Direct injection internal combustion engine piston combustion chamber

Abstract

The present invention discloses a direct injection internal combustion engine piston combustion chamber, including an upper extension of an inverted cone surface connected with a piston top surface; an upper portion of a first step side straight line segment transitioning with a lower arc of a side generatrix of the inverted cone surface; an upper portion of a first step bottom arc smoothly connected with a lower portion of a first step side straight line segment; a lower portion of a raised straight line segment smoothly connected with a first step bottom arc; an upper portion of a raised bottom arc smoothly connected with an upper portion of a raised straight line segment through a raised top arc; an upper portion of a necked opening smoothly transitioning with a lower portion of a raised bottom arc, and a lower portion thereof smoothly transitioning with a combustion chamber bottom arc; an arc at the root of a central boss smoothly transitioning with a combustion chamber bottom arc; wherein the raised straight line segment, the raised top arc, and the raised bottom arc constitute a guide protrusion. The direct injection internal combustion engine piston combustion chamber of the present invention can reduce the generation of soot, and effectively inhibit soot from entering the engine oil of a cylinder wall to protect the cylinder wall.

Description

Technical Field

[0001] The invention relates to the technical field of internal combustion engines, in particular to a direct injection internal combustion engine piston combustion chamber with a circumferential flow guide protrusion. Background Art

[0002] A direct injection internal combustion engine injects fuel directly into the cylinder, and then organizes the fuel vapor to mix with air and burn to do work under the guidance of spray and combustion chamber. It can be seen that the combustion chamber is a key design feature of the internal combustion engine combustion system. The matching of the combustion chamber design features and the spray will directly affect the combustion performance and pollutant emission level of the internal combustion engine. A direct injection diesel engine is a typical direct injection internal combustion engine. Emission regulations require that the pollutant emission limits and fuel consumption rates of direct injection diesel engines for vehicles continue to decrease. For example, in July 2021, strict national VI a emission regulations will be implemented nationwide for diesel-powered vehicles. Compared with the national V emission limits, the national VI has a 72% reduction in unburned hydrocarbons (HC), an 80% reduction in nitrogen oxides (NOx) emissions, and a 50% reduction in soot particles (PM) emissions; for another example, the third stage fuel consumption regulations for heavy-duty diesel vehicles implemented in 2019 have been reduced by 15% compared to the second stage. Therefore, the combustion system of direct injection internal combustion engines, especially the combustion chamber, needs to be continuously improved.

[0003] At present, a typical direct injection diesel engine combustion chamber shape is the ω shape and its deformation shape, such as Figure 1a-1c As shown in the figure, it shows three typical ω-shaped combustion chambers with step characteristics, where Da is called the combustion chamber diameter, Di is called the combustion chamber necking diameter, Tm is called the distance from the transition arc center to the piston top surface, and T is called the combustion chamber depth. When Da>Di, it is called a necking type combustion chamber, when Da=Di, it is called a straight type combustion chamber, and when Da<Di, it is called an open type combustion chamber.

[0004] Below Figure 2 Take the characteristics of the ω-shaped combustion chamber with step features as an example: a boss 15 is provided in the center of the combustion chamber, and the boss 15 can be a single truncated cone or a plurality of truncated cones stacked together, and the top surface of the boss can be a plane or a spherical surface. When the combustion chamber reaches the maximum diameter, the diameter of the combustion chamber gradually decreases to the minimum value when extending toward the piston top surface, so that a constriction is formed in the combustion chamber, and the diameter of the combustion chamber increases again when extending from the constriction to the piston top surface, and the upper combustion chamber space 5 is formed in a step shape, and the side surface 4 of the step has a smooth arc transition with the piston top surface.

[0005] The ω-shaped combustion chamber with step characteristics cooperates with the intake vortex to make full use of the lower space 13 formed above the bottom arc 14 in the combustion chamber, the space 5 on the step, and the air above the top surface of the piston, so as to improve the oil-gas mixing quality in the cylinder, improve the combustion efficiency and reduce the carbon soot emission. However, this type of combustion chamber still has the phenomenon of excessively rich mixed gas in some areas during the main combustion period, which causes a large amount of carbon soot to be generated during the combustion process. Although most of the carbon soot will be oxidized in the post-combustion stage, the carbon soot emission may still be too high, and even carbon soot may enter the engine oil on the cylinder wall and deteriorate the engine oil. Therefore, this type of combustion chamber needs to be continuously improved in design to improve the air utilization rate, improve the thermal efficiency during the main combustion period, and reduce the amount of carbon soot generated during the main combustion period.

