JPH082425Y2 - Sub-chamber diesel engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sub-chamber diesel engine.

2. Description of the Related Art As a conventional sub-chamber diesel engine of this type, for example, one shown in FIG. 5 is known.

In brief, a main combustion chamber 4 is formed between a lower surface 2a of a cylinder head 2 arranged on a cylinder block 1 and a top surface 3a of a piston 3, and a sub chamber inside the cylinder head 2 is formed. A barrel-shaped substantially spherical vortex flow chamber 5 is formed, and the vortex flow chamber 5 and the main combustion chamber 4 communicate with each other through a jet port 6 having a substantially elliptical cross section. Also, the piston 3 is
As shown in FIG. 6, a cloverleaf-shaped cavity 7 is formed on the top surface 3a, and a straight rectangular passage groove 8 continuous with the cavity 7 is formed immediately below the injection port 6. There is. Further, a fuel injection nozzle (not shown) and a glow plug for improving startability are provided in the swirl chamber 5.

As is well known, the air in the main combustion chamber 4 is pressure-fed from the nozzle 6 into the swirl chamber 5 as the piston 3 rises, thereby generating a strong swirl inside. On the other hand, when the piston 3 reaches the substantially top dead center position, the fuel is injected from the injection nozzle into the swirl chamber 5, mixed with the swirl air, and self-ignited by the compression temperature. Next, during the expansion stroke of the piston 3, the ignition fuel is ejected from the injection port 6 into the main combustion chamber 4, flows into the cavity 7 from the passage groove 8, and the cavity 7
It is designed to be completely combusted in the main combustion chamber 4 (see Japanese Utility Model Laid-Open No. 174725/1982).

On the other hand, as another conventional example, the one disclosed in Japanese Utility Model Laid-Open No. 52-30511 discloses that a main injection port groove portion is formed along the diametrical direction on the top surface of the piston and the main injection port is formed. Valve recesses for intake and exhaust valves are formed on both sides of the tip of the groove. Sub-injection groove portions are formed on both sides of the main injection-port groove portion on the base end side, and a communication groove is formed between the sub-injection groove portions and the valve recess for communicating the both. Furthermore, the depth of each of the main nozzle hole, the auxiliary nozzle groove,
The valve recess and the communication groove are formed shallower in this order.Fuel is ejected from the main injection hole along the piston center direction to the main injection hole groove portion, and from each sub injection hole groove portion along the piston circumferential direction. , The air utilization rate is improved by jetting from multiple directions.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the former conventional sub-chamber diesel engine in the former case, the direct combustion action of the jet fuel in the straight passage groove 8 is relatively strong, and thus the main combustion of the jet fuel is performed. The air utilization rate in the room will be low. That is, the ignition fuel ejected from the swirl chamber 5 through the injection port 6 is guided in a substantially straight direction by the passage groove 8 as shown in FIG. 6, and a part of the ignition fuel impinges on the front wall 7a of the cavity 7 and the arrow While turning in the cavity 7 along the a direction,
Others get over the front wall 7a and flow forward as shown by the broken line. Therefore, although the air can be sufficiently utilized in the forward region P, the state of mixing with the air in the left and right regions S, S of the passage groove 8, that is, the air utilization rate becomes low. As a result, there is a problem in that a good combustion state cannot be obtained in the main combustion chamber 4, the HC concentration in the exhaust gas becomes high when the engine load is low, and the smoke concentration becomes high when the engine load is high.

On the other hand, in the latter conventional example, although the injected fuel can be smoothly guided in the swirl rotation direction by changing the depth of each groove or the like, the fuel injection is performed from one main injection hole to the main injection groove. Since they are jetted to each of the two sub-jet nozzles or each sub-jet nozzle groove, the jet flow of the main jet nozzle groove collides with the cylinder wall through the center of the piston top surface, splits left and right as it is, and circulates in the circumferential direction of each cylinder. While flowing into the side, the jet flow of each sub-injection groove portion is guided by the sub-injection groove portion and the communication groove and wraps around in the tip direction of the main injection hole groove. Therefore, since the respective opposing flows passing through the main injection hole groove portion and the respective auxiliary injection hole groove portions flow into the valve recess, it is impossible to generate a swirling flow in a fixed direction in the valve recess. As a result, I cannot get a strong swirl force,
It is difficult to sufficiently improve the air utilization rate in the main combustion chamber.

