JPH0511297Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a whirlpool combustion chamber for a diesel engine.

<Prerequisite structure> The swirl chamber type combustion chamber of the diesel engine of the present invention is intended for those having the following prerequisite structure, as shown in Fig. 3, Fig. 8, Fig. 11, or Fig. 12, for example. .

That is, the main combustion chamber 1 of the diesel engine E
The vortex chamber 3 is communicated with the eccentric point of the
The axis 4 of the nozzle 2 is oriented in an inclined manner so that the closer it gets from the whirlpool chamber 3 to the main combustion chamber 1, the closer it gets to the center of the main combustion chamber 1. It is assumed that the left and right sides of the combustion chamber 1 are formed so as to widen left and right with a widening angle toward the main combustion chamber 1.

<Prior Art> In the above-mentioned structure, the shape of the piston head 8 in the prior art is as follows.

◎ Prior Art 1 See Figures 8 and 9 (Japanese Patent Publication No. 57-59410) The piston head 8 is formed flat.

◎ Prior art 2 See Figures 10 and 11 (Japanese Patent Laid-Open Publication No. 52-29513) A recess 7 is formed near the top dead center of the piston 6 to guide the combustion airflow ejected from the nozzle 2 into the main combustion chamber 1. , is formed in the piston head 8, and the starting end 10 of this recess 7 faces the nozzle 2.

The shape of the recess 7 is such that as it progresses from the starting end 10 to the distal end 12, it gradually widens left and right and becomes deeper.

The bottom surface 100 of this recess 7 is formed into a linear downward slope.

◎ Prior art 3 See Figures 12 and 13 (Japanese Patent Application Laid-Open No. 59-91420) A recess 7 is formed near the top dead center of the piston 6 to guide the combustion airflow ejected from the nozzle 2 into the main combustion chamber 1. , is formed in the piston head 8, and the starting end 10 of this recess 7 faces the nozzle 2.

The shape of the recess 7 is a cloverleaf consisting of one parallel groove 201 and a pair of left and right disc-shaped recesses 202, 202.

The parallel groove portion 201 extends straight in parallel from the starting end 10 of the recess 7 toward the tip 12,
The bottom surface 201a has a linear upward slope.

The pair of disc-shaped recesses 202, 202 are arranged symmetrically on the distal end side of the parallel groove 201, and have a shape that suddenly widens left and right from the middle of the parallel groove 201.

<Problems that the idea aims to solve> The above conventional technology has the following problems.

◎ Prior art 1 See Figures 8 and 9 ( _A1 ) Low air utilization rate At the beginning of combustion when the piston 6 is located near the compression top, the flat surface of the piston head 8
It comes close to the lower end opening of the nozzle 2, and the area immediately below the nozzle 2 is largely blocked.

For this reason, the combustion gas that starts burning and expands in the swirl chamber 3 encounters a large ventilation resistance directly below the nozzle 2 and cannot quickly flow into the main combustion chamber 1. The air utilization rate in the main chamber portion 1a on the far front end side becomes low.

This results in lower engine output and higher fuel consumption.

( _B1 ) Ring stay is likely to occur At the early stage of combustion, the combustion gas expanding in the vortex chamber 3 encounters large ventilation resistance directly below the nozzle 2, so the ring stay is likely to occur at the base end near the nozzle 2 in the main combustion chamber 1. Since the fuel is trapped in the side main chamber portion 1b, there is a lack of air and an excess of fuel, and a large amount of carbon is generated.

This large amount of generated carbon easily flows between the sliding surfaces of the piston 6 and the cylinder 15, which are located in the immediate vicinity, and accumulates in the piston ring groove, which tends to cause ring stuck.

( _C1 ) The piston is prone to thermal distortion.The proximal piston head portion of the piston head 8, located directly below the nozzle 2 where combustion gas easily flows, is heated well, while the front end piston, which is far from the nozzle 2, is heated. Since the head part is not heated much, the temperature difference between these two parts is large.
The piston 6 is prone to abnormal thermal distortion.

As a result, the amount of blow-by gas increases abnormally, and the piston 6 is likely to seize into the cylinder 15.

