JPH0643808B2 - Vortex chamber combustion chamber of diesel engine - Google Patents

Description

The present invention relates to a swirl chamber type combustion chamber of a diesel engine.

[Conventional technology]

As is well known, the basic structure of the swirl chamber type combustion chamber of a diesel engine is as follows.

For example, as shown in FIG. 1, FIG. 7 or FIG. 8, the swirl chamber 1 is formed in the rearward portion of the main combustion chamber 2, 102, 202.
・ 101 ・ 201 is replaced by a nozzle 103 ・ 103
..Communication via 203

Note that, for convenience of description, with respect to the “front / rear” direction, the side where the swirl chamber 1 is located is referred to as the rear side, and the opposite side and the front side, as viewed from the axial center of the main combustion chamber 2. . (Hereinafter, the same) In this basic structure, as the shapes of the injection holes 3, 103, 203, there are the following in the prior art.

◎ Conventional technology. See FIG. 7. The injection port 103 is in the form of a parallel hole having a constant diameter over its entire length.

◎ Prior application technology. See FIG. 8 (FIG. 2 of Japanese Utility Model Application Laid-Open No. 61-91029) The injection port 203 is formed in a downwardly widening tapered hole shape.

[Problems to be Solved by the Invention]

 The above-mentioned conventional technology and prior application technology have the following problems.

◎ Conventional technology. See FIG. 7. (a) Low air utilization ratio in the rear part 151 of the main chamber During the explosive expansion action, the combustion gas that has begun to combust and expand in the swirl chamber 101 is entirely in the form of parallel holes of the injection port 3. It is guided obliquely forward and downward, and flows from the central portion of the main chamber in the main combustion chamber 102 to the front portion of the main chamber.

Then, in the main combustion chamber 102, the rear portion 15 of the main chamber located from the left and right sides to the rear side of the opening position of the injection port 3.
In the case of 1, the combustion gas is hard to reach and the air utilization rate becomes low.

The maximum torque and maximum output are reduced by the lower air utilization rate.

(B) At the time of high load operation in which incomplete combustion occurs in the central portion of the main chamber and the front portion of the main chamber, as much as the air utilization rate in the rear portion 151 of the main chamber of the main combustion chamber 102 decreases, Incomplete combustion occurs due to fuel enrichment in the central part of the main chamber or the front part of the main chamber.

As a result, the fuel consumption rate increases, and the amount of unburned harmful components such as C, CO, and HC in the exhaust gas increases.

◎ Prior application technology. See FIG. 8 (c) Incomplete combustion occurs in the rear portion 251 of the main chamber. At the time of explosive expansion, the fuel gas that has started to combust and expand in the swirl chamber 201 follows the shape of the downwardly widening tapered hole of the injection port 3. And flows into both the front and the rear, and flows into the main combustion chamber 202.

Then, in the main chamber rear part 251 of the main combustion chamber 202, which is located on the injection port 3 side when viewed from the cylinder axis, the inflow of combustion gas becomes too large for its small volume,
Incomplete combustion occurs due to lack of air.

As a result, the fuel consumption rate increases and the unburned harmful components in the exhaust gas increase.

(D) The air utilization ratio in the front part of the main chamber is low. Combustion to the front part of the main chamber located on the opposite side to the amount that the flow rate of the fuel gas to the rear part 251 of the main chamber becomes too large. Gas flow rate is reduced.

In addition, the flow rate of the combustion gas is reduced by the decrease in the flow rate of the combustion gas. Further, the combustion gas diffuses while spreading in the downwardly widening tapered hole shape of the injection port 3, so that the flow velocity thereof rapidly decreases.

Therefore, in the front portion of the main chamber, it becomes difficult for the combustion gas to reach, and the air utilization rate becomes low.

The maximum torque and maximum output are reduced by the lower air utilization rate.

The subject of this invention is in the following points.

(A) Increase the air utilization rate in all parts of the central part of the main room, the front part of the main room and the rear part of the main room.

(B) Prevent incomplete combustion from occurring in all parts of the central part of the main chamber, the front part of the main chamber and the rear part of the main chamber.

[Means for Solving the Problems]

The present invention is characterized in that the basic structure is configured as follows, for example, as shown in FIGS. 1 to 4, in order to solve the above problems.