[0006] The ω-shaped combustion chamber with step characteristics in the prior art has the following defects: Figure 2 As shown, the existing ω-shaped combustion chamber with step features has low air utilization rate for a part of the space, which is the space 18 between the constriction and the center line of the combustion chamber. Because the step bottom plane 6 tangent to the arc surface of the constriction directly guides the fuel vapor to the step side 4 and the piston top surface 2, the fuel vapor cannot move to the space 18, thereby limiting the improvement of thermal efficiency.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0008] The object of the present invention is to provide a direct injection internal combustion engine piston combustion chamber, which is designed with a guide protrusion on the step of the ω-shaped combustion chamber. After the fuel vapor moves to the side wall of the combustion chamber, it hits the wall and is diverted. A part of the fuel vapor moves along the side wall of the lower space of the combustion chamber to the bottom of the combustion chamber, and the other part of the fuel vapor enters the upper space of the combustion chamber step through the transition arc (narrowing) between the combustion side wall and the bottom surface of the step. The air utilization between the guide protrusion and the center line of the combustion chamber can be effectively improved, thereby reducing the generation of carbon soot and effectively inhibiting the carbon soot from entering the engine oil of the cylinder wall to protect the cylinder wall.

[0009] To achieve the above-mentioned purpose, the present invention provides a direct injection internal combustion engine piston combustion chamber, which is located at the upper part of the piston body and includes an inverted cone surface, a first step side straight line segment, a first step bottom circular arc, a convex straight line segment, a convex bottom circular arc, a necking and a center boss. The upper part of the inverted cone surface extends and connects with the piston top surface; the upper part of the first step side straight line segment transitions with the lower circular arc of the side generatrix of the inverted cone surface; the upper part of the first step bottom circular arc smoothly connects with the lower part of the first step side straight line segment; the lower part of the convex straight line segment smoothly connects with the first step bottom circular arc; the upper part of the convex bottom circular arc smoothly connects with the upper part of the convex straight line segment through the convex top circular arc; the upper part of the necking smoothly transitions with the lower part of the convex bottom circular arc, and its lower part smoothly transitions with the combustion chamber bottom circular arc; the arc at the root of the center boss smoothly transitions with the combustion chamber bottom circular arc; wherein the convex straight line segment, the convex top circular arc and the convex bottom circular arc constitute a flow guide protrusion.

[0010] In a preferred embodiment, the direct injection internal combustion engine piston combustion chamber further comprises a first step bottom surface straight line segment, and the raised straight line segment and the first step bottom arc are smoothly connected via the first step bottom surface straight line segment.

[0011] In a preferred embodiment, the raised straight line segment and the raised bottom arc are transitionally connected via the raised top plane.

[0012] In a preferred embodiment, the straight line segment of the projection and the arc of the bottom of the projection are connected by a transition of the inclined surface of the top of the projection.

[0013] In a preferred embodiment, the angle between the inner tangent line of the protrusion top arc and the protrusion bottom arc and the piston top surface is between 60° and 90°.

[0014] In a preferred embodiment, the angle between the raised straight line segment and the top surface of the piston is less than or equal to 25°.

[0015] In a preferred embodiment, the centerline of the combustion chamber coincides with the centerline of the piston body.

[0016] In a preferred embodiment, the centerline of the combustion chamber and the centerline of the piston body do not coincide.

[0017] In a preferred embodiment, the combustion chamber diameter is greater than, equal to or smaller than the necking diameter.

[0018] In a preferred embodiment, the ratio of the depth from the center of the necking to the piston top surface to the combustion chamber is between 0.35 and 0.47.

[0019] Compared with the prior art, the direct injection internal combustion engine piston combustion chamber of the present invention is designed with a guide protrusion on the step of the ω-shaped combustion chamber with step characteristics. After the fuel vapor moves to the side wall of the combustion chamber, it hits the wall and splits. A part of the fuel vapor moves along the side wall of the lower space of the combustion chamber to the bottom of the combustion chamber, and the other part of the fuel vapor enters the upper space of the combustion chamber step through the transition arc (recessed opening) between the combustion side wall and the bottom surface of the step. The fuel vapor entering the step first climbs upward along the bottom arc and top arc of the guide protrusion, and rushes to the bottom surface of the cylinder head at a certain angle α under the guidance of the guide protrusion. Then, the fuel vapor moves and diffuses to both sides of the bottom surface of the cylinder, and a part of it moves to the raised guide space between the guide protrusion and the combustion center line, and the other part moves to the upper space of the first step and the raised guide space above the piston top surface. In this way, on the one hand, the utilization of air between the guide protrusion and the center line of the combustion chamber can be effectively improved, thereby improving thermal efficiency. On the other hand, the quality of the mixture in the space above the top surface of the piston can be improved, the generation of carbon soot can be reduced, and the engine oil that contains carbon soot that enters the cylinder wall can be effectively inhibited to protect the cylinder wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1a-Figure 1c It is a schematic diagram of the combustion chamber type of the ω-type direct injection diesel engine;