◎ Prior art 2 See Figures 10 and 11 ( _A2 ) Low air utilization rate At the beginning of combustion when the piston 6 is located near the compression top, the flat surface of the piston head 8 and the shallow starting end 10 of the recess 7 It comes close to the lower end opening of the nozzle 2, and the area immediately below the nozzle 2 is largely blocked.

For this reason, the combustion gas expanding in the swirl chamber 3 encounters a large ventilation resistance directly below the nozzle 2.
It cannot flow quickly into the main combustion chamber 1.

Moreover, although a small amount of combustion gas flows into the recess 7, it is blocked by the rising surface of the tip 12 of the recess 7.

As a result, the air utilization rate in the main chamber portion 1a on the front end side far from the jet nozzle 2 in the main combustion chamber 1 becomes low, and the output of the engine becomes low, and the fuel consumption rate becomes high.

( _B2 ) Ring stay is likely to occur. Due to the same effect as mentioned in ( _B1 ) above, combustion gas is trapped in the area directly below the jet nozzle 2 in the main combustion chamber 1, and a large amount of carbon is generated. Because it easily flows between the sliding surfaces of the piston, ring stays are likely to occur.

( _C2 ) The piston is susceptible to thermal distortion. Due to the same effect as in (C1) above, there is a temperature drop between the proximal piston head part directly below the nozzle of the piston head 8 and the front end piston head part far from it. Because of its large size, the piston 6 is prone to thermal distortion and seizure to the cylinder 15.

◎Prior art 3 See Figures 12 and 13 ( _A3 ) Low air utilization rate At the beginning of combustion when the piston 6 is located near the compression top, the combustion gas flowing out from inside the swirl chamber 3 flows through the parallel grooves 201 of the recess 7. Since the air flows from the air into the pair of disc-shaped recesses 202, the utilization rate of air within the recesses 7 is increased, compared to the above-mentioned prior art 1.
and is more advantageous than prior art 2.

However, the combustion gas is
Since the air is obstructed by the rising surface of the tip portion 12 of No. 2, the utilization rate of the air in the front end side main chamber portion 1a on the front side of the tip portion 12 is low.

( _B3 ) Ring stay is likely to occur. Due to the low utilization rate of the air in the main chamber portion 1a on the front end side, the combustion gas in the recess 7 generates a large amount of carbon due to lack of air. Since this large amount of carbon easily flows between the sliding surfaces of the piston, ring stuck is likely to occur.

( _C3 ) The piston is prone to thermal distortion.While the proximal piston head portion of the piston head 8 directly below the nozzle port 2 is heated by combustion gas and reaches a high temperature, the front end portion on the opposite side Since the piston head portion is not heated to a high temperature, the piston 6 is subject to thermal distortion due to the temperature drop, and the cylinder 15 is likely to seize.

The problems of the present invention are as follows.

(b) Increase air utilization rate.

(b) Make it difficult for ring stays to occur.

(c) Make piston less prone to thermal distortion.

<Means for solving the problem> In order to achieve the above-mentioned problem, the present invention adds the following characteristic structure to the above-mentioned premise structure, as shown in, for example, Figures 1 and 2 (or Figures 5, 6, or 7).

That is, near the top dead center of the piston 6,
A recess 7 that guides the combustion airflow ejected from the nozzle 2 in the main combustion chamber 1 is formed in the piston head 8, and the starting end 10 of this recess 7 faces the nozzle 2. As it progresses from the part 10 to the tip part 12, it is formed in an upwardly widening shape that gradually widens left and right and becomes gradually shallower, and it becomes gradually shallower along the length direction A of the bottom surface 100 of the recess 7. Of the upper surface portion 110,
Compared to the tip side surface portion 101 near the tip 12, the rate of change in the depth of the recess 7 is set to a larger value in the starting end side surface portion 102 located next to the starting end 10 side. It is characterized by having been configured.

<Effect> The present invention works as follows.

(A) Flow of combustion gas to the front main chamber portion 1a At the beginning of combustion when the piston 6 is located near the compression top, the deep starting end 10 of the recess 7 opens the lower end opening of the nozzle 2.

