injection diesel engine with 4V image.