Means for Solving the Problems The present invention has been devised in view of the above-mentioned conventional problems, and forms a main combustion chamber between a cylinder head lower surface and a piston top surface, and A sub-chamber is formed inside, and an opening is formed in the vicinity of the edge of the main combustion chamber at the lower part of the cylinder head. A communicating Fukumuro diesel engine, which is formed in the vicinity of the outer peripheral portion of the top surface of the piston 3, and which is continuous with a passage groove for guiding a jet flow from the injection port toward the piston center and a tip side of the passage groove. A main cavity that is formed as a circular groove and extends in a circular shape on both sides of the passage groove, and a convex portion that smoothly connects the front end side outer contour of the main cavity and that stands up against the jet flow from the injection port. , Above main cavite A sub-cavity that is formed on both sides of the passageway near the passage groove, is discontinuous with the passage groove, is continuous with the main cavity, and has a shallower depth than the main cavity. It is characterized in that a part of the jet flow ejected to the above is swirled to the vicinity of both sides of the passage groove by the sub-cavity.

Further, it is characterized in that the auxiliary cavities formed on both sides of the main cavity near the passage groove are formed in a fan shape that expands outward from the main cavity.

Further, it is characterized in that the sub-cavities formed on both sides of the main cavity near the passage groove are formed in an arc shape expanding outward from the main cavity.

The ignition fuel injected from the injection port into the main combustion chamber is guided only by the passage groove toward the center of the piston, that is, in the vicinity of the center of both main cavities. Generate a swirling flow in the.
In addition, a part of the jet flow that hits the convex portion flows over the convex portion as it is, flows in the forward direction, and is split into right and left along the cylinder wall surface and diffused. Further, a part of the swirling flow in the main cavity flows into the sub cavity, and the jet flow is diffused in the regions on both sides of the passage groove.

In particular, since the sub-cavity is discontinuous with the passage groove, a part of the jet flows into the main cavity after the passage groove passes through the sub-cavity, in combination with the structure that ejects the jet flow only in the piston center direction. However, it does not collide with the jet flow guided into the convex portion and flowing into the main cavity. Therefore, the flow of the jet flow in the main cavity is only the flow that is guided by the convex portion and flows into the main cavity, and a strong swirling flow can be obtained.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
It should be noted that the same components as those of the above-described conventional device will be described with the same reference numerals.

FIG. 1 shows a first embodiment of a sub-chamber diesel engine according to the present invention.

In the figure, 1 is a cylinder block, 2 is a cylinder head, 3
Is a piston, 4 is a main combustion chamber formed between the lower surface 2a of the cylinder head 2 and the top surface 3a of the piston 3, 5 is a swirl chamber which is a sub chamber formed inside the cylinder head 2, and 6 is main combustion As shown in FIG. 2, the piston 3 is an injection port that connects the chamber 4 and the swirl chamber 5, and a cloverleaf-shaped main cavity 7 is formed on the right side of the center line X of the top surface 3a. A straight rectangular passage groove 8 which is continuous with the main cavity 7 is formed immediately below the injection port 6.

The injection port 6 has a cylinder head 2 as shown in FIG.
An opening is formed near the edge of the lower main combustion chamber 4 so as to connect the main combustion chamber 4 and the swirl chamber 5, and the tip portion is directed toward the center of the top surface 3a of the piston 3. As shown in FIG. 2, the main cavity 7 is formed continuously on the tip side of the passage groove 8 and extends in a circular shape on both sides of the passage groove 8. Further, as shown in FIG. 1, the main cavity 7 has the same depth as that of the passage groove 8 and a uniform depth as a whole, and is located at the front position thereof, that is, facing the passage groove 8. The front peripheral wall 7a, which is a convex portion, is provided at the position. The passage groove 8 is formed near the outer peripheral portion of the top surface 3a of the piston 3 on the base end side, and has the tip directed toward the center of the top surface 3a of the piston 3 via the main cavity 7.