That is, the ejection groove 12 is formed so as to be cut rearward from the rear surface 3a of the inner peripheral surface of the injection port 3, and the ejection groove 12 is penetrated across the bottom surface of the swirl chamber 1 and the ceiling surface of the main combustion chamber 2, As the groove rear side edge 12a of the jet groove 12 approaches the groove lower end portion 12c on the main combustion chamber 2 side from the groove upper end portion 12b on the swirl chamber 1 side, the size of receding from the rear surface 3a of the injection port 3 gradually increases. The lateral width T of the ejection groove 12 is set to a value smaller than the lateral width S of the nozzle hole 3.

[Work]

 The present invention operates as follows.

(A) The air utilization rate increases in all parts of the central part of the main chamber, the front part of the main chamber, and the rear part of the main chamber. During the explosive expansion action, the combustion gas that begins to combust and expand in the swirl chamber 1 is A large flow of the main flow is guided obliquely forward and downward by the injection port 3, and a small flow of the branch flow is guided backward and downward by the ejection groove 12 above the main flow.

The former large flow main flow passes through the central portion of the main chamber in the main combustion chamber 2 and flows into the front portion of the main chamber at a high speed, and a large amount of air and excess / deficiency in the central portion of the main chamber and the front portion of the main chamber. However, since the air is mixed in an appropriate ratio, the utilization rate of air in the central portion of the main chamber and the front portion of the main chamber is high.

The latter small branch flow flows into the rear part of the small volume main chamber located from the left and right sides to the rear side of the opening position of the injection port 3 in the main combustion chamber 2, and inside the rear part of the main chamber. Since the air is mixed with an appropriate ratio without excess or deficiency, the utilization rate of air in the rear portion of the main chamber is high.

As a result, the air utilization rate is increased in all of the central portion of the main combustion chamber 2, the front portion of the main chamber, and the rear portion of the main chamber.

(B) In the high-load operation where incomplete combustion does not occur in all parts of the main chamber center part, main chamber front part, and main chamber rear part, in the main combustion chamber 2, the main chamber rear part Due to the higher air utilization rate, it is possible to prevent fuel enrichment in the central part of the main chamber or the front part of the main chamber.
Moreover, of the combustion gas that has begun to burn in the swirl chamber 1, only a small amount of branch flow flows into the rear part of the main chamber, so a large amount of main flow flows into the central part and the front part of the main chamber. , Its flow velocity becomes sufficiently fast, it goes well into the depths and mixes well with air. Therefore, incomplete combustion hardly occurs in the central portion of the main chamber and the front portion of the main chamber.

Further, in the rear portion of the main chamber, only a small branch flow of the combustion gas flows into the portion corresponding to the small volume, so that the fuel does not become rich and incomplete combustion does not occur.

As a result, incomplete combustion does not occur in all of the central portion of the main chamber, the front portion of the main chamber, and the rear portion of the main chamber.

〔The invention's effect〕

Since the present invention is configured and operates as described above,
It has the following effects.

(A) Within a large volume over the central part of the main combustion chamber 2 and the front part of the main chamber where the air utilization rate is high, in all parts of the central part of the main chamber, the front part of the main chamber, and the rear part of the main chamber In, from the nozzle 3 with a wide passage cross-sectional area,
Since a large flow rate of the main flow of the combustion gas in the swirl chamber 1 flows in at a high speed, the utilization rate of air is high.

Moreover, in the narrow volume of the rear side portion of the main chamber, a small flow amount of the combustion gas is branched from the ejection groove 12 having a narrow passage cross-sectional area, so that the utilization rate of air is high.

As a result, the air utilization rate is high in all of the central portion of the main chamber, the front portion of the main chamber, and the rear portion of the main chamber.

The maximum torque and maximum output can be increased due to the higher air utilization rate.

(B) Incomplete combustion does not occur in all parts of the central part of the main chamber, the front part of the main chamber, and the rear part of the main chamber. Since only a small branch flow of the combustion gas flows from the groove 12, there is no fuel enrichment,
Incomplete combustion does not occur.

Further, the amount of the branch flow of the combustion gas that flows into the rear portion of the main chamber does not flow into the central portion of the main chamber and the front portion of the main chamber. For this reason, in the central portion of the main chamber and the front portion of the main chamber, the fuel concentration does not become excessive and incomplete combustion does not occur.

As a result, incomplete combustion does not occur in all parts of the central part of the main chamber, the front part of the main chamber, and the rear part of the main chamber.