Therefore, the combustion gas that starts to burn and expands in the swirl chamber 3 flows smoothly from the nozzle 2 into the deep starting end 10 of the recess 7, spreads along the upward shape of the tip of the recess 7, and moves forward vigorously. It quickly flows into the main chamber portion 1a on the front end side of the recess 7 while being widely diffused.

Thereby, the utilization rate of air within the front end side main chamber portion 1a is sufficiently increased.

(B) Depth of starting end 10 of recess 7 Also, the volume of recess 7 cannot be made very large due to the volume ratio of swirl chamber 3 to the entire combustion chamber, compression ratio, piston top clearance, etc. .

In this way, under conditions where the volume of the recess 7 is limited to a small amount, the surface portion 1 of the recess bottom 100 closer to the tip end
By setting the rate of change in the depth of the recess 7 to a larger value in the starting end side portion 102 than in the case 01, the tip portion 12 of the recess 7 is
As the volume ratio of the recessed portion on the leading end side closer to the starting end portion 10 decreases, the volume ratio of the recessed portion on the starting end side closer to the starting end portion 10 increases.

As a result, considering the small and limited volume of the recess 7, the depth of the starting end 10 can be increased, which increases the degree to which the lower end opening of the nozzle 2 is opened, and the combustion here increases. The gas flow becomes smoother, promoting the flow into the front main chamber portion 1a, and further increasing the air utilization rate in the front main chamber portion 1a.

<Effects of the Invention> The present invention is configured and operates as described above, and thus has the following effects.

(a) Increased air utilization rate At the beginning of combustion when the piston 6 is located near the compression top, the deep starting end 10 of the recess 7 opens the lower end opening of the nozzle 2.

Therefore, the combustion gas that starts burning and expands in the swirl chamber 3 flows smoothly from the nozzle 2 into the deep starting end 10 of the recess 7, spreads out along the upward shape of the tip of the recess 7, and moves forward vigorously. It quickly flows into the main chamber portion 1a on the front end side of the front side of the recess 7 while being widely diffused.

Thereby, the utilization rate of air within the front end side main chamber portion 1a is sufficiently increased.

As the air utilization rate increases, the engine output can be increased and the fuel consumption rate can be reduced.

(b) Ring stay is unlikely to occur In the early stage of combustion, the combustion gas expanding in the swirl chamber 3 is smoothly guided by the recess 7 and quickly flows into the main chamber portion 1a on the front end side while being widely diffused. This front end side main chamber part 1
As the utilization rate of air increases in a, the combustion gas becomes less likely to become insufficient in air or in excess of fuel.
The amount of carbon generated is significantly reduced.

This prevents a large amount of carbon from flowing between the sliding surfaces of the piston, making it difficult for ring stuck to occur.

(c) The piston is less susceptible to thermal distortion. At the early stage of combustion, the combustion gas expanding in the swirl chamber 3 is smoothly guided by the recess 7 and quickly spreads widely to the main chamber portion 1a on the front end side. .

For this reason, the nozzle 2 of the piston head 8
Since the combustion gas is heated in both the proximal piston head portion directly below and the front end head portion far from the nozzle 2, the temperature drop is small and the piston 6 is unlikely to undergo abnormal thermal distortion.

This causes an abnormal increase in the amount of blow-by gas,
In addition, seizure of the piston 6 to the cylinder 15 can be effectively prevented.

(d) Increase in the above effects (a), (b), and (c) The rate of change in the depth of the recess 7 is set to a larger value in the starting end side surface portion 102 than in the surface portion 101 closer to the tip of the recess bottom surface 100. By doing this, the dent 7
The volume ratio of the starting end side recessed part near the starting end 10 increases by the amount that the volume ratio of the distal end side recessed part near the leading end 12 becomes smaller with respect to the total volume of.

As a result, considering the small and limited volume of the recess 7, the depth of the starting end 10 can be increased, which increases the degree to which the lower end opening of the nozzle 2 is opened, and the combustion here increases. The gas flow becomes smoother, promoting the flow into the front main chamber portion 1a, and further increasing the utilization rate of air in the front main chamber portion 1a.