[0021] Figure 2 It is a schematic diagram of the structure of the combustion chamber of an ω-type direct injection diesel engine;

[0022] Figure 3 is a schematic cross-sectional view of the structure of a piston combustion chamber according to an embodiment of the present invention;

[0023] Figure 4 is a partial enlarged view of a flow-guiding protrusion according to an embodiment of the present invention;

[0024] Figure 5 is a dimension definition diagram of a piston combustion chamber according to an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of spray motion in a piston combustion chamber according to an embodiment of the present invention.

[0026] Description of main reference numerals:

[0027] 1-piston body, 2-piston top surface, 3-inverted cone surface, 4-first step side straight line segment, 5-first step bottom arc, 6-first step bottom straight line segment, 7-first step upper space, 8-raised straight line segment, 9-flow guide protrusion, 10-raised top arc, 11-raised bottom arc, 12-neck, 13-combustion chamber lower space, 14-combustion chamber bottom arc, 15-center boss, 16-combustion chamber centerline, 17-piston pin hole, 18-raised flow guide space, 19-cylinder head bottom surface, Da-combustion chamber diameter, Di-neck diameter. DETAILED DESCRIPTION

[0028] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0029] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0030] In this specification, the same reference numerals in the drawings represent the same features. The directional terms "upper" and "upper side" in the present invention refer to the direction from the piston pin hole to the piston top surface. The terms "lower" and "lower side" refer to the direction from the piston top surface to the piston pin hole. The term "inner" refers to the side close to the center line of the combustion chamber, and the term "outer" refers to the side away from the center line of the combustion chamber.

[0031] See also Figure 3 and Figure 4According to a preferred embodiment of the present invention, a direct injection internal combustion engine piston combustion chamber is located at the upper part of the piston body 1, and includes an inverted cone surface 3, a first step side straight line segment 4, a first step bottom arc 5, a first step bottom straight line segment 6, a convex straight line segment 8, a convex top arc 10, a convex bottom arc 11, a constriction 12 and a central boss 15. The upper part of the inverted cone surface 3 extends and connects with the piston top surface 2. The upper part of the first step side straight line segment 4 transitions with the lower arc of the side generatrix of the inverted cone surface 3. The upper part of the first step bottom arc 5 smoothly connects with the lower part of the first step side straight line segment 4. The convex straight line segment 8 and the first step bottom arc 5 are smoothly connected through the first step bottom straight line segment 6, that is, the lower end of the first step bottom arc 5 is smoothly connected with one end of the first step bottom straight line segment 6, and the other end of the first step bottom straight line segment 6 can be smoothly connected with the lower end of the convex straight line segment 8 through a transition arc. The upper part of the raised bottom arc 11 is smoothly connected to the upper part of the raised straight line segment 8 through the raised top arc 10. The upper part of the constriction 12 is smoothly transitioned to the lower part of the raised bottom arc 11, and its lower part is smoothly transitioned to the combustion chamber bottom arc 14. The arc at the root of the central boss 15 is smoothly transitioned to the combustion chamber bottom arc 14. The raised straight line segment 8, the raised top arc 10 and the raised bottom arc 11 constitute the guide protrusion 9.

