JP2545357Y2 - Combustion chamber of a swirl chamber type diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the shape of a combustion chamber of a swirl chamber type diesel engine.

(Prior Art) As the main combustion chamber shape of a vortex chamber type diesel engine,
The one shown in FIGS. A and B is known. To explain this, a swirl chamber 5 provided in the cylinder head 4 is offset from the center of the cylinder and communicates with a main combustion chamber 9 via an injection hole 6. A groove-shaped trench portion 26 extending radially from a region substantially immediately below the opening of the injection hole 6 on the main combustion chamber side;
A substantially circular cavity portion 10 extending to both sides from a region near the center of the piston 26 is formed, and these form a so-called cloverleaf cavity.

In this swirl chamber type combustion chamber structure, air flowing from the main combustion chamber 9 to the swirl chamber 5 through the injection hole 6 in the compression stroke forms a swirl. Combustion is started by injecting and supplying fuel to the vortex through an injection nozzle (not shown). With the start of combustion in the vortex chamber 5, the expansion gas and a part of the injected fuel are injected through the injection holes 6. Thus, the fuel is jetted into the main combustion chamber 9. The fuel in the ejected gas is guided toward the center of the main combustion chamber 9 along the trench 26 of the piston 3,
Further, as shown by an arrow a in FIG. 4B, the gas is diffused as a swirling flow into the cavity portions 10 on both sides. As a result, the fuel is mixed and burned with the air in the main combustion chamber substantially in the range indicated by the broken line in FIG. (Examples of known structures of this type of combustion chamber include, for example, Japanese Utility Model Laid-Open No. 50-138403 and 57-78.
724, JP-A-54-59512 and the like. (Problems to be Solved by the Invention) However, in such a conventional swirl chamber type combustion chamber, since the trench section 26 is along the direction of the jet from the swirl chamber 5, the trench section 26 Is relatively large in the radial direction from the injection hole 6 and the power of the jet flowing to the side of the trench portion 26 including the cavity portion 10 is relatively weak. For this reason, especially near the base end of the trench portion 26 upstream of the jet and on both sides thereof, the mixing of fuel and air is insufficient, and the air utilization rate tends to decrease. This causes an increase in the concentration of the unburned fuel component in the exhaust during low load operation and an increase in the smoke concentration during high load operation.

The purpose of the present invention is to solve such conventional problems.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, in a combustion chamber of a vortex chamber type diesel engine in which an injection hole from a vortex chamber is opened near an edge of a main combustion chamber, a piston is provided. On the top surface, left and right large cavities that extend in a substantially circular shape from the area near the center of the piston, and outer shells that define left and right side cavities that branch off from the trench below the injection hole and communicate with each large cavity In order that the combustion gas flow from the side cavities merge with the swirling flow of the combustion gas in the large cavity portion in substantially the same direction from the tangential direction, the end thereof merges with the outer periphery of the large cavity portion. A guide portion was formed.

(Function) In the above configuration, a part of the jet of the combustion gas containing fuel from the swirl chamber and the injection hole directly flows into the left and right large cavities, and separates right and left in the downstream area on the piston as viewed from the injection hole. Thereafter, a swirling flow is formed in a mode of returning to the injection hole direction and merging again. Also, a part of the combustion gas jet from the vortex flow chamber is split into the left and right side cavities immediately after exiting the injection hole, and at the end of the side cavities along the guide portion along the guide, the large cavities are formed. It is guided in the direction of merging with the swirling flow. As a result, the jet flow is diffused through the side cavities into both side regions immediately below the injection holes where the combustion gas jet from the swirl chamber is generally difficult to flow, and the swirling flow generated in the large cavity portion is strengthened. Thus, the air utilization over the entire combustion chamber is improved.

In this way, the jet of combustion gas containing fuel is sufficiently diffused over a wide area of the main combustion chamber,
Good combustion properties can be obtained by effectively utilizing the air in the main combustion chamber.

(Example) Hereinafter, an example of the present invention is described based on an accompanying drawing. 4A and 4B are denoted by the same reference numerals as those in FIG.