As a result, it is possible to further increase the above-mentioned effects ``(a) Increased air utilization,'' ``(Rolling) less likely to cause ring-stacking,'' and ``(c) Less likely to cause thermal strain in the piston.'' can.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with

Figure 1 is a plan view of the piston head showing the first time, Figure 2 is a vertical right side view of the vicinity of the piston head, Figure 3 is a vertical right side view of the main parts of a vertical diesel engine, and Figure 4 is a schematic of the nozzle. In the figure, a cylinder 15 is formed in the center of a cylinder block 14 of a diesel engine E, and a piston 6 is fitted into the cylinder 15 so as to be vertically slidable.

The cylinder head 16 is assembled above the cylinder block 14, and a fuel injection space 19 is bored in the wall of the rear half of the cylinder head 16 facing the main combustion chamber 1 of the cylinder block 14, and a fuel injection space 19 is formed from the lower opening edge of the cylinder head 16. The half-shaped injection chamber member 20 is fitted to the upper hemisphere of the fuel injection space 19 and the injection chamber member 2.
A whirlpool chamber 3 is formed with the lower hemisphere of 0.

A nozzle insertion hole 21 is provided from the upper end of the rear half of the cylinder head 16 to the fuel injection space 19, and a combustion injection nozzle 22 is inserted into the insertion hole 21, and its tip nozzle 23 is inserted into the swirl chamber 3. Let's face it.

The nozzle 2 of the injection chamber member 20 is oriented in a backward upwardly inclined manner, that is, the axial center 4 of the nozzle 2 is oriented so that the closer it is from the swirl chamber 3 to the main combustion chamber 1, the closer it is to the center of the main combustion chamber 1.

As shown in FIG. 4, the nozzle 2 has a round hole 24 in the center that serves as the main jetting path for the combustion air flow, and side holes 25 extending over both left and right sides 5 slightly forward of the round hole 24.
It is constructed by leaving an open area and forming the border into a mountain shape.

The axes of each of the side passages 25 are inclined with respect to the axis of the round hole 24 so as to expand to the left and right as they go downwards (that is, the passage cross-sectional area of the side passages 25 is adjusted so that the passage cross-sectional area of the side passages 25 is configured to increase horizontally),
The combustion airflow ejected from the nozzle 2 into the main combustion chamber 1 is made to spread to both left and right sides.

Note that the jet nozzle 2 is basically a tapered shape that spreads the combustion air flow from side to side.
The shape of the nozzle port is not particularly specified as long as the cross-sectional shape of the passage is widened laterally as it approaches the main combustion chamber.

On the other hand, the piston head 8 is provided with a fan-shaped recess 7 that opens approximately 60 degrees. (See Figure 1).

The recess 7 is arranged near the center of the piston head 8, and its starting end 10 faces the opening end of the jet nozzle 2 on the main combustion chamber side, so that the combustion air jetted out from the jet nozzle 2 is shaped like a fan from the starting end 10 of the recess. It is configured so that it properly spreads over the entire surface of the tube and smoothly reaches the tip 12 (see FIG. 2).

The shape of the recess 7 in the longitudinal direction is as follows:
The vicinity 102 is formed into a single curved surface with a small radius of curvature, and the portion 101 near the tip 12 is formed into a single curved surface with a large radius of curvature, so that both curved wall surfaces are smoothly continuous.

In this case, among the upward surface portions 110 that gradually become shallower along the length direction A of the bottom surface 100 of the recess 7, the rate of change in the depth of the bottom surface 100 of the recess 7 is It is small and has a gently curved shape. Conversely, in the starting end side portion 102 adjacent to this starting end 10 side,
The rate of change in depth is greater than that near the tip 101, so that it exhibits a curved surface shape with a steep average slope.

Note that the upper surface portion 110 of the bottom surface 100 of the recess 7
As long as the rate of change in the depth of the tip-side surface portion 101 near the tip 12 is smaller than that of the adjacent starting-end side surface portion 102 on the starting-end 10 side, the shape in the longitudinal direction is The present invention is not limited to the above embodiments, and the following cases may also be used.