As much as this incomplete combustion does not occur, the fuel consumption rate is reduced and the amount of unburned harmful components such as C, CO, and HC in the exhaust gas is reduced.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a right side view in vertical section around a swirl chamber of a diesel engine, FIG. 2 is a schematic perspective view showing the same area, FIG. 3 is a right side view in vertical section of a main part of a diesel engine, and FIG. 4 is FIG. 4 is a sectional view taken along line IV-IV in FIG. 4, in which the diesel engine E has a cylinder 8 formed at the center of the cylinder block 7,
The piston 10 is fitted in the cylinder 8 so as to be vertically slidable.

The cylinder head 11 is assembled above the cylinder block 7, and the fuel injection space 19 is bored at the end facing the cylinder block 7 in the left half of the cylinder head 11, and the fuel injection space 19 is halved from the lower opening edge. The injection chamber member 20 is fitted to form the swirl chamber 1 by the upper hemisphere portion of the fuel injection space 19 and the lower hemisphere portion of the injection chamber member 20.

A nozzle fitting insertion hole 21 is provided so as to extend from the upper end of the left half of the cylinder head 11 to the fuel injection space 19, and a fuel injection nozzle 22 is fitted into this fitting insertion hole 21 so that the tip end injection port portion 23 is located at the swirl chamber 1. To face.

The injection port 3 is provided in the injection chamber member 20 in a rearward upward slope shape, that is,
The auxiliary combustion port 15 is formed at both left and right ends of the injection port 3 so that the main combustion chamber is composed of the upper half of the cylinder 8 through the injection port 3 and the auxiliary injection port 15. The swirl chamber 1 is communicated with 2.

That is, the passage cross section of the injection port 3 is formed in a long hole shape, and
The axis of the nozzle 3 and the axis of the auxiliary nozzle 15 are set to intersect at one focusing point.

Accordingly, the air on the main combustion chamber 2 side smoothly flows into the swirl chamber 1 during the compression stroke, and the main combustion chamber 2 flows during the combustion stroke.
The flame spread over can be averaged.

The ejection groove 12 is formed by cutting backward from the rear surface 3a of the inner peripheral surface of the injection port 3
To form.

The jet groove 12 penetrates the bottom surface of the swirl chamber 1 and the ceiling surface of the main combustion chamber 2.

The groove rear side edge 12a of the jet groove 12 is the groove upper end portion 1 on the swirl chamber 1 side.
2b from the lower end 12c of the groove on the main combustion chamber 2 side, the injection port 3
The rear surface 3a is formed so that the size of the rear surface is gradually increased.

The lateral width T of the ejection groove 12 is set to a value smaller than the lateral width S of the ejection port 3.

The ejection groove 12 is formed in a V-groove shape in a plan view as shown in FIG. 4 and a right-angled triangular shape in a side view as shown in FIG.

Thus, during the combustion stroke, the flame propagation is smoothly transmitted to the rear side of the injection port 3 in the main fuel chamber 2 in the inclination direction P (that is, the Q direction portion), and the combustion delay in this portion can be eliminated.

On the other hand, a nozzle orifice projection 5 is provided at a position corresponding to the nozzle hole 3 of the piston head 4, and the projection 5 causes the nozzle head 3, the auxiliary nozzle hole 15, and the ejection groove 12 in the process before and after the piston head 4 reaches the top dead center 6. Configured to rush into.

That is, the injection port throttle projection 5 has a base having a trapezoidal cross-section square prism shape, a conical bulge 16 at each of the front left and right ends, and a thin chevron cross-section at the center of the rear part. The wing protrusions 17 of each of the ridges 1 are connected to each other, the base portion of the bulge portion 16 to the auxiliary jet nozzle 3 and the wing protrusion 17 of the blast portion 1
Try to rush into 2.

In this case, the gap between the nozzle orifice projection 5 and the nozzle 3, the auxiliary nozzle 15, and the ejection groove 12 is set to be substantially equal to the top clearance C.

When the above-mentioned nozzle orifice projection 5 is formed on the piston head 4, the change in the passage cross-sectional area A of the nozzle hole 3 with respect to the change in the crank angle θ shows that the piston head 4 moves from the top dead center 6 as shown in FIG. The passage cross-sectional area A is secured for both engines having different cylinder diameters while they are separated, but the passage cross-sectional area A rapidly decreases before and after the piston head 4 reaches the top dead center 6.