[0032] See also Figure 3In some embodiments, the combustion chamber of the piston of the direct injection internal combustion engine of the present invention is located at the upper part of the piston body 1 and above the piston pin hole 17. The center line 16 of the combustion chamber may coincide with the center line of the piston body 1, or may be offset by a certain distance relative to the center line of the piston body 1. The center of the combustion chamber of the piston of the direct injection internal combustion engine of the present invention is a center boss 15. The lower side of the center boss 15 has an arc that smoothly transitions to the inner end of the arc 14 at the bottom of the combustion chamber. The outer side of the arc 14 at the bottom of the combustion chamber constitutes a part of the side wall of the lower space 13 of the combustion chamber. For the constricted 12 type combustion chamber, the outer end of the arc 14 at the bottom of the combustion chamber is smoothly connected to the arc of the constricted 12 through a straight line segment. If it is a straight or open combustion chamber, there is no constriction 12, and the outer end of the arc 14 at the bottom of the combustion chamber will directly connect with the raised bottom arc 11 through an arc. Above the constriction 12, the combustion chamber has the characteristics of double steps, and a guide protrusion 9 is designed at the bottom of the first step, and the lower side of the guide protrusion 9 is a raised bottom arc 11 that smoothly connects with the constriction 12. The top of the guide protrusion 9 of this embodiment is designed to be in an arc shape, that is, the raised top arc 10 of the guide protrusion 9. In some embodiments, the top of the guide protrusion 9 can also be designed as a raised top plane or a raised top inclined surface. In addition, in some embodiments, the raised bottom arc 11 and the raised top arc 10 of the guide protrusion 9 can be smoothly connected with a straight line segment. The upper side of the guide protrusion 9 is a raised straight line segment 8, and the raised straight line segment 8 smoothly transitions with the first step bottom straight line segment 6 through the arc. The first step bottom straight line segment 6 and the first step side straight line segment 4 are smoothly connected through the first step bottom arc 5. In some embodiments, the raised straight line segment 8 can be directly connected with the first step side straight line segment 4 directly through the first step bottom arc 5. There is no feature of the first step bottom straight line segment 6. The generatrix of the straight line segment 4 on the side surface of the first step and the inverted conical surface 3 (the second step) is transitioned through an arc, and the inverted conical surface 3 of the second step extends to the top surface 2 of the piston.

[0033] See also Figure 4 , the angle between the inner common tangent of the raised bottom arc 11 and the raised top arc 10 and the piston top surface 2 is α, 60<α<90°. In some embodiments, if there is a straight line segment smoothly connecting the raised bottom arc 11 and the raised top arc 10, then the straight line segment is the inner common tangent of the raised bottom arc 11 and the raised top arc 10. The angle between the raised straight line segment 8 and the piston top surface 2 is β, β≤25°. In addition, the top of the raised top arc 10 is higher than the smooth connection between the lower end of the raised straight line segment 8 and the straight line segment 6 of the bottom surface of the first step.

[0034] See also Figure 5, the combustion chamber diameter of this embodiment is Da, the diameter of the necking is Di, and the distance from the center of the necking arc 12 to the piston top surface 2 is Tm. For the straight-mouth and open-mouth combustion chambers shown in FIG1 , the necking arc 12 in the original necking 12 type combustion chamber should be called the transition arc between the combustion chamber bottom side wall and the step, and the distance from the center of the transition arc to the piston top surface 2 is Tm. The combustion chamber depth is defined as T, then 0.35≤Tm / T≤0.47.

[0035] According to the position and shape deformation of the combustion chamber step, and the fact that the ω-shaped combustion chamber can be a tapered type (i.e., with a tapered mouth) or a straight mouth or an open mouth, the guide protrusion of the present invention can be implemented in a variety of ways and should not be understood as being limited to the embodiments described above.

[0036] See also Figure 6 The working principle of the direct injection internal combustion engine piston combustion chamber of the present invention is as follows:

[0037] The combustion chamber is located below the piston top surface 2 of the internal combustion engine, is recessed into the piston body 1, and is located above the piston pin hole 17. A typical example is for a four-stroke internal combustion engine, but it is not limited to a four-stroke, and can also be used for internal combustion engines with other stroke numbers. The piston containing the combustion chamber of the present invention is assembled in the cylinder of the internal combustion engine, and an injector is installed on the cylinder head. The center line of the injector can coincide with the center line 16 of the combustion chamber, or it can be offset from the center of the combustion chamber. Taking the working process of a four-stroke internal combustion engine as an example, at the end of the compression stroke, the piston approaches the top dead center, and the injector receives the control signal of the engine controller, opens the injector, and sprays liquid fuel into the combustion chamber. Figure 6 As shown by the arrow, after the liquid fuel is sprayed out of the spray hole, it develops toward the wall of the combustion chamber and is accompanied by the liquid fuel breaking and atomizing, forming fuel vapor in and around the front of the liquid spray, and the fuel vapor has the momentum to move toward the wall of the combustion chamber. After the fuel vapor moves to the side wall of the combustion chamber, it hits the wall and splits. A part of the fuel vapor moves along the side wall of the lower space of the combustion chamber to the bottom of the combustion chamber, and the other part of the fuel vapor enters the upper space of the combustion chamber step through the transition arc (recess 12) between the combustion side wall and the bottom surface of the step. The fuel vapor entering the step first climbs upward along the bottom arc and the top arc of the guide protrusion 9, and under the guidance of the guide protrusion 9, it rushes to the bottom surface 19 of the cylinder head at a certain angle α. Then, the fuel vapor moves and diffuses to both sides of the bottom surface of the cylinder, a part of it moves to the raised guide space between above the guide protrusion 9 and the combustion center line, and the other part moves to the upper space 7 of the first step and the raised guide space above the piston top surface 2. Please refer again. Figure 3The portion from the inner common tangent line of the bottom circular arc 11 and the top circular arc 10 to the combustion chamber centerline 16 is defined as the convex flow guiding space, and the portion outside the inner common tangent line of the bottom circular arc 11 and the top circular arc 10 is defined as the upper space of the first step. This can ultimately improve the quality of the mixed gas in the upper space of the combustion chamber and increase the air utilization rate.