In FIG. 1A or FIG. 1B, reference numeral 12 denotes a large cavity portion which extends in a substantially circular shape on both sides from a region near the center on the piston top surface 8, and has a circular arc symmetrically with respect to the center line 1 of the jet. It is defined by an outer shell 17 having an arranged shape. This shell
17 has an opposing wall portion 17A projecting in a substantially V-shape on the jet center line l.

Reference numeral 14 denotes a side cavity extending from both sides of the trench 11 below the injection hole 6 and communicating with the large cavity 12.

Reference numeral 13 denotes a dispersion table formed so as to be located on the jet center line l, and each large cavity portion 12 and each side cavity portion 14
Has a shape protruding in an island shape from the bottom surface of the nozzle hole, and the outer shape facing the injection hole 6 projects in a substantially V-shape.

An outer shell defining a side cavity portion 14 with the dispersion table 13
A circular portion 18 extends from the trench portion 11 to the middle along the outline of the piston 3 in a circular shape, and forms a guide portion 18A that gradually reduces the curvature from the middle. The guide portion 18A is curved so that the jet gas flowing into the large cavity portion 12 through the side cavity portion 14 joins the swirling flow of the jet gas generated in the large cavity portion 12 from a substantially tangential direction thereof. I do.

Based on the above configuration, the jet containing unburned fuel that has been jetted from the vortex chamber 5 to the main combustion chamber 9 via the injection hole 6 in the expansion stroke is
It collides with the dispersion table 13 located immediately downstream of the injection hole 6, and as shown by the arrow b in FIG.
14, and the jet flow is diffused laterally also in the vicinity of the trench portion 11, and a part of the jet flow collides with the dispersion table 13 and collides with the substantially V-shaped opposed wall portion 17 </ b> A. As shown by the arrow c, the air flows into the left and right large cavities 12 and is guided by the outer shell 17 to generate a swirling flow.

The jet flowing into the large cavity portion 12 through the side cavity portion 14 is guided by the guide portion 18A and merges with the swirling flow generated in the large cavity portion 12 from a substantially tangential direction as shown by an arrow b. I do. Thereby, generation of stagnation in the vicinity of the junction can be suppressed, and the swirling flow generated in the large cavity portion 12 can be further strengthened.

As a result, as shown by the broken line in FIG. 1B, the diffusion region of the jet is extremely wide as compared with the conventional case, and therefore, the air in the main combustion chamber 9 can be sufficiently utilized to perform efficient combustion. .

Next, in another embodiment shown in FIGS. 2A and 2B, a half-moon-shaped groove 15 is formed on the piston top surface 8 at a position facing the injection hole 6 with the outer shell 17 interposed therebetween.

An outer shell 19 that defines the groove 15 is formed in an arc along the outline of the piston 3, and the jet gas that has passed over the opposing wall 17 </ b> A collides against the outer shell 19, so that the jet gas is released from the inner wall of the cylinder block 1. It is possible to prevent the occurrence of extinction by colliding with 7, thereby reducing HC and smoke.

Next, another embodiment shown in FIGS. 3A and 3B is a groove-shaped straight passage extending radially from the trench portion 11 located immediately below the injection hole 6 to the large cavity portion 20 on the piston top surface 8. In addition to forming the portion 21, a side cavity portion 22 that also extends to both sides from the trench portion 11 and communicates with the large cavity portion 20 is formed. The passage width of the straight passage portion 21 is formed smaller than the opening width of the injection hole 6.

Reference numeral 23 denotes a left and right dispersion table formed so as to be located between the straight passage 21 and the left and right side cavities 22 and the left and right large cavities 20, and from the bottom surface of each large cavity 20 and the side cavities 22. It has a shape protruding like an island.

Outer shell that defines the side cavity portion 22 with the dispersion table 23
25 forms a guide portion 25A that gradually curves as approaching the large cavity portion 20. The guide portion 25A generates a jet flowing through the side cavity portion 22 and flowing into the large cavity portion 20 in the large cavity portion 20. It is curved so as to merge with the jet flow to be formed from a substantially tangential direction.