Then, near the passage grooves 8 on both sides of the main cavity 7,
That is, the sub-cavities 11, 11 are formed at positions slightly apart from both ends of the passage groove 8. That is, the sub-cavities 11, 11 are formed discontinuously with the passage groove 8. More specifically, the sub-cavities 11 and 11 have a fan shape that expands outward from the main cavity 7 by about 90 °, and each inner edge has a passage groove 8 and each outer edge has the center line X. They are arranged parallel to each other, and are formed shallower and flatter than the depth of the main cavity 7. Also, the inner edge of the small arc
11a, 11a are formed continuously with the rear peripheral walls 7b, 7b of the main cavity 7, and large arcuate outer edges 11b, 11b extend to the outer edge of the piston 3. The depth from the lower surface 2a of the cylinder head 2 increases in the order of the piston top surface 3a, the sub cavity 11, and the main cavity 7.

According to this embodiment having the above-described structure, the ignition fuel ejected from the swirl chamber 5 into the main combustion chamber 4 through the injection port 6 during the expansion stroke of the piston 3 travels straight by the passage groove 8 as shown in FIG. Part of the main cavity 7 passes over the front peripheral wall 7a of the main cavity 7, flows forward, and abuts on a cylinder wall (not shown). Further, from here, the auxiliary cavities 11 and 11 are branched while generating a swirling flow by branching in the left and right direction as shown by arrow b.
It is possible to wrap around to the side and effectively use the air in the front area of the jet.

On the other hand, the other ignition fuel that has proceeded straight from the passage groove 8 hits the front peripheral wall 7a of the main cavity 7 and remains as it is.
Along which the swirl flow is generated by splitting to the left and right as indicated by arrow a, and from there, as shown by arrow c, the swirl flow is further crossed over the rear peripheral walls 7b, 7b and quickly flows into the sub-cavities 11, 11. Therefore, the jet flow that has passed over the front peripheral wall 7a collides with the wall surface of the cylinder, splits as shown by arrow b, and diffuses, so that the air in front of the main cavity can be effectively used.

Further, the jet flow hitting the front peripheral wall 7a is divided in the main cavity 7 as shown by an arrow a to become strong swirl flows in mutually opposite directions, and a part of the jet flow into the sub cavities 21 and 21. The effective use of the air in the main cavity 7 can be achieved, and the effective use of the air in the wide area up to the both sides of the sub-cavities 21, 21, that is, the passage grooves 8 where the jet flow is difficult to reach can be achieved.

In particular, since the sub-cavities 21 and 21 are discontinuous with the passage groove 8, the jet flow is ejected only toward the center of the piston 3 as described above, and the jet flow from the passage groove 8 to the sub-cavity. It is possible to sufficiently prevent the particles from directly flowing into 21, 21 and then into the main cavity 7 and colliding with the swirling flow in the main cavity 7. Therefore, the swirling direction of the jet flow in the main cavity 7 becomes constant, and a strong swirl can be obtained. As a result, as described above, the utilization rate of air in the main combustion chamber 4 is improved, combustion can be improved, and the HC concentration in the exhaust gas at low engine load and the smoke concentration at high load can be made sufficient. Can be lowered. As a result, combustion is improved and the amount of smoke and HC in the exhaust gas is reduced.

FIG. 3 shows a second embodiment of the present invention, the first embodiment
The difference from the embodiment is that the auxiliary cavities 21 and 21 arranged on both sides of the passage groove 8 are formed in an arc shape as shown in FIG. That is, this sub-cavity
As for 21,21, each inner end edge 21a, 21a is continuously formed on the substantially central peripheral wall 7c, 7c of the main cavity 7, and each outer end edge 21b, 21b is arranged slightly inward from the outer edge of the piston 3, that is, , Inner wall 2
It is formed in a shape surrounded by 2,22. The other structure is the same as that of the first embodiment.