Therefore, looking at the change in the air flow velocity V of the nozzle 3 with respect to the change in the crank angle θ, as shown in FIG. 6, when the piston head 4 approaches the top dead center 6, the air flow velocity V increases and becomes approximately −.
Although it reaches a peak at 20 degrees and then decays like a virtual line in the prior art, in the present invention, the second stage is again performed immediately before reaching 0 degrees (that is, immediately before the piston head 4 reaches the top dead center 6). It reaches the peak of the eye and maximizes the air flow velocity V.

As a result, a large passage cross-sectional area A is secured while the piston head 4 is away from the top dead center 6, so that the main combustion chamber 2
The air smoothly flows into the swirl chamber 1 to increase the compression ratio. Therefore, the starting performance can be improved.

On the contrary, before and after the piston head 4 reaches the top dead center 6, since the passage cross-sectional area A is narrowed down by the projection 5, the inflow velocity of air is increased to increase the air utilization rate and the combustion gas is ejected to the main combustion chamber 2. Increase the flow velocity to increase the flame propagation speed.

Moreover, when the combustion gas exits the main combustion chamber 2, the protrusion 5
Is separated from the injection port 3, the ejection passage is enlarged and frictional resistance is reduced to reduce pressure loss. Therefore, the combustion efficiency can be improved as a whole.

In particular, in the present embodiment, since the ejection groove 12 is formed on the side opposite to the inclination direction of the ejection port 3 and the wing protrusion 17 is provided at a position opposed to the ejection groove 12 of the piston head 4, so to speak, The communication passage between the swirl chamber 1 and the main combustion chamber 2 is expanded,
The starting performance can be maintained at a high level, and the passage cross-sectional area can be narrowed to the side opposite to the direction of the injection port inclination of the main combustion chamber 2 to increase the flame propagation speed and to reliably eliminate the combustion delay and improve the combustion efficiency.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is a right side view in vertical section around a swirl chamber of a diesel engine, FIG. 2 is a schematic explanatory perspective view showing the same, and FIG. 3 is diesel. A right side view of a longitudinal section of an essential part of the engine, and FIG. 4 is an IV in FIG.
FIG. 5 is a cross-sectional view taken along the line IV, FIG. 5 is a relationship diagram between the crank angle and the passage cross-sectional area of the nozzle, and FIG. 6 is a relationship diagram between the crank angle and the air flow velocity at the nozzle. FIG. 7 is a longitudinal right side view around the swirl chamber showing the prior art, and FIG. 8 is a vertical right side view around the swirl chamber showing the prior application. 1 ... Vortex chamber, 2 ... Main combustion chamber, 3 ... Injection port, 3a ... Rear surface, 4 ... Piston head, 5 ... Injection port throttle protrusion, 6 ...
… Top dead center, 12… Jet groove, 12a… Rear edge of groove, 12b…
Groove top, 12c ... Groove bottom, A ... total passage cross-section of 3 and 12, B ... 5 cross-section, E ... Diesel engine, S ... 3 width, T ... 12 Width.

Claims (2)

[Claims] 1. A swirl chamber (1) is provided in a rearward portion of a main combustion chamber (2) of a diesel engine (E), and a jet port (3) having an upward slanted rearward direction.
In a swirl chamber type combustion chamber of a diesel engine that is communicated via a jet nozzle, a jet groove (12) is formed so as to cut backward from the rear surface (3a) of the inner peripheral surface of the jet nozzle (3). 12) penetrates the bottom surface of the swirl chamber (1) and the ceiling surface of the main combustion chamber (2), and the groove rear side edge (12a) of this ejection groove (12) is located on the swirl chamber (1) side. The ejection groove is formed so that the size of the recess retreating from the rear surface (3a) of the injection port (3) gradually increases as the groove upper end (12b) approaches the groove lower end (12c) on the main combustion chamber (2) side. The swirl chamber combustion chamber of a diesel engine, characterized in that the width (T) of (12) is set to a value smaller than the width (S) of the nozzle (3). 2. A nozzle head projection (5) is provided on the piston head (4),
The stroke before and after the piston head (4) reaches the top dead center (6) by projecting toward the nozzle (3) and the nozzle (12) at the position corresponding to the nozzle (3) and the nozzle (12). so,
The jet orifice projection (5) enters the jet port (3) and the jet groove (12),
The total passage sectional area (A) of the nozzle (3) and the ejection groove (12) is configured to be narrowed by the value of the sectional area (B) of the nozzle throttle protrusion (5). A swirl chamber combustion chamber for a diesel engine according to item 1.