Also in this case, of the jet gas containing unburned components ejected to the main combustion chamber 9 through the injection hole 6, as shown by an arrow d in FIG. A diverging flow is generated, and joins the swirling flow generated in the large cavity portion 20 from the substantially tangential direction by being guided by the guide portion 25A, but passes through the central passage portion 21 as shown by an arrow e in FIG. The flow diverted to the large cavity section 20 is increased, and the swirling flow in the large cavity section 20 is strengthened. As a result,
As shown by the broken line in the figure, the diffusion region of the jet flow is extremely wide, so that the air in the main combustion chamber 9 can be sufficiently utilized to perform efficient combustion.

(Effects of the Invention) As described above, according to the present invention, the jet flow is diffused through the side cavity portion to the side area just below the injection hole where the jet flow from the vortex chamber is difficult to flow, and the side cavity is formed. The jet flowing through the large cavity is merged with the swirling flow generated in the large cavity from a substantially tangential direction, so that the swirling flow in the large cavity is strengthened, and the air flows over the entire area of the main combustion chamber. The utilization factor can be increased, so that the amount of unburned fuel during low-load operation and the amount of smoke discharged during high-load operation are significantly reduced.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of an essential part of an embodiment of the present invention, and FIG. 1B is a plan view of the piston. FIG. 2A is a longitudinal sectional view of a main part of another embodiment of the present invention, and FIG. 2B is a plan view of the piston. FIG. 3A is a longitudinal sectional view of a main part of still another embodiment,
FIG. B is a plan view of the piston. FIG. 4A is a longitudinal sectional view of a main part of a conventional example, and FIG. 4B is a plan view of the piston. 3 ... Piston, 4 ... Cylinder head, 5 ... Swirl chamber, 6 ... Injection hole, 8 ... Piston top surface, 9 ... Main combustion chamber, 11 ... Trench portion, 12,20 ... Large cavity Part 13,
23 ... Dispersion table, 14,22 ... Side cavity, 18, 25 ...
Outer shell, 18A, 25A …… Guide part.

Claims (5)

(57) [Scope of request for utility model registration] In a combustion chamber of a vortex chamber type diesel engine having an injection hole from a vortex chamber near an edge of a main combustion chamber, the left and right sides of a piston top surface are formed into a substantially circular shape from a region near the center of the piston. A large cavity portion and an outer shell defining left and right side cavities branching from a trench portion below the injection hole and communicating with each large cavity portion are formed laterally with respect to a swirling flow of combustion gas in the large cavity portion. A swirl chamber type diesel engine, characterized in that a guide portion whose end merges with the outer periphery of the large cavity portion is formed so that the combustion gas flow from the cavity portion merges in substantially the same direction from the tangential direction. Combustion chamber. 2. The utility model registration claim according to claim 1, wherein the left and right guide portions of the side cavity portion extend in a direction away from each other along the outer shape of the piston, and then invert and extend in a direction approaching each other. 2. The combustion chamber of a swirl chamber diesel engine according to item 1. 3. A utility model registration characterized in that a semi-lunar groove having an arc-shaped outer portion facing the injection hole is formed at a position facing the injection hole with the large cavity portion interposed therebetween. 3. A combustion chamber for a vortex chamber type diesel engine according to any one of the above items 1 and 2. 4. A dispersing base is raised on the top surface of the piston in an island shape so as to be located on the center line of the jet from the injection hole and substantially in the middle between the side cavity portion and the large cavity portion. The combustion chamber of a vortex chamber type diesel engine according to any one of claims 1 to 3, wherein the utility model is registered. 5. A pair of dispersing bases is raised on the piston top surface in an island shape so as to be located on both sides of the center line of the jet from the injection hole and substantially at the center between the side cavity portion and the large cavity portion. 4. A utility model registration claim according to claim 1, wherein a straight passage portion extending in the radial direction from the trench portion immediately below the injection hole to the large cavity portion and extending in a radial direction between the respective dispersion tables is formed. The combustion chamber of a vortex chamber type diesel engine according to any one of the above.