Therefore, in this embodiment, part of the ignited fuel can be sufficiently utilized in the front direction of the main cavity 7 by the passage groove 8, while the other hits the front peripheral wall 7a of the main cavity 7 in the left and right direction in the arrow a direction. Divide and split sub-cavity 21,2
Since it enters the inside of 1 and swirls along the inner wall 22 as shown by the arrow d, a strong swirling flow is obtained and the mixing action with air is promoted. This can further reduce the amount of smoke and HC in the exhaust gas.

Needless to say, the fuel injection nozzle and the glow plug are arranged in the swirl chamber of each of the above embodiments.

Effects of the Invention As is clear from the above description, according to the sub-chamber diesel engine according to the present invention, the ignition fuel ejected from the sub-chamber into the main combustion chamber during the expansion stroke of the piston causes the air in the pre-ejection direction to be emitted. Not only can it be used effectively, but the ignition fuel that hits the convex part splits in the main cavity into strong swirling flows in opposite directions, and part of it flows smoothly into each sub-cavity, so It is possible to effectively use the air inside and near both sides of the passage groove.

In particular, since the sub-cavity and the passage groove are discontinuous, the ignition fuel injected into the passage groove is prevented from flowing into the main cavity from the sub-cavity. Therefore, collision with the swirl flow in the main cavity is prevented, and a strong swirl flow is maintained in the main cavity, which further improves the effective utilization rate of air. As a result, combustion in the main combustion chamber can be improved, and the HC concentration in the exhaust gas when the engine load is low and the smoke concentration when the engine load is high can be sufficiently reduced.

[Brief description of drawings]

1 is a sectional view showing a first embodiment of a sub-chamber diesel engine according to the present invention, FIG. 2 is a view taken along the line II-II of FIG. 1, and FIG. 3 is a second embodiment of the present invention. Sectional view showing No. 4
FIG. 5 is a sectional view taken along the line IV-IV of FIG. 3, FIG. 5 is a sectional view of a conventional sub-chamber diesel engine, and FIG. 6 is a sectional view taken along the line VI-VI of FIG. 2 ... Cylinder head, 2a ... Lower surface, 3 ... Piston, 3a ... Top surface, 4 ... Main combustion chamber, 5 ... Vortex chamber (sub chamber), 6 ... Injection port, 7
… Main cavities, 8… Passage grooves, 11,12… Sub cavities.

Claims (3)

[Scope of utility model registration request] 1. A main combustion chamber is formed between a lower surface of a cylinder head and a top surface of a piston, and a sub chamber is formed inside the cylinder head, and near the edge of the main combustion chamber below the cylinder head. A sub-chamber type diesel engine in which the main combustion chamber and the sub-chamber are communicated with each other only by an injection port whose opening is formed in the direction of the center of the piston and which is formed near the outer peripheral portion of the top surface of the piston. , A passage groove for guiding the jet flow from the injection port toward the center of the piston, a main cavity formed continuously on the tip side of the passage groove, and extending in a circular shape on both sides of the passage groove; The front end side contour is smoothly continuous, and is provided upright to face the jet from the nozzle, and is formed on both sides of the main cavity near the passage groove, and is not continuous with the passage groove. cavity And a sub-cavity having a shallower depth than the main cavity, and a part of the jet flow ejected from the nozzle through the passage groove into the main cavity is swirled by the sub-cavity to the vicinity of both sides of the passage groove. A sub-compartment diesel engine characterized by this. 2. A utility model registration claim according to claim 1, wherein the auxiliary cavities formed on both sides of the main cavity near the passage groove are formed in a fan shape that expands outward from the main cavity. The sub-chamber diesel engine described in the item. 3. A utility model registration claim characterized in that the sub-cavities formed on both sides of the main cavity near the passage groove are formed in an arc shape expanding outward from the main cavity. The sub-chamber diesel engine according to item 1.