That is, FIG. 5 shows a second embodiment of the recess 7, in which the part from the starting end 10 to the midway part 103 toward the tip 12 is formed deeply into a flat part, and the part from the midway part 103 to the tip 12 has a predetermined curvature. Single curved surface of radius 104
The average slope of the tip-side portion 102 of this single curved surface 104 is large, and the average slope of the tip-side portion 10 is small.

FIG. 6 shows a third embodiment of the recess 7, with the starting end 1
The wall surface 50 cut down from 0 is α with respect to the vertical plane B.
If the length direction A from the starting end 10 to the tip end 12 is set positive and the opposite direction is set negative, the lower the direction, the more negative the direction from the vertical plane B. It is shaped so that it moves away from the sky.

In this case, the tip portion 12 is cut down from the wall surface 50.
The bottom surface 100 is a single curved surface with a predetermined radius of curvature.

FIG. 7 shows a fourth embodiment of the recess 7, in which the cut-down wall surface 50 is inclined at an angle of β with respect to the vertical plane B, and is formed so that it becomes further away from the vertical plane B in the positive direction as it goes downward. This is what I did.

As described above, the present invention is characterized in that the rate of change in the depth of the recess 7 formed in the piston head is changed, and the bottom surface connecting between the bottom of the cut-down wall surface 50 and the tip 12 is Regarding this, the portion near the tip 12 may be formed into an upwardly projecting convex curved surface or a bent plane.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is a plan view of a piston head showing the first embodiment, Fig. 2 is a vertical right side view of the vicinity of the piston head, and Fig. 3 is a longitudinal sectional view of the main part of a vertical diesel engine. 4 is a schematic diagram of the nozzle, FIG. 5 is a longitudinal sectional right side view of the piston head showing the second embodiment, FIG. 6 is a view corresponding to FIG. 5 showing the third embodiment, and FIG. 5 is a diagram corresponding to FIG. 5 showing the fourth embodiment. FIG. 8 is a vertical left side view of the swirl chamber type combustion chamber according to Prior Art 1, and FIG. 9 is a bottom view of the nozzle in FIG. 8. FIG. 10 is a vertical left side view of a spiral combustion chamber according to Prior Art 2, and FIG. 11 is a plan view of the piston head shown in FIG. 10. 1st
2 is a vertical sectional right side view of a swirl chamber type combustion chamber according to Prior Art 3, and FIG. 13 is a plan view of the piston head of FIG. 12. 1... Main combustion chamber, 2... Nozzle, 3... Whirlpool chamber,
4...Axis of 2, 5...Both left and right sides of 2, 6...
Piston, 7... recess, 8... piston head,
10...starting end of 7, 12...tip end of 7, 10
0...bottom of 7, 101...surface near the tip, 1
02...Starting end side part, 110...Upper face part,
A... Length direction of 7, E... Diesel engine.

Claims (1)

[Claims for Utility Model Registration] A whirlpool chamber 3 is connected to an eccentric location of the main combustion chamber 1 of the diesel engine E through a jet nozzle 2, and the axis 4 of the jet nozzle 2 becomes closer to the main combustion chamber 1 from the whirlpool chamber 3. The left and right side surfaces 5 of the nozzle 2 are oriented in an inclined manner approaching the center of the main combustion chamber 1, and the left and right side surfaces 5 of the nozzle 2 are oriented so that the left and right sides of the combustion air expanding in the swirl chamber 3 are oriented at an angle toward the main combustion chamber 1. In the whirlpool combustion chamber of a diesel engine, which is formed to spread out, a recess 7 is formed in the piston head 8 near the top dead center of the piston 6 to guide the combustion airflow ejected from the nozzle 2 into the main combustion chamber 1. The starting end 10 of this recess 7 faces the nozzle 2, and the shape of the recess 7 is such that as it progresses from the starting end 10 to the tip 12, it gradually widens left and right and becomes gradually shallower. Of the ascending surface portion 110 that is formed in a widening upward shape and gradually becomes shallower along the length direction A of the bottom surface 100 of the recess 7,
Compared to the tip-side surface portion 101 near the tip 12, the rate of change in the depth of the recess 7 is set to a larger value in the starting end side surface portion 102 located adjacent to the starting end 10 side. A swirl chamber type combustion chamber of a diesel engine is characterized by its structure.