[0038] In summary, the direct injection internal combustion engine piston combustion chamber of the present invention is designed with a guide protrusion on the step of the ω-shaped combustion chamber with step characteristics. After the fuel vapor moves to the side wall of the combustion chamber, it hits the wall and splits. A part of the fuel vapor moves along the side wall of the lower space of the combustion chamber to the bottom of the combustion chamber, and the other part of the fuel vapor enters the upper space of the combustion chamber step through the transition arc (narrowing) between the combustion side wall and the bottom surface of the step. The fuel vapor entering the step first climbs upward along the bottom arc and the top arc of the guide protrusion, and rushes to the bottom surface of the cylinder head at a certain angle α under the guidance of the guide protrusion. Then, the fuel vapor moves and diffuses to both sides of the bottom surface of the cylinder, a part of it moves to the raised guide space between the guide protrusion and the combustion center line, and the other part moves to the upper space of the first step and the raised guide space above the piston top surface. In this way, on the one hand, the air utilization between the guide protrusion and the center line of the combustion chamber can be effectively improved, thereby improving thermal efficiency. On the other hand, the quality of the mixed gas in the space above the top surface of the piston can be improved, the generation of carbon soot can be reduced, and the carbon soot can be effectively inhibited from entering the cylinder wall of the engine oil to protect the cylinder wall.

[0039] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A direct injection internal combustion engine piston combustion chamber, located at the upper part of the piston body, characterized in that: include: An inverted conical surface, the upper portion of which extends to engage with the top surface of the piston; The first step side straight line segment, the upper portion of which transitions to the lower arc portion of the side generatrix of the inverted cone surface; The first step bottom arc has an upper portion smoothly connected to the lower portion of the straight line segment on the side surface of the first step; A raised straight line segment, the lower part of which is smoothly connected to the arc at the bottom of the first step; The upper part of the raised bottom circular arc is smoothly connected with the upper part of the raised straight line segment through the raised top inclined surface; The necking has an upper portion which smoothly transitions to the lower portion of the arc at the bottom of the protrusion, and a lower portion which smoothly transitions to the arc at the bottom of the combustion chamber; The arc at the root of the central boss smoothly transitions to the arc at the bottom of the combustion chamber; as well as Wherein, the convex straight line segment, the convex top inclined surface and the convex bottom arc constitute the diversion convexity; The first step bottom surface straight line segment, the raised straight line segment and the first step bottom arc are smoothly connected through the first step bottom surface straight line segment.

2. The direct injection internal combustion engine piston combustion chamber according to claim 1, characterized in that: The raised straight line segment and the raised bottom arc are transitionally connected through the raised top inclined surface.

3. The direct injection internal combustion engine piston combustion chamber according to claim 1, characterized in that: The angle between the raised straight line segment and the top surface of the piston is less than or equal to 25°.

4. The direct injection internal combustion engine piston combustion chamber according to claim 1, characterized in that: The center line of the combustion chamber coincides with the center line of the piston body.

5. The direct injection internal combustion engine piston combustion chamber according to claim 1, characterized in that: The center line of the combustion chamber and the center line of the piston body do not coincide.

6. The direct injection internal combustion engine piston combustion chamber according to claim 1, characterized in that: The ratio of the center of the necking to the top surface of the piston and the depth of the combustion chamber is between 0.35 and 0.47.

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